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  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/74—Iron group metals
  • B01J23/75—Cobalt
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  • B01J37/02—Impregnation, coating or precipitation
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  • B01J37/0203—Impregnation the impregnation liquid containing organic compounds
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  • B01J37/16—Reducing
  • B01J37/18—Reducing with gases containing free hydrogen
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G2/00—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon
  • C10G2/30—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen
  • C10G2/32—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts
  • C10G2/33—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used
  • C10G2/331—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used containing group VIII-metals
  • C10G2/332—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used containing group VIII-metals of the iron-group
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G2/00—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon
  • C10G2/30—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen
  • C10G2/32—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts
  • C10G2/33—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used
  • C10G2/331—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used containing group VIII-metals
  • C10G2/333—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used containing group VIII-metals of the platinum-group
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  • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
  • B01J21/02—Boron or aluminium; Oxides or hydroxides thereof
  • B01J21/04—Alumina
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  • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
  • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
  • B01J21/08—Silica
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  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
  • B01J23/84—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J23/843—Arsenic, antimony or bismuth
  • B01J23/8437—Bismuth
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  • B01J37/08—Heat treatment

Definitions

• This invention relates to cobalt catalysts and in particular cobalt catalysts suitable for the
• Cobalt catalysts suitable for use in the Fischer Tropsch process for synthesising hydrocarbons are generally subjected to pre-reduction and encapsulation in a suitable material prior to installation in the Fischer-Tropsch reactor. This is because the reduction processes typically are operated at temperatures > 25O 0 C, and in particular >300°C, which are challenging for the fixed bed or slurry phase reactors used. Furthermore reduction is typically performed using hydrogen gas streams, and the gas streams available for in-situ reduction generally comprise synthesis gas mixtures containing carbon monoxide. Whereas in-situ reduction of cobalt Fischer-Tropsch catalysts is a desired aim, heretofore such processes have not been commercially used.
• the invention provides a catalyst precursor comprising 5 to 50% by weight of one or more oxidic cobalt compounds selected from CoO, CoO(OH) and Co 3 O 4 and 0.05 to 10% by weight of one or more reduction promoters selected from metals or compounds of Ru, Pt, Cu, Rh, Pd, Ir, Ag and Bi, supported on an inert support selected from alpha alumina, a metal- aluminate, silica, titania, zirconia, zinc oxide, silicon carbide, carbon or mixtures thereof, wherein the cobalt is in a highly reducible form such that at least 75% of the cobalt is reducible by a reducing gas stream at temperatures ⁇ 24O 0 C.
• the cobalt is present in a highly reducible form so that the oxidic cobalt compound may be effectively reduced by a reducing gas stream at temperatures ⁇ 24O 0 C.
• the degree of reduction i.e. the amount of cobalt reduced is >75% wt, preferably >85% wt, more preferably >90% wt of the Co present in the catalyst precursor.
• the invention further provides a process for activating a catalyst comprising placing the above catalyst precursor in a Fischer-Tropsch reactor and passing a reducing gas mixture over the catalyst precursor for a period of time to reduce cobalt present therein to elemental form, wherein the temperature of the reducing gas mixture throughout the activation step is ⁇ 24O 0 C.
• the invention further provides a process for the Fischer-Tropsch synthesis of hydrocarbons comprising the step of passing a gas mixture comprising hydrogen and carbon monoxide over a catalyst in a Fischer-Tropsch reactor wherein the catalyst has been activated by passing a reducing gas mixture at a temperature of ⁇ 24O 0 C over the above catalyst precursor in the Fischer Tropsch reactor,.
• the cobalt content of the catalyst precursor is in the range 5 to 50% by weight, preferably 10 to 35% by weight, most preferably 12 to 30% by weight.
• the additive or promoter content of the catalyst precursor is in the range 0.05 to 10% by weight, preferably 0.1 to 5% wt, most preferably 0.1 to 2% by weight .
• the total amount of additive or promoter in the catalyst precursor is preferably ⁇ 10% by weight.
• the metal contents may be determined using known methods such as ICP AES or ICP OES.
• the cobalt is in reducible form, i.e. preferably ⁇ 5% by weight, more preferably ⁇ 1 % by weight, most preferably ⁇ 0.05% by weight and especially none of the cobalt is in the form of a cobalt-support mixed oxide such as cobalt aluminate.
• the reducible cobalt is present as one or more of CoO, CoO(OH) and Co 3 O 4 .
• substantially all of the reducible cobalt is present as Co 3 O 4 .
• DOR degree of reduction
• a temperature-programmed reduction (TPR) method for estimating DOR may be used as follows:
• the reduction promoter in the present invention is selected from one or more compounds or metals of Ru, Pt, Cu, Rh, Pd, Ir, Ag and Bi, preferably one or more of Ru, Pt and Cu, more preferably Ru.
• the inert support in the present invention is one that is inert to the cobalt, i.e. does not readily form mixed oxides of cobalt, such as cobalt aluminate spinels.
• the inert support is selected from alpha alumina, a metal-aluminate, silica, titania, zirconia, zinc oxide, silicon carbide, carbon or mixtures thereof.
• the support and hence the resulting catalyst precursor may be in the form of a powder having a surface-weighted mean diameter D[3,2] in the range 1 to 200 microns.
• the term surface- weighted mean diameter D[3,2], otherwise termed the Sauter mean diameter, is defined by M.
• the support may be in the form of a monolith, e.g. a honeycomb, or a cellular material such as an open foam structure.
• the inert support may also be in the form of a wash-coat on a ceramic, metal, carbon or polymer substrate.
• Such catalysts advantageously offer in-situ reduction in micro GTL equipment.
• Carbon supports such as activated carbons, high surface area graphites, carbon nanofibres, and fullerenes in powder, pellet or granular form and having suitable porosities, e.g. above 0.1 ml/g may be used as supports for the present invention. Such supports are preferably not used in methods where air calcination is employed because of oxidation of the support.
• catalyst precursors comprising carbon supports are produced where the gas stream to which the carbon is exposed during calcination contains preferably ⁇ 1 %, more preferably ⁇ 0.1 %, oxygen by volume, e.g. oxygen free nitrogen, helium or argon.
• the support may be a silica support.
• Silica supports may be formed from natural sources, e.g. as kieselguhr, may be a pyrogenic or fumed silica or may be a synthetic, e.g. precipitated silica or silica gel. Structured mesoporous silicas, such as SBA-15 may be used as a support. Precipitated silicas are preferred.
• the silica may be in the form of a powder or a shaped material, e.g. as extruded, pelleted or granulated silica pieces. Suitable powdered silicas typically have particles of surface weighted mean diameter D[3,2] in the range 3 to 100 ⁇ m.
• Shaped silicas may have a variety of shapes and particle sizes, depending upon the mould or die used in their manufacture.
• the particles may have a cross-sectional shape which is circular, lobed or other shape and a length from about 1 to greater than 10 mm.
• the BET surface area of suitable powdered or granular silicas is generally in the range 10 - 500 m 2 /g, preferably 100 - 400 m 2 g ⁇
• the pore volume is generally between about 0.1 and 4 ml/g, preferably 0.2 - 2 ml/g and the mean pore diameter is preferably in the range from 0.4 to about 30 nm.
• the silica may be mixed with another metal oxide, such as titania or zirconia.
• the silica may alternatively be present as a coating on a shaped unit, which is preferably of alumina typically as a coating of 0.5 to 5 monolayers of silica upon the underlying support.
• the support may be a titania support. Titania supports are preferably synthetic, e.g. precipitated titanias.
• the titania may optionally comprise e.g. up to 20% by weight of another refractory oxide material, typically silica, alumina or zirconia.
• the titania may alternatively be present as a coating on a support which is preferably of silica or alumina, for example as a coating of 0.5 to 5 monolayers of titania upon the underlying alumina or silica support.
• the BET surface area of suitable titania is generally in the range 10 - 500 m 2 /g, preferably 100 to 400 m 2 /g.
• the pore volume of the titania is preferably between about 0.1 and 4 ml/g, more preferably 0.2 to 2 ml/g and the mean pore diameter is preferably in the range from 2 to about 30 nm.
• zirconia supports maybe synthetic, e.g. precipitated zirconias.
• the zirconia may again optionally comprise e.g. up to 20% by weight of another refractory oxide material, typically silica, alumina or titania.
• the zirconia may be stabilised e.g. an yttria- or ceria- stabilised zirconia.
• the zirconia may alternatively be present as a coating on a support, which is preferably of silica or alumina, for example as a coating of 0.5 to 5 monolayers of zirconia upon the underlying alumina or silica support.
• the support may be a metal aluminate, for example a calcium aluminate.
• the inert support is alpha-alumina.
• the alpha alumina may be obtained commercially or made by heating transition aluminas, e.g. gamma-alumina, to temperatures in the range 1000-1500 0 C, preferably >1200°C.
• the alpha alumina is preferably reasonably pure with an alkali content ⁇ 100ppm, preferably ⁇ 50 ppm and substantially no metal aluminate spinel present.
• the BET surface area is preferably ⁇ 50m 2 /g.
• a suitable alpha alumina powder generally has a surface-weighted mean diameter D[3,2] in the range 1 to 200 ⁇ m.
• the alumina support material may be in the form of a spray dried powder or formed into shaped units such as spheres, pellets, cylinders, rings, or multi-holed pellets, which may be multi-lobed or fluted, e.g. of cloverleaf cross-section, or in the form of extrudates known to those skilled in the art.
• the alpha alumina support may be advantageously chosen for high filterability and attrition resistance.
• Alpha-alumina supported cobalt Fischer-Tropsch catalysts are known.
• WO 02/47816 describes cobalt catalysts on an alpha alumina or alpha alumina-containing support.
• the list of possible promoters given includes Re, Pt, Ir or Rh.
• reduction of the catalyst precursors was performed at 250-400 0 C, preferably 300-400 0 C.
• Metal-aluminate supports such as nickel aluminate, lithium aluminate or calcium aluminate supports may also be used in the present invention. These supports have the advantage of being unable to readily interact with the cobalt oxides formed thereon.
• the catalyst precursors may be prepared using known methods.
• the catalysts may be prepared using impregnation methods, precipitation methods or deposition precipitation methods, or a combination of these, generally followed by a drying step to remove any solvents and a calcination step to effect conversion of the cobalt and additive or promoter compounds to their respective oxides.
• the cobalt and promoter may be uniformly distributed within the support or may be in the form of an eggshell on its surface.
• the first method is particularly suitable when preparing catalysts on shaped supports such as extrudates or pellets, whereas the second method is particularly suitable for powder supports.
• a suitable soluble metal compounds for example the metal nitrate or acetate may be impregnated onto a support material from an aqueous or non-aqueous solution, e.g. ethanol, which may include other materials, and then dried to remove the solvent or solvents.
• aqueous or non-aqueous solution e.g. ethanol
• One or more soluble metal compounds may be present in the solution.
• One or more impregnation steps may be performed, with or without intervening drying and/or calcination steps, to increase metal loading or provide sequential layers of different metal compounds.
• Impregnation may be performed using any of the methods known to those skilled in the art of catalyst manufacture, but preferably is by way of a so-called 'dry' or 'incipient- wetness' impregnation as this minimises the quantity of solvent used and to be removed in drying.
• Incipient wetness impregnation comprises mixing the support material with only sufficient solution to fill the pores of the support.
• Impregnation methods for producing cobalt catalysts generally comprise combining a catalyst support with a solution of cobalt nitrate, e.g. cobalt (II) nitrate hexahydrate at a suitable concentration. Whereas a number of solvents may be used such as water, alcohols, ketones or mixtures of these, preferably the support has been impregnated using aqueous solutions of cobalt nitrate.
• the reduction promoter may also be included in the catalyst precursor by impregnation, using suitable soluble compounds such as the nitrate chloride, acetate, or mixtures of these.
• the additive or promoter may be included in the catalyst precursor before or after the cobalt, or at the same time by combining the cobalt and additive or promoter compounds in the same impregnating solution.
• the amount of cobalt and additive or promoter compound in solution, or the amount of inert support may be varied to achieve the desired metal loadings. Single or multiple impregnations may be performed to achieve the desired cobalt and additive or promoter levels in the catalyst precursor.
• the catalyst precursor is made by co-impregnating an inert support with a solution of ruthenium acetate and cobalt nitrate.
• the catalyst precursor may be dried to remove solvent prior to calcination.
• the drying step may be performed at 20-120 0 C, preferably 95-11O 0 C, in air or under an inert gas such as nitrogen, or in a vacuum oven.
• the catalyst precursor may then be heated in air to effect conversion of the cobalt and additive or promoter compounds to their respective oxides.
• the calcination temperature is preferably in the range 250 to 500 0 C.
• the calcination time is preferably ⁇ 24, more preferably ⁇ 16, most preferably ⁇ 8, especially ⁇ 6 hours.
• the dried catalyst precursor may be heated under an inert gas containing ⁇ 5 % volume oxygen such as nitrogen or argon, which may include nitric oxide or nitrous oxide at a concentration in the range 0.001 to 15% by volume.
• the drying and/or calcination steps may be carried out batch-wise or continuously, depending on the availability of process equipment and/or scale of operation.
• the method for making a catalyst precursor comprises the steps of
• the catalyst precursor may in addition to cobalt and one or more of Ru, Pt, Cu, Rh, Pd, Ir, Ag and Bi, further comprise one or more suitable additives useful in Fischer-Tropsch catalysis.
• the catalysts may comprise one or more additives that alter the physical properties and/or promoters that effect the reducibility or activity or selectivity of the catalysts.
• Suitable additives are selected from compounds of metals selected from molybdenum (Mo), iron (Fe), manganese (Mn), titanium (Ti), zirconium (Zr), lanthanum (La), cerium (Ce), chromium (Cr), magnesium (Mg) or zinc (Zn).
• the additives may be incorporated into the catalyst precursor by use of suitable compounds such as acids, metal salts, e.g. metal nitrates or metal acetates, or suitable metal-organic compounds, such as metal alkoxides or metal acetylacetonates. Typical amounts of the additives are 0.1 - 10% metal by weight on catalyst precursor. If desired, the compounds of the additional additives may be added in suitable amounts to the cobalt solution. Alternatively, they may be combined with the catalyst precursor before or after drying or calcination.
• At least a portion of the cobalt oxide may be reduced to the metal.
• Reducing gas streams that may be used include hydrogen- and/or carbon monoxide-containing gases. Reduction is preferably performed using hydrogen-containing gasses at elevated temperature.
• the temperature of the reducing gas stream, and hence the catalyst precursor, during the entire reduction stage is ⁇ 24O 0 C, preferably ⁇ 23O 0 C, more preferably ⁇ 225 0 C.
• the minimum reduction temperature is preferably 9O 0 C, more preferably 100°C, although higher temperatures may speed up reduction and a particularly preferred reduction temperature range is 180-240°C.
• the catalyst precursor may, if desired, be formed into shaped units suitable for the process for which the catalyst is intended, using methods known to those skilled in the art.
• the catalysts are desirably reduced in-situ, i.e. in the reactor in which they are to be used.
• Fischer Tropsch reactors take a variety of forms including fixed bed reactors in which a gas stream comprising carbon monoxide and hydrogen is passed through one or more beds of a particulate or monolithic catalyst, including catalyst supported on a wash-coated ceramic or metal substrate; and slurry phase reactors in which a gas stream comprising hydrogen and carbon monoxide is passed through a slurry of particulate catalyst in a suitable liquid medium.
• Such reactors include the well-known slurry bubble column reactors (SBCR's).
• the reduction also termed activation, may be performed by passing a reducing gas stream such as hydrogen, synthesis gas (a gas mixture comprising hydrogen, carbon monoxide and/or carbon dioxide) or a mixture of hydrogen and/or carbon monoxide with nitrogen or other inert gas over the oxidic composition at elevated temperature, for example by passing the hydrogen- containing gas over the catalyst precursor at temperatures in the range 140-240 0 C, preferably 160-220 0 C for between 1 and 16 hours, preferably 1 - 8 hours.
• the reducing gas stream comprises hydrogen at >25% vol, more preferably >50% vol, most preferably >75%, especially >90% vol hydrogen.
• At least 90% of the reducible cobalt is reduced at ⁇ 24O 0 C.
• the cobalt surface areas of the reduced catalysts may be determined by H 2 chemisorption using known methods.
• Reduction may be performed at ambient pressure or increased pressure, i.e. the pressure of the reducing gas may suitably be from 1-50, preferably 1-20, more preferably 1-10 bar abs. Higher pressures >10 bar abs may be more appropriate where the reduction is performed in- situ.
• the gas-hourly-space velocity (GHSV) for the reducing gas stream may be in the range 100- 25000hr "1 , preferably 1000 - 15000hr "1 .
• the catalyst is to be used in a SBCR
• a suitable liquid medium such as a molten hydrocarbon wax, e.g. a C6 to C40 hydrocarbon mixture
• the solids content of such a slurry is preferably in the range 1 to 50% w/v, more preferably from 3 to 40% w/v, most preferably from 5 to 35 % w/v.
• the catalysts may be used for the Fischer-Tropsch synthesis of hydrocarbons.
• the Fischer-Tropsch synthesis of hydrocarbons with cobalt catalysts is well established.
• the Fischer-Tropsch synthesis converts a mixture of carbon monoxide and hydrogen to hydrocarbons.
• the mixture of carbon monoxide and hydrogen is typically a synthesis gas having a hydrogen: carbon monoxide ratio in the range 1.6-3.0:1 , preferably 1.7 - 2.5:1.
• the reaction may be performed in a continuous or batch process using one or more stirred slurry- phase reactors, bubble-column reactors, loop reactors or fluidised bed reactors.
• the process may be operated at pressures in the range 0.1-10Mpa and temperatures in the range 150- 35O 0 C.
• GHSV gas-hourly-space velocity
• TPR temperature-programmed reduction
• a gamma alumina (HP 14-150 available from Sasol Condea) was subjected to calcination in air at a temperature of 1400°C for sufficient time to convert it to alpha alumina.
• Examples 1(a) - (c) were prepared by a co-impregnation method.
• An impregnation solution was prepared by dissolving 5% wt ruthenium acetate in acetic acid and cobalt nitrate hexahydrate in demineralised water.
• the alpha alumina was treated with the solution by the dry impregnation method, dried at 105°C for 3 hours and calcined by heating to 400°C at 2°C/min, and holding at this temperature for 1 hour. The procedure was then repeated on the calcined material.
• the resulting catalyst precursor had a cobalt content of 17.8% by weight and a ruthenium content of 0.21 % by weight.
• Catalyst precursors were made in the same way using copper (II) nitrate and platinum nitrate to achieve a cobalt content of about 18% wt and reduction promoter level of about 1 % wt on the calcined material.
• a Co content of about 18% wt in a catalyst precursor corresponds to a Co content of about 20% in a reduced catalyst assuming all the Co is reduced).
• Comparative catalyst precursor materials containing about 18% wt Co and no promoter, or differing amounts of gold, lanthanum and rhenium were also prepared using the same co- impregnation method.
• Example 1 (d) was prepared by a sequential impregnation method: The alpha alumina was treated with a solution of cobalt nitrate hexahydrate by dry the impregnation method, dried at 105°C for 3 hours and calcined by heating to 400°C at 2°C/min, and holding at this temperature for 1 hour. This procedure was then repeated on the calcined material. The resulting alpha- alumina-supported cobalt oxide precursor was promoted by impregnation with 5% wt ruthenium acetate in acetic acid and then drying at 105 0 C for 3 hours. The resulting Ru-promoted catalyst precursor was not calcined. The analysis of the catalyst precursors gave the following;
• the ruthenium promoted catalyst gave the highest surface area result, followed by the Re- promoted catalyst.
• Temperature-programmed reduction (TPR) experiments can be useful in predicting the behaviour of catalysts during reduction in situ. Thermal conductivity measurements were made on a sample exposed to hydrogen over time with increasing temperature using an AMI-200 instrument available from Altamira Instruments. The TPR experiments were run using 70- 80mg of catalyst precursor in a quartz tube held in place by quartz wool plugs. The catalyst precursor was heated to 1000 0 C from ambient at a rate of 10°C/min under a flow of 30ml/min of 10% H 2 /Ar, and then held at 1000 0 C for ten minutes.
• Figures 1 - 4 depict Examples 1(a)-(d) respectively and show the thermal conductivity changes associated with the reduction of of Co 3 O 4 to CoO and then CoO to Co metal as the temperature is increased and with time.
• the figures show the copper, ruthenium and platinum containing catalysts to be reduced below 300°C and well below that of the corresponding un-promoted catalyst.
• the rhenium and lanthanum catalyst precursors were reduced at higher temperatures than the un-promoted catalyst precursor under these conditions. The results were as follows;
• a further comparative example was done using a catalyst prepared on the gamma alumina using the co-impregnation method described above.
• the gamma alumina used was HP14- 150.
• the resulting Co content of the precursor was 16.4% and the Ru content, 0.77%.
• the results were as follows;
• the degree of reduction obtained with the Ru or Pt catalyst is better than the copper catalyst or the catalyst prepared using gamma alumina.
• a platinum-promoted catalyst was prepared using the same method except that platinum nitrate was used,to obtain a catalyst precursor having an estimated cobalt content of 18% wt and an estimated Pt content of 1 % wt.
• TPR experiments were performed according to the method described in Example 1.
• the TPR plot of the silica-supported Ru-promoted Co catalyst is depicted in Figure 5, along with that of a comparable un-promoted catalyst precursor and clearly shows the lower reduction temperature for the catalyst precursors of the invention.
• the performance of Pt as a reduction promoter is similar to that of Ru. The results are given below.
• a two-step TPR experiment was also performed according to the method described in Example 1 and showed a degree of reduction of 86% for the Ru-promoted catalyst precursor.
• the catalyst precursor of Example 1(a) was used for the Fischer-Tropsch synthesis of hydrocarbons in a laboratory-scale tubular reactor. About 0.1 g of catalyst precursor mixed with SiC was placed in bed (ca. 4 mm ID by 50 mm depth) and reduced by passing a reducing gas stream through the bed using three different regimes; a) reduction at 21O 0 C for 7 hours under hydrogen gas, b) reduction at 21O 0 C for 7 hours under a synthesis gas comprising hydrogen and carbon monoxide at a ratio of 2:1 and, c) for comparison, reduction at 38O 0 C for 7 hours under hydrogen gas.

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