RU2137702C1 - Method for catalytic partial oxidation of hydrocarbons - Google Patents

Abstract

FIELD: petrochemical synthesis. SUBSTANCE: invention, in particular, concerns production of carbon monoxide- hydrogen mixture from methane-containing raw material. Mixture of the latter with oxygen-containing gas at oxygen-to-carbon ratio between 0.3 and 0.8 is brought into contact with catalyst containing VIII group metal at temperature above 900 C and elevated pressure. According to invention, catalyst is carried by refractory metal oxide including at least two cations and contact is effected at flow rate from 500000 to 30000000 nl/kg hr. EFFECT: increased conversion of hydrocarbon raw and improved selectivity. 13 cl, 2 tbl, 5 ex

Description

 The present invention relates to a method for the catalytic partial oxidation of hydrocarbons, in particular to a method for producing a mixture of carbon monoxide and hydrogen from a methane-containing feedstock, for example natural gas or a corresponding gas.

 Partial oxidation of hydrocarbons, such as methane or natural gas, in the presence of a catalyst is an effective way to produce mixtures of carbon monoxide and hydrogen, known as synthesis gas. The resulting mixture can be converted into valuable hydrocarbon products, for example fuel with a boiling point within the middle boiling point, and hydrocarbon paraffins by methods such as, for example, Fischer-Tropsch synthesis, well known in the art.

 Or the mixture can be converted into products such as, for example, methanol, by known methods of synthesis.

 The optimal method of catalytic partial oxidation for industrial applications provides high levels of conversion of hydrocarbon feedstock with a high selectivity for carbon monoxide and hydrogen.

State of the art
There are many documents in the literature that disclose details of experiments conducted in the catalytic partial oxidation of hydrocarbons, in particular methane, using various catalysts. Typically, these catalysts contain an active metal selected from group VIII of the Periodic Table of Elements (CAS variant, as described in the Handbook of Chemistry and Physics, 68th edition), which is supported by a carrier based on refractory material such as alumina or silica.

 In European application N 0262947 (EP - A - 0262947) a method for the catalytic partial oxidation of methane using a catalyst containing platinum and chromium oxide and supported on a support made of an oxide of refractory material is disclosed. The catalyst specifically disclosed in EP-A-0262947 contains silicon dioxide as a carrier material.

Ashcroft A.T. and others ("Selective oxidation of methane to produce synthesis gas using transition metal catalysts," Nature, Volume 344, N 6264, pp. 319-321, March, 1990) describe experiments using lanthanide and ruthenium oxides of the formula Ln ₂ Sn ₂ O ₇ for the partial oxidation of methane. A number of lanthanides were tested at a temperature of 777 ^° C., a gas hourly space velocity of 40,000 h ⁻¹ and a pressure of 1 atm. The authors concluded that under the existing process conditions, the active catalyst contained a ruthenium metal supported on a metal oxide support.

Similarly, Jones R. Kh. And others ("Catalytic Conversion of Methane to Syngas over Europium Iridate, Eu ₂ Ir ₂ O ₇ ", Catalysis Zetters 8 (1991) 169-174) describe selective partial oxidation of methane over europium-iridium pyrochlore , Eu ₂ Ir ₂ O ₇ at a pressure of 1 atm. and a temperature of 873 K (600 ^o C). It was shown that the active catalyst contained iridium metal particles supported on europium oxide. Similar results are disclosed by Vernon P.D.F. and others ("Partial Oxidation of Methane to Syngas", Catalysis Zetters 6, (1990) 181-186, and Catalysis Today, 13 (1992) 417-426) for nickel, ruthenium, rhodium, palladium, iridium, and platinum on supports from alumina or present as metals in oxides derived from mixed oxide precursors.

US patent N 5149464 generally relates to a method for the selective oxidation of methane to produce carbon monoxide and hydrogen by contacting the gas mixture of the reagent at a temperature of about 650 - 900 ^o C with a solid catalyst, which is generally described as:
a) a catalyst of the formula M _x M ' _y O _z , where:
M is at least one element selected from Mg, B, Al, Ln, Ga, Si, Ti, Ir and Hf;
Ln is at least one element selected from lanthanum and a group of lanthanide elements;
M '- d-block is a transition metal, and each of the ratios x / y and y / z and (x + y) / z is equal to independently from 0.1 to 8; or
b) d-block oxide is a transition metal; or
c) d-block - transition metal on a refractory carrier; or
d) a catalyst obtained by heating a) or b) under reaction conditions or under non-oxidizing conditions.

 As indicated in US Pat. No. 5,149,464, d-block transition metals are selected from those having an element serial number of 21-29, 40-47, 72-79, i.e., metals — scandium, titanium, vanadium, chromium, manganese, iron , cobalt, nickel, copper, zirconium, niobium, molybdenum, technetium, ruthenium, palladium, silver, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum and gold.

 US Pat. No. 5,149,464 teaches that the preferred metals are Group VIII metals in the Periodic Table of the Elements, i.e., iron, osmium, cobalt, rhenium, iridium, palladium, platinum, nickel and ruthenium.

The method described in US Pat. No. 5,149,464 is carried out at a temperature in the range of 650 ^° C. to 900 ^° C., with a temperature range of 700-800 ^° C. being preferred. US Pat. No. 5,149,464 describes a series of experiments in which various catalysts containing Group VIII metals were tested. including ruthenium oxide, praseodymium / ruthenium oxides, pyrochlore, ruthenium on alumina, nickel /, alumina, perovskites and nickel oxide.

A similar general description of the catalyst for use in the catalytic partial oxidation method is presented in International Application WO N 92/11199. WO 92/11199 specifically describes experiments in which catalysts containing iridium, palladium, ruthenium, rhodium, nickel and platinum supported on an alumina support were used. All experiments were carried out under mild process conditions, with typical conditions being a pressure of 1 atm, a temperature of 1050 K (777 ^° C), and a gas hourly space velocity of approximately 20,000 / hour. The patent specification WO 92/11199 states that catalysts were tested to determine their service life and that most catalysts, as expected, did not show a decrease in activity after 80 hours and possibly significantly longer.

Japanese Patent No. 58-207946 discloses a catalyst for the partial oxidation of hydrocarbons, which comprises a combination of spinel alumina-magnesium oxide, cobalt aluminate, barium carbonate and barium aluminate or a combination of spinel alumina-magnesium oxide, cobalt, cobalt oxide and barium aluminate . Japanese Patent No. 58-207946 teaches that this catalyst is suitable for the partial oxidation of hydrocarbons, for example natural gas, methane, ethane, propane and butane. However, Japanese Patent No. 58-207946 relates generally to a method for producing a gas containing carbon monoxide and hydrogen for surface hardening of steel. In this regard, the examples presented in Japanese Patent No. 58-207946 are limited to the partial oxidation of butane to produce a mixture of carbon monoxide and hydrogen having a hydrogen / carbon monoxide ratio of about 1.3. The experiments were carried out at a space velocity of 12,000 h ^-1 , using a mixture of air and butane as a feedstock, while the amount of air exceeded the theoretical amount 1.025 times necessary for the oxidation of butane to carbon monoxide and hydrogen (i.e., the ratio of oxygen / carbon equal to 0.51). Japanese Patent No. 58-207946 does not indicate an appropriate operating pressure for a partial oxidation process. In Japanese patent N 58-207946 it is indicated that the catalysts allow the partial oxidation process to be carried out with good efficiency at low temperatures, that is, below 1000 ^° C. For this purpose, all experiments on testing the catalysts were carried out at a temperature of 980 ^° C.

 Finally, International Application WO N 93/01130 discloses a method for the partial oxidation of methane using a catalyst containing a platinum group metal and / or metal oxide on a support of lanthanide oxide and / or metal oxide from group III B and / or metal oxide from Group IV B in the Periodic Table and / or from alumina. WO 93/01130 describes a series of experiments in which catalysts were used consisting of palladium supported on a support of scandium, yttrium, lanthanum, titanium, zirconium, hafnium, cerium, samarium, aluminum, silicon and mixed barium / cerium oxides and strontium / cerium.

The experiments were carried out at a temperature of 750 ^o C and at a gas hourly space velocity of 5000 h ^-1 , while a feedstock of 45% methane: 5% oxygen: 55% argon was used. WO 93/01130 does not indicate operating pressure. The results disclosed in WO 93/01130 show that, under selected operating conditions, catalysts having supports consisting of metal oxide from groups III B or IV B of the Periodic Table, aluminum and cerium lanthanide, showed high selectivity for carbon monoxide instead of forming large amounts of carbon dioxide.

 As already mentioned, an important method for industrial applications is to obtain mixtures of carbon monoxide and hydrogen, which are then used as feedstock for the process of hydrocarbon or organic chemical synthesis.

 The catalytic partial oxidation of hydrocarbons is one possible way to obtain these mixtures. However, for the method to be effective for industrial applications, it is necessary that it be carried out at elevated pressure, for example from 30 to 150 bar, and at a very high hourly space velocity of the gas, for example of the order of 1,000,000 N l / kg / h For reasons of thermodynamics, in order to achieve the required selectivity for carbon monoxide and hydrogen, it is necessary to carry out the partial oxidation method at high temperatures. Therefore, for a partial oxidation process carried out on an industrial scale, it is essential that the catalyst used maintains its level of activity and selectivity for the desired products over long periods of work required for industrial processes.

 Also the most preferred mixture of carbon monoxide and hydrogen for use as a feedstock for an industrial-scale synthesis process, for example the synthesis of paraffins or methanol, according to the Fischer-Tropsch process, is a mixture having a ratio of hydrogen to carbon monoxide of about 2.0. Such a mixture can be obtained by partial oxidation of methane or a methane-containing feedstock, for example natural gas or a corresponding gas.

 So, we can see that there is a need for a method for the catalytic partial oxidation of methane or methane-containing feedstock, in which the catalyst maintains a high level of activity and selectivity for carbon monoxide and hydrogen under conditions of high space velocity, high pressure and high temperature. In contrast to solutions in well-known documents, in particular in International Application WO 93/01130, it was unexpectedly discovered that a method in which catalysts containing a metal selected from group VIII of the Periodic Table of Elements are supported on a support of refractory oxide having at least at least two cations, provides both carbon monoxide and hydrogen in the above conditions, and with high yield for an extended period of time.

Description of the invention
Thus, the proposed method in accordance with the present invention for the catalytic partial oxidation of methane-containing starting material, which consists in contacting a mixture of feedstock and oxygen-containing gas, and the mixture has a ratio of oxygen to carbon in the range of 0.3-0.8 at temperatures above 900 ^o C and at elevated pressure with a catalyst comprising a metal selected from group VIII of the Periodic table of elements, supported on a refractory oxide having at EPE two cations.

 The method in accordance with the present invention is suitable for producing a mixture of carbon monoxide and hydrogen from any metal-containing raw material. However, a typical feed will contain methane in combination with one or more other hydrocarbons and gases. The feedstock preferably contains methane in an amount of at least 50% by volume, better than 75% by volume, and even better 80% by volume. Methane may be in combination with other hydrocarbons, for example light hydrocarbons having 2-4 carbon atoms. The method is particularly suitable for partial oxidation of natural gas and the corresponding gas.

 The feedstock is contacted with the catalyst as a mixture with an oxygen-containing gas. Air is suitable as an oxygen-containing gas. However, it is best to use substantially pure oxygen as an oxygen-containing gas. Thus, the need for a large volume of inert gas, for example nitrogen, is eliminated when air is used as the oxygen-containing gas. Feedstock may contain steam.

The methane-containing feed and the oxygen-containing gas are mixed in such an amount as to obtain an oxygen to carbon ratio in the range of 0.3-0.8, more preferably in the range of 0.45-0.75. The reference to the ratio of oxygen to carbon refers to the ratio of oxygen in the form of molecules (O ₂ ) to carbon atoms present in the methane-containing feed. Preferably, the oxygen to carbon ratio is in the range of 0.45-0.65, and the oxygen to carbon ratio in the region of the stoichiometric ratio of 0.5, which is in the range of 0.45-0.6, is particularly preferred. If steam is present in the feed, then the ratio of the vapor content to the carbon content is in excess of 0.0-3.0, preferably in the range of 0.0-2.0. The methane-containing feed, oxygen-containing gas and steam, if present, are preferably mixed well before contact with the catalyst.

 The method in accordance with the present invention is carried out at elevated pressure, which is significantly higher than atmospheric pressure. The method can be carried out under pressure up to 150 bar. More preferably, the method is carried out under pressure in the range of 5-100 bar, especially 10-75 bar.

Under the high pressure existing in the process, the feed must be in contact with the catalyst at high temperatures to achieve the desired degree of conversion. Thus, the mixture of methane-containing feed and oxygen-containing gas is in contact with the catalyst at temperatures above 900 ^o C, preferably in the range from 1000-1300 ^o C, and even better 1000-1200 ^o C. Prior to contacting with the catalyst, the methane-containing feed and oxygen-containing gas are preferably preheated . A mixture of methane-containing feed and oxygen-containing gas can be supplied during the process at any appropriate space velocity. An advantage of the method in accordance with this invention is that very high gas space velocities can be achieved. So, typical gas hourly space velocities for this method (expressed in normal liters of gas per kg of catalyst per hour) are in the range of 20,000-100000000 normal liters / kg / hour, more preferably from 50,000 to 50,000,000 normal liters / kg / hour. A space velocity in the range of 500,000-30000,000 normal liters / kg / h is particularly preferred.

 The catalyst used in the method in accordance with the present invention contains a metal of group VIII of the Periodic table of the elements supported on the oxide of the refractory material containing at least two cations. The catalyst has a structure formed by the deposition of a metal of group VIII on a substrate of oxide of refractory material, for example, by impregnation. Thus, the catalysts contain a Group VIII metal on the surface of a refractory oxide support. This structure is the opposite of the structure formed by the use of the catalysts described in the known technical solutions in which the refractory oxide is applied directly in the process of partial oxidation, the existing conditions in which the oxides present in the refractory material are reduced to the corresponding metal, which is catalytically active.

 The catalyst contains a Group VIII metal in the Periodic Table of Elements, with a metal selected from ruthenium, rhodium, palladium, osmium, iridium and platinum being preferred. Catalysts containing ruthenium, rhodium or iridium as a catalytically active metal are particularly preferred for use in the present process.

 Group VIII metal is supported on a support made of an oxide of refractory material that contains at least two cations. The oxide of the refractory material is a double go triple oxide consisting of two or three cations, respectively, with double oxides being preferred. Each of two or more cations of the oxide of the refractory material is preferably selected from groups IA, IIA, IIIA and IVA in the Periodic table of the elements or from transition metals. More preferably, each of two or more cations is selected from groups IA, IIA, IIIA, IIIB, IVA and IVB and lanthanides. A preferred catalyst contains refractory oxide having at least one cation selected from groups IA, IIA and IIIB and lanthanides, and at least one cation selected from groups IIIA, IVA and IVB. More preferably, the catalyst comprises a refractory oxide having at least one cation from group IIIA or IVB. Barium is a particularly preferred cation selected from group IIA. Aluminum is a particularly preferred cation selected from group IIIA. Lanthanum is the most preferred cation selected from group IIIB. Zirconium is the most preferred cation selected from group IVB. One most preferred oxide of a refractory material for use as a support in a catalyst is barium and aluminum double oxide, in particular barium hexaaluminate. Another, most preferred refractory oxide for use as a support in a catalyst is lanthanum and zirconium double oxide.

 Refractory oxide materials for use as supports in catalysts are commercially available or can be prepared by known methods.

 The catalyst can be prepared by known methods, of which impregnation is the preferred method. The method of preparing the catalyst by impregnation consists in contacting the refractory oxide with a solution of a Group VIII metal salt in the Periodic Table of the Elements. Then, the impregnated refractory oxide is dried and calcined.

 In the method in accordance with the present invention, any reaction mode may be used to contact the reactants with the catalyst. One appropriate mode is a fluidized bed in which a catalyst is used in the form of particles fluidized by a gas stream. The preferred reaction mode for use in the method is the reaction mode in the fluidized bed, in which the catalyst is held inside the reaction zone in a stationary position. In the fixed-bed mode, the catalyst particles can be held using known fixed-bed reaction methods. Or, the catalyst may be in the form of a foam prepared, for example, by impregnating the foam ceramic from refractory oxide in the manner described. Suitable foams for use in the preparation of the catalyst include those that have 30 to 150 pores per inch (12-60 pores per centimeter). Other forms of catalyst also include honeycomb monolithic structures.

 In a specific embodiment of the method in accordance with this invention, the feedstock is contacted with a catalyst held in a fixed bed, which has a high tortuosity. The term “tortuosity” is a term known in the art that when it refers to a fixed catalyst bed, can be defined as the ratio of the path length occupied by the gas passing through the bed to the shortest direct path through the bed. Thus, honeycomb monolithic structures have a sinuosity of 1.0. For the purposes of the present invention, the term “high tortuosity” refers to devices having a tortuosity substantially greater than that of honeycomb monolithic structures, in particular tortuosity of at least 1.1. The fixed bed of catalyst particles typically has a tortuosity of 1.5, so that ceramic foams having a tortuosity in the range of 3.0-4.0 or even higher can be obtained. In general, the tortuosity of a fixed-bed device is preferably in the range of 1.1-10.0, and preferably 5.0. The most appropriate tortuosity range is from 1.3 to 4.0.

 It has been established that the use of a catalyst in a device with a fixed bed having a high tortuosity makes it possible to achieve the desired conversion only with a relatively very short contact time between the reaction gases and the catalyst. Thus, only a very small catalyst is required, which, in turn, makes it possible to achieve the very high space velocities required to carry out the process on an industrial scale.

 The feed is preferably contacted with the catalyst under adiabatic conditions. For the purposes of this description, the term “adiabatic” refers to reaction conditions under which substantially all heat loss and radiation from the reaction zone are excluded except for the heat remaining in the gaseous effluent from the reactor.

 According to another aspect, the present invention relates to carbon monoxide or hydrogen obtained by the described method.

 The mixture of carbon monoxide and hydrogen obtained by the method in accordance with this invention is particularly suitable for use in the synthesis of hydrocarbons, for example, by the Fischer-Tropsch synthesis or the synthesis of oxygenates, for example methanol. Methods for converting a mixture of carbon monoxide and hydrogen into such products are well known in the art.

 The method in accordance with the invention is further illustrated by the following examples, of which examples 1, 3 and 4 relate to the method in accordance with the present invention, and examples 2 and 5 are presented only for comparison purposes.

Example 1
Catalyst Preparation
Barium - hexa - aluminate (BaAl ₁₂ O ₁₉ ) was prepared as follows.

Barium (21.0 g) was added to isopropyl alcohol (1500 ml) in a nitrogen atmosphere and the charged mixture was heated under irrigation for 1.5 hours. More isopropyl alcohol (1000 ml) was added to the resulting solution. After that, aluminum isopropylate (379.65 g) was gradually added and the mixture was heated under irrigation conditions for 5 hours. The resulting mixture (601.87 g) was combined with demineralized water (22.5 g) and heated with irrigation, while the mixture was stirred for an additional 1 hour. The resulting solution was then heated to evaporate the solvent to leave a solid precipitate. The solid was dried by heating to a temperature of 450 ^o C for 4 hours and maintained at this temperature for 1 hour, and in the second stage to a temperature of 1300 ^o C for 1 hour and maintained at this temperature for 5 hours.

An aqueous solution was prepared by dissolving rhodium chloride (RhCl ₃ , 2.0 g) and hydrochloric acid (37%, 1.0 g) in demineralized water (6.83 g) to obtain a rhodium concentration of 10% by weight. Barium-hexa-aluminate obtained by the described method (30/80 mesh, 2.0 g) was immersed in the aforementioned aqueous solution (1.07 g). The resulting mixture was first mixed in a roller mill for 1 hour and then in a drum dryer for 1 hour. The resulting material was dried in a dryer by heating for 1 hour and maintained at a temperature of 120 ^o C for 5 hours, then calcined by heating for 5 hours and maintained at a temperature of 500 ^o C for 1 hour. The resulting catalyst contained 5.0 wt.% Rhodium.

Catalytic partial oxidation
A reactor was made containing a transparent sapphire tube mounted concentrically inside the outer transparent polycarbonate tube. The rhodium-containing catalyst prepared by the described method was loaded into a sapphire tube and held therein in the form of a fixed layer of catalyst particles having a sinuosity of 1.5. A sufficient amount of methane and oxygen to obtain an oxygen to carbon ratio of 0.59 was thoroughly mixed before being introduced into the reactor for contact with a fixed catalyst bed. A mixture of methane and oxygen was fed into the reactor under a pressure of 5 bar and at a gas hourly space velocity (GHSV) of 1240000 normal liters / kg / h. The operating temperature in the catalyst bed was measured by optical pyrometry. The composition of the gas mixture leaving the reactor was measured by gas chromatography. The conversion and selectivity of the method for carbon monoxide and hydrogen (based on converted methane) were determined. The operating conditions of the reactor and the experimental results are presented in table 1.

Example 2
Catalyst Preparation
An aqueous solution containing rhodium chloride was prepared as described in Example 1. The solution contained rhodium in an amount of 10% by weight. Alpha alumina extrudates (commercially available as supplied by the company Engelhard in crushed form to a size of 30/80 mesh, 10.0 grams) were immersed in the above solution (5.33 g). The resulting mixture was first stirred in a roller mill for 1 hour and then for 1 hour in a drum dryer. The resulting material was dried in a dryer by heating for 1 hour, maintained at a temperature of 120 ^° C. for 5 hours, then calcined by heating for 5 hours and maintained at a temperature of 500 ^° C. for 1 hour. The resulting catalyst contained 5.0 wt.% Rhodium.

Catalytic partial oxidation
The catalyst prepared as described was loaded into the device and tested for activity in the partial oxidation of methane, using the method described in example 1. The operating conditions of the reactor and the experimental results are presented in table 1.

Example 3
A catalyst containing 5.0 wt.% Rhodium on a barium-hexa-aluminate substrate was prepared as described in Example 1. The catalyst was loaded into a device and tested for activity in the catalytic partial oxidation of methane, using the same method as the general method. described in example 1. The operating conditions of the reactor and the experimental results are presented in table 2.

Example 4
Catalyst Preparation
Lanthanum zirconate (La ₂ Zr ₂ O ₇ ) was prepared as follows. Lanthanum nitrate (La (NO ₃ ) ₃ • 6H ₂ O, 27.07 g) and zirconium chloride (ZrOCl ₂ • 8H ₂ O, 20.14 g) were dissolved in demineralized water (200 ml). Citric acid (30 g) was added to the resulting solution. The resulting mixture was heated to evaporate the solvent, while solid material remained in the form of a precipitate. The solid material was dried by heating to a temperature of 700 ^o C for 5 hours and maintained at this temperature for 2 hours. Finally, the solid material was heated for 5 hours at a temperature of 1100 ^o C.

An aqueous solution containing rhodium chloride was prepared as described in Example 1. The solution contained rhodium in an amount of 10% by weight. Lanthanum zirconate obtained by the described method (1.4 g) was loaded into the above solution (1.7 ml). The resulting mixture was first mixed in a roller mill for 1 hour and then in a drum dryer for 1 hour. The resulting material was dried in a dryer by heating for 1 hour, maintained at a temperature of 120 ^o C for 5 hours, calcined by heating for 5 hours and kept at a temperature of 500 ^o C for 1 hour. The resulting catalyst contained 5.0 wt. % rhodium.

Catalytic partial oxidation
The catalyst prepared by the described method was loaded into the device and tested for activity in the partial oxidation of methane using the method described in example 1. The operating conditions of the reactor and the experimental results are presented in table 2.

Example 5
The catalyst containing 5.0 wt. % rhodium on an alpha alumina support was prepared as described in Example 2. The catalyst was loaded into the device and tested for activity in the catalytic partial oxidation of methane, using the same general method as in Example 1. The operating conditions of the reactor and the experimental results are presented in table 2.

Claims (13)

1. A method for the catalytic partial oxidation of a methane-containing feedstock, comprising contacting a mixture of feedstock and an oxygen-containing gas with an oxygen to carbon ratio in the range of 0.3 - 0.8 at a temperature above 900 ^° C and elevated pressure with a catalyst containing a metal selected from group VIII of the Periodic table of the elements, which is supported on oxide refractory material having at least two cations, characterized in that the contacting of the mixture of the feedstock and oxygen-containing g for the catalyst is carried out at a space velocity of from 500,000 to 30,000,000 Nl / kg / h.  2. The method according to claim 1, characterized in that the methane-containing feedstock includes methane in an amount of at least 50 vol.%, Preferably at least 80% by volume.  3. The method according to claim 1 or 2, characterized in that the methane-containing feedstock is natural gas or the corresponding gas.  4. The method according to any one of claims 1 to 3, characterized in that the mixture includes methane-containing raw materials and oxygen-containing gas in an amount sufficient to obtain an oxygen to carbon ratio in the range 0.45 - 0.75, preferably 0.45 - 0.65.  5. The method according to any one of claims 1 to 4, characterized in that the mixture is contacted with the catalyst under pressure in the range of up to 150 bar, preferably in the range of 5 - 100 bar, and preferably 10 - 75 bar. 6. The method according to any preceding paragraph, characterized in that the mixture is contacted with a catalyst at a temperature in the range of 1000 - 1300 ^o C, preferably 1000 - 1200 ^o C.  7. The method according to any preceding paragraph, characterized in that the metal selected from group VIII of the Periodic Table of the Elements is ruthenium, rhodium, palladium, osmium, iridium or platinum, with ruthenium, rhodium or iridium being preferred.  8. The method according to any preceding paragraph, characterized in that the refractory oxide is a double or triple oxide, preferably a double oxide.  9. The method according to any preceding paragraph, characterized in that the refractory oxide contains two or more cations, each selected from groups IA, IIA, IIIA, IIIB and IVA and transition metals, preferably from groups IA, IIA, IIIA, IIIB, IVA and IVB and lanthanides.  10. The method according to claim 9, characterized in that the refractory oxide contains one cation selected from groups IA, IIA and IIIB, and at least one cation selected from groups IIIA, IVA and IVB, and preferably one cation from the group IIA or IIIB and at least one cation is from group IIIA or IIB.  11. The method according to p. 10, characterized in that the refractory oxide contains a double oxide of barium and aluminum or a double oxide of lanthanum and zirconium.  12. The method according to any preceding paragraph, characterized in that the catalyst is held in a device with a fixed layer, and the device with a fixed layer has a high tortuosity, more preferably in the range from 1.1 to 5.0.  13. A mixture of carbon monoxide and hydrogen, characterized in that it is obtained by the method according to claims 1 to 12.

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