MXPA98003451A - Process of activation and renewal of a catalyst - Google Patents

Abstract

The present invention relates to a process for activating or renewing a catalyst in the presence of a hydrocarbon liquid, such a catalyst comprising a metal compound of Group Ib, VIIb or VII, by contacting the catalyst with a gas containing hydrogen at a partial pressure of hydrogen of at least 15 bar abs. The present invention further relates to a hydrocarbon synthesis process, which comprises activating or renewing a hydrocarbon synthesis catalyst in the presence of a hydrocarbon liquid, contacting the catalyst with a hydrogen-containing gas at a partial pressure of hydrogen of at least 15 bar abs, and then contacting the catalyst with a mixture of hydrogen and carbon monoxide under hydrocarbon synthesis reaction conditions

Description

PROCESS DB ACTIVATION AND RENEWAL OF A CATALYST FIELD OF THE INVENTION The present invention relates to a process for the activation or renewal of a catalyst, in particular to a hydrocarbon synthesis catalyst, with a gas containing hydrogen in the presence of a hydrocarbon liquid.

BACKGROUND OF THE INVENTION Hydrocarbon synthesis catalysts, ie, catalysts capable of catalyzing the synthesis of hydrocarbons from hydrogen and carbon monoxide (for example, Fischer-Tropsch synthesis), typically comprise a Group VIII metal, supported on a carrier of catalyst. The Group VIII metal is preferably selected from iron, nickel, cobalt and / or ruthenium, preferably iron or cobalt, especially cobalt. The catalyst carrier is preferably an inorganic refractory oxide, preferably alumina, silica, titania, zirconia or mixtures thereof. The Group VIII metal which is typically Rf.27339 present in the hydrocarbon synthesis catalyst, in particular catalysts comprising iron, cobalt, nickel and / or ruthenium, must be at least partially in the metallic state in order to be active in the catalysis of the synthesis of hydrocarbons from carbon monoxide and hydrogen. Thus, before use, the catalyst is subjected to one or more reduction or activation steps, in the presence of hydrogen. Various ways to activate hydrocarbon synthesis catalysts are known in the art. Thus, European Patent Application Publication No. 0 533 227 describes a process for the activation of a Fischer-Tropsch catalyst by contacting with a hydrogen-containing gas, wherein the concentration of hydrogen and the spatial velocity of the gas are increased stepwise or continuously during activation. European Patent Application Publication No. 0 533 228 describes a process for the activation of a Fischer-Tropsch catalyst, which comprises contacting the catalyst with a hydrogen-containing gas in a first stage at a total pressure of up to 5%. bars, rapidly increasing the pressure to at least 10 bars and contacting the catalyst with a gas containing hydrogen in a second stage at this pressure. U.S. Patent Specification No. 4,670,414 describes an activation process comprising, in sequence, the steps of (a) reduction with a hydrogen-containing gas, (b) oxidation with an oxygen-containing gas, and (c) reduction with a gas containing hydrogen. The process for activating hydrocarbon synthesis catalysts can be performed ex situ, but can also be performed in situ in the reactor just before the start, particularly for fixed bed units. The hydrocarbon synthesis processes can be carried out in various types of catalyst bed, such as fluidized beds, fixed beds, moving beds, boiling beds and slurry beds. In the boiling and slurry beds in operation, the catalyst is kept dispersed in a liquid, typically a hydrocarbon liquid. Bubbles of reactive gases (hydrogen and carbon monoxide) flow upward (usually) or downward through the liquid containing catalyst. It will be appreciated that it would be desirable to be able to activate the catalyst in the presence of the hydrocarbon liquid. This would be particularly convenient for boiling and gaseous slurry catalyst beds. A major problem, however, is the occurrence of hydrogenolysis of the hydrocarbon liquid, which is catalyzed by the activated (partially) hydrocarbon synthesis catalyst. The hydrogenolysis of the hydrocarbon liquid can cause the formation of undesirable methane and an increase in the adiabatic temperature. Additionally, coke can be formed, affecting the duration and activity of the catalyst. The problem of hydrogenolysis is especially applicable to hydrocarbon synthesis catalysts comprising more than one metal. For example, in U.S. Pat. 4,588,708 it is stated that the Co / Mn catalysts are approximately 15 times more active in the hydrogenolysis reaction than the catalyst comprising cobalt alone. European Patent Application Publication No. 0 589 692 describes a process for activating a hydrocarbon synthesis catalyst, in which the catalyst is first reduced (activated) ex situ without the presence of hydrocarbon liquids, and the reduced catalyst is then further activated in the presence of hydrogen and a hydrocarbon liquid. It is described in column 3, lines 40-48 of that publication that hydrogenolysis and coke formation are avoided in view of the relatively short treatment time. European Patent Application Publication No. 0 590 882 describes a similar process in which a partially deactivated but still reduced catalyst is subjected to a renewal treatment in the presence of a hydrocarbon liquid. Activation, as used herein, is a process in which a fresh catalyst is treated with hydrogen to reduce the (oxidized) metal compounds to catalytically active metals, thereby activating the catalyst. Usually, the catalyst is calcined by reaction with a gas containing oxygen at elevated temperatures before reduction. Renovation, as used herein, is a process in which an exhausted catalyst is treated with hydrogen to restore at least some of the initial activity of an activated fresh catalyst. Without wishing to be bound by a particular theory, it would seem that, among others, the following processes occur during the renovation: removal of coke precursors, removal of metal-bearing compounds and reduction of metal compounds. It would be desirable to have the ability to activate or completely renew a catalyst, in particular a hydrocarbon synthesis catalyst, in the presence of a hydrocarbon liquid, while avoiding hydrogenolysis and / or coke formation, and eliminating the need for a step of previous reduction. It has now been surprisingly found that it is possible to activate or renew catalysts in the presence of a hydrocarbon liquid by contacting the catalysts with hydrogen or a hydrogen-containing gas in which the partial pressure of hydrogen exceeds a certain limit.

DETAILED DESCRIPTION OF THE INVENTION Therefore, the present invention relates to a process for activating or renewing a catalyst, preferably a hydrocarbon synthesis catalyst, in the presence of a hydrocarbon liquid, the catalyst comprising a metal compound of Group Ib, VIIb or VIII, by contacting the catalyst with a gas containing hydrogen at a partial pressure of hydrogen of at least 15 bar abs. For the purposes of this specification, a gas containing hydrogen is a gas containing hydrogen and, optionally, one or more components of inert gas such as nitrogen. A synthesis gas mixture, comprising hydrogen and (substantial amounts of) carbon monoxide, is not included in the term hydrogen-containing gas as used herein. Preferably, the partial pressure of hydrogen is at least 20 bar abs; preferably at least 30 bar abs.

Typically, the partial pressure of hydrogen is, at most, 200 bar abs; preferably, at most, 100 bars abs. More preferably, the partial pressure of hydrogen is maintained in the range from 50 to 60 bar abs. A preferred catalyst to be activated or renewed according to the process of the present invention comprises a Group VIII metal compound. The term "metal compound" includes, apart from oxides, hydroxides, carbides, etc. of metal, also metal itself, especially in the case of renovation. Preferably, a cobalt, nickel or ruthenium compound or mixtures thereof. More preferably, the catalyst comprises a cobalt metal compound, in particular a cobalt oxide. The preferred catalyst to be activated or renewed is typically a hydrocarbon synthesis catalyst.

The metal compound is typically supported on a catalyst carrier. A suitable catalyst carrier can be selected from the group of refractory oxides, preferably alumina, silica, titania, zirconia or mixtures thereof, preferably silica, titania, zirconia or mixtures thereof. The catalytically active metal can be applied to the carrier by any of the techniques known in the art, for example regrinding, impregnation, spray coating or precipitation, especially co-curing, impregnation or spray coating. Impregnation is a particularly preferred technique, in which the carrier is contacted with a compound of the catalytically active metal in the presence of a liquid, more conveniently in the form of a solution of the metal compound. The active metal compound can be inorganic or organic, with inorganic compounds, in particular nitrates, being preferred. The liquid used can also be organic 0 inorganic Water is the most convenient liquid. It will be appreciated that water can be derived, at least partially, from crystal water which is released from the metal compound in the impregnation at elevated temperature. The amount of catalytically active metal present in the carrier is typically in the range of from 1 to 100 parts by weight, preferably 10 to 50 parts by weight, per 100 parts by weight of carrier material. The catalytically active metal may be present in the catalyst together with one or more metal promoters or cocatalysts. The promoters may be present as metals or as the metal oxide, depending on the particular promoter. Suitable promoters include oxides of metals of Groups IIA, IIIB, IVB, VB, VIB, and / or VIIB of the Periodic Table, oxides of the lanthanides and / or the actinides. Preferably, the catalyst comprises at least one oxide of an element of Group IVB, VB and / or VIIB of the Periodic Table, in particular titanium, zirconium, manganese and / or vanadium. As an alternative or in addition to the metal oxide promoter, the catalyst may comprise a metal promoter selected from Groups VIIB and / or VIII of the Periodic Table. Preferred metal promoters include rhenium, platinum and palladium. A more suitable catalyst comprises cobalt as the catalytically active metal and zirconium as a promoter. Another more suitable catalyst comprises cobalt as the catalytically active metal and manganese and / or vanadium as a promoter. The promoter can be incorporated into the catalyst using any of the methods discussed hereinabove with respect to the catalytically active component. The promoter, if present in the catalyst, is typically present in an amount of from 0.1 to 60 parts by weight, preferably from 0.5 to 40 parts by weight, per 100 parts by weight of carrier material. It will be appreciated, however, that the optimal amount of promoter can vary for the respective elements that act as the promoter. If the catalyst comprises cobalt as the catalytically active metal and manganese and / or vanadium as the promoter, the atomic ratio of cobalt: (manganese + vanadium) is advantageously at least 12: 1. The hydrocarbon liquid to be used in the process of the present invention is more conveniently a product of a hydrocarbon synthesis process, in particular a process as described herein. Alternatively, fractions of crude oil (refined) or liquid polyolefins may be used. Preferably, the hydrocarbon liquid is highly paraffinic. Typically, a highly paraffinic hydrocarbon liquid contains at least 70% by weight, preferably 80% by weight, and preferably 90% by weight of paraffinic hydrocarbons. The process is typically carried out at a temperature in the range from 180 to 400 ° C, preferably from 200 to 350 ° C, preferably from 220 to 320 ° C. A more preferred temperature range, especially for cobalt-containing catalysts, is from 240 to 320 ° C. For some catalysts, however, which contain catalytically active metal compounds which are difficult to reduce, it may be convenient to operate the process mainly towards the upper end of the range from 180 to 400 ° C. In such a case, it is particularly convenient to operate the process at a high hydrogen partial pressure, typically at least 30 bar abs; preferably at least 50 bar abs. At temperatures below 220 ° C, especially below 200 ° C, very especially below 180 ° C, the partial hydrogen pressure may be less than the partial pressure of hydrogen at which the effective reduction is carried out. At these temperatures the hydrogenolysis rates are relatively low, and thus a lower partial hydrogen pressure can be used. Usually the partial hydrogen pressures will be more than 75% of the final pressure, especially 50% or more, very especially 25% or more for the temperatures indicated above. At temperatures below 180 ° C, especially below 160 ° C, partial pressures of hydrogen may be even lower, for example 50% or more, especially 25% or more of the final partial hydrogen pressure. Thus, a programmed profile of hydrogen pressure increase / temperature increase can be used to achieve the final reaction conditions. During these initial reaction steps, part of the reduction reaction may already occur, for example up to 40% of the final reduction reaction, preferably up to 20%, preferably up to 10%. The activation process according to the present invention is conveniently carried out at a constant temperature level or in a programmed manner as described above. In a preferred embodiment, the activation process is carried out as follows. A fresh catalyst, mixed with hydrocarbon liquid, is first heated to an initial temperature, typically in the range of 150 to 180 or even 200 ° C, preferably in the presence of an inert gas such as nitrogen. Once this initial temperature is reached, the catalyst is contacted with a gas containing hydrogen, at the appropriate partial pressure. The temperature is increased by increments (step by step) or continuously at a rate in the range from 0.1 to 10 ° C / min up to a final temperature, typically at least 240 ° C, preferably at least 250 ° C, but within of the temperature ranges as indicated above. It will be understood that if the temperature is increased by increments, the rate of temperature increase above refers to the rate during periods of temperature increase and not to the rate of average temperature increase between initial and final temperature. The mixture of catalyst and hydrocarbon liquid is maintained at the final temperature level for a period sufficient to substantially activate the catalyst, typically by at least 0.25 hours, preferably at least 2 hours. If desired, the temperature of the mixture is then decreased incrementally or continuously at a rate in the range from 0.1 to 10 ° C / min up to a final temperature which, for safety reasons, is at least 10 ° C lower than the temperature contemplated for the hydrocarbon synthesis step. According to one embodiment, the hydrogen-containing gas can then be replaced by a synthesis gas mixture comprising hydrogen and carbon monoxide, to begin the step of hydrocarbon synthesis. According to another embodiment, the hydrogen-containing gas is first replaced by an inert gas, such as nitrogen, and then the inert gas is replaced by a synthesis gas mixture to begin the hydrocarbon synthesis step. It has been found that, in the latter case, it is beneficial that the temperature of the catalyst mixture and hydrocarbon liquid is lower than the temperature at which substantial hydrogenolysis begins to occur, when brought into contact with the inert gas. Preferably the temperature is less than 200 ° C, preferably less than 185 ° C. According to a particularly preferred embodiment, the rate of temperature increase depends on the reduction rate (activation), which can be verified by the amount of water production. Preferably, the activation is carried out in a controlled manner. Thus, the water production rate (steam) is maintained below a certain level. This level can depend on the catalyst that is being activated and can be determined by routine experimentation. For example, catalysts comprising a carrier containing silica tend to be sensitive to too high amounts of water vapor present during activation. Thus, if a catalyst comprising a carrier containing silica is to be activated, the amount of water vapor present in the hydrogen-containing exit gas is preferably less than 4000 ppmv, preferably less than 3000 ppmv. For catalysts containing titania or zirconia, the amount of water vapor in the hydrogen-containing exit gas can be conveniently higher, for example in the range from 0.4 to 10% by volume. For these latter catalysts it may even be convenient to add additional water vapor during the activation step. Conveniently, the renewal process is carried out using the same temperature program that was typically applied during the activation step. However, it will be appreciated that in the renewal process the spent catalyst is already normally at an elevated temperature, typically between the hydrocarbon synthesis temperature and a temperature up to 100 ° C lower. Thus, a temperature increase program may not be necessary. The renewal step can be carried out in batches or continuously. In a batch mode of operation, normally the complete catalyst inventory of a hydrocarbon synthesis reactor vessel is subjected to a renewal treatment. Preferably, the renewal treatment is carried out in situ. The hydrocarbon synthesis process is temporarily stopped by interrupting the supply of synthesis gas, and introducing hydrogen-containing gas into the reactor. In a continuous mode of operation, a small portion of catalyst is removed from the hydrocarbon synthesis reactor and renewed in a separate renewal vessel. It will be appreciated that it is also possible to remove portions of catalyst in a batch operation method. The renewal step is preferably carried out in a temperature range that is from 50 ° C lower than the operating temperature of hydrocarbon synthesis to 50 ° C higher than the hydrocarbon synthesis temperature, but still within the temperature range broad as indicated above.

The temperature can be increased or decreased in increments or continuously up to the desired renewal temperature at a rate in the range of 0.5 to 20 ° C / min. The temperature is maintained at the desired renewal temperature level for a period sufficient to substantially renew the catalyst, typically for at least 10 minutes, preferably at least 30 minutes, preferably at least 1 hour. If desired, the temperature is then decreased or increased in increments or continuously to the desired final temperature at a rate in the range of 0.5 to 20 ° C / min, which for safety reasons is at least 10 ° C lower than the temperature contemplated for the hydrocarbon synthesis step. It will be appreciated that the supply of synthesis gas to the catalyst to be renewed can be simply replaced by a gas containing hydrogen, and the hydrogen-containing gas can be simply replaced by a synthesis gas supply, after the renewal step . It may be convenient, however, to replace the supply of synthesis gas and / or gas containing hydrogen, as the case may be, first with a supply of an inert gas such as nitrogen, followed by the replacement of the inert gas with gas which contains hydrogen or synthesis gas. In that case, it is beneficial that the temperature of the catalyst mixture and hydrocarbon liquid is lower than the temperature at which substantial hydrogenolysis begins to occur in the presence of the inert gas. Preferably the temperature is lower than 200 ° C, preferably lower 185 ° C. The volume percentage of hydrogen present in the hydrogen-containing gas can vary widely. Typically, a hydrogen-containing gas comprising from 25 to 100% by volume of hydrogen is employed. For economic reasons, the hydrogen-containing gas preferably comprises from 50 to 100 volume% of hydrogen, preferably 80 to 100 volume% of hydrogen. The gas containing hydrogen can be derived from known sources. Suitable examples include an installation dedicated to the manufacture of hydrogen and a tail gas from a hydrocarbon synthesis process. The tail gas to be used in the activation and renewal process typically comprises hydrogen, carbon dioxide, carbon monoxide, gaseous hydrocarbon products and water. Optionally, the tail gas is treated to remove gaseous hydrocarbon products, carbon dioxide and / or water. The amount of carbon monoxide must be less than 5% by volume, preferably less than 2% by volume. If the tail gas contains more carbon monoxide, the tail gas is first led to a medium capable of separating a hydrogen-rich gas, depleted in carbon monoxide, from the tail gas. An example of such a medium is a Pressure Oscillating Adsorber. The process is typically carried out for a sufficient period to activate or renew the catalyst. It will be appreciated that this period may vary, depending on the composition of the catalyst, the average reaction temperature and the partial pressure of hydrogen. Typically, the catalyst is contacted with the hydrogen-containing gas for 0.5 to 48 hours, preferably for 6 to 36 hours. According to a preferred embodiment, the catalyst is contacted with the gas containing hydrogen until at least 25% by weight, preferably at least 50% by weight, preferably at least 80% by weight, of the compound of metal is reduced to the metallic state. The amount of the metal compound that has been reduced can be conveniently verified by measuring the cumulative water production during the process. Other methods known to those skilled in the art include Thermogravimetric Analysis and Programmed Temperature Reduction.

The process of activation and renewal in the presence of hydrocarbon liquids is especially advantageous for use in hydrocarbon synthesis processes that operate with boiling catalyst or slurry catalyst beds. The boiling catalyst and slurry catalyst beds are well known to those skilled in the art. In the boiling and slurry beds in operation, the catalyst is kept dispersed in a liquid, typically a hydrocarbon liquid. The bubbles of the reactive gases (hydrogen and carbon monoxide) flow (usually) upwards through the liquid containing the catalyst. According to a preferred embodiment, in the process for activation / renewal of catalyst in a bed of slurry or boiling, the catalyst is kept dispersed in the hydrocarbon liquid. The process is exothermic. By keeping the catalyst dispersed in the liquid, heat transfer is facilitated. The catalyst can be kept dispersed in the hydrocarbon liquid by maintaining a high upward surface velocity of the hydrocarbon liquid, and / or by injection of hydrogen-containing gas at a sufficiently high surface gas velocity. The operation with a low liquid velocity along the bubble column of the slurry can be preferred, ie a low surface velocity of the hydrocarbon liquid, since this can reduce or eliminate the need for recycling of the liquid. liquid watery paste. This can reduce the complexity of reactor operating procedures and can reduce operating and capital expenses. However, operation with a high liquid velocity along the bubble column of the slurry can also be preferred. This may be the case if it is desired to separate the liquid product and the catalyst outside the reactor or, for example, if it is desired to continuously renew the catalyst in a separate vessel. It has been found to be especially advantageous for catalysts comprising silica to activate the catalyst in situ in the reactor vessel. Typically, the surface velocity of the liquid is maintained in the range from 0.05 to 4.0 cm / sec. It will be appreciated that the preferred range may depend on the preferred mode of operation, as discussed above.

If it is desired to operate at a low surface velocity of the liquid, the velocity is preferably maintained in the range from 0.05 to 1.0 cm / sec; preferably from 0.2 to 0.8 cm / sec. If it is desired to operate at a high surface velocity of the liquid, the velocity is preferably maintained in the range from 0.5 to 4.0 cm / sec; depending among others on the size and density of the catalyst particles, preferably from 1.0 to 3.0 cm / sec. Typically, the surface velocity of the hydrogen-containing gas varies from 0.5 to 50 cm / sec; preferably from 0.5 to 40 cm / sec; preferably from 1 to 30 cm / sec, more preferably from 1 to 15 cm / sec. According to a further aspect, the present invention relates to a hydrocarbon synthesis process comprising activating or renewing a hydrocarbon synthesis catalyst in the presence of a hydrocarbon liquid, contacting the catalyst with a hydrogen-containing gas at a hydrogen partial pressure of at least 15 bar abs; and then contacting the catalyst with a mixture of hydrogen and carbon monoxide at the reaction conditions of hydrocarbon synthesis. The hydrocarbon synthesis process is typically carried out at a temperature in the range from 125 to 350 ° C, preferably 200 to 275 ° C. The pressure typically varies from 5 to 80 bar abs; preferably from 20 to 60 bar abs. Hydrogen and carbon monoxide (synthesis gas) are typically fed to the process in a molar ratio in the range from 0.4 to 2.5. In a preferred embodiment of the hydrocarbon synthesis process, the molar ratio of hydrogen to carbon monoxide is of the order of 1.0 to 2.5, especially 1.5 to 2.5. The space velocity per hour of gas may vary within wide ranges and is typically in the range from 400 to 14000 h "1, for example 400 to 4000 h" 1. The process for the preparation of hydrocarbons can be conducted using a variety of reactor types and reaction regimes, for example a fixed bed regime, a slurry phase regime or a boiling bed regime. It will be appreciated that the size of the catalyst particles may vary depending on the reaction regime for which they are intended. Those skilled in the art will have the experience to select the most appropriate catalyst particle size for a given reaction regime. Additionally, it will be understood that skilled persons have the ability to select the most appropriate conditions for a specific reactor configuration and reaction regime. For example, the space velocity per hour of preferred gas may depend on the type of reaction regime being applied. Thus, if it is desired to operate the hydrocarbon synthesis process with a fixed bed regime, preferably the space velocity per hour of gas is selected in the range from 500 to 2500 Nl / l / h. If it is desired to operate the hydrocarbon synthesis process with a slurry phase regime, preferably the space velocity per hour of gas is selected in the range from 1500 to 8000 h "1, especially from 3000 to 3500 h" 1. Preferably, the hydrocarbon synthesis step is carried out in a bed of boiling catalyst or slurry in the presence of a hydrocarbon liquid. At least during the hydrocarbon synthesis step, the catalyst is kept dispersed in the hydrocarbon liquid. Preferably, the catalyst is kept dispersed during the activation or renewal step and during the hydrocarbon synthesis step. Preferably, the surface velocity of the synthesis gas is in the range from 0.5 to 50 cm / sec; preferably in the range from 5 to 35 cm / sec.

Typically, the surface velocity of the liquid is maintained in the range from 0.05 to 4.0 cm / sec. It will be appreciated that the preferred range may depend on the preferred mode of operation, as described above with respect to the activation / renewal step. If it is desired to operate at a low surface velocity of the liquid, the velocity is preferably maintained in the range from 0.05 to 1.0 cm / sec.; preferably from 0.2 to 0.8 cm / sec. If it is desired to operate at a high surface velocity of the liquid, the velocity is preferably maintained in the range from 0.5 to 4.0 cm / sec; depending among others on the size and density of the catalyst particles, preferably from 1.0 to 3.0 cm / sec. According to an embodiment of the invention, the activation and / or renewal and synthesis steps of hydrocarbons are carried out in the same reactor vessel, preferably in the same catalyst bed. According to another embodiment of the invention, the activation and / or renewal and synthesis steps of hydrocarbons are carried out in separate containers, that is, a reactor vessel for the hydrocarbon synthesis step, an activation / renewal vessel. combined, or separate activation and renewal containers. Thus, the catalyst to be renewed is conducted, together with hydrocarbon liquid, into the activation / renewal vessel or renewal vessel, from the hydrocarbon synthesis vessel, the renewed catalyst, together with a hydrocarbon liquid, is conducted back to the hydrocarbon synthesis vessel. The fresh catalyst to be activated is introduced into the activation / renewal vessel or the activation vessel, and the activated catalyst is conducted with a hydrocarbon liquid to the hydrocarbon synthesis vessel. Preferably, the hydrocarbon liquid comprises a product of the hydrocarbon synthesis step. According to an embodiment of the invention, the activation / renewal step or renewal step is combined with a hydrogenation step in which the hydrocarbon liquid is hydrogenated and a hydrogenated product is obtained. Embodiments of the invention will now be described in greater detail with reference to Figures 1 to 3. Those skilled in the art will appreciate, however, that several alternative embodiments are possible, without departing from the scope of the invention.

Figure 1 schematically represents an embodiment in which the catalyst is activated and / or renewed in situ in a reactor vessel comprising a bed of slurry or boiling catalyst. Figure 2 schematically represents an embodiment in which a slurry of concentrated catalyst is activated and renewed. Figure 3 schematically depicts an embodiment in which at least a portion of a slurry of catalyst together with hydrocarbon-containing product is conducted to a hydrogenation reactor to simultaneously hydrogenate the hydrocarbon-containing product and to renew the catalyst. With reference to Figure 1, a reactor vessel 1, comprising a bed of slurry or boiling paste catalyst and a cooling medium (not shown) is equipped with a gas inlet means 2 and an outlet means of 3. The catalyst present in the reactor vessel can now be activated or renewed by introducing a hydrogen-containing gas under appropriate conditions into the reactor vessel 1 via the gas inlet medium 2. A gaseous effluent, comprising unconverted hydrogen, inert gases and water vapor, leaves the reactor vessel by the gas outlet means 3.

After activation or renewal of the catalyst, synthesis gas is introduced into the reactor vessel 1 via the gas inlet 2. Due to the high exothermic condition of the hydrocarbon synthesis reaction, the slurry catalyst bed or at boiling is preferably at a temperature lower than the contemplated reaction temperature, preferably at least 10 ° C below the contemplated reaction temperature before synthesis gas is introduced into the reactor vessel 1. A slurry of catalyst comprising a hydrocarbon product is conducted through line 4 and pump 9, to a separation medium 5. The catalyst-free hydrocarbon product is discharged via line 6 and a concentrated catalytic water paste is conducted from the separation means 5, through lines 7 and 8 back to the reactor vessel 1. The spent catalyst can be discharged through line 10 and, if desired, can be regenerated or renewed in means not shown or renewed in the activation vessel 16, as will be discussed below, and subsequently conducted back to the reactor vessel 1.

If desired, part or all of the separation means 5 can be integrated into the reactor vessel 1. Additionally, the line 10 can be omitted if the reactor vessel additionally comprises a catalyst outlet means. This is particularly convenient if the separation means 5 is integrated into the reactor vessel 1. In a preferred embodiment, an activated, fresh catalyst is introduced into the reactor vessel 1 from a separate activation vessel 16. The activation vessel 16 comprises a gas inlet means 11, a catalyst inlet means 14 and a gas outlet means 15. The activated catalyst is conducted by line 12 or by lines 13 and 8 to the reactor vessel 1. The activation in the vessel 16 is typically carried out in the presence of a hydrocarbon liquid, which can be derived from line 6 and introduced into vessel 16 together with the catalyst by means of catalyst inlet 14. It will be appreciated that, in one embodiment Alternatively, the reactor vessel 1 is not used for the activation or renewal of the catalyst, but is continuously used for hydrocarbon synthesis. As in the embodiment described above, the fresh catalyst is activated in the activation vessel 16 and introduced into the reactor vessel 1 by lines 12 or 13 and 8, and the spent catalyst is discharged through the line 10. It will be appreciated that, at the start, the fresh catalyst is activated batchwise in the activation vessel 16. The batches of activated catalyst can then be introduced into the reactor vessel where the catalyst is maintained under conditions that prevent coke formation and / or hydrogenolysis, that is, at a low temperature, preferably less than 185 ° C, and / or in the presence of a gas containing hydrogen at a hydrogen partial pressure of at least 15 bar abs; preferably at least 20 or at least 30 bar abs. With reference to Figures 2 and 3, reference numbers corresponding to the numbers in Figure 1 have the same meaning as in Figure 1. Those skilled in the art will appreciate without difficulty that the preferred or alternative embodiments discussed with respect to Figure 1 can be applied, when appropriate, to the process configuration represented schematically in any of Figures 2 or 3 or in additional alternative process configurations. Figure 2 schematically depicts an embodiment in which at least part of a slurry of concentrated catalyst in line 7 is conducted to a renovation vessel 20. A gas containing hydrogen is introduced into vessel 20 via line 21. Optionally , a fresh catalyst, which may have been partially or fully activated in media not shown, is introduced into vessel 20 by line 22. A fresh gaseous catalyst paste is conducted through line 23 and pump 25 to the reactor vessel. 1. A gaseous effluent, comprising unconverted hydrogen, inert gases and water vapor, leaves the vessel 20 by the gas outlet means 24. Alternatively, the pump 25 is omitted and the slurry of concentrated catalyst of higher density is removed. that the slurry of catalyst in the reactor vessel 1 is conducted back to the reactor vessel by gravity. Figure 3 schematically depicts an embodiment in which at least part of a slurry of catalyst and hydrocarbon-containing product is conducted through line 4, pump 30 and line 31 to a hydrogenation reactor 33 to hydrogenate simultaneously the product containing hydrocarbons and to renew the catalyst. The gas containing hydrogen is introduced to reactor 33 by line 32. The gaseous effluent leaves reactor 33 by line 34. Optionally, reactor 33 is also used to simultaneously activate the fresh catalyst, which is introduced to reactor 33 as a supplement for any spent catalyst removed. The fresh catalyst is maintained in the container 36, which is equipped with a gaseous slurry input medium of catalyst 38, and optionally with a gas inlet means 37 and an outlet means 39 to allow at least partial pre-reduction of the catalyst before the introduction to the container 33. The fresh catalyst, optionally partially or fully activated, is conducted from the container 36 through the line 35 and the pump 46 to the container 33. It will be appreciated that, according to an alternative embodiment , the fully activated catalyst from the vessel 36 is led directly to the gaseous sparge column by means not shown. The effluent of slurry from the reactor 33 comprising the renewed catalyst and the product containing hydrogenated hydrocarbons is conducted via line 40 and pump 47 to a separation means 41. The product containing hydrogenated hydrocarbons leaves the separation medium 41 by line 42. A slurry of renewed catalyst concentrate is conducted to reactor vessel 1 via line 43. The spent catalyst can be conveniently removed from recycling by lines 44 or 45.

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

EXAMPLE I The following experiments demonstrate the effect of partial pressure of hydrogen on the hydrogenolysis activity of a fully activated catalyst comprising 22% by weight of cobalt on a zirconia-silica carrier. In the experiments, a microflow unit was charged with 9.5 ml of catalyst. The catalyst was activated in the absence of hydrocarbons at a temperature of 290 ° C and a hydrogen partial pressure of 3 bar. Next, n-hexadecane was passed through the catalyst bed at elevated temperature and in the presence of hydrogen. The hydrogenolysis activity was determined by measuring the amount of methane in the exit gas. The results are summarized in Table I. As can be seen in Table I, the hydrogenolysis activity at high hydrogen partial pressures is much lower than the activity at lower hydrogen pressures.

Table I 1 2 3 4 5 6 T (° C) 255 273 260 270 250 274 n-Cie 3.1 3.1 3.2 3.4 3.4 3.4 GHSV 1.7 1.7 1.2 1.2 1.2 1.2 P (H2) 29.0 29.5 11.3 7.0 38.7 38.9 CH4 0.6 2.0 4.6 12.6 0.3 1.5 Legend: n-Ciß = flow of n-hexadecane in g / 1 GHSV = Space Velocity Per Hour of Gas in Nm3 / l / h P (H2) = Hydrogen partial pressure of bars g CH4 = Production of CH4 in mmoles / h EXAMPLE II A fresh cobalt catalyst on zirconia-silica, having a particle size of about 40 μm, was activated in situ in a 10 cm diameter watery bubbler column in the presence of a hydrocarbon liquid. The slurry of hydrocarbon liquid and catalyst contained 30% by volume of catalyst. The catalyst was suspended in a commercially available hydrocarbon starting oil, sold by Shell Companies under the trade designation ONDINA-68, and dried under nitrogen at 3 bar abs, and a surface gas velocity Ug of 6 cm / sec. The temperature was continuously increased from 20 ° C to 180 ° C at a rate of 5 ° C / h. At 180 ° C, the gaseous sparge column was pressurized to 60 bar abs. and the nitrogen was replaced by hydrogen (100% by volume) in a one-step operation. The temperature was increased by 5 ° C / h to 260 ° C. The aqueous catalyst paste was maintained at this temperature for 2 hours. If necessary, the temperature was temporarily kept constant or decreased to maintain the concentration of water vapor in the exit gas below 4000 ppmv. Hydrogenolysis was verified by in-line analysis of CH4 in the exit gas. At a temperature of 260 ° C, a maximum CH4 content of 0.5% by volume in the outlet gas was observed. After activation, the temperature was reduced to 180 ° C, and the pressure was reduced to 40 bar abs. Synthesis gas was introduced at a surface gas velocity Ug of 10 cm / sec. The H2 / CO ratio at the entrance of the gaseous pulp bubble column was 1.1 (v / v). The temperature was increased to 210 ° C and the bubble column of the slurry was left out of line for 48 hours. A first order reaction rate constant of 0.11 mol of converted CO / kg of catalyst / barium H2 was obtained for the Fischer-Tropsch synthesis. For comparative purposes, the same catalyst was activated in the absence of liquid hydrocarbons in a fixed-bed microflow unit and tested in a gas-phase single step operation to determine its intrinsic activity, i.e., excluding any transfer limitations of intra-particle mass. The activation was carried out at 2 bars abs. of total pressure, using a mixture of hydrogen / nitrogen gases at a GHSV of 2600 Nl / l / h and 260 ° C. The water concentration was maintained below 4000 ppmv by varying the hydrogen partial pressure of the gas mixture. After 3 hours, the gas mixture was replaced by 100% hydrogen gas. The catalyst was kept in this condition for 16 hours. Then, the temperature was lowered to 180 ° C, and synthesis gas was introduced at 800 Nl / lh. The H2 / CO ratio at the entrance of the microflow unit was 1.1 (v / v). The temperature was increased to 210 ° C and the system was left offline for 48 hours. A first-order reaction rate constant of 0.10 mol of converted CO / kg of catalyst / barium H2 was obtained for the Fischer-Tropsch synthesis. Accordingly, the activated catalyst in the presence of the hydrocarbon liquid has approximately the same activity as the activated catalyst in the absence of the hydrocarbon liquid. The activity of hydrogenolysis during activation in the presence of the hydrocarbon liquid was negligible.

It is noted that in relation to this date the best method known by the applicant to carry out the ementioned 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 process for activating or renewing a catalyst in the presence of a hydrocarbon liquid, the catalyst comprises a Group Ib, Vllb or VIII metal compound, characterized in that the catalyst is contacted with a hydrogen-containing gas at a hydrogen partial pressure of at least 15 bar abs.

2. A process according to claim 1, characterized in that the partial pressure of hydrogen is at least 20 bar abs.

3. A process according to claim 2, characterized in that the partial pressure of hydrogen is at least 30 bar abs. and at the most 200 bars abs.

4. A process according to any one of the preceding claims, characterized in that the catalyst is a hydrocarbon synthesis catalyst.

5. A process according to claim 4, characterized in that the catalyst comprises a cobalt compound and a carrier selected from alumina, silica, titania, zirconia or mixtures thereof.

6. A process according to any of the preceding claims, characterized in that the temperature is maintained in the range from 180 to 400 ° C.

7. A process according to any one of the preceding claims, characterized in that the surface velocity of the gas containing hydrogen is from 0.5 to 30 cm / sec. and a hydrogen-containing gas comprising from 25 to 100% by volume of hydrogen is employed.

8. A process according to any one of the preceding claims, characterized in that the catalyst is brought into contact with the hydrogen or gas containing hydrogen for 0.5 to 48 hours.

9. A hydrocarbon synthesis process, characterized in that it comprises activating or renewing a hydrocarbon synthesis catalyst in the presence of a hydrocarbon liquid, by contacting the catalyst with a gas containing hydrogen at a hydrogen partial pressure of at least 15%. abs bars; and then contacting the catalyst with a mixture of hydrogen and carbon monoxide under the reaction conditions of the hydrocarbon synthesis.

10. A process according to claim 9, characterized in that the hydrocarbon liquid, which comprises the product of the hydrocarbon synthesis step, is conducted from the hydrocarbon synthesis step to the renewal step, in such a step the hydrocarbon liquid is hydrogenated. and a hydrogenated product is obtained.