FR3071749A1 - CATALYST COMPRISING AN NI4W ALLOY AND ITS USE IN FISCHER-TROPSCH SYNTHESIS - Google Patents

Abstract

The invention relates to a catalyst containing a nickel-tungsten Ni4W alloy deposited on a support comprising alumina, silica or silica-alumina, said support optionally containing a mixed oxide phase containing cobalt and / or nickel. The invention also relates to its use in the field of Fischer-Tropsch synthesis methods.

Description

The invention relates to a catalyst containing a nickel-tungsten alloy Ni ₄ W, deposited on a support comprising alumina, silica or silica-alumina, said support optionally containing a mixed oxide phase containing cobalt and / or nickel. The invention also relates to its use in the field of Fischer-Tropsch synthesis methods.

The present invention relates to the field of FischerTropsch synthesis processes which make it possible to obtain a wide range of hydrocarbon cuts from the CO + H ₂ mixture, commonly called synthesis gas or syngas.

The simplified stoichiometric equation (limited in the equation below to the formation of alkanes) of the Fischer-Tropsch synthesis is written:

n CO + (2n + 1) H ₂ -> C _n H _{2n + 2} + n H ₂ O

The catalysts used in Fischer-Tropsch synthesis are most often supported catalysts based on alumina, silica or silica-alumina or combinations of these supports, the active phase mainly consisting of iron (Fe) or cobalt ( Co) optionally doped with a noble metal such as platinum (Pt), rhodium (Rh) or ruthenium (Ru).

The cobalt element is particularly chosen for its selectivity towards the growth of long carbon chains. However, this is an element classified as critical for the European Union on the one hand and whose impact on the cost of the final catalyst is significant. The replacement of cobalt, partial or total, has been studied in the literature, with iron for example (Angew. Chem. Int. Ed., 2013, 52, p.4397-4401), nickel (Chemical Engineering & Processing: Process Intensification, 2017, 119, 44-61) or molybdenum (Catalysis Today, 2008, 131, p.255-261).

The present invention seeks to provide a Fischer-Tropsch catalyst by replacing the active phase of cobalt with another active phase, in particular by an alloy based on nickel and tungsten.

Patent application WO 2012/107844 claims a catalyst based on cobalt, iron, nickel or ruthenium as active phase on an oxide support containing tungsten, the tungsten not being contained in the active phase.

Alloys making it possible to obtain catalytic performances at least equivalent to cobalt catalysts do not seem to be disclosed in the state of the art, with the exception of alloys with noble metals such as ruthenium (Green Chem, 2011, 13 , p.1950-1959).

summary

The invention relates to a catalyst containing a nickel-tungsten alloy Ni ₄ W, deposited on a support comprising alumina, silica or silica-alumina, said support optionally containing a mixed oxide phase containing cobalt and / or nickel. The invention also relates to its use in the field of Fischer-Tropsch synthesis methods.

The Applicant has in fact found that the use of a catalyst containing the nickel-tungsten alloy Ni ₄ W, deposited on a support comprising alumina, silica or silica-alumina, said support optionally containing a mixed oxide phase containing cobalt and / or nickel, made it possible to obtain a catalyst for the Fischer-Tropsch synthesis showing high catalytic performance with a reduced production cost.

Indeed, the catalyst according to the invention shows an activity and a selectivity at least equivalent or even superior to catalysts containing an active phase based on cobalt.

According to a variant, the nickel content is between 1 and 30% by weight, expressed as a metallic element relative to the total weight of the catalyst.

According to a variant, the tungsten content is between 0.1% and 20% by weight, expressed as a metallic element relative to the total weight of the catalyst.

According to a variant, said support also contains a mixed oxide phase containing cobalt and / or nickel. According to this variant, the content of the mixed oxide phase in the support is between 0.1 and 45% by weight relative to the weight of the support.

According to a variant, the mixed oxide phase comprises an aluminate of formula

C0AI2O4 or N1AI2O4 in the case of a support based on alumina or silica-alumina.

According to a variant, the mixed oxide phase comprises a silicate of formula Co2SiC> 4 or Ni ₂ SiO ₄ in the case of a support based on silica or silica-alumina.

According to a variant, the silica content of said support is between 0.5% by weight to 30% by weight relative to the weight of the support before the formation of the mixed oxide phase when the support is a silica-alumina.

According to a variant, the catalyst also comprises an element chosen from groups VIII, IA, IB, IIA, IIB, NIA, IIIB and VA.

The invention also relates to a process for preparing the catalyst comprising the following steps:

a) a step of bringing the support into contact comprising alumina, silica or silica-alumina with at least one solution containing at least one precursor of nickel and tungsten,

b) a drying step at a temperature below 200 ° C,

c) a reduction step at a temperature between 410 and 900 ° C.

According to a variant, the reduction step c) is carried out at a temperature between 550 and 800 ° C.

According to a variant, before the contacting step a), a step of bringing the support into contact with at least one solution containing at least one cobalt and / or nickel precursor is carried out, then dried and calcined at a temperature between 700 and 1200 ° C, so as to obtain a mixed oxide phase containing cobalt and / or nickel in the support.

According to a variant, after the drying step b), a calcination step is carried out at a temperature between 200 and 550 ° C., under an inert atmosphere or under an atmosphere containing oxygen.

The invention also relates to a Fischer-Tropsch process for the synthesis of hydrocarbons in which the catalyst according to the invention is brought into contact with a charge comprising synthesis gas under a total pressure of between 0.1 and 15 MPa, under a temperature between 150 and 350 ° C, and at an hourly volume speed between 100 and 20,000 volumes of synthesis gas per volume of catalyst and per hour with a H ₂ / CO molar ratio of synthesis gas between 0.5 and 4 .

Detailed description of the invention

Catalyst

In the following, groups of chemical elements are given according to CAS Classification (CRC Handbook of Chemistry and Physics, CRC press publisher, editor DR Lide, 81 ^th Edition, 2000-2001). For example, group VIII according to the CAS classification corresponds to the metals in columns 8, 9 and 10 according to the new lUPAC classification.

The textural and structural properties of the support and of the catalyst described below are determined by the characterization methods known to those skilled in the art. The total pore volume and the pore distribution are determined in the present invention by nitrogen porosimetry as described in the work "Adsorption by powders and porous solids. Principles, methodology and applications >> written by F. Rouquérol, J. Rouquérol and K. Sing, Academie Press, 1999.

By specific surface is meant the BET specific surface (SBET in m ² / g) determined by nitrogen adsorption in accordance with standard ASTM D 3663-78 established from the BRUNAUER-EMMETT-TELLER method described in the periodical The Journal of American Society, 1938, 60, 309.

The crystalline phases of the catalyst according to the invention are characterized by diagrams which have been recorded on a diffractometer (X'PERT'Pro from PANalytical) in Bragg-Bentano geometry, equipped with a copper tube (1.54 Å), a proportional counter and slots with variable openings as a function of 2Θ. The irradiated sample surface was 10x1 Omm, the sampling step of 0.05 ° 2θ, the time in steps of 5 to 15s. After recording, the intensities were corrected and transformed into intensities at constant irradiated volume. The measurement of the positions, relative intensities and widths of the diffracted lines were determined by complete modeling of the diffractograms using symmetric pseudo-Voigt type analytical functions, with a Gaussian-Lorentzian ratio set at 0.5.

The presence of the bimetallic phase in the form of an Ni ₄ W alloy can be confirmed by X-ray diffraction, by comparing the lines observed with those appearing in the ICDD file for the Ni ₄ W phase (PDF # 03-065-2673) . The positions of the Ni ₄ W lines are shown in the table below, only the lines of relative intensities “l / l ₀ ” greater than 10 and of interreticular distances “d >> greater than 1.35 Å (or less at a 2Θ angle of 70 °) have been reported. The column “hkl” corresponds to the Miller indices.

PDF 03-065-2673 (Ni ₄ W) d (A) 2Θ l / lo (%) hkl 4.05 21.92 13.2 110 3.02 29.56 16.1 101 2.08 43.51 100.0 211 1.81 50.32 34.4 130 1.78 51.39 15.1 002

The nickel content of said catalyst is between 1 and 30% by weight, preferably between 2 and 20% by weight, expressed as a metallic element relative to the total weight of the catalyst. The tungsten content is between 0.1% and 20% by weight, preferably between 1% and 15% by weight, expressed as a metallic element relative to the total weight of the catalyst.

When the support comprises alumina, it contains more than 45% by weight of alumina relative to the weight of the support and, preferably, it contains only alumina. The alumina can be present in a crystallographic form such as gamma, delta, theta, alpha alumina, taken alone or as a mixture.

In another preferred case, the support comprises silica. In this case, it contains more than 45% by weight of silica relative to the weight of the support and, preferably, it contains only silica. Sources of silicon are well known to those skilled in the art.

In another preferred case, the support comprises a silica-alumina. A support comprising a silica-alumina is understood to mean a support in which the silicon and the aluminum is in the form of agglomerates of silica or alumina respectively, of amorphous aluminosilicate or any other mixed phase containing silicon and aluminum, it being understood that the support is not mesostructured. Preferably, the alumina and the silica are present in the form of a mixture of SiO2-AI ₂ O3 oxides. The silica content in the silica-alumina support varies from 0.5% by weight to 30% by weight, preferably from 1% by weight to 25% by weight, and even more preferably from 1.5 to 20% by weight relative to the weight of the support.

According to a preferred variant, the support consists of alumina, silica or silicone alumina, and in a particularly preferred manner the support consists of alumina silica.

The specific surface of the support is generally between 50 m ² / g and 500 m ² / g, preferably between 100 m ² / g and 300 m ² / g, more preferably between 150 m ² / g and 250 ² / g. The pore volume of said support is generally between 0.3 ml / g and 1.2 ml / g, and preferably between 0.4 ml / g and 1 ml / g.

The support can also contain a mixed oxide phase containing cobalt and / or nickel. The term “mixed oxide phase containing cobalt and / or nickel” is understood to mean a phase in which cobalt and / or nickel cations are combined with the oxide ions O ² ′ of the alumina and / or silica support forming thus a mixed phase containing aluminates and / or silicates containing cobalt and / or nickel. The mixed oxide phase can be in amorphous form or in crystallized form.

When the support is based on alumina, the mixed oxide phase can comprise an aluminate of formula CoAI ₂ 0 ₄ or NiAI ₂ O ₄ , in amorphous or crystallized form, for example in spinel form.

When the support is based on silica, the mixed oxide phase can comprise a silicate of formula Co ₂ Si0 ₄ or Ni ₂ SiO ₄ (cobalt- or nickelorthosilicate), in amorphous or crystallized form.

When the support is based on silica-alumina, the mixed oxide phase may comprise an aluminate of formula CoAI ₂ 0 ₄ or NiAI ₂ O ₄ in amorphous or crystallized form, for example in spinel form, and / or a silicate of formula Co ₂ Si0 ₄ or Ni ₂ SiO ₄ , in amorphous or crystallized form.

Generally, the content of the mixed oxide phase in the support is between 0.1 and 45% by weight relative to the support, preferably between 0.5 and 30% by weight, and more preferably between 1 and 20% weight.

The presence of mixed oxide phase in the catalyst according to the invention is measured by reduction in programmed temperature RTP (or TPR for temperature programmed reduction according to English terminology) such as for example described in Oil & Gas Science and Technology, Rev. IFP, Vol. 64 (2009), No. 1, pp.

11-12. According to this technique, the catalyst is heated under the flow of a reducing agent, for example under the flow of dihydrogen. Measuring the dihydrogen consumed as a function of temperature gives quantitative information on the reducibility of the species present. The presence of a mixed oxide phase in the catalyst is thus manifested by consumption of dihydrogen at a temperature above about 800 ° C.

The support can have a morphology in the form of beads, extrudates (for example of three-lobed or four-lobed form) or pellets, in particular when said catalyst is used in a reactor operating in a fixed bed, or have a morphology in the form of powder of variable particle size, especially when said catalyst is used in a bubble column type reactor (or slurry bubble column according to the English termination). The grain size of the catalyst can be between a few microns and a few hundred microns. For use in a slurry reactor, the particle size of the catalyst is preferably between 10 microns and 500 microns, preferably between 10 microns and 300 microns, very preferably between 20 and 200 microns, and even more preferred between 30 and 160 microns.

According to a variant, the catalyst comprises, in addition to the elements Ni, W, Si and Al and optionally the element Co, a different element chosen from groups VIII, IA, IB, IIA, IIB, IIIA, IIIB and VA.

Possible preferred group VIII elements are platinum, ruthenium and rhodium. The preferred group IA elements are sodium and potassium. The preferred group IB items are silver and gold. The preferred group IIA elements are manganese and calcium. The preferred group IIB element is zinc. The preferred group IIIA elements are boron and indium. The preferred group IIIB elements are lanthanum and cerium. The preferred VA element is phosphorus.

The content of any element of groups VIII, IA, IB, IIA, IIB, IIIA, IIIB and / or VA is between 50 ppm and 20% by weight, preferably between 100 ppm and 15% by weight, and more preferably between 100 ppm and 10% weight expressed as an element relative to the total weight of the catalyst.

Preparation process

Said catalyst can be prepared by any method known to a person skilled in the art. A preferred preparation process includes the following steps:

a) a step of bringing the support into contact comprising alumina, silica or silica-alumina with at least one solution containing at least one precursor of nickel and tungsten,

b) a drying step at a temperature below 200 ° C,

c) a reduction step at a temperature between 410 and 900 ° C.

Step a) can be preceded by a step for forming a mixed oxide phase containing cobalt and / or nickel (stabilization step), drying step b) can be followed by a calcination step .

The different stages of the process leading to the catalyst according to the invention are detailed below:

Optional stage before stage a): Stage of formation of the mixed oxide phase containing cobalt and / or nickel

According to a variant, before the contacting step a), a step of bringing the support into contact with at least one solution containing at least one cobalt and / or nickel precursor is carried out, then dried and calcined at a temperature between 700 and 1200 ° C, so as to obtain a mixed oxide phase containing cobalt and / or nickel in the support.

The objective of this step is the formation of a mixed oxide phase containing cobalt and / or nickel in a support comprising alumina, silica or silica-alumina by bringing into contact with a solution containing at least one cobalt and / or nickel precursor, followed by drying and calcination at high temperature.

It is known that the presence of a mixed oxide phase containing cobalt and / or nickel in a support of the alumina, silica or silica-alumina type makes it possible to improve the resistance to the phenomenon of chemical and mechanical attrition in a Fischer-Tropsch process, and therefore to stabilize the support.

The formation of the mixed oxide phase in the support, often called the support stabilization step, can be carried out by any method known to those skilled in the art. It is generally carried out by introducing cobalt and / or nickel in the form of a salt precursor, for example of the nitrate type, on the initial support containing alumina, silica or silica-alumina. By calcination at very high temperature, the mixed oxide phase containing cobalt and / or nickel, is formed and stabilizes the entire support. The cobalt and / or nickel contained in the mixed oxide phase is not reducible during the final activation of the Fischer5 Tropsch catalyst (reduction). The cobalt and / or nickel contained in the mixed oxide phase therefore does not constitute the active phase of the catalyst.

According to this step, a step is carried out of bringing a support comprising alumina, silica or silica-alumina into contact with at least one solution containing at least one cobalt and / or nickel precursor, then dried and calcined at a temperature between 700 and 1200 ° Q so as to obtain a mixed oxide phase containing cobalt and / or nickel in the support.

More particularly, this step can be carried out by impregnation, preferably dry, of a support comprising alumina, silica or silica alumina, preformed or in powder, with at least one aqueous solution containing the cobalt precursor. and / or nickel, followed by drying and calcination at a temperature between 700 and 1200 ° C.

The cobalt is brought into contact with the support via any cobalt precursor soluble in the aqueous phase. Preferably, the cobalt precursor is introduced in aqueous solution, preferably in the form of nitrate, carbonate, acetate, chloride, complexes formed with acetylacetonates, or any other inorganic derivative soluble in aqueous solution, which is brought into contact with said support. The cobalt precursor advantageously used is cobalt nitrate or cobalt acetate.

The nickel is brought into contact with the support by means of any nickel precursor soluble in the aqueous phase. Preferably, said nickel precursor is introduced in aqueous solution, for example in the form of nitrate, carbonate, acetate, chloride, hydroxide, hydroxycarbonate, oxalate, complexes formed with acetylacetonates, or any other inorganic derivative soluble in aqueous solution, which is brought into contact with said support. The nickel precursor advantageously used is nickel nitrate, nickel chloride, nickel acetate or nickel hydroxycarbonate.

The total content of cobalt and / or nickel is advantageously between 1 and 20% by weight and preferably between 2 and 10% by weight relative to the total mass of the final support.

The drying is advantageously carried out at a temperature between 60 ° C and 200 ° C, preferably for a period ranging from 30 minutes to three hours.

The calcination is carried out at a temperature between 700 and 1200 ° C, preferably between 850 and 1200 ° C, and preferably between 850 and 1100 ° C, generally for a period between one hour and 24 hours and from preferably between 2 hours and 5 hours. The calcination is generally carried out under an oxidizing atmosphere, for example in air, or in oxygen-depleted air; it can also be carried out at least in part under nitrogen. It allows cobalt and / or nickel precursors and alumina and / or silica to be transformed into a mixed oxide phase containing cobalt and / or nickel.

According to a variant, the calcination can also be carried out in two stages, said calcination is advantageously carried out at a temperature between 300 ° C and 600 ° C in air for a period of time between half an hour and three hours, then at a temperature between 700 ° C and 1200 ° C, preferably between 850 and 1200 ° C and preferably between 850 and 1100 ° C, generally for a period of between one hour and 24 hours, and preferably between 2 hours and 5 hours.

Thus, at the end of this stabilization step, said support comprising alumina, silica or silica-alumina further comprises a mixed oxide phase containing cobalt and / or nickel. When the support is based on alumina or silica-alumina, the mixed oxide phase comprises an aluminate of formula C0AI2O4 or N1AI2O4. When the support is based on silica or silica-alumina, the mixed oxide phase comprises a silicate of formula C02S1O4 or Ni ₂ SiO4.

Step a): Introduction of the active phase

Step a) of bringing said support into contact with at least one solution containing at least one nickel precursor and one tungsten precursor can be carried out by any method well known to those skilled in the art. Said step a) is preferably carried out by impregnating the support with at least one solution containing at least one nickel precursor and one tungsten precursor. In particular, said step a) can be carried out by dry impregnation, by excess impregnation, or even by deposition - precipitation (as described in patents US 5,874,381 and US 6,534,436) according to methods well known in the art. 'Man of the trade. Preferably, said step a) is carried out by dry impregnation, which consists in bringing the catalyst support into contact with a solution containing at least one nickel precursor and at least one tungsten precursor, the volume of which is equal to pore volume of the support to be impregnated. This solution contains the nickel and tungsten elements at the desired concentration.

Nickel and tungsten are brought into contact with said support by means of any precursor soluble in the aqueous phase or in the organic phase. When it is introduced in organic solution, said nickel precursor is for example nickel acetate and said tungsten precursor is for example Bis (cyclopentadienyl) tungsten (IV) dihydride. Preferably, said nickel and tungsten precursors are introduced in aqueous solution, for example in the form of nitrate, carbonate, hydroxide, acetate, chloride, complexes formed with acetylacetonates, or any other derivative inorganic soluble in aqueous solution for the nickel element, and for example in the form of tungstic acid, ammonium paratungstate, ammonium metatungstate, or any other derivative inorganic soluble in aqueous solution for the element tungsten. Advantageously used as nickel precursor nickel nitrate or nickel acetate. Advantageously, the ammonium paratungstate or ammonium metatungstate will be used as the tungsten precursor.

The nickel content of said catalyst is between 1 and 30%, preferably between 2 and 20% by weight, expressed as a metallic element relative to the total weight of the catalyst. The tungsten content is between 0.1% and 20%, preferably between 1% and 15% by weight, expressed as a metallic element relative to the total weight of the catalyst.

Drying step b)

In accordance with the drying step b) of the implementation for the preparation of the catalyst, the drying is carried out at a temperature below 200 ° C., advantageously between 50 and 180 ° C., preferably between 70 and 150 ° C. , very preferably between 75 and 130 ° C. The drying step is preferably carried out for a period of between 5 minutes and 24 hours, preferably under an inert atmosphere or under an atmosphere containing oxygen.

The drying step can be carried out by any technique known to those skilled in the art. It is advantageously carried out at atmospheric pressure or at reduced pressure. Preferably, this step is carried out at atmospheric pressure. It is advantageously carried out in a fluidized bed using air or any other hot gas. Preferably, when the drying is carried out in a fluidized bed, the gas used is either air, or an inert gas such as argon or nitrogen. Very preferably, the drying is carried out in a fluidized bed in the presence of nitrogen and / or air. Preferably, the drying step has a short duration of between 5 minutes and 4 hours, preferably between 30 minutes and 4 hours and very preferably between 1 hour and 3 hours.

At the end of the drying step b), a dried catalyst is then obtained.

Optional step after the drying step b): Calcination step

At the end of the drying step b), a calcination step is optionally carried out at a temperature between 200 ° C and 550 ° C, preferably between 250 ° C and 500 ° C, under a dry atmosphere (nitrogen for example) or in an atmosphere containing oxygen (air for example). The duration of this heat treatment is generally between 0.5 hours and 16 hours, preferably between 1 hour and 5 hours.

Step c) reduction

Prior to its use in the catalytic reactor and the implementation of the Fischer-Tropsch process according to the invention, the dried catalyst obtained in step b) or the calcined catalyst obtained after the calcination carried out after the drying step b) undergoes a reducing treatment, for example with hydrogen, pure or diluted, at high temperature. This treatment makes it possible to activate said catalyst and to form particles of metal Ni ₄ W alloy. The temperature of this reducing treatment is between 410 ° C and 900 ° C, and most preferably between 550 ° C and 800 ° C. Its duration is generally between 2 and 20 hours.

w This reducing treatment is carried out either in situ (in the same reactor as that in which the Fischer-Tropsch reaction is carried out according to the process of the invention), or ex situ before being loaded into the reactor.

Alternatively, when the catalyst contains one or more additional elements from groups VIII, IA, IB, IIA, IIB, NIA, IIIB and / or VA, this or these elements may be either initially present on the support before the preparation of the catalyst, is introduced at any time of the preparation and by any methods known to those skilled in the art.

Fischer-Tropsch process

Finally, another object of the invention is the use of the catalyst according to the invention in a Fischer-Tropsch synthesis process.

The Fischer-Tropsch process according to the invention leads to the production of essentially linear and saturated C5 + hydrocarbons (having at least 5 carbon atoms per molecule). The hydrocarbons produced by the process of the invention are thus essentially paraffinic hydrocarbons, the fraction of which exhibits the highest boiling points can be converted with a high yield into middle distillates (gas oil and kerosene cuts) by a process of hydroconversion such as hydrocracking and / or catalytic hydroisomerization (s).

The feed used for implementing the process of the invention comprises synthesis gas. The synthesis gas is a mixture comprising in particular carbon monoxide and hydrogen having H ₂ / CO molar ratios which can vary in a ratio of 0.5 to 4 depending on the process by which it was obtained. The H ₂ / CO molar ratio of the synthesis gas is generally close to 3 when the synthesis gas is obtained from the process of steam reforming of hydrocarbons or alcohol. The H ₂ / CO molar ratio of the synthesis gas is of the order of 1.5 to 2 when the synthesis gas is obtained from a partial oxidation process. The H ₂ / CO molar ratio of the synthesis gas is generally close to 2.5 when it is obtained from a thermal reforming process. The H ₂ / CO molar ratio of the synthesis gas is generally close to 1 when it is obtained from a gasification and CO ₂ reforming process.

The catalyst used in the hydrocarbon synthesis process according to the invention can be used in different types of reactors, for example in a fixed bed, in a moving bed, in a bubbling bed or even in a three-phase fluidized bed. The use of the catalyst in suspension in a three-phase fluidized reactor, preferably of the bubble column type, is preferred. In this preferred implementation of the catalyst, said catalyst is divided into a very fine powder, particularly of the order of a few tens of microns, this powder forming a suspension with the reaction medium. This technology is also known by the slurry process terminology by a person skilled in the art.

The process for synthesizing hydrocarbons according to the invention is carried out under a total pressure of between 0.1 and 15 MPa, preferably between 0.5 and 10 MPa, at a temperature between 150 and 350 ° C, preferably between 180 and 270 ° C. The hourly volume speed is advantageously between 100 and 20,000 volumes of synthesis gas per volume of catalyst and per hour (100 to 20,000 h ' ¹ ) and preferably between 400 and 10,000 volumes of synthesis gas per volume of catalyst and per hour (400 to 10,000 h ' ¹ ).

The following examples demonstrate the performance gains on the catalysts according to the invention.

Examples

Example 1 (comparative): Catalyst A of formula Co / AI2O3.S1O2

A catalyst A comprising cobalt deposited on a silica-alumina support is prepared by dry impregnation of an aqueous solution of cobalt nitrate hexahydrate (Alfa Aesar ™, <97.7%) so as to deposit in one step approximately 10 % by weight of Co on a silica-alumina initially containing 5% by weight of SiO ₂ , with an average particle size equal to 80 μm, and having a specific surface of 180 m ² / g and a pore volume of 0.6 ml / g.

After dry impregnation, the solid is dried in a traversed bed at 120 ° C for 3 hours in air and then calcined at 400 ° C for 4 hours in a trapped bed. The solid is finally reduced exsitu under a stream of pure hydrogen at 400 ° C for 16 hours.

The DRX analysis of catalyst A shows the presence of a majority Co ° metallic cobalt phase and a minority CoO decobalt oxide phase.

Example 2 (comparative): Catalyst B of formula Co / COAI2O4-AI2O3.S1O2

A catalyst B comprising cobalt deposited on a support, based on a mixed oxide phase (in the form of spinel) included in a silica-alumina, is prepared by dry impregnation of an aqueous solution of cobalt nitrate hexahydrate (Alfa Aesar ™, <97.7%) so as to deposit in one step approximately 10% by weight of cobalt on the support.

The spinel present in the support of catalyst B is a simple spinel formed from cobalt aluminate, which is included in a silica-alumina containing 5% by weight of S1O2, of average particle size equal to 80 μm, and having a specific surface of 180 m ² / g and a pore volume of 0.6 ml / g. The spinel included in the silica-alumina is prepared by dry impregnation of an aqueous solution of cobalt nitrate hexahydrate (Alfa Aesar ™, <97.7%) so as to introduce 5% by weight of Co into said silica -alumina. After drying at 120 ° C for 3 hours, the solid is calcined at 850 ° C for 4 hours in air.

The catalyst support denoted B ’is formed from 5% by weight of cobalt in the form of cobalt aluminate (ie 15% by weight of spinel) in silica-alumina.

The cobalt-based active phase is then deposited on said support in one step, by dry impregnation, according to a protocol identical to that described for the preparation of catalyst A. The drying, calcination and reduction steps are also carried out in the same operating conditions as those of Example 1. The concentration of cobalt in the cobalt nitrate solution, used for the successive impregnations, is chosen to obtain catalyst B with the desired final Co content (10% by weight of Co ).

The X-ray analysis of catalyst B shows the presence of a majority Co ° metallic cobalt phase and a minority CoO decobalt oxide phase.

Example 3 (comparative): Catalyst C of formula Ni-W / AI2O3.S1O2.

A catalyst C comprising nickel and tungsten on a silica alumina support is prepared by dry impregnation of an aqueous solution of nickel nitrate hexahydrate (Alfa Aesar ™, 98%) and hydrated ammonium metatungstate (Aldrich ™, > 85% WO ₃ ). The amounts of nickel and tungsten are calculated so as to have an isomolar catalyst made of metallic elements relative to catalyst A. The catalyst C is therefore prepared so as to deposit approximately 8% by weight of element Ni and 6% by weight d element W on the silica-alumina support initially containing 5% by weight of SiO ₂ , of average particle size equal to 80 μm, and having a specific surface of 180 m ² / g and a pore volume of 0.6 ml / g.

After dry impregnation, the solid is dried in a traversed bed at 120 ° C for 3 hours in air and then calcined at 400 ° C for 4 hours in a trapped bed. The solid is finally reduced exsitu under a stream of pure hydrogen at 400 ° C for 16 hours.

The X-ray analysis of catalyst C reveals the presence of a majority nickel metal nickel phase and of minority tungsten oxide and nickel phases. The Ni ₄ W phase is not detected by X-ray diffraction.

Example 4 (according to the invention): Catalyst D of formula Ni-W / AI2O3.S1O2.

Catalyst D is prepared in the same way as catalyst C, except for the reduction step which is carried out at 750 ° C.

The X-ray analysis of catalyst D shows the presence of a majority Ni ₄ W phase and a minority metallic nickel phase.

Example 5 (according to the invention): Catalyst E of formula Ni-W / COAI2O4AI2O3.S1O2

A catalyst E comprising nickel and tungsten deposited on a support, based on a mixed oxide phase (in the form of spinel) included in an alumina silica, is prepared by dry impregnation of an aqueous solution of nitrate of nickel hexahydrate (Alfa Aesar ™, 98%) and ammonium molybdate tetrahydrate (Aldrich ™,> 99%). The amounts of nickel and tungsten are calculated so as to have an isomolar catalyst made of metallic elements relative to catalyst A. The catalyst E is therefore prepared so as to deposit approximately 8% by weight of element Ni and 6% by weight d 'Mo element.

The spinel present in the support of catalyst E is a simple spinel formed from cobalt aluminate, which is included in a silica-alumina containing 5% by weight of S1O2, of average particle size equal to 80 μm, and having a specific surface of 180 m ² / g and a pore volume of 0.6 ml / g. The spinel included in the silica-alumina is prepared by dry impregnation of an aqueous solution of cobalt nitrate hexahydrate (Alfa Aesar ™, <97.7%) so as to introduce 5% by weight of Co into said silica -alumina. After drying at 120 ° C for 3 hours, the solid is calcined at 850 ° C for 4 hours in air. The catalyst support denoted E ′ is formed from 5% by weight of cobalt in the form of cobalt aluminate (ie 15% by weight of spinel) in silica-alumina.

The active phase based on nickel and tungsten is then deposited on said support E 'in one step, by dry impregnation, according to a protocol identical to that described for the preparation of catalyst C. The stages of drying, calcination and reduction are carried out under the same operating conditions as those of Example 4.

The DRX analysis of catalyst E shows the presence of a majority Ni ₄ W phase and a minority metallic nickel phase.

EXAMPLE 6 Catalytic performances of catalysts A to E in the Fischer-Tropsch reaction

The reduced catalysts A, B, C, D and E are protected from reoxidation by a solvent of paraffinic nature is introduced into a continuous batch reactor filled with commercial wax (Duracyne®) at a temperature of 100-120 ° C, the test is then started by injecting synthesis gas, under the following conditions:

- Temperature = 220 ° C

- Total pressure = 2MPa

- H ₂ / CO molar ratio = 2

- CO conversion maintained at 45-50% by adjusting the gas flow rate

H ₂ / CO

The test conditions are adjusted by modifying the flow rate of synthesis gas so as to achieve a constant CO conversion whatever the activity of the catalyst and whatever its level of deactivation during the test.

The activity of a catalyst is calculated relative to catalyst A

Activity = exp

-E

PT 'ç exp base with Tref = 225 ° C, E = activation energy and R = constant of ideal gases.

For the reference catalyst A, the activity is 100%.

The results are also expressed in terms of methane selectivity (mass percentage of methane on all of the products formed),

Catalyst CO conversion at 300h under reaction flow (% rel) Selectivity in CH ₄ at 300h under reaction flow (% by weight) A (comparative) 100 14.4 B (comparative) 139 11.1 C (comparative) 14 37.0 D (according to the invention) 116 13.2 E (according to the invention) 147 12.0

Table 1: catalytic performance of each catalyst

The results appearing in Table 1 demonstrate that the catalyst according to the invention shows an activity and a selectivity at least equivalent or even superior to the catalysts known from the prior art based on cobalt.

Claims (14)

1) Catalyst containing a nickel-tungsten alloy Ni ₄ W, deposited on a support comprising alumina, silica or silica-alumina. 2) Catalyst according to claim 1, in which the nickel content is between 1 and 30% by weight, expressed as a metallic element relative to the total weight of the catalyst. 3) Catalyst according to claims 1 or 2, wherein the tungsten content is between 0.1% and 20% by weight, expressed as a metallic element relative to the total weight of the catalyst. 10 4) Catalyst according to one of the preceding claims, in which said support also contains a mixed oxide phase containing cobalt and / or nickel. 5) Catalyst according to the preceding claim, in which the content of the mixed oxide phase in the support is between 0.1 and 45% by weight relative to the weight of the support. 15 6) Catalyst according to one of claims 4 or 5, wherein the mixed oxide phase comprises an aluminate of formula C0AI2O4 or N1AI2O4 in the case of a support based on alumina or silica-alumina. 7) Catalyst according to one of claims 4 to 6, in which the mixed oxide phase comprises a silicate of formula Co ₂ Si0 ₄ or Ni ₂ SiO4 in the case of a 20 support based on silica or silica-alumina. 8) Catalyst according to one of the preceding claims, in which the silica content of said support is between 0.5% by weight to 30% by weight relative to the weight of the support before the formation of the mixed oxide phase when the support is a silica-alumina. 25 9) Catalyst according to one of the preceding claims, which further comprises an element chosen from groups VIII, IA, IB, IIA, IIB, IIIA, IIIB and VA. 10) Process for the preparation of the catalyst according to claims 1 to 9 comprising the following successive steps: a) a step of bringing the support into contact comprising alumina, silica or silica-alumina with at least one solution containing at least one 5 nickel and tungsten precursor, b) a drying step at a temperature below 200 ° C, c) a reduction step at a temperature between 410 and 900 ° C. 11) A preparation method according to claim 10 in which the reduction step c) is carried out at a temperature between 550 and 800 ° C. 10 12) A method of preparation according to claims 10 or 11 wherein, before the contacting step a), a step of bringing the support into contact with at least one solution containing at least one cobalt precursor and / or nickel, then dried and calcined at a temperature between 700 and 1200 ° C, so as to obtain a mixed oxide phase containing cobalt 15 and / or nickel in the support. 13) A method of preparation according to claims 10 to 12 wherein, after the drying step b), a calcination step is carried out at a temperature between 200 and 550 ° C, under a irire atmosphere or under an atmosphere containing oxygen. 20 14) Fischer-Tropsch process for the synthesis of hydrocarbons in which the catalyst according to any one of claims 1 to 9 is brought into contact with a charge comprising synthesis gas under a total pressure of between 0.1 and 15 MPa, at a temperature between 150 and 350 ° C, and at an hourly volume speed between 100 and 20,000 gas volumes of 25 synthesis by volume of catalyst and per hour with a H ₂ / CO molar ratio of the synthesis gas between 0.5 and 4. FRENCH REPUBLIC National registration number irai - I NATIONAL INSTITUTE INDUSTRIAL PROPERTY PRELIMINARY SEARCH REPORT based on the latest claims filed before the start of the search FA 843530 FR 1759060 DOCUMENTS CONSIDERED AS RELEVANT Relevant claim (s) Classification attributed to the invention by ΙΊΝΡΙ Category Citation of the document with indication, if necessary, of the relevant parts US 2015/038751 Al (NG KY SIMON [US] ET AL) February 5, 2015 (2015-02-05) * paragraphs [0002], [0009], [0017], [0022] - [0024], [0032] - [0035], [0048], [0055], [0058], [0066]; figure 7 * Dionysios Vroulias: NICKEL MODIFIED CATALYSTS FOR THE PRODUCTION 0F SYNTHESIS GAS FRON BIOGAS, 1 to 10.12, 1-6,9-13 December 31, 2016 (2016-12-31), XP055477247, Extract from the Internet: URL: http: //nemertes.1is.upatras.gr/jspui/b i tstream / 10889/10778/3 / Vrouli as% 28chem% 29. pdf [extract 2018-05-22] * page ix * 14 * figures 17.9-17.10 * JO-WEI DUN ET AL: Report on the 14 catalytic activity of 6-heteropolymolybdates as potential Fischer-Tropsch synthesis catalysts, APPLIED CATALYSIS, vol. 21, no. 1 February 1, 1986 (1986-02-01), pages 61-72, XP055476760, NL ISSN: 0166-9834, D0I: 10.1016 / 50166-9834 (00) 81328-7 * Materials * * table 2 * Research completion date B01J23 / 888 B01J21 / 00 B01J37 / 16 C10G2 / 00 TECHNICAL AREAS SOUGHT (IPC) C10G C07C B01J EPO FORM 1503 12.99 (P04C14) Examiner Trader, Karin May 23, 2018 T: theory or principle underlying the invention E: patent document with a date prior to the filing date and which was only published on that filing date or on a later date. D: cited in the request L: cited for other reasons CATEGORY OF DOCUMENTS CITED X: particularly relevant on its own Y: particularly relevant in combination with another document in the same category A: technological background O: unwritten disclosure P: interlayer document &: member of the same family, corresponding document ANNEX TO THE PRELIMINARY RESEARCH REPORT RELATING TO THE FRENCH PATENT APPLICATION NO. FR 1759060 FA 843530 This appendix indicates the members of the patent family relating to the patent documents cited in the preliminary search report referred to above. The said members are contained in the computer file of the European Patent Office on 23-05-2018 The information provided is given for information only and does not engage the responsibility of the European Patent Office or of French administration