|Title of Invention||
"A PROCESS FOR THE FISCHER -TROPSCH SYNTHESIS OF HYDROCARBONS USING HIGH COBALT CONTENT, HIGH COBALT SURFACE AREA CATALYSTS"
|Abstract||A particulate catalyst is described comprising an intimate mixture of cobalt and aluminum compounds having cobalt and aluminum at an atomic ratio in the range 10:1 to 2:1 (C0:A), which when reduced at 425°C, has a cobalt surface area as measured by hydrogen chemisorptions at 150°C of at least 30 m2/g of catalyst. The catalyst is prepared by sequential precipitation of cobalt with aluminum ions in the presence of an alkaline precipitation agent. The catalyst may be used for the hydrogenation of unsaturated compounds or the Fischer-Tropic synthesis of hydrocarbons.|
The application relates to cobalt-alumina catalysts, as well as to the preparation and use
Supported cobalt catalysts wherein the cobalt is in its elemental or reduced state are well
known and find use in many reactions involving hydrogen such as hydrogenation reactions,
and the Fischer-Tropsch synthesis of hydrocarbons. The activity of the catalysts is believed to
be directly proportional to the cobalt surface area of the reduced catalysts, but in order to
achieve high cobalt surface areas, the cobalt should be well dispersed on the support.
Furthermore, to minimize reactor volume, the catalyst should preferably have as high a cobalt
content as possible. High cobalt contents also offer improved efficiency in catalyst recycle and
regeneration. However, as the cobalt content of a catalyst increases above 20% by weight (on
reduced catalyst) the cobalt becomes more difficult to disperse resulting in lower cobalt surface
areas. Cobalt is a relatively expensive metal and therefore there is a desire to improve the
cobalt dispersion (expressed as cobalt surface area per gram catalyst).
Preparation of cobalt-alumina catalysts has heretofore typically been by impregnation of cobalt
compounds into 'pre-formed' alumina materials or by precipitation of cobalt compounds from
solution in the presence of alumina powders or extrudates, followed usually by a heating step
and then, prior to use, reduction of the resulting cobalt compounds to elemental form using
Alternatively cobalt-alumina catalysts may be prepared by simultaneous co-precipitation of
cobalt (Co) and aluminium (Al) compounds by addition of a base. Khassin et al describe the
co-precipitation of Co2+ and AI3+ at ratios of 1:1, 1:1.3 and 1:2 to yield hydrotalcite-containing
materials. Upon calcination and reduction under hydrogen at 470-480°C these catalysts were
of low activity in the Fischer-Tropsch synthesis of hydrocarbons (see Journal of Molecular
Catalysis A: Chemical, 168, 2001, 193-207).
We have found surprisingly, that new high cobalt content, high cobalt surface area catalysts
suitable for the hydrogenation of unsaturated compounds or in the Fischer-Tropsch synthesis
of hydrocarbons may be obtained by the sequential precipitation of cobalt and aluminate ions
The present invention provides a particulate catalyst comprising an intimate mixture of cobalt
and aluminium compounds having cobalt and aluminium at an atomic ratio in the range 10:1 to
2:1 (Co:AI), which when reduced at 425°C, has a cobalt surface area as measured by
hydrogen chemisorption at 150°C of at least 30 m2/g of catalyst.
Preferably the atomic ratio of cobalt to aluminium of the catalysts is in the range 5:1 and 2.5:1,
more preferably between 4:1 and 3:1. Despite the high cobalt contents compared to the
impregnated or simultaneous co-precipitated catalysts previously known, the catalysts retain
high cobalt surface areas upon reduction. For example, stable catalysts with cobalt contents
>60% wt particularly >75% wt (reduced catalyst) may be prepared. It is believed that in order to
obtain the very high cobalt surface areas observed at these Co levels, the amount of reduced
cobalt is >60%, preferably £70%, of the cobalt present in the unreduced catalyst. An
advantage of such high cobalt contents is that catalyst recovery and recycling to obtain the
cobalt once the catalyst is spent becomes economically viable. This leads also to the further
benefit of a reduced waste-disposal burden.
The catalyst composition, which may also be termed catalyst precursor prior to reduction,
comprises intimately mixed cobalt and aluminium compounds in which cobalt compounds may
be supported on cobalt-aluminium compounds. Upon reduction the cobalt compounds are
readily reduced whereas the cobalt-aluminium compounds are more difficult to reduce. The
resulting structure is different to that obtainable by impregnation or simultaneous coprecipitation
techniques and provides improved catalyst performance. It is believed that prior to
activation at least a major portion of the aluminium in the catalysts of the present invention may
be in the form of one or more cobalt-aluminium compounds. By major portion we mean >50%
of the aluminium atoms. Preferably >75%, more preferably substantially all of the aluminium
has reacted to form cobalt aluminium compounds. This is in contrast to the supported catalysts
of the prior art wherein it is believed that a minor part of the aluminium is in the form of cobaltaluminium
compounds and a major part is alumina. The presence of cobalt-aluminium
compounds may be determined using vibrational spectroscopy, e.g. Raman or Infra-red
spectroscopy. Alternatively the presence of an intimate mixture of cobalt-aluminium
compounds may be determined using a temperature-programmed reduction (TPR) wherein
reduction with hydrogen is performed at 150-10uO°C and a TCD signal recorded that shows a
characteristic peak for, e.g. Co-AI hydrotalcite structures in the range 400-800°C.
The particle size of the catalysts expressed as surface-weighted mean diameter D[3,2] is
preferably in the range 5-100 f.im (microns). More preferably the particle size is in the range 5-
30 microns, especially 10-20 microns. Larger particles may be prepared by agglomeration.
The term surface-weighted mean diameter D[3,2], otherwise termed the Sauter mean diameter,
is defined by M. Alderliesten in the paper "A Nomenclature for Mean Particle Diameters"; Anal.
Proc., vol 21, May 1984, pages 167-172, and is calculated from the particle size analysis which
may conveniently be effected by laser diffraction for example using a Malvern Mastersizer.
The catalysts of the present invention have a porous structure with pore diameters preferably of
50-500 angstroms or larger, depending on the Co:AI ratio. For example, at a Co:AI atomic ratio
of 5:1, the pore diameters of the catalyst prior to reduction may be about 200-250 angstroms.
The pore volume of the catalyst prior to reduction is preferably >0.3 cm3/g, more preferably
0.4 cm3/g of catalyst.
The BET surface area of the catalyst prior to reduction is preferably between 50 and 250 rrr/g
of catalyst, more preferably >90 m2/g. The BET surface area and pore volume measurements
are suitably determined using nitrogen desorption using methods known to persons skilled in
the art. The average pore diameter may be calculated from (4 x pore volume)/BET surface
In addition to cobalt and aluminium compounds, the catalyst may comprise one or more
suitable additives and promoters useful in hydrogenation reactions and/or Fischer-Tropsch
catalysis. For example, the catalysts may comprise one or more additives that alter the
physicai properties and/or promoters that effect the reducibility or activity or selectivity of the
catalysts. Suitable additives are selected from compounds of molybdenum (Mo), nickel (Ni),
copper (Cu), iron (Fe), manganese (Mn), titanium (Ti), zirconium (Zr), lanthanum (La), cerium
(Ce), chromium (Cr), magnesium (Mg) or zinc (Zn). Suitable promoters include rhodium (Rh),
iridium (Ir), ruthenium (Ru), rhenium (Re), platinum (Pt) and palladium (Pd). Additives and/or
promoters may be incorporated into the catalysts by addition of suitable compounds such as
metal salts, e.g. metal nitrates or metal acetates, or suitable metal-organic compounds, such as
metal alkoxides or metal acetylacetonates, to the reaction mixtures.
The invention further provides a process for the preparation of a particuiate catalyst comprising
an intimate mixture of cobalt and aluminium compounds having cobalt and aluminium at an
atomic ratio in the range 10:1 to 2:1 (Co:AI), which when reduced at425°C, has a cobalt
surface area as measured by hydrogen chemisorption at 150°C of at least 30 m2/g of catalyst
comprising the steps of;
(i) precipitating an insoluble cobalt compound from an aqueous solution of a cobalt salt with
an excess alkaline precipitating agent,
(ii) adding a soluble aluminium compound
(iii) ageing the resulting precipitate in suspended form, and
(iv) recovering and drying the catalyst composition.
Hence, one or more insoluble cobalt compounds is precipitated from an aqueous solution of a
cobalt salt with an excess alkaline precipitating agent, which precipitate is subsequently
allowed to age in suspended form and is then collected, wherein, after the cobalt ions have
been precipitated, a soluble aluminium compound is added. The soluble aluminium compound
can be added as a solution but also as undissolved crystals. The soluble aluminium compound
being added after the cobalt ions have been substantially precipitated is e.g. aluminium nitrate,
sodium aluminate or alumina that dissolves at least partly in the excess alkali. Preferably the
soluble aluminium compound is aluminium nitrate or sodium aluminate, particularly sodium
By forming the aluminium 'support' in-situ by the sequential precipitation method described
herein, rather than using an alumina powder, pellet, extrudate or the like, the present invention
allows a degree of control over the resulting catalyst physical properties not previously
possible. In particular the separate manipulation of the precipitation and ageing steps allows a
degree of control not previously provided. For example, by increasing or decreasing the
temperature during the ageing step, the pore size of the catalyst may be controlled.
Furthermore, the particle size of the catalyst may be controlled by the degree of agitation of the
After precipitation and ageing according to the invention, the precipitate is recovered from the
liquid e.g. by centrifugation or filtration, usually washed, and dried. Subsequent activation of
the catalyst is typically performed by reduction of the cobalt compounds with a hydrogencontaining
gas at an elevated temperature using methods known to those skilled in the art. An
advantage of this preparative method is that calcination of the catalyst composition is not
required and accordingly that reduction of the dried precipitate leads directly to the high surface
area catalysts. However, in some cases it may be desirable to calcine the dried catalyst
precursor composition at temperatures in the range 200-800°C, preferably 200-600°C, more
preferably 200-400°C. Calcination may be under an inert gas such as nitrogen or argon or may
be in air to effect oxidation of the cobalt and/or aluminium compounds prior to activation.
Cobalt compounds which can be used as starting material for the catalysts are water-soluble
cobalt compounds such as nitrate, sulphate, acetate, chloride and formate. The solutions
which are charged to the precipitation reactor preferably contain between 10 and 100, more
preferably 10 and 80 grams cobalt per litre; especially preferred are solutions which contain
between 25 and 60 grams cobalt per litre.
If desired, suitable compounds of additives and/or promoters may be added to the solution of
cobalt compounds prior to precipitation.
Alkaline precipitation agents may be alkali metal hydroxide, alkali metal carbonate, alkali metal
bicarbonate, the corresponding ammonium compounds and mixtures of the above-mentioned
compounds. Ammonium carbonate may also be used. The concentration of the alkaline
solution which is fed into the precipitation reactor is preferably between 20 and 300 grams
alkaline material (calculated as anhydrous material) per litre (in as far as the solubility allows
this), more particularly between 50 and 250 grams per litre.
Preferably the precipitant solution comprises an alkali metal carbonate, particularly Na2CO-s,
more preferably the precipitant comprises NaOH and Na2CO3 with a mole ratio of
NaOH:Na2CO3 carbonate is used as precipitation agent, the cobalt is initially thought to precipitate in a prehydrotalcite-
like structure that readily accepts aluminium cations from solution thereby forming
stable cobalt-aluminium hydrotalcite-like structures during the ageing step.
It is convenient to use both solutions (of cobalt compound and alkaline compound) in almost
the same concentrations (expressed in equivalents), so that approximately the same volumes
can be reacted.
The cobalt-containing solution and the alkaline solution are added in such amounts per unit of
time that an excess of alkaline compound is present during the precipitation step, so that pH is
preferably in the range 7-11, more preferably 7-10.
The precipitation reactor preferably has such dimensions with respect to the amounts of liquid
pumped in that short average residence times can be obtained. Typically, average residence
times of between 0.1 sec. and 10 minutes, preferably between 0.2 sec. an 4.5 minutes may be
used in the precipitation reactor.
In a preferred embodiment, in which the precipitation step (step 1) is carried out continuously,
the amounts of solutions fed into the precipitation reactor are controlled by measuring,
optionally continuously, the normality or pH of the reactor effluent.
The temperature at which the precipitation takes place can be controlled by adjusting the
temperatures of the liquids fed into the precipitation reactor. Preferably the temperature is
maintained below 90°C, more preferably below 50°C, most preferably below 30°C. The
required vigorous agitation of the liquid in the precipitation reactor preferably takes place with a
mechanical energy input of between 5 and 2000 watts per kg of solution. More preferably the
agitation takes place with a mechanical energy input of 100 to 2000 watts per kg of solution.
The reaction mixture obtained from the precipitation reactor goes immediately thereafter to a
stirred post-reactor (ageing reactor) of a significantly higher capacity in which the suspension is
agitated and aged. At this stage, the soluble aluminium compound is added. The amount of
aluminium compound added is 0.1 to 0.5 mole aluminium ions per gram atom of cobalt in the
If desired, a soluble silicate compound may also be added with the aluminium source following
precipitation of the cobalt. Suitable soluble silicate compounds are e.g. waterglass, including
neutral waterglass and potassium silicate. The amount of silicate added may be from 0.05-1
mole per gram atom of cobalt, preferably between 0.1 and 0.5 mole.
Additives and/or and promoters may also be added at this stage in addition to, or as an
alternative to adding them to the cobalt solution prior to precipitation. Suitable amounts of
additives and/or promoters are from 0.5 to 10% wt, calculated on the weight of cobalt in the
Preferably the liquid in the ageing reactor during the ageing step is kept at a temperature
between 10 and 100°C, preferably 40°C and 100°C. In a continuous process where the
precipitant consists of sodium carbonate, the temperature is preferably in the range 40-60°C.
The pH in the ageing reactor will vary during the ageing step. The average pH in the ageing
reactor is preferably maintained in the range 6-11, more preferably 7-10, most preferably 8-10.
The precipitation step and also the maturing step can be carried out batch-wise (i.e.
discontinuously), continuously and semi-continuously (e.g. according to the cascade method).
The ageing step can be carried out in one or more reactors, the (total) average residence time
being maintained between 10 and 180 minutes, preferably between 30 and 150 minutes, more
preferably between 30 and 70 minutes. If more than one ageing reactor is used the conditions
may be the same or different. Alternatively the product may be fully aged in one" reactor then
passed to a storage vessel under conditions where no further ageing takes place. By 'fully
aged' we mean that substantially all the aluminium compound has been precipitated, preferably
in the form of cobalt aluminium compounds. For example the ageing reactor may discharge
product, in which substantially all the aluminium has reacted to form cobalt aluminium
compounds, into a stirred tank operated at room temperature (ca. 20°C).
The present process involving separate precipitation and ageing steps results in a catalyst
precursor of particle size and particle size distribution more suitable for filtration than a
simultaneously co-precipitated precursor. Improved filterability is of considerable importance in
both hydrogenation processes and the Fischer-Tropsch synthesis of hydrocarbons where more
efficient catalyst recovery is highly desirable.
The solid material recovered from the ageing reactor is preferably washed with water;
optionally containing some alkali or a surface active material, e.g. a non-ionic surfactant. Also,
an organic solvent, e.g. acetone can be advantageously used during washing. Drying
preferably takes place with hot air below 200°C. Spray-drying is preferred but freeze-drying is
Before the catalysts are activated by reduction, the dried composition 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 shaped units may be spheres, pellets, cylinders,
rings, or multi-holed pellets, which may be multi-lobed or fluted, e.g. of cloverleaf cross-section.
Reduction may be performed by passing a hydrogen-containing gas such as hydrogen,
synthesis gas or a mixture of hydrogen with nitrogen, methane or other inert gas over the dried
catalyst composition at elevated temperature, for example by passing the hydrogen-containing
gas over the composition at temperatures in the range 150-600°C, preferably 250-600°C,
alternatively 150-500°C, preferably 300-500°C for between 1 and 24 hours. Reduction may be
performed at atmospheric or higher pressures up to about 25 bar.
Catalysts in the reduced state can be difficult to handle as they can react spontaneously with
oxygen in air, which can lead to undesirable self-heating and loss of activity. Consequently
reduced catalysts suitable for hydrogenation reactions may be passivated following reduction
with an oxygen-containing gas, often air or oxygen in carbon dioxide and/or nitrogen.
Passivation provides a thin protective layer sufficient to prevent undesirable reaction with air,
but which is readily removed once the catalyst has been installed in a hydrogenation process
by treatment with a hydrogen-containing gas. For catalysts suitable for Fischer-Tropsch
processes, passivation is not preferred and the reduced catalyst is preferably protected by
encapsulation of the reduced catalyst particles with a suitable barrier coating. In the case of a
Fischer-Tropsch catalyst, this may suitably be a FT-hydrocarbon wax. Alternatively, the
catalyst can be provided in the unreduced state and reduced in-situ with a hydrogen-containing
Whichever route is chosen, the catalysts of the present invention provide very high cobalt
surface areas. The catalysts, when reduced at 425°C, have a cobalt surface area of at least
30 m2/g of (reduced) catalyst as measured by the H2 chemisorption technique described
herein. Preferably the cobalt surface area is greater than 35 m2/g (reduced) catalyst, more
preferably at least 40 m2/g (reduced) catalyst.
The cobalt surface area is determined by H2 chemisorption. The preferred method is as
follows; approximately 0.2 to 0.5 g of sample material is firstly degassed and dried by heating
to 140°C at 10°C/min in flowing helium and holding it at 140°C for 60 mins. The degassed and
dried sample is then reduced by heating it from 140°C to 425°C at a rate of 3°C/min under a 50
ml/min flow of hydrogen and then holding it under the same hydrogen flow, at 425°C for 6
hours. Following reduction and under vacuum, the sample is heated up to 450°C at 10°C/min
and held under these conditions for 2 hours. The sample is then cooled to 150°C and held for
a further 30 minutes under vacuum. The chemisorption analysis is carried out at 150°C using
pure hydrogen gas. An automatic analysis program is used to measure a full isotherm over the
range 100 mmHg up to 760 mmHg pressure of hydrogen. The analysis is carried out twice; the
first measures the "total" hydrogen uptake (i.e. includes chemisorbed hydrogen and
physisorbed hydrogen) and immediately following the first analysis the sample is put under
vacuum ( uptake. A linear regression may then be applied to the "total" uptake data with extrapolation
back to zero pressure to calculate the volume of gas chemisorbed (V).
Cobalt surface areas were calculated in all cases using the following equation;
Co surface area = ( 6.023 x 1023 x V x SF x A ) / 22414
where V = uptake of H2 in ml/g
SF = Stoichiometry factor (assumed 2 for H2 chemisorption on Co)
A = area occupied by one atom of cobalt (assumed 0.0662 nm2)
This equation is described in the Operators Manual for the Micromeretics ASAP 2010 Chemi
System V 2.01, Appendix C, Part No. 201 -42808-01, October 1996.
The catalysts may be used for hydrogenation reactions and for the Fischer-Tropsch synthesis
Typical hydrogenation reactions include the hydrogenation of aldehydes and nitriles to alcohols
and amines respectively, and the hydrogenation of cyclic aromatic compounds or unsaturated
hydrocarbons. The catalysts of the present invention are particularly suitable for the
hydrogenation of unsaturated organic compounds particularly oils, fats, fatty acids and fatty
acid derivatives like nitriles. Such hydrogenation reactions are typically performed in a
continuous or batch-wise manner by treating the compound to be hydrogenated with a
hydrogen-containing gas under pressure in an autoclave at ambient or elevated temperature in
the presence of the cobalt-catalyst, for example the hydrogenation may be carried out with
hydrogen at 80-250°C and a pressure in the range 0.1- 5.0 x 106 Pa.
The Fischer-Tropsch synthesis of hydrocarbons 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 1.7-2.5:1. 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 150-350°C. The gas-hourly-space velocity (GHSV) for
continuous operation is in the range 100-25000hr"1. The catalysts of the present invention are
of particular utility because of their high cobalt surface areas/g catalyst.
The invention will now be further described by reference to the following examples.
Example 1. Preparation of catalysts
AI:Co molar ratio = 0.21:1. Aqueous solutions of Co(N03)2 hydrate (35 g Co/litre) and a
Na2CO3 anh. (67 g/litre)/NaOH (25 g/litre) mixture were continuously pumped at flow rates of
respectively 1500 and 860 ml/hour into a vigorously stirred precipitation reactor, where cobalt
hydroxide/carbonate was precipitated at a temperature of 35°C. The pH of the suspension in
this reactor was 9.5. In this precipitation reactor (volume 100ml), the suspension had an
average residence time of 0.5 min. The suspension was then transferred continuously to an
ageing reactor (volume 5000 ml) wherein the temperature was 70°C. Simultaneously, an
amount of aluminium ions was continuously dosed into this reactor, as an aqueous solution of
sodium aluminate (10 g Al/litre), at a rate of 490ml/hour. In addition, 1150 ml/hour of water was
dosed into this reactor. The suspension was subsequently transferred continuously to a
second ageing reactor in which the temperature was 60°C.
The pH of the suspension in the first ageing reactor was 9.5 and in the second ageing reactor
9.5. The volume of the liquid in the first and second ageing reactor was kept constant.
The ageing was continued until at least a major portion of the aluminium formed cobaltaluminium
compounds. The ageing step was terminated and the suspension from the second
ageing reactor filtered. The filtration rate was about 1-litre/min. The filter cake thus obtained
was washed with distilled water. The washed cake was spray dried. The cobalt surface area
was determined on the reduced catalyst by hydrogen chemisorption as described above. The
particle size of the catalyst prior to reduction was measured using a Malvern Mastersizer™'
The BET surface area and pore volume for the un-reduced and reduced catalysts were
measured by nitrogen physisorption using methods known in the art. The pore volume was
determined using the desorption branch and pore diameter was calculated from (4 x pore
volume)/BET surface area. The results are given in Table 1.
Comparative Example A
In accordance with the procedure described in Example 1, a catalyst was prepared using an
AI/Co atomic ratio of 0.02 by using a sodium aluminate solution of 1g Al/litre. The results are
An aqueous solutions of cobalt nitrate and an aqueous precipitant solution comprising NaOH/
and/or Na2CO3 were continuously pumped at flow rates of respectively 1500 and 860 ml/hour
into a vigorously stirred precipitation reactor (upto 1500rpm), where cobalt hydroxide/carbonate
was precipitated at a temperature of 20-45°C. In this precipitation reactor (volume ca.15ml),
the suspension had an average residence time of ca. 0.5 min. The suspension was then
transferred continuously to a stirred ageing reactor (volume 5000 ml, stirred 100-450rpm),
which allowed an ageing time of 75 to 25 minutes. (Alternatively a 3000 ml vessel was used in
some experiments). The temperature of the ageing reactor was controlled by means of a
thermostatically-controlled water bath. Simultaneously, an amount of aluminium ions was
continuously dosed into this reactor, as an aqueous solution of sodium aluminate. The
suspension was subsequently transferred continuously to a non-stirred storage tank at room
temperature (ca 20°C). The suspension from the storage tank was subsequently washed with
1500 ml of demineralised water and filtered. The filter cake thus obtained was dried, at 110°C
overnight or by spray drying. The cobalt surface area was determined on the reduced catalyst
by hydrogen chemisorption as described above.
a) Effect of pH. In a first series of experiments the pH in the ageing reactor was varied by
using different amounts of sodium carbonate and sodium hydroxide in the precipitating
agent solution, at an AI:Co ratio of 0.3 with 70°C ageing for 70 minutes. (0.0 indicates that
all the precipitant was sodium carbonate and 1.0 indicates that the precipitant was 50:50
(molar) sodium hydroxide and sodium carbonate. The results are as follows;(Table Removed)
1. A process for the Fischer-Tropsch synthesis of hydrocarbons comprising the step of
reacting a mixture of carbon monoxide and hydrogen in the presence of a particulate
catalyst comprising an intimate mixture of cobalt and aluminium compounds having cobalt
and aluminium at an atomic ratio in the range 10:1 to 2:1 (Co:AI), which when reduced at
425°C, has a cobalt surface area as measured by hydrogen chemisorption at 150°C of at
least 30 m2/g of catalyst wherein the catalyst is prepared by steps comprising;
(i) precipitating an insoluble cobalt compound from an aqueous solution of a cobalt
salt with an excess alkaline precipitating agent,
(ii) adding a soluble aluminium compound,
(iii) ageing the resulting precipitate in suspended form,
(iv) recovering and drying the catalyst composition, and
(v) activating the catalyst by reduction using a hydrogen-containing gas.
2. A process according to claim 1 further comprising a step of calcination of the dried catalyst
3. A process according to claim 1 or claim 2 wherein the cobalt salt is a nitrate, sulphate,
acetate, chloride or formate.
4. A process according to any one of claims 1 to 3 wherein the cobalt salt is cobalt nitrate.
5. A process according to any one of claims 1 to 4 wherein the precipitating agent is an alkali
metal hydroxide, alkali metal carbonate, alkali metal bicarbonate, the corresponding
ammonium compound or a mixture thereof.
6. A process according to any one of claims 1 to 5 wherein the precipitating agent is sodium
hydroxide, sodium carbonate or a mixture thereof.
7. A process according to any one of claims 1 to 6 wherein the precipitation is effected at a
pH in the range 7-10 at a temperature below 50°C.
8. A process according to any one of claims 1 to 7 wherein the soluble aluminium compound
is aluminium nitrate, sodium aluminate or alumina that dissolves at least partly in the
9. A process according to any one of claims 1 to 8 wherein the soluble aluminium compound
is sodium aluminate.
10. A process according to any one of claims 1 to 9 wherein ageing is performed until 50% of
the aluminium is in the form of cobalt aluminium compounds.
11. A process according to any one of claims 1 to 10 wherein the ageing is performed at a pH
in the range of 6-11 at a temperature in the range 10-100°C.
12. A process according to any one of claims 1 to 11 wherein the mixture of carbon monoxide
and hydrogen used for the Fischer-Tropsch synthesis of hydrocarbons is a synthesis gas
having a hydrogen: carbon monoxide ratio in the range 1.7-2.5:1.
13. A process according to any one of claims 1 to 12 wherein the Fischer-Tropsch synthesis of
hydrocarbons is performed in a continuous or batch process using one or more stirred
slurry-phase reactors, bubble-column reactors, loop reactors orfluidised bed reactors.
14. A process according to any one of claims 1 to 13 wherein the Fischer-Tropsch synthesis of
hydrocarbons is operated at pressures in the range 0.1-10Mpa and temperatures in the
|Indian Patent Application Number||1467/DELNP/2007|
|PG Journal Number||33/2013|
|Date of Filing||23-Feb-2007|
|Name of Patentee||JOHNSON MATTHEY PLC.,|
|Applicant Address||40-42 HATTON GARDEN LONDON EC1N 8EE,UK|
|PCT International Classification Number||B01J 23/75|
|PCT International Application Number||PCT/GB2005/003235|
|PCT International Filing date||2005-08-19|