MXPA00006950A - Catalyst suitable for the preparation of hydrogen and carbon monoxide from a hydrocarbonaceous feedstock - Google Patents

Abstract

A catalyst comprising a catalytically active metal, selected from Ru, Rh, Os and Ir, associated with at least one inorganic metal cation or precursor thereof, wherein the inorganic metal cation or precursor thereof is present in intimate association supported on or with the catalytically active metal, a process for the preparation of the catalyst, and a process for the preparation of carbon monoxide and/or hydrogen from a hydrocarbonaceous feedstock using the catalyst.

Description

CATALYST ADEQUATE FOR THE PREPARATION OF HYDROGEN AND CARBON MONOXIDE FROM "-DE-A RAW MATERIAL HYDROCARBONACEA DESCRIPTION OF THE INVENTION The present invention relates to a catalyst suitable for the preparation of carbon onoxide and / or hydrogen from a gaseous or liquid hydrocarbonaceous raw material, a process for the preparation of such a catalyst and a catalytic partial oxidation process, using such a catalyst. The partial oxidation of hydrocarbons, for example, methane or natural gas, in the presence of a catalyst is an attractive route for the synthesis gas preparation. The partial oxidation of a hydrocarbon is an exothermic reaction and in the case where the methane is the hydrocarbon, it proceeds by the following reaction: 2CH4 + 0; 2CO + 4H.

The optimal catalytic partial oxidation process for commercial scale application would provide high yields of carbon monoxide and hydrogen at high pressures, for REF.121315 example, around 30 bar and high space velocities, for example, in the order of l and OJC G 000 Nl / Kg / h, or more. For thermodynamic reasons, in order to obtain high productions of carbon monoxide and hydrogen under these process conditions, it is necessary to operate the partial oxidation process at high temperatures. The literature contains a number of documents describing details of experiments conducted in the catalytic oxidation of hydrocarbons, in particular methane, using a wide range of catalysts. Reference is made, for example, to US -A- 5, 149, 464, WO 92/11199 and WO 93/01130. Most of these experiments, however, have been conducted under relatively moderate conditions or under conditions not suitable for the operation of a large commercial catalytic partial oxidation process. In addition, the literature contains a number of documents describing details of experiments conducted in the catalytic partial oxidation of hydrocarbons under conditions required for commercial operation to produce mixtures of carbon monoxide and / or hydrogen.

EP-A-640561 discloses that the catalytic partial oxidation process can be carried out under conditions demanded by commercial processes, in high performance with low deactivation by employing a catalyst comprising a catalytically active Group VIII metal supported on a refractory oxide having at least two cations selected from Groups IA, IIA, IIIA and IVA of the Periodic Table or the transition metals. Furthermore, EP-A-737164 discloses that, when operated under the conditions of high pressure and at high temperatures as demanded by a commercial process, the catalytic partial oxidation of hydrocarbons can, in the presence of nitrogen, produce a gas product. of synthesis containing a number of byproducts, in particular ammonia (NH3) and hydrogen cyanide (HCN), in low but significant amounts. It has been found that such by-products can adversely affect downstream processes for converting carbon monoxide and / or hydrogen produced by the catalytic partial oxidation process, for example, in the case of Fisher-Tropsch synthesis or of methane synthesis !. The presence of by-products, in ammonia or hydrogen cyanide, in the products of the catalytic partial oxidation process, is therefore undesirable. In EP-A-737164, it is described that the generation of such by-products is significantly lower in a process employing a catalyst comprising rhodium, iridium or platinum as the catalytically active metal. At such levels, it is possible to remove any unwanted by-products, using known solvents, adsorption processes and the like. The alumina is used as the catalytic support. WO 96/04200 discloses a catalytic partial oxidation process employing a Group VIII catalytically active metal supported on a zirconium-based carrier, which has a high thermal shock resistance. In EP 548 679 a catalytic partial oxidation process is described wherein a catalyst containing ruthenium and / or rhodium as the active ingredient and cobalt and / or manganese as a promoter is used.

According to the above, it will be apparent that there is a condition number - »- and circumstances that affect the execution of a partial, catalytic oxidation reaction and that while it is possible to optimize in terms of individual execution parameters, there is some conflict between opt individual imitations, each directed specifically to one of the previous execution parameters, where it is not possible to operate a process with simultaneous optimization of all the conditions. Specifically, nitrogen is present in many natural gas raw materials and the preparation of pure, nitrogen-free oxygen on a commercial scale is both very expensive and technically difficult. Therefore, the process must produce acceptably low levels of secondary product containing N. In addition, the selection of the catalytically active metal, refractory oxide and the like in the catalyst to be effective on a commercial scale must be made taking into account factors that they include resistance to high temperature and pressure and resistance to thermal shock under extreme conditions to be employed in terms of the factors mentioned hereinabove. Finally, the process must produce optimal yields and selectivity to desired products and optimal life time under such extreme conditions and, of course, under conditions of variation that may prevail in the case of fluctuations in operation. According to the above, there is a need for a process for the catalytic partial oxidation of hydrocarbons in which nitrogen may be present during partial oxidation reactions, which may be applied on a commercial scale to produce a carbon monoxide product. and / or hydrogen in high yield and selectivity, containing a minimum of components such as ammonia and hydrogen cyanide and at low or negligible catalyst deactivation ranges. Surprisingly, it has been found that by employing in the catalytic partial oxidation process a catalyst comprising the catalytically active metal associated with an execution modifying cation selected from Al, Mg, Zr, Ti, La, Hf and Si, The above objectives can be achieved admirably, for a wide range of operating conditions. In addition, the selection of the cation employed can be used to optimize specific execution factors, including raw material conversion and product performance, catalyst stability, coke formation, superior temperature control and the like. above, the present invention provides a catalyst comprising a catalytically active metal selected from Ru, Rh, Os and Ir, associated with a metal cation selected from Al, Mg, Zr, Ti, La, Hf and Si, supported on a carrier suitable, obtainable by a process which comprises providing the cation of metal and the ca-active metal in solutions suitable for impregnation or coimpregnation on the carrier, drying and optionally calcination.The inorganic metal cation is selected from Al, Mg, Zr, Ti , La, Hf and Si, of which Zr is preferred.The cation is preferably in the form of its oxide.The catalyst can be supported on a carrier, for example, comprising a refractory oxide having at least one cation or comprising a metal or other wear resistant substrate at high temperature. ----- «_. Preferably, the catalyst comprises cation to metal in an atomic range in excess of or equal to 1.0 on its surface, more preferably, in excess of or equal to 2.0, even more preferably, in excess of or equal to 3.0 up to a maximum only limited by the restrictions of the method to build the catalyst, for example, impregnation. It is a particular window of the catalyst of the present invention that the association nature of the catalytically active metal and the metal cation would be at least partially self-regulating or directing. Without being limited by theory, it would seem that a form of raw material conditioning through metal cation serves to optimize the catalytic activity and by this generate improvement in the performance parameters of performance, selectivity, resistance to deactivation and low formation of secondary products simultaneously. The catalytically active metal is selected from ruthenium, rhodium, osmium and iridium, preferably rhodium and iridium. As discussed hereinabove, these ~ -m ^ ka1 offer the significant advantage that substantially lower amounts of ammonia and hydrogen cyanide are produced during the catalytic partial oxidation reaction, compared to the other metals of Group VIII of the Periodic Table of the Elements. The catalyst may comprise the catalytically active metal in any suitable amount to achieve the appropriate level of activity. Typically, the catalyst comprises the active metal in an amount in the range of 0.01 to 20% by weight, preferably, 0.02 to 10% by weight, more preferably, 0.1 to 7.5% by weight. The catalyst may comprise the metal cation in any suitable amount to achieve the required level of selectivity and conversion and resistance to deactivation. Normally, the catalyst comprises the metal cation in an amount of at least 0.5% by weight. The cation is preferably present in the catalyst in the range of 1.5-15.0% by weight, more preferably 5.0 to 15.0% by weight.

The metal is catalytically supported on a carrier. Suitable carrier materials are well known in the art and include refractory oxides, such as silica, alumina, titania, zirconia, and mixtures thereof. Mixed refractory oxides, that is, refractory oxides comprising at least two cations, can also be used as carrier materials for the catalyst. The most suitable refractory oxide carriers are binary oxides of zirconia and alumina, in particular in (partially) stabilized form such as AEZ (zirconia hardened alumina) or ZPE (partially stabilized zirconia), mulite or alumina. Also, metals or metal alloys, for example, alloys of the fecralloy type, preferably in the form of gauzes, can be suitably applied as a carrier material. A suitable technique for associating the metal and the metal cation is impregnation, in the event that the metal and cation are supported on a carrier as defined herein above. Preferably, the carrier is impregnated with a solution of a catalytically active metal compound and a solution of a salt of the metal cation, followed by se-ca-βte and optionally, calcination of the resulting material. The solutions are preferably combined in a suitable amount and co-impregnated. Alternatively, the impregnation can be sequential, with the first stage of impregnation, drying and optionally, calcination with the catalytically active metal solution and the second stage of impregnation, drying and optionally, calcination with the metal cation solution or a mixture of this with the catalytically active metal solution. Preferred techniques for impregnation are sinking, painting, spraying, immersion, application by measured drop and the like of a suspension or solution of the modification cation, with subsequent drying in hot air or the like and calcination, so as to achieve a uniform impregnation. Preferably, the impregnation and / or drying is carried out in the absence of distorting gravitation, meniscus or capillary effects during drying, which could provide an undesired gradient or total content of the impregnated cation. For example, the oxide support can be rotated or suspended in such a way that contact with any others does not produce meniscus or capillary effects. According to the foregoing, in a broader aspect of the invention, a process for the preparation of a catalyst apt to catalyze a partial oxidation reaction is provided, the catalyst comprises a catalytically active metal, selected from Ru, Rh, Os and Ir, associated with a metal cation selected from Al, Mg, Zr, Ti, La, Hf and Si supported on a carrier, the process comprises providing the cation of metal and the catalytically active metal in solutions suitable for precession or co- impregnation on the carrier, drying and optionally, calcination. In another aspect of the invention, a process is provided for the preparation of carbon monoxide and / or hydrogen from a hydrocarbonaceous raw material, which process comprises contacting a mixture with the raw material and a gas containing oxygen with a catalyst comprising a catalytically active metal, selected from Ru, Rh, Os and Ir, associated with a metal cation selected from Al, Mg, Zr, Ti, La, Hf and Si, supported on a carrier, obtainable by a process that it comprises providing the metal cation and the catalytically active salt in solutions suitable for impregnation or co-impregnation on the carrier, drying and optionally calcination. The process of the present invention can be used to prepare carbon monoxide and / or hydrogen from any hydrocarbonaceous raw material that is gaseous under the conditions prevailing during the partial oxidation reaction. The raw material may contain compounds that are liquid and / or compounds that are gaseous under standard conditions of temperature and pressure (i.e., at 0 ° C and 1 atm.). The process is particularly suitable for the conversion of methane, natural gas, associated gas or other sources of light hydrocarbons. In this regard, the term "light hydrocarbons" is a reference to hydrocarbons having from 1 to 5 carbon atoms. The process can be applied in the conversion of reserves that are present in stable mint in the nature of methane that contain a substantial amount of carbon dioxide. The feed, preferably, comprises methane in an amount of at least 50% by volume, more preferably, at least 75% by volume, especially, at least 80% by volume-m &; & *; The process is also particularly suitable for the conversion of liquid hydrocarbon raw materials such as naphtha raw materials having boiling points between 35 ° C and 150 ° C, kerosene raw materials with boiling points of between 150 ° C and 200 ° C, petroleum raw materials of synthetic gas with boiling points between 200 ° C and 500 ° C, in particular, between 200 ° C and 300 ° C. It is possible to have hydrocarbonaceous material present in the raw materials to be used in the process according to the present invention, which are gaseous. under standard conditions of temperature and pressure, together with materials that are liquid under standard conditions of temperature and pressure. Hydrocarbons that are liquid under standard conditions of temperature and pressure usually contain up to 25 carbon atoms in their molecules. The process according to the present invention can also be carried out when the raw material contains oxygenates (being gaseous and / or being liquid under standard condition of temperature and pressure). The oxygenates are used as (part of) the raw material in the process according to the present invention are defined as molecules containing, apart from carbon and hydrogen atoms, at least 1. Oxygen atom that is bonded to either one or two carbon atoms or a carbon atom and a hydrogen atom Examples of suitable oxygenates include methanol, ethanol, dimethyl ether and alkanols, ether, acids and esters having up to 25 atoms Furthermore, mixtures of hydrocarbons and oxygenates, as defined above, can be used as raw material in the process according to the present invention.The hydrocarbonaceous raw material is contacted with a gas containing oxygen during the partial oxidation process. You can use air as the oxygen-containing gas, in which case nitrogen will be present in the feed and reaction mixture in large quantities. e can use substantially pure oxygen or air enriched with oxygen.

Preferably, the feed comprises the hydrocarbon feedstock and oxygen in amounts that provide an oxygen-to-carbon range in the range of from 0.3 to 0.8, preferably, from 0.45 to 0.75. References to the oxygen-to-carbon range refer to the oxygen range in the form of molecules (02) to carbon atoms present in the hydrocarbon feedstock. The oxygen-to-carbon ranges of the stoichiometric range, 0.5, that is, in the range of 0.45 to 0.65, are particularly suitable. If oxygenated raw materials are used, for example, methanol, oxygen-to-carbon ranges below 0.3 can be used appropriately. The feed may, optionally, comprise steam. If steam is present in the feed, the vapor-to-carbon range (that is the range of vapor molecules (H20) to carbon atoms in the hydrocarbon), is preferably in the range of more than 0.0 to 3.0, more preferably, from more than 0.0 to 2.0. The process of the present invention is put into operation at elevated pressures, that is, significantly higher pressures of atmospheric pressure. The process is put into operation normally at pressures in the range of hasfe * 150 bara (absolute bar). Preferably, the operating pressure is in the range of from 2 to 125 bara, more preferably, from 5 to 100 bara. The process can be put into operation at any suitable temperature. Under these preferred high pressure conditions prevailing in the process, the feed gases are allowed to contact the catalyst at elevated temperatures in order to achieve the conversion level required for a commercial scale operation. According to the above, the process is normally operated at a temperature of, therefore. less, 750 ° C. Preferably, the operating temperature is in the range of from 800 to 1300 ° C, more preferably, in the range of from 900 to 1200 ° C. - Temperatures in the range of 1000 to 1200 ° C are particularly suitable with substantially pure oxygen, or in the range of 800 ° C to 1000 ° C with air. The reference here to temperature is at the temperature of the gas leaving the cat to the igniter.

The feed mixture is normally supplied during the catalytic catalytic oxidation process at gas space velocities (expressed as normal liters (ie, liters at 0 ° C and 1 atm) of gas per kilogram of catalyst per hour) in the range of from 20,000 to 100,000,000 Nl / Kg / h, preferably, in the range of 50,000 to 50,000,000 Nl / Kg / h. Space velocities in the range of 500,000 to 30,000,000 Nl / kg / h are particularly suitable. The gaseous mixture of the hydrocarbonaceous raw material and the oxygen-containing gas is preferably contacted with the catalyst under adiabatic conditions. For the purposes of this specification, the term 'adiabatic' is a reference to the reaction conditions in which substantially any loss of heat and radiation from the reaction zone is prevented, with the exception of heat leaving the gaseous effluent stream of the reactor Any suitable reaction regime can be applied in the process of the present invention, in order to contact the reactants with the catalyst.A suitable regime is a fluidized bed, wherein the catalyst is employed in the form of fluted particles. by a gas stream.A preferred reaction regime for use in the process is a fixed bed reaction regime, wherein the catalyst is retained within a reaction zone in a fixed array. can be used in the fixed-bed regime, retained using fixed-bed reaction techniques well known in the art. In this case, the fixed arrangement may comprise the catalyst in the form of a monolithic structure. A more preferred monolithic structure comprises a ceramic foam. The ceramic foams suitable for use in the process, are commercially available. In addition, alternative forms for the catalyst include monolithic refractory oxide honeycomb structures or metal gauze structures. A mixture of carbon monoxide and hydrogen prepared by means of the process of this invention, is particularly suitable for use in the synthesis of hydrocarbons, for example, by means of the Fisher-Tropsch synthesis or the synthesis of oxygenates, for example, methanol . Processes for the conversion of the carbon monoxide and hydrogen mixture to those products are well known in the art. Hydrogen or a mixture with other gases, prepared by means of the process of this invention, may be particularly suitable for use as n-fuel, either directly or indirectly. The process of this invention could be used very appropriately to provide the hydrogen feed for a fuel cell. In the fuel cells, hydrogen and oxygen are passed over the fuel cell in order to produce electricity and water. Fuel cell technology is well known in the art. The present invention is described more fully by way of the following illustrative examples.

Example 1 Preparation of catalyst - not according to the invention A ceramic foam of 1600 ppcm "2 (pores per cm2) was cut to size to fit the reactor or was crushed and sieved to 30/80 mesh particles before its placement at 120 ° C throughout the night. (particles) was weighed and the amount of rhodium or iridium chloride solution needed to provide a rhodium or iridium load at 5% by weight was calculated. The solution was added to the foam (particles) to impregnate them in three stages and the foam (particles) was dried in an oven at 140 ° C and between each impregnation. This was repeated until all the necessary amount of solution was added. After this, the foam (particles) was added and calcined in air as indicated below: 4 hours at 120 ° C, the temperature rises to 700 ° C with 80 ° C / hour, 4 hours at 700 ° C and cooled to 120 ° C. The resulting catalysts consisted of 5.0 wt% iridium or rhodium on ZPE (partially stabilized zirconia), AEZ (zirconia hardened alumina), alumina or mulita foam. The results are indicated in Table 1.

Use 2 Preparation of catalyst - according to the invention The procedure of Example 1 was followed, except that the impregnation solution was modified by the addition of a solution of a salt of an inorganic cation calculated to give a load of 5% by weight of the inorganic cations. The solutions were selected from zirconyl nitrate, Mg nitrate, Al nitrate and their mixtures. The resulting catalysts consisted of 5.0% by weight of iridium or rhodium cations and 5% by weight of Zr, Mg, Al or Mg-Al cations, coimpregnated on ZPE foam, AEZ, alumina or mulite of 1600 ppcr "2 co impregnated.Example 3 Preparation of catalyst - according to the invention The procedure of Example 1 was followed, with the additional step of a second impregnation using a solution of a salt of an inorganic metal cation calculated to provide a charge of 5% by weight of the inorganic metal cation The second impregnation was carried out using the same procedure of Example 1 for the first impregnation The resulting impregnated foam (particles) was calcined using the procedure of Example 1. ----- The resulting catalysts comprised 5.0 wt% of Ir or Rh and 5 wt% of Zr cations, sequentially impregnated on alumina or Y-ZPE foam The results are shown in Table 3.

Table 3 Use 4 Catalytic partial oxidation A reactor was built, which comprised a transparent sapphire tube or metal. The modified catalyst prepared as described here above was coffee and in the tube and retained in the form of a fixed bed of catalyst. Methane and air or air enriched with oxygen (02: N2 is 1.8 v / v), in sufficient quantities to provide an oxygen-to-carbon range in the range of 0.49 to 0.64, were completely mixed just before being introduced into the reactor to be contacted with the fixed catalyst bed. The mixture of methane and air or air enriched with oxygen was fed to the reactor at a pressure of 11 bara and at a space velocity per hour of gas (VEHG) in the range of 2,500,000 to 3,600,000 Nl / Kg / h. The composition of the gas mixture leaving the reactor was determined by gas chromatography and weighing the condensed water from the gas stream leaving the reactor. In Tables 5 to 9, the results are given as xCH4 (% conversion of methane), sCO and sH2 (selectivity to CO and H2).

Table 4 CPO enriched air: Execution of Ir / Y-ZPE with metallic cation (VEHG is 3,300,000 NI / Kg / h, - "- € 2 C Performance at thermodynamic equilibrium Table 5 CPO enriched air: Effect of the modifier on Ir / Y-ZPE (VEHG is 3,400,000 Nl / Kg / h; Q2: C is b Declination in xCH4 for 24 h The results presented in Table 4 and 5 indicate that the modifiers have * »- a beneficial influence on CH4 conversion. The important parameters of the catalyst performance are: a high CH conversion, a low compensation of NH3 and a high stability. Stability is expressed as the decrease in CH4 conversion as a function of time. The zirconia modifier seemed to be the most beneficial: the CH4 conversion of this catalyst was greater, while at the same time the compensation of NH3 was not increased much. This catalyst was tested for stability and appeared to be greater than the stability of the catalyst without modifier. The Zr modification of the CPO catalysts is not only beneficial for the catalysts supported on Y-ZPE. An even stronger effect is observed with an alumina support. The Ir / alumina catalyst was not active in the air-enriched CPO experiment, while the Ir / alumina modified with Zr showed excellent performance. A high and stable CH4 conversion was measured (see Table 6).

Table 6 CPO enriched air: Ir / alum-á-aa performance (alumina: Dytech Poral 20; (VEHG is 4,900,000 The air-CPO experiments are of interest.

It also seems that under these conditions the Zr modification shows its benefits. The catalysts have been prepared with active phases that differ and different supports and the results show an improved execution of many systems when the Zr modification is applied (see Table 7). The catalysts modified with Zr show a higher CH4 conversion, while the NH3 form is not greatly diminished. In Table 9, the and lc-lf represent catalysts in disagreement with the invention, given for comparative purposes with corresponding catalysts according to the invention. - "-» In the process using catalyst 3b, prepared by impregnating a solution of zirconia in Ir / Y-ZPE, the presence of zirconium improves the performance of the catalyst, without changing the Ir dispersion. However, the catalyst prepared from This way is not as good as the catalyst where the Ir and Zr are mixed in the impregnation solution.

Table 7 Air-CPO: Effect of Zr on different supports It is noted that, in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (9)

1. CLAIMS Having described the invention ^^ as above, claim .co or property, contained in the following claims: 1. A process for the preparation of a catalyst comprising a catalytically active metal, selected from Ru, Rh, Os and Go , associated with a metal cation selected from Al, Mg, Zr, Ti, La, Hf and Si, supported on a carrier, the process is characterized in that it comprises providing the cation of metal and the metal c active in suitable solutions p- for impregnation or co impregnation on the carrier, drying and optionally calcination.
2. 2. The process according to claim 1, characterized in that the cation of metal and the catalytically active metal are provided in solutions suitable for coimpregnation.
3. 3. A catalyst characterized in that it comprises a catalytically active metal, selected from Ru, Rh, Os and Ir, associated with a metal cation selected from Al, Mg, Zr, Ti, La, Hf and Si, supported on a carrier, obtainable by a process according to claim 1 or 2.
4. 4. A catalyst according to claim 3, characterized in that the metal -e-ß-thion is a zirconium cation.
5. 5. A catalyst according to any of claims 3 to 4, characterized in that the carrier is a wear-resistant carrier, resistant to high temperatures, the carrier preferably comprises a metal or a refractory oxide.
6. 6. A catalyst according to any one of claims 3 to 5, characterized in that the atomic ratio of the cation to the catalytically active metal is in excess of or equal to 1.0, more preferably 2.0, more preferably 3.O.
7. 7. A catalyst according to any of claims 3 to 6, characterized in that the metal cation is present in an amount of at least 0.25% by weight based on the total weight of the catalyst, more preferably at least 0.5%, more preferably from 1.25 to 15%.
8. 8. A process for the preparation of carbon monoxide and / or hydrogen from a hydrocarbonaceous raw material, characterized in that it comprises contacting a mixture of the raw material and an oxygen-containing gas with a catalyst according to any one of the claims of 3 to 7.
9. 9. A process according to claim 8, characterized in that the mixture is contacted with the catalyst at a temperature of at least 750 ° C, preferably, in the range of 800 to 1300 ° C, more preferably from 900 to 1200 ° C, at a pressure of up to 150 bara (absolute bar), preferably in the range of 2 to 125 bara, more preferably, from 5 to 100 bara, at a space velocity per hour of gas in the range from 2 0, 0 0 0 to 100,000 Nl / Kg / hr, preferably from .50,000 to 50,000,000 NI (Kg / hr, more preferably, from 500,000 to 30,000,000 Nl / Kg / hr. process according to the rei indication 8 or 9, characterized in that the mixture has a oxygen-to-carbon ratio in the range of 0.3 to 0.8, preferably from 0.45 to 0.75. 11. A process according to any of claims 8 or 9, characterized in that the feed is contacted with the catalyst under substantially adiabatic conditions. - "-« - *.