WO2014140973A1

WO2014140973A1 - A hydrocarbon synthesis process using a cobalt-based catalyst supported on a silicon carbide comprising support

Info

Publication number: WO2014140973A1
Application number: PCT/IB2014/059259
Authority: WO
Inventors: Peter Jacobus Van Berge
Original assignee: Sasol Technology Pty Ltd
Current assignee: Sasol Technology Pty Ltd
Priority date: 2013-03-14
Filing date: 2014-02-26
Publication date: 2014-09-18
Anticipated expiration: 2015-09-14

Abstract

The present invention relates to a process for producing hydrocarbons, and more particularly to such a process which includes the use of a cobalt-based silicon carbide supported catalyst. According to the invention, there is provided a process for producing hydrocarbons and, optionally, oxygenates of hydrocarbons, the process including: contacting syngas, which includes a mixture of hydrogen and carbon monoxide, with a cobalt-based supported catalyst in a slurry bed of a slurry bed reactor at a temperature above 180°C in the slurry bed, a pressure of at least 10 bar(a) (1000 kPa(a)) in the slurry bed and a water partial pressure (PH2o) reaching at least 5 bar(a) (500 kPa(a)) in the slurry bed; wherein: the cobalt-based supported catalyst has been prepared by (i) introducing a cobalt compound onto and/or into a particulate silicon carbide catalyst support to provide a cobalt loaded silicon carbide catalyst support; (ii) calcining the cobalt loaded silicon carbide catalyst support under non-reducing conditions at a temperature above 400°C to provide a catalyst precursor; and (iii) reducing the catalyst precursor to activate the catalyst precursor and thus providing a cobalt-based supported catalyst.

Description

A HYDROCARBON SYNTHESIS PROCESS USING A COBALT-BASED CATALYST SUPPORTED ON A SILICON CARBIDE COMPRISING SUPPORT

TECHNICAL FIELD

This invention relates to a process for producing hydrocarbons, and more particularly to such a process which includes the use of a cobalt-based silicon carbide supported catalyst.

BACKGROUND ART

Hydrocarbon synthesis from synthesis gas (or syngas) including a mixture of hydrogen and carbon monoxide in the presence of a Fischer-Tropsch (FT) catalyst is commonly known as Fischer-Tropsch synthesis (FTS). FTS forms part of gas-to-liquids, coal-to-liquids, and biomass-to-liquids processes in which natural gas, coal, and biomass respectively are usually converted by means of a three step process into liquid hydrocarbons. The three process steps are normally (i) production of synthesis gas (or syngas) comprising a mixture of hydrogen and carbon monoxide from natural gas, coal, or biomass, (ii) conversion of the syngas into a waxy syncrude by means of FTS, and (iii) a hydrocracking or hydrotreating step to convert the waxy syncrude into liquid transportation fuels such as diesel, petrol, jet fuel, as well as naphtha.

During the conversion of syngas in a FTS process, the mixture of H₂ and CO is contacted with a FTS catalyst at elevated pressure and temperature thereby converting the syngas to hydrocarbons and, optionally, oxygenates of hydrocarbons. It would be understood that during FTS it is aimed to convert as much syngas as is possible into hydrocarbons, particularly long chain hydrocarbons. However, during FTS water (H₂0) forms as a byproduct and often FT catalysts are sensitive to H₂0 in a FTS reactor, causing the FT catalysts to deactivate over time when exposed to a high water partial pressure (Ρ_Η2ο)·

FTS catalysts in the form of cobalt supported on alumina deactivate much faster at higher water partial pressures of around 1000 kPa than at a water partial pressure of around 450 kPa, as illustrated in Table 1. Due to this high deactivation rate at a high P_H2o_> the FTS either has to be carried out at a low P_H2o resulting in a lower syngas conversion, or the average catalyst activity will be lower, requiring mitigating actions such as replacing the catalyst more frequently, loading more catalyst into the reactor, etc., that is, a less economical process is obtained. Accordingly, it is desirable to have a FTS catalyst that is resistant to deactivation under high P_H2o during FTS. High P_H2o is more problematic in slurry bed reactors compared to fixed bed reactors, since there is a substantial extent of back-mixing in slurry bed reactors so that a comparatively large part of the slurry bed is exposed to high P_H2o- In addition, the catalyst particles in a slurry bed reactor circulate continuously through the whole slurry bed, so that all particles frequently pass through zones of high P_H2o- In a fixed bed reactor, the catalyst particles are stationary and the P_H2o increases from the reactor inlet to the outlet; accordingly, a much smaller part of the catalyst bed is exposed to the higher P_H2o-

The art teaches of silicon carbide (SiC) as a support for catalysts. In particular, silicon carbide has been identified as a support for catalysts in Ledoux et a/., J Catal. 114 (1988) 176-188; Philippe et al., Catal Today 147S (2009) S305-S312; De la Osa er a/., Catalysis Today 176 (2011) 298-302; Nguyen et al., Appl. Catal. 391 (2011) 443-454; Lacroix et al., Appl. Catal. 397 (2011 ) 62-72; US Patent No. 7,393,877; International Application No. WO 2007/000506; US Patent No. 5,677,257; Tymowskia, Applied Catalysis A: General 419- 420 (2012) 31- 40; De la Osa et al., Fuel 95 (2012) 587-598; and De la Osa., Catalysis Today (2012), doil 0.1016/j.cattod.2011.12.029.

From the above prior art, it is known to use silicon carbide as a support for a cobalt-based supported catalyst in FTS. However, a known reason for a cobalt-based supported FTS catalyst to deactivate under high P_H2o conditions is that the high P_H2o causes the cobalt crystallites dispersed on the catalyst support to sinter into larger cobalt crystallites resulting in a catalyst with lower FTS activity. Accordingly, the catalyst support should interact sufficiently with the cobalt crystallites to reduce sintering.

Silicon carbide is also known for its chemical inertness (see, for example, De la Osa, Fuel 95 (2012) 587, page 587, second column, last 4 lines to page 588, first column, first 4 lines) and although it has been used as a catalyst support on an experimental basis, it would be expected that the interaction of the cobalt with the silicon carbide support would be low due to the chemical inertness of this support. Low interaction with the supported cobalt would be expected to cause sintering of the cobalt and result in deactivation during FTS at a high P_H2_O. especially for FTS carried out in a slurry bed FTS reactor.

Most surprisingly, it has now been found that when a cobalt-based silicon carbide supported catalyst is prepared, as set out below, and used in slurry bed FTS at a high P_H2o the catalyst demonstrates low or no deactivation under these conditions. DISCLOSURE OF THE INVENTION

According to the present invention, there is provided a process for producing hydrocarbons and, optionally, oxygenates of hydrocarbons, the process including:

contacting syngas, which includes a mixture of hydrogen and carbon monoxide, with a cobalt-based supported catalyst in a slurry bed of a slurry bed reactor at a temperature above 180°C in the slurry bed, a pressure of at least 10 bar(a) (1000 kPa(a)) in the slurry bed and a water partial pressure (Ρ_Η2ο) reaching at least 5 bar(a) (500 kPa(a)) in the slurry bed;

wherein: the cobalt-based supported catalyst has been prepared by

(i) introducing a cobalt compound onto and/or into a particulate silicon carbide catalyst support to provide a cobalt loaded silicon carbide catalyst support;

(ii) calcining the cobalt loaded silicon carbide catalyst support under non-reducing conditions at a temperature above 400°C to provide a catalyst precursor; and

(iii) reducing the catalyst precursor to activate the catalyst precursor and thus providing a cobalt-based supported catalyst.

The silicon carbide catalyst support

The particulate silicon carbide catalyst support may be any suitable silicon carbide support for supporting cobalt or a cobalt compound thereon, provided that the silicon carbide catalyst support is suitable for use as a support in a catalyst for producing hydrocarbons and, optionally, oxygenates of hydrocarbons from at least hydrogen and carbon monoxide.

Preferably, the catalyst is a Fischer-Tropsch (FT) synthesis catalyst to be used in a three phase slurry bed FT synthesis process.

Preferably, the silicon carbide catalyst support contains more than 50% by weight silicon carbide, preferably more than 90% by weight silicon carbide. More preferably, the support (excluding promoters and dopants) consists of substantially 100% by weight silicon carbide.

Preferably, the silicon carbide in the support includes more than 50% by weight beta-SiC, preferably above 90% by weight beta-SiC, and preferably substantially 100% by weight beta- SiC. Preferably, the silicon carbide catalyst support includes an outer layer of Si0₂. The outer layer may be formed by treating the silicon carbide of the silicon carbide support in air. The silicon carbide catalyst support may be a beta-SiC support supplied by Sicat Sari.

The particulate silicon carbide catalyst support is usually porous. The incipient wetness support pore volume may be between 0.1 and 1ml/g catalyst support, and in one embodiment of the invention it may be 0.19 ml/g catalyst support, or even above 0.3 ml/g catalyst support. The incipient wetness support pore volume is defined as the pore volume as determined by adding water to the support until external wetting is observed. The catalyst support may have a support surface above 20 m²/g catalyst support, and in one embodiment of the invention it may be 28 m²/g catalyst support, or even about 40 m²/g catalyst support. The catalyst support may be pre-shaped. The catalyst support may be in the form of crushed and sieved particles. The particulate support may have an average particle size of between 1 and 500 micrometers, preferably between 10 and 250 micrometers, more preferably between 38 and 150 micrometers.

The cobalt loaded silicon carbide catalyst support

The cobalt loaded silicon carbide catalyst support is prepared by introducing a cobalt compound onto and/or into the particulate silicon carbide catalyst support.

The cobalt compound may be an organic cobalt compound, but preferably it is an inorganic cobalt compound. The cobalt compound may be a cobalt salt, preferably an inorganic cobalt salt. The inorganic cobalt salt may be cobalt nitrate, preferably Co(N0₃)₂.6H₂0.

The cobalt compound may be introduced onto and/or into the catalyst support by any suitable manner, but preferably it is by means of impregnation. Preferably, the catalyst support is impregnated by the cobalt compound by forming a mixture of the cobalt compound; a liquid carrier for the cobalt compound; and the catalyst support.

The liquid carrier may comprise a solvent for the cobalt compound and preferably the cobalt compound is dissolved in the liquid carrier. The liquid carrier may be water.

The impregnation may be effected by any suitable impregnation method, including incipient wetness impregnation or slurry phase impregnation. Slurry phase impregnation is preferred. Preferably, the cobalt compound is dissolved in the liquid carrier in order that the volume of the solution is greater than xy litre, which solution is then mixed with the catalyst support, and wherein x is the BET pore volume of the catalyst support in ml/g support, and y is the mass of catalyst support to be impregnated in kg. Preferably, the volume of the solution is greater than 1.5 xy litre, and preferably it is about 2 xy litre.

The impregnation may be carried out at sub-atmospheric pressure, preferably below 85 kPa(a), preferably at 20kPa(a) and lower. Preferably, the impregnation is also carried out at a temperature above 25°C. Preferably, the temperature is above 40°C, preferably above 60°C, but preferably not above 95°C.

The impregnation may be followed by partial drying of the impregnated support, preferably at a temperature above 25°C. Preferably, the temperature is above 40°C, preferably above 60°C, but preferably not above 95°C. Preferably the partial drying may be effected at sub- atmospheric conditions, preferably below 85kPa(a), preferably at 20kPa(a) and lower.

In one embodiment of the invention, the impregnation and partial drying may be carried out in a procedure which includes a first step wherein the catalyst support is impregnated (preferably slurry impregnated) with the cobalt compound at a temperature above 25°C, and at sub-atmospheric pressure, and the resultant product is dried; and at least one subsequent step wherein the resulting partially dried impregnated catalyst support of the first step is subjected to treatment at a temperature above 25°C, and sub-atmospheric pressure such that the temperature of the subsequent step exceeds that in the first step and/or the sub- atmospheric pressure in the subsequent step is lower than that in the first step. This two step impregnation may be the process as described in WO 00/20116, which is incorporated herein by reference.

A dopant capable of enhancing the reducibility of the cobalt in the cobalt compound may also be introduced onto and/or into the catalyst support. The dopant may be introduced during or after the introduction of the cobalt compound onto and/or into the catalyst support. The dopant may be introduced as a dopant compound which is a compound of a metal selected from the group including palladium (Pd), platinum (Pt), ruthenium (Ru), rhenium (Re) and a mixture of one or more thereof. Preferably, the dopant compound is an inorganic salt, and preferably it is soluble in water. The dopant may be introduced to be present at mass proportion of the metal of the dopant to cobalt at 1 :300 to 1 :3000. The catalyst precursor

The catalyst precursor is formed by calcining the cobalt loaded silicon carbide catalyst support under non-reducing conditions at a temperature above 400°C.

Preferably, the calcination is carried out after partial drying of the impregnated support, as described above.

The calcination may be effected to form one or more cobalt oxide compounds, preferably by decomposing the cobalt compound and/or causing the cobalt compound to react with oxygen. For example, cobalt nitrate may be converted into a compound selected from CoO, CoO(OH), C03O4, Co₂0₃ or a mixture of one or more thereof.

The calcination may be carried out in an inert atmosphere, but preferably it is carried out under oxidation conditions, preferably in an oxygen containing atmosphere, preferably in air.

The calcination may be carried out in any suitable manner such as in a rotary kiln, but preferably it is carried out in a fluidised bed reactor.

Preferably, the calcination is carried out at a temperature of at least 450°C, preferably of at least 500°C, and preferably at about 550°C and even above 550°C, but preferably not above 750°C, preferably not above 650°C.

The calcination may be carried out by using a heating rate and an air space velocity that complies with the following criteria:

(i) when the heating rate is≤ 1 °C/min, the air space velocity is at least 0.76 m_n ³/(kg Co(N0₃)₂-6H₂0)/h; and

(ii) when the heating rate is higher than 1°C/min, the air space velocity satisfies the relation: log 20 - log 0.76

log (space velocity) > log 0.76 + log ( heating rate )

2

The impregnation, the partial drying and calcination may be repeated to achieve higher loadings of the catalyst precursor compound on the catalyst support. The cobalt-based supported catalyst

Preferably, the cobalt-based supported catalyst is formed by reducing the catalyst precursor at an elevated temperature, preferably of at least 200°C, more preferably at least 300°C, and most preferably at least 400°C, to activate the catalyst precursor.

The temperature during reduction is preferably at least 450°C, more preferably at least 500°C, most preferably about 550°C and even above. During reduction, cobalt metal is formed.

The catalyst precursor is preferably treated with a reducing gas to activate the catalyst precursor. Preferably, the reducing gas is hydrogen or a hydrogen containing gas. The hydrogen containing gas may consist of hydrogen and one or more inert gases which are inert in respect of the active catalyst. The hydrogen containing gas preferably contains at least 90 volume % hydrogen. Alternatively, the reducing gas may also be a carbon monoxide containing gas. The catalyst may also be activated by treating it with different types of reducing gases in subsequent stages of the activation procedure.

The reducing gas may be contacted with the catalyst precursor in any suitable manner. Preferably, the catalyst precursor is provided in the form of a bed of particles with the reducing gas being caused to flow through the bed of particles. The bed of particles may be a fixed bed, but preferably it is a fluidised bed and preferably the reducing gas acts as the fluidising medium for the bed of catalyst precursor particles.

The reduction may be carried out at a pressure from 0.6 to 1.5 bar(a) (60 to 150 kPa(a)), preferably from 0.8 to 1.3 bar(a) (80 to 130 kPa(a)). Alternatively, the pressure may be from 1.5 to 20 bar(a) (150 to 2000 kPa(a)). Preferably, the pressure is at about atmospheric pressure.

During reduction, the temperature may be varied, and preferably it is increased to a maximum temperature as set out above.

The flow of the reducing gas through the catalyst bed is preferably controlled to ensure that contaminants produced during reduction are maintained at a sufficiently low level. The reducing gas may be recycled, and preferably the recycled reducing gas is treated to remove one or more contaminants produced during reduction. The contaminants may comprise one or more of water and ammonia.

The activation may be carried out in two or more steps during which one or more of the heating rate, the space velocity of the reducing gas and the reducing gas composition is varied.

The cobalt-based supported catalyst may include a cobalt loading in an amount of more than 12 g Co/100g catalyst support. Preferably, the cobalt loading is more than 15 g Co/100g catalyst support.

In one embodiment of the invention, the catalyst may be coated by a coating medium (preferably a wax), preferably by introducing a mixture of the catalyst particles and a coating medium, in the form of a molten organic substance (preferably a wax), which is at a temperature T^ and which sets or congeals at a lower temperature T₂ so that T₂<T₁, into at least one mould; and at least partly submerging the mould in a cooling liquid, so as to cool the organic substance down to a temperature T₃, where T₃≤T₂.

Hydrocarbon synthesis

Preferably, the hydrocarbon synthesis process is a three phase slurry bed Fischer-Tropsch process for producing hydrocarbons and, optionally oxygenates of hydrocarbons.

The hydrocarbon synthesis may be carried out in any suitable slurry bed reactor comprising a reactor vessel containing the cobalt-based supported catalyst in a liquid medium (preferably an organic substance, preferably a wax). Examples of such reactors, which are also called slurry phase reactors, slurry bubble column reactors or the like, are provided in the art, e.g. FT Technology, Stud. Surf. Sci. Cat. Vol. 152, Chapter 2.

The slurry bed may be in a churn-turbulent flow regime, and preferably the slurry bed reactor has a diameter of more than 1m.

The slurry bed temperature during the hydrocarbon synthesis process is at least 180°C, preferably at least 200°C, preferably at least 220°C, and more preferably about 230°C. Preferably, the temperature is below 250°C. The pressure in the slurry bed during hydrocarbon synthesis is preferably at least 20 bar(a) (2000 kPa(a)), preferably about 30 bar(a) (3000 kPa(a)). Preferably, the pressure is below 70 bar(a) (7000 kPa(a)).

Preferably, the water partial pressure (P_H2_O) reached in the slurry bed is above 7 bar(a) (700kPa(a)) and most preferably it is above 9 bar(a) (900 kPa(a)). Preferably, the said P_H2o is also reached in the gas leaving the slurry bed.

A person skilled in the art would understand that the required P_H2o can be achieved in various ways, including by increasing the catalyst activity, increasing the temperature, increasing the total pressure, increasing the amount of catalyst loaded, decreasing the space velocity, and combinations hereof.

According to another aspect of the present invention, there is provided a process for producing hydrocarbons and, optionally, oxygenates of hydrocarbons, the process including:

(a) preparing a cobalt-based supported catalyst by

(ii) calcining the cobalt loaded silicon carbide catalyst support under non- reducing conditions at a temperature above 400°C to provide a catalyst precursor; and

(iii) reducing the catalyst precursor to activate the catalyst precursor and thus providing a cobalt-based supported catalyst;

and

(b) contacting syngas, which includes a mixture of hydrogen and carbon monoxide, with the cobalt-based supported catalyst in a slurry bed of a slurry bed reactor at a temperature above 180°C in the slurry bed, a pressure of at least 10 bar(a) (1000 kPa(a)) in the slurry bed and a water partial pressure (Ρ_Η2ο) reaching at least 5 bar(a) (500 kPa(a)) in the slurry bed.

The process may also include a hydroprocessing step for converting the hydrocarbons and, optionally, oxygenates thereof to liquid fuels and/or chemicals.

According to yet another aspect of the present invention, there is provided the use of a cobalt-based supported catalyst in a process for producing hydrocarbons by contacting syngas, which includes a mixture of hydrogen and carbon monoxide, with the cobalt-based supported catalyst in a slurry bed of a slurry bed reactor at a temperature above 180°C in the slurry bed, a pressure of at least 10 bar(a) (1000 kPa(a)) in the slurry bed and a water partial pressure (P_H2o) reaching at least 5 bar(a) (500 kPa(a)) in the slurry bed;

wherein: the cobalt-based supported catalyst has been prepared by

It will be appreciated that when the cobalt-based silicon carbide supported catalyst is prepared, as set out herein above, and used in the slurry bed FTS process of the present invention at a high P_H2o. the catalyst demonstrates low or no deactivation under these conditions and the use thereof results in reduced deactivation of the catalyst.

According to yet another aspect of the present invention there is provided hydrocarbon synthesis products produced by the processes as described above.

The invention will now be described in more detail with reference to the following non-limiting examples.

EXAMPLES

Example 1 - Preparation of a silicon carbide (SiC) catalyst support

A standard crushed and sieved (that is, particulate) beta-SiC catalyst support was supplied by the company Sicat Sari. The particle size distribution of this material ranged from a diameter of 38 pm to 150 pm, the incipient wetness pore volume was 0.19 ml/g. The surface area was 28 m²/g, as analysed by the technique of N₂ Sorptometry. The SiC support includes a Si0₂ outer layer of a few nanometers.

Example 2 (Comparative)

The support material of Example 1 was impregnated with a cobalt compound, by applying a slurry phase impregnation method with an aqueous cobalt nitrate solution followed by vacuum drying using the following procedure:

10 minutes at 60°C and 100 kPa(a); 30 minutes at 60°C and 20 kPa(a); 90 minutes at 75°C and 20 kPa(a); 60 minutes at 85°C and 20 kPa(a); and 240 minutes at 85°C and 5 kPa(a) (as also described in US 6,455,462) to provide a cobalt loaded silicon carbide catalyst support.

After drying, the intermediate material (the cobalt loaded silicon carbide catalyst support) was calcined in air at 250°C in a fluidised bed reactor, using a heating rate of 1°C/min and a space velocity of 1.0 Nm³/(kg Co(N0₃)₂.6H₂0.hr) (as also described in US 6,806,226). Three subsequent impregnation and calcination steps were executed to obtain a catalyst precursor with the targeted cobalt loading. The cobalt content of this catalyst precursor was 13 mass%, i.e. [15.9g Co/100g β-SiC].

The calcined catalyst precursor was activated (i.e. reduced in a dynamic environment of pure H₂) at atmospheric pressure during which the temperature was increased from 25°C to 550°C at a rate of 1.0°C/minute at a pure H₂ flow of 23 ml_n/(minute . g catalyst) whereafter it was kept isothermally at 550°C for 4 hours at a pure H₂ flow of 23 ml_n/(minute . g catalyst) to provide a cobalt-based supported catalyst. Subsequently, the catalyst was cooled down in hydrogen to room temperature and loaded under an argon blanket in molten Fischer- Tropsch wax, ensuring proper protection of the cobalt-based supported catalyst from the atmosphere.

Example 3 (Inventive)

This catalyst was prepared according to the procedures of Example 2, except that the calcination was executed at a temperature of 450°C.

Example 4 (Inventive)

This catalyst was prepared according to the procedures of Example 2, except that the calcination was executed at a temperature of 550°C.

Example 5 (Inventive)

This catalyst was prepared according to the procedures of Example 2, except that the calcination was executed at a temperature of 650°C.

Example 6 (Inventive)

This catalyst was prepared according to the procedures of Example 2, except that the calcination was executed at a temperature of 750°C.

Example 7 (Comparative)

A standard Sasol Germany Puralox 2/150 gamma alumina support was impregnated with cobalt and platinum, a slurry impregnation method as per Example 2 was applied, followed by calcination and reduction as per Example 2.

Two subsequent impregnation and calcination steps were executed to obtain a catalyst precursor with the targeted cobalt loading. The cobalt content of this catalyst precursor was 23 mass%, i.e. [30g Co/100g Al₂0₃], and the platinum content was 0.05 mass%. Example 8

The activated and wax protected catalysts of Examples 2 to 7 were tested for their slurry phase FTS performance in a laboratory micro slurry CSTR of about 700 ml volume at a reactor temperature of 230°C and a reactor pressure of 30 bar during which a pure H₂ and CO and Ar feed gas mixture was utilised with a 10 volume% Ar content and a molar H₂/CO ratio of 2.1.

The gas space velocity was changed to such an extent that the catalyst performance was determined first at P_H2o of 500 kPa(a) and thereafter at P_H2o of 1000 kPa(a). The P_H2o is measured at the outlet of the laboratory CSTR, but due to the nature of a CSTR the complete catalyst inventory is exposed to this P 2 at all times during the experiment.

The intrinsic FTS activities were derived from the following published (Ind. Eng. Chem. Res.; 48(2009)10439-10447) reaction equation: = kpxs [ (Pco⁰⁵⁰ P 2^0'75 ) / ( 1 + (1.58 baf¹)P_Co⁰-⁵⁰)²] where: rrrs = moles CO converted to FTS products excluding C0₂, per gram of freshly calcined catalyst precursor per second as measured at a catalytic effectiveness factor of one.

The FT stability of the catalyst Examples with respect to water partial pressures is expressed as S 2 = (activity after P 2 =900-1000 kPa(a) FT conditions for 1 day) / (activity after P 2 =400-500 kPa(a) FT conditions for 1 day).

FT stability of catalysts prepared in terms of the aforementioned Examples

SPH₂O = (activity after P_H2o=900-1000 kPa(a) FT conditions for 1 day) / (activity after P_H2o=400-500 kPa(a) FT conditions for 1 day)

It can be seen from Table 1 that the alumina-based catalyst lost a significant amount of its activity when operated at conditions of high water partial pressures. The beta-SiC based catalysts are however very stable at high water partial pressures. Surprising, the catalyst calcined at 550°C even shows an increase in catalyst activity when subjected to high water partial pressures.

The FT activity of the SiC based catalysts (Examples 2 to 6) is shown in Table 2, and it can be seen that calcination of the impregnated and dried catalyst intermediate should be done in excess of 250°C to obtain catalysts with a high activity. Excellent methane selectivity is obtained for Examples 3, 4, 5 and 6, i.e. the catalysts calcined in excess of 250°C.

FT activity and methane selectivity pertaining to catalysts prepared in terms of Examples 2 to 6

^* As tested at between P_H2o=900-1000 kPa(a)

Example 9 (Comparative)

The activated and wax protected catalyst of Example 7 was tested in a similar manner as in Example 8, but for a longer period of time.

As can be seen from Figure 1 , the activity of this comparative catalyst decreases about 50% over a 4 day period (from day 4 to day 8) at a P_H2o of between about 600-900kPa(a).

Example 10 (Inventive)

The activated and wax protected catalyst of Example 4 was tested in a similar manner as in Example 8, but for a longer period of time.

As can be seen from Figure 2, the activity of this inventive catalyst decreases only about 10% over a 60 day period at a P_H2o of about 1 000 kPa(a).

Comparing Figures 1 and 2 clearly shows that the inventive catalyst is much more stable for a long period of time at high Ρ_Η2ο (>500 kPa(a)) than the comparative catalyst.

Claims

A process for producing hydrocarbons and, optionally, oxygenates of hydrocarbons, the process including:

contacting syngas, which includes a mixture of hydrogen and carbon monoxide, with a cobalt-based supported catalyst in a slurry bed of a slurry bed reactor at a temperature above 180°C in the slurry bed, a pressure of at least 10 bar(a) (1000 kPa(a)) in the slurry bed and a water partial pressure (P_H2o) reaching at least 5 bar(a) (500 kPa(a)) in the slurry bed;

wherein: the cobalt-based supported catalyst has been prepared by

The process according to claim 1 , wherein the particulate silicon carbide catalyst support contains more than 50% by weight silicon carbide.

The process according to claim 2, wherein the silicon carbide in the particulate silicon carbide catalyst support includes more than 50% by weight beta-SiC.

The process according to claim 2 or claim 3, wherein the silicon carbide catalyst support has an incipient wetness support pore volume of between 0.1 and 1ml/g catalyst support.

The process according to any one of claims 2 to 4, wherein the silicon carbide catalyst support has a support surface above 20 m²/g catalyst support.

The process according to any one of claims 2 to 5, wherein the silicon carbide catalyst support has an average particle size of between 1 and 500 micrometers.

7. The process according to claim 1, wherein the cobalt compound is introduced onto and/or into the silicon carbide catalyst support by means of impregnation to form an impregnated support.

8. The process according to claim 7, wherein the silicon carbide catalyst support is impregnated by the cobalt compound by forming a mixture of the cobalt compound; a liquid carrier for the cobalt compound; and the catalyst support.

9. The process according to claim 7 or claim 8, wherein impregnation is followed by partial drying of the impregnated support at a temperature above 25°C.

10. The process according to claim 1 or claim 9, wherein calcination is carried out after partial drying of the impregnated support.

11. The process according to claim 1 , wherein the catalyst precursor is activated by reducing the said catalyst precursor at a temperature of at least 450°C, thereby providing a cobalt-based supported catalyst.

12. A process for producing hydrocarbons and, optionally, oxygenates of hydrocarbons, the process including:

(a) preparing a cobalt-based supported catalyst by

and

(b) contacting syngas, which includes a mixture of hydrogen and carbon monoxide, with the cobalt-based supported catalyst in a slurry bed of a slurry bed reactor at a temperature above 180°C in the slurry bed, a pressure of at least 10 bar(a) (1000 kPa(a)) in the slurry bed and a water partial pressure (PH2O) reaching at least 5 bar(a) (500 kPa(a)) in the slurry bed.

Use of a cobalt-based supported catalyst in a process for producing hydrocarbons by contacting syngas, which includes a mixture of hydrogen and carbon monoxide, with the cobalt-based supported catalyst in a slurry bed of a slurry bed reactor at a temperature above 180°C in the slurry bed, a pressure of at least 10 bar(a) (1000 kPa(a)) in the slurry bed and a water partial pressure (PH2O) reaching at least 5 bar(a) (500 kPa(a)) in the slurry bed;

wherein: the cobalt-based supported catalyst has been prepared by

14. A hydrocarbon synthesis product produced by the process of any one of claims 1 to 12.