WO2008003731A1

WO2008003731A1 - Process for preparing a catalyst

Info

Publication number: WO2008003731A1
Application number: PCT/EP2007/056783
Authority: WO
Inventors: Arend Hoek; Patrick Vander Hoogerstraete; Carolus Matthias Anna Maria Mesters; Marinus Johannes Reynhout; Guy Lode Magda Maria Verbist
Original assignee: Shell Internationale Research Maatschappij B.V.
Priority date: 2006-07-07
Filing date: 2007-07-05
Publication date: 2008-01-10

Abstract

A process for the preparation of a catalyst or catalyst precursor for use in a reactor, comprising the steps of: (a) admixing: (i) a catalytically active component or precursor therefor; (ii) one or more carrier materials; (iii) particles of fresh, optionally calcined, catalyst or catalyst precursor material, said particles having a size of 1 to 100 micrometer; and (iv) optionally one or more promoters and/or one or more co-catalysts; (b) shaping the mixture of step (a), and (c) calcining the shaped product of step (b). The introduction of micro-particles into the catalyst or catalyst precursor provides a number of advantages including increased activity, strength, and possible uses of waste material.

Description

PROCESS FOR PREPARING A CATALYST

The present invention relates to a process for preparing a catalyst and a catalyst precursor for use in producing normally gaseous, normally liquid and optionally solid hydrocarbons from synthesis gas, generally provided from a hydrocarbonaceous feed, for example a Fischer-Tropsch process.

Many documents are known describing processes for the catalytic conversion of (gaseous) hydrocarbonaceous feedstocks, especially methane, natural gas and/or associated gas, into liquid products, especially methanol and liquid hydrocarbons, particularly paraffinic hydrocarbons. In this respect often reference is made to remote locations and/or off-shore locations, where direct use of the gas, e.g. through a pipeline or in the form of liquefied natural gas, is not always practical. This holds even more in the case of relatively small gas production rates and/or fields. Reinjection of gas will add to the costs of oil production, and may, in the case of associated gas, result in undesired effects on the crude oil production. Burning of associated gas has become an undesired option in view of depletion of hydrocarbon sources and air pollution.

The Fischer-Tropsch process can be used as part of the conversion of hydrocarbonaceous feed stocks into liquid and/or solid hydrocarbons. Generally the feed stock (e.g. natural gas, associates gas and/or coal-bed methane, coal) is converted in a first step into a mixture of hydrogen and carbon monoxide (this mixture is often referred to as synthesis gas or syngas) . The synthesis gas is then fed into a reactor where it is converted in one or more steps over a suitable catalyst at elevated temperature and pressure into compounds ranging from methane to high molecular weight modules comprising up to 200 carbon atoms, or, under particular circumstances, even more, (and water) .

Catalysts used in the Fischer-Tropsch synthesis often comprise a carrier based support material and one or more metals from Group VIII of the Periodic Table, especially from the cobalt and iron groups, optionally in combination with one or more metal oxides and/or metals as promoters selected from zirconium, titanium, chromium, vanadium and manganese, especially manganese. Such catalysts are known in the art and have been described for example, in the specifications of WO 9700231A and US 4595703.

Catalysts can be prepared by obtaining a metal hydroxide, carefully oxidising it to the metal oxide and then placing it in the appropriate reactor where it is reduced to the metal in situ. One catalyst for Fischer-Tropsch reactions is cobalt in titania. In one way to prepare the catalyst, cobalt hydroxide (Co (OH) 2) can be used as a starting material.

This material is usually mixed with one or more co- catalysts, promoters, etc, and a carrier, and then calcined. During calcination cobalt oxide (CoO) is formed, and next the cobalt is further oxidised to form C03O4. The calcined catalyst or catalyst precursor normally is placed in a Fischer-Tropsch reactor. In the reactor the cobalt oxide is reduced to cobalt. One limiting factor of the activity of a catalyst is its porosity, that is the ability of the syngas to ingress into the catalyst particles so as to fully utilise all the catalytically active material. It is one object of the present invention to provide an improved catalyst and catalyst precursor.

According to one aspect of the present invention, there is provided a process for the preparation of a catalyst or catalyst precursor for use in a reactor, comprising the steps of:

(a) admixing:

(i) a catalytically active component or precursor therefor; (ϋ) one or more carrier materials;

(iii) particles of fresh, optionally calcined, catalyst or catalyst precursor material, said particles having a size of 1 to 100 micrometer; and

(iv) optionally one or more promoters and/or one or more co-catalysts;

(b) shaping the mixture of step (a), and

(c) calcining the shaped product of step (b) .

The introduction of micrometer-sized particles of fresh, optionally calcined, catalyst or catalyst precursor material into the catalyst or catalyst precursor provides a number of advantages including increased activity and increased strength. Preferably the micrometer-sized particles are calcined particles. Particles with a size of 1 to 100 micrometer are defined as particles having a longest internal straight length of 1 to 100 micrometer.

Catalyst or catalyst precursor material comprises a catalytically active component or precursor therefore, one or more carrier materials, and optionally other components. As examples of optional other components are promoters and co-catalysts. Fresh catalyst or catalyst precursor material is fresh in the sense that the material has not been subjected to a mixture of hydrogen and carbon monoxide. Spent catalyst, on the other hand, has been subjected to a mixture of hydrogen and carbon monoxide and has less than 70% of its original activity.

The particles of fresh, optionally calcined, catalyst or catalyst precursor material may be formed during the production of a catalyst or catalyst precursor. For example they may be derived from catalyst or catalyst precursor which is considered to have insufficient or incorrect activity for the intended reaction to be carried out in the reactor. Such material could be calcined, and recycled for use in the present invention, rather than being considered as waste material that may otherwise be dumped or stockpiled elsewhere. It may be necessary to grind or mill such material to a size of 1 to 100 micrometer before using it in a process according to the present invention. Another example of the formation of suitable particles of fresh, optionally calcined, catalyst or catalyst precursor material are the 'fines' that are created in a process for forming a catalyst or catalyst precursor, including but not limited to the process of the present invention. That is, in many catalyst forming processes, the catalyst or catalyst precursor undergoes physical processing such as tumbling in a dryer, or conveying through a drum, or other transportation, which action forms fine particles by the physical inter-engagement of the catalyst or catalyst precursor particles against themselves or against a surface of the process machinery. Where such fines have, or can be graded to, the desired micro-particle size as mentioned above, then such materials can be recycled back into the process for forming the catalyst or catalyst precursor, rather than again being considered as waste. The micrometer-sized particles of fresh, optionally calcined, catalyst or catalyst precursor material generally have a size wholly or substantially in the range of 1 to 100 μm, preferably 2 to 50 μm, more preferably 5 to 20 μm. The size of the micro-particles can be compared with the nanometer size of the other components in the mixture of step (a) . The other components normally have a size smaller than 1 micrometer, preferably smaller than 800 nm, more preferably smaller than 500 nm, or even smaller than 200 nm.

Preferably the micrometer-sized particles of fresh, optionally calcined, catalyst or catalyst precursor material will occupy 1 to 20%, possibly about 10%, or even less than 10%, for example 3-7%, of the volume of solids in the admixture of step (a) . Preferably the micrometer-sized particles of fresh, optionally calcined, catalyst or catalyst precursor material will occupy 1 to 20%, preferably 5-10% of the weight of the catalyst or catalyst precursor after the calcination step (c).

In this way, the present invention provides a catalyst and catalyst precursor, which includes a significant portion of particles which are significantly larger than the sizes of other components. Other components are, optionally among others, the catalytically active component (s) or precursors therefor, carrier material (s), and any promoters and/or co- catalysts if present.

The micro-particles and other components of the catalyst or catalyst precursor may be wholly or substantially simultaneously admixed, or admixed by addition of each component over time. The mixture is then shaped, for example by extrusion or pelletising, granulating, spray-drying, or hot oil dropping methods. Preferably the mixture is extruded or pelletised, most preferably extruded. Apart from the micrometer-sized particles of fresh, optionally calcined, catalyst or catalyst precursor material other particles having a size in the range of 1 to 100 μm, preferably 2 to 50 μm, more preferably 5 to 20 μm may be admixed in step (a) . Preferably such extra micrometer-sized particles are of a material that can be defined as 'inert' to the reaction being catalysed and/or the catalytic activity of the catalytically active component, more preferably 'inert' in not affecting the catalytic activity of the catalytically active component, most preferably not causing any catalyst de-activation.

For example, the extra micro-particles may be a relatively non-active material such as a refractory oxide such as silica, alumina or titania, including crystalline forms such as quartz and quartzite. It is preferred not to use zeolite particles.

Preferably, particles of fresh, optionally calcined, catalyst or catalyst precursor material, and/or any extra micro-particles, have a hardness of at least 5.5 on the Mohs hardness scale. Preferably, they have a hardness between 5.5 and 9 on the Mohs hardness scale, more preferably between 6 and 9 on the Mohs hardness scale.

The particles of fresh, optionally calcined, catalyst or catalyst precursor material, and any extra micro- particles (if present), may have a regular or non-regular shape. Particles having a shape significantly different from a sphere, such as needles, platelets or particles containing sharp edges, are included within the present invention . Through the use of micro-particles, it has been found that the present invention provides a catalyst or catalyst precursor which has an increased porosity compared with prior catalysts and catalyst precursors not containing micro-particles. It is believed this has been achieved through two causes. Firstly, the introduction of larger particles can provide strength to the catalyst or catalyst precursor particles, thus reducing the compaction energy required to shape the mixture of step (a) in step (b) . With less compaction, there is increased porosity in general.

Secondly, the inclusion of micro-particles reduces the contact of at least some or portions of the other components together, increasing the degree of porosity between the components in the shaped catalyst or catalyst precursor particles.

It has now been found that, even when the amount of catalytically active component or precursor therefor in a catalyst particle formed by the present invention compared to a similar prior art particle is reduced as a result of the introduction of the micro-particles, the catalytic activity of the catalyst formed by the present invention is higher due to the increase in porosity, and hence increase of ingress of reactants into the catalyst particles.

The introduction of micro-particles provides a catalyst or catalyst precursor which has increased strength, especially when the micro-particles have a hardness of at least 5.5 on the Mohs hardness scale, and hence provide strength on a micro-reinforcement scale.

Since particles of fresh, optionally calcined, catalyst or catalyst precursor material are used to prepare a catalyst or catalyst precursor, and are not considered 'waste', the present invention has a natural economic benefit.

The porosity of the catalyst or catalyst precursor prepared using a method according to the present invention can be measured using any known porosity apparatus or test. A further test can be to measure the rate of absorption, which is a more refined measurement of the degree of porosity of the catalyst particles rather than the overall amount or volume of porosity. The rate of absorption can be measured by locating such particles in a resin which has an initially low viscosity, but whose viscosity increases over time until it sets. Various resin materials are known having this utility, such as those used for analysis for certain samples by micro-spectroscopy, including SEM. The particles can be located in such a resin for different time periods, and as the resin solidifies, micrographs can be taken of cross sections of the particles to see the amount of ingress of the resin material into the particles over time. Thus, the micrographs provide a visual indication of the rate of absorption.

Preferably more than 50% of the total pore volume of the micrometer-sized particles of fresh, optionally calcined, catalyst or catalyst precursor material admixed in step (a) has pores with a size of more than 2 nm. More preferably the average pore size of more than 50% of the total pore volume of the micrometer-sized particles of fresh, optionally calcined, catalyst or catalyst precursor material admixed in step (a) is more than 2 nm. The mixture of step (a) may include a gluing agent.

Such gluing agent is preferably a carboxylic acid, being either a mono-carboxylic, di-carboxylic or tri—carboxylic acid. Carboxylic acid derivatives may also be used. Optionally, other functional groups may be present in the carbon chains, such as aldehyde groups. Poly-carboxylic acids may also be used.

The gluing agent also includes basic and acidic compounds. Examples of suitable compounds include

L-Aspartic acid, acetic acid, formic acid, citric acid, oxalic acid and propionic acid, preferably citric acid.

The gluing agent may be provided in any amount suitable, which can be calculated by the skilled men for different carrier materials and additional components. In one embodiment, the amount of gluing agent added is at least 0.25wt% of the mixture or greater. The amount of gluing agent is one influence the strength of the catalyst or catalyst precursor, which can be confirmed by tests such as analysing attrition, and flat plate crushing strength.

General methods of preparing catalysts are known in the art, see for example US 4409131, US 5783607, US 5502019, WO 0176734, CA 1166655, US 5863856 and US 5783604. These include preparation by co-precipitation and impregnation. Such processes could also include freezing, sudden temperature changing, etc. Control of the component ratio in the solid solution can be provided by parameters such as residence time, temperature control, concentration of each component, etc.

The catalytically active component for Fischer- Tropsch preferably is a catalytically active metal, or a mixture of catalytically active metals, such as cobalt, iron, ruthenium, or a mixture thereof, preferably cobalt. The catalytically active component may be present with one or more metals or metal oxides as promoters, more particularly one or more d-metals or d-metal oxides. Suitable metal oxide promoters may be selected from Groups UA, IUB, IVB, VB, VIB, VIIB and VIIIB of the Periodic Table of Elements, or the actinides and lanthanides. In particular, oxides of magnesium, calcium, strontium, barium, scandium, yttrium, lanthanum, cerium, titanium, zirconium, hafnium, thorium, uranium, vanadium, chromium and manganese are most suitable promoters.

References to "Groups" and the Periodic Table as used herein relate to the previous IUPAC version of the Periodic Table of Elements such as that described in the 68th Edition of the Handbook of Chemistry and Physics (CPC Press) .

Suitable metal promoters may be selected from Groups VIIB or VIII of the (same) Periodic Table. Manganese, iron, rhenium and Group VIII noble metals are particularly suitable, with platinum and palladium being especially preferred. The amount of promoter present in the catalyst is suitably in the range of from 0.01 to 100 pbw, preferably 0.1 to 40, more preferably 1 to 20 pbw, per 100 pbw of carrier.

The catalytically active component could also be present with one or more co-catalysts. Suitable co- catalysts include one or more metals such as iron, nickel, or one or more noble metals from Group VIII. Preferred noble metals are platinum, palladium, rhodium, ruthenium, iridium and osmium. Most preferred co- catalysts for use in the hydro-cracking are those comprising platinum. Such co-catalysts are usually present in small amounts. A most suitable catalyst comprises cobalt as the catalytically active component and zirconium as a promoter. Another most suitable catalyst comprises cobalt - li ¬

as the catalytically active component and manganese and/or vanadium as a promoter.

Any promoter (s) are typically present in an amount of from 0.1 to 60 parts by weight per 100 parts by weight of any carrier material used. It will however be appreciated that the optimum amount of promoter (s) may vary for the respective elements which act as promoter (s). If the catalyst comprises cobalt as the catalytically active metal and manganese and/or vanadium as promoter, the cobalt: (manganese + vanadium) atomic ratio is advantageously at least between 5:1 and 30:1.

In one embodiment of the present invention, the catalyst comprises the promoter (s) and/or co-catalyst ( s ) having a concentration in the Group VIII metal (s) in the range 1-10 atom% (based on cobalt), preferably 3-7 atom%, and more preferably 4-6 atom% .

In another embodiment of the present invention, the catalytically active component or precursor therefor is a catalytically active metal or precursor therefor in the form of a hydroxide, carbonate, citrate, nitrate, oxyhydroxide or oxide, preferably hydroxide.

The catalytically active component is preferably supported on a carrier material, which can be added prior to forming or shaping. The porous carrier material may be selected from any of the suitable refractory metal oxides or silicates or combinations thereof known in the art. Particular examples of preferred porous carriers include silica, alumina, titania, zirconia, ceria, gallia and mixtures thereof, especially silica, zirconia and titania.

The optimum amount of catalytically active component present on a carrier depends inter alia on the specific catalytically active component. Typically, the amount of cobalt present in the catalyst may range from 1 to 100 parts by weight per 100 parts by weight of carrier material, preferably from 10 to 50 parts by weight per 100 parts by weight of carrier material. In a preferred embodiment, a liquid is added to the mixture as part of the process of the present invention. Preferably the liquid is added to the mixture after admixing and before or during the shaping such as extrusion . The liquid may be any of suitable liquids known in the art, for example: water; ammonia, alcohols, such as methanol, ethanol and propanol; ketones, such as acetone; aldehydes, such as propanol and aromatic solvents, such as toluene, and mixtures of the aforesaid liquids. A most convenient and preferred liquid is water.

The liquid may include viscosity improvers such as polyvinylalcohol .

WO99/34917A describes a process for forming a catalyst or catalyst precursor suitable for use with the present invention. WO99/34917A describes a process for the preparation of a cobalt-containing catalyst or catalyst precursor, comprising: mixing (1) titania or a titania precursor, (2) a liquid, and (3) a cobalt compound, which is at least partially insoluble in the amount of liquid used, to form a mixture; shaping and drying of the mixture thus obtained; and calcination of the composition thus obtained.

The titania for inclusion in the mixture may further comprise up to 20% by weight of another refractory oxide, typically silica, alumina or zirconia, or a clay as a binder material, preferably up to 10% by weight based on the total weight of refractory oxide and binder material. Preferably, the titania has been prepared in the absence of sulphur-containing compounds . An example of such preparation method involves flame hydrolysis of titanium tetrachloride. Titania is available commercially and is well-known as material for use in the preparation of catalysts or catalyst precursors. The titania suitably has a surface area of from 0.5 to 200 m²/g, more preferably of from 20 to 150 m^/g.

As an alternative or in addition to titania, the mixture may comprise a titania precursor. Titania may be prepared by heating titania hydroxide. As the heating progresses, titania hydroxide is converted via a number of intermediate forms and the successive loss of a number of water molecules into titania. For the purpose of this specification, the term "titania precursor" is to be taken as a reference to titania hydroxide or any of the aforementioned intermediate forms .

The liquid may be any of suitable liquids known in the art as described above. Any cobalt compound, preferably of which at least 50% by weight is insoluble in the amount of the liquid used, can be suitably used in the process of the present invention. Preferably, at least 70% by weight of the cobalt compound is insoluble in the amount of liquid used, more preferably at least 80% by weight, still more preferably at least 90% by weight. Examples of suitable cobalt compounds are metallic cobalt powder, cobalt hydroxide, cobalt oxide or mixtures thereof, preferred cobalt compounds are Co (OH) 2 or C03O4.

The amount of cobalt compound present in the mixture may vary widely. Typically, the mixture comprises up to 60 parts by weight of cobalt per 100 parts by weight of refractory oxide, preferably 10-40 parts by weight. The above amounts of cobalt refer to the total amount of cobalt, on the basis of cobalt metal, and can be determined by known elemental analysis techniques.

The cobalt compound which is at least partially insoluble in the liquid may be obtained by precipitation. Any precipitation method known in the art may be used. Preferably, the cobalt compound is precipitated by addition of a base or a base-releasing compound to a solution of a soluble cobalt compound, for example by the addition of sodium hydroxide, potassium hydroxide, ammonia, urea, or ammonium carbonate. Any suitable soluble cobalt compound may be used, preferably cobalt nitrate, cobalt sulphate or cobalt acetate, more preferably cobalt nitrate. Alternatively, the cobalt compound may be precipitated by the addition of an acid or an acid-releasing compound to a cobalt ammonia complex. The precipitated cobalt compound may be separated from the solution, washed, dried, and, optionally, calcined. Suitable separation, washing, drying and calcining methods are commonly known in the art.

In one embodiment of the process of the present invention, the cobalt compound and a compound of promoter metal are obtained by co-precipitation, most preferably by co-precipitation at constant pH. Co-precipitation at constant pH may be performed by the controlled addition of a base, a base-releasing compound, an acid or an acid- releasing compound to a solution comprising a soluble cobalt compound and a soluble compound of promoter metal, preferably by the controlled addition of ammonia to an acidic solution of a cobalt compound and a promoter metal compound .

The cobalt compound and, optionally, the promoter metal compound may be precipitated in the presence of at least a part of the titania or titania precursor, preferably in the presence of all titania or titania precursor. In a preferred embodiment of the invention, cobalt hydroxide and manganese hydroxide are co-pre- cipitated by addition of ammonia to a solution comprising cobalt nitrate, manganese nitrate, and titania particles. The precipitated cobalt hydroxide and manganese hydroxide and the titania particles may be separated from the solution, washed, dried, and, optionally, calcined by methods commonly known in the art.

The solids content of the mixture formed in step (a) of the preparation process of the invention may be up to 90% by weight based on the total mixture. It will be appreciated that the mixing method largely depends on the solids contents of the mixture.

The mixing of step (a) of the catalyst preparation process of the present invention may suitably be performed by methods known to those skilled in the art, such as by kneading, mulling or stirring. Typically, the ingredients of the mixture are mulled for a period of from 5 to 120 minutes, preferably from 15 to 90 minutes. During the mulling process, energy is put into the mixture by the mulling apparatus. The mulling process may be carried out over a broad range of temperature, preferably from 15 to 90 ⁰C. As a result of the energy input into the mixture during the mulling process, there will be a rise in temperature of the mixture during mulling. The mulling process is conveniently carried out at ambient pressure. Any suitable, commercially available mulling machine may be employed .

To improve the flow properties of the mixture, it is preferred to include one or more flow improving agents and/or extrusion aids in the mixture prior to extrusion. Suitable additives for inclusion in the mixture include fatty amines, quaternary ammonium compounds, polyvinyl pyridine, sulphoxonium, sulphonium, phosphonium and iodonium compounds, alkylated aromatic compounds, acyclic mono-carboxylic acids, fatty acids, sulphonated aromatic compounds, alcohol sulphates, ether alcohol sulphates, sulphated fats and oils, phosphonic acid salts, polyoxyethylene alkylphenols, polyoxyethylene alcohols, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyacrylamides, polyols and acetylenic glycols. Preferred additives are sold under the trademarks Nalco and Superfloc.

To obtain strong extrudates, it is preferred to include in the mixture, prior to shaping, for example by extrusion, at least one compound which acts as a peptising agent for the titania. Suitable peptising agents for inclusion in the extrudable mixture are well known in the art and include basic and acidic compounds. Examples of basic compounds are ammonia, ammonia- releasing compounds, ammonium compounds or organic amines. Such basic compounds are removed upon calcination and are not retained in the extrudates to impair the catalytic performance of the final product. Preferred basic compounds are organic amines or ammonium compounds. A most suitable organic amine is ethanol amine. Suitable acidic peptising agents include weak acids, for example formic acid, acetic acid, citric acid, oxalic acid, and propionic acid. Optionally, burn-out materials may be included in the mixture, prior to extrusion, in order to create macropores in the resulting extrudates . Suitable burn-out materials are commonly known in the art. The total amount of flow-improving agents/extrusion aids, peptising agents, and burn-out materials in the mixture preferably is in the range of from 0.1 to 20% by weight, more preferably from 0.5 to 10% by weight, on the basis of the total weight of the mixture.

Extrusion may be effected using any conventional, commercially available extruder. In particular, a screw- type extruding machine may be used to force the mixture through the orifices in a suitable dieplate to yield extrudates of the desired form. The strands formed upon extrusion may be cut to the desired length.

After shaping in step(b), the shaped product, for example extrudates, are dried. Drying may be effected at an elevated temperature, preferably up to 500 ⁰C, more preferably up to 300 ⁰C. The period for drying is typically up to 5 hours, more preferably from 15 minutes to 3 hours .

In another embodiment of the invention, the solids contents of the mixture obtained in step (a) is such that a slurry or suspension is obtained, and the slurry or suspension thus-obtained is shaped and dried by spray- drying. The solids content of the slurry/suspension is typically in the range of from 1 to 30% by weight, preferably of from 5 to 20% by weight. The extruded and dried, spray-dried or otherwise- shaped and dried compositions are subsequently calcined. Calcination is effected at elevated temperature, preferably at a temperature between 400 and 750 ⁰C, more preferably between 500 and 650 ⁰C. The duration of the calcination treatment is typically from 5 minutes to several hours, preferably from 15 minutes to 4 hours. Suitably, the calcination treatment is carried out in an oxygen-containing atmosphere, preferably air. It will be appreciated that, optionally, the drying step and the calcining step can be combined.

The resulting catalyst or catalyst precursor may be activated by contacting the catalyst with hydrogen or a hydrogen-containing gas, typically at temperatures of about 200 to 350 ⁰C.

The present invention extends to the activation of a catalyst or catalyst precursor prepared as herein described, particularly but not exclusively, by decomposition of the catalytically active component or precursor therefor and/or reduction of the catalytically active component or precursor therefor to its metal form. The invention also extends to a catalyst formed thereby. A catalyst provided by the present invention is particularly, but not exclusively, useful for a hydrocarbon synthesis process such as a Fischer-Tropsch reaction. Fischer-Tropsch catalysts are known in the art, and as a Group VIII metal component, they preferably use cobalt, iron and/or ruthenium, more preferably cobalt. A steady state catalytic hydrocarbon synthesis process may be performed under conventional synthesis conditions known in the art. Typically, the catalytic conversion may be effected at a temperature in the range of from 100 to 600 ⁰C, preferably from 150 to 350 ⁰C, more preferably from 180 to 270 ⁰C. Typical total pressures for the catalytic conversion process are in the range of from 1 to 200 bar absolute, more preferably from 10 to 70 bar absolute. In the catalytic conversion process mainly C5 + hydrocarbons are formed, based on the total weight of hydrocarbonaceous products formed, (at least 70 wt%, preferably 90 wt%) .

According to a second aspect of the present invention, there is provided a process for producing normally gaseous, normally liquid and optionally normally solid hydrocarbons from synthesis gas which comprises the steps of :

(i) providing the synthesis gas; and (ii) catalytically converting the synthesis gas of step (i) at an elevated temperature and pressure to obtain the normally gaseous, normally liquid and optionally normally solid hydrocarbons; wherein the catalyst for step (ii) is formed from a catalyst or catalyst precursor herein described.

The present invention also provides a process further comprising:

(iii) catalytically hydrocracking higher boiling range paraffinic hydrocarbons produced in step(ii), as well as hydrocarbons whenever provided by a process as described herein.

The present invention also provides use of a catalyst as defined herein in a process for producing normally gaseous, normally liquid and optionally normally solid hydrocarbons from synthesis gas which comprises the steps of:

(i) providing the synthesis gas; and

(ii) catalytically converting the synthesis gas of step (i) at an elevated temperature and pressure to obtain the normally gaseous, normally liquid and optionally normally solid hydrocarbons .

Fischer-Tropsch synthesis is preferably carried out at a temperature in the range from 125 to 350 ⁰C, more preferably 175 to 275 ⁰C, most preferably 180 ⁰C to 260 ⁰C. The pressure preferably ranges from 5 to

150 bar abs . , more preferably from 5 to 80 bar abs .

Preferably, a Fischer-Tropsch catalyst is used, which yields substantial quantities of paraffins, more preferably substantially unbranched paraffins. A part may boil above the boiling point range of the so-called middle distillates, to normally solid hydrocarbons. A most suitable catalyst for this purpose is a cobalt- containing Fischer-Tropsch catalyst. The term "middle distillates", as used herein, is a reference to hydrocarbon mixtures of which the boiling point range corresponds substantially to that of kerosene and gas oil fractions obtained in a conventional atmospheric distillation of crude mineral oil. The boiling point range of middle distillates generally lies within the range of about 150 to about 360 ⁰C.

The higher boiling range paraffinic hydrocarbons if present, may be isolated and subjected to a catalytic hydrocracking step, which is known per se in the art, to yield the desired middle distillates. The catalytic hydrocracking is carried out by contacting the paraffinic hydrocarbons at elevated temperature and pressure and in the presence of hydrogen with a catalyst containing one or more metals having hydrogenation activity, and supported on a carrier. Suitable hydrocracking catalysts include catalysts comprising metals selected from Groups VIB and VIII of the (same) Periodic Table of Elements. Preferably, the hydrocracking catalysts contain one or more noble metals from Group VIII. Preferred noble metals are platinum, palladium, rhodium, ruthenium, iridium, and osmium. Most preferred catalysts for use in the hydrocracking stage are those comprising platinum.

Suitable hydrocracking catalysts may be prepared according to the method of the present invention.

The amount of catalytically active component present in the hydrocracking catalyst may vary within wide limits and is typically in the range of from about 0.05 to about 5 parts by weight per 100 parts by weight of the carrier material. Suitable conditions for the catalytic hydrocracking are known in the art. Typically, the hydrocracking is effected at a temperature in the range of from about 175 to 400⁰C. Typical hydrogen partial pressures applied in the hydrocracking process are in the range of from 10 to 250 bar.

The process may be operated in a single pass mode ("once through") or in a recycle mode. Slurry bed reactors, ebulliating bed reactors and fixed bed reactors may be used, the fixed bed reactor being the preferred option .

The product of the hydrocarbon synthesis and consequent hydrocracking suitably comprises mainly normally liquid hydrocarbons, beside water and normally gaseous hydrocarbons. By selecting the catalyst and the process conditions in such a way that especially normally liquid hydrocarbons are obtained, the product obtained ("syncrude") may transported in the liquid form or be mixed with any stream of crude oil without creating any problems as to solidification and or crystallization of the mixture. It is observed in this respect that the production of heavy hydrocarbons, comprising large amounts of solid wax, are less suitable for mixing with crude oil while transport in the liquid form has to be done at elevated temperatures, which is less desired.

The off gas of the hydrocarbon synthesis may comprise normally gaseous hydrocarbons produced in the synthesis process, nitrogen, unconverted methane and other feedstock hydrocarbons, unconverted carbon monoxide, carbon dioxide, hydrogen and water. The normally gaseous hydrocarbons are suitably C]__5 hydrocarbons, preferably

C]__4 hydrocarbons, more preferably C]__3 hydrocarbons. These hydrocarbons, or mixtures thereof, are gaseous at temperatures of 5-30 ⁰C (1 bar), especially at 20 ⁰C (1 bar). Further, oxygenated compounds, e.g. methanol, dimethyl ether, may be present in the off gas. The off gas may be utilized for the production of electrical power, in an expanding/combustion process such as in a gas turbine described herein, or recycled to the process. The energy generated in the process may be used for own use or for export to local customers. Part of an energy could be used for the compression of the oxygen containing gas .

The process as just described may be combined with all possible embodiments as described in this specification . Any percentage mentioned in this description is calculated on total weight or volume of the composition, unless indicated differently. When not mentioned, percentages are considered to be weight percentages. Pressures are indicated in bar absolute, unless indicated differently.

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

A mixture was prepared containing 143 g commercially available titania powder (P25 ex. Degussa) , 66 g commercially available Co (OH) 2 powder, 10.3 g Mn(Ac)2-4H2θ and 38 g water. The mixture was kneaded for

15 minutes. The mixture was shaped using a Bonnot extruder. The extrudates were dried for 16 hours at 120 ⁰C and calcined for 2 hours at 500 ⁰C. The resulting extrudates contained 20 wt% Co and 1 wt% Mn. Example 1

A sample part of the Comparative Example above was ground and sieved to obtain microparticles in the range 5 to 50 μm. As such, the microparticles were calcined 'fines' created in the process for forming a catalyst or catalyst precursor. These microparticle 'fines' were added to the same ingredients as the Comparative Example above prior to kneading. After the same kneading, extruding, drying and calcinations steps of the Comparative Example, a calcined catalyst or catalyst precursor containing 5.5 wt% of microparticles of total weight was prepared.

The catalysts or catalyst precursors of the Comparative Example and Example 1 were reduced with hydrogen using the process described in Example VII of WO99/034917A.

The two catalysts were then contacted with a stream of synthesis gas. Catalyst testing was done at about 210 ⁰C, at a pressure of 35 bara, an H2/CO feed ratio of 1.1 and a GHSV of 1200 Nl/1 reactor volume/h. The Example 1 catalyst containing the fines showed an increased C5+ selectivity of about 1% (conversion of CO into C5+ hydrocarbons). In addition, the space time yield

(STY) showed an increase of about 7%. Similar results were obtained at a reaction temperature of about 200 ⁰C and of about 230 ⁰C (and a GHSV of 2400 Nl/L/h) .

Examples 2 and 3

Following the procedure in Example 1, a catalyst or catalyst precursor was prepared from the same components but with different amounts of microparticle fines, such that two further catalysts or catalyst precursors were prepared having 5 wt% and 10 wt% of the same microparticle 'fines' as Example 1. Following their reduction with hydrogen at about 260 ⁰C, Examples 2 and 3 catalysts were similarly contacted with a stream of synthesis gas. At a reaction temperature of 212/213 ⁰C, a pressure of 32 bara, a GHSV of 1200 Nl/L/h, and an H₂/C0 feed ratio of 1.1. Examples

2 and 3 showed an increased C5+ selectivity of about 3.5% and 2.5% respectively, and an increase in STY of about 19% and 13% respectively over a similar catalyst prepared without fines, and under the same reaction conditions. Using similar reaction conditions, but at a pressure of 57 bara and a reaction temperature of 207/208 ⁰C, there was an increase in C5+ selectivity of 2.5% and 1.3% respectively, and an 11% and 6.5% STY increase, using Examples 2 and 3 compared with the comparative catalyst.

Claims

C L A I M S

1. A process for the preparation of a catalyst or catalyst precursor for use in a reactor, comprising the steps of :

(a) admixing: (i) a catalytically active component or precursor therefor;

(ii) one or more carrier materials;

(iv) optionally one or more promoters and/or one or more co-catalysts ;

(b) shaping the mixture of step (a), and

(c) calcining the shaped product of step (b) .

2. A process as claimed in claim 1, wherein a Fischer- Tropsch catalyst or catalyst precursor is prepared.

3. A process as claimed in claim 1 or 2 wherein the catalytically active component is a catalytically active metal, or a mixture of catalytically active metals, selected from the group comprising: cobalt, iron, ruthenium, and mixtures thereof; preferably cobalt.

4. A process as claimed in any one of the preceding claims wherein the carrier material is a refractory metal oxide, preferably titania or zirconia.

5. A process as claimed in any one of the preceding claims wherein the particles of fresh, optionally calcined, catalyst or catalyst precursor material have a size wholly or substantially in the range of 2 to 50 μm, preferably 5-20 μm.

6. A process as claimed in any one of the preceding claims wherein the particles of fresh, optionally calcined, catalyst or catalyst precursor material have a hardness of at least 5.5 on the Mohs hardness scale.

7. A process as claimed in any one of the preceding claims wherein the particles of fresh, optionally calcined, catalyst or catalyst precursor material occupy 1 to 20% of the weight of the catalyst or catalyst precursor after the calcination step (c).

8. A process as claimed in any one of the preceding claims wherein in step (a) inert particles are admixed, said particles having a size wholly or substantially in the range of 1 to 100 μm, preferably 2 to 50 μm, more preferably 5-20 μm.

9. A process as claimed in claim 8 wherein the inert particles are refractory oxides including silica, alumina, titania, quartz and quartzite.

10. A process as claimed in claim 8 or 9 wherein the inert particles have a hardness of at least 5.5 on the Mohs hardness scale.

11. A process for producing normally gaseous, normally liquid and optionally normally solid hydrocarbons from synthesis gas which comprises the steps of:

(i) providing the synthesis gas; and (ii) catalytically converting the synthesis gas of step (i) at an elevated temperature and pressure to obtain the normally gaseous, normally liquid and optionally normally solid hydrocarbons; wherein the catalyst for step (ii) is catalyst produced according to any one of the claims 1 to 10.

12. A catalyst or catalyst precursor prepared by a process as defined in any one of claims 1 to 10.

13. Use of a catalyst as defined in claim 12 in a process for producing normally gaseous, normally liquid and optionally normally solid hydrocarbons from synthesis gas which comprises the steps of: (i) providing the synthesis gas; and (ii) catalytically converting the synthesis gas of step (i) at an elevated temperature and pressure to obtain the normally gaseous, normally liquid and optionally normally solid hydrocarbons .