BR112020019091B1 - FISCHER-TROPSCH CATALYST CONTAINING SUPPORTED COBALT, PROCESS FOR PREPARING THE SAME AND PROCESS FOR CONVERTING A FEED COMPRISING A MIXTURE OF GASES - Google Patents

Abstract

A FISCHER-TROPSCH CATALYST CONTAINING SUPPORTED COBALT, PROCESS FOR PREPARING THE SAME AND USES THEREOF. The present invention relates to a process for preparing a Fischer-Tropsch synthesis catalyst containing cobalt with good physical properties and high cobalt loading. In one aspect, the present invention provides a process for preparing a supported cobalt-containing Fischer-Tropsch synthesis catalyst, wherein said process comprises the steps of: (a) impregnating a support material with cobalt hydroxide nitrate, or a hydrate thereof, of formula (I) below to form an impregnated support material, [Co(OH)x(NO3)(2-x).yH2O] (I) where: 0 2 0=y=6 ( b) dry and calcine the impregnated support material.

Description

[0001] The present invention relates to a process for preparing a Fischer-Tropsch synthesis catalyst that contains supported cobalt and using it in a Fischer-Tropsch reaction. In particular, the supported cobalt-containing Fischer-Tropsch synthesis catalyst is prepared using a source of cobalt in the form of a cobalt hydroxide nitrate compound, or a hydrate thereof. The invention also provides uses of the supported cobalt-containing Fischer-Tropsch synthesis catalyst prepared by the process, as well as a process for preparing the cobalt hydroxide nitrate compound, or a hydrate thereof, which is employed as the source of cobalt. .

[0002] 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 sparked new interest in the Fischer-Tropsch process as one of the most attractive and environmentally acceptable direct routes to high-quality transportation fuels.

[0003] Many metals, for example, cobalt, nickel, iron, molybdenum, tungsten, thorium, ruthenium, rhenium and platinum are known to be catalytically active, either separately or in combination, in converting synthesis gas into hydrocarbons and oxygenated derivatives of the same. Among the metals mentioned above, cobalt, nickel and iron have been studied most intensively. Generally speaking, metals are used in combination with a support material, the most common of which are alumina, silica and carbon.

[0004] In the preparation of cobalt-containing Fischer-Tropsch catalysts, a solid support is typically impregnated with a cobalt-containing compound, which may, for example, be an organometallic or inorganic compound (e.g., Co(OH)2 and Co(NO3)2.6H2O), placing it in contact with a solution of the compound. The particular form of the cobalt-containing compound is typically selected for its ability to form a cobalt oxide (e.g., CoO, Co2O3 or Co3O4) after a subsequent calcination/oxidation step.

[0005] After generation of supported cobalt oxide, a reduction step is necessary in order to form pure cobalt metal as the active catalytic species. Therefore, the reduction step is also commonly referred to as an activation step. Several different methods of activating a Fischer-Tropsch catalyst or regenerating a used Fischer-Tropsch catalyst are known.

[0006] A main focus in adapting the Fischer-Tropsch synthesis catalyst is to improve activity and selectivity for C5+ hydrocarbonates, in particular paraffinic hydrocarbons. It is generally understood that the selectivity for C5+ hydrocarbons in the Fischer-Tropsch synthesis reaction is increased by operating at lower temperatures. By providing a higher activity catalyst, it may be possible to achieve the same level of synthesis gas conversion at lower temperatures, whilst there is benefit from improved C5+ hydrocarbon selectivity. Thus, a higher activity catalyst also represents a means to modify the selectivity of the Fischer-Tropsch synthesis allowing a reduction in the operating temperature. An additional focus in adapting Fischer-Tropsch synthesis catalysts is to enhance the conversion of synthesis gas or other mixtures of hydrogen and carbon monoxide gases into hydrocarbons.

[0007] Previous research has revealed that the cobalt content in catalysts is a decisive factor for the operating performance of Fischer-Tropsch catalysts. A loading of up to approximately 10 wt% cobalt on an elemental basis was quickly achieved by the impregnation step with a completely dissolved solution of cobalt-containing compound, without compromising the physical properties of the supported Fischer-Tropsch synthesis catalyst. Impregnation of a powder or granulated support with a solution like this also ensures that a mixture is obtained which is suitable for extrusion. It has been observed that larger solution volumes, which correspond to higher loadings of cobalt-containing compound, can lead to problems with consistency, which can prevent satisfactory shaping of the extrusion-impregnated support material.

[0008] The formation of cobalt-containing extrudates from commercially available preformed extrudates presents similar limitations in the concentration of cobalt that can be achieved on the supported catalyst in a single impregnation step. As described, for example, in WO 2011/062773 and WO 99/34917, a single impregnation step with a solution of a cobalt-containing compound has historically been unable or difficult to achieve a cobalt metal loading above 10% in Weight.

[0009] As such, multiple impregnations are normally required to provide extrudates with metal fillers that may be only marginally lower, yet at significant additional costs, as described, for example, in document WO 2016/097402.

[0010] Furthermore, the use of partially undissolved solid solutions, which require lower volumes of liquid, can negatively impact the distribution of the cobalt-containing compound on the support and, in some cases, leads to poor morphology and low resistance to resistance. mass crushing into an extrudate.

[0011] Document WO 99/34917 describes a process for forming an extrudate with a higher cobalt metal filler of, for example, 20% by weight, by means of a single impregnation with a partially undissolved solution (a “solid solution” ) of a compound containing cobalt. Such a solid solution can be formed by precipitation of the cobalt compound after adding a base to a compound solution containing soluble cobalt. Although the method reported in WO 99/34917 is capable of forming extrudates with higher cobalt metal fillers and thus higher catalyst activities than was previously possible in a single impregnation step, the extrudates obtained by this method suffer from low resistance to crushing in bulk and poor morphology.

[0012] Thus, in obtaining superior cobalt metal filler, the advantages associated with the use of an extrudate are a nullified effect. Furthermore, it has been previously observed that the use of a solid solution to impregnate particulate backing material results in poor dispersion of cobalt-containing compound over the surface and pores of the backing material, which can negatively impact the performance of the backing material. catalyst and useful life.

[0013] It is known that cobalt hydroxide is less soluble than cobalt nitrate and hydrates thereof and, therefore, greater concentrations of cobalt can be achieved per unit volume of solvent where cobalt nitrate and hydrates thereof are used. However, cobalt nitrate is hydroscopic and therefore, upon deposition on a support material, a degree of metal dilution may occur on the surface as a result of moisture absorption. Upon calcination, there is substantial loss of volume due to the conversion of cobalt nitrate to cobalt oxide and the loss of water of crystallization, impacting the density of cobalt oxide crystallites per unit area on the surface of the support. This is believed to contribute to the lower maximum cobalt loadings that have historically been achieved through a single impregnation step where, for example, cobalt nitrate hexahydrate is employed as the cobalt source.

[0014] There remains a need for an improved process to produce a high cobalt loading Fischer-Tropsch synthesis catalyst in a single impregnation step, so that the reduced catalyst benefits from superior activity while retaining good physical properties, including bulk crush resistance and morphology. Furthermore, there remains a need for an alternative process for preparing a Fischer-Tropsch synthesis catalyst that can be used to improve conversion and selectivity for C5+ hydrocarbons in Fischer-Tropsch reactions, which hydrocarbons are of greater value for preparing C5+ hydrocarbon compositions. fuel.

[0015] Surprisingly it was found that a cobalt-containing Fischer-Tropsch catalyst having a high loading of cobalt metal, for example in excess of 15% by weight, can be prepared in a single impregnation step using a cobalt nitrate compound. cobalt hydroxide, or a hydrate thereof, as the source of cobalt. This compound has a higher proportion of cobalt (percentage by weight) and is less hydroscopic when compared to cobalt nitrate hexahydrate which has historically been the cobalt source of choice in the preparation of cobalt-containing Fischer-Tropsch catalysts. It was found that the Fischer-Tropsch catalyst obtained from using the cobalt hydroxide nitrate compound as the cobalt source has high conversion and good selectivity for C5+ hydrocarbons.

[0016] In a first aspect, the present invention provides a process for preparing a supported cobalt-containing Fischer-Tropsch synthesis catalyst, wherein said process comprises the steps of: (a) impregnating a support material with cobalt nitrate cobalt hydroxide, or a hydrate thereof, of formula (I) below to form an impregnated support material, [Co(OH)x(NO3)(2-x).yH2O] (I) where: 0<x< 2, and 0≤y≤6; (b) dry and calcine the impregnated support material.

[0017] In a second aspect, the present invention provides a process for preparing a Fischer-Tropsch synthesis catalyst that contains supported cobalt, wherein said process comprises the steps of: (i) impregnating a support material with cobalt nitrate cobalt hydroxide, or a hydrate thereof, of formula (I) below to form an impregnated support material, [Co(OH)x(NO3)(2-x).yH2O] (I) where: 0<x< 2, and 0≤y≤6; (ii) forming shaped particles from the impregnated support material; and (iii) drying and calcining the molded particles.

[0018] In other aspects, the invention provides a Fischer-Tropsch synthesis catalyst obtained and obtainable by the process defined above, as well as a process for converting a feed comprising a mixture of hydrogen and carbon monoxide gases into hydrocarbons that employs the catalyst of Fischer-Tropsch synthesis that contains cobalt.

[0019] Also provided are methods and uses of a Fischer-Tropsch synthesis catalyst containing cobalt as previously defined to increase the selectivity of a Fischer-Tropsch process for the production of C5+ hydrocarbons and/or increase conversion in a process by Fischer-Tropsch.

[0020] Also provided is the use of cobalt hydroxide nitrate of formula (I) as previously defined to increase the loading of elemental cobalt metal in the supported cobalt-containing Fischer-Tropsch synthesis catalyst that is obtainable in a single step of impregnation.

[0021] In yet a further aspect, the invention also provides a process for preparing cobalt hydroxide nitrate, or a hydrate thereof, of formula (I): [Co(OH)x(NO3)(2-x). yH2O] (I) where: 0<x<2; and 0≤y≤6, wherein said process comprises the step of reacting cobalt hydroxide with cobalt nitrate.

[0022] In the first aspect, the present invention provides a process for preparing a supported cobalt-containing Fischer-Tropsch synthesis catalyst, wherein said process comprises the steps of: (a) impregnating a support material with hydroxide nitrate cobalt to form an impregnated support material; and, (b) drying and calcining the impregnated support material.

[0023] In the second aspect, the present invention provides a process for preparing a supported cobalt-containing Fischer-Tropsch synthesis catalyst, wherein said process comprises the steps of: (i) impregnating a support material with hydroxide nitrate cobalt to form an impregnated support material; (ii) forming shaped particles from the impregnated support material; and (iii) drying and calcining the molded particles.

[0024] In this document, reference to cobalt hydroxide nitrate, unless otherwise specified, refers to a cobalt hydroxide nitrate compound, or a hydrate thereof, of formula (I): [Co( OH)x(NO3)(2-x).yH2O] (I) where: 0<x<2 0≤y≤6

[0025] In formula (I), it is not necessary for x and y to be integers and can often be numbers that are not integers.

[0026] In formula (I), x is greater than 0 and less than 2. In some or all embodiments, x is at most 1.5. In some or all embodiments, x is at most 1. In some or all embodiments, x is at least 0.1. In some or all embodiments, x is at least 0.2.

[0027] In formula (I), y is equal to or greater than 0 and equal to or less than 6.

[0028] In some or all embodiments, formula (I) can be written as formula (I'): [Cop(OH)q(NO3)r.zH2O] (I') where: p, x and y are integers greater than zero p = (q + r) / 2; and 0 ≤z ≤6p;

[0029] In some embodiments, p is 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0030] In preferred embodiments, p is an integer greater than 1, for example, from 2 to 10 or from 2 to 8.

[0031] In some embodiments, q is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20.

[0032] In preferred embodiments, q is an integer greater than 1, for example, from 2 to 20, from 2 to 16 or from 2 to 12.

[0033] In some embodiments, r is 1, 2, 3, 4 or 5.

[0034] In some embodiments, r is 1, 2 or 3 or r is 1 or 2.

[0035] In some embodiments, z is from 0.1 to 10, from 0.2 to 8, or from 0.25 to 5.

[0036] In some or all embodiments of the present invention, cobalt hydroxide nitrate is selected from Co(OH)(NO3)-H2O, Cθ2(0H)3(N03)-0.25H20 and Cθ7(0H )12(N03)2^5H20.

[0037] Without being bound by any particular theory, it is believed that the cobalt hydroxide nitrate described below in this document can accommodate a higher concentration of cobalt in the impregnation solution which, in turn, leads to a higher concentration of cobalt that can be deposited on the support material during impregnation. This is believed to be due to both the good solubility properties of cobalt hydroxide nitrate in the impregnation solution in combination with a higher weight percentage of cobalt in the compound compared to conventional cobalt sources such as cobalt nitrate hexahydrate. Furthermore, the lower hygroscopicity associated with cobalt(I) hydroxide nitrate compared to, for example, cobalt nitrate hexahydrate means that the compound of formula (I) can be more densely loaded into the bulk of the support material after impregnation. This allows an increased elemental cobalt loading on the supported catalyst to be obtained in a single impregnation step.

[0038] In this document, reference to “impregnation”, “impregnate”, “impregnated” or related terms is intended to refer to placing a support material, such as preformed molded particle/extrudate, in contact with a nitrate solution of cobalt hydroxide before drying, in order to achieve precipitation of cobalt hydroxide nitrate.

[0039] The impregnation solution may or may not be completely dissolved, depending on the concentration of cobalt hydroxide nitrate in the solvent. However, it has been found that it is not necessary for the impregnation to be carried out with a completely dissolved solution of cobalt hydroxide nitrate to ensure good dispersion of the cobalt hydroxide nitrate in the support material. The benefits of the present invention can also be noted in the in which case a partially undissolved cobalt hydroxide nitrate solution is used.

[0040] The support material used with the present invention is not particularly limited and can be selected from any silicates or refractory metal oxides known in the art or combinations thereof. Preferably, the support material is selected from the group consisting of silica, alumina, silica-alumina, ceria, gallium, zirconia, titania, magnesia, zinc oxide and mixtures thereof. More preferably, the support material is selected from titania and zinc oxide. Most preferably, the support material is selected from titania or mixtures containing titania. Titania can be selected from anatase titanium dioxide, rutile titanium dioxide, bookite titanium dioxide and combinations thereof. An example of a preferred titania support material particulate is powdered titania, for example, Degussa P25.

[0041] In this document, reference to a “preformed” or “molded particle” support is intended to mean a solid molded support (for example, by extrusion) suitable for impregnation, for example, by incipient moisture. The preformed support may, for example, have a geometrically symmetrical shape, examples of which include a cylinder, sphere, cylindrical dilobe, cylindrical trilobe, cylindrical quadrilobe or a hollow cylinder. Preferably, the preformed support has not undergone any impregnation step to introduce cobalt-containing compounds, or any other materials into it, and the impregnation step (a) is the only step in which a cobalt-containing compound is introduced into the support material. support before calcination in step (b). However, preformed supports that have undergone pretreatment can be used, for example, the introduction of promoters, dispersion aids, strength aids, binders and other additives. Pre-treatments of the pre-formed support may also include physical pre-treatments such as granulation prior to forming the molded solid support.

[0042] In this document, reference to a powder or granule of a support material is understood to refer to free-flowing particles of a support material or to particles of support material that undergo granulation to assume a particular range of shape (e.g. spherical) and size. In the context of the present invention, the powder or granulate is in a form that is suitable for impregnation by means of a cobalt hydroxide nitrate solution and subsequent extrusion. Preferably, the powder or granulate of a support material, when used as a starting material in the process of the invention, has not undergone any impregnation step to introduce the cobalt-containing compound, or any other materials into it. Alternatively or additionally, the impregnation step (a) in the first aspect of the invention, or step (i) in the second aspect of the invention, is preferably the only step in which a cobalt-containing compound is introduced into the support material prior to calcination in the step (b) in the first aspect of the invention, or step (iii) in the second aspect of the invention. However, powders or granules of a support material that has undergone pre-treatment can be used, in order to, for example, introduce promoters, dispersion aids, strength aids, binders and other additives. Pre-treatments of powders or granules of a support material may also include physical pre-treatments, such as sieving.

[0043] Preferred support materials are substantially free of metals or foreign elements that may adversely affect the catalytic activity of the system. Thus, preferred support materials are at least 95 wt % pure, more preferably at least 99 wt % pure. The impurities preferably amount to less than 1% by weight, more preferably less than 0.60% by weight and most preferably less than 0.30% by weight. The pore volume of the support is preferably greater than 0.20 ml/g and preferably greater than 0.5 ml/g. The average pore radius (before impregnation with cobalt hydroxide nitrate) of the support material is 10 to 500 Â, preferably 15 to 100 Â, more preferably 20 to 80 Â and most preferably 25 to 40 Â. The BET surface area is preferably 2 to 1,000 m2/g, preferably 10 to 600 m2/g, more preferably 15 to 100 m2/g and most preferably 30 to 60 m2/g.

[0044] The BET surface area, pore volume, pore size distribution, and mean pore radius can be determined from the nitrogen adsorption isotherm determined at 77 K using a volumetric adsorption analyzer static Micromeritics TRISTAR 3000. One procedure that can be used is an application of the methods of British Standard BS4359:Part 1:1984 'Recommendations for gas adsorption (BET) methods' and BS7591:Part 2:1992, 'Porosity and pore size distribution of materials' - Gas adsorption evaluation method. The resulting data can be reduced using the BET method (over the pressure range of 0.05 to 0.20 P/Po) and the Barrett, Joyner & Halenda (BJH) method (for powder diameters of 20 to 1,000 Å) in order to generate the surface area and pore size distribution, respectively.

[0045] Suitable references for the above data reduction methods are Brunauer, S, Emmett, P H, & Teller, E, J. Amer. Chem. Soc. 60, 309, (1938) and Barrett, E P, Joyner, L G & Halenda P P, J. Am Chem. Soc., 1951 73 373380.

[0046] In preferred embodiments, where a support material powder is employed as the starting material, the powder has a median particle size diameter (d50) less than 50 μm, preferably less than 25 μm. The particle size diameter (d50) can be suitably determined by means of a particle size analyzer (e.g. Microtrac S3500 particle size analyzer).

[0047] In preferred embodiments, when the support material is in the form of a granulate, the median particle size diameter (d50) is in the range of 300 to 600 μm.

[0048] When the support material is in the form of a powder or granule, the impregnation step may form a powder or granule of the impregnated support. In the second aspect of the invention, such an impregnated carrier powder or granulate can then be formed into a molded particle in step (ii), prior to drying and calcining in step (iii). In an embodiment of the second aspect of the present invention, the impregnated support powder or granulate is extruded to form an extrudate before drying and calcining in step (iii).

[0049] Alternatively, when a support material is in the form of a powder or granule, the impregnation step may form a powder or granule of the support impregnated in step (a) according to the first aspect of the invention, this powder or granule of impregnated support may undergo drying and calcination in step (b) to form a calcined powder or granulate, after which the calcined powder or granulate may then be formed into a shaped particle, for example, by extrusion to form an extrudate.

[0050] In embodiments where the support material is in the form of a molded particle, for example an extrudate, the impregnation step (a) may form an impregnated molded particle, for example an impregnated extrudate, before drying and calcining in the step (b) according to the first aspect of the invention.

[0051] Impregnation of the support material with the cobalt hydroxide nitrate compound according to the present invention can be achieved by any suitable method, which is understood by those skilled in the art, for example, by vacuum impregnation, incipient humidity or immersion in excess liquid. The solvent of the impregnation solution can be either an aqueous solvent or a non-aqueous organic solvent. Suitable non-aqueous organic solvents include, for example, alcohols (e.g. methanol, ethanol and/or propanol), ketones (e.g. acetone), hydrocarbons and liquid paraffinic ethers. Alternatively, aqueous organic solvents, for example, an aqueous alcoholic solvent, may be employed. Preferably, the solvent of the impregnation solution is water and, in some or all embodiments, the support material is impregnated with an aqueous solution or suspension of cobalt hydroxide nitrate.

[0052] The concentration of cobalt hydroxide nitrate in the impregnation solution is not particularly limited. When a powder or granulate of a support material is impregnated and immediately followed by an extrusion step, the amount of impregnation solution is preferably suitable to form an extrudable paste. In some or all embodiments, the concentration of the impregnation solution is sufficient to provide greater than or equal to 15 wt% cobalt filler, preferably 15 wt% to 20 wt% cobalt filler, on an elemental basis. on the supported synthesis catalyst based on the total weight of the supported synthesis catalyst. A suitable concentration of the cobalt-containing compound is, for example, 0.1 to 15 mol/liter.

[0053] Impregnation of the support material according to the present invention also involves sufficient drying of the impregnation solution in order to effect precipitation of the cobalt hydroxide nitrate on the support material and preferably also in order to remove the bound solvent from the impregnation solution (e.g. water). In this way, drying does not cause the decomposition of the cobalt hydroxide nitrate, or otherwise, a change in the oxidation state of the cobalt. As will be noted, in embodiments in which an extrusion is performed, complete drying and removal of the solvent (e.g., bound solvent) from the impregnation solution may occur after extrusion. Drying according to the present invention is suitably carried out at temperatures of 50°C to 150°C, preferably 75°C to 125°C. Suitable drying times are 5 minutes to 24 hours. Drying may suitably be conducted by any means known in the art, suitable examples including drying in a drying oven or in a box furnace, for example, under the flow of an inert gas at an elevated temperature.

[0054] When a preformed or extruded support is impregnated in accordance with the present invention, it will be understood that the support may come into contact with the impregnation solution by any suitable means which include, for example, vacuum impregnation, incipient moisture or immersion in excess liquid.

[0055] When a powder or granule of support material is impregnated, the powder or granule may be mixed with the impregnation solution by any suitable means of which those skilled in the art understand, such as by adding the powder or granule to a container of the carrier material. impregnation solution, or vice versa, and stirring the resulting solution. When an extrusion step immediately follows the impregnation of a powder or granulate, the mixture of the powder or granule and the impregnation solution may be further processed if they are not already in a form that is suitable for extrusion. For example, the mixture may be crushed to reduce the presence of larger particles that may not be readily extruded or, otherwise, their presence impairs the physical properties of the resulting extrudate. Milling typically involves the formation of a paste that is suitable for molding through extrusion. Any grinding or kneading apparatus known to those skilled in the art can be used for grinding in the context of the present invention. For example, a pestle and mortar may be used appropriately in some applications, while a de Vinci mixer or Simpson grinder may be appropriately employed. Grinding is carried out for a period sufficient to achieve the desired consistency, in some or all embodiments this may be for a period of 3 to 90 minutes, such as for a period of 5 minutes to 30 minutes. Grinding can be carried out adequately over a range of temperatures, including ambient temperatures. A preferred temperature range for grinding is 15°C to 50°C. Grinding can be carried out adequately at ambient pressures. The solvent content of the mixture before extrusion can be adjusted if necessary, for example with the solvent used for impregnation, in order to achieve an extrudable paste. As set forth hereinbefore, it will be appreciated that complete removal of the bound solvent from the impregnation solution can be conducted to effect complete precipitation after extrusion.

[0056] As part of an extrusion step, a shaped extrudate can be formed. The extrudate may, for example, have a geometrically symmetrical shape, examples of which include a cylinder, sphere, cylindrical dilobe, cylindrical trilobe, cylindrical quadrilobe or a hollow cylinder.

[0057] In embodiments in which a calcination step is carried out on an impregnated powder or granulate, thereby completely removing the solvent from the impregnation solution, the calcined powder or granule can also be further processed in order to form a mixture that is suitable to form shaped particles, such as by extrusion. For example, an extrudable paste can be formed by combining the calcined powder or granulate with a suitable solvent, for example, a solvent used for impregnation, preferably an aqueous solvent and milled as previously described.

[0058] According to the process of the present invention, the preparation of the supported Fischer-Tropsch synthesis catalyst involves a calcination step. As discussed in this document previously, calcination is necessary to convert the cobalt hydroxide nitrate that has been impregnated into the support material into a cobalt oxide. Thus, calcination causes thermal decomposition of cobalt hydroxide nitrate and not just the removal of the bound solvent from an impregnation solution, as in the case of drying according to the present disclosure.

[0059] Calcination can be carried out by any method known to those skilled in the art, for example, in a fluidized bed or rotary kiln at a temperature suitably in the range of 150 °C to 700 °C. In embodiments, the calcination in step (b) of the first aspect of the invention, or step (iii) of the second aspect of the invention, is conducted at a temperature of at least 250 °C, preferably 275 °C to 500 °C. Calcination can be conducted as part of an integrated process in which calcination and reductive activation of the synthesis catalyst to generate a reduced synthesis catalyst are carried out in the same reactor.

[0060] It has been found that the process of the present invention is particularly suitable for increasing the cobalt loading on a supported Fischer-Tropsch synthesis catalyst. The amount of cobalt, on an elemental basis, in the supported synthesis catalyst obtained in the impregnation step of the present invention is preferably greater than or equal to 10% by weight, 11% by weight, 12% by weight, 13% by weight, 14 % by weight, 15% by weight, 16% by weight, 17% by weight or 18% by weight, based on the total weight of the synthesis catalyst. In some or all embodiments of the present invention, the range of cobalt concentrations, on an elemental basis, for the synthesis catalyst obtained in accordance with the process of the present invention is 15 to 20% by weight, based on the total weight. of the synthesis catalyst. As will be understood by those skilled in the art, the amount of cobalt, on an elemental basis, in the synthesis catalyst can be readily determined by X-ray fluorescence (XRF) techniques. Furthermore, as will be understood by those skilled in the art, identification of the cobalt-containing compound or other types of compound deposited on or comprising the support material can be accomplished by X-ray diffraction (XRD) techniques, in particular X-ray diffraction techniques. powder X-ray (PXRD).

[0061] The supported Fischer-Tropsch synthesis catalyst prepared according to the process of the present invention may additionally comprise one or more promoters, dispersion aids, strength aids and/or binders. Promoters can be added to promote the reduction of a cobalt oxide to cobalt metal, preferably at lower temperatures. In some or all embodiments of the present invention, one or more promoters are selected from a list consisting of ruthenium, palladium, platinum, rhodium, rhenium, manganese, chromium, nickel, iron, molybdenum, tungsten, zirconium, gallium, thorium , lanthanum, cerium and mixtures thereof. Preferably the promoter is manganese. When a promoter is present, the one or more promoters are typically used in a total amount of 0.1 wt % to 3 wt %, on an elemental basis, based on the total weight of the supported synthesis catalyst.

[0062] The addition of promoters, dispersion aids, strength aids or binders can be integrated at various stages of the process, in accordance with the present invention. Preferably, the promoter, dispersion aids, strength aids and/or binders are introduced during the impregnation step.

[0063] The process of the present invention allows the preparation of a supported Fischer-Tropsch synthesis catalyst that has a high cobalt loading, for example, at least 15% by weight. Consequently, a reduced synthesis catalyst obtained through the process of the present invention can have proportionally high activity in Fischer-Tropsch reactions.

[0064] The present invention, therefore, also provides a Fischer-Tropsch catalyst that contains cobalt obtained or capable of being obtained by the process of the present invention.

[0065] The Fischer-Tropsch synthesis catalyst prepared in accordance with the present invention can be conveniently converted into a reduced Fischer-Tropsch synthesis catalyst by reductive activation by any known means, which is understood by those skilled in the art, which has the ability to convert cobalt oxide to active cobalt metal. Thus, in one embodiment, the process of the invention further comprises reducing the cobalt-containing Fischer-Tropsch synthesis catalyst obtained to form a reduced Fischer-Tropsch synthesis catalyst.

[0066] The step of forming a reduced Fischer-Tropsch synthesis catalyst can be carried out in batch or continuously in a fixed bed reactor, fluidized bed reactor or slurry phase reactor. The reduced synthesis catalyst formed after the reductive activation process is useful in the heterogeneously catalyzed production of hydrocarbons from synthesis gas by Fischer-Tropsch synthesis, for example, in the production of a diesel or aviation fuel or precursor thereof. The Fischer-Tropsch synthesis of hydrocarbons from synthesis gas can be represented by Equation 1: mCO + (2m+l)H2 ^ mH2O + CmH2m+2 Equation 1

[0067] As previously discussed, it was surprisingly found that the process of the present invention produces a Fischer-Tropsch catalyst that exhibits high C5+ hydrocarbon selectivity. Furthermore, at least in some embodiments, it has been found that the catalytic activity is also superior.

[0068] In another aspect, there is provided a method for increasing the selectivity of a Fischer-Tropsch process for the production of C5+ hydrocarbons and/or increasing conversion in a Fischer-Tropsch process, wherein said method comprises step of providing a Fischer-Tropsch synthesis catalyst containing cobalt, as defined herein prior to a Fischer-Tropsch process.

[0069] The present invention also provides a use of a Fischer-Tropsch synthesis catalyst containing cobalt as defined hereinbefore for producing C5+ hydrocarbons and/or increasing conversion in a Fischer-Tropsch process.

[0070] In a further aspect, the present invention provides a process for converting a feed comprising a mixture of hydrogen and carbon monoxide gases, preferably in the form of a synthesis gas mixture, into hydrocarbons, wherein the process comprises placing a mixture of hydrogen and carbon monoxide, preferably in the form of a synthesis gas mixture, in contact with a Fischer-Tropsch catalyst containing cobalt, as defined previously in this document.

[0071] In the Fischer-Tropsch reaction described above, the volume ratio between hydrogen and carbon monoxide (H2:CO) in the gaseous reactant mixture is preferably in the range of 0.5: 1 to 5: 1, more preferably 1 :1 to 3:1, for example, in the range of 1.6:1 to 2.2:1. The gaseous reactant stream may also comprise other gaseous components, such as nitrogen, carbon dioxide, water, methane and other light saturated and/or unsaturated hydrocarbons, each preferably being present in a concentration of less than 30% by volume. The temperature of the Fischer-Tropsch reaction is preferably in the range of 100 to 400 ° C, more preferably 150 to 350 ° C, and most preferably 150 to 250 ° C. The pressure is preferably in the range of 0.1 to 10 MPa (from 1 to 100 bar), more preferably from 0.5 to 7.5 MPa (5 to 75 bar) and most preferably from 1.0 to 5.0 MPa (from 10 to 50 bar).

[0072] Cobalt hydroxide nitrate can be prepared by any suitable method of which the skilled person is aware. For example, cobalt hydroxide nitrate can be prepared by controlled hydrolysis of Co(NO3)2 in sodium hydroxide solution, as described in L Markov et al., Thermochim Acta, 1986, 106, pages 283 to 292. Alternatively , cobalt hydroxide nitrate can be prepared using NaHCO3 and urea as the hydrolysis reagents, as described in K. Petrov et al., Journal of Solid State Chemistry, 1992, 101, pages 145 to 153. However, the present invention also provides an additional process for preparing cobalt hydroxide nitrate as described below.

[0073] Thus, in another aspect, the invention provides a process for preparing cobalt hydroxide nitrate, or a hydrate thereof, as previously described. This process for preparing cobalt hydroxide nitrate, or a hydrate thereof, comprises the step of reacting cobalt hydroxide with cobalt nitrate. The reaction is suitably carried out in solution, preferably aqueous solution (e.g. in deionized water) and above room temperature.

[0074] Preferably, the reaction is carried out at a temperature of 40 °C to 80 °C, more preferably 50 °C to 70 °C, most preferably 55 °C to 65 °C.

[0075] In some embodiments, cobalt hydroxide and cobalt nitrate are placed in solution with stirring (e.g., vigorous stirring) for a suitable period of time so that the reaction continues. For example, cobalt hydroxide and cobalt nitrate can be placed in solution for at least 10 minutes, e.g. 10 minutes to 2 hours, such as 30 to 90 minutes, e.g. 50 to 75 minutes. The progress of the reaction can be conveniently monitored by observing a color change from scarlet red to purple.

[0076] Preferably, the molar ratio of cobalt nitrate to cobalt hydroxide in the preparation of cobalt hydroxide nitrate is 1:1 to 5:1, more preferably in the range of 2:1 to 4:1. In some cases , cobalt nitrate can be in the form of cobalt nitrate hexahydrate.

[0077] In some embodiments, cobalt hydroxide and cobalt nitrate react in the presence of nitric acid. Preferably, the molar ratio of cobalt hydroxide to nitric acid in the preparation in these embodiments is 1:1 to 5:1, more preferably 2:1 to 5:1.

[0078] In yet a further aspect, the present invention also provides a use of the cobalt hydroxide nitrate of the formula for increasing the loading of elemental cobalt metal in the supported cobalt-containing Fischer-Tropsch synthesis catalyst that is obtainable in a single impregnation step.

[0079] The invention will now be further described by reference to the following examples, which are illustrative only. In the examples, CO conversion is defined as moles of CO used/moles of CO fed x 100, and carbon selectivity as moles of CO assigned to a particular product/mols of CO converted x 100. Unless otherwise stated , the temperatures cited in the examples are applied temperatures and not catalyst/bed temperatures. Unless otherwise stated, the pressures named in the examples are absolute pressures.

[0080] The present invention will now be illustrated by means of the following examples and with reference to the following figure:

[0081] FIGURE 1: Results of the PXRD pattern (top) and phase identification (base) of an extrudate prepared by the process of the invention.

Examples Example 1 - preparation of cobalt hydroxide nitrate from cobalt hydroxide and cobalt nitrate

[0082] A predetermined amount of deionized water was weighed, the desired amount of cobalt nitrate hexahydrate (Co (NO3)2*6H2O) was added and the solids dissolved under vigorous stirring at 60 °C. Cobalt hydroxide (Co(OH)2) was added to the solution in such an amount as to achieve a molar ratio of Co(OH)2:Co(NO3)2^6H2O of 1:3. The solution was maintained at a temperature temperature of 60 °C with stirring for 60 min, whereby the color of the solution changed from scarlet red to purple.

Example 2 - preparation of cobalt hydroxide nitrate from cobalt hydroxide, cobalt nitrate and nitric acid

[0083] A predetermined amount of deionized water was weighed and the desired amount of nitric acid was added into a glass reactor associated with a heater and adjustable stirring system. Cobalt hydroxide (Co(OH)2) was added to the solution in an amount to achieve a HNO3 : Co(OH)2 molar ratio of 1 : 2 and the solids were dissolved under vigorous stirring. Cobalt nitrate hexahydrate (Co(NO3)2*6H2O) was then added to the solution to achieve a molar ratio of Co(NO3)2^6H2O : Co(OH)2 of 1 : 1. The resulting solution was heated at 60 °C and maintained at 60 °C with stirring for 60 min, whereby the color of the solution changed from scarlet red to purple.

Example 3 - preparation of catalyst extrudates

[0084] An appropriate amount of titania powder (Evonik Aeroxide P25) was weighed in order to achieve a weight ratio of elemental cobalt (Co) present in the prepared solution or in Example 1 or 2 to titania to achieve a weight percentage of cobalt in the final extrudate of 20% by weight. The solution prepared in either Example 1 or 2 was slowly added to the titania with stirring, in order to reduce the volume of the powder. The mixture was then transferred to a mechanical mixer (Vinci mixer or Simpson grinder) and kneaded into an extrudable paste. The moisture content of the paste was adjusted with water as necessary to form an extrudable paste. The mixture was then extruded into green extrudates with the desired geometry. The extrudates were dried and calcined using the following profiles: 60 °C for 5 h, 120 °C for 5 h, 300 °C for 2 h; rate of increase between them is 2.0 °C/min.

[0085] Figure 1 shows the PXRD pattern of extrudates dried at 120 °C. Lines attributed to hydrated cobalt hydroxide nitrate are clearly discernible, as are several titanium oxides (anatase and rutile) and hydrated cobalt nitrate. The cobalt hydroxide (Co(OH)2) used in the synthesis is not observed, suggesting the complete conversion of this compound.

Example 4 - use of catalyst extrudates in a Fischer-Tropsch synthesis process

[0086] The cobalt species in the catalyst extrudates were completely reduced to cobalt metal using hydrogen prior to the reaction. Gas phase products were analyzed using in-line GC equipment with an FID. Liquid products were collected in cryogenic containers and analyzed offline. The operating conditions and reaction results are listed as follows:

Comparative Example 1 - preparation of catalyst extrudates using conventional cobalt nitrate hexahydrate as the cobalt source

[0087] A predetermined amount of cobalt nitrate hexahydrate (Co(NO3)2*6H2O) was weighed and dissolved in a minimum amount to form a clear solution at room temperature. A predetermined amount of powdered titania (Evonik Aeroxide P25) was added to this solution. The mixture was then transferred to a mechanical mixer (Vinci mixer or Simpson grinder) and kneaded into a paste. The moisture content of the paste was adjusted with water as necessary to form an extrudable paste. The mixture was then extruded into green extrudates with the desired geometry. The extrudates were dried and calcined using the following profiles: 60 °C for 5 h, 120 °C for 5 h, 300 °C for 2 h; rate of increase between them is 2.0 °C/min. The resulting catalyst had 10 wt% Co metal, which represents the maximum Co loading achieved by conventional methods.

Comparative Example 2 - use of catalyst extrudates in a Fischer-Tropsch synthesis process

[0088] The cobalt species in the catalyst extrudates were completely reduced to cobalt metal using hydrogen prior to the reaction. Gas phase products were analyzed using in-line GC equipment with an FID. Liquid products were collected in cryogenic containers and analyzed offline. The operating conditions and reaction results are listed as follows:

[0089] A Fischer-Tropsch catalyst was not prepared using Co(OH)2 because of its poor solubility in water.

[0090] The above results demonstrate the usefulness of the catalyst according to the present invention in the Fischer-Tropsch process. When comparing the performance data of the catalyst with 10 wt% Co loading formed using conventional methods (Comparative Example 2) and the catalyst with 20 wt% Co loading prepared in accordance with the present invention (Example 4 ), it is clear that the catalyst prepared in the present invention is superior. Example 4 shows an average CO conversion of 64.29% at 192°C, while the catalyst prepared in Comparative Example 2 only achieves a CO conversion of 63.52% at 199.5°C. The lower reaction temperature required in Example 4 when compared to Comparative Example 2 results in lower methane selectivity (7.02% vs. 8.33%) and higher selectivity for C5+ hydrocarbons (86.76% vs. 84.13 %), which is highly desirable in a Fischer-Tropsch process.

Claims (29)

1. Process for preparing a Fischer-Tropsch synthesis catalyst containing cobalt supported on titania, said process being characterized by comprising the steps of: (a) impregnating a titania support material with cobalt hydroxide nitrate, or a hydrate thereof, of formula (I) below to form an impregnated support material, [Co(OH)x(NO3)(2-x).yH2O] (I) where: 0<x<2 0≤y≤6 (b) dry and calcine the impregnated support material. 2. Process for preparing a Fischer-Tropsch synthesis catalyst containing supported cobalt, said process being characterized by comprising the steps of: (i) impregnating a support material with cobalt hydroxide nitrate, or a hydrate thereof, of formula (I) below to form an impregnated support material, [Co(OH)x(NO3)(2-x).yH2O] (I) where: 0<x<2, and 0<y<6; (ii) forming shaped particles from the impregnated support material; and (iii) drying and calcining the molded particles. 3. Process, according to claim 1 or 2, characterized by the fact that x is at most 1.5, preferably at most 1. 4. Process, according to claim 2, characterized by the fact that, in step (ii), the molded particles are formed by extrusion. 5. Process according to claim 1, characterized by the fact that the support material is in the form of a powder or granule and the impregnation step (a) forms an impregnated support powder or granule and the calcination in step ( b) forms a calcined powder or granulate, the process further comprising extruding the calcined powder or granulate to form an extrudate. 6. Process according to claim 4 or 5, characterized by the fact that the support material is in the form of a powder having a median particle size diameter (d50) less than 50 μm, preferably less than 25 μm ; or wherein the support material is in the form of a granulate having a particle size median diameter (d50) of 300 to 600 μm, as determined by means of a particle size analyzer. 7. Process according to any one of claims 1 to 6, characterized in that the average pore radius of the support material before impregnation is in the range of 10 to 500Â, preferably 15 to 100Â, more preferably 20 to 80 Â and most preferably 25 to 40 Â, as determined by measuring the BET surface area. 8. Process according to claim 1, characterized by the fact that the support material is in the form of an extrudate and the impregnation step (a) forms an impregnated extrudate before step (b). 9. Process according to any one of claims 1 to 8, characterized by the fact that the support material has not been previously impregnated with a cobalt-containing compound and the impregnation step of the process is the only step in which the compound containing Contains cobalt is introduced into the support material before calcination. 10. Process according to any one of claims 1 to 9, characterized by the fact that the impregnation step produces a synthesis catalyst that contains more than or equal to 10% by weight of cobalt, preferably more than or equal to 15% by weight. weight of cobalt, such as from 15 wt% to 20 wt% cobalt, on an elemental basis, based on the total weight of the supported synthesis catalyst. 11. Process according to any one of claims 1 to 10, characterized in that the support material is impregnated with an aqueous solution or suspension of cobalt hydroxide nitrate. 12. Process according to any one of the preceding claims, characterized in that the support material comprises a material selected from silica, alumina, silica-alumina, ceria, gallium, zirconia, titania, magnesia, zinc oxide and mixtures thereof, preferably titania or mixtures containing titania. 13. Process according to claim 12, characterized in that the support material is a titania and selected from anatase titanium dioxide, rutile titanium dioxide, brookite titanium dioxide and combinations thereof. 14. Process according to any one of claims 1 to 13, characterized in that the cobalt-containing Fischer-Tropsch synthesis catalyst obtained comprises one or more promoters, dispersion aids, strength aids and/or binders, preferably wherein the one or more promoters, dispersion aids, strength aids and/or binders, or precursors thereof, is/are introduced during the impregnation step. 15. Process according to claim 14, characterized by the fact that the cobalt-containing Fischer-Tropsch synthesis catalyst obtained comprises one or more promoters selected from the group consisting of ruthenium, palladium, platinum, rhodium, rhenium , manganese, chromium, nickel, iron, molybdenum, tungsten, zirconium, gallium, thorium, lanthanum, cerium and mixtures thereof; preferably wherein the promoter is manganese. 16. Process according to claim 15, characterized by the fact that the one or more promoters are present in the Fischer-Tropsch synthesis catalyst containing cobalt obtained in an amount of 0.1% by weight to 3% by weight , on an elemental basis, based on the total weight of the supported synthesis catalyst. 17. Process according to any of the preceding claims, characterized by the fact that calcination is carried out at a temperature of at least 250 °C, preferably 275 °C to 500 °C. 18. Process according to any one of the preceding claims, characterized in that it further comprises reducing the cobalt-containing Fischer-Tropsch synthesis catalyst obtained to form a reduced Fischer-Tropsch synthesis catalyst. 19. Process according to any one of claims 1 to 18, characterized by the fact that no Co(OH)2 is observed after drying as measured by powder X-ray diffraction. 20. Process according to any one of claims 1 to 19, characterized in that cobalt hydroxide nitrate, or a hydrate thereof, is prepared by reacting cobalt hydroxide with cobalt nitrate. 21. Process according to claim 20, characterized by the fact that the reaction is carried out for at least 10 minutes before impregnation. 22. Process according to any one of claims 1 to 21, characterized in that the impregnation of the titania support material with cobalt hydroxide nitrate or hydrate thereof comprises providing a purple solution of cobalt hydroxide nitrate cobalt or a hydrate thereof; then contacting the purple solution with the titania holder to impregnate it. 23. Process according to any one of claims 1 to 22, characterized in that the provision of the purple cobalt hydroxide nitrate solution or the hydrate thereof comprises the reaction of cobalt hydroxide with cobalt nitrate in aqueous solution , for at least ten minutes, before the purple solution comes into contact with the titania support. 24. Process for preparing cobalt hydroxide nitrate, or a hydrate thereof, of formula (I): [Co(OH)x(NO3)(2-x).yH2O] (I) where: 0<x<2 , and 0≤y≤6; said process being characterized by comprising the step of reacting cobalt hydroxide with cobalt nitrate. 25. Process according to claim 24, characterized by the fact that the cobalt nitrate is in the form of cobalt nitrate hexahydrate. 26. Process according to claim 24 or 25, characterized by the fact that cobalt hydroxide reacts with cobalt nitrate in solution. 27. Process according to any one of claims 24 to 26, characterized in that cobalt hydroxide and cobalt nitrate react in the presence of nitric acid. 28. Process according to any one of claims 24 to 27, characterized by the fact that the molar ratio of cobalt nitrate to cobalt hydroxide is 1:1 to 5:1, preferably 2:1 to 4:1 . 29. Process for converting a feed comprising a mixture of hydrogen and carbon monoxide gases, preferably in the form of a synthesis gas mixture, into hydrocarbons, the process being characterized by comprising placing a mixture of hydrogen and carbon monoxide, preferably in the form of a synthesis gas mixture, in contact with a Fischer-Tropsch catalyst containing cobalt, as defined in claims 1 to 23.