Patent Description:
The invention also relates to a process for the preparation of Fischer-Tropsch synthesis catalysts comprising an extruded titania-based material comprising mesopores and macropores and having reduced selectivity for methane and/or improved selectivity for C<NUM>+ hydrocarbons in Fischer-Tropsch reactions.

The conversion of synthesis gas into hydrocarbons by the Fischer-Tropsch process has been known for many years. The growing importance of alternative energy sources has seen renewed interest in the Fischer-Tropsch process as one of the more attractive direct and environmentally acceptable routes to high quality transportation fuels.

Many metals, for example cobalt, nickel, iron, molybdenum, tungsten, thorium, ruthenium, rhenium and platinum are known to be catalytically active, either alone or in combination, in the conversion of synthesis gas into hydrocarbons and oxygenated derivatives thereof. Of the aforesaid metals, cobalt, nickel and iron have been studied most extensively. Generally, the metals are used in combination with a support material, of which the most common are alumina, silica and carbon.

In the preparation of metal-containing Fischer-Tropsch catalyst, a solid support is typically impregnated with a metal-containing compound, such as a cobalt-containing compound, which may for instance be an organometallic or inorganic compound (e.g. Co(NO<NUM>)<NUM>. <NUM><NUM>O), by contacting with a solution of the compound. The particular form of metal-containing compound is generally selected for its ability to form an appropriate oxide (for example Co<NUM>O<NUM>) following a subsequent calcination/oxidation step. Following generation of the supported metal oxide, a reduction step is necessary in order to form the pure metal as the active catalytic species. Thus, the reduction step is also commonly referred to as an activation step.

It is known to be beneficial to perform Fischer-Tropsch catalysis with an extrudate, particularly in the case of fixed catalyst bed reactor systems. It is, for instance, known that for a given shape of catalyst particles, a reduction in the size of the catalyst particles in a fixed bed gives rise to a corresponding increase in pressure drop through the bed. Thus, the relatively large extrudate particles cause less of a pressure drop through the catalyst bed in the reactor compared to the corresponding powered or granulated supported catalyst. It has also been found that extrudate particles generally have greater strength and experience less attrition, which is a particular value in fixed bed arrangements where bulk crush strength may be very high.

An impregnated extrudate may be formed by mixing a solution of a metal-compound with a support material particulate, mulling, and extruding to form an extrudate before drying and calcining. Alternatively, an extrudate of a support material is directly impregnated, for instance by incipient wetness, before drying and calcining.

Commonly used support materials for Fischer-Tropsch catalysts include alumina, silica and carbon; however, a particularly useful material is extruded titania (titanium dioxide). Extruded titania support materials typically have a mesoporous structure, i.e. the extruded material comprises pores having a pore size of <NUM> to <NUM>.

<CIT> discloses titania based catalyst carriers for use in applications requiring a balance of surface area and crush strength can be obtained by using as the starting material a titania hydrate pulp with a surface area above about <NUM> m2/g and an LOI of from about <NUM>% to about <NUM>% by weight.

<CIT> discloses a method of forming a shaped article includes forming a mixture which includes a titania hydrate pulp having a loss on ignition of from about <NUM> to <NUM> wt. %, a seed material comprising a titanium oxide, at least a portion of the titanium oxide being in a rutile form, and optionally a dispersion aid. The method includes forming the mixture into a shaped article and firing the shaped article. A shaped article suitable for use as a catalyst carrier is at least <NUM>% titanium oxide, greater than <NUM>% of the titanium oxide being in the rutile phase. The article has a surface area of at least <NUM><<NUM>>/g and a mercury pore volume of greater than <NUM> cc/g.

<CIT> discloses a process for regenerating one or more deactivated cobalt comprising Fischer-Tropsch catalyst particle(s), comprising the steps of: (i) oxidising the catalyst particle(s) at a temperature between <NUM> and <NUM>. ; (ii) treating the catalyst particle(s) for more than <NUM> minutes, (iii) drying the catalyst particle(s); and (iv) optionally reducing the catalyst particle(s) with hydrogen or a hydrogen comprising gas. This process may be preceded by a step in which Fischer-Tropsch product is removed from the catalyst particle(s). The treatment is performed using carbon dioxide and a liquid comprising ammonia.

It is known that including macropores, i.e. pores having diameters of greater than <NUM>, in catalyst support materials can be beneficial, for example by allowing increased metal loading and/or molecular diffusion. However, the incorporation of macropores may result in a reduction in the surface area of the catalyst support material, which can be detrimental, because it reduces the number of active sites for catalysis. Porous, extruded titania-based materials comprising mesopores and macropores have not previously been produced or suggested for use as catalyst supports. There therefore remains a need for a porous, extruded titania-based material comprising mesopores and macropores.

It has now surprisingly been found that including a porogen during the extrusion of a titania-based material enables the formation of both macropores and mesopores following removal of the porogen by thermal or oxidative decomposition. Surprisingly, the macropores may be formed without a significant impact on surface area. Fischer-Tropsch catalysts produced from such materials also have surprisingly improved catalyst activity and/or selectivity.

Thus, in a first aspect there is disclosed a porous, extruded titania-based material comprising mesopores and macropores.

There is further disclosed a process for the production of a porous, extruded titania-based material comprising mesopores and macropores according to the invention, said process comprising:.

The present invention provides a Fischer-Tropsch synthesis catalyst according to claim <NUM> comprising a porous, extruded titania-based material comprising mesopores having a pore diameter of <NUM> to <NUM> and macropores having a pore diameter of greater than <NUM> wherein the mesopores and macropores are present in a bi-modal distribution and further comprising cobalt.

The present invention yet further provides a process for the preparation of a Fischer-Tropsch synthesis catalyst according to any of claims <NUM> to <NUM>, said process comprising:.

The present invention further provides a process for the preparation of a Fischer-Tropsch synthesis catalyst according to any of claims <NUM> to <NUM>, said process comprising:.

There is yet further provided the use of a porogen to prepare a porous, extruded titania-based material comprising mesopores and macropores, and also the use of a porogen to prepare a porous, extruded titania-based Fischer-Tropsch synthesis catalyst comprising mesopores and macropores.

In a further aspect, the present invention provides a process for converting a mixture of hydrogen and carbon monoxide gases to hydrocarbons, which process comprises contacting a mixture of hydrogen and carbon monoxide with a Fischer-Tropsch synthesis catalyst according to any of claims <NUM> to <NUM>.

There is further provided a composition, preferably a fuel composition, comprising hydrocarbons obtained by a process according to the invention.

There is further provided a process for producing a fuel composition, said process comprising blending hydrocarbons obtained by a process according to the invention with one or more fuel components to form the fuel composition.

The pore diameter of the porous, extruded titania-based material comprising mesopores and macropores according to the present invention may be measured by any suitable method known to those skilled in the art, for example scanning electron microscopy or mercury porosimetry based on mercury intrusion using the Washburn equation with a mercury contacting angle of <NUM>° and a mercury surface tension of <NUM> dynes/cm. As used herein, the term "pore diameter" equates with "pore size" and consequently refers to the average cross-sectional dimension of the pore, understanding, as the skilled person does, that a determination of pore size typically models pores as having circular cross-sections.

The porous, extruded titania-based material comprises bi-modal distribution of pore sizes/pore diameters, i.e. a range of pore sizes/pore diameters comprising two modes, the first mode representing mesopores and the second mode representing macropores.

The porous, extruded titania-based material comprising mesopores and macropores according to the present invention comprises mesopores having a pore diameter of <NUM> to <NUM>, for example <NUM> to <NUM>, preferably <NUM> to <NUM> or <NUM> to <NUM>, more preferably <NUM> to <NUM> or <NUM> to <NUM>.

The porous, extruded titania-based material comprising mesopores and macropores according to the present invention comprises macropores having a pore diameter of greater than <NUM>, preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>.

The pore volume of a porous, extruded titania-based material comprising mesopores and macropores according to the present invention may be measured by any suitable method known to those skilled in the art, for example using mercury porosimetry.

Suitably, the porous, extruded titania-based material according to the present invention has a total pore volume of at least <NUM>/g, preferably at least <NUM>/g, more preferably at least <NUM>/g. The upper limit of the total pore volume is not critical, so long as the material remains sufficiently robust to function as a catalyst support; however, a suitable maximum pore volume may be <NUM>/g, preferably <NUM>/g. Particularly preferred ranges of total pore volume for a porous, extruded titania-based material comprising mesopores and macropores according to the present invention are <NUM> to <NUM>/g, such as <NUM> to <NUM>/g, <NUM> to <NUM>/g or <NUM> to <NUM>/g.

The surface area of a porous, extruded titania-based material comprising mesopores and macropores according to the present invention may be measured in any suitable way known to those skilled in the art, such as by nitrogen porosimetry using the BET model to the nitrogen adsorption isotherm collected at <NUM> on a Quadrasorb SI unit (Quantachrome).

Suitably, a porous, extruded titania-based material comprising mesopores and macropores according to the present invention has a surface area of at least <NUM><NUM>/g, preferably at least <NUM><NUM>/g. The upper limit of the surface area is not critical, so long as the material is suitable for the intended use, such as a catalyst support; however, a suitable maximum surface area may be <NUM><NUM>/g or <NUM><NUM>/g. A particularly suitable range of surface area for a porous, extruded titania-based material comprising mesopores and macropores of the present invention is <NUM> to <NUM><NUM>/g, preferably <NUM> to <NUM><NUM>/g.

The BET surface area, pore volume, pore size distribution and average pore radius of a porous, extruded titania-based material comprising mesopores and macropores may additionally be determined from the nitrogen adsorption isotherm determined at <NUM> using a Micromeritics TRISTAR <NUM> static volumetric adsorption analyser. A procedure which may be used is an application of British Standard method BS4359: Part <NUM>: <NUM>, "Recommendations for gas adsorption (BET) methods" and BS7591: Part <NUM>: <NUM>, "Porosity and pore size distribution of materials" - Method of evaluation by gas adsorption. The resulting data may be reduced using the BET method (over the relative pressure range <NUM> - <NUM> P/P<NUM>) and the Barrett, Joyner & Halenda (BJH) method (for pore diameters of <NUM> to <NUM>) to yield the surface area and pore size distribution respectively. Nitrogen porosimetry, such as described above, is the preferred method for determining the surface areas of the extruded titania-based materials according to the present invention.

Suitable references for the above data reduction methods are <NPL>) and<NPL>.

As a further alternative, pore volume may be estimated through mercury porosimetry by use of an AutoPore IV (Micromeritics) instrument, and pore diameter may be measured from the mercury intrusion branch using the Washburn equation with a mercury contacting angle at <NUM>° and a mercury surface tension of <NUM> dynes/cm. Further details are provided in ASTM D4284-<NUM> Standard Test Method for Determining Pore Volume Distribution of Catalysts and Catalyst Carriers by Mercury Intrusion Porosimetry; and <NPL>); <NPL>. Mercury porosimetry, such as described above, is the preferred method for determining the pore volumes and pore diameters of the extruded titania-based materials according to the present invention.

The porous, extruded titania-based material comprising mesopores and macropores according to the present invention generally has a symmetrical geometry that includes, but is not limited to, cylinders, spheres, spheroids, pastilles, dilobes, such as cylindrical dilobes, trilobes , such as cylindrical trilobes, quadralobes, such as cylindrical quadralobes and hollow cylinders.

The porous, extruded titania-based material comprising mesopores and macropores according to the present invention may be prepared by any suitable extrusion process known to those skilled in the art, but modified so that one or more porogens are included in the titania-based material during extrusion and are subsequently removed by thermal or oxidative decomposition.

The porous, extruded titania-based material comprising mesopores and macropores according to the present invention may be prepared using any suitable form of titanium oxide, such as titanium dioxide (<NPL>), titanium dioxide anatase (<NPL>), titanium dioxide rutile (<NPL>), titanium dioxide brookite (<NPL>), and ad-mixtures or composites thereof.

Where the porous, extruded titania-based material comprising mesopores and macropores according to the present invention is to be used as a catalyst support it is preferably substantially free of extraneous metals or elements which might adversely affect the catalytic activity of the system. Thus, preferred porous, extruded titania-based materials comprising mesopores and macropores according to the present invention are preferably at least <NUM>% w/w pure, more preferably at least <NUM>% w/w pure. Impurities preferably amount to less than <NUM>% w/w, more preferably less than <NUM>% w/w and most preferably less than <NUM>% w/w. The titanium oxide from which the porous, extruded titania-based material is formed is preferably of suitable purity to achieve the above preferred purity in the finished extruded product.

The porous, extruded titania-based material comprising mesopores and macropores according to the present invention may be prepared using any suitable porogen, i.e. a material capable of enabling the formation of macropores in an extruded titania-based material once it has been removed therefrom, for example by thermal or oxidative decomposition.

Suitable porogens for use in the process for the production of a porous, extruded titania-based material comprising mesopores and macropores according to the present invention comprise cellulose or derivatives thereof, such as methyl cellulose (<NPL>), ethyl cellulose (<NPL>) and ethyl methyl cellulose (<NPL>); alginic acid (<NPL>) or derivatives thereof, such as ammonium alginate (<NPL>), sodium alginate (<NPL>) and calcium alginate (<NPL>); latex, such as polystyrene latex (<NPL>) or polyvinylchloride (<NPL>).

The proportion of total porogen to titanium dioxide used in the process of the present invention may be selected so as to provide a suitable proportion of macropores in the porous, extruded titania-based material. However, a preferred weight ratio of titanium dioxide to total porogen is from <NUM>:<NUM> to <NUM>:<NUM>, preferably <NUM>:<NUM> to <NUM>:<NUM>, more preferably <NUM>:<NUM> to <NUM>:<NUM>.

In the process for the production of a porous, extruded titania-based material comprising mesopores and macropores according to the present invention, the titanium dioxide and one or more porogens may be mixed using any suitable technique to form a homogenous mixture, such as by mixing in a mechanical mixer. The liquid extrusion medium used to form a homogenous paste may be added to the homogenous mixture once mixing of the titanium dioxide and one or more porogens is complete, in which case mixing to form a homogenous paste may be carried out in the same apparatus used to form the homogenous mixture or in a different apparatus. Alternatively, the liquid extrusion medium may be added during the mixing of the titanium dioxide and one or more porogens, in which case mixing to form a homogenous paste will generally be carried out in the same equipment as used to form the homogenous mixture.

Any suitable liquid extrusion medium may be used in the process of the present invention, i.e. any liquid capable of causing the titanium dioxide and one or more porogens to form a homogenous paste suitable for extrusion. Water is an example of a suitable liquid extrusion medium.

The process for the production of a porous, extruded titania-based material comprising mesopores and macropores according to the present invention may optionally further comprise a mulling step to reduce the presence of larger particles that may not be readily extruded, or the presence of which would otherwise compromise the physical properties of the resulting extrudate. Any suitable mulling or kneading apparatus of which a skilled person is aware may be used for mulling in the context of the present invention. For example, a pestle and mortar may be suitably used in some applications or a Simpson muller may suitably be employed. Mulling is typically undertaken for a period of from <NUM> to <NUM> minutes, preferably for a period of <NUM> minutes to <NUM> minutes. Mulling may suitably be undertaken over a range of temperatures, including ambient temperatures. A preferred temperature range for mulling is from <NUM> to <NUM>. Mulling may suitably be undertaken at ambient pressures.

The homogenous paste formed in the process for the production of a porous, extruded titania-based material comprising mesopores and macropores according to the present invention may be extruded to form an extrudate using any suitable extruding methods and apparatus of which the skilled person is aware. For example, the homogenous paste may be extruded in a mechanical extruder (such as a Vinci VTE <NUM>) through a die with an array of suitable diameter orifices, such as <NUM>/<NUM> inch diameter, to obtain extrudates with cylindrical geometry.

The extrudate formed in a process for the production of a porous, extruded titania-based material comprising mesopores and macropores according to the present invention may be calcined at any temperature sufficient to at least partly decompose the one or more porogens, and preferably to fully decompose the one or more porogens.

Optionally, a drying step may be carried out before calcining.

Drying in accordance with the present invention is suitably conducted at temperatures of from <NUM> to <NUM>, preferably <NUM> to <NUM>. Suitable drying times are from <NUM> minutes to <NUM> hours. Drying may suitably be conducted in a drying oven or in a box furnace, for example, under the flow of an inert gas at elevated temperatures.

Calcination may be performed by any method known to those of skill in the art, for example in a fluidised bed or a rotary kiln, suitably at a temperature of at least <NUM>, and preferably in the range of from <NUM> to <NUM>, more preferably from <NUM> to <NUM>, and yet more preferably from <NUM> to <NUM>. Where the one or more porogens comprise cellulose, or a derivative thereof, and/or alginic acid, or a derivative thereof, calcining is preferably carried out at a temperature of at least <NUM>, and preferably at least <NUM>, more preferably <NUM> to <NUM>.

The Fischer-Tropsch synthesis catalyst according to the present invention comprises a porous, extruded titania-based material comprising mesopores and macropores according to the present invention and further comprises cobalt. The amount of metal, on an elemental basis, present in the Fischer-Tropsch synthesis catalyst according to the present invention is suitably from <NUM> wt% to <NUM> wt%, preferably <NUM> wt% to <NUM> wt%, more preferably <NUM> wt% to <NUM> wt%, based on the total weight of the catalyst. As will be appreciated by the skilled person, the amount of metal, on an elemental basis, present in the Fischer-Tropsch synthesis catalyst may be readily determined by X-ray fluorescence (XRF) techniques.

The Fischer-Tropsch synthesis catalyst according to the present invention may additionally comprise one or more promoters, dispersion aids, binders or strengthening agents. Promoters are typically added to promote reduction of an oxide of metal to pure metal; for example cobalt to cobalt metal, preferably at lower temperatures. Preferably, the one or more promoters are selected from rhenium, ruthenium, platinum, palladium, molybdenum, tungsten, boron, zirconium, gallium, thorium, manganese, lanthanum, cerium or mixtures thereof. The promoter is typically used in a metal to promoter atomic ratio of up to <NUM>:<NUM>, and more preferably up to <NUM>:<NUM>, still more preferably up to <NUM>:<NUM>, and most preferably <NUM>:<NUM>.

The Fischer-Tropsch synthesis catalyst according to the present invention may be prepared by incorporating a solution of at least one thermally decomposable cobalt compound into a process for the production of a porous, extruded titania-based material comprising mesopores and macropores according to the present invention, i.e. by adding the solution of at least one thermally decomposable cobalt compound at any stage before extrusion of the homogenous paste.

Alternatively, the Fischer-Tropsch synthesis catalyst according to the present invention may be prepared by impregnating a porous, extruded titania-based material comprising mesopores and macropores according to the present invention with a solution of at least one thermally decomposable cobalt compound. Impregnation of the porous, extruded titania-based material comprising mesopores and macropores with the solution of at least one thermally decomposable cobalt compound in accordance with the present invention may be achieved by any suitable method of which the skilled person is aware, for instance by vacuum impregnation, incipient wetness or immersion in excess liquid. The impregnating solution may suitably be either an aqueous solution or a non-aqueous, organic solution of the thermally decomposable metal compound. Suitable non-aqueous organic solvents include, for example, alcohols, ketones, liquid paraffinic hydrocarbons and ethers. Alternatively, aqueous organic solutions, for example an aqueous alcoholic solution, of the thermally decomposable metal-containing compound may be employed. Preferably, the solution of the thermally decomposable metal-containing compound is an aqueous solution.

Suitable metal-containing compounds are those which are thermally decomposable to an oxide of the metal following calcination, or which may be reduced directly to the metal form following drying and/or calcination, and which are completely soluble in the impregnating solution. Preferred metal-containing compounds are the nitrate, acetate or acetyl acetonate salts of cobalt, most preferably the nitrate, for example cobalt nitrate hexahydrate.

Following extrusion, the extrudate may be calcined at a temperature sufficient to decompose the one or more porogens and to convert the at least one thermally decomposable cobalt compound to an oxide thereof or to the metal form. Optionally, the extrudate may be dried before the calcining step.

Following impregnation, the impregnated extrudate may be dried and/or calcined at a temperature sufficient to convert the at least one thermally decomposable cobalt containing compound to an oxide thereof or to the metal form.

The drying and calcining temperatures and conditions suitable for producing a porous, extruded titania-based material comprising mesopores and macropores according to the present invention are also suitable for use in the processes for preparing Fischer-Tropsch synthesis catalysts according to the present invention.

Where an oxide of cobalt is formed during a process for the preparation of a Fischer-Tropsch synthesis catalyst according to the present invention, the material may be used as a catalyst in a Fischer-Tropsch reaction without further processing, and the oxide of cobalt will be converted to the metal form during such use. Alternatively, the material comprising an oxide of cobalt may optionally be heated under reducing conditions to convert the at least one cobalt oxide to the metal form before use as a Fischer-Tropsch synthesis catalyst. Any suitable means for converting the oxide of cobalt to the metal form known to those skilled in the art may be used.

Where promoters, dispersion aids, binders and/or strengthening aids are incorporated in the Fischer-Tropsch synthesis catalyst according to the present invention, the addition of these materials may be integrated at several stages of the process according to the present invention. Preferably, the promoter, dispersion aids, binder or strengthening aids are admixed during any stage prior to extrusion, or during the impregnation step.

The Fischer-Tropsch synthesis catalyst comprising a porous, extruded titania-based material comprising mesopores and macropores according to the present invention or a Fischer-Tropsch synthesis catalyst obtainable by a process according to the present invention may be used as a catalyst in any conventional Fischer-Tropsch process for converting a mixture of hydrogen and carbon monoxide gases to hydrocarbons. The Fischer-Tropsch synthesis of hydrocarbons from a mixture of hydrogen and carbon monoxide, such as syngas, may be represented by Equation <NUM>:.

mCO + (<NUM>+<NUM>)H<NUM> → mH<NUM>O + CmH<NUM>+<NUM>     Equation <NUM>.

As discussed hereinbefore, the Fischer-Tropsch synthesis catalysts according to the present invention have been surprisingly found to have improved catalyst activity and/or selectivity, particularly reduced selectivity for methane. The Fischer-Tropsch synthesis catalyst according to the present invention therefore provides particularly useful ranges of hydrocarbons when used in a Fischer-Tropsch reaction.

A composition comprising hydrocarbons obtained by a process of the present invention is preferably a fuel composition, for example a gasoline, diesel or aviation fuel or precursor thereof.

The present invention will now be illustrated by way of the following Examples and with reference to the following Figures:.

Titanium dioxide (BASF P25) was formulated with distilled water in a mechanical mixer (Vinci MX <NUM>) and then extruded using a mechanical extruder (Vinci VTE <NUM>) through a die with an array of <NUM>/<NUM> inch diameter orifices to obtain extrudates with cylindrical geometry.

The extrudates were dried at a temperature of <NUM> to <NUM> overnight, followed by calcination in air flow at <NUM> for four hours, via a ramp of <NUM>/min.

The resultant extrudate was characterised using nitrogen porosimetry (Quantachrome, Quadrasorb SI), mercury porosimetry (Micromeritics, AutoPore IV) and scanning electron microscopy.

<FIG> depicts the pore size distribution (PDS) of the extrudate prepared in Comparative Example <NUM> estimated from the mercury intrusion data using the Washburn equation with a contact angle of <NUM>° and a surface tension of bulk mercury of <NUM> mN/m. This sample exhibits only mesopores, with mean pore diameters of <NUM>. The pore volume and surface area of this material is shown in Table <NUM>. The total pore volume of this material is approximately <NUM>/g as determined from the mercury intrusion data. The surface area of this material analysed from the nitrogen adsorption isotherm using the Brunaeur-Emmett-Teller (BET) model is <NUM><NUM>/g.

A porous, titania-based extrudate was prepared by mixing a predetermined amount of titanium oxide (BASF P25) and a cellulose (Aldrich, Sigmacell Type <NUM>) in a <NUM>° rotating mixer (Turbula) and then formulating with distilled water in a mechanical mixer to obtain a paste with a mass ratios of titania to cellulose and water of <NUM>:<NUM>:<NUM>. The resulting paste was extruded through a die with <NUM>/<NUM> inch diameter holes to obtain extrudates with cylindrical rod geometry.

The extrudate was dried at <NUM> overnight, followed by calcination at <NUM> for four hours, via a ramp of <NUM>/min.

The resultant extrudate was characterised using nitrogen porosimetry, mercury porosimetry, and scanning electron microscopy, as described in Comparative Example <NUM>.

<FIG> depicts the pore size distribution of the material of Example <NUM>, and shows a bi-modal pore distribution centred at <NUM> (mesopores) and <NUM> (macropores).

<FIG> shows scanning electron micrographs of samples of the extrudate formed in Example <NUM> at various magnifications, and clearly demonstrates the presence of uniform wormhole-like macropores in the extrudate.

Total pore volume and surface area values for the material of Example <NUM> are shown in Table <NUM>. Owing to the formation of macropores, this material exhibits a mercury intrusion pore volume of <NUM>/g, which is substantially higher than the value (<NUM>/g) of the material formulated without using porogen (Comparative Example <NUM>). BET surface area of the material of Example <NUM> is <NUM><NUM>/g, which is very similar to the extrudate formed without using the porogen in Comparative Example <NUM>.

A porous, titania-based extrudate was prepared according to the procedure set out in Example <NUM>, with the exception that the mass ratio of titanium oxide to cellulose was adjusted to <NUM>:<NUM>. The mixture of titanium oxide and cellulose was homogenised with a Turbula mixer, formulated with water in the trough of a Vinci mixer, extruded using a Vinci extruder, and dried and calcined as set out in Example <NUM>.

The extrudate of Example <NUM> was characterised using nitrogen porosimetry, mercury porosimetry and scanning electron microscopy as described in Comparative Example <NUM>, and the results are shown in Table <NUM>.

The material of Example <NUM> exhibited a bi-modal pore size distribution with peaks at <NUM> and <NUM>, respectively. Total pore volume was <NUM>/g, and the BET surface area of the sample was <NUM><NUM>/g.

The procedure of Example <NUM> was repeated, with the exception that the mass ratio of titania to cellulose was adjusted to <NUM>:<NUM>. The resulting mixture was homogenised, formulated with water, extruded, dried and calcined as set out in Example <NUM>.

The extrudate of Example <NUM> was characterised as set out in Comparative Example <NUM>, and the results are shown in Table <NUM>.

The calcined extrudate of Example <NUM> exhibited a bi-modal pore size distribution with peaks at <NUM> and <NUM>, respectively. The total pore volume was <NUM>/g, and the BET surface area was <NUM><NUM>/g.

The procedure of Example <NUM> was repeated, with the exception that an alternative form of cellulose (Aldrich Cellulose Fibre) was used as the porogen at a mass ratio of titania to cellulose of <NUM>:<NUM>.

The mixture was homogenised, formulated with water, extruded, dried and calcined as set out in Example <NUM>.

The calcined extrudate of Example <NUM> was characterised as set out in Comparative Example <NUM>, and the results are shown in Table <NUM>.

The procedure of Example <NUM> was repeated, with the exception that an alternative form of cellulose (Aldrich Sigmacell Type <NUM>) was used as the porogen at a mass ratio of titanium oxide to cellulose of <NUM>:<NUM>.

The procedure of Example <NUM> was repeated, with the exception that an alternative cellulose (Aldrich Sigmacell Type <NUM>) was used as the porogen at a mass ratio of titanium oxide to cellulose of <NUM>:<NUM>.

The procedure of Example <NUM> was repeated, with the exception that alginic acid (Aldrich) was used as the porogen at a mass ratio of titanium dioxide to alginic acid of <NUM>:<NUM>.

The materials set out in Example <NUM> were used to prepare a porous, extruded titania-based material comprising mesopores and macropores on a pilot scale. The titanium oxide (BASF P25) and cellulose fibre (Aldrich Cellulose Fibre) were mixed at a mass ratio of titanium oxide to cellulose of <NUM>:<NUM>.

The mixture was homogenised and formulated with water in a Simpson Muller, and the subsequent paste was extruded using a Bonnet Extruder. The extrudate was dried and calcined as set out in Example <NUM>.

A comparison of the results for Comparative Example <NUM> and Examples <NUM> to <NUM>, as shown in Table <NUM>, clearly shows that the inclusion of a porogen before the extrusion stage, and the subsequent removal thereof, allows the preparation of a porous, extruded titania-based material comprising mesopores and macropores. The resulting materials also have significantly increased total pore volume, but without any effect on BET surface area.

A Fischer-Tropsch catalyst was prepared by loading the porous, extruded titania-based material comprising mesopores of Comparative Example <NUM> with a loading of <NUM>% cobalt and <NUM>% manganese; for example, by impregnation with an aqueous solution of cobalt nitrate and manganese acetate using an incipient wetness procedure, followed by drying in air at <NUM>° C for <NUM> hours and <NUM>° C for <NUM> hours, and calcining at <NUM>° C for <NUM> hours with a ramp rate between soaking steps of <NUM>° C/min.

The Fischer-Tropsch catalyst of Comparative Example <NUM> was characterised as set out in Comparative Example <NUM>, and the material was found to comprise only mesopores, with mean pore diameters of <NUM>.

A Fischer-Tropsch catalyst comprising mesopores and macropores was prepared by loading the porous, extruded titania-based material comprising mesopores and macropores of Example <NUM> with <NUM>% cobalt and <NUM>% manganese, using the method set out in Comparative Example <NUM>.

The Fischer-Tropsch catalyst of Example <NUM> was characterised as set out in Comparative Example <NUM>, and was found to exhibit a bi-modal pore distribution having peaks at <NUM> and <NUM>, respectively.

The Fischer-Tropsch catalysts of Comparative Example <NUM> and Example <NUM> were tested to determine their activity and selectivity in a Fischer-Tropsch process as follows.

The catalysts were each loaded into a fixed bed testing reactor, then reduced in-situ in hydrogen flow at <NUM> for <NUM> hours. Synthesis gas (a mixture of carbon monoxide and hydrogen) was passed over the catalyst bed using the following conditions:.

Each catalyst was run for a sufficient period to obtain steady state conditions and the temperature was adjusted to provide a particular level of carbon monoxide conversion (typically between about <NUM> and <NUM>%). The temperature and pressure were stabilised at <NUM> and <NUM> barg respectively.

Exit gases were sampled by on-line gas chromatography, and analysed for gaseous products. The degree of carbon monoxide conversion, methane selectivity and selectivity for C<NUM>+ hydrocarbons were determined for each catalyst. The results are shown in Table <NUM>.

As will be seen from Table <NUM>, the Fischer-Tropsch catalyst of Example <NUM> comprising mesopores and macropores has improved carbon monoxide conversion and improved selectivity to C<NUM>+ hydrocarbons compared to the Fischer-Tropsch catalyst of Comparative Example <NUM> (comprising only mesopores). Additionally, the Fischer-Tropsch catalyst of Example <NUM> has significantly reduced selectivity to methane compared to the Fischer-Tropsch catalyst of Comparative Example <NUM>, which is particularly advantageous because methane is one of the major components in typical synthesis gas feeds, and the conversion of synthesis gas back to methane is highly undesirable in Fischer-Tropsch processes.

Claim 1:
A Fischer-Tropsch synthesis catalyst comprising a porous, extruded titania-based material comprising mesopores having a pore diameter of <NUM> to <NUM> and macropores having a pore diameter of greater than <NUM> wherein the mesopores and macropores are present in a bi-modal distribution, and wherein the catalyst further comprises cobalt.