US2145576A - Conversion of hydrocarbons - Google Patents

Description

H. V. ATWELL Jan. 31, 1939.

CONVERSION OF HYDROCARBONS Filed July 29, 1937 ATTORNEY Patented Jan. 3l, 1939 UNITED STATES PATENT oFFlcE CONVERSION OF HYDROCRBONS Application July 29, 1937, Serial No. l56,272

i Claims.

My invention relates in general to the conversion of normally gaseous hydrocarbons and more particularly to a unitary process for the production .of normally liquid hydrocarbons suitable for use as motor fuel from lighter gaseous hydrocarbons such as ethylene.

It has been shown that normally gaeous hydrocarbons can be polymerized under suitable conditions to yield normally liquid products. In

w general, however, such known processes of either lili tcularly directed to the processing of the higher molecular Weight hydrocarbons.

A principal object of my invention is to provide a. unitary process wherein normally gaseous hydrocarbons predominating in ethylene are converted to normally liquidproducts suitable for use as motor fuel.

A further object of my invention is to provide a unitary process for the conversion of normally gaseous hydrocarbons comprising substantial amounts of ethylene to normally liquid products lill wherein the ethylene is initially converted, in the 35 presence of a suitable promoter, to unsaturated hydrocarbons of higher molecular weight and wherein normally gaseous hydrocarbons comprising unsaturated hydrocarbons of higher molecular weight so produced aresubjected to polymerizing conditions of temperature and pressure toefect the conversion of normally gaseous hydrocarbons to normally liquid products suitable as motor fuel.

Another object of my invention is to provide a unitary process for the polymerization of normally gaseous hydrocarbons wherein normally gaseous hydrocarbons comprising both saturated and unsaturated hydrocarbons are converted to normally liquid products and wherein ethylene, heretofore found diicult to convert because of its apparent refractoriness, is converted in continuous stream to unsaturated hydrocarbons of higher molecular weight suitable for treatment in the polymerization phase of the cycle thus obs taining greater yields of liquid products than (lill. ISG-lili) have heretofore been obtained from a similar raw material.

Another object of my invention is to provide a unitary process for the conversion of normally gaseous hydrocarbons predominating in lower molecular weight unsaturated hydrocarbons to normally liquid products wherein the normally gaseous hydrocarbons are treated to eiect conversion ofthe lower molecular weight unsaturated hydrocarbon to unsaturated hydrocarbons of higher molecular weight with the simultaneous production of olen oxides, for example ethylene oxide, capable ofpromoting polymerization reactions and wherein normally gaseous hydrocarbons comprising the higher molecular weight unsaturates and the olefin oxides produced therewith are subjected to conditions of temperature and pressure whereby conversion of normally gaseous hydrocarbons to normally liquid, stable, gasoline-like products of high antiknock value is effected. f

My invention contemplates a process for the conversion in a continuous stream of normally gaseous hydrocarbons comprising substantial amounts of ethylene, or consisting essentially or principally of ethylene to normally liquid products in the gasoline lboiling range, wherein the normally gaseous hydrocarbons are treated, in the presence of a suitable promoter toconvert ethylene to unsaturated hydrocarbons of higher molecular weight. The normally gaseous hydrocarbon stream comprising the higher boiling unsaturates so produced is subjected to conditions of temperature and pressure whereby normally gaseous hydrocarbons are converted to normally liquid products in the gasoline boiling range. The conversion products are fractionated to separate normally liquid products from the normally gaseous products. The normally gaseous reaction products are again fractionated to segregate a fraction predominating in hydrocarbons having three or more carbon atoms to the molecule which may be recycled .to the thermal conversion zone. 'Ihe remaining normally gaseous products comprising ethane, ethylene, hydrogen and methane are further fractionated to segregate a fraction predominating in ethane and ethylene which is recycled to the primary conversion zone wherein ethylene is converted to unsaturated hydrocarbons of higher molecular weight. If desired the hydrocarbon fraction predominating in ethane and ethylene may be treated to effect a concentration of the ethylene before recycling the traction to the primary conversion zone.

the treatment of gases in which the concentration of ethylene is particularly high. My invention, therefore, has the further advantage of being able to operate on the effluent gases normally eliminated from some polymerization units because of theirl high ethylene content.

When charging those normally gaseousy hydrocarbons for which my-process is especially adapted, that is, those containing substantial amounts of ethylene, the hydrocarbons in admixture with controlled quantities of a promoting agent capable of converting ethylene to unsaturated hydrocarbons of higher molecular weight are passed through a preheating coil and discharged into a reaction zone, under conditions which will effect the conversion of ethylene to unsaturated hydrocarbons of higher molecular weight.

Suitable agents for promoting the conversion of ethylene to unsaturated hydrocarbons ofhigher molecular weight are: oxygen or an oxygencontaining gas, halogens, sulfur or compounds of these elements such as SO2 or SaClz. Of these oxygen is preferred. When oxygen is used as the activating agent there will be produced simultaneously with the conversion of ethylene to unsaturated hydrocarbons of higher molecular weight small quantities of oleiine. oxides, such as ethylene oxide, which are of especial value in promoting thel ,subsequent conversion of normally gaseous hydrocarbons to normally liquid products.

The invention will be more fully understood from the following description read in connection with the accompanying drawing showing diagrammatically an elevation of one form of apparatus for carrying out the process of the invention.

Referring to the drawing, normally gaseous hydrocarbons predominating drawn through line I from an outside source, not shown, and forced by means of pump 2 through line I, controlled by valve 3, into a preheating coil 5 positioned in furnace '6. Prior to their entry into preheating coil 5, the hydrocarbon gases are mixed with an activating agent, for example oxygen, supplied from an outside source, not shown, through line I controlled by valve 8. The

quantity of oxygen added to the charge may vary between 0.5% and 3%, and should preferably be about 1%, by volume of the charge passed into coil 5. The stream of hydrocarbons with the admlxed oxygen is preheated in coil 5 to a temperature of approximately 750 to 1200 F., and at a low pressure ranging from slightly above atmospheric to about pounds per square inch. 'I'he preheated gaseous mixture leaving coil 5H is passed through line 9 into the reaction chamber I0 wherein the conditions of temperature and pressure prevailing in coil 5 are maintained. Although in the specific example illustrating the invention the conversion of etlwlene to unsaturated hydrocarbons of higher molecular weight is carried out in a reaction chamber, the invention is in no wise limited to the use of such reaction chamber, and the reaction may be effected in a separate coil or in a continuation of coil 5 itself. When the given temperature and pressure conditions are carefully maintained in coil in ethylene are 5 and reaction chamber I0, a substantial portion of ethylene, in the presence of the admixed oxygen, is converted in reaction chamber I0' to unsaturated hydrocarbons having three and four carbon atoms to the molecule. The gases are maintained in the reaction chamber I0 for a period of time sufliciently long to eiect the desired conversion, which will normally not exceed about ten seconds. The mechanism of the reaction or reactions by which ethylene is converted in reaction chamber I0 to unsaturated hydrocarbons of higher molecular weight is not fully understood. It is probable that the presence of the oxygen promotes the disruption of the carbon to hydrogen linkages of the ethylene in a manner the conversion of ethylene to unsaturated hydrocarbons of higher molecular weight other promoters such as halogens, sulphur or compoundsof these elements such as SO2 or SzClz may be used. When, as in the present instance, oxygen is used as the activating agent for the primary conversion operation there are formed, simultaneously with the higher molecular weight unsaturated hydrocarbons, lesser quantities of oxygenated hydrocarbons comprising olen oxides, for example, ethylene oxide, as well as small amounts of hydrogen and oxides of carbon.

Reaction rproducts comprising the higher mo- .lecular weight unsaturated hydrocarbons propylene and butylene, and the hydrogen and oxygenated products produced. simultaneously therewith, comprising oleiin oxides such as ethyleneoxide, are withdrawn from reaction chamber I0 through line II controlled by valve I2 and conducted to a heat exchanger I3 wherein the products are cooled by indirect heat exchange with v a suitable cooling medium which may be fresh charge to the system. Additional cooling by means of indirect exchange not shown in the drawing may be resorted to if desired. To enable compression of the gaseous stream to that pressure desired in the subsequent phase of the process the gases are cooled in heat exchanger I3 to a .temperature at which such compression can more easily be effected, for example, 300 to 500 F. The cooled stream is conducted from exchanger I3 through line I4 to compressor I5 wherein the` gases are brought to a pressure of from 400 to 3000 lbs. and preferably about 1000 to 1500 lbs. from compressor I5 through lines I6 and I1 into conversion coil I8 positioned' in furnace I9 wherein the hydrocarbon stream is raised to a temperature of 750.to 1250 F. and preferably from 900 to l050 F. to eect the conversion of normally gaseous hydrocarbons to normally liquid products in the gasoline boiling range. Normally gaseous hydrocarbons, substantially parafiinic in character, or containing both paraflins and olelns, may be drawn from an'outslde source through line 20 controlled by valve 2| and forced by means of pump 22 into line I1 wherein they are mixed with the products resulting from the ethylene conversion operation. As an alternative to their direct introduction into the system through line 20 the normally gaseous hydrocarbons may, by means of connections not shown in the drawing, be preheated by passage through exchanger i3 and the preheated gases introduced into line i'l. If desired, these additional hydrocarbons may be preheated by direct admixture with the hot reaction products emanating from reaction chamber l and the resulting mixed stream passed to compressor l5. For example, these additional hydrocarbons may be admixed with the hot products from chamber lll by introduction through line 50, provided with valve lil, which connects with line Il. The conversion of normally gaseous hydrocarbons to normally liquid products eiected in conversion coil i3 may be, as described, oi the thermal type involving both polymerization and alkylation rcactions although catalyst may be used to effect the desired conversion. The presence, in the conversion coil i3, of olefin oxides, for example ethylene oxide, produced in reaction chamber lll simultaneously with the conversion of ethylene to unsaturated hydrocarbons of higher molecular weight, materially aids in promoting the conversion of normally gaseous hydrocarbons to liquid products. If the production of these olefin oxides in reaction chamber i3 should be below the quantity required for the desired promotional eect in the subsequent thermal conversion phase of the process, or if they should be completely absent due to the use of an activating agent other than oxygen in reaction chamber l0', olefin oxides, such as ethylene oxide, may be supplied from an outside source through line 23 controlled by valve 2li and admixed with the gaseous charge flowing through line il' to the conversion coil lll.

Reaction products pass from conversion coil i3 through line 23 and are cooled to below an 'active polymerization temperature by indirect heat exchange in exchanger 23. Additional cooling or quenching of reaction products in line 23 by means not shown in the drawing may be resorted to if desired. The cooled reaction products pass into a fractionator 2l wherein normally liquid products having a boiling point above that of the gasoline boiling range are separated and withdrawn from the bottom through line 33 controlled by valve 23. Uncondensed vapors and gases are passed from the primary fractionator 3l through line 33 to fractionator 3l wherein normally liquid products in the gasoline boiling range are condensed and withdrawn from the -bottom of fractionator 3l through line 32 controlled by valve 33. Normally gaseous reaction products comprising hydrocarbons having less than ve carbon atoms to the molecule and hydrogen are passed from fractionator 3l through line 33 to another fractionator 33 wherein a fraction predominating in three and four carbon atoms to the molecule is segregated. This fraction is drawnrom fractionator 35 through line 33 controlled by valve 3l and recycled to the thermal conversion zone i3 by means of pump 3,3 which forces the fraction through line 33 into line l1. Normally gaseous reaction products not vcondensed in fractionator 35 and comprising ethane, ethylene, methane and hydrogen are passed from fraftionator 35 through line t0 into fractionator 4l. a fraction predominating in ethane and ethylene is segregated from the lighter gases comprising In fractionator 4l methane and hydrogen which leave fractionator 4l through line 42 controlled by valve 33 and are eliminated from the system. The hydrocarbon fraction predorninating in ethane and ethylene in liquefied condition is drawn from fractionator 4l through line M and forced by means of pump 45 through line 56 into line 4 leading to the ethylene conversion phase of the process. The ethylene-ethane fraction drawn from fractionator 3l may be subjected to any desired treatment, not shown in the drawing, whereby the ethylene in the fraction is concentrated before being returned to the ethylene conversion stage of the cycle. Such ethylene concentration could be effected, for example, by absorption of the ethylene by a suitable absorbing medium such as acetone, acetaldehyde -or liquid acetylene with subsequent recovery of the absorbed ethylene which is then returned to the ethylene conversion zone. i

Normally gaseous hydrocarbons predominat- J ing in or consisting essentially of ethylene are charged to the system, as has been pointed out above, through line l. If it is desired to process normally gaseous hydrocarbons comprising substantial proportions of hydrocarbons having more than two carbon atoms to the molecule, or

less than two carbon atoms to the vmolecule in addition to ethylene'the charge may be introduced into the system through line lll controlled by valve 33 and forced by means of pump 33 through line 50 into fractionator 33 to be subjected to fractionation therein together with the Vnormally gaseous reaction products resulting from the thermal conversion operation.

Although in the specic example set forth to illustrate the invention the unsaturated hydrocarbons produced by the conversion of ethylene in the primary conversion phase of the process are converted to normally liquid products "in a thermal conversion type of operation, 'it is to be understood that the process is not limited to the use of this particular type of operation toeffect this phase of the process. The normally gaseous unsaturated hydrocarbons resulting from the conversion of ethylene into unsaturated hydrocarbons of higher molecular weight may be converted to liquid products in a polymerization operation of the catalytic type whereinthe normal gaseous hydrocarbonsV are subjected to a temperature of from 300 to 600 F., preferably about 400 to 500 F., and a pressure of 50 to 500 pounds, preferably 100 to 200 pounds in the presence of an active polymerization catalyst such as phosphoric acid. While phosphoric acid is preferred, other catalysts such as aluminum chloride, alumina on silica, sodium aluminum' chloride, sulfuric acid or similar catalysts may be used.

The invention as set forth is particularly applicable to the conversion, in the primary phase of the process, of ethylene to unsaturated hydrocarbons of higher molecular weight. 1 wishto point out that my process is not limited to the the conversion of this particular unsaturate ln this phase of the process and that, should it be desired, propylene or a higher unsaturate may be charged to the primary conversion zone of the process in place of the ethylene, or together with ethylene, to be converted to higher olefins without detracting from the effective operation `of the process according to the invention.

elli

j As pointed out above, the presence of the olen oxides, for example ethylene oxide, formed simultaneously with thevhigher molecular weight unsaturated hydrocarbons in reaction chamber lll are of particular value in promoting polymerization reactions either of the thermal or catalytic type. Furthermore, their presence in the systemlends to the normally liquid polymers drawn from fractionator 3| through line 32 a high degree of gum stability. Products of polymerization containing olefin oxides maybe mixed with cracked gasoline of a high unsaturate content andthe mixture digested at a moderately high temperature, `for example, 400 to 700 F., at a moderately high pressure, for example, 500 to 1000 pounds for a sulcient period of time to effect the desired polymerization of gum-forming constituents in the mixture. A small amount of olein oxides, for example, ethylene oxide from an outside source may be added to the mixture of polymer and cracked gasoline to promote the complete polymerization of any potential gumforming compounds in the gasoline blend.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. The method of converting normally. gaseous hydrocarbons to normally liquid` products which comprises subjecting an ethylene-rich gaseous hydrocarbon mixture in admixture with oxygen to elevated temperature in a primary conversion zone to eiect conversion of ethylene to normally I gaseous olefin hydrocarbons having more than two carbon atoms per molecule and olefin oxides, admixing the hot reaction products from said primary conversion zone with a gaseous hydr0- carbon mixture containing hydrocarbons having more than two carbon atoms per molecule to reduce substantially the temperature of said reaction products, and subjecting the resulting mixwherein the pressure maintained in said primary' I conversion zone is not greater than from atmospheric to 100 pounds per square inch, and the` pressure applied to the reaction products" therefrom is substantially greater.

3. The method of treating a hydrocarbongas mixture comprising ethylene and hydrocarbons having at least three carbon atoms per molecule -which comprises treating said mixture to separate therefrom an ethylene-rich fraction and a C3 fraction predomlnating in hydrocarbons having at least three carbon atoms per molecule, subjecting said ethylene-rich fraction in admixture with oxygen to elevated temperature in a primary conversion zone under conditions suitable to eiect conversion of ethylene to normally gaseous olen hydrocarbons' having more than two carbon atoms per molecule and olen oxides, admixing the reaction products from said primary conversion zone with sald C3 fraction, and subjecting the resulting mixture' to elevated temperature whereby olefin oxides present therein promote conversion of normally gaseous hydrocarbon constituents to normally liquid products. 4. The method in accordance with claim 3 herein the reaction in said primary conversion zone is effected under relatively low pressure, the

hot reaction products therefrom are admixed with said C3 fraction to substantially reduce the temperature of said reaction products, and the resulting mixture is subjected to elevated temperature at relatively high pressure to effect production of normally liquid products.

HAROLD V. ATWELL.

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