CA2225763A1 - Pseudo-plug-flow reactor - Google Patents
Pseudo-plug-flow reactor Download PDFInfo
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- CA2225763A1 CA2225763A1 CA 2225763 CA2225763A CA2225763A1 CA 2225763 A1 CA2225763 A1 CA 2225763A1 CA 2225763 CA2225763 CA 2225763 CA 2225763 A CA2225763 A CA 2225763A CA 2225763 A1 CA2225763 A1 CA 2225763A1
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Abstract
A reactor, in which reactions may take place in a mode similar to that provided by plug-flow reactors. This Pseudo-Plug-Flow reactor has an elongate configuration separated by baffles, which form pools to restrain liquids containing reactants from freely flowing from the back end to the front end of the reactor. The liquids are preferably re-circulated from each pool to predetermined inlets directly above the pool, or in front of and above the pool. Preferably, the liquids are atomized at the predetermined inlets. The reactor may be inclined or it may be substantially horizontal.
Description
CA 0222~763 1997-12-23 PSEUDO-PLUG-FLOW REACTOR
CROSS-REFERENCE TO RELATED APPLICATION
The present application claims priority from U.S. Provisional Application No. 60/033,831 filed December 23, 1996, and from U.S. Non-Provisional Application No. 08/861,210 filed May 21, 1997, which applications are incorporated herein by reference in their entireties.
This invention relates to devices for controlling reactions with special emphasis to oxidations. The reactor of this invention behaves in a manner similar to the manner that a plug-flow reactor behaves.
Plug-flow reactors and processes are well known to the art. They are usually characterized by their ability to allow a mixture of reactants to undergo a reaction as the mixture flows from one end to the other end of the reactor without any substantial back mixing. In order to achieve conditions which allow plug-flow, it is 20 important that the reactants are homogeneous, in either gaseous or liquid state (including dispersions, aerosols, and homogeneous powder or dust containing gases), and preferably in one phase. If all reactants are in the same liquid phase, which flows from one end to the other end of the reactor, back mixing may be avoided more easily than in the case that all reactants are in the gaseous phase, because of molecular 25 mobility reasons.
If one reactant is in a liquid state and the other in gaseous state, it becomes extremely difficult, if not impossible to produce plug-flow conditions with the presently known techniques.
There are many reactions, which require that one reactant is in the liquid 30 state, while the other reactant is in the gaseous state. One example is the case of miscellaneous oxidations, wherein for example a hydrocarbon is oxidized to form an CA 0222~763 1997-12-23 intermediate oxidation product. In such cases, the present art utilizes stirred-tank conditions, which lack completely the advantages of plug-flow conditions. Our recent patents and patent applications on atomization technology, although they provide a great advance in the art of reactions in general, with special emphasis in oxidations, are 5 not characterized by plug-flow conditions.
There is a plethora of references (both patents and literature articles) dealing with the formation of intermediate oxidation products, such as diacids, for example, one of the most important being adipic acid. Adipic acid is used to produce Nylon 66 fibers and resins, polyesters, polyurethanes, and miscellaneous other 1 0 compounds.
There are different processes of manufacturing adipic acid. The conventional process involves a first step of oxidizing cyclohexane with oxygen to a mixture of cyclohexanone and cyclohexanol (KA mixture), and then oxidation of the KA mixture with nitric acid to adipic acid. Other processes include, among others, the 15 "Hydroperoxide Process," the "Boric Acid Process," and the "Direct Synthesis Process," which involves direct oxidation of cyclohexane to adipic acid with oxygen in the presence of solvents, catalysts, and initiators or promoters.
Initiators or promoters are presently being used to shorten considerably an induction period at the beginning of the reaction. Accepted explanations, which 20 have been given regarding the role of the initiators or promoters, involve oxidation of the catalyst, which is usually cobaltous ions to cobaltic ions.
The Direct Synthesis Process has been given attention for a long time.
However, to this date it has found little commercial success. One of the reasons is that although it looks very simple at first glance, it is extremely complex in reality. Due to 25 this complexity, one can find strikingly conflicting results, comments, and views in different references.
It is well known that after a reaction has taken place according to the Direct Synthesis Process, a mixture of two liquid phases is present at ambient temperature, along with a solid phase mainly consisting of adipic acid. The two liquid 30 phases have been called the "Polar Phase" and the "Non-Polar" phase. However, no CA 0222~763 1997-12-23 attention has been paid so far to the importance of the two phases, except for separating the adipic acid from the "Polar Phase" and recycling these phases to the reactor partially or totally with or without further treatment. Further, no attention has been paid to the behavior of catalyst, such as solubility, for example, during reaction conditions.
It is also important to note that most, if not all, studies on the Direct Synthesis Process have been conducted in a batch mode, literally or for all practical purposes.
There is a plethora of references dealing with oxidation of organic compounds to produce acids, such as, for example, adipic acid, benzoic acid, phthalic 10 acid, isophthalic acid, terephthalic acid, etc.
The following references, among the plethora of others, may be considered as representative of oxidation processes relative to the preparation of diacids, and especially adipic acid.
U.S. Patent 5,463,119 (Kollar) discloses a process for the oxidative 15 preparation of C5-C8 aliphatic dibasic acids by ( 1 ) reacting, (a) at least one saturated cycloaliphatic hydrocarbon having from 5 to 8 ring carbon atoms in the liquid phase and (b) an excess of oxygen gas or an oxygen-containing gas in 20 the presence of (c) a solvent comprising an organic acid containing only primary and/or secondary hydrogen atoms and (d) at least about 0.002 mole per 1000 grams of reaction mixture of a polyvalent heavy metal catalyst;
CROSS-REFERENCE TO RELATED APPLICATION
The present application claims priority from U.S. Provisional Application No. 60/033,831 filed December 23, 1996, and from U.S. Non-Provisional Application No. 08/861,210 filed May 21, 1997, which applications are incorporated herein by reference in their entireties.
This invention relates to devices for controlling reactions with special emphasis to oxidations. The reactor of this invention behaves in a manner similar to the manner that a plug-flow reactor behaves.
Plug-flow reactors and processes are well known to the art. They are usually characterized by their ability to allow a mixture of reactants to undergo a reaction as the mixture flows from one end to the other end of the reactor without any substantial back mixing. In order to achieve conditions which allow plug-flow, it is 20 important that the reactants are homogeneous, in either gaseous or liquid state (including dispersions, aerosols, and homogeneous powder or dust containing gases), and preferably in one phase. If all reactants are in the same liquid phase, which flows from one end to the other end of the reactor, back mixing may be avoided more easily than in the case that all reactants are in the gaseous phase, because of molecular 25 mobility reasons.
If one reactant is in a liquid state and the other in gaseous state, it becomes extremely difficult, if not impossible to produce plug-flow conditions with the presently known techniques.
There are many reactions, which require that one reactant is in the liquid 30 state, while the other reactant is in the gaseous state. One example is the case of miscellaneous oxidations, wherein for example a hydrocarbon is oxidized to form an CA 0222~763 1997-12-23 intermediate oxidation product. In such cases, the present art utilizes stirred-tank conditions, which lack completely the advantages of plug-flow conditions. Our recent patents and patent applications on atomization technology, although they provide a great advance in the art of reactions in general, with special emphasis in oxidations, are 5 not characterized by plug-flow conditions.
There is a plethora of references (both patents and literature articles) dealing with the formation of intermediate oxidation products, such as diacids, for example, one of the most important being adipic acid. Adipic acid is used to produce Nylon 66 fibers and resins, polyesters, polyurethanes, and miscellaneous other 1 0 compounds.
There are different processes of manufacturing adipic acid. The conventional process involves a first step of oxidizing cyclohexane with oxygen to a mixture of cyclohexanone and cyclohexanol (KA mixture), and then oxidation of the KA mixture with nitric acid to adipic acid. Other processes include, among others, the 15 "Hydroperoxide Process," the "Boric Acid Process," and the "Direct Synthesis Process," which involves direct oxidation of cyclohexane to adipic acid with oxygen in the presence of solvents, catalysts, and initiators or promoters.
Initiators or promoters are presently being used to shorten considerably an induction period at the beginning of the reaction. Accepted explanations, which 20 have been given regarding the role of the initiators or promoters, involve oxidation of the catalyst, which is usually cobaltous ions to cobaltic ions.
The Direct Synthesis Process has been given attention for a long time.
However, to this date it has found little commercial success. One of the reasons is that although it looks very simple at first glance, it is extremely complex in reality. Due to 25 this complexity, one can find strikingly conflicting results, comments, and views in different references.
It is well known that after a reaction has taken place according to the Direct Synthesis Process, a mixture of two liquid phases is present at ambient temperature, along with a solid phase mainly consisting of adipic acid. The two liquid 30 phases have been called the "Polar Phase" and the "Non-Polar" phase. However, no CA 0222~763 1997-12-23 attention has been paid so far to the importance of the two phases, except for separating the adipic acid from the "Polar Phase" and recycling these phases to the reactor partially or totally with or without further treatment. Further, no attention has been paid to the behavior of catalyst, such as solubility, for example, during reaction conditions.
It is also important to note that most, if not all, studies on the Direct Synthesis Process have been conducted in a batch mode, literally or for all practical purposes.
There is a plethora of references dealing with oxidation of organic compounds to produce acids, such as, for example, adipic acid, benzoic acid, phthalic 10 acid, isophthalic acid, terephthalic acid, etc.
The following references, among the plethora of others, may be considered as representative of oxidation processes relative to the preparation of diacids, and especially adipic acid.
U.S. Patent 5,463,119 (Kollar) discloses a process for the oxidative 15 preparation of C5-C8 aliphatic dibasic acids by ( 1 ) reacting, (a) at least one saturated cycloaliphatic hydrocarbon having from 5 to 8 ring carbon atoms in the liquid phase and (b) an excess of oxygen gas or an oxygen-containing gas in 20 the presence of (c) a solvent comprising an organic acid containing only primary and/or secondary hydrogen atoms and (d) at least about 0.002 mole per 1000 grams of reaction mixture of a polyvalent heavy metal catalyst;
(2) removing the aliphatic dibasic acid; and (3) recycling intermediates, post oxidation components, and derivatives thereof rem~ining after removal of the aliphatic dibasic acid into the oxidation reaction.
U.S. Patent 5,374,767 (Drinkard et al) discloses formation of 30 cyclohexyladipates in a staged reactor, e.g, a reactive distillation column. A mixture CA 0222~763 1997-12-23 containing a major amount of benzene and a minor amount of cyclohexene is fed to the lower portion of the reaction zone and adipic acid is fed to the upper portion of the reaction zone, cyclohexyladipates are formed and removed from the lower portion of the reaction zone and benzene is removed from the upper portion of the reaction zone.
The reaction zone also contains an acid catalyst.
U.S. Patent 5,321,157 (Kollar) discloses a process for the preparation of C5- C8 aliphatic dibasic acids through oxidation of corresponding saturated cycloaliphatic hydrocarbons by (1) reacting, at a cycloaliphatic hydrocarbon conversion level of 10 between about 7% and about 30%, (a) at least one saturated cycloaliphatic hydrocarbon having from 5 to 8 ring carbon atoms in the liquid phase and (b) an excess of oxygen gas or an oxygen cont~ining gas mixture in the presence of (c) less than 1.5 moles of a solvent per mole of cycloaliphatic hydrocarbon (a), wherein said solvent comprises an organic acid containing only primary and/or secondary hydrogen atoms and (d) at least about 0.002 mole per 1000 grams of reaction mixture of a polyvalent heavy metal catalyst; and (2) isolating the C5 - C8 aliphatic dibasic acid.
U.S. Patent 5,221,800 (Park et al.) discloses a process for the manufacture of adipic acid is disclosed. In this process, cyclohexane is oxidized in an aliphatic monobasic acid solvent in the presence of a soluble cobalt salt wherein water is continuously or intermittently added to the reaction system after the initiation of 25 oxidation of cyclohexane as indicated by a suitable means of detection, and wherein the reaction is conducted at a temperature of about 50~C to about 150~C at an oxygen partial pressure of about 50 to 420 pounds per square inch absolute.
U.S. Patent 3,987,100 (Barnette et al.) describes a process of oxidizing cyclohexane to produce cyclohexanone and cyclohexanol, said process comprising 30 contacting a stream of liquid cyclohexane with oxygen in each of at least three CA 0222~763 1997-12-23 successive oxidation stages by introducing into each stage a mixture of gases comprising molecular oxygen and an inert gas.
U.S. Patent 3,957,876 (Rapoport et al.) describes a process for the preparation of cyclohexyl hydroperoxide substantially free of other peroxides by5 oxidation of cyclohexane containing a cyclohexane soluble cobalt salt in a zoned oxidation process in which an oxygen containing gas is fed to each zone in the oxidation section in an amount in excess of that which will react under the conditions of that zone.
U.S. Patent 3,932,513 (Russell) discloses the oxidation of cyclohexane 10 with molecular oxygen in a series of reaction zones, with vaporization of cyclohexane from the last reactor effluent and parallel distribution of this cyclohexane vapor among the series of reaction zones.
U.S. Patent 3,530,185 (Pugi) discloses a process for manufacturing precursors of adipic acid by oxidation with an oxygen-containing inert gas which15 process is conducted in at least three successive oxidation stages by passing a stream of liquid cyclohexane maintained at a temperature in the range of 140 ~C to 200 ~C and a pressure in the range of 50 to 350 p.s.i.g. through each successive oxidation stage and by introducing a mixture of gases containing oxygen in each oxidation stage in an amount such that substantially all of the oxygen introduced into each stage is consumed 20 in that stage thereafter causing the residual inert gases to pass countercurrent into the stream of liquid during the passage of the stream through said stages.
U.S. Patent 3,515,751 (Oberster et al.) discloses a process for the production of epsilon-hydroxycaproic acid in which cyclohexane is oxidized by liquid phase air oxidation in the presence of a catalytic amount of a lower aliphatic carboxylic 25 acid and a catalytic amount of a peroxide under certain reaction conditions so that most of the oxidation products are found in a second, heavy liquid layer, and are directed to the production of epsilon-hydroxycaproic acid.
U.S. Patent 3,361,806 (Lidov et al) discloses a process for the production of adipic acid by the further oxidation of the products of oxidation of cyclohexane after 30 separation of cyclohexane from the oxidation mixture, and more particularly to stage CA 0222~763 1997-12-23 wise oxidation of the cyclohexane to give high yields of adipic acid precursors and also to provide a low enough concentration of oxygen in the vent gas so that the latter is not a combustible mixture.
U.S. Patent 3,234,271 (Barker et al) discloses a process for the 5 production of adipic acid by the two-step oxidation of cyclohexane with oxygen. In a preferred embodiment, mixtures comprising cyclohexanone and cyclohexanol are oxidized. In another embodiment, the process involves the production of adipic acid from cyclohexane by oxidation thereof, separation of cyclohexane from the oxidation mixture and recycle thereof, and further oxidation of the other products of oxidation.
U.S. Patent 3,231,608 (Kollar) discloses a process for the preparation of aliphatic dibasic acids from saturated cyclic hydrocarbons having from 4 to 8 cyclic carbon atoms per molecule in the presence of a solvent which comprises an aliphatic monobasic acid which contains only primary and secondary hydrogen atoms and a catalyst comprising a cobalt salt of an organic acid, and in which process the molar ratio of said solvent to said saturated cyclic hydrocarbon is between 1.5:1 and 7:1, and in which process the molar ratio of said catalyst to said saturated cyclic hydrocarbon is at least 5 millimoles per mole.
U.S. Patent 3,161,603 (Leyshon et al) discloses a process for recovering the copper-vanadium catalyst from the waste liquors obtained in the manufacture of adipic acid by the nitric acid oxidation of cyclohexanol and/or cyclohexanone.
U.S. Patent 2,565,087 (Porter et al) discloses the oxidation of cycloaliphatic hydrocarbons in the liquid phase with a gas containing molecular oxygen and in the presence of about 10% water to produce two phases and avoid formation of esters.
U.S. Patent 2,557,282 (Hamblet et al) discloses production of adipic acid and related aliphatic dibasic acids; more particularly to the production of adipic acid by the direct oxidation of cyclohexane.
U.S. Patent 2,439,513 (Hamblet et al) discloses the production of adipic acid and related aliphatic dibasic acids and more particularly to the production of adipic acid by the oxidation of cyclohexane.
CA 0222~763 1997-12-23 U.S. Patent 2,223,494 (Loder et al) discloses the oxidation of cyclic saturated hydrocarbons and more particularly to the production of cyclic alcohols and cyclic ketones by oxidation of cyclic saturated hydrocarbons with an oxygen-containing gas.
5U.S. Patent 2,223,493 (Loder et al) discloses the production of aliphatic dibasic acids and more particularly to the production of aliphatic dibasic acids by oxidation of cyclic saturated hydrocarbons with an oxygen-containing gas.
German Patent DE 44 26 132 A 1 (Kysela et al.) discloses a method for dehydration of process acetic acid from the liquid-phase oxidation of cyclohexane with 10air, in the presence of cobalt salt as a catalyst after separation of the adipic acid by filtration and the cyclohexane phase by phase separation, while simultaneously avoiding cobalt salt precipitates in the dehydration column, characterized in that the acetic acid phase to be returned to the beginning of the process is subjected to azeotropic distillation by the use of added cyclohexane, under distillative removal of the water 15down to a residual content of less than about 0.3 to 0.7 wt %.
PCT Demand International publication WO 96/03365 (Costantini et al.) discloses a method of recycling a cobalt-cont~ining catalyst in a reaction involving the direct oxidation of cyclohexane into adipic acid using an oxygen containing gas. The method is characterized in that the reaction mixture, obtained in a preceding stage 20where the cyclohexane was oxidized into adipic acid, of which at least part of the intermediate oxidation products, such as cyclohexanol and cyclohexanone, the carboxylic acid and water has been separated and of which at least part of the adipic acid formed has been recovered by cryst~lli7~tion, undergoes at least one extraction operation using at least one cosolvent or a mixture comprising a cosolvent and a25carboxylic acid. The method is also characterized by the separation of a mixture containing at least part of the cobalt catalyst, part of the carboxylic acid and optionally residual quantities of other compounds and a solution containing the co-solvent and at least part of the glutaric and succinic acids formed during the oxidation reaction, and the carboxylic acid.
CA 0222~763 1997-12-23 The following references, among others, describe processes conducted in intermixing liquid with gaseous materials, mostly under increased surface area conditions.
U.S. Patent No. 5,399,750 (Brun et al.) discloses methods for preparing 5 maleamic acid (aminomaleic acid) by reacting gaseous ammonia with molten maleic anhydride under reactant contact conditions of high surface area, for example reacting said gaseous NH3 with a thin film of said molten maleic anhydride or with said molten maleic anhydride in a state of vigorous agitation.
U.S. Patent No. 5,396,850 (Connote et al.) discloses a method of 10 destroying organic waste in a bath of molten metal and slag contained in a vessel. The method comprises injecting organic waste into the bath to form a primary reaction zone in which the organic waste is thermally cracked and the products of the thermal cracking which are not absorbed into the bath are released into the space above the surface of the bath. The method further comprises injecting an oxygen-containing gas 15 toward the surface of the bath to form a secondary reaction zone in the space above the surface of the bath in which the oxidizable materials in the products from the primary reaction zone are completely oxidized and the heat released by such oxidation istransferred to the bath. In order to facilitate efficient heat transfer from the second reaction zone to the bath, the method further comprises injecting an inert or other 20 suitable gas into the bath to cause molten metal and slag to be ejected upwardly from the bath into the secondary reaction zone.
U.S. Patent No. 5,312,567 (Kozma et al.) discloses a complex mixing system with stages consisting of propeller mixers of high diameter ratio, where the blades are provided with flow modifying elements, whereby the energy proportions25 spent on dispersion of the amount of gas injected into the reactor, homogenization of the multi-phase mixtures, suspension of solid particles, etc. and the propertiescorresponding to the rheological properties of the gas-liquid mixtures and to the special requirements of the processes can be ensured even in extreme cases. Open channels opposite to the direction of rotation are on the blades of the dispersing stage of the 30 propeller mixers fixed to a common shaft, where the channels are interconnected with CA 0222~763 1997-12-23 gas inlet. The angle of incidence of a certain part of the blades of mixing stages used for homogenization and suspension is of opposite direction and the length is shorter and/or the angle of incidence is smaller than those of the other blades. Baffle bars are on the trailing end of the blades on a certain part of the propeller mixers used similarly for homogenization and suspension, and/or auxiliary blades at an angle of max. 20~ to the blade wings are arranged above or below the trailing end of the blades.
U.S. Patent No. 5,244,603 (Davis) discloses a gas-liquid mixing system which employs an impeller/draft tube assembly submerged in liquid. Hollow eductor tubes affixed to the impeller drive shaft are used to flow gas from an overhead gas space 10 to the liquid in the vicinity of the assembly. The positioning and size of the eductor tubes are such as to maximize the desired gas-liquid mixing and reaction rate.
U.S. Patent No. 5,270,019 (Melton et al.) discloses an elongated, generally vertically extending concurrent reactor vessel for the production of hypochlorous acid by the mixing and reaction of a liquid alkali metal hydroxide and a 15 gaseous halogen, wherein an atomizer is mounted near the top of the reactor vessel to atomize the liquid alkali metal hydroxide into droplets in the vessel. The vessel has a spraying and reaction zone immediately beneath the atomizer and a drying zone beneath the spraying and reaction zone to produce a gaseous hypochlorous acid and a substantially dry solid salt by-product.
U.S. Patent No. 5,170,727 (Nielsen) discloses a process and apparatus in which supercritical fluids are used as viscosity reduction diluents for liquid fuels or waste materials which are then spray atomized into a combustion chamber. The addition of supercritical fluid to the liquid fuel and/or waste material allows viscous petroleum fractions and other liquids such as viscous waste materials that are too 25 viscous to be atomized (or to be atomized well) to now be atomized by this invention by achieving viscosity reduction and allowing the fuel to produce a combustible spray and improved combustion efficiency. Moreover, the present invention also allows liquid fuels that have suitable viscosities to be better utilized as a fuel by achieving further viscosity reduction that improves atomization still further by reducing droplet size 30 which enhances evaporation of the fuel from the droplets.
CA 0222~763 1997-12-23 U.S. Patent No. 5,123,936 (Stone et al.) discloses a process and apparatus for removing fine particulate matter and vapors from a process exhaust air stream, and particularly those emitted during post-production curing or post-treatment of foamed plastics, such as polyurethane foam, in which the exhaust air stream is passed 5 through a transfer duct into which is introduced a water spray in the form of a mist of fine droplets in an amount which exceeds the saturation point; thereafter the exhaust air stream is introduced into a filter chamber having a cross-sectional area that issubstantially greater than that of the transfer duct, and the exhaust air stream passes through at least one, and preferably a plurality of high surface area filters, whereby a 10 portion of the water is removed from the exhaust air stream and collected in the filter chamber prior to the discharge of the exhaust air stream into the environment.
U.S. Patent No. 5,061,453 (Krippl et al.) discloses an apparatus for continuously charging a liquid reactant with a gas. The gas is dispersed in the reactant through a hollow stirrer in a gassing tank. The quantity of gas introduced per unit time 15 is kept constant.
U.S. Patent No. 4,423,018 (Lester, Jr. et al.) discloses a process according to which a by-product stream from the production of adipic acid from cyclohexane, containing glutaric acid, succinic acid and adipic acid, is employed as a buffer in lime or limestone flue gas scrubbing for the removal of sulfur dioxide from 20 combustion gases.
U.S. Patent No. 4,370,304 (Hendriks et al.) discloses methods by which ammonium orthophosphate products are prepared by reacting ammonia and phosphoricacid together at high speed under vigorous mixing conditions by spraying the reactants through a two-phase, dual coaxial mixer/sprayer and separately controlling the supply 25 and axial outflow rate of the phosphoric acid at 1 to 10 m/sec. and the outflow rate of ammonia at 200 to 1000 m/sec. (N.T.P.). Thorough mixing and a homogenous productis obtained by directing the outflow spray into a coaxial cylindrical reaction chamber of a specified size with respect to the diameter of the outermost duct of the sprayer/mixer.
The product may be granulated on a moving bed of granules and adjusted in respect of CA 0222~763 1997-12-23 the NH3 to H3PO4 content by ch~n~;ing the concentration of the phosphoric acid and/or supplying additional ammonia to the granulation bed.
U.S. Patent No. 4,361,965 (Goumondy et al.) discloses a device for atomizing a reaction mixture, said device enabling the reaction mixture to be atomized 5 in a reactor with the aid of at least a first gas and an atomizing nozzle. This device further comprises a supply of a second hot gas at the top of the atomizing device, serving to dry the atomized mixture, a supply of a third gas and means for distributing this third gas comprising an annular space of adjustable width and adapted to distribute in the reactor said third gas in the form of a ring along the inner wall of the reactor, so 10 as to avoid any contact between the reaction mixture and said wall. The invention is applicable to the atomization of a reaction mixture.
U.S. Patent No. 4,308,037 (Meissner et al.) discloses methods according to which high temperature thermal exchange between molten liquid and a gas stream is effected by generating in a confined flow passageway a plurality of droplets of molten 15 liquid and by passing a stream through the passageway in heat exchange relationship with the droplets. The droplets are recovered and adjusted to a predetermined temperature by means of thermal exchange with an external source for recycle. The process provides for removal of undesired solid, liquid or gaseous components.
U.S. Patent No. 4,065,527 (Graber) discloses an apparatus and a method 20 for handling a gas and a liquid in a manner to cause a specific interaction between them.
The gas is placed into circulation to cause it to make a liquid circulate in a vortex fashion to present a liquid curtain. The gas is then passed through the liquid curtain by angled vanes to cause the interaction between the two fluids, such as the heating of the liquid, scrubbing of the gas, adding a chemical to the liquid and the like. The vanes are 25 spaced apart and project inwardly from the inner periphery of an annular support so that the circulating liquid readily moves into the spaces between the vanes to create the liquid curtain. A number of embodiments of the invention are disclosed.
U.S. Patent No. 4,039,304 (Bechthold et al.) discloses methods according to which waste gas is contacted with a solution of a salt from a pollutant of 30 the gas. This solution is obtained from another stage of the process used for cleaning or CA 0222~763 1997-12-23 purifying the gas. The resulting mixture of gas and solution is subjected to vaporization so as to obtain a dry gaseous substance constituted by the waste gas and the evaporated solvent for the salt. The gaseous substance thus formed contains crystals of the salt as well as the pollutant present in the original waste gas. The salt crystals and other solid 5 particles are removed from the gaseous substance in the form of a dry solids mixture.
The gaseous substance is subsequently mixed with an absorption fluid such as an ammonia solution in order to wash out and redissolve any salt crystals which mayremain in the gaseous substance and in order to remove the pollutant present in the original waste gas from the gaseous substance. The pollutant and the redissolved salt 10 crystals form a salt solution together with the absorption fluid and it is this salt solution which is brought into contact with the waste gas. The gaseous substance is exhausted to the atmosphere after being mixed with the absorption fluid.
U.S. Patent No. 3,928,005 (Laslo) discloses a method and apparatus for treating gaseous pollutants such as sulfur dioxide in a gas stream which includes a wet 15 scrubber wherein a compressed gas is used to atomize the scrubbing liquid and a nozzle and the compressed gas direct the atomized liquid countercurrent to the flow of gas to be cleaned. The method and apparatus includes pneumatically conveying to the nozzle a material such as a solid particulate material which reacts with or modifies the pollutant to be removed or altered. The gas used for atomizing the scrubbing liquid is 20 also used as a transport vehicle for the solid particulate material. In the case of sulfur oxides, the material may be pulverized limestone.
U.S. Patent No. 3,677,696 (Bryk et al.) discloses a method according to which, the concentration of circulating sulfuric acid is adjusted to 80-98% by weight and used to wash hot gases cont~ining mercury. The temperature of the acid is 25 m~int~ined between 70-250~C, and the solid material separating from the circulating wash solution is recovered.
U.S. Patent No. 3,613,333 (Gardenier) discloses a process and apparatus for removing cont:~min~nts from and pumping a gas stream comprising indirectly heat exch~nging the gas and a liquid, introducing the liquid under conditions of elevated 30 temperature and pressure in vaporized and atomized form into the gas, mixing same CA 0222~763 1997-12-23 thereby entrapping the cont:~min~nts, and separating clean gas from the atomized liquid containing the cont~min~nts.
U.S. Patent No. 2,980,523 (Dille et al.) discloses a process for the production of carbon monoxide and hydrogen from carbonaceous fuels by reaction with 5 oxygen. In one of its more specific aspects it is directed to a method of separating carbonaceous solid entrained in the gaseous products of reaction of carbonaceous fuels and oxygen wherein said products are contacted with a limited amount of liquid hydrocarbon and thereafter scrubbed with water, and said carbonaceous solid is decanted from said clarified water.
U.S. Patent No. 2,301,240 (Ba-lm~nn et al.) discloses an improved process for removing impurities from acetylene gas which has been prepared by thermal or electrical methods by washing with organic liquids, as for example oils or tars.
U.S. Patent No. 2,014,044 (Haswell) discloses an improved method for treating gas and aims to provide for the conservation of the sensible heat of such gas.
U.S. Patent No. 1,121,532 (Newberry) discloses a process of recovering alkalis from flue-gases.
None of the above references, or any other references known to the inventors disclose, suggest or imply, singly or in combination, oxidation of cyclic hydrocarbons to dibasic acids in multiple stages of temperature/conversion, subject to 20 the intricate and critical controls and requirements of the instant invention as described and claimed.
Our U.S. Patents 5,580,531, 5,558,842, 5,502,245, and our co-pending applications 08/477,195 (filed 06/07/95), 08/587,967 (filed 01/17/96), and 08/620,974 (filed 03/25/96), all of which are incorporated herein by reference, describe methods 25 and apparatuses relative to controlling reactions in atomized liquids.
Our co-pending U.S. Patent Application No. 08/812,847 of Mark W.
Dassel, Eustathios Vassiliou, David C. DeCoster, Ader M. Rostami, and Sharon M.
Aldrich, titled "Methods and Devices for Controlling the Reaction Rate of a Hydrocarbon to an Acid by Making Phase-related Adjustments", filed on March 6, 30 1997, is also incorporated herein by reference.
CA 0222~763 1997-12-23 Our co-pending U.S. Patent Application No. 08/824,992 of Mark W.
Dassel, David C. DeCoster, Ader M. Rostami, Sharon M. Aldrich, and Eustathios Vassiliou, titled "Methods and Devices for Preparing Dibasic Acids", filed on March 27, 1997, is also incorporated herein by reference.
All of the following patent applications, each of which was filed on May 21, 1997 are also incorporated herein by reference:
U.S. Patent Application No. 08/859,985 of Eustathios Vassiliou, Mark W. Dassel, David C. DeCoster, Ader M. Rostami, and Sharon M. Aldrich, titled "Methods and Devices for Controlling the Reaction Rate of a Hydrocarbon to an 10 Intermediate Oxidation Product by Pressure Drop Adjustments";
U.S. Patent Application No. 08/861,281 of Mark W. Dassel, Eustathios Vassiliou, David C. DeCoster, Ader M. Rostami, and Sharon M. Aldrich, titled "Methods and Devices for Controlling the Reaction Rate of a Hydrocarbon to an Intermediate Oxidation Product by Monitoring Flow of Incoming and Outcoming 15 Gases";
U.S. Patent Application No. 08/861,180 of David C. DeCoster, Ader M.
Rostami, Mark W. Dassel, and Eustathios Vassiliou, titled "Methods and Devices for Controlling the Oxidation Rate of a Hydrocarbon by Adjusting the Ratio of the Hydrocarbon to a Rate-Modulator";
U.S. Patent Application No. 08/861,176 of Mark W. Dassel, Eustathios Vassiliou, David C. DeCoster, and Ader M. Rostami, titled "Methods of Preparing an Intermediate Oxidation Product from a Hydrocarbon by Utilizing an Activated Initiator"; and U.S. Patent Application No. 08/859,890 of Ader M. Rostami, Mark W.
25 Dassel, Eustathios Vassiliou, David C. DeCoster, titled "Methods and Devices for Controlling the Oxidation of a Hydrocarbon to an Acid by Regulating Temperature/Conversion Relationship in Multi-Stage Arrangements."
SUMMARY OF THE INVENTION
As aforementioned, this invention relates to reactors behaving in a similar manner as plug-flow reactors. More particularly, the instant invention relates to CA 0222~763 1997-12-23 a reactor comprising a reaction chamber having an elongate body, a liquid feed side, a coalescing side, a front end, a back end, a cross section, a length, a width, and an axis, the reactor comprising:
a first reactant feed line for introducing a first reactant to the reactor, the first reactant being non-gaseous;
a plurality of liquid-feed inlets at the liquid feed side of the reactor, the liquid-feed inlets being adapted to feed a liquid in a direction substantially perpendicular to the direction of the axis, and in a manner that the liquid changes direction from substantially perpendicular to substantially parallel to the direction of the 10 axis at the coalescing side of the reactor;
a gas feed line adapted to feed a gas containing a second reactant to the reactor; and reaction-inducing means for causing a reaction to take place between the first reactant and the second reactant to form a reaction product, in at least a portion of 15 the reaction chamber. Examples of such means are temperature and/or pressure control means, such as for example heaters, coolers, compressors, etc., preferably accompanied by monitoring equipment, etc., all well known to the art.
It is highly preferable that at least one of the plurality of the liquid-feed inlets may comprise an atomizer for atomizing the liquid in a form of a pattern, which is 20 preferably linear. However, at least one of the plurality of the liquid-feed inlets may comprise an orifice adapted to form streams of liquid, and/or a spatter producing mech~ni .~m .
The cross-section of the reaction chamber may have any shape, but it is preferably circular, and more preferably triangular.
Also preferably, the gas feed line is located in the vicinity of the front end of the reaction chamber and the first reactant feed line is in the vicinity of the back end of the reaction chamber.
It is preferable that the reaction chamber further comprises restrictive baffles forming pools at the coalescing side of said reaction chamber. The reactor may CA 0222~763 1997-12-23 also preferably comprise a re-circulator for transferring liquid from the coalescing side to predeterrnined liquid feed inlets.
The predetermined liquid feed inlets, the feed of which originates from a given pool, may preferably be located between the pool and the front end, or above the pool, while the gas feed line may be also located under said pool.
It is preferable that at least two of the pools have different capacities, more preferable that pools toward the front end have higher capacities than pools toward the back end, and even more preferable that the pools have progressively larger capacities going from the back end toward the front end of the reaction chamber.10 Degree of inclination of the reaction chamber, different heights of baffles or different distances between consecutive baffles are examples of ways to modify the capacities of the pools.
The ratio of the length of the reaction chamber to the width of said reaction chamber is preferably higher than 10. The reaction chamber may be inclined or 15 it may be substantially horizontal. Means for adjusting the degree of inclination of the reaction chamber may also be provided. Such means may be for example hydraulic or other types of lifters, well known to the art, which may adjust one or both ends of the reaction chamber, thus ch~n~;ing the degree of inclination of the reaction chamber. In addition, one or both ends of the reaction chamber may be pivoted.
The reaction chamber may be divided into different sections adapted to operate under different conditions. The reactor may comprise additional inlets in at least one of the different sections, for introducing matter ch~nging reaction characteristics in the at least one of the different sections. The reaction chamber may further comprise means for removing reaction product between at least one pool and the 25 respective liquid feed inlet. Also, by-products such as water for example, or recyclable products, may be removed in a similar manner.
BRIEF DESCRIPTION OF THE DRAWING
The reader's understanding of this invention will be enhanced by 30 reference to the following detailed description taken in combination with the drawing figures, wherein:
CA 0222~763 1997-12-23 FIGURES 1 A, I B, AND 1 C illustrate schematically examples of miscellaneous general configurations of the reactors according to the present invention.
FIGURES 2A through 2E illustrate schematically examples of miscellaneous general cross sections of the reaction chambers according to the present invention.
FIGURE 3 illustrates schematically an inclined reactor according to a preferred embodiment of the present invention wherein liquids are recirculated from pools to sets of liquid feed inlets.
FIGURE 4 illustrates schematically a fragmented view of another 10 preferred embodiment of the present invention, wherein a filter is used in the re-circulation line.
FIGURES 5 and 6 illustrate schematically examples of segments of the reaction chamber according to a preferred embodiment of the present invention.
FIGURES 7 and 8 illustrate schematically examples of atomized liquids 15 through liquid feed lines or atomizers.
FIGURE 9 illustrates schematically a fragmented view of a reaction chamber according to another preferred embodiment of the instant invention, wherein the liquid feed inlets in the form of atomizers are stacked very close to each other in order to provide high concentration of droplets in linear spray patterns.
FIGURE 10 illustrates schematically a linear spray pattern.
FIGURE 11 illustrates schematically a circular or elliptical spray pattern.
FIGURE 12 illustrates schematically a reaction chamber with a circular cross section having triple feed inlets in order to maximize the density of liquid droplets after the triple inlets have been stacked as illustrated in the reaction chamber of Figure 25 9.
FIGURE 13 illustrates schematically a reaction chamber having a triangular cross section, wherein three substantially flat plates are connected together.
FIGURE 14 illustrates schematically a fragmented view of a reaction chamber according to another preferred embodiment of the instant invention, wherein 30 the gas feed line is positioned under a pool.
CA 0222~763 l997-l2-23 FIGURE 15 illustrates schematically a horizontal reaction chamber according to another preferred embodiment of the instant invention.
FIGURE 16 illustrates schematically a horizontal reaction chamber according to another preferred embodiment of the instant invention, wherein each re-5 circulator pump, re-circulates the liquid through a respective 3-way valve in a way that part of the liquid is dispensed, preferably atomized, immediately above the pool under consideration and part of the liquid is dispensed above a pool further away from the back end and closer to the front end of the reaction chamber.
FIGURE 17 illustrates schematically a reaction chamber according to 10 another preferred embodiment of the instant invention, wherein a first section of the reaction chamber is controlled to have a higher temperature than a second section.
FIGURE 18 illustrates schematically a reaction chamber according to another preferred embodiment of the instant invention, wherein the reaction chamber is separated in a back section and a front section, as well as an additional inlet for 15 introducing other desirable ingredients.
DETAILED DESCRIPTION OF THE INVENTION
As aforementioned, this invention relates to reactors behaving in a similar manner as plug-flow reactors. The reactor of the instant invention is very useful 20 in most cases wherein one reactant is a liquid or a substance contained in a liquid and the other reactant is a gas, or a substance contained in a gas. Examples include but are not limited to formation of maleamic acid, formation of ammonium phosphate, etc., wherein one reactant is in the liquid state and the other reactant is in the gaseous state.
This invention is particularly fit for oxidations, such as for example oxidation of 25 cyclohexane to cyclohexanone and/or cyclohexanol, and/or cyclohexyhydroperoxide, and/or adipic acid, oxidation of cyclohexanone and/or cyclohexanol to cyclohexylhydroperoxide, and/or adipic acid, oxidation of cyclohexylhydroperoxide to adipic acid, oxidation of toluene to benzoic acid, oxidation of o-xylene to phthalic acid, oxidation of m-xylene to isophthalic acid, oxidation of p-xylene to terephthalic acid, 30 etc.
CA 0222~763 1997-12-23 The reactor 10, as better illustrated in Figures lA to lC, comprises a reaction chamber 12, which in turn comprises an elongated body 13, a front end 14, a back end 16, a length L, a width W, and an axis X. The ratio of the length L to the width W is preferably larger than 10 The general shape of the reactor l O of this invention may have any of a plurality of configurations. In one example, illustrated in Figure lA, the general shape of the reactor l O has the form of a coil. In another example, illustrated in Figure 1 B, the general shape of the reactor 10 has the form of two inclined straight segments connected together. In still another example, illustrated in Figure lC, the general shape of the 10 reactor lO has the form of a single inclined segment. The reactor lO, may also be substantially horizontal, as will be illustrated at a later point.
The inclination of the reaction chamber 12 is preferably lower than 45 degrees and more preferably in the range of 5 to 20 degrees. The reaction chamber 12 may also be substantially horizontal.
Means for adjusting the degree of inclination (not shown) of the reaction chamber 12 may also be provided. Such means may be for example hydraulic lifters or other types of lifters, well known to the art, which may adjust one or both ends of the reaction chamber, thus ch:~nging the degree of inclination of the reaction chamber. In addition, one or both ends of the reaction chamber may be pivoted.
The cross-sections of the different segments of the reactor 10 may have different shapes. Examples of some of the most common cross-sections are illustrated in Figures 2A through 2E. The most preferred cross-sections, for reasons to be explained later are a circular cross-section illustrated in Figure 2A, and a triangular cross-section illustrated in Figure 2D.
The reaction chamber 12, as better illustrated in Figure 3, also has preferably a liquid feed side 18, a coalescing side 20, a first reactant feed line 22, a liquid exit port 23, a gas feed line 24, sets 26 of liquid feed inlets 28, each set 26 cont~ining one or more liquid feed inlets 28, and a condenser 30, provided with a valve 31, for condensing condensables and allowing off-gases to be moved out of the system.
30 Preferably, a demister (not shown), well known to the art, may be placed between the CA 0222~763 1997-12-23 reaction chamber 12 and the condenser 30. It is preferable that that the reaction chamber 12 has baffles 32, which form pools 34 in the coalescing side 20. The pools 34 are adapted to restrict liquid matter from free flowing from the back end 16 to the front end 18 of the reaction chamber 12. In many occasions, it is preferable that at least two 5 pools have different capacities, more preferable that the pools toward the front end 14 are larger or have larger capacities than the pools toward the back end 16, and it is even more preferable that the pools have progressively higher capacities going from the back end 16 toward the front end 14. One of the reasons why is that the reaction rate usually decreases as the reaction progresses, and the reaction progresses in the reaction chamber 10 12 as the liquid moves from the back end 16 to the front end 14.
The reactor 10, may also comprise a re-circulator, in the form of a pump 36 for example, which is adapted to re-circulate liquid matter from the pools 34 to predetermined inlets 28 or sets of inlets 26. A filter 35 may be used in the re-circulator line 37 for removing precipitated matter, such as adipic acid for example in the case of 15 oxidation of cyclohexane to adipic acid, as better shown in Figure 4. A cooler (not shown) may be used between the pool and the filter 35 to promote precipitation and to remove heat of reaction. Also, a heat exchanger (not shown), preferably a heater, may be used after the filter and before the liquid feed inlets 28 to raise the temperature adequately for the reaction to proceed, and ensure solubilization of any precipitate that 20 might form after the filter.
Filters in the re-circulation lines are preferably employed in pools located after the reaction has progressed adequately to filter out the product of reaction, adipic acid for example. In this particular case, at the early stages, no filters are necessary. In order to remove the heat of reaction at the early stages and in the absence 25 of a filter, a cooler may be used in such a manner that the temperature does not decrease to a point that reaction cannot proceed and/or to the point that reaction product, adipic acid for example, is precipitated. In addition, it may be prudent to m~int~in the temperature of the heat exchanger cooling fluid at a higher temperature than thetemperature of precipitation of any solids dissolved, to avoid deposition of solids on the 30 heat exchanger surfaces.
CA 0222~763 1997-12-23 The re-circulation line may also be divided in one stream of lower temperature and one stream of higher temperature, the two streams being fed through different atomizers in the same vicinity. As explained in more detail in our co-pending application Serial Number 08/587,967, filed 01/17/96, which is incorporated herein by 5 reference, the heat produced by the reaction in the higher temperature droplets is removed by evaporation of volatile matter, which matter condenses on the lower temperature droplets.
A jacket around the reaction chamber may also be used for removing heat of reaction by recirculating cooling liquids through the jacket.
Exemplary segments of the reaction chamber 12 are better illustrated in Figures 5 and 6. A plurality of segments as shown in Figure 5 may be connected together through flanges 38.
Preferably, the liquid feed inlets 28 comprise or are in the form of atomizers. Atomized liquids have the advantage of providing an extremely high surface 15 area, as compared to bubbling or other methods of contact with a gas. The reaction in the case of atomized liquids takes place between the gas as continuous phase and the droplets of the atomized liquid as the discontinuous phase. Figures 7 and 8 illustrate some examples of atomized liquids 40 through liquid feed lines or atomizers 28. As aforementioned, other examples of liquid feed inlets are orifices which may produce 20 substantially linear streams of liquid, or spatter. Spatter is characterized by a course spray, wherein the average diameter of the droplets is larger than about 1/16".
The liquid feed inlets 28, if they are in the form of atomizers, may be stacked very close to each other, as better shown in Figure 9, and provide high concentration of droplets if the spray pattern is linear. A spray pattern is linear if the 25 atomizer produces a substantially linear pattern 42 on a flat substrate facing the atomizer 28, as better shown in Figure 10. Common shapes of patterns, in contrast with the substantially linear pattern 42, are circular or elliptical patterns 44, better shown in Figure 11. For the reasons stated above, the linear pattern atomizers are highlypreferable.
CA 0222~763 1997-12-23 The first reactant feed line 22 should most preferably be in the vicinity of the back end 16 of the reaction chamber 12. It can be over or under pool 34. It can also be part of one or more of sets 26 of inlet 28, or inlets 28, which are located toward the back end 16.
The gas feed line 24 can preferably be in the vicinity of the front end 14.
However, it can also be in the vicinity of the back end, or in any other place or places within the reaction chamber 12.
As aforementioned, the preferable cross-sections of the reaction chamber 12 are circular and triangular. For the same conditions, materials of construction, and cross-sectional area, the circular cross section provides higher strength than the triangular one. However, the triangular cross section provides higher density ofatomized droplets under the right atomization conditions, wherein the pattern of spray is linear. When a reaction chamber with a circular cross section is used, a preferred arrangement of the locations of liquid feed inlets 28 is illustrated in Figure 12, so that a lS plurality of triple liquid feed inlets 28 may be stacked closely to each other, as better illustrated in Figure 9.
An example of a reaction chamber having a triangular cross section is illustrated in Figure 13. Three substantially flat plates 46 are connected together by the bolts and nuts 48. Gaskets and other well known to the art features are not shown for purposes of brevity and clarity. Two or all three plates may be integrally connected. A
tube having a triangular configuration, for example, may be used. It is preferable, however, that at least one plate is removable for easy access, installation and maintenance of the liquid feed inlets, the baffles, and other accessories, which are not shown, such as for example thermocouples, pressure monitors, etc.
The operation of these embodiments, regardless of shape of cross section, arrangement or size of baffles, location and type of liquid feed inlets 28, and other variations, may be better explained by considering Figure 3.
Initially, first reactant, for example cyclohexane, contained in a liquid, for example acetic acid with catalyst and initiator, is caused to flow into the slightly 30 inclined reaction chamber 12 through the first reactant feed line 22. A pool 34, closest CA 0222~763 1997-12-23 to the first reactant feed line 22, starts being filled. After this pool 34 has been filled, it starts overflowing and liquid starts entering the second pool, next to it. This process repeats itself until all pools are full and overflowing, at which point the liquid is removed from the reaction chamber 12 through the liquid exit port 23 for further5 treatment. At the same time that this process of liquid movement is taking place from pool to pool in a direction substantially parallel to the axis X-X of the reaction chamber, re-circulating devices, such as for example pumps 36, remove liquid from a respective pool, and recirculate it to the reaction chamber 12 through a set 26 of liquid feed inlets 28, preferably in the form of an atomized liquid. The atomized droplets fall back to the 10 respective pools 34, and the recirculation continues. The direction of the falling droplets is substantially perpendicular to the axis X-X of the reaction chamber 12, while the overall movement of the liquid is from the back end to the front end of the reaction chamber 12, parallel to the axis X-X.
Simultaneously, a second reactant, for example oxygen, mixed in a gas, 15 for example nitrogen, or just oxygen, enters the reaction chamber 12 through gas feed line 24 and moves in a direction substantially parallel to the axis X-X of the reaction chamber 12. During this movement of the gas, the first reactant, for example cyclohexane, reacts with the second reactant, for example oxygen, to form a reaction product, for example adipic acid. The movement of the gas may be co-current with the 20 general movement of the liquid or counter-current, as it will be exemplified hereinbelow. The off-gases leave the system through valve 31 of condenser 30, while condensable matter returns to the reaction chamber 12, after it has been condensed in the condenser 30.
Temperatures, pressures, and other conditions regarding the reactor 10 25 depend on the particular reactants and reaction products, so that they are not specifically described here, as also being very well known to the art.
The concentration of second reactant is higher closer to the front end 14, and it decreases as the gas moves toward the back end 16, since second reactant is replenished at the front end 16, and since the conversion of the first reactant to reaction 30 product has been progressed considerably to a desired degree toward the front end.
CA 0222~763 1997-12-23 If all other conditions are the same, the lower the feed rate of first reactant through the first reactant feed line 22, the higher the conversion of first reactant to reaction product of liquid in the vicinity of the front end 14, provided that the reaction is slow enough. Of course, higher temperatures, and higher partial pressures of S the second reactant in the reaction chamber favor higher reaction rates, and therefore, conversions as the liquid moves from the back end 16 toward the front end 14.
This re-circulation arrangement allows the first reactant to move slowly in a controlled manner from the back end 16 to the front end 14, while it is continually or continuously, and controllably reacting during this movement with the second 10 reactant. Thus it performs in a manner similar to a plug flow reactor, having important added advantages. The first and second reactants according to the instant invention can have an independent inlet/outlet relation from any end to the opposite end, and most importantly, the reactor of the present invention can handle heterogeneous reactants, such as liquids with gases, in a plug flow manner, which is not possible with a 15 conventional plug flow reactor.
In the embodiment shown in Figure 4, the liquid from pool 34 passes through a filter 35 via re-circulation line 37, wherein solid products of l-eaction, such as for example adipic acid, terephthalic acid, etc., are removed from the liquid before it enters the liquid feed inlets 28. A cooler (not shown) in the recirculation line 37 20 between pool 34 and filter 35 is in many occasions beneficial as precipitating the product of reaction to a high degree. For example, in the case that the first reactant is cyclohexane and the reaction product is adipic acid, such a cooler may be desirable for precipitating the adipic acid before filtration. Two phases which may be formed during cooling may be separated, if so desired, and treated separately or together before they 25 are further pumped toward the set 26 of liquid feed inlets 28. A heater (not shown) after the filter 35 may be desirable to re-produce one phase from the two phases.
In another embodiment of the instant invention, the gas feed line 24 may be positioned under one or more pools 34, as better illustrated in Figure 14. In this case the gas not only comes in contact with the droplets above the pool, but it also bubbles CA 0222~763 1997-12-23 through the content of the pool, thus speeding up the reaction. In all other respects this embodiment is similar to the embodiments already discussed.
In still another embodiment, better shown in Figure lS, the reaction chamber is substantially horizontal, and each pump 36 re-circulates liquid from each 5 pool to a set 26 of liquid feed inlets 28, which are preferably atomizers above the same individual pool. The operation of this embodiment is substantially identical as the embodiments discussed above.
In still a different embodiment of the instant invention, better illustrated in Figure 16, each re-circulator pump 36, re-circulates the liquid through a respective 3-lO way valve 50 in a way that part of the liquid is dispensed, preferably atomized,immediately above the pool under consideration and part of the liquid is dispensed above a pool further away from the back end 16 and closer to the front end 14 (not shown in Figure 16, but shown in Figure 3). A combination of flow rate of liquidentering the reaction chamber 12 through first reactant feed line 22, and settings of 3-15 way valves 50, determines the conversion of first reactant to reaction product at thedifferent stages of the reaction chamber, all other parameters or conditions rem~ining constant.
In still another embodiment, better illustrated in Figure 17, a first section 52 of the reaction chamber 12 is temperature controlled to have a higher temperature 20 than a second section 54 by well known to the art techniques. The details regarding the liquid feed inlets, baffles, pools, etc., are not shown for purposes of clarity and brevity, and also since they have already been discussed in detail above. The purpose of this arrangement is to initiate a reaction, such as for example of cyclohexane to adipic acid, in section 52, and then continue the reaction at a lower temperature in second section 54 25 at a lower temperature, in order to improve selectivity and yield to final reaction product, for example adipic acid, without suffering from a long induction or initiation period. More than 2 sections similar to sections 52 and 54 may be utilized, and be operated at different temperatures. In other regards, the operation of this embodiment is substantially the same as discussed above regarding the other embodiments.
CA 0222~763 1997-12-23 In another embodiment, better shown in Figure 18, the reaction chamber 12 is separated in a back section 56 and a front section 58. In the vicinity of the back part 57 of the front section 56, there is located an additional inlet 60 for introducing other materials, such as for example other reactants, solvents, catalysts, initiators, or any 5 other desirable ingredients. More additional inlets at different desirable points and more than two section may be used depending on the particular circumstances. Thedifferent sections are adapted to attain different temperatures and operate under different conditions, so that one type of reaction may take place in one section and a different reaction in a different section. As in the previous case, details regarding the 10 liquid feed inlets, baffles, pools, etc., are not shown for purposes of clarity and brevity, and also since they have already been discussed in detail above.
The operation of this embodiment will be better understood if it is described in terms of a specific example. In this example, the purpose is to produce adipic acid from cyclohexane. Cyclohexane containing catalyst, such as a cobalt 15 compound for example, and a small amount of initiator, such as cyclohexanone for example, are fed to the back section 56 ofthe reaction chamber 12. The back section 56 is preferably kept at a temperature of 130 to 160~C. The mixture is atomized andrecirculated in this section as already has been described in the previous embodiments, and it progresses from the back point 16 of the reaction chamber 12 toward the back 20 point 57 of the front section 58. Oxygen, or a gas containing oxygen enters the gas feed line 24, which in this case is preferably located in the vicinity of the back end 16 of the reaction chamber 12. Acetic acid is introduced into the front section 58 of the reaction chamber 12 through additional inlet 60. The temperature of the front section 58 is preferably maintained in a range of 90 ~C to 120 ~C. The gas entering from the gas feed 25 line 24 and moving through the reaction chamber 12 in a direction from the back end 16 toward the front end 12 does not allow vapors of acetic acid to move to the back section 56 and condense therein. The liquid which is re-circulated from pools (similar to the ones described in the previous embodiments, but not shown for purposes of clarity) to respective liquid feed inlets (similar to the ones described in the previous embodiments, CA 0222~763 1997-12-23 but not shown for purposes of clarity), contains acetic acid as solvent within the front section 58.
These conditions favor the formation of cyclohexanone and cyclohexanol in the back section 56, while they also favor the formation of adipic acid 5 in the front section 58, from oxidation of an excess of cyclohexane which passes unreacted through the back section 56, and from oxidation of cyclohexanone, cyclohexanol and other adducts, which were formed in the back section 56. Thus, according to this embodiment of the instant invention, an adequate amount of initiator may be produced in a reaction chamber at a back section, while the final product may be 10 formed in the same reaction chamber in a front section.
The examples given above illustrate very clearly the versatility and adaptability of the reactor of the instant invention, wherein even more than one reaction may take place within a single reaction chamber in different sections of said reaction chamber in a highly controlled fashion.
A major advantage of the methods and devices of the present invention is that an outstanding balance between productivity and selectivity/yield of the desired product may be achieved. In this respect high yields and selectivities may be obtained without sacrificing productivity.
Another major advantage of this invention is that the conversion of first 20 reactant, for example cyclohexane, to reaction product, for example adipic acid, increases substantially uniformly along the length of the reaction chamber from the back end to the front end, and all the liquid reaching the front end, and exiting therefrom, has been subjected to the same treatment gradually. In the contrary, in the case of a stirred tank reactor, the exiting liquid contains completely unconverted first 25 reactant (which is being mixed substantially instantaneously with the rest of the liquid as it enters the stirred tank reactor), as well as reaction product which was formed and remained in the reactor for an excessively long time, so that the average conversion of first reactant to reaction product reaches an average conversion in the stirred tank reactor which is equivalent to the conversion level reached at the front end of the 30 reaction chamber of the present invention. In other words, the striking difference is that CA 0222~763 1997-12-23 in the case of the reaction chamber of this invention, and for all practical purposes, the molecules of first reactant and reaction product exiting the reaction chamber have been subjected to substantially the same treatment, while in the case of a stirred tank reactor, even some molecules of first reactant which just entered the reactor, exit, while other 5 molecules have been reacted at a considerably earlier time, in order to reach an average conversion which is equivalent to the conversion level reached at the front end of the reaction chamber of the present invention. This promotes substantially better selectivities and yields when the reaction is conducted according to the teachings of the present invention.
Reactions, such as oxidations for example, according to this invention, are non-destructive oxidations, wherein the oxidation product is different than carbon monoxide, carbon dioxide, and a mixture thereof. Of course, small amounts of these compounds may be formed along with the oxidation product, which may be one product or a mixture of products.
Examples include, but of course, are not limited to plepa~lion of C5-C,2 aliphatic dibasic acids from the corresponding saturated cycloaliphatic hydrocarbons, such as for example preparation of adipic acid from cyclohexane.
Regarding adipic acid, the preparation of which is especially suited to the methods and apparatuses of this invention, general information may be found in aplethora of U.S. Patents, among other references. These, include, but are not limited to:
U.S. Patents 2,223,493; 2,589,648; 2,285,914; 3,231,608; 3,234,271;
3,361,806; 3,390,174; 3,530,185; 3,649,685; 3,657,334; 3,957,876; 3,987,100;
U.S. Patent 5,374,767 (Drinkard et al) discloses formation of 30 cyclohexyladipates in a staged reactor, e.g, a reactive distillation column. A mixture CA 0222~763 1997-12-23 containing a major amount of benzene and a minor amount of cyclohexene is fed to the lower portion of the reaction zone and adipic acid is fed to the upper portion of the reaction zone, cyclohexyladipates are formed and removed from the lower portion of the reaction zone and benzene is removed from the upper portion of the reaction zone.
The reaction zone also contains an acid catalyst.
U.S. Patent 5,321,157 (Kollar) discloses a process for the preparation of C5- C8 aliphatic dibasic acids through oxidation of corresponding saturated cycloaliphatic hydrocarbons by (1) reacting, at a cycloaliphatic hydrocarbon conversion level of 10 between about 7% and about 30%, (a) at least one saturated cycloaliphatic hydrocarbon having from 5 to 8 ring carbon atoms in the liquid phase and (b) an excess of oxygen gas or an oxygen cont~ining gas mixture in the presence of (c) less than 1.5 moles of a solvent per mole of cycloaliphatic hydrocarbon (a), wherein said solvent comprises an organic acid containing only primary and/or secondary hydrogen atoms and (d) at least about 0.002 mole per 1000 grams of reaction mixture of a polyvalent heavy metal catalyst; and (2) isolating the C5 - C8 aliphatic dibasic acid.
U.S. Patent 5,221,800 (Park et al.) discloses a process for the manufacture of adipic acid is disclosed. In this process, cyclohexane is oxidized in an aliphatic monobasic acid solvent in the presence of a soluble cobalt salt wherein water is continuously or intermittently added to the reaction system after the initiation of 25 oxidation of cyclohexane as indicated by a suitable means of detection, and wherein the reaction is conducted at a temperature of about 50~C to about 150~C at an oxygen partial pressure of about 50 to 420 pounds per square inch absolute.
U.S. Patent 3,987,100 (Barnette et al.) describes a process of oxidizing cyclohexane to produce cyclohexanone and cyclohexanol, said process comprising 30 contacting a stream of liquid cyclohexane with oxygen in each of at least three CA 0222~763 1997-12-23 successive oxidation stages by introducing into each stage a mixture of gases comprising molecular oxygen and an inert gas.
U.S. Patent 3,957,876 (Rapoport et al.) describes a process for the preparation of cyclohexyl hydroperoxide substantially free of other peroxides by5 oxidation of cyclohexane containing a cyclohexane soluble cobalt salt in a zoned oxidation process in which an oxygen containing gas is fed to each zone in the oxidation section in an amount in excess of that which will react under the conditions of that zone.
U.S. Patent 3,932,513 (Russell) discloses the oxidation of cyclohexane 10 with molecular oxygen in a series of reaction zones, with vaporization of cyclohexane from the last reactor effluent and parallel distribution of this cyclohexane vapor among the series of reaction zones.
U.S. Patent 3,530,185 (Pugi) discloses a process for manufacturing precursors of adipic acid by oxidation with an oxygen-containing inert gas which15 process is conducted in at least three successive oxidation stages by passing a stream of liquid cyclohexane maintained at a temperature in the range of 140 ~C to 200 ~C and a pressure in the range of 50 to 350 p.s.i.g. through each successive oxidation stage and by introducing a mixture of gases containing oxygen in each oxidation stage in an amount such that substantially all of the oxygen introduced into each stage is consumed 20 in that stage thereafter causing the residual inert gases to pass countercurrent into the stream of liquid during the passage of the stream through said stages.
U.S. Patent 3,515,751 (Oberster et al.) discloses a process for the production of epsilon-hydroxycaproic acid in which cyclohexane is oxidized by liquid phase air oxidation in the presence of a catalytic amount of a lower aliphatic carboxylic 25 acid and a catalytic amount of a peroxide under certain reaction conditions so that most of the oxidation products are found in a second, heavy liquid layer, and are directed to the production of epsilon-hydroxycaproic acid.
U.S. Patent 3,361,806 (Lidov et al) discloses a process for the production of adipic acid by the further oxidation of the products of oxidation of cyclohexane after 30 separation of cyclohexane from the oxidation mixture, and more particularly to stage CA 0222~763 1997-12-23 wise oxidation of the cyclohexane to give high yields of adipic acid precursors and also to provide a low enough concentration of oxygen in the vent gas so that the latter is not a combustible mixture.
U.S. Patent 3,234,271 (Barker et al) discloses a process for the 5 production of adipic acid by the two-step oxidation of cyclohexane with oxygen. In a preferred embodiment, mixtures comprising cyclohexanone and cyclohexanol are oxidized. In another embodiment, the process involves the production of adipic acid from cyclohexane by oxidation thereof, separation of cyclohexane from the oxidation mixture and recycle thereof, and further oxidation of the other products of oxidation.
U.S. Patent 3,231,608 (Kollar) discloses a process for the preparation of aliphatic dibasic acids from saturated cyclic hydrocarbons having from 4 to 8 cyclic carbon atoms per molecule in the presence of a solvent which comprises an aliphatic monobasic acid which contains only primary and secondary hydrogen atoms and a catalyst comprising a cobalt salt of an organic acid, and in which process the molar ratio of said solvent to said saturated cyclic hydrocarbon is between 1.5:1 and 7:1, and in which process the molar ratio of said catalyst to said saturated cyclic hydrocarbon is at least 5 millimoles per mole.
U.S. Patent 3,161,603 (Leyshon et al) discloses a process for recovering the copper-vanadium catalyst from the waste liquors obtained in the manufacture of adipic acid by the nitric acid oxidation of cyclohexanol and/or cyclohexanone.
U.S. Patent 2,565,087 (Porter et al) discloses the oxidation of cycloaliphatic hydrocarbons in the liquid phase with a gas containing molecular oxygen and in the presence of about 10% water to produce two phases and avoid formation of esters.
U.S. Patent 2,557,282 (Hamblet et al) discloses production of adipic acid and related aliphatic dibasic acids; more particularly to the production of adipic acid by the direct oxidation of cyclohexane.
U.S. Patent 2,439,513 (Hamblet et al) discloses the production of adipic acid and related aliphatic dibasic acids and more particularly to the production of adipic acid by the oxidation of cyclohexane.
CA 0222~763 1997-12-23 U.S. Patent 2,223,494 (Loder et al) discloses the oxidation of cyclic saturated hydrocarbons and more particularly to the production of cyclic alcohols and cyclic ketones by oxidation of cyclic saturated hydrocarbons with an oxygen-containing gas.
5U.S. Patent 2,223,493 (Loder et al) discloses the production of aliphatic dibasic acids and more particularly to the production of aliphatic dibasic acids by oxidation of cyclic saturated hydrocarbons with an oxygen-containing gas.
German Patent DE 44 26 132 A 1 (Kysela et al.) discloses a method for dehydration of process acetic acid from the liquid-phase oxidation of cyclohexane with 10air, in the presence of cobalt salt as a catalyst after separation of the adipic acid by filtration and the cyclohexane phase by phase separation, while simultaneously avoiding cobalt salt precipitates in the dehydration column, characterized in that the acetic acid phase to be returned to the beginning of the process is subjected to azeotropic distillation by the use of added cyclohexane, under distillative removal of the water 15down to a residual content of less than about 0.3 to 0.7 wt %.
PCT Demand International publication WO 96/03365 (Costantini et al.) discloses a method of recycling a cobalt-cont~ining catalyst in a reaction involving the direct oxidation of cyclohexane into adipic acid using an oxygen containing gas. The method is characterized in that the reaction mixture, obtained in a preceding stage 20where the cyclohexane was oxidized into adipic acid, of which at least part of the intermediate oxidation products, such as cyclohexanol and cyclohexanone, the carboxylic acid and water has been separated and of which at least part of the adipic acid formed has been recovered by cryst~lli7~tion, undergoes at least one extraction operation using at least one cosolvent or a mixture comprising a cosolvent and a25carboxylic acid. The method is also characterized by the separation of a mixture containing at least part of the cobalt catalyst, part of the carboxylic acid and optionally residual quantities of other compounds and a solution containing the co-solvent and at least part of the glutaric and succinic acids formed during the oxidation reaction, and the carboxylic acid.
CA 0222~763 1997-12-23 The following references, among others, describe processes conducted in intermixing liquid with gaseous materials, mostly under increased surface area conditions.
U.S. Patent No. 5,399,750 (Brun et al.) discloses methods for preparing 5 maleamic acid (aminomaleic acid) by reacting gaseous ammonia with molten maleic anhydride under reactant contact conditions of high surface area, for example reacting said gaseous NH3 with a thin film of said molten maleic anhydride or with said molten maleic anhydride in a state of vigorous agitation.
U.S. Patent No. 5,396,850 (Connote et al.) discloses a method of 10 destroying organic waste in a bath of molten metal and slag contained in a vessel. The method comprises injecting organic waste into the bath to form a primary reaction zone in which the organic waste is thermally cracked and the products of the thermal cracking which are not absorbed into the bath are released into the space above the surface of the bath. The method further comprises injecting an oxygen-containing gas 15 toward the surface of the bath to form a secondary reaction zone in the space above the surface of the bath in which the oxidizable materials in the products from the primary reaction zone are completely oxidized and the heat released by such oxidation istransferred to the bath. In order to facilitate efficient heat transfer from the second reaction zone to the bath, the method further comprises injecting an inert or other 20 suitable gas into the bath to cause molten metal and slag to be ejected upwardly from the bath into the secondary reaction zone.
U.S. Patent No. 5,312,567 (Kozma et al.) discloses a complex mixing system with stages consisting of propeller mixers of high diameter ratio, where the blades are provided with flow modifying elements, whereby the energy proportions25 spent on dispersion of the amount of gas injected into the reactor, homogenization of the multi-phase mixtures, suspension of solid particles, etc. and the propertiescorresponding to the rheological properties of the gas-liquid mixtures and to the special requirements of the processes can be ensured even in extreme cases. Open channels opposite to the direction of rotation are on the blades of the dispersing stage of the 30 propeller mixers fixed to a common shaft, where the channels are interconnected with CA 0222~763 1997-12-23 gas inlet. The angle of incidence of a certain part of the blades of mixing stages used for homogenization and suspension is of opposite direction and the length is shorter and/or the angle of incidence is smaller than those of the other blades. Baffle bars are on the trailing end of the blades on a certain part of the propeller mixers used similarly for homogenization and suspension, and/or auxiliary blades at an angle of max. 20~ to the blade wings are arranged above or below the trailing end of the blades.
U.S. Patent No. 5,244,603 (Davis) discloses a gas-liquid mixing system which employs an impeller/draft tube assembly submerged in liquid. Hollow eductor tubes affixed to the impeller drive shaft are used to flow gas from an overhead gas space 10 to the liquid in the vicinity of the assembly. The positioning and size of the eductor tubes are such as to maximize the desired gas-liquid mixing and reaction rate.
U.S. Patent No. 5,270,019 (Melton et al.) discloses an elongated, generally vertically extending concurrent reactor vessel for the production of hypochlorous acid by the mixing and reaction of a liquid alkali metal hydroxide and a 15 gaseous halogen, wherein an atomizer is mounted near the top of the reactor vessel to atomize the liquid alkali metal hydroxide into droplets in the vessel. The vessel has a spraying and reaction zone immediately beneath the atomizer and a drying zone beneath the spraying and reaction zone to produce a gaseous hypochlorous acid and a substantially dry solid salt by-product.
U.S. Patent No. 5,170,727 (Nielsen) discloses a process and apparatus in which supercritical fluids are used as viscosity reduction diluents for liquid fuels or waste materials which are then spray atomized into a combustion chamber. The addition of supercritical fluid to the liquid fuel and/or waste material allows viscous petroleum fractions and other liquids such as viscous waste materials that are too 25 viscous to be atomized (or to be atomized well) to now be atomized by this invention by achieving viscosity reduction and allowing the fuel to produce a combustible spray and improved combustion efficiency. Moreover, the present invention also allows liquid fuels that have suitable viscosities to be better utilized as a fuel by achieving further viscosity reduction that improves atomization still further by reducing droplet size 30 which enhances evaporation of the fuel from the droplets.
CA 0222~763 1997-12-23 U.S. Patent No. 5,123,936 (Stone et al.) discloses a process and apparatus for removing fine particulate matter and vapors from a process exhaust air stream, and particularly those emitted during post-production curing or post-treatment of foamed plastics, such as polyurethane foam, in which the exhaust air stream is passed 5 through a transfer duct into which is introduced a water spray in the form of a mist of fine droplets in an amount which exceeds the saturation point; thereafter the exhaust air stream is introduced into a filter chamber having a cross-sectional area that issubstantially greater than that of the transfer duct, and the exhaust air stream passes through at least one, and preferably a plurality of high surface area filters, whereby a 10 portion of the water is removed from the exhaust air stream and collected in the filter chamber prior to the discharge of the exhaust air stream into the environment.
U.S. Patent No. 5,061,453 (Krippl et al.) discloses an apparatus for continuously charging a liquid reactant with a gas. The gas is dispersed in the reactant through a hollow stirrer in a gassing tank. The quantity of gas introduced per unit time 15 is kept constant.
U.S. Patent No. 4,423,018 (Lester, Jr. et al.) discloses a process according to which a by-product stream from the production of adipic acid from cyclohexane, containing glutaric acid, succinic acid and adipic acid, is employed as a buffer in lime or limestone flue gas scrubbing for the removal of sulfur dioxide from 20 combustion gases.
U.S. Patent No. 4,370,304 (Hendriks et al.) discloses methods by which ammonium orthophosphate products are prepared by reacting ammonia and phosphoricacid together at high speed under vigorous mixing conditions by spraying the reactants through a two-phase, dual coaxial mixer/sprayer and separately controlling the supply 25 and axial outflow rate of the phosphoric acid at 1 to 10 m/sec. and the outflow rate of ammonia at 200 to 1000 m/sec. (N.T.P.). Thorough mixing and a homogenous productis obtained by directing the outflow spray into a coaxial cylindrical reaction chamber of a specified size with respect to the diameter of the outermost duct of the sprayer/mixer.
The product may be granulated on a moving bed of granules and adjusted in respect of CA 0222~763 1997-12-23 the NH3 to H3PO4 content by ch~n~;ing the concentration of the phosphoric acid and/or supplying additional ammonia to the granulation bed.
U.S. Patent No. 4,361,965 (Goumondy et al.) discloses a device for atomizing a reaction mixture, said device enabling the reaction mixture to be atomized 5 in a reactor with the aid of at least a first gas and an atomizing nozzle. This device further comprises a supply of a second hot gas at the top of the atomizing device, serving to dry the atomized mixture, a supply of a third gas and means for distributing this third gas comprising an annular space of adjustable width and adapted to distribute in the reactor said third gas in the form of a ring along the inner wall of the reactor, so 10 as to avoid any contact between the reaction mixture and said wall. The invention is applicable to the atomization of a reaction mixture.
U.S. Patent No. 4,308,037 (Meissner et al.) discloses methods according to which high temperature thermal exchange between molten liquid and a gas stream is effected by generating in a confined flow passageway a plurality of droplets of molten 15 liquid and by passing a stream through the passageway in heat exchange relationship with the droplets. The droplets are recovered and adjusted to a predetermined temperature by means of thermal exchange with an external source for recycle. The process provides for removal of undesired solid, liquid or gaseous components.
U.S. Patent No. 4,065,527 (Graber) discloses an apparatus and a method 20 for handling a gas and a liquid in a manner to cause a specific interaction between them.
The gas is placed into circulation to cause it to make a liquid circulate in a vortex fashion to present a liquid curtain. The gas is then passed through the liquid curtain by angled vanes to cause the interaction between the two fluids, such as the heating of the liquid, scrubbing of the gas, adding a chemical to the liquid and the like. The vanes are 25 spaced apart and project inwardly from the inner periphery of an annular support so that the circulating liquid readily moves into the spaces between the vanes to create the liquid curtain. A number of embodiments of the invention are disclosed.
U.S. Patent No. 4,039,304 (Bechthold et al.) discloses methods according to which waste gas is contacted with a solution of a salt from a pollutant of 30 the gas. This solution is obtained from another stage of the process used for cleaning or CA 0222~763 1997-12-23 purifying the gas. The resulting mixture of gas and solution is subjected to vaporization so as to obtain a dry gaseous substance constituted by the waste gas and the evaporated solvent for the salt. The gaseous substance thus formed contains crystals of the salt as well as the pollutant present in the original waste gas. The salt crystals and other solid 5 particles are removed from the gaseous substance in the form of a dry solids mixture.
The gaseous substance is subsequently mixed with an absorption fluid such as an ammonia solution in order to wash out and redissolve any salt crystals which mayremain in the gaseous substance and in order to remove the pollutant present in the original waste gas from the gaseous substance. The pollutant and the redissolved salt 10 crystals form a salt solution together with the absorption fluid and it is this salt solution which is brought into contact with the waste gas. The gaseous substance is exhausted to the atmosphere after being mixed with the absorption fluid.
U.S. Patent No. 3,928,005 (Laslo) discloses a method and apparatus for treating gaseous pollutants such as sulfur dioxide in a gas stream which includes a wet 15 scrubber wherein a compressed gas is used to atomize the scrubbing liquid and a nozzle and the compressed gas direct the atomized liquid countercurrent to the flow of gas to be cleaned. The method and apparatus includes pneumatically conveying to the nozzle a material such as a solid particulate material which reacts with or modifies the pollutant to be removed or altered. The gas used for atomizing the scrubbing liquid is 20 also used as a transport vehicle for the solid particulate material. In the case of sulfur oxides, the material may be pulverized limestone.
U.S. Patent No. 3,677,696 (Bryk et al.) discloses a method according to which, the concentration of circulating sulfuric acid is adjusted to 80-98% by weight and used to wash hot gases cont~ining mercury. The temperature of the acid is 25 m~int~ined between 70-250~C, and the solid material separating from the circulating wash solution is recovered.
U.S. Patent No. 3,613,333 (Gardenier) discloses a process and apparatus for removing cont:~min~nts from and pumping a gas stream comprising indirectly heat exch~nging the gas and a liquid, introducing the liquid under conditions of elevated 30 temperature and pressure in vaporized and atomized form into the gas, mixing same CA 0222~763 1997-12-23 thereby entrapping the cont:~min~nts, and separating clean gas from the atomized liquid containing the cont~min~nts.
U.S. Patent No. 2,980,523 (Dille et al.) discloses a process for the production of carbon monoxide and hydrogen from carbonaceous fuels by reaction with 5 oxygen. In one of its more specific aspects it is directed to a method of separating carbonaceous solid entrained in the gaseous products of reaction of carbonaceous fuels and oxygen wherein said products are contacted with a limited amount of liquid hydrocarbon and thereafter scrubbed with water, and said carbonaceous solid is decanted from said clarified water.
U.S. Patent No. 2,301,240 (Ba-lm~nn et al.) discloses an improved process for removing impurities from acetylene gas which has been prepared by thermal or electrical methods by washing with organic liquids, as for example oils or tars.
U.S. Patent No. 2,014,044 (Haswell) discloses an improved method for treating gas and aims to provide for the conservation of the sensible heat of such gas.
U.S. Patent No. 1,121,532 (Newberry) discloses a process of recovering alkalis from flue-gases.
None of the above references, or any other references known to the inventors disclose, suggest or imply, singly or in combination, oxidation of cyclic hydrocarbons to dibasic acids in multiple stages of temperature/conversion, subject to 20 the intricate and critical controls and requirements of the instant invention as described and claimed.
Our U.S. Patents 5,580,531, 5,558,842, 5,502,245, and our co-pending applications 08/477,195 (filed 06/07/95), 08/587,967 (filed 01/17/96), and 08/620,974 (filed 03/25/96), all of which are incorporated herein by reference, describe methods 25 and apparatuses relative to controlling reactions in atomized liquids.
Our co-pending U.S. Patent Application No. 08/812,847 of Mark W.
Dassel, Eustathios Vassiliou, David C. DeCoster, Ader M. Rostami, and Sharon M.
Aldrich, titled "Methods and Devices for Controlling the Reaction Rate of a Hydrocarbon to an Acid by Making Phase-related Adjustments", filed on March 6, 30 1997, is also incorporated herein by reference.
CA 0222~763 1997-12-23 Our co-pending U.S. Patent Application No. 08/824,992 of Mark W.
Dassel, David C. DeCoster, Ader M. Rostami, Sharon M. Aldrich, and Eustathios Vassiliou, titled "Methods and Devices for Preparing Dibasic Acids", filed on March 27, 1997, is also incorporated herein by reference.
All of the following patent applications, each of which was filed on May 21, 1997 are also incorporated herein by reference:
U.S. Patent Application No. 08/859,985 of Eustathios Vassiliou, Mark W. Dassel, David C. DeCoster, Ader M. Rostami, and Sharon M. Aldrich, titled "Methods and Devices for Controlling the Reaction Rate of a Hydrocarbon to an 10 Intermediate Oxidation Product by Pressure Drop Adjustments";
U.S. Patent Application No. 08/861,281 of Mark W. Dassel, Eustathios Vassiliou, David C. DeCoster, Ader M. Rostami, and Sharon M. Aldrich, titled "Methods and Devices for Controlling the Reaction Rate of a Hydrocarbon to an Intermediate Oxidation Product by Monitoring Flow of Incoming and Outcoming 15 Gases";
U.S. Patent Application No. 08/861,180 of David C. DeCoster, Ader M.
Rostami, Mark W. Dassel, and Eustathios Vassiliou, titled "Methods and Devices for Controlling the Oxidation Rate of a Hydrocarbon by Adjusting the Ratio of the Hydrocarbon to a Rate-Modulator";
U.S. Patent Application No. 08/861,176 of Mark W. Dassel, Eustathios Vassiliou, David C. DeCoster, and Ader M. Rostami, titled "Methods of Preparing an Intermediate Oxidation Product from a Hydrocarbon by Utilizing an Activated Initiator"; and U.S. Patent Application No. 08/859,890 of Ader M. Rostami, Mark W.
25 Dassel, Eustathios Vassiliou, David C. DeCoster, titled "Methods and Devices for Controlling the Oxidation of a Hydrocarbon to an Acid by Regulating Temperature/Conversion Relationship in Multi-Stage Arrangements."
SUMMARY OF THE INVENTION
As aforementioned, this invention relates to reactors behaving in a similar manner as plug-flow reactors. More particularly, the instant invention relates to CA 0222~763 1997-12-23 a reactor comprising a reaction chamber having an elongate body, a liquid feed side, a coalescing side, a front end, a back end, a cross section, a length, a width, and an axis, the reactor comprising:
a first reactant feed line for introducing a first reactant to the reactor, the first reactant being non-gaseous;
a plurality of liquid-feed inlets at the liquid feed side of the reactor, the liquid-feed inlets being adapted to feed a liquid in a direction substantially perpendicular to the direction of the axis, and in a manner that the liquid changes direction from substantially perpendicular to substantially parallel to the direction of the 10 axis at the coalescing side of the reactor;
a gas feed line adapted to feed a gas containing a second reactant to the reactor; and reaction-inducing means for causing a reaction to take place between the first reactant and the second reactant to form a reaction product, in at least a portion of 15 the reaction chamber. Examples of such means are temperature and/or pressure control means, such as for example heaters, coolers, compressors, etc., preferably accompanied by monitoring equipment, etc., all well known to the art.
It is highly preferable that at least one of the plurality of the liquid-feed inlets may comprise an atomizer for atomizing the liquid in a form of a pattern, which is 20 preferably linear. However, at least one of the plurality of the liquid-feed inlets may comprise an orifice adapted to form streams of liquid, and/or a spatter producing mech~ni .~m .
The cross-section of the reaction chamber may have any shape, but it is preferably circular, and more preferably triangular.
Also preferably, the gas feed line is located in the vicinity of the front end of the reaction chamber and the first reactant feed line is in the vicinity of the back end of the reaction chamber.
It is preferable that the reaction chamber further comprises restrictive baffles forming pools at the coalescing side of said reaction chamber. The reactor may CA 0222~763 1997-12-23 also preferably comprise a re-circulator for transferring liquid from the coalescing side to predeterrnined liquid feed inlets.
The predetermined liquid feed inlets, the feed of which originates from a given pool, may preferably be located between the pool and the front end, or above the pool, while the gas feed line may be also located under said pool.
It is preferable that at least two of the pools have different capacities, more preferable that pools toward the front end have higher capacities than pools toward the back end, and even more preferable that the pools have progressively larger capacities going from the back end toward the front end of the reaction chamber.10 Degree of inclination of the reaction chamber, different heights of baffles or different distances between consecutive baffles are examples of ways to modify the capacities of the pools.
The ratio of the length of the reaction chamber to the width of said reaction chamber is preferably higher than 10. The reaction chamber may be inclined or 15 it may be substantially horizontal. Means for adjusting the degree of inclination of the reaction chamber may also be provided. Such means may be for example hydraulic or other types of lifters, well known to the art, which may adjust one or both ends of the reaction chamber, thus ch~n~;ing the degree of inclination of the reaction chamber. In addition, one or both ends of the reaction chamber may be pivoted.
The reaction chamber may be divided into different sections adapted to operate under different conditions. The reactor may comprise additional inlets in at least one of the different sections, for introducing matter ch~nging reaction characteristics in the at least one of the different sections. The reaction chamber may further comprise means for removing reaction product between at least one pool and the 25 respective liquid feed inlet. Also, by-products such as water for example, or recyclable products, may be removed in a similar manner.
BRIEF DESCRIPTION OF THE DRAWING
The reader's understanding of this invention will be enhanced by 30 reference to the following detailed description taken in combination with the drawing figures, wherein:
CA 0222~763 1997-12-23 FIGURES 1 A, I B, AND 1 C illustrate schematically examples of miscellaneous general configurations of the reactors according to the present invention.
FIGURES 2A through 2E illustrate schematically examples of miscellaneous general cross sections of the reaction chambers according to the present invention.
FIGURE 3 illustrates schematically an inclined reactor according to a preferred embodiment of the present invention wherein liquids are recirculated from pools to sets of liquid feed inlets.
FIGURE 4 illustrates schematically a fragmented view of another 10 preferred embodiment of the present invention, wherein a filter is used in the re-circulation line.
FIGURES 5 and 6 illustrate schematically examples of segments of the reaction chamber according to a preferred embodiment of the present invention.
FIGURES 7 and 8 illustrate schematically examples of atomized liquids 15 through liquid feed lines or atomizers.
FIGURE 9 illustrates schematically a fragmented view of a reaction chamber according to another preferred embodiment of the instant invention, wherein the liquid feed inlets in the form of atomizers are stacked very close to each other in order to provide high concentration of droplets in linear spray patterns.
FIGURE 10 illustrates schematically a linear spray pattern.
FIGURE 11 illustrates schematically a circular or elliptical spray pattern.
FIGURE 12 illustrates schematically a reaction chamber with a circular cross section having triple feed inlets in order to maximize the density of liquid droplets after the triple inlets have been stacked as illustrated in the reaction chamber of Figure 25 9.
FIGURE 13 illustrates schematically a reaction chamber having a triangular cross section, wherein three substantially flat plates are connected together.
FIGURE 14 illustrates schematically a fragmented view of a reaction chamber according to another preferred embodiment of the instant invention, wherein 30 the gas feed line is positioned under a pool.
CA 0222~763 l997-l2-23 FIGURE 15 illustrates schematically a horizontal reaction chamber according to another preferred embodiment of the instant invention.
FIGURE 16 illustrates schematically a horizontal reaction chamber according to another preferred embodiment of the instant invention, wherein each re-5 circulator pump, re-circulates the liquid through a respective 3-way valve in a way that part of the liquid is dispensed, preferably atomized, immediately above the pool under consideration and part of the liquid is dispensed above a pool further away from the back end and closer to the front end of the reaction chamber.
FIGURE 17 illustrates schematically a reaction chamber according to 10 another preferred embodiment of the instant invention, wherein a first section of the reaction chamber is controlled to have a higher temperature than a second section.
FIGURE 18 illustrates schematically a reaction chamber according to another preferred embodiment of the instant invention, wherein the reaction chamber is separated in a back section and a front section, as well as an additional inlet for 15 introducing other desirable ingredients.
DETAILED DESCRIPTION OF THE INVENTION
As aforementioned, this invention relates to reactors behaving in a similar manner as plug-flow reactors. The reactor of the instant invention is very useful 20 in most cases wherein one reactant is a liquid or a substance contained in a liquid and the other reactant is a gas, or a substance contained in a gas. Examples include but are not limited to formation of maleamic acid, formation of ammonium phosphate, etc., wherein one reactant is in the liquid state and the other reactant is in the gaseous state.
This invention is particularly fit for oxidations, such as for example oxidation of 25 cyclohexane to cyclohexanone and/or cyclohexanol, and/or cyclohexyhydroperoxide, and/or adipic acid, oxidation of cyclohexanone and/or cyclohexanol to cyclohexylhydroperoxide, and/or adipic acid, oxidation of cyclohexylhydroperoxide to adipic acid, oxidation of toluene to benzoic acid, oxidation of o-xylene to phthalic acid, oxidation of m-xylene to isophthalic acid, oxidation of p-xylene to terephthalic acid, 30 etc.
CA 0222~763 1997-12-23 The reactor 10, as better illustrated in Figures lA to lC, comprises a reaction chamber 12, which in turn comprises an elongated body 13, a front end 14, a back end 16, a length L, a width W, and an axis X. The ratio of the length L to the width W is preferably larger than 10 The general shape of the reactor l O of this invention may have any of a plurality of configurations. In one example, illustrated in Figure lA, the general shape of the reactor l O has the form of a coil. In another example, illustrated in Figure 1 B, the general shape of the reactor 10 has the form of two inclined straight segments connected together. In still another example, illustrated in Figure lC, the general shape of the 10 reactor lO has the form of a single inclined segment. The reactor lO, may also be substantially horizontal, as will be illustrated at a later point.
The inclination of the reaction chamber 12 is preferably lower than 45 degrees and more preferably in the range of 5 to 20 degrees. The reaction chamber 12 may also be substantially horizontal.
Means for adjusting the degree of inclination (not shown) of the reaction chamber 12 may also be provided. Such means may be for example hydraulic lifters or other types of lifters, well known to the art, which may adjust one or both ends of the reaction chamber, thus ch:~nging the degree of inclination of the reaction chamber. In addition, one or both ends of the reaction chamber may be pivoted.
The cross-sections of the different segments of the reactor 10 may have different shapes. Examples of some of the most common cross-sections are illustrated in Figures 2A through 2E. The most preferred cross-sections, for reasons to be explained later are a circular cross-section illustrated in Figure 2A, and a triangular cross-section illustrated in Figure 2D.
The reaction chamber 12, as better illustrated in Figure 3, also has preferably a liquid feed side 18, a coalescing side 20, a first reactant feed line 22, a liquid exit port 23, a gas feed line 24, sets 26 of liquid feed inlets 28, each set 26 cont~ining one or more liquid feed inlets 28, and a condenser 30, provided with a valve 31, for condensing condensables and allowing off-gases to be moved out of the system.
30 Preferably, a demister (not shown), well known to the art, may be placed between the CA 0222~763 1997-12-23 reaction chamber 12 and the condenser 30. It is preferable that that the reaction chamber 12 has baffles 32, which form pools 34 in the coalescing side 20. The pools 34 are adapted to restrict liquid matter from free flowing from the back end 16 to the front end 18 of the reaction chamber 12. In many occasions, it is preferable that at least two 5 pools have different capacities, more preferable that the pools toward the front end 14 are larger or have larger capacities than the pools toward the back end 16, and it is even more preferable that the pools have progressively higher capacities going from the back end 16 toward the front end 14. One of the reasons why is that the reaction rate usually decreases as the reaction progresses, and the reaction progresses in the reaction chamber 10 12 as the liquid moves from the back end 16 to the front end 14.
The reactor 10, may also comprise a re-circulator, in the form of a pump 36 for example, which is adapted to re-circulate liquid matter from the pools 34 to predetermined inlets 28 or sets of inlets 26. A filter 35 may be used in the re-circulator line 37 for removing precipitated matter, such as adipic acid for example in the case of 15 oxidation of cyclohexane to adipic acid, as better shown in Figure 4. A cooler (not shown) may be used between the pool and the filter 35 to promote precipitation and to remove heat of reaction. Also, a heat exchanger (not shown), preferably a heater, may be used after the filter and before the liquid feed inlets 28 to raise the temperature adequately for the reaction to proceed, and ensure solubilization of any precipitate that 20 might form after the filter.
Filters in the re-circulation lines are preferably employed in pools located after the reaction has progressed adequately to filter out the product of reaction, adipic acid for example. In this particular case, at the early stages, no filters are necessary. In order to remove the heat of reaction at the early stages and in the absence 25 of a filter, a cooler may be used in such a manner that the temperature does not decrease to a point that reaction cannot proceed and/or to the point that reaction product, adipic acid for example, is precipitated. In addition, it may be prudent to m~int~in the temperature of the heat exchanger cooling fluid at a higher temperature than thetemperature of precipitation of any solids dissolved, to avoid deposition of solids on the 30 heat exchanger surfaces.
CA 0222~763 1997-12-23 The re-circulation line may also be divided in one stream of lower temperature and one stream of higher temperature, the two streams being fed through different atomizers in the same vicinity. As explained in more detail in our co-pending application Serial Number 08/587,967, filed 01/17/96, which is incorporated herein by 5 reference, the heat produced by the reaction in the higher temperature droplets is removed by evaporation of volatile matter, which matter condenses on the lower temperature droplets.
A jacket around the reaction chamber may also be used for removing heat of reaction by recirculating cooling liquids through the jacket.
Exemplary segments of the reaction chamber 12 are better illustrated in Figures 5 and 6. A plurality of segments as shown in Figure 5 may be connected together through flanges 38.
Preferably, the liquid feed inlets 28 comprise or are in the form of atomizers. Atomized liquids have the advantage of providing an extremely high surface 15 area, as compared to bubbling or other methods of contact with a gas. The reaction in the case of atomized liquids takes place between the gas as continuous phase and the droplets of the atomized liquid as the discontinuous phase. Figures 7 and 8 illustrate some examples of atomized liquids 40 through liquid feed lines or atomizers 28. As aforementioned, other examples of liquid feed inlets are orifices which may produce 20 substantially linear streams of liquid, or spatter. Spatter is characterized by a course spray, wherein the average diameter of the droplets is larger than about 1/16".
The liquid feed inlets 28, if they are in the form of atomizers, may be stacked very close to each other, as better shown in Figure 9, and provide high concentration of droplets if the spray pattern is linear. A spray pattern is linear if the 25 atomizer produces a substantially linear pattern 42 on a flat substrate facing the atomizer 28, as better shown in Figure 10. Common shapes of patterns, in contrast with the substantially linear pattern 42, are circular or elliptical patterns 44, better shown in Figure 11. For the reasons stated above, the linear pattern atomizers are highlypreferable.
CA 0222~763 1997-12-23 The first reactant feed line 22 should most preferably be in the vicinity of the back end 16 of the reaction chamber 12. It can be over or under pool 34. It can also be part of one or more of sets 26 of inlet 28, or inlets 28, which are located toward the back end 16.
The gas feed line 24 can preferably be in the vicinity of the front end 14.
However, it can also be in the vicinity of the back end, or in any other place or places within the reaction chamber 12.
As aforementioned, the preferable cross-sections of the reaction chamber 12 are circular and triangular. For the same conditions, materials of construction, and cross-sectional area, the circular cross section provides higher strength than the triangular one. However, the triangular cross section provides higher density ofatomized droplets under the right atomization conditions, wherein the pattern of spray is linear. When a reaction chamber with a circular cross section is used, a preferred arrangement of the locations of liquid feed inlets 28 is illustrated in Figure 12, so that a lS plurality of triple liquid feed inlets 28 may be stacked closely to each other, as better illustrated in Figure 9.
An example of a reaction chamber having a triangular cross section is illustrated in Figure 13. Three substantially flat plates 46 are connected together by the bolts and nuts 48. Gaskets and other well known to the art features are not shown for purposes of brevity and clarity. Two or all three plates may be integrally connected. A
tube having a triangular configuration, for example, may be used. It is preferable, however, that at least one plate is removable for easy access, installation and maintenance of the liquid feed inlets, the baffles, and other accessories, which are not shown, such as for example thermocouples, pressure monitors, etc.
The operation of these embodiments, regardless of shape of cross section, arrangement or size of baffles, location and type of liquid feed inlets 28, and other variations, may be better explained by considering Figure 3.
Initially, first reactant, for example cyclohexane, contained in a liquid, for example acetic acid with catalyst and initiator, is caused to flow into the slightly 30 inclined reaction chamber 12 through the first reactant feed line 22. A pool 34, closest CA 0222~763 1997-12-23 to the first reactant feed line 22, starts being filled. After this pool 34 has been filled, it starts overflowing and liquid starts entering the second pool, next to it. This process repeats itself until all pools are full and overflowing, at which point the liquid is removed from the reaction chamber 12 through the liquid exit port 23 for further5 treatment. At the same time that this process of liquid movement is taking place from pool to pool in a direction substantially parallel to the axis X-X of the reaction chamber, re-circulating devices, such as for example pumps 36, remove liquid from a respective pool, and recirculate it to the reaction chamber 12 through a set 26 of liquid feed inlets 28, preferably in the form of an atomized liquid. The atomized droplets fall back to the 10 respective pools 34, and the recirculation continues. The direction of the falling droplets is substantially perpendicular to the axis X-X of the reaction chamber 12, while the overall movement of the liquid is from the back end to the front end of the reaction chamber 12, parallel to the axis X-X.
Simultaneously, a second reactant, for example oxygen, mixed in a gas, 15 for example nitrogen, or just oxygen, enters the reaction chamber 12 through gas feed line 24 and moves in a direction substantially parallel to the axis X-X of the reaction chamber 12. During this movement of the gas, the first reactant, for example cyclohexane, reacts with the second reactant, for example oxygen, to form a reaction product, for example adipic acid. The movement of the gas may be co-current with the 20 general movement of the liquid or counter-current, as it will be exemplified hereinbelow. The off-gases leave the system through valve 31 of condenser 30, while condensable matter returns to the reaction chamber 12, after it has been condensed in the condenser 30.
Temperatures, pressures, and other conditions regarding the reactor 10 25 depend on the particular reactants and reaction products, so that they are not specifically described here, as also being very well known to the art.
The concentration of second reactant is higher closer to the front end 14, and it decreases as the gas moves toward the back end 16, since second reactant is replenished at the front end 16, and since the conversion of the first reactant to reaction 30 product has been progressed considerably to a desired degree toward the front end.
CA 0222~763 1997-12-23 If all other conditions are the same, the lower the feed rate of first reactant through the first reactant feed line 22, the higher the conversion of first reactant to reaction product of liquid in the vicinity of the front end 14, provided that the reaction is slow enough. Of course, higher temperatures, and higher partial pressures of S the second reactant in the reaction chamber favor higher reaction rates, and therefore, conversions as the liquid moves from the back end 16 toward the front end 14.
This re-circulation arrangement allows the first reactant to move slowly in a controlled manner from the back end 16 to the front end 14, while it is continually or continuously, and controllably reacting during this movement with the second 10 reactant. Thus it performs in a manner similar to a plug flow reactor, having important added advantages. The first and second reactants according to the instant invention can have an independent inlet/outlet relation from any end to the opposite end, and most importantly, the reactor of the present invention can handle heterogeneous reactants, such as liquids with gases, in a plug flow manner, which is not possible with a 15 conventional plug flow reactor.
In the embodiment shown in Figure 4, the liquid from pool 34 passes through a filter 35 via re-circulation line 37, wherein solid products of l-eaction, such as for example adipic acid, terephthalic acid, etc., are removed from the liquid before it enters the liquid feed inlets 28. A cooler (not shown) in the recirculation line 37 20 between pool 34 and filter 35 is in many occasions beneficial as precipitating the product of reaction to a high degree. For example, in the case that the first reactant is cyclohexane and the reaction product is adipic acid, such a cooler may be desirable for precipitating the adipic acid before filtration. Two phases which may be formed during cooling may be separated, if so desired, and treated separately or together before they 25 are further pumped toward the set 26 of liquid feed inlets 28. A heater (not shown) after the filter 35 may be desirable to re-produce one phase from the two phases.
In another embodiment of the instant invention, the gas feed line 24 may be positioned under one or more pools 34, as better illustrated in Figure 14. In this case the gas not only comes in contact with the droplets above the pool, but it also bubbles CA 0222~763 1997-12-23 through the content of the pool, thus speeding up the reaction. In all other respects this embodiment is similar to the embodiments already discussed.
In still another embodiment, better shown in Figure lS, the reaction chamber is substantially horizontal, and each pump 36 re-circulates liquid from each 5 pool to a set 26 of liquid feed inlets 28, which are preferably atomizers above the same individual pool. The operation of this embodiment is substantially identical as the embodiments discussed above.
In still a different embodiment of the instant invention, better illustrated in Figure 16, each re-circulator pump 36, re-circulates the liquid through a respective 3-lO way valve 50 in a way that part of the liquid is dispensed, preferably atomized,immediately above the pool under consideration and part of the liquid is dispensed above a pool further away from the back end 16 and closer to the front end 14 (not shown in Figure 16, but shown in Figure 3). A combination of flow rate of liquidentering the reaction chamber 12 through first reactant feed line 22, and settings of 3-15 way valves 50, determines the conversion of first reactant to reaction product at thedifferent stages of the reaction chamber, all other parameters or conditions rem~ining constant.
In still another embodiment, better illustrated in Figure 17, a first section 52 of the reaction chamber 12 is temperature controlled to have a higher temperature 20 than a second section 54 by well known to the art techniques. The details regarding the liquid feed inlets, baffles, pools, etc., are not shown for purposes of clarity and brevity, and also since they have already been discussed in detail above. The purpose of this arrangement is to initiate a reaction, such as for example of cyclohexane to adipic acid, in section 52, and then continue the reaction at a lower temperature in second section 54 25 at a lower temperature, in order to improve selectivity and yield to final reaction product, for example adipic acid, without suffering from a long induction or initiation period. More than 2 sections similar to sections 52 and 54 may be utilized, and be operated at different temperatures. In other regards, the operation of this embodiment is substantially the same as discussed above regarding the other embodiments.
CA 0222~763 1997-12-23 In another embodiment, better shown in Figure 18, the reaction chamber 12 is separated in a back section 56 and a front section 58. In the vicinity of the back part 57 of the front section 56, there is located an additional inlet 60 for introducing other materials, such as for example other reactants, solvents, catalysts, initiators, or any 5 other desirable ingredients. More additional inlets at different desirable points and more than two section may be used depending on the particular circumstances. Thedifferent sections are adapted to attain different temperatures and operate under different conditions, so that one type of reaction may take place in one section and a different reaction in a different section. As in the previous case, details regarding the 10 liquid feed inlets, baffles, pools, etc., are not shown for purposes of clarity and brevity, and also since they have already been discussed in detail above.
The operation of this embodiment will be better understood if it is described in terms of a specific example. In this example, the purpose is to produce adipic acid from cyclohexane. Cyclohexane containing catalyst, such as a cobalt 15 compound for example, and a small amount of initiator, such as cyclohexanone for example, are fed to the back section 56 ofthe reaction chamber 12. The back section 56 is preferably kept at a temperature of 130 to 160~C. The mixture is atomized andrecirculated in this section as already has been described in the previous embodiments, and it progresses from the back point 16 of the reaction chamber 12 toward the back 20 point 57 of the front section 58. Oxygen, or a gas containing oxygen enters the gas feed line 24, which in this case is preferably located in the vicinity of the back end 16 of the reaction chamber 12. Acetic acid is introduced into the front section 58 of the reaction chamber 12 through additional inlet 60. The temperature of the front section 58 is preferably maintained in a range of 90 ~C to 120 ~C. The gas entering from the gas feed 25 line 24 and moving through the reaction chamber 12 in a direction from the back end 16 toward the front end 12 does not allow vapors of acetic acid to move to the back section 56 and condense therein. The liquid which is re-circulated from pools (similar to the ones described in the previous embodiments, but not shown for purposes of clarity) to respective liquid feed inlets (similar to the ones described in the previous embodiments, CA 0222~763 1997-12-23 but not shown for purposes of clarity), contains acetic acid as solvent within the front section 58.
These conditions favor the formation of cyclohexanone and cyclohexanol in the back section 56, while they also favor the formation of adipic acid 5 in the front section 58, from oxidation of an excess of cyclohexane which passes unreacted through the back section 56, and from oxidation of cyclohexanone, cyclohexanol and other adducts, which were formed in the back section 56. Thus, according to this embodiment of the instant invention, an adequate amount of initiator may be produced in a reaction chamber at a back section, while the final product may be 10 formed in the same reaction chamber in a front section.
The examples given above illustrate very clearly the versatility and adaptability of the reactor of the instant invention, wherein even more than one reaction may take place within a single reaction chamber in different sections of said reaction chamber in a highly controlled fashion.
A major advantage of the methods and devices of the present invention is that an outstanding balance between productivity and selectivity/yield of the desired product may be achieved. In this respect high yields and selectivities may be obtained without sacrificing productivity.
Another major advantage of this invention is that the conversion of first 20 reactant, for example cyclohexane, to reaction product, for example adipic acid, increases substantially uniformly along the length of the reaction chamber from the back end to the front end, and all the liquid reaching the front end, and exiting therefrom, has been subjected to the same treatment gradually. In the contrary, in the case of a stirred tank reactor, the exiting liquid contains completely unconverted first 25 reactant (which is being mixed substantially instantaneously with the rest of the liquid as it enters the stirred tank reactor), as well as reaction product which was formed and remained in the reactor for an excessively long time, so that the average conversion of first reactant to reaction product reaches an average conversion in the stirred tank reactor which is equivalent to the conversion level reached at the front end of the 30 reaction chamber of the present invention. In other words, the striking difference is that CA 0222~763 1997-12-23 in the case of the reaction chamber of this invention, and for all practical purposes, the molecules of first reactant and reaction product exiting the reaction chamber have been subjected to substantially the same treatment, while in the case of a stirred tank reactor, even some molecules of first reactant which just entered the reactor, exit, while other 5 molecules have been reacted at a considerably earlier time, in order to reach an average conversion which is equivalent to the conversion level reached at the front end of the reaction chamber of the present invention. This promotes substantially better selectivities and yields when the reaction is conducted according to the teachings of the present invention.
Reactions, such as oxidations for example, according to this invention, are non-destructive oxidations, wherein the oxidation product is different than carbon monoxide, carbon dioxide, and a mixture thereof. Of course, small amounts of these compounds may be formed along with the oxidation product, which may be one product or a mixture of products.
Examples include, but of course, are not limited to plepa~lion of C5-C,2 aliphatic dibasic acids from the corresponding saturated cycloaliphatic hydrocarbons, such as for example preparation of adipic acid from cyclohexane.
Regarding adipic acid, the preparation of which is especially suited to the methods and apparatuses of this invention, general information may be found in aplethora of U.S. Patents, among other references. These, include, but are not limited to:
U.S. Patents 2,223,493; 2,589,648; 2,285,914; 3,231,608; 3,234,271;
3,361,806; 3,390,174; 3,530,185; 3,649,685; 3,657,334; 3,957,876; 3,987,100;
4,032,569; 4,105,856; 4,158,739 (glutaric acid); 4,263,453; 4,331,608; 4,606,863;
4,902,827; 5,221,800; and 5,321,157.
Examples demonstrating the operation of the instant invention have been given for illustration purposes only, and should not be construed as limiting the scope of this invention in any way. In addition it should be stressed that the preferred embodiments discussed in detail hereinabove, as well as any other embodiments encompassed within the limits of the instant invention, may be practiced individually, or in any combination thereof, according to common sense and/or expert opinion.
CA 0222~763 1997-12-23 Individual sections of the embodiments may also be practiced individually or in combination with other individual sections of embodiments or embodiments in their totality, according to the present invention. These combinations also lie within the realm of the present invention. Furthermore, any attempted explanations in the 5 discussion are only speculative and are not intended to narrow the limits of this nventlon.
All explanations given hereinabove are to be considered as speculative and should not be construed as limiting the breadth of the claims.
4,902,827; 5,221,800; and 5,321,157.
Examples demonstrating the operation of the instant invention have been given for illustration purposes only, and should not be construed as limiting the scope of this invention in any way. In addition it should be stressed that the preferred embodiments discussed in detail hereinabove, as well as any other embodiments encompassed within the limits of the instant invention, may be practiced individually, or in any combination thereof, according to common sense and/or expert opinion.
CA 0222~763 1997-12-23 Individual sections of the embodiments may also be practiced individually or in combination with other individual sections of embodiments or embodiments in their totality, according to the present invention. These combinations also lie within the realm of the present invention. Furthermore, any attempted explanations in the 5 discussion are only speculative and are not intended to narrow the limits of this nventlon.
All explanations given hereinabove are to be considered as speculative and should not be construed as limiting the breadth of the claims.
Claims (29)
1. A reactor comprising a reaction chamber having an elongated body, a liquid feed side, a coalescing side, a front end, a back end, a cross section, a length, a width, and an axis, the reactor comprising:
a first reactant feed line for introducing a first reactant to the reaction chamber, the first reactant being non-gaseous;
a plurality of liquid feed inlets at the liquid feed side of the reaction chamber, the liquid-feed inlets being adapted to feed a liquid in a direction substantially perpendicular to the direction of the axis, and in a manner that the liquid changes direction from substantially perpendicular to substantially parallel to the direction of the axis at the coalescing side of the reactor;
a gas feed line adapted to feed a gas containing a second reactant to the reaction chamber; and reaction-inducing means for causing a reaction to take place between the first reactant and the second reactant to form a reaction product, in at least a portion of the reaction chamber.
a first reactant feed line for introducing a first reactant to the reaction chamber, the first reactant being non-gaseous;
a plurality of liquid feed inlets at the liquid feed side of the reaction chamber, the liquid-feed inlets being adapted to feed a liquid in a direction substantially perpendicular to the direction of the axis, and in a manner that the liquid changes direction from substantially perpendicular to substantially parallel to the direction of the axis at the coalescing side of the reactor;
a gas feed line adapted to feed a gas containing a second reactant to the reaction chamber; and reaction-inducing means for causing a reaction to take place between the first reactant and the second reactant to form a reaction product, in at least a portion of the reaction chamber.
2. A reactor as defined in claim 1, wherein at least one of the plurality of the liquid feed inlets comprises an atomizer for atomizing the liquid in a form of a pattern.
3. A reactor as defined in claim 2, wherein the pattern is linear.
4. A reactor as defined in claim 1, 2 or 3, wherein the cross-section of the reaction chamber is triangular.
5. A reactor as defined in claim 1, 2, 3, or 4, wherein the gas feed line is located in the vicinity of the front end of the reaction chamber and the first reactant feed line is in the vicinity of the back end of the reaction chamber.
6. A reactor as defined in claim 1, 2, 3 or 5, wherein the cross-section of the reaction chamber is circular.
7. A reactor as defined in claim 1, 2, 3, 4, 5 or 6, wherein the reaction chamber further comprises restrictive baffles forming pools at the coalescing side of said reaction chamber.
8. A reactor as defined in claim 1, 2, 3, 4, 5, 6 or 7, further comprising a re-circulator for transferring liquid from the coalescing side to the liquid feed inlets.
9. A reactor as defined in claim 7 or 8, wherein the predetermined liquid feed inlets are located between the pool and the front end.
10. A reactor as defined in claim 7 or 8, wherein the predetermined liquid feed inlets are located above the pool.
11. A reactor as defined in claim 7, 8, 9 or 10 wherein at least two of the pools have different capacities.
12. A reactor as defined in claim 7, 8, 9, 10 or 11, wherein pools toward the front end have higher capacities than pools toward the back end.
13. A reactor as defined in claim 7, 8, 9, 10, 11 or 12, wherein the pools have progressively larger capacities going from the back end toward the front end of the reaction chamber.
14. A reactor as defined in claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or 13,wherein the ratio of the length of the reaction chamber to the width of said reaction chamber is higher than 10.
15. A reactor as defined in claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or14, wherein the reaction chamber is inclined.
16. A reactor as defined in claim 15, wherein the reaction chamber further comprises restrictive baffles forming pools at the coalescing side of said reaction chamber, the reactor further comprising a re-circulator for transferring liquid from a pool to respective liquid feed inlets, the liquid feed inlets located above said pool.
17. A reactor as defined in claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or14, wherein the reaction chamber is substantially horizontal.
18. A reactor as defined in claim 17, wherein the reaction chamber further comprises restrictive baffles forming pools at the coalescing side of said reaction chamber, the reactor further comprising a re-circulator for transferring liquid from a pool to respective liquid feed inlets, the liquid feed inlets being located in a region from abovesaid pool to the front end of said pool.
19. A reactor as defined in claim 1, 2, 3, 4, 5, 6 or 14, wherein the reactionchamber further comprises restrictive baffles forming pools at the coalescing side of said reaction chamber, the reactor further comprising a re-circulator for transferring liquid from a pool to respective liquid feed inlets, the liquid feed inlets being located above and/or in front of said pool, and wherein the gas feed line is located under said pools.
20. A reactor as defined in claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 or 19, wherein at least one of the plurality of the liquid-feeding inlets comprises an atomizer.
21. A reactor as defined in claim 20, wherein the reaction chamber further comprises restrictive baffles forming pools at the coalescing side of said reaction chamber, the reactor further comprising a re-circulator for transferring liquid from a pool to respective liquid feed inlets.
22. A reactor as defined in claim 1,2,3,4,5,6,7,8,9, 10, 11, 12, 13, 14, 15, 16, 17, 18 or 19, wherein at least one of the plurality of the liquid-feed inlets comprises an orifice adapted to form streams of liquid.
23. A reactor as defined in claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 or 19, wherein at least one of the plurality of the liquid-feed inlets comprises a spatter producing mechanism.
24. A reactor as defined in claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22 or 23, wherein said reaction chamber is divided into different sections adapted to operate under different conditions.
25. A reactor as defined in claim 24, wherein the ratio of the length of the reaction chamber to the width of said reaction chamber is higher than 10.
26. A reactor as defined in claim 24 or 25, further comprising additional inlets in at least one of the different sections, for introducing matter changing reaction characteristics in the at least one of the different sections.
27. A reactor as defined in claim 7, 8, 9, 10, 11, 12, 13, 16, 18, 19 or 21, further comprising means for removing reaction product from a line between at least one pool and the respective liquid feed inlet.
28. A reactor as defined in claim 7, 8, 9, 10, 11, 12, 13, 16, 18, 19 or 21, further comprising means for removing by-product from a line between at least one pool and the respective liquid feed inlet.
29. A reactor as defined in claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or 16, wherein the reaction chamber has an inclination, the reactor further comprising means for adjusting said inclination.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US3383196P | 1996-12-23 | 1996-12-23 | |
| US60/033,831 | 1996-12-23 | ||
| US86121097A | 1997-05-21 | 1997-05-21 | |
| US08/861,210 | 1997-05-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2225763A1 true CA2225763A1 (en) | 1998-06-23 |
Family
ID=26710182
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2225763 Abandoned CA2225763A1 (en) | 1996-12-23 | 1997-12-23 | Pseudo-plug-flow reactor |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2225763A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115121191A (en) * | 2022-07-13 | 2022-09-30 | 重庆大学 | Preparation of PEDOT by gas-liquid two-phase reaction: PSS device and method |
-
1997
- 1997-12-23 CA CA 2225763 patent/CA2225763A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115121191A (en) * | 2022-07-13 | 2022-09-30 | 重庆大学 | Preparation of PEDOT by gas-liquid two-phase reaction: PSS device and method |
| CN115121191B (en) * | 2022-07-13 | 2023-08-04 | 重庆大学 | And (3) preparing PEDOT by gas-liquid two-phase reaction: PSS device and method |
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