Bifunctional material and use thereof in a method for capturing and converting carbon dioxide

Abstract

The present invention relates to a method for capturing carbon dioxide (CO2) and converting it into C1 to C3 chemical compounds, characterised in that it comprises the following steps: - placing a bifunctional material in contact with a flow comprising carbon dioxide in order to capture the carbon dioxide using the bifunctional material; and - placing the bifunctional material having captured the carbon dioxide in contact with a hydrogen flow in order to convert the carbon dioxide into at least one C1 to C3 chemical compound selected from the group comprising methanol, methane, carbon monoxide, formic acid, ethylene, dimethyl ether and propylene, the compound preferably being methanol, the bifunctional material consisting of a sorbent and a catalyst, the sorbent being capable of capturing the carbon dioxide by physical adsorption, the catalyst being capable of converting the carbon dioxide into at least one C1 to C3 chemical compound and preferably capable of reducing the carbon dioxide to methanol, the catalyst not comprising any support other than the sorbent, the catalyst being positioned at the surface of the sorbent, the method being further characterised in that the flow comprising the carbon dioxide is an air flow or a flue gas flow. The invention also relates to a bifunctional material for capturing carbon dioxide and then converting it into at least one C1 to C3 chemical compound, as well as to a method for preparing the bifunctional material.

Description

Description Title: Bifunctional material and its use in a carbon dioxide capture and conversion process Technical field

[0001] The present invention relates to the field of chemistry. It relates in particular to a bifunctional material which makes it possible to both capture carbon dioxide (CO2) and then convert it into useful products, and in particular into methanol. The invention also relates to a method for capturing and converting carbon dioxide (CO2) using said bifunctional material. Prior art

[0002] The CO2 recovery chain is characterized by all the steps involved in capturing this element and converting it into useful products, thus contributing to reducing greenhouse gas emissions, combating climate change and promoting the transition to a more sustainable economy. Indeed, once CO2 has been recovered and transformed into useful products, these products can be commercialized and distributed on the market, thus creating a new source of income and stimulating the circular economy. However, this recovery chain is still under development and requires improvements, in particular to limit the high costs of capture and conversion as well as the environmental impact of the process (high energy intensity of the CO2 capture and conversion process).

[0003] The first crucial step in the CO2 recovery chain is its capture. CO2 capture can be carried out (1) at concentrated points (“point-source”), i.e. at the exit of industrial chimneys or in a specific industrial process, or (2) directly in the air. Capture at concentrated points consists of recovering CO2 from the fumes resulting from industrial processes or the combustion of fossil fuels. Direct air capture makes it possible to capture CO2 directly from the atmosphere. Conventional CO2 capture techniques, whether performed at concentrated points or directly from the air, include chemical absorption and / or physical adsorption. Chemical absorption is one of the most commonly used methods for capturing CO2, particularly in the context of concentrated point capture. It involves the use of chemical solvents to absorb CO2, such as ammonia, monoethanolamine, diethanolamine, methyl diethanolamine, and other amines. The CO2 is captured in the solvent and then separated from the solvent by a desorption step, usually carried out by increasing temperature, which allows the CO2 to be released and stored. Physical adsorption of CO2 involves the use of specific porous materials such as activated carbon, mesoporous silicas, polymeric membranes or metal oxides (MgO, CaO). These porous materials can be functionalized with compounds that capture CO2, such as amine compounds. After adsorption of CO2 by the porous material, the CO2 can be released by applying pressure reduced or increased temperature. The CO2 thus captured is pure CO2 in the sense that it has been isolated from other components present in the air or in industrial chimney fumes. Regardless of the technique used, once the CO2 is captured by a facility, it must be compressed and transported to conversion facilities, which generally constitute a second, separate processing unit. Alternatively, the CO2 can be transported to long-term storage sites (over 100 years) for "disposal."

[0004] The second step in the CO2 recovery chain involves converting captured CO2 into value-added products such as methanol, carbon monoxide, methane, and ethylene. The most common technologies for CO2 conversion are thermal catalysis, electrocatalysis, and biological conversion. Regarding thermal catalysis technology, the most commonly used catalysts for CO2 conversion include: - copper-zinc-aluminum catalysts, which are widely used in the reduction of CO2 to methanol and are often mixtures of copper, zinc and aluminum supported on materials such as alumina; - copper complex catalysts, which are generally organometallic complexes comprising organic ligands which stabilize the copper complex, said catalysts also facilitating the reduction of CO2 to methanol; - noble metal catalysts, such as rhodium, ruthenium or platinum, which have also shown promising catalytic performance in the reduction of CO2 to methanol, although their high cost often limits their use to specific applications. The 2021 paper by Tariq Anisa et al. describes Cu / ZnO catalysts combined with ZSM-5 zeolites to which a mixture of CO2 and hydrogen is applied to produce the oxygenates methanol and dimethyl ether. The conversion rate of CO2 to oxygenates is 3% when the catalyst is prepared by the "CVI" (chemical vapor impregnation) method versus 14-20% when prepared by the "OG" (oxalate gel precipitation) method.

[0005] Thus, CO2 capture and conversion are generally two separate steps often carried out by independent industrial infrastructures, which multiplies the number of steps that do not add value to the finished product. The desorption step is an example because it represents a very high energy demand to separate the CO2 from its capture medium, so that it can be purified, compressed, transported, stored and finally recovered by a transformation unit (often distant) into a finished product.

[0006] In order to address the cost and environmental impact issues caused by the separation of CO2 capture and conversion, so-called "dual function materials" have been proposed in the literature because they allow both CO2 capture and then conversion, which allows in particular the use of only one reactor. CO2 capture and conversion processes using a bifunctional material are thus greatly simplified, economically competitive and with reduced environmental impact. Bifunctional materials combining CO2 capture and conversion properties have thus been studied in particular in the context of capture at the plant exit, mainly for methanation reactions (i.e. the reduction of CO2 to methane) but also for the production of synthesis gas using iron-based catalysts. Concerning methanation reactions, bifunctional materials are generally composed of three distinct parts, such as (i) metal oxides or carbonates as adsorbent to capture CO2 at high temperature, (ii) metallic elements (such as nickel, ruthenium or rhodium nanoparticles) to catalyze, in the presence of dihydrogen, the conversion of adsorbed CO2 into valuable products, the combination of (i) and (ii) being generally deposited on (iii) an alumina support. The 2023 paper Loukia-Pantzechroula Merkouri et al. describes bifunctional materials for capturing CO2 at high temperatures (250°C or 500°C) and then reducing them to methane. These materials are composed of nickel and ruthenium (Ni-Ru) nanoparticles, but also potassium (K) as an adsorbent to effectively improve CO2 adsorption, all of which is deposited on a cerium and aluminum (CeO2 / AhO3) support. The process of capturing and reducing the bifunctional material is shown schematically in Figure 6D. PCT / US2015 / 039889 also describes a method for capturing CO2 at high temperature (250°C) and then converting said CO2 into methane using a bifunctional material composed of three distinct parts, namely an adsorbent part (e.g. calcium oxide) for adsorbing CO2, a catalytic part (e.g. ruthenium) for converting CO2 and a support part (e.g. aluminium oxide) on which the adsorbent part and the catalytic part are deposited. The adsorbent and catalytic parts, which are positioned next to each other and are on the surface of the support part, represent respectively 2 to 10% by weight and 1 to 10% by weight of the bifunctional material. The bifunctional materials of the prior art thus generally comprise a support which constitutes the major part by weight of the bifunctional material, which notably limits the quantity of adsorbent present and therefore the capacity to adsorb CO2 effectively. In addition, the materials described as adsorbent in the document PCT / US2015 / 039889 (but also in the document Loukia-Pantzechroula Merkouri et al. of 2023) are only suitable for capture at the factory outlet, which means that they only allow capture of CO2 at high temperature (> 250°C) which is not compatible with capture of CO2 in the air which is at ambient temperature, except by heating the air which causes an additional cost linked to heating and an environmental impact.

[0007] Thus, there is still a need to find bifunctional materials that are particularly suitable for capturing CO2 and then converting it into useful products, particularly methanol. It is particularly useful to find bifunctional materials with an increased capacity to adsorb CO2, whether the capture is carried out at concentrated points (at chimney outlets) or directly in the air, at a temperature ranging from -15 to 45°C. It is also useful to find bifunctional materials with an increased capacity to convert CO2 into useful products such as methanol with a high conversion rate. A "high conversion rate" means a conversion of at least 50% of the CO2 when brought into contact with the bifunctional material.

[0008] The inventors thus had the original idea of ​​preparing bifunctional materials where the support on which the catalyst is deposited also has a CO2 adsorption function. Thus the bifunctional materials of the invention consist of only two parts: a catalytic part and an adsorbent part, the catalytic part being positioned on the absorbent part which also plays the role of support for the catalytic part. In this way the bifunctional materials of the invention have a much greater quantity of adsorbent than the bifunctional materials of the prior art which makes it possible, due to the increased number of adsorption sites within the material, to obtain bifunctional materials with an increased capacity to adsorb CO2. After extensive research, the inventors were able to select compounds capable of acting as both catalyst supports and CO2 adsorbents. Among the selected compounds, the inventors discovered that certain zeolites had particularly interesting CO2 capture properties, which made it possible to use them both as CO2 absorbents and as catalyst supports, thereby obtaining new bifunctional materials. Zeolite-supported catalysts have already been described in the literature for various catalytic reactions including CO2 conversion. However, in these cases, the selected zeolite types only have catalytic properties complementary to the properties of the catalyst deposited on their surface, namely CO2 conversion, but do not allow CO2 capture. Summary

[0009] According to one aspect, the invention relates to a process for capturing and converting carbon dioxide (CO2) into chemical compounds C1 to C3, and preferably methanol, characterized in that it comprises the following steps: - contacting a bifunctional material with a stream comprising carbon dioxide in order to capture the carbon dioxide using said bifunctional material, - contacting the bifunctional material having captured the carbon dioxide with a hydrogen stream in order to convert the carbon dioxide into at least one chemical compound C1 to C3, and preferably methanol, said bifunctional material consisting of a sorbent and a catalyst, said sorbent being capable of capturing the carbon dioxide, by physical adsorption, said catalyst being capable of converting the carbon dioxide into at least one chemical compound C1 to C3, and preferably capable of reducing the carbon dioxide into methanol, said catalyst not comprising a support other than the sorbent, said catalyst being positioned on the surface of said sorbent, said stream comprising the carbon dioxide being an air stream or a chimney outlet stream.

[0010] According to another aspect, the present invention relates to a bifunctional material suitable for use in a CO2 capture and conversion process, said bifunctional material being characterized in that it consists of a sorbent and a catalyst, said sorbent being capable of capturing carbon dioxide, by physical adsorption, said catalyst being capable of converting carbon dioxide into at least one chemical compound C1 to C3, and preferably capable of reducing carbon dioxide into methanol, said catalyst not comprising a support other than the sorbent, said catalyst being positioned on the surface of said sorbent, said sorbent being a zeolite or a metal-organic framework ("MOF"), and is preferably a zeolite, said catalyst consisting of zinc oxide (ZnO) associated with another metal oxide chosen from the group comprising copper oxide (CuO),zirconium dioxide (ZrO2) and cerium dioxide (CeO2) and / or is associated with a metal chosen from the group comprising Au (gold), Pd (palladium) and Pt (platinum).,

[0011] According to yet another aspect, there is provided in the invention a process for preparing the bifunctional material as defined above, characterized in that it comprises the following steps: - a wet impregnation step which consists of mixing the sorbent and the catalyst or a metal precursor of the catalyst in a solvent, for a period ranging from 1 to 48 h, and preferably ranging from 1 to 10 h, in order to ensure the deposition of the catalyst on the surface of the sorbent or to synthesize the catalyst directly on the surface of the sorbent by (co)-reduction / precipitation of the metal precursor; or, - a dry impregnation step which consists of mixing the catalyst in the solvent in order to obtain a catalyst solution having a concentration ranging from 500 to 5000 g of catalyst / L of solvent, and preferably ranging from 1000 to 2500 g / L, then mixing said catalyst solution with the sorbent in powder form, and evaporating the solvent; - filtration of the mixture obtained in one of the two previous stages, - drying the filtered mixture in air, at a temperature ranging from 50 to 150°C, preferably from 90 to 120°C, for a period ranging from 24 to 96 hours, and preferably from 24 to 48 hours, - calcination of the dried mixture at a temperature ranging from 200 to 500°C, preferably from 250 to 350°C, for a period ranging from 2 to 6 hours, and preferably from 2 to 4 hours. Brief description of the drawings

[0012] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analyzing the attached drawing, in which: Fig. 1

[0013] [Fig. 1] is a schematic representation of the bifunctional material of the invention. Detailed description

[0014] The process of capturing and converting carbon dioxide

[0015] Thus, the subject of the present invention is a process for capturing and converting carbon dioxide into chemical compounds C1 to C3, characterized in that it comprises the following steps: - contacting a bifunctional material with a stream comprising carbon dioxide in order to capture the carbon dioxide using said bifunctional material, - contacting the bifunctional material having captured the carbon dioxide with a flow of hydrogen in order to convert the carbon dioxide into at least one chemical compound C1 to C3 chosen from the group comprising methanol, methane, carbon monoxide, formic acid, ethylene, dimethyl ether and propylene, said compound preferably being methanol, said bifunctional material consisting of a sorbent and a catalyst: - said sorbent being capable of capturing carbon dioxide, by physical adsorption, - said catalyst being capable of converting carbon dioxide into at least one chemical compound C1 to C3, and preferably capable of reducing carbon dioxide into methanol, said catalyst not comprising any support other than the sorbent, said catalyst being positioned on the surface of said sorbent, said method being further characterized in that the stream comprising carbon dioxide is an air stream or a stack outlet stream. The direct use of an air flow or a chimney outlet flow is extremely advantageous since it allows one to avoid the prior stage of CO2 capture which aims to isolate said CO2 from other components present in the air or in industrial fumes.

[0016] Advantageously, the bifunctional material of the invention used in the method of the invention consists of only two constituents: a sorbent and a catalyst, which means that the material does not comprise any constituents other than the sorbent and the catalyst. The catalyst does not contain any support other than the sorbent, which means that the sorbent and the catalyst support are a single constituent. The catalyst positioned on the surface of the sorbent means that the catalyst is dispersed over the entire surface of the sorbent and can form several islands that can have different sizes. The catalyst can also be located in the pores of the sorbent. Since the pores of the sorbent are located on the surface of the sorbent, it is considered that the catalyst is positioned on the surface of the sorbent, even if it is located in the pores of the sorbent. In this way, the catalyst and the sorbent are in intimate contact. Figure 1 is a schematic representation of the bifunctional material of the invention. Sorbent within the meaning of the present invention means a material having the property of physical adsorption and which is also suitable as a catalyst support. The sorbent of the invention is thus capable of capturing CO2 but also of supporting a catalyst. Advantageously according to the invention, the sorbent of the invention means both a CO2 adsorbent and a catalyst support. Captured CO2 can be: - CO2 present in the atmosphere at a temperature ranging from -15 to 45°C or, - CO2 present in an industrial process or at the exit of industrial chimneys where the temperature can be high, namely up to 400°C. The catalyst suitable within the scope of the invention is a catalyst capable of converting / transforming the CÛ2 into chemical compounds C1 to C3. Examples of C1 chemical compounds include methanol, methane, carbon monoxide and formic acid, preferably methanol. Examples of C2 chemical compounds include ethylene and dimethyl ether. Examples of C3 chemical compounds include polypropylene. According to an advantageous embodiment of the invention, the catalyst used within the bifunctional material is a catalyst capable of reducing CO2 to methanol. Bringing the flow comprising CO2, namely the air flow or the chimney outlet flow, into contact with the bifunctional material of the invention advantageously makes it possible to firstly capture the CO2 - thanks to the sorbent which will adsorb it - then to convert it in a second stage thanks to the catalyst which will help to transform the adsorbed CO2 when the latter is brought into contact with the hydrogen flow. As stated above, the catalyst is dispersed over the entire surface of the sorbent. The CO2, once adsorbed by the sorbent, is also positioned over the entire surface of the sorbent, meaning that the adsorbed CO2 is also positioned near the catalytic sites, which results in a high conversion of said adsorbed CO2 once the hydrogen stream is brought into contact with the bifunctional material. The combination of the bifunctional material proposed in the invention with the capture and conversion process proposed in the invention leads to several advantages, such as an economically competitive process with reduced environmental impact, but also advantageously makes it possible to obtain a CO2 conversion rate of at least 50%, and preferably at least 55%. Other characteristics defining the bifunctional material used in the capture and conversion process of the invention are described in more detail below.

[0017] According to an advantageous embodiment of the process of the invention, the bifunctional material consists of 60 to 95% by weight of sorbent and 5 to 40% by weight of catalyst, the percentages by weight being expressed relative to the total weight of the bifunctional material. The high proportion of sorbent within the bifunctional material advantageously allows a significant quantity of CO2 to be captured. For example, for two sorbents each having a CO2 adsorption capacity of 5 mmol / g, with 80% sorbent in the bifunctional material it is possible to capture 4 mmol of CO2 per gram of bifunctional material versus only 1 mmol of CCh / g for a bifunctional material which would only comprise 20% sorbent, under conditions of CO2 capture in air and at a temperature ranging from -15 to 45°C.

[0018] According to another advantageous embodiment of the method, the sorbent as defined above is a porous structure having one or all of the following characteristics: - a CO2 adsorption capacity greater than or equal to 0.5 moles of CO2 per kilogram of sorbent (0.5 mol CCh / kg) under the conditions of CO2 capture in air and at a temperature ranging from -15 to 45°C, - CO2 adsorption kinetics greater than or equal to 0.5 moles of CO2 per hour and per kilogram of sorbent (0.5 mol CO2 / h / kg) under conditions of CO2 capture in air and at a temperature ranging from -15 to 45°C, - a specific surface area measured by the BET method from nitrogen adsorption isotherms at a temperature of 77 K, greater than or equal to 500 m 2 / g, and preferably ranging from 500 to 3000 m 2 / g ; - a pore size greater than or equal to 0.33 nm, and preferably ranging from 0.33 to 10 nm; - a uniform distribution of pore sizes; - a density of pores and therefore of CO2 adsorption sites greater than or equal to 0.10 cm 3 per gram of sorbent (0.10 cm 3 / g); - an adsorption selectivity of CO2 compared to other gases greater than or equal to 5, and preferably greater than 10; - thermal stability up to 350°C; - chemical stability with respect to molecules present in the environment; - a release of at least 80% of the CO2 adsorbed and / or converted into at least one chemical compound C1 to C3, preferably at least 90%, and more preferably at least 95%.

[0019] The specific surface area of ​​a material refers to its actual surface area as opposed to its apparent surface area. It represents the total surface area per unit mass and is expressed in m 2 / g. The specific surface area of ​​materials is measured by adsorption of a gas, namely nitrogen, using the BET (Brunauer, Emett and Teller) method. In this case, the specific surface area was calculated with nitrogen as the adsorptive at a temperature of 77 K (the boiling point of liquid nitrogen). A specific surface area of ​​a value greater than or equal to 500 m 2 / g advantageously allows significant interaction between the sorbent and CO2. A pore size greater than or equal to 0.33 nm, and preferably ranging from 0.33 to 10 nm, is a size adapted to the size of the CO2 molecules. A uniform pore size distribution means that at least 60% of the pores are of the same or near-identical size, meaning that the pore size does not vary by more than 0.1 nm. A uniform pore size distribution promotes CO2 capture efficiency. An adsorption selectivity of CO2 over other gases greater than or equal to 5 means that CO2 is adsorbed 5 times more efficiently than another gas potentially present in the medium, such as nitrogen. Thermal stability means that the sorbent does not degrade at temperatures up to 350°C, which is the temperature that can be reached during the CO2 conversion step, and therefore does not suffer any loss of performance. The chemical stability of the sorbent means that the sorbent only reacts with certain molecules under specific conditions of temperature and pressure. For example, the sorbent must be able to capture CO2 from the air but must not react with oxygen present in the air. The release of at least 80% of the CO2 adsorbed and / or converted into at least one chemical compound C1 to C3 is also an important characteristic allowing, at the end of a CO2 capture and conversion cycle, to find a sorbent capable of starting a new capture and conversion cycle, and therefore also to obtain an efficient yield of the capture and conversion process. conversion of the invention. According to a particularly advantageous embodiment of the invention, the sorbent has all of the characteristics mentioned above.

[0020] According to another embodiment of the method of the invention, the sorbent as defined above is a zeolite or a metal-organic framework (“MOF”, English acronym meaning “Metal Organic Framework”), and is preferably a zeolite.

[0021] According to a particular embodiment of the method, the sorbent as defined above is a zeolite having a Si / AI ratio ranging from 1 to 100, and is preferably a zeolite whose IZA (“International Zeolite Classification”) identifiers are chosen from the group comprising FAU, MFI, LTA, MOR, LTL, MER and BEA. "Si" refers to the chemical element silicon and "Al" refers to aluminum. The Si / Al ratio determines the number of acidic, and therefore catalytic, sites in the zeolite. The lower this ratio, the more acidic (and therefore catalytic) sites the zeolite contains. For example, a zeolite particularly suited to the capture and conversion of CO2 into methanol will have, in addition to the aforementioned characteristics, a Si / AI ratio greater than 10. As an example, we can cite a zeolite of type 13X (FAU) or 5A (LTA).

[0022] According to yet another particular embodiment of the method of the invention, the sorbent as defined above is a metallo-organic network "MOF" chosen from the group comprising UiO-Frameworks (UiO-66, UiO-67, UiO-68), M-MOF-74 (M = Mg, Ni, Fe, Co), PCN250 and HKUST-1.

[0023] Still according to an embodiment of the process of the invention, the catalyst as defined above consists of zinc oxide (ZnO) associated with another metal oxide chosen from the group comprising copper oxide (CuO), zirconium dioxide (ZrO2) and cerium dioxide (CeO2) and / or is associated with a metal chosen from the group comprising Cu (copper), Au (gold), Pd (palladium) and Pt (platinum).

[0024] According to an advantageous embodiment of the process of the invention, the catalyst as defined above is chosen from the group comprising the catalyst of formula ZnO-M, ZnO-X, ZnO-MX and ZnO-Xi-X2 with: - M representing a metal chosen from the group comprising Cu, Au, Pd and Pt, - X, X1 and X2 representing, independently of one another, a metal oxide chosen from the group comprising CuO, ZrO2 and CeO2. The dash in the catalyst formula means that the catalyst consists of a mixture of zinc oxide with a metal oxide and / or a metal. According to a particularly advantageous embodiment, the catalyst consists of a mixture of nanoparticles of zinc oxide and copper oxide (ZnO-CuO) or nanoparticles of zinc oxide and zirconium dioxide (ZnO-ZrO2).

[0025] According to an advantageous embodiment of the process of the invention, the catalyst as defined above is in the form of nanoparticles with a size ranging from 5 to 100 nm, and preferably from 10 to 50 nm.

[0026] As an example of a bifunctional material of the invention which is particularly advantageous in the capture and conversion process, mention may be made of a material consisting of the zeolite sorbent of type 13X (FAU) or type 5A (LTA) and the catalyst ZnO-CuO or ZnO-ZrO2. Still as an example, the respective proportions of said zeolite and said catalyst are 90 / 10, 85 / 15 or 80 / 20. The ZnO-CuO or ZnO-ZrO2 catalyst is deposited / dispersed on the surface and in the pores of the zeolite which therefore also plays the role of catalyst support.

[0027] In the first step of the method of the invention, the bifunctional material is for example brought into contact with the flow comprising CO2 until the sorbent has captured sufficient CO2, and preferably until the sorbent is saturated with CO2, saturation meaning that the sorbent has reached its maximum CO2 adsorption capacity. Sufficient CO2 capture means that the sorbent has adsorbed at least 50% of its maximum CO2 adsorption capacity. However, contacting the bifunctional material with the flow comprising CO2 can also be stopped when the flow no longer comprises CO2. Verification of the sufficient amount of CO2 adsorption or of the stream that no longer includes CO2 is carried out by gas chromatography. According to one embodiment of the method of the invention, in the second step the bifunctional material having thus captured the CO2 is brought into contact with a flow of hydrogen so that the catalyst of the bifunctional material allows and accelerates the conversion of the CO2 into chemical compounds C1 to C3, and preferably reduces the CO2 into methanol.

[0028] According to another advantageous embodiment of the capture and conversion process, the bifunctional material is introduced into a single reactor suitable for the capture and conversion of CO2, said material being introduced into the reactor before it comes into contact with the stream comprising the CO2.

[0029] The reactor used in the capture and conversion process of the invention may, for example, be a fixed bed or fluidized bed reactor. A fixed-bed reactor is a type of catalytic reactor in which the catalyst is arranged in the form of granules, beads, or pellets in a fixed bed inside a chamber. Reactants (gases or liquids) pass through the catalyst bed to carry out the chemical reaction. The reactants are introduced at one end of the fixed bed, and the chemical reaction occurs as they pass through the catalyst bed. A fluidized bed reactor is a device in which the catalyst is held in the form of solid particles that are suspended in a continuous flow of gas or liquid. The catalyst particles form a fluid bed that can move freely inside the reactor. In a fluidized bed reactor, the reactants are introduced at the bottom of the reactor, and the reaction gas or liquid is blown through the catalyst particles. The catalyst particles behave like a constantly agitated fluid bed.

[0030] As stated above, the stream comprising CO2 that is contacted with the bifunctional material is an air stream or stack outlet stream. When the CO2 stream is an air stream, the CO2 concentration in the air stream is 300 to 600 ppm. The temperature of such a stream varies from -15 to 45°C, depending on whether it is winter or summer, and depending on the location in the world. For information, the two main components of air are nitrogen (N2) and oxygen (O2). But air is also composed of water vapor and other gases in very small proportions compared to oxygen and nitrogen. These gases are argon (Ar), carbon dioxide (CO2), neon (Ne), methane (CH4), hydrogen (H2), helium (He), krypton (Kr), and xenon (Xe). When the stream containing CO2 is a stack outlet stream, the CO2 concentration in the stream is 1 to 30%. The temperature of such a stream can be up to 400°C. However, it will then be necessary to cool the temperature of said stream before introducing said stream into the reactor to capture the CO2. The flow must be cooled to a temperature less than or equal to 45°C. For information purposes, the composition of some industrial fumes is indicated below. Coal-fired power plants: CO 2 : 12-15%, N 2 : 70-75%, O 2 : 3-5%, Others (NOx, SOx, particles, water vapor). Natural gas power plants: CO 2 : 3-4%, N 2 : 70-75%, O 2 : 10-15%, Others (NOx, water vapor). Cement industry: CO 2 : 15-30%, N 2 : 60-70%, O 2 : 2-5%, Others (NOx, SOx, dust). Steel industry: CO 2: 20-25%, N 2 : 65-70%, O 2 : approximately 5%, Others (NOx, SOx, particles). Refinery and petrochemical industry: CO 2 : 8-15%, N 2 : 70-80%, O 2 : 2-5%, Others (NOx, SOx, hydrocarbons, water vapor).

[0031] According to another advantageous embodiment of the method of the invention, the flow comprising CO2 is introduced into the reactor according to one or all of the following methods: - a GHSV ("Gas Hourly Space Velocity") flow rate ranging from 10 to 500 L / g m at bifunction / h, and preferably from 15 to 100 L / gmat bifunction / h, - a pressure ranging from 1 to 30 bars, - a temperature ranging from -15 to 45°C. GHSV (Gas Hourly Space Velocity) is used to quantify the flow rate of a gas through a chemical reactor, particularly a catalytic reactor. GHSV is more specifically defined as the volume of gas processed per unit volume of catalyst per hour. The higher the GHSV, the faster the reactant gas passes through the catalyst bed. According to the invention the above-mentioned catalyst regarding GHSV represents the bifunctional material and the GHSV is thus expressed in liters of gas per gram of bifunctional material per hour (L / gmat bifunct / h).

[0032] According to another embodiment of the process, after the CO2 capture step and before the conversion step, the reactor may be purged with a flow of inert gas chosen from nitrogen or argon, at a GHSV flow rate ranging from 10 to 500 L / g mat bi-function / h, preferably from 15 to 100 L / gmat bi-function / h and at a pressure ranging from 1 to 200 bars, or by vacuum.

[0033] According to another embodiment of the process of the invention, after the above-mentioned capture and purge steps, the reactor is heated to a temperature ranging from 200 to 350°C, and preferably from 230 to 280°C, in order to carry out the conversion step.

[0034] The heating system used for the reactor can be a conventional heating system. According to an advantageous embodiment of the method of the invention, the reactor is heated by induction. If this option is chosen, the reactor must be provided with a conductive base. Induction heating, in addition to being an electrical heating method, has the advantage of being a fast and precise contactless heating method. It is thus possible to locally reach the desired temperature more quickly than conventional contact heating reactors. It also has no thermal inertia, which allows for a faster temperature drop. Induction heating is therefore perfectly suited to the process of the invention, which requires temperature adjustments at each capture and conversion cycle.

[0035] According to yet another advantageous embodiment of the process of the invention, the hydrogen flow is introduced into the reactor at a temperature ranging from 25 to 100°C, at a GHSV flow rate ranging from 10 to 500 L / g m at bi-function / h, preferably from 15 to 100 L / gmat bi-function / h, and at a pressure ranging from 1 to 200 bars. For example, the hydrogen source could be green, blue, gray or orange hydrogen, and preferably green hydrogen.

[0036] The bifunctional material

[0037] The present invention also relates to a bifunctional material suitable for use in a capture and conversion process as defined above, said bifunctional material being characterized in that it consists of a sorbent and a catalyst, said sorbent being capable of capturing carbon dioxide, by physical adsorption, said catalyst being capable of converting carbon dioxide into at least one chemical compound C1 to C3, and preferably capable of reducing carbon dioxide into methanol, said catalyst not comprising a support other than the sorbent, said catalyst being positioned on the surface of said sorbent, said sorbent being a zeolite or a metal-organic framework ("MOF"), and is preferably a zeolite, said catalyst consisting of zinc oxide (ZnO) associated with another metal oxide chosen from the group comprising copper oxide (CuO),zirconium dioxide (ZrO2) and cerium dioxide (CeO2) and / or is associated with a metal chosen from the group comprising Au (gold), Pd (palladium) and Pt (platinum)., As examples of a bifunctional material which is the subject of the invention, mention may be made of a material consisting of the zeolite sorbent of type 13X (FAU) or type 5A (LTA) and the ZnO-CuO catalyst or ZnO-ZrO2. Still as examples, the respective proportions of said zeolite and said catalyst are 90 / 10, 85 / 15 or 80 / 20.

[0038] The process of preparing the bifunctional material

[0039] The invention also relates to a process for preparing the bifunctional material as defined above, characterized in that it comprises the following steps: - a wet impregnation step which consists of mixing the sorbent and the catalyst or a metal precursor of the catalyst in a solvent, for a period ranging from 1 to 48 h, and preferably ranging from 1 to 10 h, in order to ensure the deposition of the catalyst on the surface of the sorbent or to synthesize the catalyst directly on the surface of the sorbent by (co)-reduction / precipitation of the metal precursor; or, - a dry impregnation step which consists of mixing the catalyst in the solvent in order to obtain a catalyst solution having a concentration ranging from 500 to 5000 g of catalyst / L of solvent, and preferably ranging from 1000 to 2500 g / L, then mixing said catalyst solution with the sorbent in powder form, and evaporating the solvent; - filtration of the mixture obtained in one of the two previous stages, - drying the filtered mixture in air, at a temperature ranging from 50 to 150°C, preferably from 90 to 120°C, for a period ranging from 24 to 96 h, and preferably from 24 to 48 h, - calcination of the dried mixture at a temperature ranging from 200 to 500°C, preferably from 250 to 350°C, for a period ranging from 2 to 6 h, and preferably from 2 to 4 h.

[0040] The first step of the bifunctional material preparation process can therefore be carried out in two different ways, namely by wet impregnation or by dry impregnation. If dry impregnation is chosen, the catalyst solution is preferably added to the sorbent in powder form in three successive additions, each addition being followed by a step of evaporation of the solvent in air, at a temperature of 90 to 120°C, for a period of 20 to 120 min.

[0041] The solvent used in the process for preparing the bifunctional material may be chosen from the group comprising water, aromatic hydrocarbons, alkanes, alcohols, esters, ketones, ethers, glycol ethers, halogenated hydrocarbons and mixtures thereof. Examples of aromatic hydrocarbons include benzene, toluene and / or xylene. Examples of alkanes include hexane and / or heptane. Examples of alcohols include ethanol and / or methanol. Examples of esters include ethyl acetate and / or methyl acetate. Examples of ketones include acetone and / or methyl ethyl ketone. Examples of ethers include dimethyl ether (DME) and / or tetrahydrofuran (THF). Examples of glycol ethers include ethylene glycol and / or propylene glycol. Examples of halogenated hydrocarbons include dichloromethane and / or chlorobenzene.

[0042] At the end of the preparation process, the bifunctional material is obtained in which the catalyst is positioned on the surface of the sorbent.

[0043] As already indicated, the bifunctional material of the invention makes it possible to capture carbon dioxide and then convert it into at least one chemical compound C1 to C3, said material being intended to be used in the process of capturing and converting CO2 as described above. Examples

[0044] Example 1: Preparation of bifunctional materials

[0045] A bifunctional material consisting of 80% by mass of 5A zeolite and 20% by mass of CuO-ZnO catalyst is prepared by wet impregnation according to the following steps: - mixture of 0.8 g of zeolite and 0.2 g of catalyst in 50 mL of deionized water (= solvent), - magnetic stirring of the mixture for 2 hours, - Büchner vacuum filtration of the mixture, - drying in air of the material thus obtained at a temperature of 100°C for 24 hours, - calcination of the dried material at a temperature of 250°C in air, for 3 hours (ramp of 5°C / min).

[0046] A bifunctional material consisting of 90% by mass of 13X zeolite and 10% by mass of CuO-ZnO catalyst is prepared by wet impregnation according to the following steps: - mixture of 1 g of catalyst in 5 mL of deionized water, - incorporation of the catalyst solution obtained in the previous step into 9 g of 13X zeolite in 3 successive additions separated by an evaporation step in air at 100°C for 25 minutes, - once the 3 additions have been made, drying in air of the material thus obtained at a temperature of 100°C for 24 hours, - calcination of the dried material at a temperature of 250°C in air, for 3 hours (ramp of 5°C / min).

[0047] A bifunctional material consisting of 85% by mass of 13X zeolite and 15% by mass of ZnO-ZrO2 catalyst is prepared by wet impregnation according to the following steps: - mixture of 0.85 g of zeolite and 0.15 g of catalyst in 30 mL of ethanol (= solvent), - magnetic stirring of the mixture for 3 hours, - Büchner vacuum filtration of the mixture, - drying in air of the material thus obtained at a temperature of 100°C for 24 hours, - calcination of the dried material at a temperature of 250°C in air, for 3 hours (ramp of 5°C / min).

[0048] Example 2: Preparation of bifunctional materials and their uses for capturing and converting CO2

[0049] Bifunctional material consisting of 15% by mass of CuO-ZnO catalyst (1:1) and 85% by mass of zeolite 13X. The BET surface area of ​​zeolite, measured by the classical N2 adsorption-desorption method, is 600 m 2 / g. Preparation process Step One: Catalyst Synthesis A solution containing 1% vlv of acetic acid in 100 mL of deionized water is prepared. Into this solution are added the metallic precursors of the catalyst, namely 3.749 g of copper nitrate trihydrate (Cu(NO 3 ) 2 -3H 2 O) and 4.616 g of zinc nitrate hexahydrate (Zn(NO 3 ) 2 6H 2 O) in order to obtain a CuO-ZnO ratio of 1:1. The pH of the solution is adjusted to 7 using 1.0 M aqueous ammonium hydroxide (NH4OH) solution. The solution is then brought to 60°C and stirred for 6 hours. Subsequently, the temperature is increased to 80°C to allow the solvent to evaporate. The resulting material is then dried in an oven at 100-120°C for 24 hours. After drying, the material is finally calcined at 450°C for 2 hours, with a temperature ramp of 5°C per minute. The CuO-ZnO catalyst is thus obtained. Second step: preparation of the bifunctional material The CuO-ZnO catalyst obtained in the previous step is then deposited on a 13X zeolite (commercial) by wet impregnation in water. For this, a quantity of 0.15 g of catalyst and 0.85 g of zeolite are mixed in 50 mL of water at room temperature. The solution is left under magnetic stirring for 2 h before being filtered under vacuum (Buchner). The bifunctional material thus obtained is then dried for 24 hours at 100°C in an oven, then calcined at a temperature of 300°C for 2 hours. Use of bifunctional material for CO2 capture and conversion To begin, the reactor is purged to remove any unwanted components. Then, 1 g of the bifunctional material as obtained according to the process described above is introduced into the autoclave-type reactor in the form of a fixed bed. The reactor is then heated to 150°C under an argon flow of 50 mL / min to ensure that all potentially present molecules are desorbed before the first capture step, then cooled to room temperature, still under argon. For successive CO2 capture (by adsorption) and conversion cycles, the following steps are carried out. CO2 capture at 25°C, with dehumidified air from the laboratory, at 250 mL / min, until the material is saturated (120 min). The pressure is maintained at 1 bar. GHSV = 15. 5-minute purge with argon (or N2) at 300 mL / min to remove any residual oxygen or CO2. Pressure is maintained at 1 bar. GHSV = 18. CO2 conversion is initiated by increasing the temperature to 250°C. Simultaneously, pure hydrogen from the electrolyzer is introduced at a flow rate of 250 mL / min until no product or CO2 is detected. The pressure is maintained at 3 bar. GHSV = 15. Finally, a purge is carried out with argon (or N2) at 300 mL / min while cooling down to 250°C. The pressure is maintained at 1 bar. GHSV = 18. The performance of the bifunctional material is reported in Table 1 below.

[0050] [Table 1] These data show optimized conversion rates compared to those of the prior art usually obtained (of the order of 20%) on conventional CO2 to methanol conversion processes. This is certainly due to the fact that CO2, once adsorbed, is found on the entire surface of the sorbent, which means that it is also located close to the catalytic sites and which has the effect of causing a high conversion of the adsorbed CO2 once the hydrogen flow is brought into contact with the bifunctional material. This therefore means optimized mass transport.

[0051] Bifunctional material consisting of 15% by mass of CuO-ZnO catalyst (1:1) and 85% by mass of zeolite 5A. The BET surface area of ​​zeolite is 490 m 2 / g (measured). The catalyst is prepared according to the same protocol as that described just before. To prepare the bifunctional material, the CuO-ZnO catalyst is deposited on the 5A zeolite (commercial) by wet impregnation in water. For this, a quantity of 0.15 g of catalyst and 0.85 g of zeolite are mixed in 40 mL of water at room temperature. The solution is left under magnetic stirring for 1 h before being filtered under vacuum (Buchner). The bifunctional material obtained is then dried for 24 h at 100 ° C in an oven, then is calcined at a temperature of 300 ° C for 2 h. The bifunctional material is then tested under the same conditions as described just before. The performance of the bifunctional material is reported in Table 2 below.

[0052] [Table 2] The same conclusions can be drawn from this as in Table 1.

[0053] This disclosure is not limited to the examples described above, solely as an example, but it encompasses all variants that may be envisaged by those skilled in the art within the framework of the protection sought. List of cited documents Patent documents

[0054] For all useful purposes, the following patent document is cited: - patcitl: PCT / US2015 / 039889 (filing number). Non-patent literature

[0055] For all useful purposes, the following non-patent elements are cited: - nplcit 1: Anisa Tariq et al., Topics in Catalysis (2021) 64: 965-973; nplcit2: Loukia-Pantzechroula Merkouri et al., Nanomaterials 2023, 13, 506. https: / / doi.Org / 10.3390 / nano13030506.

Claims

Claims

1. A process for capturing and converting carbon dioxide into chemical compounds C1 to C3, characterized in that it comprises the following steps: - contacting a bifunctional material with a stream comprising carbon dioxide in order to capture the carbon dioxide using said bifunctional material, - contacting the bifunctional material having captured the carbon dioxide with a hydrogen stream in order to convert the carbon dioxide into at least one chemical compound C1 to C3 selected from the group comprising methanol, methane, carbon monoxide, formic acid, ethylene, dimethyl ether and propylene, said compound preferably being methanol, said bifunctional material consisting of a sorbent and a catalyst, said sorbent being capable of capturing the carbon dioxide, by physical adsorption, said catalyst being capable of converting the carbon dioxide into at least one chemical compound C1 to C3, and preferably capable of reducing the carbon dioxide into methanol, said catalyst not comprising a support other than the sorbent, said catalyst being positioned on the surface of said sorbent, said method being further characterized in that the stream comprising the carbon dioxide is an air stream or a chimney outlet stream.

2. Capture and conversion process according to claim 1, characterized in that the bifunctional material consists of 60 to 95% by weight of sorbent and 5 to 40% by weight of catalyst, the weight percentages being expressed relative to the total weight of the bifunctional material.

3. A capture and conversion method according to claim 1 or 2, characterized in that the sorbent is a porous structure having one or all of the following characteristics: - a CO2 adsorption capacity greater than or equal to 0.5 moles of CO2 per kilogram of sorbent (0.5 mol CCh / kg) under the conditions of CO2 capture in air and at a temperature ranging from -15 to 45°C, - CO2 adsorption kinetics greater than or equal to 0.5 moles of CO2 per hour and per kilogram of sorbent (0.5 mol CO2 / h / kg) under the conditions of CO2 capture in air and at a temperature ranging from -15 to 45°C, - a specific surface area measured by the BET method from nitrogen adsorption isotherms at a temperature of 77 K, greater than or equal to 500 m 2 / g, and preferably ranging from 500 to 3000 m 2 / g ; - a pore size greater than or equal to 0.33 nm, and preferably ranging from 0.33 to 10 nm; - a uniform distribution of pore sizes; - a density of pores and therefore of CO2 adsorption sites greater than or equal to 0.10 cm 3 per gram of sorbent (0.10 cm 3 / g); - an adsorption selectivity of CO2 compared to other gases greater than or equal to 5, and preference greater than 10; - thermal stability ranging from 0 to 350°C; - chemical stability with respect to molecules present in the environment; - a release of at least 80% of the CO2 adsorbed and / or converted into at least one chemical compound C1 to C3, preferably at least 90%, and more preferably at least 95%.

4. A capture and conversion process according to any one of claims 1 to 3, characterized in that the sorbent is a zeolite or a metal-organic framework (“MOF”), and is preferably a zeolite.

5. Capture and conversion process according to any one of claims 1 to 4, characterized in that the sorbent is a zeolite having a Si / AI ratio ranging from 1 to 100, and is preferably a zeolite whose IZA (“International Zeolite Classification”) identifiers are chosen from the group comprising FAU, MFI, LTA, MOR, LTL, MER and BEA.

6. Capture and conversion process according to any one of claims 1 to 5, characterized in that the sorbent is a metal-organic network "MOF" chosen from the group comprising UiO-Frameworks (UiO-66, UiO-67, UiO-68), M-MOF-74 (M = Mg,Ni,Fe,Co), PCN250 and HKUST-1.

7. Capture and conversion process according to any one of claims 1 to 6, characterized in that the catalyst consists of zinc oxide (ZnO) associated with another metal oxide chosen from the group comprising copper oxide (CuO), zirconium dioxide (ZrO2) and cerium dioxide (CeO2) and / or is associated with a metal chosen from the group comprising Cu (copper), Au (gold), Pd (palladium) and Pt (platinum).

8. Capture and conversion process according to any one of claims 1 to 7, characterized in that the catalyst is chosen from the group comprising the catalyst of formula ZnO-M, ZnO-X, ZnO-MX and ZnO-Xi-X2 with: - M representing a metal chosen from the group comprising Cu, Au, Pd and Pt, - X, X1 and X2 representing, independently of one another, a metal oxide chosen from the group comprising CuO, ZrO2 and CeO2.

9. A capture and conversion process according to any one of claims 1 to 8, characterized in that the bifunctional material is introduced into a single reactor adapted to the capture and conversion of carbon dioxide, said material being introduced into the reactor before it is brought into contact with the stream comprising carbon dioxide.

10. Capture and conversion process according to any one of claims 1 to 9, characterized in that the stream comprising carbon dioxide is introduced into the reactor according to one or all of the following methods: - a pressure ranging from 1 to 30 bars, - a GHSV ("Gas Hourly Space Velocity") flow rate ranging from 10 to 500 L / g m at bifunc / h, and preferably from 15 to 100 L / gmat bi-function / h, - a temperature ranging from -15 to 45°C.

11. Capture and conversion process according to any one of claims 1 to 10, characterized in that, after the carbon dioxide capture step and before the conversion step, the reactor is purged with a flow of inert gas chosen from nitrogen or argon, at a GHSV flow rate ranging from 10 to 500 L / gmat bifunc / h, preferably from 15 to 100 L / g ma t bifunction / h and at a pressure ranging from 1 to 200 bars, or by vacuum.

12. A capture and conversion process according to claim 11, characterized in that, after the capture and purge steps, the reactor is heated to a temperature ranging from 200 to 350°C, and preferably from 230 to 280°C, in order to carry out the conversion step.

13. Capture and conversion method according to claim 12, characterized in that the reactor is heated by induction.

14. Capture and conversion process according to any one of claims 1 to 13, characterized in that the hydrogen flow is introduced into the reactor at a temperature ranging from 25 to 100°C, at a GHSV flow rate ranging from 10 to 500 L / g ma t bifunction / h, preferably 15 to 100 L / g m at bifunction / h, and at a pressure ranging from 1 to 200 bars.

15. A bifunctional material suitable for use in a capture and conversion process as defined in any one of claims 1 to 14, said bifunctional material being characterized in that it consists of a sorbent and a catalyst, said sorbent being capable of capturing carbon dioxide, by physical adsorption, said catalyst being capable of converting carbon dioxide into at least one chemical compound C1 to C3, and preferably capable of reducing carbon dioxide into methanol, said catalyst not comprising a support other than the sorbent, said catalyst being positioned on the surface of said sorbent, said sorbent being a zeolite or a metal-organic framework ("MOF"), and is preferably a zeolite, said catalyst consisting of zinc oxide (ZnO) associated with another metal oxide selected from the group comprising copper oxide (CuO),zirconium dioxide (ZrO2) and cerium dioxide (CeO2) and / or is associated with a metal chosen from the group comprising Au (gold), Pd (palladium) and Pt (platinum).,

16. Process for preparing the bifunctional material as defined in claim 15, characterized in that it comprises the following steps: - a wet impregnation step which consists of mixing the sorbent and the catalyst or a metal precursor of the catalyst in a solvent, for a period ranging from 1 to 48 h, and preferably ranging from 1 to 10 h, in order to ensure the deposition of the catalyst on the surface of the sorbent or to synthesize the catalyst directly on the surface of the sorbent by (co)-reduction / precipitation of the metal precursor; or, - a dry impregnation step which consists of mixing the catalyst in the solvent in order to obtain a catalyst solution having a concentration ranging from 500 to 5000 g of catalyst / L of solvent, and preferably ranging from 1000 to 2500 g / L, then mixing said catalyst solution with the sorbent in powder form, and evaporating the solvent; - filtration of the mixture obtained in one of the two previous steps, - drying the filtered mixture in air, at a temperature ranging from 50 to 150°C, preferably from 90 to 120°C, for a period ranging from 24 to 96 h, and preferably from 24 to 48 h, - calcination of the dried mixture at a temperature ranging from 200 to 500°C, preferably from 250 to 350°C, for a period ranging from 2 to 6 h, and preferably from 2 to 4 h.

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