FR3053898A1 - PROCESS FOR PREPARING AN IRRADIATION-ASSISTED COBALT COMPOSITION - Google Patents

Abstract

A process for the preparation by photo-assisted condensation of a composition comprising a support containing a semiconductor having on its surface particles of cobalt in the metallic state, which process comprises the following steps: a) a support containing a semi -conductor and suspending it in a non-aqueous phase with stirring comprising a soluble cobalt precursor; b) the suspension obtained in step a) is irradiated with an irradiation source so that at least a part of the emission spectrum of said irradiation source is composed of photons of energies greater than the bandgap width of said semiconductor.

Description

® FRENCH REPUBLIC

NATIONAL INSTITUTE OF INDUSTRIAL PROPERTY © Publication number: 3,053,898 (to be used only for reproduction orders)

©) National registration number: 16 56741

COURBEVOIE © Int Cl ⁸ : B 01 J 23/75 (2017.01), B 01 J 37/34, 37/02, B 82 Y 40/00

A1 PATENT APPLICATION

©) Date of filing: 13.07.16. © Applicant (s): IFP ENERGIES NOUVELLES Etablis- (© Priority: public education - FR. @ Inventor (s): FECANT ANTOINE, TAVERNIER EUGENIE and LECOCQ VINCENT. (43) Date of public availability of the request: 19.01.18 Bulletin 18/03. ©) List of documents cited in the report preliminary research: Refer to end of present booklet (© References to other national documents ® Holder (s): IFP ENERGIES NOUVELLES Etablisse- related: public. ©) Extension request (s): © Agent (s): IFP ENERGIES NOUVELLES.

Pty PROCESS FOR PREPARING A COMPOSITION BASED ON COBALT ASSISTED BY IRRADIATION.

FR 3 053 898 - A1

Process for the preparation by photo-assisted condensation of a composition comprising a support containing a semiconductor having on its surface particles of cobalt in the metallic state, which process comprises the following steps:

a) providing a support containing a semiconductor and suspending it in a non-aqueous phase with stirring comprising a soluble cobalt precursor;

b) the suspension obtained in step a) is irradiated with an irradiation source so that at least part of the emission spectrum of said irradiation source is composed of photons of energies greater than the prohibited bandwidth of said semiconductor.

PROCESS FOR PREPARING A COMPOSITION BASED ON IRRADIATION ASSISTED COBALT

Field of the invention

The invention relates to a process for the preparation of an irradiation-assisted composition which can be used as a catalyst, in particular for the Fischer-Tropsch synthesis process.

State of the art

The preparation of catalyst assisted by irradiation is known from the state of the art. For example, X. Wang et al. (Advanced Materials Research, vol. 148-149, p. 1258, 2001) and MC Hidalgo et al. (Applied Catalysis A: General, vol 397, p. 112, 2012) propose several catalyst synthesis routes comprising gold nanoparticles as active phase deposited on a TiO ₂ semiconductor by photo-deposition in a suspension aqueous containing HAuCI ₄ as a gold precursor, and ethanol or isopropanol as a sacrificial agent.

On the other hand, F. Zhang et al. (Catalysis today, vol. 93, p. 645, 2004) propose a catalyst synthesis route comprising palladium nanoparticles on a TiO ₂ semiconductor by photo-deposition in an aqueous suspension containing Na ₂ PdCI ₄ as as a palladium precursor, and ethanol as a sacrificial agent.

Likewise, F. Zhang et al. (Langmuir, vol. 19, p. 8230, 2003) propose a catalyst synthesis route comprising silver nanoparticles on a TiO ₂ semiconductor by photo-deposition in an aqueous suspension containing AgNO ₃ as a precursor of palladium, water as a solvent acting as a sacrificial agent.

Finally, F. Zhang et al. (Langmuir, vol. 20, p. 9329, 2004) propose a catalyst synthesis route comprising platinum nanoparticles on a TiO ₂ semiconductor by photo-deposition in an aqueous suspension containing K ₂ PtCI ₆ as palladium precursor, and ethanol as a sacrificial agent.

However, to date there is no synthesis method assisted by irradiation of catalyst based on supported cobalt nanoparticles. Indeed, even though this method is known for the deposition of noble metal phases, the photo-deposition of cobalt, less easily reducible than the noble metals has not hitherto been carried out. Photo-assisted deposits of cobalt phosphates on Fe ₂ O ₃ and TiO ₂ supports have been described in the literature (and. KJ McDonald et al. Chemistry of materials, vol. 23, p. 1686, 2011; L. Lin et al. Science China Chemistry, vol. 55, p. 1976, 2012). These methods consist of the oxidation of Co ²⁺ ions in aqueous solution to Co ³⁺ ions stabilized by phosphate ions (Pi) to form a Co-Pi phase in the form of particles on the surface of a conductive semi3053898. However, this deposition method does not provide a way to reduce cobalt ions to metal particles of cobalt.

The Applicant has developed a new process for the preparation of a composition, usable as a catalyst, based on supported cobalt nanoparticles, assisted by irradiation, which process differing from the preparation processes assisted by irradiation known from the prior art in that the preparation process takes place in a nonaqueous medium, allowing in particular the reduction of dissolved Co ²⁺ or Co ³⁺ ions rather than the reduction of H ⁺ protons present in an aqueous medium to form dihydrogen in place of metallic cobalt.

The preparation process according to the invention makes it possible in a simplified manner to obtain a catalyst based on cobalt particles in the metallic state on the surface of a semiconductor support, and this with a reduced number of steps compared to the prior art. "Metallic cobalt" means cobalt with a zero oxidation state (and therefore in the form of metal).

Objects of the invention

A first object according to the invention relates to a process for the preparation by photo-assisted condensation of a composition comprising a support containing a semiconductor having on its surface particles of cobalt in the metallic state, which process comprises the following steps:

a) providing a support containing a semiconductor and suspending it in a non-aqueous phase with stirring comprising a soluble cobalt precursor;

b) the suspension obtained in step a) is irradiated with an irradiation source so that at least part of the emission spectrum of said irradiation source is composed of photons of energies greater than the prohibited bandwidth of said semiconductor;

c) optionally, the composition of the suspension from step b) is at least partially separated;

d) optionally, the composition obtained in step c) is dried;

e) optionally, the dried composition obtained in step d) is subjected to a heat treatment.

Advantageously, the semiconductor is chosen from an inorganic or organic-inorganic semiconductor.

Preferably, the semiconductor is chosen from TiO ₂ , Ce ₂ O ₃ , CeO ₂ , WO ₃ , ZrO ₂ , CoTi0 ₃ , NiTiO ₃ , FeTiO ₃ , CuTiO ₃ , MnTiO ₃ , ZnTiO ₃ , ZnO, ZnFe ₂ O ₄ , ZrO ₂ , CoAI ₂ 0 ₄ , NiAI ₂ O ₄ , FeAI ₂ O ₄ , MnAI ₂ O ₄ , Co ₂ Si0 ₄ , Ni ₂ SiO ₂ , Fe ₂ SiO ₄ , AITiO ₃ , SiC alone or as a mixture.

Preferably, the loading rate of the semiconductor in the non-aqueous phase is between 0.1 and 500 g / L.

Preferably, the non-aqueous phase is chosen from alcohols, aldehydes or amines.

Advantageously, said particles of cobalt in the metallic state are in the form of particles of sizes between 0.5 nm and 1000 nm.

Preferably, the soluble cobalt precursor is cobalt nitrate, cobalt acetate or a cobalt acetylacetonate.

Advantageously, the content of cobalt in the metallic state is between 0.1 and 40% by weight relative to the total weight of the composition.

Preferably, the non-aqueous phase also comprises a sacrificial agent chosen from alcohols, aldehydes or amines.

Advantageously, the molar ratio between the sacrificial agent and the cobalt precursor is greater than 1, preferably between 1 and 5.

The source of radiation is a source of artificial or natural radiation.

Advantageously, in step c), the separation is carried out by centrifugation.

Preferably, in step d), the drying is carried out between 30 ° C and 200 ° C. Advantageously, the dried composition obtained in step d) is subjected to a heat treatment under hydrogen at a temperature between 50 ° C and 500 ° C, at an absolute pressure between 0.1 MPa and 1.5 MPa (step e )).

A second object according to the invention relates to the use of the composition obtained by the process according to the invention as a catalyst in a FischerTropsch synthesis process operating in the presence of synthesis gas under a total pressure of between 0.1 and 15 MPa, at a temperature between 150 and 350 ° C, at an hourly volume speed between 100 and 20,000 volumes of synthesis gas per volume of catalyst and per hour.

Detailed description of the invention

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 IUPAC classification.

The process for preparing the composition according to the invention involves depositing the cobalt on the surface of the support by photo-assisted condensation. More particularly, the method comprises the following steps:

a) a support containing a semiconductor is provided and it is suspended in a non-aqueous phase with stirring comprising a soluble cobalt precursor, and optionally a sacrificial agent;

b) the suspension obtained in step a) is irradiated with an irradiation source such that at least part of the emission spectrum of said irradiation source is composed of photons of energies greater than the bandwidth prohibited said semiconductor;

c) optionally, the composition of the suspension from step b) is at least partially separated;

d) optionally, the composition obtained in step c) is dried;

e) optionally, the dried composition obtained in step d) is subjected to a heat treatment.

Step a)

In step a), a support is provided containing a semiconductor, and it is suspended with stirring in a non-aqueous phase comprising a soluble cobalt precursor.

The semiconductors used according to the invention comprise at least one inorganic or organic-inorganic semiconductor. The forbidden bandwidth of the inorganic or organic-inorganic semiconductor is generally between 0.1 and 5.5 eV.

According to a first variant, the semiconductor comprises at least one inorganic solid. The inorganic semiconductor may comprise one or more elements chosen from the elements of group IVA, such as silicon, germanium, silicon carbide or silicon-germanium. It can also contain one or more elements of groups IIIA and VA, such as GaP, GaN, InP and InGaAs, or elements of groups IIB and VIA, such as CdS, ZnO and ZnS, or elements of groups IB and VIIA, such as CuCI and AgBr, or elements of groups IVA and VIA, such as PbS, PbO, SnS and PbSnTe, or elements of groups VA and VIA, such as Bi ₂ Te ₃ and Bi ₂ O ₃ , or elements of groups IIB and VA, such as Cd ₃ P ₂ , Zn ₃ P ₂ and Zn ₃ As ₂ , or elements of groups IB and VIA, such as CuO, Cu ₂ O and Ag ₂ S, or elements of groups VIII and VIA, such as CoO, PdO, Fe ₂ O ₃ and NiO, or elements of groups VIB and VIA, such as MoS ₂ and WO ₃ , or elements of groups VB and VIA, such as V ₂ O ₅ and Nb ₂ O ₅ , or elements of groups IVB and VIA, such as TiO ₂ and HfS ₂ , or elements of groups IIIA and VIA, such as ln ₂ O ₃ , ln ₂ S ₃ or ln (OH) ₃ , or elements of the VIA groups and lanthanides, such as Ce ₂ O ₃ , Pr ₂ O ₃ , Sm ₂ S ₃ , Tb ₂ S ₃ and La ₂ S ₃ , or elements of the VIA groups and actinides, such as UO ₂ and UO ₃ . Preferably, the semiconductor is chosen from TiO ₂ , Ce ₂ O ₃ , CeO ₂ , WO ₃ , ZrO ₂ , CoTi0 ₃ , NiTiO ₃ , FeTiO ₃ , CuTiO ₃ , MnTiO ₃ , ZnTiO ₃ , ZnO, ZnFe ₂ O ₄ , ZrO ₂ , CoAI ₂ 0 ₄ , NiAI ₂ O ₄ , FoAI ₂ O ₄ , MnAI ₂ O ₄ , Co ₂ Si0 ₄ , Ni ₂ SiO ₂ , Fo ₂ SiO ₄ , AITiO ₃ , SiC alone or as a mixture. Very preferably, the semiconductor is chosen from TiO ₂ , ZnO, WO ₃ , CeO ₂ , ZrO ₂ , CoAI ₂ O ₄ , NiAI ₂ O ₄ , FoAI ₂ O ₄ , MnAI ₂ O ₄ .

According to another variant, the semiconductor comprises at least one organic-inorganic semiconductor. Among the organic-inorganic semiconductors, mention may be made of crystallized solids of the MOF type (for Metal Organic Frameworks according to English terminology). MOFs are made up of inorganic subunits (transition metals, lanthanides, etc.) connected together by organic ligands (carboxylates, phosphonates, imidazolates, etc.), thus defining crystallized, sometimes porous, hybrid networks.

The semiconductor may optionally be doped with one or more ions chosen from metal ions, such as for example ions of V, Ni, Cr, Mo, Fe, Sn, Mn, Co, Re, Nb, Sb, La, Ce, Ta, Ti, non-metallic ions, such as for example C, N, S, F, P, or by a mixture of metallic and non-metallic ions.

The semiconductor can be in different forms (nanometric powder, nanoobjects with or without cavities, for example in the form of nanotube) or shaped (monolith, micrometric or millimeter-sized beads, etc.).

In another variant, the semiconductor may itself be contained in an inorganic refractory support, of alumina, silica, silica-alumina type in any proportion. Said inorganic support which can itself be presented in different forms (nanometric powder, nanoobjects with or without cavities, etc.) or shaped (monolith, beads of micrometric or millimeter size, etc.).

Any method known to a person skilled in the art may be used to supply said semiconductor.

The loading rate of the semiconductor in the non-aqueous phase is between 0.1 and 500 g / L, preferably between 0.1 and 100 g / L, very preferably between 1 and 20 g / L.

In step a) of the process according to the invention, after having provided said support containing the semiconductor, it is suspended with stirring in a non-aqueous phase comprising a soluble cobalt precursor.

The non-aqueous soluble phase can consist of all organic species and contain only trace amounts of water, preferably below 1% by volume, very preferably below 0.1% by volume. . The non-aqueous phase may be any liquid organic phase at the temperature of the preparation. Preferably, the nonaqueous phase is chosen from alcohols, aldehydes or amines. Very preferably, the non-aqueous phase is an alcohol. When the non-aqueous phase is an alcohol, methanol, ethanol, propanol or isopropanol are preferably chosen, alone or as a mixture.

The non-aqueous phase also includes a soluble cobalt precursor. The soluble cobalt precursor is generally based on chloride, iodide, bromide, fluoride, acetate, acetylacetonate, nitrate, sulfate, hydroxide. Preferably, the precursor is cobalt nitrate, cobalt acetate or a cobalt acetylacetonate.

The non-aqueous phase may optionally further comprise a sacrificial agent. The sacrificial agent is an organic or inorganic compound soluble in the nonaqueous phase. This agent will be consumed by oxidation during step b) according to the preparation process of the invention concomitantly with the reduction of Co ²⁺ or Co ³⁺ to metallic cobalt (Co °). Preferably, the sacrificial agent is chosen from alcohols, aldehydes or amines. Very preferably the non-aqueous phase is an alcohol. When the sacrificial agent is present in the non-aqueous phase, the molar ratio between the sacrificial agent and the cobalt precursor is greater than 1, preferably between 1 and 5. The mixing is generally carried out at a temperature between 5 and 90 ° C, preferably between 15 and 40 ° C, and particularly preferably at room temperature, with stirring, preferably mechanical or by bubbling.

Step b)

During step b), the suspension is irradiated by an irradiation source such that at least part of the emission spectrum of said source is composed of photons of energies greater than the prohibited bandwidth of the half driver.

The semiconductor can be excited using the energy provided by the irradiation. The absorption of a photon, whose energy is greater than the forbidden bandwidth, or bandgap according to English terminology, between the valence band and the conduction band, induces the formation of an electron- hole in the semiconductor. There is therefore the excitation of an electron at the level of the conduction band and the formation of a hole on the valence band. This electron-hole pair will allow the formation of free radicals which will either react with compounds present in the medium or then recombine according to various mechanisms. Each semiconductor has a difference in energy between its conduction band and its own valence band, or bandgap.

A semiconductor can be activated by the absorption of at least one photon. Absorbable photons are those whose energy is greater than the bandgap bandgap of the photocatalyst. In other words, the semiconductors can be activated by at least one photon with a wavelength corresponding to the energy associated with the forbidden bandwidth of the semiconductor or with a lower wavelength. The maximum wavelength absorbable by the semiconductor is calculated using the following equation:

. h '/, c

With At _max the maximum wavelength absorbable by the semiconductor (in m), h the Planck constant (4.13433559.10 ¹⁵ eV.s), c the speed of light in a vacuum (299 792 458 ms ¹ ) and Eg the forbidden bandwidth or bandgap of the semiconductor (in eV).

Preferably, the source emits at least one range of wavelengths greater than 250 nm, very preferably between 280 nm and 800 nm, which includes the UV spectrum and / or the visible spectrum. The radiation source can be any source of artificial or natural electromagnetic radiation, such as natural sunlight, an Hg type lamp, an Xe type lamp, an LED type lamp.

The duration of this step is preferably between 10 minutes and 7 days under irradiation, preferably between 1 hour and 48 hours.

At the end of step b), metallic cobalt nanoparticles are deposited on the surface of the semiconductor. The term “metallic cobalt” means cobalt being at the oxidation state zero (and therefore in the form of metal). Optionally, a fraction of the cobalt element may be in the oxidized form, the content of cobalt element in oxidized form being less than 30 mol% of cobalt in its oxidized form relative to the total content of cobalt element, preferably less at 20 mol%, more preferably less than 10 mol%, and even more preferably less than 5 mol%.

Said cobalt particles in the metallic state are preferably in the form of particles of sizes between 0.5 nm and 1000 nm, very preferably between 0.5 nm and 100 nm.

The content of cobalt in the metallic state is between 0.1 and 40% by weight, preferably between 1 and 30% by weight relative to the total weight of the composition, very preferably from 2 to 25% by weight relative to the total weight of the composition.

The composition, which can be used as a catalyst, composed of nanoparticles of metallic cobalt can be stored in the non-aqueous phase in order to keep the cobalt at the zero oxidation state for direct use in a catalytic process.

When it is desired to obtain a material free from the non-aqueous phase, it is possible optionally to proceed to step c), then optionally d) and / or optionally e).

Step cl

In step c), the composition of the suspension is separated from step d). The separation can be carried out by filtration or by centrifugation. Preferably it is carried out by centrifugation. Generally, this centrifugation is carried out for 10 to 60 minutes from 2000 to 10000 revolutions per minute. Preferably, one to three washes with an aqueous or non-aqueous phase are then carried out. When a non-aqueous phase is used for washing, this is preferably the same as that used for step a).

Step d)

In step d), the composition obtained in step c) is dried. Drying is carried out between 30 ° C and 200 ° C, generally for 1 hour to 48 hours, preferably in air. Optionally, this drying can be carried out under an inert atmosphere. The drying can optionally be carried out in an oven or a rotary evaporator. The drying step can optionally be done under partial vacuum.

Step el

The dried composition obtained in step d) can be subjected to a heat treatment under hydrogen. The heat treatment is generally carried out at a temperature between 50 ° C and 500 ° C, preferably for a period between 1 hour and 20 hours, in a reactor in a fixed bed or in a fluidized bed at an absolute pressure of between 0.1 MPa and 1 , 5 MPa (1 and 15 bar). Hydrogen can be pure or diluted. Then, the composition obtained is optionally discharged under inert into an organic solvent in order to avoid its re-oxidation, or is left in the reactor under hydrogen or inert gas for later use.

Prior to this heat treatment under hydrogen, the dried composition obtained in step d) may be subjected to a treatment under air flow, of nitrogen, optionally under partial vacuum.

A composition is thus obtained comprising a support containing a semiconductor having on its surface metallic particles of cobalt.

Use of the catalyst in a Fischer-Tropsch process

The subject of this invention also relates to the use of these compositions as catalysts, for example for the Fischer-Tropsch synthesis.

The Fischer-Tropsch synthesis processes make it possible to obtain a wide range of hydrocarbon cuts from the CO + H ₂ mixture, commonly called synthesis gas. The global equation of the Fischer-Tropsch synthesis can be written as follows:

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

Fischer-Tropsch synthesis is at the heart of the processes for converting natural gas, coal or biomass into fuels or intermediates for the chemical industry. These processes are called GtL (Gas to Liquids according to Anglo-Saxon terminology) in the case of the use of natural gas as initial charge, CtL (Coal to Liquids according to Anglo-Saxon terminology) for coal, and BtL (Biomass to Liquids according to Anglo-Saxon terminology) for biomass. In each of these cases, the initial charge is first gasified into synthesis gas, a mixture of carbon monoxide and dihydrogen. The synthesis gas is then mainly transformed into paraffins by means of the Fischer-Tropsch synthesis, and these paraffins can then be transformed into fuels by a hydroisomerization-hydrocracking process. For example, transformation processes such as hydrocracking, dewaxing, and hydroisomerization of heavy cuts (C16 +) make it possible to produce different types of fuels in the range of medium distillates: diesel (cut 180-370 ° C) and kerosene (cut 140-300 ° C). The lighter C5-C15 fractions can be distilled and used as solvents.

The Fischer-Tropsch process according to the invention thus allows the production of essentially linear and saturated C5 + hydrocarbons. In accordance with the invention, the expression “essentially linear and saturated C5 + hydrocarbons” is understood to mean hydrocarbons whose proportion of hydrocarbon compounds having at least 5 carbon atoms per molecule represents at least 50% by weight, preferably at least 80% by weight of all of the hydrocarbons formed, the total content of olefinic compounds present among said hydrocarbon compounds having at least 5 carbon atoms per molecule being less than 15% by weight. The hydrocarbons produced by the process of the invention are thus essentially paraffinic hydrocarbons, the fraction of which having the highest boiling points can be converted with a high yield into middle distillates (diesel and kerosene cuts) by a catalytic process d hydroconversion such as hydrocracking and / or hydroisomerization.

The Fischer-Tropsch synthesis reaction can be carried out in different types of reactors (fixed, mobile, or three-phase bed (gas, liquid, solid), for example of the perfectly stirred autoclave type, or in a bubble column), and the products of the reaction in particular has the characteristic of being free of sulfur-containing, nitrogenous or aromatic compounds.

Preferably, the feedstock used for implementing the process of the invention consists of synthesis gas which is a mixture of carbon monoxide and hydrogen with H ₂ / CO molar ratios which can vary between 0, 5 and 4 depending on the manufacturing process from which it comes. 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 an autothermal 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 reforming process of hydrocarbons to CO ₂ (known as dry reforming).

The Fischer-Tropsch process according to the invention is operated 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 invention is illustrated by the following examples which are in no way limiting in nature.

EXAMPLES

Example 1: Suspension A

In this example, the suspension is in the aqueous phase.

0.992 g of Co (NO ₃ ) ₂ .6H ₂ 0 (99%, Sigma Aldrich ™) is added in 1 L of distilled water. This solution is added to a double jacket glass reactor. 0.4 ml of ethanol (99.8%, Sigma Aldrich ™) and then 5.04 g of TiO ₂ nanoparticles (P25, Degussa ™) are then added with stirring to form a suspension.

The mixture is then left under stirring and under UV radiation for 7 hours. The lamp used to provide UV radiation is a 125W HPK ™ mercury vapor lamp. The reactor is thermostatically controlled at 25 ° C throughout the synthesis.

A suspension A is then obtained, consisting of a visually white powder. The powder in suspension A is called catalyst A.

Example 2: Suspension B

0.995 g of Co (N0 _{3) 2} .6H ₂ 0 (99%, Sigma Aldrich ™) was added in 1 L of ethanol (99.8%, Sigma Aldrich ™). This solution is added to a double jacket glass reactor. 5.01 g of TiO ₂ nanoparticles (P25, Degussa ™) are then added with stirring to form a suspension.

The mixture is then left under stirring for 7 hours. The reactor is obscured so that no irradiation reaches the reaction mixture. The reactor is thermostatically controlled at 25 ° C throughout the synthesis.

A suspension B is then obtained, consisting of a visually white powder. The powder in suspension B is called catalyst B.

Example 3: Suspension C

0.995 g of Co (N0 _{3) 2} .6H ₂ 0 (99%, Sigma Aldrich ™) was added in 1 L of ethanol (99.8%, Sigma Aldrich ™). This solution is added to a double jacket glass reactor. 5.00 g of TiO ₂ nanoparticles (P25, Degussa ™) are then added with stirring to form a suspension.

The mixture is then left under stirring and under UV radiation for 7:30. The lamp used to provide UV radiation is a 125W HPK ™ mercury vapor lamp. The reactor is thermostatically controlled at 25 ° C throughout the synthesis.

A suspension C is then obtained, consisting of a visually gray-black powder. The powder in suspension C is called catalyst C.

Example 4: Suspension D

0.900 g of Co (NO ₃ ) ₂ .6H ₂ 0 (99%, Sigma Aldrich ™) is added in 1 L of isopropanol (99.7%, Sigma Aldrich ™). This solution is added to a double jacket glass reactor. 5.04 g of TiO ₂ nanoparticles (P25, Degussa ™) are then added with stirring to form a suspension.

The mixture is then left under stirring and under UV radiation for 7 hours. The lamp used to provide UV radiation is a 125W HPK ™ mercury vapor lamp. The reactor is thermostatically controlled at 25 ° C throughout the synthesis.

A suspension D is then obtained, consisting of a visually gray-black powder. The powder in suspension D is called catalyst D.

Example 5: Suspension E

0.901 g of Co (NO ₃ ) ₂ .6H ₂ 0 (99%, Sigma Aldrich ™) is added to 985 ml of ethanol (99.8%, Sigma Aldrich ™). This solution is added to a double jacket glass reactor. 12.5 g of a commercial suspension of ZnO nanoparticles in ethanol (40% by weight of ZnO, Sigma Aldrich ™) are then added with stirring to form a suspension.

The mixture is then left under stirring and under UV radiation for 7 hours. The lamp used to provide UV radiation is a 125W HPK ™ mercury vapor lamp. The reactor is thermostatically controlled at 25 ° C while Icng of the synthesis.

A suspension E is then obtained, consisting of a visually gray-black powder. The powder in suspension E is called catalyst E.

Example 6: Suspension F

0.903 g of Co (NO ₃ ) ₂ .6H ₂ 0 (99%, Sigma Aldrich ™) is added in 1 L of isopropanol (99.7%, Sigma Aldrich ™). This solution is added to a double jacket glass reactor. 5.02 g of TiO ₂ particles of average size 45 μm (> 99%, Sigma Aldrich ™) are then added with stirring to form a suspension.

The mixture is then left under stirring and under UV radiation for 7 hours. The lamp used to provide UV radiation is a 125W HPK ™ mercury vapor lamp. The reactor is thermostatically controlled at 25 ° C while Icng of the synthesis.

This gives a suspension F, consisting of a visually gray-black powder. The powder in suspension F is called catalyst F.

Example 7: Catalytic performances of catalysts A to E in Fischer-Tropsch reaction in fixed bed reactor.

The suspensions A to E are centrifuged for 20 minutes at 8000 revolutions per minute in order to recover the catalysts A to E. Two washes with water are then carried out, each of the washes being followed by a centrifugation. The catalysts A to E recovered are then placed in an oven at 120 ° C for 12 hours.

Part of the catalysts A to E are removed for analysis by X-ray fluorescence of the metal cobalt content.

Catalysts A, B, C, D and E, before being tested in Fischer-Tropsch synthesis, are reduced in situ under a flow of pure hydrogen at 400 ° C for 16 hours. The Fischer-Tropsch synthesis reaction is carried out in a tubular reactor of the fixed bed type and operating continuously.

The Fischer-Tropsch synthesis conditions are as follows:

Temperature = 216 ° C;

Total pressure = 2 MPa;

Hourly volume speed (VVH) = 1800 NL / h ¹ /kg.catalyst;

H ₂ / CO molar ratio = 2/1.

The results, expressed in terms of activity (conversion of CO to%) and selectivity (mass percentage of C ₅ ⁺ hydrocarbons on all the products formed), as well as the cobalt contents measured by FX are shown in the table 1 below.

Table 1: catalytic performances of catalysts A to E in Fischer reaction

Tropsch in fixed bed reactor

Catalyst Conversion of CO at 70h under reaction flow (%) Selectivity in C ₅ ⁺ at 70 h under reaction flow (% by weight) Co content (metal,% weight) A (comparative) 0 n.d. (*) <0.01 B (comparative) 0 n.d. (*) <0.01 C (invention) 21.4 76.8 3.62 D (invention) 24.8 77.6 3.80 E (invention) 30.0 78.6 3.60

(*) = not detectable

The results appearing in Table 1 demonstrate that the catalysts according to the invention are active in Fischer-Tropsch synthesis and selective for the production of C ₅ ⁺ hydrocarbons.

Example 8: Catalytic performances in Fischer-Tropsch process of catalyst F in slurry reactor.

The suspension F is centrifuged for 20 minutes at 8000 revolutions per minute in order to recover the catalyst F.

Part of the catalyst F is removed for analysis by X-ray fluorescence of the metal cobalt content. Before analysis, two washes with water are carried out, each of the washes being followed by centrifugation. The solid recovered is then placed in an oven at 120 ° C for 12 hours. The dried solid is then assayed by X-ray fluorescence.

Without any step of thermal reduction of the catalyst, the remaining undried and unwashed part of catalyst F is coated in Sasolwax® to be stored in the absence of air before testing. The Fischer-Tropsch synthesis reaction is carried out in a slurry type reactor and operating continuously and operating with a concentration of 10% (vol) of catalyst in the slurry phase.

The catalyst is in the form of a powder with an average particle diameter of 45 μm.

The test conditions are as follows:

• Temperature = 230 ° C;

• Total pressure = 2MPa;

• H ₂ / CO molar ratio = 2.

The CO conversion is maintained between 45 and 50% throughout the duration of the test.

The test conditions are adjusted so as to be iso-conversion of CO whatever the activity of the catalyst.

The results were calculated for catalyst F in consumption of carbon monoxide in mol CO / g _cata i _yseLl r / h, as well as in selectivity towards the formation of C ₅ ⁺ hydrocarbons. The results are shown in Table 2 below.

Table 2: Catalytic performances of catalyst F in Fischer Tropsch reaction in slurry reactor

Catalyst CO consumption at 300h under reaction flow (mol CO / g _cata / h) Selectivity in C ₅ ⁺ at 300h under reaction flow (% by weight) Co content (metal,% weight) F (invention) 0.0054 79.7 3.53

The results appearing in Table 2 demonstrate that the catalysts according to the invention are active in Fischer Tropsch synthesis and selective for the production of C ₅ ⁺ hydrocarbons, and that the method of preparation according to the invention makes it possible to reduce the number of 'stage of catalyst synthesis since catalyst F is active in Fischer Tropsch synthesis without heat treatment step (drying, reduction, ...) post-synthesis.

Claims (15)

1. Process for the preparation by photo-assisted condensation of a composition comprising a support containing a semiconductor having on its surface particles of cobalt in the metallic state, which process comprises the following steps: a) providing a support containing a semiconductor and suspending it in a non-aqueous phase with stirring comprising a soluble cobalt precursor; b) the suspension obtained in step a) is irradiated with an irradiation source so that at least part of the emission spectrum of said irradiation source is composed of photons of energies greater than the prohibited bandwidth of said semiconductor; c) optionally, the composition of the suspension from step b) is at least partially separated; d) optionally, the composition obtained in step c) is dried; e) optionally, the dried composition obtained in step d) is subjected to a heat treatment. 2. Method according to claim 1, in which the semiconductor is chosen from an inorganic or organic-inorganic semiconductor. 3. Method according to claims 1 or 2, wherein the semiconductor is chosen from TiO ₂ , Ce ₂ O ₃ , CeO ₂ , WO ₃ , ZrO ₂ , CoTi0 ₃ , NiTiO ₃ , FeTiO ₃ , CuTiO ₃ , MnTiO ₃ , ZnTiO ₃ , ZnO, ZnFe ₂ O4, ZrO ₂ , CoAI ₂ 04, NiAI ₂ O4, FeAI ₂ O4, MnAI ₂ O4, Co ₂ Si04, Ni ₂ SiO ₂ , Fe ₂ SiO ₄ , AITiO _3i SiC alone or as a mixture . 4. Method according to any one of the preceding claims, in which the loading rate of the semiconductor in the non-aqueous phase is between 0.1 and 500 g / L. 5. Method according to any one of the preceding claims, in which the non-aqueous phase is chosen from alcohols, aldehydes or amines. 6. Method according to any one of the preceding claims, in which said particles in the metallic state of cobalt are in the form of particles of sizes between 0.5 nm and 1000 nm. 7. Method according to any one of the preceding claims, in which the soluble cobalt precursor is cobalt nitrate, cobalt acetate or a cobalt acetylacetonate. 8. Method according to any one of the preceding claims, in which the content of cobalt in the metallic state is between 0.1 and 40% by weight relative to the total weight of the composition. 9. Method according to any one of the preceding claims, in which the non-aqueous phase further comprises a sacrificial agent chosen from alcohols, aldehydes or amines. 10. The method of claim 9, wherein the molar ratio between the sacrificial agent and the cobalt precursor is greater than 1, preferably between 1 and 5. 11. Method according to any one of the preceding claims, in which the irradiation source is an artificial or natural irradiation source. 12. Method according to any one of the preceding claims, in which in step c), the separation is carried out by centrifugation. 13. Method according to any one of the preceding claims, in which in step d), the drying is carried out between 30 ° C and 2D0 ° C. 14. Method according to any one of the preceding claims, in which in step e), the dried composition obtained in step d) is subjected to a heat treatment under hydrogen at a temperature between 50 ° C and 500 ° C. , at an absolute pressure between 0.1 MPa and 1.5 MPa. 15. Use of the composition obtained by the process according to any one of claims 1 to 15 as a catalyst in a FischerTropsch synthesis process operating in the presence of synthesis gas under a total pressure of between 0.1 and 15 MPa, at a temperature between 150 and 350 ° C, at an hourly volume speed between 100 and 20,000 volumes of synthesis gas per volume of catalyst and per hour.