CO2 CONVERSION IN THE PRESENCE OF A COPPER AND INDIUM CATALYST

Abstract

Process for the hydrogenation of CO2 by reverse water gas reaction (RWGS) by contacting a feed of a gaseous mixture comprising CO2 and hydrogen with a catalyst comprising an active phase based on copper and indium, which process being carried out at a temperature between 0°C and 600°C, at a pressure between 0.1 MPa and 5 MPa, at a molar ratio of hydrogen / carbon dioxide between 0.1 and 10 and at an hourly volumetric rate between 100 h-1 and 40000 h-1.

Description

Title of the invention: CONVERSION OF CO2 IN THE PRESENCE OF A COPPER AND INDIUM CATALYST Technical field

[0001] The present invention relates to a process for reverse water gas shift (RWGS) in the presence of a bimetallic catalyst based on copper and indium. State of the art

[0002] Current solutions for reducing greenhouse gas emissions and combating global warming are varied and are the subject of much research in the academic and industrial worlds. Improving the energy efficiency of current processes, developing renewable energies, and capturing, storing, and using carbon dioxide (CO2) are examples.

[0003] CO2 is a thermodynamically very stable compound and its use in chemical products remains complex, although some examples exist. Examples include, at the industrial level, the synthesis of urea for the production of fertilizers or plastics, and at an advanced stage of research, the production of polycarbonates.

[0004] The hydrogenation of CO2 is an interesting recovery route which allows the production, depending on the operating conditions of the methanol, of carbon monoxide, which can themselves react and give access to a wide variety of compounds.

[0005] The reverse water gas shift reaction (also called here RWGS or Reverse Water Gas Shift according to the English terminology), makes it possible to transform CO2 into carbon monoxide (CO) in the presence of hydrogen. The main by-product of the hydrogenation of CO2 into CO is methane, the selectivity of which is favored at low temperature and in the presence of an excess of hydrogen. Oxide materials alone or mixed (spinels, CeO2, CuO / ZnO / Al2O3 composites), noble (Pt, Pd) or non-noble (Cu, Ni, Fe, Co) mono or bimetallic metals supported on generally reducible oxides (TiO2, ZrO2) are known to selectively catalyze the RWGS reaction (Chen et al. Frontiers in Chemistry, 8,709, 2020).

[0006] The RWGS reaction is reversible and endothermic. It is therefore thermodynamically favored at high temperature, generally above 600°C. However, operability at high temperature is expensive and significant deactivation of the catalysts is observed.

[0007] There is a need to develop active, selective and stable catalysts for CO2 conversion.

[0008] Copper is an active metal for RWGS but a stability deficit is noted during high temperature operation. To limit its deactivation, the use of aluminate or stabilization tests by the formation of bimetallic compounds are described in the literature.

[0009] Indium oxide In2O3 is described in the literature for its CO2 adsorption capacities, but the latter remains not very active for the RWGS reaction. Wang et al. improved the activity of indium oxide In2O3 for the RWGS reaction by adding cerium oxide CeO2 within the catalyst with an In2O3 content between 5 and 15% by weight relative to the total weight of the catalyst (cf. Wang, 2016, 259, 402-408, Catalysis Today). The CO2 conversion is at most 20% at 500°C. Stability is not mentioned. Davi et al. prepared a catalyst in the form of copper and indium nanocomposites with an In2O3 content of between 5 and 15% by weight relative to the total weight of the catalyst, i.e. a Cu / In molar ratio of between 11 and 33 mol / mol for the liquid electrochemical reduction of CO2 to CO at 25°C (cf. Catalysis Science Technology, 2019, 5339).

[0010] The research therefore concerns the development of active catalysts, operating at the lowest possible temperature, selective (in CO) and stable (with regard to the conversion of CO2).

[0011] Surprisingly, the Applicant has discovered that the use of a supported bimetallic catalyst whose active phase is based on copper and indium, according to a specific Cu / In ratio, makes it possible to significantly improve the conversion of CO2 into CO by RWGS while maintaining good selectivity. Objects of the invention

[0012] The present invention relates to a process for the hydrogenation of CO2 by reverse water gas reaction (RWGS) by bringing a charge of a gas mixture comprising CO2 and hydrogen into contact with a catalyst comprising an active phase based on copper and indium and a support comprising at least one refractory oxide, the copper content being between 0.5% and 25% by weight of copper element relative to the total weight of the catalyst, the atomic ratio between copper and indium being between 1 and 50 mol / mol, said support being in the form of a ball or an extrudate comprising a specific surface area of ​​between 20 m2 / g and 400 m2 / g, which process being carried out at a temperature of between 0°C and 600°C, at a pressure of between 0.1 MPa and 5 MPa, at a hydrogen / CO2 molar ratio of between 0.1 and 10 and at an hourly volumetric speed between 100 h 1 and 40000 h 1.

[0013] According to one or more embodiments according to the invention, the catalyst support is chosen from alumina, silica, and silica-alumina.

[0014] According to one or more embodiments according to the invention, said support is an extrudate comprising three lobes or four lobes.

[0015] According to one or more embodiments according to the invention, the indium content in the catalyst is between 0.02% and 25% by weight of indium element relative to the total weight of the catalyst.

[0016] According to one or more embodiments according to the invention, the atomic ratio between copper and indium is between 1 and 35 mol / mol.

[0017] According to one or more embodiments according to the invention, the catalyst comprises an alloy containing copper and indium.

[0018] According to one or more embodiments according to the invention, the size of the copper-indium alloy particles is between 3.5 nm and 100 nm.

[0019] According to one or more embodiments according to the invention, said catalyst is prepared according to a process comprising the following steps:

[0020] a) the support is brought into contact with a solution comprising at least one precursor of the active copper phase;

[0021] b) the support is brought into contact with at least one solution comprising at least one precursor of the active indium phase;

[0022] steps a) and b) being carried out separately, in any order, or simultaneously;

[0023] c) the catalyst precursor obtained at the end of steps a) and b) is dried at a temperature below 250°C.

[0024] According to one or more embodiments according to the invention, when steps a) and b) are carried out separately, an intermediate drying step is carried out between steps a) and b) in which the catalyst precursor obtained at the end of step a), or step b), is dried at a temperature below 250°C.

[0025] According to one or more embodiments according to the invention, the catalyst precursor obtained at the end of the intermediate drying step is subjected to a heat treatment at a temperature between 250°C and 1000°C.

[0026] According to one or more embodiments according to the invention, steps a) and b) are carried out simultaneously.

[0027] According to one or more embodiments according to the invention, the precursor of the active copper phase is chosen from copper acetate, copper acetylacetonate, copper nitrate, copper sulfate, copper chloride, copper bromide, copper iodide and copper fluoride.

[0028] According to one or more embodiments according to the invention, the precursor of the active indium phase is chosen from indium acetate, indium acetylacetonate, indium nitrate, indium sulfate, indium sulfide, indium chloride, indium mercaptoacetate, indium bromide, indium iodide, indium fluoride, indium oxide, indium phosphide, indium hydroxide. Detailed description of the invention Definitions

[0029] In the following, the groups of chemical elements are given according to the CAS classification (CRC Handbook of Chemistry and Physics, publisher CRC press, editor-in-chief DR Lide, 81st edition, 2000-2001). For example, group IIIA according to the CAS classification corresponds to the metals of column 13 according to the new IUPAC classification.

[0030] The BET specific surface area is measured by nitrogen physisorption. The BET specific surface area is measured by nitrogen physisorption according to ASTM D3663-03 as described in Rouquerol F.; Rouquerol J.; Singh K. “Adsorption by Powders & Porous Solids: Principle, methodology and applications”, Academie Press, 1999.

[0031] The total pore volume is measured by mercury porosimetry according to ASTM D4284-92 with a wetting angle of 140°, for example using an Autopore® III model device from Microméritics®.

[0032] The term "copper-indium alloy particle size" refers to the diameter of the copper-indium crystallites in oxide form. The crystallite diameter is determined by X-ray diffraction, from the width of the diffraction line located at the angle 2theta=43° (i.e., along the crystallographic direction

[200] ) using the Scherrer relationship. This method, used in X-ray diffraction on powders or polycrystalline samples, which relates the width at half-height of the diffraction peaks to the particle size, is described in detail in the reference: Appl. Cryst. (1978), 11, 102-113 "Scherrer after sixty years: A survey and some new results in the determination of crystallite size", JI Langford and AJC Wilson.

[0033] The copper and indium contents are measured by X-ray fluorescence.

[0034] In the present description, the term "comprise" is synonymous with (means the same as) "include" and "contain", and is inclusive or open and does not exclude other elements not recited. It is understood that the term "comprise" includes the exclusive and closed term "consist". Furthermore, in the present description, the term "substantially" corresponds to an approximation of ± 10%, preferably ± 5%, very preferably ± 2%, of a reference value such as a distance, a speed, a flow rate, a compound content, a temperature, a pressure, etc. 1. CO2 hydrogenation process by RWGS

[0035] The subject of the present invention is a process for the hydrogenation of CO2 by reverse water gas reaction (RWGS) by bringing a charge of a gas mixture comprising CO2 and hydrogen into contact with a catalyst comprising an active phase based on copper and indium and a support comprising at least one refractory oxide, the copper content being between 0.5% and 25% by weight of element copper per relative to the total weight of the catalyst, the atomic ratio between copper and indium being between 1 and 50 mol / mol, said support being in the form of a ball or an extrudate comprising a specific surface area of ​​between 20 m2 / g and 400 m2 / g, which process is carried out at a temperature of between 0°C and 600°C, at a pressure of between 0.1 MPa and 5 MPa, at a hydrogen / CO2 molar ratio of between 0.1 and 10 and at an hourly volumetric velocity of between 100 h 1 and 40,000 h1.

[0036] In the process according to the invention, CO2 is selectively hydrogenated to CO by RWGS reaction in the presence of a specific catalyst as described below. The effluents contain CO, water, and optionally unconverted hydrogen and CO2. By-products of the reaction, such as methane, methanol or other alcohols, alkenes, ethers and / or alkanes may also be present in the effluent from the RWGS reaction. The charge

[0037] The CO2 contained in the gas mixture feed can come from various sources. The necessary CO2 can be provided by a unit for separating a stream comprising CO2 (e.g. combustion fumes) or a CO2 capture unit (e.g. CO2 present in the air).

[0038] The hydrogen required for the conversion of CO2 can be produced by a water electrolysis unit, said water being able to come from the effluent of the RWGS reaction unit and optionally from downstream units (for example Fischer-Tropsch (FT) or alcohol synthesis units). Preferably, the use of the water electrolysis unit to treat the water produced by the RWGS reaction unit also makes it possible to minimize the environmental impact of the process. Thus, the process according to the invention does not require an external supply of hydrogen, for example produced by steam reforming of natural gas. The electrolyzer can preferably operate with low-carbon electricity, which contributes to the renewable nature of the synthesis gas and the hydrocarbons which will then be produced from this synthesis gas.Furthermore, the water used for hydrogen production can come at least in part from the recycling of water produced by the RWGS reaction, which has the advantage of limiting the external water supply.

[0039] The hydrogen / CO2 molar ratio is preferably between 0.1 and 10, preferably between 0.5 and 5, more preferably between 1 and 3, and even more preferably between 1 and 2.

[0040] The gas mixture constituting the charge may contain, in addition to CO2 and hydrogen, other gaseous elements such as water vapor, alkanes such as methane, propane and / or isobutane. Implementation

[0041] The technological implementation of the RWGS process is for example carried out by injection, in ascending or descending flow, of the feedstock, i.e. the gas mixture comprising CO2 and hydrogen, into at least one fixed-bed or fluid-bed reactor. Preferably, the reactor is a fixed-bed reactor. Said reactor may be of the isothermal type or of the adiabatic type. An adiabatic reactor is preferred.

[0042] The feedstock can advantageously be diluted by one or more reinjections of the effluent, from said reactor where the selective hydrogenation reaction takes place, at various points in the reactor, located between the inlet and the outlet of the reactor in order to limit the temperature gradient in the reactor.

[0043] In one embodiment according to the invention, the RWGS reaction is carried out with a hydrogen / CO2 molar ratio of between 0.1 and 10, preferably between 0.5 and 5, more preferably between 1 and 3, and even more preferably between 1 and 2, a temperature of between 0°C and 600°C, preferably between 25°C and 600°C, and even more preferably between 30°C and 550°C, an hourly volumetric velocity (HVV) of between 100 h 1 and 40000 h1, preferably between 2000 h 1 and 20000 h1, and a pressure of between 0.1 MPa and 5.0 MPa, preferably between 0.1 MPa and 4.0 MPa, and even more preferably between 0.1 MPa and 3.0 MPa.

[0044] Preferably, the catalyst is pre-heat-treated in the reactor under a reducing atmosphere before injecting the feedstock, at a temperature between 100°C and 600°C, preferably between 150°C and 500°C and for a duration between 30 minutes and 12 hours. 2. Catalyst

[0045] The catalyst used in the context of the process according to the invention comprises, preferably consists of, an active phase comprising copper and indium, and a support comprising at least one refractory oxide, the copper content being between 0.5% and 25% by weight of copper element relative to the total weight of the catalyst, the atomic ratio between copper and indium being between 1 and 50 mol / mol, said support being in the form of a ball or an extrudate comprising a specific surface area of ​​between 20 m2 / g and 400 m2 / g.

[0046] The copper content in the catalyst is between 0.5% and 25% by weight of copper element relative to the total weight of the catalyst, preferably between 1 and 20% by weight, more preferably between 2 and 18% by weight, more preferably between 3 and 15% by weight, and even more preferably between 5 and 15% by weight.

[0047] The indium content in the catalyst is preferably between 0.02% and 25% by weight of indium element relative to the total weight of the catalyst, preferably between 0.05% and 20% by weight, and even more preferably between 0.1% and 15% by weight.

[0048] The atomic ratio between copper and indium is between 1 and 50 mol / mol, preferably between 1 and 45 mol / mol, and more preferably between 1 and 40 mol / mol, and even more particularly between 1 and 35 mol / mol.

[0049] According to one or more embodiments, the copper is distributed homogeneously throughout the shaped support.

[0050] According to one or more embodiments, the indium is distributed homogeneously throughout the shaped support.

[0051] In one embodiment according to the invention, the catalyst may preferably contain the presence of an alloy containing copper and indium. In this embodiment, the size of the copper-indium alloy particles is advantageously between 3.5 nm and 100 nm, preferably between 4 nm and 50 nm.

[0052] The specific surface area of ​​the catalyst is advantageously between 20 m2 / g and 400 m2 / g, preferably between 30 m2 / g and 350 m2 / g, more preferably between 40 m2 / g and 320 m2 / g, more preferably between 50 m2 / g and 310 m2 / g, and even more preferably between 80 m2 / g and 300 m2 / g.

[0053] The total pore volume (TPV) of the catalyst is advantageously between 0.1 cmVg and 1.5 cmVg, preferably between 0.2 cmVg and 1.4 cmVg, and even more preferably between 0.25 cmVg and 1.3 cmVg. 3. Support

[0054] The catalyst support used in the process according to the invention comprises at least one refractory oxide, preferably chosen from alumina, silica-alumina and silica. Preferably, the support is alumina.

[0055] When the support is based on alumina, it is understood that it comprises at least 95%, preferably at least 98%, and particularly preferably at least 99% by weight of alumina relative to the weight of the support. The alumina generally has a crystallographic structure of the delta, gamma or theta alumina type, alone or as a mixture.

[0056] When the support is silica-based, it is understood that it comprises at least 95%, preferably at least 98%, and particularly preferably at least 99% by weight of silica relative to the weight of the support. The silica generally has an amorphous crystallographic structure, but may contain crystalline silica quartz, tridymite, cristobalite alone or in a mixture. The silica may be fused silica.

[0057] When the support is based on silica-alumina, the silica content is between 1 and 95% by weight, preferably between 5 and 90% and more preferably between 10 and 80% by weight relative to the total weight of the support. The alumina content is between 1 and 95% by weight, preferably between 5 and 90% by weight and more preferably between 10 and 80% by weight relative to the total weight of the support. The silica-alumina can be prepared by any method known to those skilled in the art. such as the sol-powder, sol-gel, co-precipitation, or co-gelation method. Depending on its preparation method, silica-alumina contains domains of amorphous crystallographic structure and delta, gamma or theta alumina type, alone or in a mixture.

[0058] The silica, alumina, or silica-alumina-based support may comprise impurities such as metal oxides from groups IIA, IIIB, IVB, IIB, IIIA, IVA according to the CAS classification, preferably alumina, titanium dioxide, zirconium dioxide, zinc oxide, magnesium oxide and calcium oxide, or alkali metals, preferably lithium, sodium or potassium, and / or alkaline earth metals, preferably magnesium, calcium, strontium or barium or sulfur.

[0059] The specific surface area of ​​the support is between 20 m2 / g and 400 m2 / g, preferably between 30 m2 / g and 350 m2 / g, more preferably between 40 m2 / g and 320 m2 / g, more preferably between 50 m2 / g and 310 m2 / g, and even more preferably between 80 m2 / g and 300 m2 / g.

[0060] The total pore volume (TPV) of the support is advantageously between 0.1 cm3 / g and 1.5 cmVg, preferably between 0.2 cmVg and 1.4 cmVg, and even more preferably between 0.25 cmVg and 1.3 cmVg.

[0061] The support is either in the form of balls or in the form of extrudates, advantageously of trilobal or quadrilobal shape. When the support is in the form of balls, the diameter of the balls is generally between 1 mm and 10 mm, preferably between 2 mm and 8 mm, and even more preferably between 2 mm and 6 mm. When the support is in the form of an extrudate of quadrilobal type, the length of the extrudate is generally between 2 mm and 10 mm, preferably between 2 mm and 8 mm, and more preferably between 3 mm and 6 mm. When the support is in the form of a quadrilobe type extrudate, the extrudates have a diameter generally between 0.5 mm and 10 mm, preferably between 0.8 mm and 3.2 mm and very preferably between 1.0 mm and 2.5 mm and a length between 0.5 and 2.0 mm.

[0062] The support can advantageously be shaped by any technique known to those skilled in the art. The shaping can be carried out for example by kneading-extrusion, by the oil-drop coagulation method, by granulation on a rotating plate or by any other method well known to those skilled in the art. The catalysts are manufactured and used in the form of extrudates or beads. The advantageous shaping method according to the invention is extrusion and the preferred extrudate shapes are trilobal or quadrilobal shapes. 4. Preparation of the catalyst

[0063] The catalyst used in the process according to the invention can be prepared according to a catalyst preparation process comprising the following steps:

[0064] a) the support is brought into contact with a solution comprising at least one precursor of the active copper phase;

[0065] b) the support is brought into contact with at least one solution comprising at least one precursor of the active indium phase;

[0066] steps a) and b) being carried out separately, in any order, or simultaneously;

[0067] c) the catalyst precursor obtained at the end of steps a) and b) is dried at a temperature below 250°C. Implementation of steps a) and b)

[0068] Said step a) is characterized in that the contacting of the support with a solution containing a precursor of the active copper phase can be carried out by impregnation, dry or in excess, or by deposition-precipitation, according to methods well known to those skilled in the art. The pH of said solution can be modified by the possible addition of an acid or a base.

[0069] Said step a) is preferably carried out by impregnation of the support consisting for example of bringing the support into contact with at least one aqueous solution containing a copper precursor.

[0070] Preferably, said step a) is carried out by dry impregnation, which consists of bringing the support into contact with at least one solution, containing, preferably consisting of, at least one copper precursor, the volume of the solution of which is between 0.25 and 1.5 times the pore volume of the support to be impregnated.

[0071] The copper precursor salt is preferably selected from copper acetate, copper acetylacetonate, copper nitrate, copper sulfate, copper chloride, copper bromide, copper iodide or copper fluoride.

[0072] Preferably, the copper precursor salt is selected from copper nitrate, copper sulfate or copper chloride.

[0073] The concentration of copper in solution is adjusted according to the type of impregnation (dry or excess impregnation) and the pore volume of the support so as to obtain for the supported catalyst, a copper content of between 0.5% and 25% by weight of copper element relative to the total weight of the catalyst, preferably between 1% and 20% by weight, more preferably between 2% and 18% by weight, more preferably between 3% and 15% by weight, even more preferably between 5% and 15% by weight.

[0074] Said step b) is characterized in that the contacting of the support with a solution containing a precursor of the active indium phase, in accordance with the implementation of step b), can be carried out by impregnation, dry or in excess, or still by deposition - precipitation, according to methods well known to those skilled in the art.

[0075] Said step b) is preferably carried out by impregnation of the shaped support, consisting for example of bringing the support into contact with at least one aqueous solution containing an indium precursor. The pH of said solution can be modified by the possible addition of an acid or a base.

[0076] Preferably, said step b) is carried out by dry impregnation, which consists of bringing the support into contact with at least one solution, containing, preferably consisting of indium, the volume of the solution of which is between 0.25 and 1.5 times the pore volume of the support to be impregnated.

[0077] The precursor of the active phase based on indium is preferably chosen from indium acetate, indium acetylacetonate, indium nitrate, indium sulfate, indium sulfide, indium chloride, indium mercaptoacetate, indium bromide, indium iodide, indium fluoride, indium oxide, indium phosphide, indium hydroxide.

[0078] The concentration of indium solution is adjusted according to the type of impregnation (dry or excess impregnation) and the pore volume of the support so as to obtain for the supported catalyst, an indium content of between 0.02% and 25% by weight relative to the total weight of the catalyst, preferably between 0.05 and 20% by weight, more preferably between 0.1 and 15% by weight.

[0079] Similarly, the concentration of indium in solution is supplied so that the atomic ratio between copper and indium is between 1 and 50 mol / mol, preferably between 1 and 45 mol / mol, and more preferably between 1 and 40 mol / mol, and even more particularly between 1 and 35 mol / mol.

[0080] When steps a) and b) are carried out separately, an intermediate drying step is carried out between steps a) and b), or between steps b) and a), in which the catalyst precursor obtained at the end of step a), or step b), is dried at a temperature below 250°C, preferably between 70°C and 200°C. The drying time is generally between 0.5 hours and 20 hours. Longer times are not excluded, but do not necessarily provide an improvement.

[0081] Drying is generally carried out under combustion air of a hydrocarbon, preferably methane, or under heated air comprising between 0 and 80 grams of water per kilogram of combustion air, an oxygen level of between 5% and 25% by volume and a CO2 level of between 0% and 10% by volume.

[0082] Optionally, the catalyst precursor obtained at the end of the intermediate drying step is subjected to a heat treatment in air, preferably combustion air, and more preferably methane combustion air, comprising between 40 grams and 80 grams of water per kg of air, an oxygen level of between 5% and 15% by volume and a CO2 content of between 4% and 10% by volume. The calcination temperature is generally between 250°C and 900°C, preferably between about 300°C and about 500°C. The calcination time is generally between 0.5 hours and 5 hours. The hourly volumetric velocity (HVV) is generally between 150 and 3000, preferably between 300 and 1500 liters of combustion air per hour and per liter of catalyst.

[0083] In another embodiment, steps a) and b) are carried out simultaneously. In this case, the impregnated support can be dried during step c). Step c): drying the impregnated support

[0084] Step c) of drying the catalyst precursor obtained at the end of the sequence of steps a) and b) is carried out at a temperature below 250°C, preferably between 15 and 180°C, more preferably between 30 and 160°C, even more preferably between 50 and 150°C, and even more preferably between 70 and 140°C, typically for a period of between 10 minutes and 24 hours. Longer periods are not excluded, but do not necessarily provide an improvement.

[0085] The drying step can be carried out by any technique known to those skilled in the art. It is advantageously carried out under an inert atmosphere or under an atmosphere containing oxygen or under a mixture of inert gas and oxygen. It is advantageously carried out at atmospheric pressure or at reduced pressure. Preferably, this step is carried out at atmospheric pressure and in the presence of air or nitrogen.

[0086] Heat treatment of the dried catalyst (optional}

[0087] Optionally, after drying (step c)), the catalyst is calcined in air, preferably combustion air, and more preferably methane combustion air, comprising between 40 grams and 80 grams of water per kg of air, an oxygen level of between 5% and 15% by volume and a CO2 level of between 4% and 10% by volume. The calcination temperature is generally between 250°C and 900°C, preferably between approximately 300°C and approximately 500°C. The calcination time is generally between 0.5 hours and 5 hours. The hourly volumetric velocity (HVV) is generally between 150 and 3000, preferably between 300 and 1500 liters of combustion air per hour and per liter of catalyst. Reduction by reducing gas (optional)

[0088] Optionally, the catalyst is reduced. This step is preferably carried out in the presence of a reducing gas, either in situ, i.e. in the reactor where the catalytic transformation is carried out, or ex situ. Preferably, this step is carried out at a temperature between 100°C and 600°C, even more preferably between 120°C and 500°C.

[0089] The reduction is carried out in the presence of a reducing gas comprising between 25% vol and 100% vol of hydrogen, preferably 100% volume of hydrogen. The hydrogen is optionally supplemented by an inert gas for the reduction, preferably argon, nitrogen or methane.

[0090] The reduction generally includes a temperature increase phase followed by a plateau.

[0091] The duration of the reduction stage is generally between 1 hour and 10 hours, preferably between 2 hours and 8 hours.

[0092] The Hourly Volumetric Velocity (HVV) is generally between 150 and 3000, preferably between 300 and 1500 liters of reducing gas per hour and per liter of catalyst. Examples

[0093] The invention will now be illustrated via the following examples which are in no way limiting.

[0094] Example 1: Preparation of an AL-1 alumina extrudate

[0095] An alumina gel is synthesized via a mixture of sodium aluminate and aluminum sulfate. The precipitation reaction is carried out at a temperature of 60°C, at a pH of 9, for 60 minutes and with stirring at 200 rpm.

[0096] The gel thus obtained is mixed on a Z-arm mixer to provide the paste. Extrusion is carried out by passing the paste through a die provided with orifices of diameter 1.6 mm in the shape of a trilobe. The extrudates thus obtained are dried at 150°C for 12 hours and then calcined at 450°C under a flow of dry air for 5 hours. The dry air used in this example and in all the examples below contains less than 5 grams of water per kilogram of air.

[0097] The AL-1 alumina support has a specific surface area of ​​200 m2 / g, a pore volume (determined by mercury porosimetry) of 0.85 mL / g and a median mesoporous diameter of 15 nm. The sodium content is 0.0350% by weight and the sulfur content is 0.15% by weight relative to the total weight of the support.

[0098] Example 2: preparation of a 10% Cu / AL-1 catalyst

[0099] 12.2 g of hydrated copper nitrate (Cu(NO3)2; 2.5 H2O, M=232.56 g / mol, 5.24 mmol) are dissolved in 21 mL of deionized water at room temperature. The solution is then added dropwise to 30 g of shaped support AL-1 in a rotating dragee at room temperature. The material is dried for 16 h in air at 120°C then calcined for 2 h at 400°C under air flow.

[0100] Catalyst A comprises a copper element content of 10% by weight relative to the total weight of the catalyst.

[0101] Example 3: preparation of a catalyst 6.1% by weight of In / AL-1

[0102] 6.7 g of hydrated indium nitrate (In(NO3)3; 5 H2O, M=391 g / mol, 1.71 mmol) are dissolved in 21 mL of deionized water at room temperature. The solution is then added dropwise to 30 g of AL-1 shaped support in a rotating dragee at room temperature. The material is dried for 12 h in air at 60°C then calcined for 2 h at 400°C under air flow.

[0103] Catalyst B comprises an indium element content of 6.1% by weight relative to the total weight of the catalyst.

[0104] Example 4: preparation of a 9.9%Cu 0.5% In / AL-1 catalyst (mol / mol Cu / In ratio = 55. non-compliant) by co-impregnation

[0105] 0.37 g of hydrated indium nitrate (In(NO3)3;5 H2O, M=391 g / mol, 0.095 mmol) and 12.2 g of hydrated copper nitrate (Cu(NO3)2; 2.5 H2O, M=232.6 g / mol, 5.24 mmol) are dissolved in 21 mL of deionized water at room temperature. The solution is then added dropwise to 30 g of shaped support AL-1 in a rotating drageoir at room temperature. The material is dried for 16 h in air at 120°C and then calcined for 2 h at 400°C under air flow.

[0106] Catalyst C comprises a copper element content of 9.9% by weight relative to the total weight of the catalyst and an indium content of 0.33% by weight relative to the total weight of the catalyst. The Cu / In molar ratio is 55 mol / mol.

[0107] Example 5: preparation of a 9.2% wt. Cu 7.6% wt. In / AL-1 catalyst (mol / mol Cu / In ratio = 2.2. compliant) by co-impregnation

[0108] 9.3 g of hydrated indium nitrate (In(NO3)3; 5 H2O, M=391 g / mol, 2.37 mmol) and 12.2 g of hydrated copper nitrate (Cu(NO3)2; 2.5 H2O, M=232.6 g / mol, 5.24 mmol) are dissolved in 21 mL of deionized water at room temperature. The solution is then added dropwise to 30 g of shaped support AL-1 in a rotating drageoir at room temperature. The material is dried for 16 h in air at 120°C and then calcined for 2 h at 400°C under air flow.

[0109] Catalyst D comprises a copper element content of 9.2% by weight relative to the total weight of the catalyst and an indium content of 7.6% by weight relative to the total weight of the catalyst. The Cu / In molar ratio is 2.2 mol / mol.

[0110] Example 6: preparation of a 9.9%Cu 0.5% In / AL-1 catalyst (mol / mol ratio Cu / In = 33. compliant) by co-impregnation

[0111] 0.6 g of hydrated indium nitrate (In(NO3)3;5 H2O, M=391 g / mol, 0.15 mmol) and 12.2 g of hydrated copper nitrate (Cu(NO3)2; 2.5 H2O, M=232.6 g / mol, 5.24 mmol) are dissolved in 21 mL of deionized water at room temperature. The solution is then added dropwise to 30 g of shaped support AL-1 in a rotating drageoir at room temperature. The material is dried for 16 h in air at 120°C and then calcined for 2 h at 400°C under air flow.

[0112] Catalyst E comprises a copper element content of 9.9% by weight relative to the total weight of the catalyst and an indium content of 0.5% by weight relative to the total weight of the catalyst. The Cu / In molar ratio is 33 mol / mol.

[0113] Example 7: Catalytic tests: performance in hydrogenation of carbon dioxide

[0114] Catalysts A to E described in the examples above are tested for the CO2 hydrogenation reaction by RWGS.

[0115] The catalysts are tested with an Avantium® unit comprising 16 stainless steel reactors in parallel, with an internal diameter of 2 mm and a length of 560 mm. The reaction is carried out in the gas phase, at a pressure of 1.2 bar absolute (0.12 MPaa). The feed gases are CO2 and hydrogen with an H2 / CO2 molar ratio of 1.1. The gases (CO2) and H2 are co-injected in down-flow and mixed upstream of the reactor head. The feed is heated in the first part of the reactor. The catalyst is loaded in the form of extrudates with a diameter of 1.6 mm. The mass of catalyst loaded is 100 mg per reactor, corresponding to a loading height of 6 cm to 15 cm depending on the catalyst.

[0116] At the unit outlet, the products are analyzed by gas chromatography.

[0117] The products observed are mainly carbon monoxide (CO), hydrogen H2, unconverted carbon dioxide (CO2), methanol (CH3OH), methane (CH4), and traces of hydrocarbon products (alkenes, alkanes) and alcohols other than methanol.

[0118] The performance of the catalyst is defined by the conversion to CO2 and the selectivity to CO.

[0119] The conversion to CO2 is defined according to the following formula:

[0120] CO2 Conversion (%) = 100 x [Q (CO2) in - Q (CO2) out] / [Q (CO2) in]

[0121] with: - Q (CO2)inlet ■ molar flow rate of CO2 inlet in NmL / min - Q (CO2)output: molar flow rate of CO2 output in NmL / min

[0122] The molar selectivity in CO (also called here SCO) is defined according to the following formula:

[0123] SCO (%) = Q (CO) output / (Q (CO2) input - Q (CO2) output)

[0124] For each test, the catalysts are treated at atmospheric pressure at 300°C, for 4 hours with a hydrogen flow rate of 12.5 NmL / min per reactor, i.e. a VVH of 10,000 h1.

[0125] The molar mixture charge H2 / CO2 = 1.1 is then injected into the reactor at 350°C for 48 h with a gas flow rate of 12.5 NmL / min per reactor, i.e. a VVH of 10,000 h A

[0126] The temperature is then increased to 500°C with a ramp of 300°Ch 1 for a duration of 72 hours.

[0127] A first series of tests is carried out on catalysts A to E. The results are shown in Table 1 below.

[0128] [Tableauxl] Catalyst description Conversion (%) Deactivation (% / h) Sco(%) Catalysts Cu content (wt.%) In content (wt.%) Cu / In (mol / mol) D 60 h 80 h 200 h 80 h A (non-compliant) 10 0 - 38 20 (2.4) 10 (0.7) 99 B (non-compliant) 0 6.1 - 5 2 (3) 2 (0) Not determined C (non-compliant) 9.4 0.33 55 35 20 (2.1) 12 (0.6) 99 D (compliant) 9.4 7.6 2.2 20 20 (0) 18 (0.1) 99 E (compliant) 9.5 0.5 33 20 15 (1.25) 15 (0) 98

[0129] Table 1: Comparison of the performances of catalysts A to E in selective hydrogenation of CO2 to CO.

[0130] The monometallic catalyst B (non-compliant) comprising only indium is not very active for the CO2 conversion reaction at 500°C whereas catalyst A, composed only of copper, is very active with a conversion of 38% at the start of the cycle at 350°C.

[0131] All active catalysts A, C, D and E are selective for CO production with a selectivity of 98%.

[0132] Catalysts D and E, in accordance with the invention, convert CO2 with conversions of 20%. The addition of indium reduces the activity at the start of the cycle. This reduction is all the more significant as the indium content is high. However, it is observed that the addition of indium in a certain proportion makes it possible to limit or even cancel the deactivation of the catalyst under load. Indeed, catalyst A, monometallic copper, sees its conversion fall from 50% at 60 h under load to 20% at 80 h under load and 10% at 200 h under load.

[0133] Catalyst D (conformal) with a Cu / In ratio of 2.2 mol / mol has a slope of almost zero deactivation. Conversion remains stable at 20%. For catalyst E (compliant) with a lower indium content (Cu / In ratio of 33 mol / mol), deactivation is observed between 60 h and 80 h with a decrease of 20% to 18% in conversion. Then, the catalyst conversion remains stable. For catalyst C (non-compliant) with an even lower indium content (Cu / In ratio of 55 mol / mol), it is observed that the addition of indium in such a proportion no longer has any effect on the stability of the catalyst over time (conversion of 12% after 200 h).

[0134] Catalysts D and E used in the process according to the invention are therefore active and stable. The addition of indium in a certain proportion makes it possible to gain stability with isoselectivity in CO for the hydrogenation of CO2.

Claims

Claims

1. A process for the hydrogenation of CO2 by reverse water gas reaction (RWGS) by contacting a feedstock of a gas mixture comprising carbon dioxide and hydrogen with a catalyst comprising an active phase based on copper and indium and a support comprising at least one refractory oxide, the copper content being between 0.5% and 25% by weight of copper element relative to the total weight of the catalyst, the atomic ratio between copper and indium being between 1 and 50 mol / mol, said support being in the form of a ball or an extrudate comprising a specific surface area of ​​between 20 m2 / g and 400 m2 / g, which process being carried out at a temperature of between 0°C and 600°C, at a pressure of between 0.1 MPa and 5 MPa, at a hydrogen / carbon dioxide molar ratio of between 0.1 and 10 and at a hourly volumetric speed between 100 h 1 and 40000 h 1.

2. The method of claim 1, wherein the catalyst support is selected from alumina, silica, and silica-alumina.

3. A method according to either of claims 1 or 2, wherein said support is an extrudate having three lobes or four lobes.

4. A method according to any one of claims 1 to 3, wherein the indium content in the catalyst is between 0.02% and 25% by weight of indium element relative to the total weight of the catalyst.

5. A method according to any one of claims 1 to 4, wherein the atomic ratio between copper and indium is between 1 and 35 mol / mol.

6. A method according to any one of claims 1 to 5, wherein the catalyst comprises an alloy containing copper and indium.

7. The method of claim 6, wherein the size of the copper-indium alloy particles is between 3.5 nm and 100 nm.

8. Process according to any one of claims 1 to 7, wherein said catalyst is prepared according to a process comprising the following steps: a) the support is brought into contact with a solution comprising at least one precursor of the active copper phase; b) the support is brought into contact with at least one solution comprising at least one precursor of the active indium phase; steps a) and b) being carried out separately, in any order, or simultaneously; c) the catalyst precursor obtained at the end of steps a) and b) is dried at a temperature below 250°C.

9. Method according to claim 8, wherein when steps a) and b) are carried out separately, an intermediate drying step is carried out between steps a) and b) in which the catalyst precursor obtained at the end of step a), or step b), is dried at a temperature below 250°C.

10. Method according to claim 9, in which the catalyst precursor obtained at the end of the intermediate drying step is subjected to a heat treatment at a temperature between 250°C and 1000°C.

11. A method according to claim 8, wherein steps a) and b) are carried out simultaneously.

12. A method according to any one of claims 8 to 11, wherein the precursor of the active copper phase is selected from copper acetate, copper acetylacetonate, copper nitrate, copper sulfate, copper chloride, copper bromide, copper iodide and copper fluoride.

13. A method according to any one of claims 8 to 12, wherein the precursor of the active indium phase is selected from indium acetate, indium acetylacetonate, indium nitrate, indium sulfate, indium sulfide, indium chloride, indium mercaptoacetate, indium bromide, indium iodide, indium fluoride, indium oxide, indium phosphide, indium hydroxide.