MXPA97010023A - Catalyst and process for the preparation of hydrocarb - Google Patents

Abstract

The present invention relates to a catalyst for use in a process for the preparation of hydrocarbons, comprising cobalt and manganese and / or vanadium, supported on a support, wherein the atomic ratio of coblate: (magnesium + vanadium) is at minus 12: 1. Preferably, the atomic ratio of cobalt: (manganese + vanadium) is at most 1500: 1. The hydrocarbon preparation comprising contacting a mixture of hydrogen and carbon monoxide at elevated temperature and pressure with a catalyst as described hitherto. Typically, at least part of the cobalt is present in a metallic state.

Description

CATALYST AND PROCESS FOR THE PREPARATION OF HYDROCARBONS Field of the Invention The present invention relates to a catalyst and a process for the preparation of hydrocarbons from synthesis gas, which is a mixture of carbon monoxide and hydrogen.

BACKGROUND OF THE INVENTION The preparation of hydrocarbons from synthesis gas is well known in the art and is commonly referred to as the Fischer-Tropsch synthesis.

Suitable catalysts for use in a Fischer-Tropsch synthesis process typically contain a catalytically active metal of Group VIII of the Periodic Table of the Elements (Manual of Physics and Chemistry, 68th edition, CRC Press, 1987-1988). In particular, iron, nickel, cobalt and ruthenium are well-known catalytically active metals for such catalysts. Cobalt has been found to be the most appropriate to catalyze a process in which the synthesis gas is converted to hydrocarbons mainly paraffinic containing 5 or more carbon atoms. In REF: 026361 other words, the selectivity to C5 + of the catalyst is high.

A great research effort has been directed to find catalysts that have a selectivity higher than C5 + compared to catalysts known to the same or greater activity.

Thus, European Patent Specification No. 398 420, discloses that the selectivity to C5 + of catalysts comprising cobalt and zirconium, titanium or chromium on a porous support, having a small external surface area, can be improved by contacting the catalyst with a synthesis gas having a low ratio of hydrogen to carbon monoxide, typically, from 1.1 to 1.2.

European Patent Specification No. 178 008 discloses cobalt catalysts supported on a porous support, wherein the majority of the cobalt is concentrated in the shell of the catalyst particle.

European Patent Specification No. 167 215 discloses a cobalt / zirconia catalyst on silica, for use in a fixed bed of catalyst, catalyst that satisfies a relationship between the internal surface area and the external surface area.

European Patent Specification No. 168 894, discloses an optimal activation method, to increase the C5 + selectivity of the cobalt base Fischer-Tropsch catalyst.

European Patent Specification No. 363 537 describes an increase in the activity of cobalt catalysts supported on titania, by adding up to 15% by weight of silica to the titania support.

The publication of the European patent application No. 498 976 describes catalysts containing cobalt and rhenium supported on a titania support. It is claimed that these catalysts have a high volumetric productivity (activity).

Regardless of the research effort in this field, there is still room for improvement. In this way, it would be desirable if a catalyst could be found that has an even higher selectivity for C5 + thereto or, preferably, higher activity than the known catalysts.

Surprisingly it has been found that a catalyst comprising as catalytically active components cobalt and a small amount of manganese and / or vanadium, typically comprising an atomic ratio of cobalt: (manganese + vanadium) of at least 12: 1, shows a higher selectivity to Cs + and greater activity when used in a process for the preparation of hydrocarbons, compared to catalysts which are otherwise the same but which contain only cobalt, or which contain a relatively greater amount of manganese and / or vanadium.

The publication of the European patent application No. 71 770, describes a process for the preparation of linear α-olefins from synthesis gas. Among other things, cobalt / manganese and cobalt / vanadium catalysts are claimed as applicable to this process. The C5 + selectivity of a catalyst comprising cobalt and manganese in a ratio of 1: 6 is only 50%.

Van der Riet et al. (1986) J. Chem. Soc., Chem. Commun., Pages 798-799, describes the selective formation of C3 hydrocarbons from carbon monoxide and hydrogen, using cobalt-manganese oxide catalysts. The cobalt / manganese ratio is typically 1: 1.

PCT International Application WO 93/05000 describes a Fischer-Tropsch catalyst comprising cobalt and scandium. Optionally, the catalyst contains additional promoters such as toria and / or other materials such as magnesia and manganese.

"The Fischer-Tropsch and Related Synthesis" by H.H. Storch, N. Golumbic, and R.B. Anderson (John Wiley and Sons, New York, 1951), referred to in the International PCT Application WO 93/05000, provides a review of previous work on Fischer-Tropsch catalysts, including catalysts comprising cobalt and manganese and / or vanadium. On page 120, reference is made to experiments in which it was found that the cobalt-vanadium oxide and cobalt-manganese oxide catalysts were inactive as Fischer-Tropsch catalysts. However, on page 198, reference is made to experiments in which a catalyst containing cobalt and manganese in an atomic ratio of 6.2: 1 has been found to have a higher C5 + selectivity compared to a catalyst containing cobalt and However, at a significantly lower synthesis gas conversion.

Australian patent application No. 46119/85 discloses a catalyst containing cobalt, silica and a base or alkaline material, typically an alkaline or alkaline earth metal. Optionally, additional promoters chosen from salts of elements chosen from the group of aluminum, magnesium, zinc, copper, manganese, chromium, vanadium, germanium, boron, molybdenum, lanthanum, rare earths and the like or combinations thereof, may be present; arsenic or antimony. It is claimed that these catalysts have a high selectivity towards low boiling l-alkenes.

Typically, the catalysts according to the present invention do not contain alkaline or alkaline earth metals, apart from possible impurities introduced with the starting materials in the process of preparing the catalysts of the present invention. Typically, the atomic ratio of the alkali or alkaline earth metals to the metallic cobalt is less than 0.01, preferably less than 0.005.

U.S. Patent Specification No. 4,588,708 describes catalysts containing cobalt and manganese for use in isomerization and hydrogenation of olefins and hydrogenolysis. The atomic ratio of cobalt / manganese can vary widely. In one example, a catalyst containing cobalt and manganese in an atomic ratio of 39: 1 on a silica support has been described.

Detailed Description of the Invention Therefore, according to the present invention, there is provided a catalyst comprising cobalt and manganese and / or vanadium, supported on a support, wherein the cobalt: (manganese + vanadium) atomic ratio is at least 12: 1, with the proviso that the catalyst does not contain cobalt and manganese in an atomic ratio of 39: 1 on a silica support.

According to another aspect, the catalyst comprises cobalt and manganese and / or vanadium, supported on a support, wherein the cobalt: (manganese + vanadium) atomic ratio is at least 12: 1, and wherein the support comprises titania, zirconia or mixtures thereof.

The catalyst preferably comprises cobalt and manganese, wherein the cobalt: manganese atomic ratio is at least 12: 1.

Preferably, the cobalt: (manganese + vanadium) atomic ratio is at most 1500: 1; more preferably at most 500: 1; still more preferably at most 100: 1; more preferably 38: 1.

The cobalt: (manganese + vanadium) atomic ratio is preferably at least 15: 1; more preferably at least 16: 1; still more preferably at least 18: 1.

In a preferred embodiment, the support is a refractory oxide support. Examples of refractory oxide supports include alumina, silica, titania, zirconia or mixtures thereof, such as silica-alumina or physical mixtures such as silica and titania. Preferably the support comprises titania, zirconia or mixtures thereof.

According to a preferred embodiment, the support comprising titania, zirconia or mixtures thereof may further comprise up to 50% by weight of another refractory oxide, typically silica or alumina. More preferably, the additional refractory oxide, if present, comprises up to 20% by weight, even more preferably up to 10% by weight of the support.

The support more preferably comprises titania, in particular titania which has been prepared in the absence of sulfur-containing compounds. An example of such a preparation method involves flame hydrolysis of titania tetrachloride. It will be appreciated that the titania powder derived from said preparation method may not be of the desired size and shape. In this way, usually a forming step is required to prepare the support. The forming techniques are well known to those skilled in the art and include pelletizing, extrusion, spray drying, and hot oil dripping methods.

The amount of cobalt present in the catalyst can vary widely. Typically, the catalyst comprises from 1-100 parts by weight of cobalt per 100 parts by weight of the support, preferably, from 3-60 parts by weight, more preferably, from 5-40 parts by weight.

In addition to manganese and / or vanadium, the catalyst may comprise one or more additional promoters known to those skilled in the art. Preferably any of the additional promoters are selected from Group IIIB, IVB, the noble metals of Group VIII of the Periodic Table or rhenium, niobium or tantalum, more preferably from Group IVB, the noble metals of Group VIII of the Periodic Table or rhenium, niobium or tantalum. Especially preferred additional promoters include zirconium, titanium, ruthenium, platinum, palladium and / or rhenium. The amount of additional promoter, if present, is typically between 0.1 and 150 parts by weight, for example between 1 and 150 parts by weight, per 100 parts by weight of the support.

The catalyst according to the present invention may be suitably prepared by methods known to those skilled in the art, such as by precipitation of catalytically active compounds or precursors on a support; coating by atomization, kneading and / or impregnation of the catalytically active compounds or precursors on the support; and / or the extrusion of one or more catalytically active components or precursors, together with the support material for preparing catalyst extrudates.

It will be appreciated by those skilled in the art that the most preferred method of preparation may vary, depending for example on the desired size of the catalyst particles. It belongs to the ability of the skilled person to select the most appropriate method for a given set of circumstances and requirements.

A preferred catalyst preparation method according to the present invention is by impregnating the catalytically active compounds or precursors on top of the support. Thus, the support is typically impregnated with a solution of a cobalt salt and a vanadium and / or manganese salt. Preferably, the support is impregnated simultaneously with the respective metal salts. Then, according to a preferred embodiment, the process for preparing the catalyst according to the present invention comprises the co-impregnation of the support with a solution of a cobalt salt and a vanadium and / or manganese salt. In case a catalyst containing cobalt and manganese is prepared, a highly concentrated solution is most preferably employed. An appropriate method to reach said concentrated solution is to use a mixture of molten cobalt nitrate salts and manganese nitrate.The impregnation treatment is typically followed by drying and, optionally, by calcining. Drying is typically carried out at a temperature of 50 to 300 ° C for up to 24 hours, preferably 1 to 4 hours.

The calcination is typically carried out at a temperature between 200 and 900 ° C, preferably between 250 and 600 ° C. The duration of the treatment by calcination is typically from 0.5 to 24 hours, preferably from 1 to 4 hours. Suitably, the treatment by calcination is carried out in an atmosphere containing oxygen, preferably air. It will be appreciated that the average temperature during the treatment by calcination will normally be higher than the average temperature during the drying treatment.

The catalyst according to the present invention is typically used to catalyze a process for the preparation of hydrocarbons from synthesis gas.

Typically when used in that process, at least part of the cobalt is present in its metallic state.

Therefore, it is normally advantageous to activate the catalyst before use, by a reduction treatment, in the presence of hydrogen at an elevated temperature. Typically, the treatment by reduction, involves the treatment of the catalyst at a temperature in the range from 100 to 450 ° C for 1 to 48 hours at elevated pressure, typically from 1 to 200 absolute bars. Pure hydrogen can be used in the reduction treatment, but it is usually preferred to apply a mixture of hydrogen and an inert gas such as nitrogen. The relative amount of hydrogen present in the mixture may be between 0 and 100% by volume.

In accordance with a preferred embodiment, the catalyst is brought to the desired pressure and temperature level in a nitrogen gas atmosphere. Subsequently, the catalyst is contacted with a gas mixture containing only a small amount of hydrogen gas, the remainder being nitrogen gas. During the reduction treatment, the relative amount of hydrogen gas in the gas mixture is gradually increased to 50% or even 100% by volume.

If possible, it is preferred to activate the catalyst in-situ, that is, inside the reactor. European patent application No. 95203040.1 describes an activation process of an in-situ catalyst, which comprises contacting the catalyst in the presence of a liquid hydrocarbon with a hydrogen-containing gas, at a hydrogen partial pressure of at least 15. absolute bars, preferably at least 20 absolute bars, more preferably at least 30 absolute bars. Typically, in this process, the partial pressure of hydrogen is at most 200 absolute bars.

In a further aspect, the present invention relates to a process for the preparation of hydrocarbons, comprising contacting a mixture of carbon monoxide and hydrogen at elevated temperature and pressure with a catalyst as described hereinabove, typically comprising cobalt and vanadium and / or manganese, where the atomic ratio of cobalt: (manganese + vanadium) is at least 11: 1.

The process is typically carried out at a temperature in the range from 125 to 350 ° C, preferably 175 to 275 ° C. The pressure is typically in the range from 5 to 150 absolute bars, preferably from 5 to 80 absolute bars, in particular from 5 to 50 absolute bars.

Hydrogen and carbon monoxide (synthesis gas) are typically fed to the process at an atomic ratio in the range from 1 to 2.5. It is known that low atomic ratios of hydrogen to carbon monoxide will increase the C5 + selectivity of the Fischer-Tropsch catalysts. It has now been found more surprisingly that the C5 + selectivity of the catalyst according to the present invention is considerably high, even when a synthesis gas having a high atomic ratio of hydrogen to carbon monoxide is used. In a preferred embodiment of the hydrocarbon synthesis process of the present invention, the atomic ratio of hydrogen to carbon monoxide ranges from 1.5 to 2.5.

The space gas speed can vary within wide ranges, and is typically in the range from 400 to 10000 Nl / l / h, for example, from 400 to 4000 Nl / l / h.

The process for the preparation of hydrocarbons can be carried out using a variety of reactor types and reaction regimes, for example a fixed bed regime, a suspended phase regime or an ebullient bed regime. It will be appreciated that the size of the catalyst particles may vary depending on the reaction regime for which they are used. It belongs to the ability of the skilled person to select the most appropriate particle size of catalyst for a given reaction regime.

In addition, it will be understood that the skilled person is able to select the most appropriate conditions for a specific reactor configuration and reaction regime. For example, the preferred gas hour speed space may depend on the type of reaction regime that is being applied. Then, if it is desired to operate the hydrocarbon synthesis process with a fixed bed regime, the preferred gas hour speed space is chosen in the range from 500 to 2500 Nl / l / h. If it is desired to operate the hydrocarbon synthesis process with a regime in phase in suspension, the gas speed space is chosen in the range from 1500 to 7500 Nl / l / h.

The invention will now be further illustrated by means of the following Examples.

EXAMPLE 1 (comparative) Commercially available titania particles (30-80 mesh) of the rutile variety were impregnated with a concentrated solution of cobalt nitrate.

The solution was prepared by heating solid cobalt nitrate (Co (N03) 2.6H20) to a temperature of 60 ° C, thus causing the cobalt nitrate to dissolve in its own crystal water. The particles impregnated with titania were dried for 2 hours at 120 ° C and then calcined in air for 4 hours at 400 ° C. The catalyst (I) thus produced contained 10% by weight of cobalt compounds, expressed as metallic cobalt.

EXAMPLE II The procedure of Example I was repeated but now the impregnating solution also contained manganese nitrate. The solution was prepared in the same manner as that described in Example I, but part of the solid cobalt nitrate was replaced by manganese nitrate (Mn (N03) 2.4H20).

The catalyst (II) contained 10% by weight of metal compounds, expressed as metal. The cobalt: manganese atomic ratio totaled 20: 1.

EXAMPLE III (comparative) The procedure of Example II was repeated, but the impregnating solution contained more manganese nitrate. The catalyst (III) contained 10% by weight of metal compounds, expressed as metal. The atomic ratio of cobalt: manganese totaled 10: 1.

EXAMPLE IV Catalysts I, II and III were tested in a process for the preparation of hydrocarbons. Microfluid reactors A, B and C, containing 10 grams of catalysts I, II and III respectively, were heated to a temperature of 260 ° C, and pressurized with a continuous flow of nitrogen gas to a pressure of 2 bar abs. The catalysts were reduced in-situ for 24 hours with a mixture of nitrogen and hydrogen gas. During the reduction, the relative amount of hydrogen in the mixture gradually increased from 0% to 100%. The concentration of water in the outlet gas was kept below 3000 ppmv.

After the reduction, the pressure was increased to 26 bar abs. The reaction was carried out with a mixture of hydrogen and carbon monoxide at an atomic ratio of H2 / C0 of 2: 1, and a temperature of 200 ° C. The GHSV totaled 800 Nl / l / h.

The space-time yield (STY), expressed as grams of hydrocarbon product per liter of catalyst per hour, and the C5 + selectivity, expressed as percentage by weight of the total product of hydrocarbons, was determined for each of the reactors after 100 hours of operation.

The results are set forth in Table I.

TABLE I Reactor: A B C Catalyst I (without Mn) II (Co / Mn = 20) III (Co / Mn = 10) STY (g / l / h) 70 100 65 Selectivity 89 91 87 C5 + (%) It will be appreciated that the activity and selectivity of catalyst II, according to the invention, is much better than the activity and selectivity of catalysts I and III, which do not follow the invention.

Accordingly, in a further aspect, the invention relates to the use of manganese and / or vanadium for the purpose of increasing the C5 + activity and / or selectivity of a cobalt-containing catalyst in a process for the preparation of hydrocarbons.

It is noted that in relation to this date, the best known method for carrying out the invention is that which is clear from the present description of the invention.

Having described the invention as above, property is claimed as contained in the following

Claims (10)

1. A catalyst comprising cobalt and manganese and / or vanadium, supported on a support, characterized in that the atomic ratio of cobalt: (manganese + vanadium) is at least 12: 1, with the proviso that the catalyst does not contain cobalt and manganese in an atomic ratio of 39: 1 on a silica support.

2. A catalyst comprising cobalt and manganese and / or vanadium, supported on a support, characterized in that the cobalt: (manganese + vanadium) atomic ratio is at least 12: 1, and wherein the support comprises titania, zirconia or mixtures thereof .

3. The catalyst according to claims 1 or 2, characterized in that the cobalt: (manganese + vanadium) atomic ratio is at least 15: 1.

. The catalyst according to claims 1 to 3, characterized in that the cobalt: (manganese + vanadium) atomic ratio is at most 1500: 1.

5. The catalyst according to any of the preceding claims, characterized in that at least part of the cobalt is in the metallic state.

6. A process for the preparation of a catalyst according to any of claims 1 to 4, characterized in that it comprises impregnation of the support with a solution of a cobalt salt and a solution of a manganese and / or vanadium salt, followed by drying and, optionally, calcined.

7. The process according to claim 6, characterized in that it comprises the co-impregnation of the support with a solution of a cobalt salt and a manganese and / or vanadium salt.

8. The process for the preparation of a catalyst according to claim 5, characterized in that it comprises subjecting the catalyst of any of claims 1 to 4 to a reduction treatment in the presence of hydrogen.

9. A process for the preparation of hydrocarbons, characterized in that it comprises contacting a mixture of carbon monoxide and hydrogen at elevated temperature and pressure with a catalyst as claimed in claim 5.

10. The use of a catalyst according to any of claims 1 to 5 in a process for the preparation of hydrocarbons.