Catalysts containing composite supports and their preparation methods and methods for producing methanol by carbon dioxide hydrogenation

Abstract

This invention relates to the field of catalysts, and discloses a catalyst containing a composite support, its preparation method, and a method for producing methanol by carbon dioxide hydrogenation. The catalyst comprises a composite support and an active metal component supported on the composite support; the composite support comprises a(AO) x )-b(BO y )-c(CO z ( ), wherein A is selected from at least one of Zn, In, Cr, Cu, Fe and Mo; B is selected from at least one of Ce, Zr, Al, La and Si; and C is selected from at least one of Zn, Cr, Cd, Zr, Ca and Mg; a = 0.1–0.7, b = 0.01–0.5, c = 0.01–0.4, x = 1–3, y = 1–3, z = 1–3; the specific surface area of ​​the catalyst is not less than 40 m². 2 / g. This catalyst has a high specific surface area and exhibits high catalytic activity and methanol selectivity in the hydrogenation of carbon dioxide.

Description

Technical Field

[0001] This invention relates to the field of catalysts, specifically to a catalyst containing a composite support, a method for preparing the same, and a method for preparing methanol by hydrogenation of carbon dioxide. Background Technology

[0002] Climate change has a significant impact on socio-economic development and human progress. In recent years, "carbon neutrality and carbon peaking" have attracted widespread attention in the technological field. The consumption of fossil fuels has led to a sharp increase in CO2 concentration, which in turn has triggered numerous environmental problems. The hydrogenation and utilization of carbon dioxide is a hot research topic in carbon-based energy recycling. It can alleviate the environmental pressure caused by CO2, address the energy shortage problem after the oil and gas era, turn waste into treasure, and bring considerable economic benefits.

[0003] Methanol is a widely used bulk chemical. It can be used directly as fuel or as an intermediate product to convert into aromatics, olefins, and other chemicals. The development of MTO, MTG, and MTP processes is also maturing. Methanol consumption is projected to reach 77.9 million tons in 2020. Currently, methanol production mainly relies on syngas from non-renewable resources, converting CO2 into methanol.

[0004] Currently, thermodynamic equilibrium shows that the yield of methanol from CO2 decreases with increasing reaction temperature and increases with increasing reaction pressure. Therefore, developing low-temperature methanol production catalysts can save industrial heating costs and improve methanol yield. Most industrial CO2-to-methanol catalysts are currently modified from copper-zinc-aluminum oxide catalysts used in syngas-to-methanol production. Mature syngas-to-methanol catalysts can achieve a methanol selectivity of up to 99% at 250-300℃ and 5-10 MPa, but the selectivity for CO2-to-methanol production is only 60%. For example, CN101983765A, CN102000578A, CN102302934A, and CN101513615A disclose methods to modulate the dispersibility of copper and improve the interaction between Cu and the support by introducing different promoters (SiO2, TiO2, MgO, CeO2, Ag2O, Fe2O3, La2O3, etc.) into Cu / ZnO catalysts. However, the preparation processes of these catalysts are complex, and the methanol selectivity is low. Meanwhile, the poor hydrothermal stability of copper-based catalysts and the problem of long-term deactivation have not been well resolved.

[0005] To improve the methanol selectivity in the CO2-to-methanol reaction, numerous attempts have been made in existing technologies. Professor Wu Xinping's research group at East China University of Science and Technology has effectively improved methanol selectivity under low pressures of less than or equal to 2 MPa using a zinc-rich Pd@Zn core-shell bimetallic catalyst prepared by CdSe (Liao et al., Green Chem. 19, 270–280 (2017)). Professor Liu Changjun's research group at Tianjin University first mixed In2O3 powder with a Pd / peptide complex, then heat-treated it to remove the peptides, preparing a Pd / In2O3 catalyst. The resulting Pd / In2O3 catalyst consists of highly dispersed Pd nanoparticles supported by In2O3, mainly exposed on the (111) surface with a particle size of 3.6 nm, thus helping to improve the catalytic performance of the Pd / In2O3 catalyst in CO2 hydrogenation to methanol, with CO2 conversion >20% and methanol selectivity >70% (Rui et al., Applied Catalysis). B:Environmental.218,488-497(2017)), but in the above literature, the crystal form of the support is an important factor affecting the selectivity and stability of the reaction, and it is difficult to control. CN110479235A discloses an indium oxide catalyst for the production of methanol from CO2, which achieves high methanol selectivity, but the catalyst preparation process is relatively complicated, costly and time-consuming.

[0006] Therefore, the challenge and direction for achieving the industrial production of methanol from CO2 is to develop catalysts with high and low temperature activity, high methanol selectivity, simple preparation process, and low energy consumption while ensuring hydrothermal stability. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of high catalyst preparation cost, small specific surface area, low methanol selectivity, and low space-time yield in the prior art. It provides a catalyst containing a composite support, its preparation method, and a method for preparing methanol by carbon dioxide hydrogenation. This catalyst has a high specific surface area, high catalytic activity in the reaction of preparing methanol by carbon dioxide hydrogenation, and high methanol selectivity.

[0008] To achieve the above objectives, the first aspect of the present invention provides a catalyst containing a composite support, the catalyst comprising a composite support and an active metal component supported on the composite support;

[0009] The composite carrier comprises a(AO) x )-b(BO y )-c(CO z), wherein A is selected from at least one of Zn, In, Cr, Cu, Fe and Mo, B is selected from at least one of Ce, Zr, Al, La and Si, and C is selected from at least one of Zn, Cr, Cd, Zr and Mg; wherein a = 0.1-0.7, b = 0.01-0.5, c = 0.01-0.4, x = 1-3, y = 1-3, z = 1-3;

[0010] The specific surface area of ​​the catalyst is not less than 40 m². 2 / g.

[0011] A second aspect of the present invention provides a method for preparing a catalyst containing a composite support, comprising the following steps:

[0012] (1) Provide a mixed solution containing salt A, salt B, salt C and auxiliaries;

[0013] Wherein, A is selected from at least one of Zn, In, Cr, Cu, Fe and Mo, B is selected from at least one of Ce, Zr, Al, La and Si, and C is selected from at least one of Zn, Cr, Cd, Zr, Ca and Mg; the auxiliary agent is a precipitant and / or a template agent;

[0014] (2) The mixed solution is reacted under microwave reaction conditions;

[0015] The microwave reaction conditions include: microwave output power of 500-2000W, reaction temperature of 60-200℃, and reaction time of 0.5-24h.

[0016] (3) The product obtained in step (2) is subjected to solid-liquid separation, washing, drying and calcination to obtain a composite carrier;

[0017] (4) Introduce active metal components onto the composite support to obtain a catalyst containing the composite support.

[0018] The third aspect of the present invention provides a catalyst containing a composite support prepared by the preparation method of the second aspect.

[0019] A fourth aspect of the present invention provides a method for preparing methanol by hydrogenation of carbon dioxide, the method comprising: contacting carbon dioxide and hydrogen in the presence of a catalyst under conditions for preparing methanol by hydrogenation of carbon dioxide; wherein the catalyst is the catalyst containing a composite support as described in the first and third aspects.

[0020] The beneficial effects obtained by the present invention through the above technical solution are as follows:

[0021] (1) The catalyst containing the composite support provided by the present invention has a high specific surface area, appropriate interaction between the active metal component and the support, good crystallinity, and can effectively suppress the reverse water-gas shift reaction.

[0022] (2) The preparation method of the catalyst containing the composite support provided by the present invention is simple to operate. It utilizes the response of the auxiliary agent to microwave to promote the rapid hydrolysis of metal complexes / coordination compounds, which is conducive to the formation of composite supports with large specific surface area and many oxygen vacancies. At the same time, compared with traditional hydrothermal, microwave-assisted synthesis has the advantages of high efficiency and energy saving.

[0023] (3) The method for preparing methanol by carbon dioxide hydrogenation provided by the present invention can achieve a high conversion rate and good reaction stability at a lower temperature and pressure by using the catalyst containing the composite support provided by the present invention. The CO2 conversion rate can reach 12% and the methanol selectivity can reach 92%. Detailed Implementation

[0024] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] The first aspect of the present invention provides a catalyst containing a composite support, the catalyst comprising a composite support and an active metal component supported on the composite support;

[0026] The composite carrier comprises a(AO) x )-b(BO y )-c(CO z ), wherein A is selected from at least one of Zn, In, Cr, Cu, Fe and Mo, B is selected from at least one of Ce, Zr, Al, La and Si, and C is selected from at least one of Zn, Cr, Cd, Zr, Ca and Mg; wherein a = 0.1-0.7, b = 0.01-0.5, c = 0.01-0.4, x = 1-3, y = 1-3, z = 1-3;

[0027] The specific surface area of ​​the catalyst is not less than 40 m². 2 / g.

[0028] In this invention, the composite carrier comprises a(AO) x )-b(BO y )-c(CO z ), where a, b, and c represent the components AO in the composite carrier. x BO y CO z The molar ratio, where x, y, and z represent AO respectively. x BOy CO z The atomic ratio of O to A, B, and C in the composite support. The components in the composite support are uniformly distributed and composited at the molecular scale. Under the above composition of the composite support, it helps to improve the structural stability and hydrophobicity of the composite support. The catalyst containing the composite support has a high specific surface area, appropriate interaction between the active metal component and the support, good crystallinity, and can effectively suppress the reverse water-gas shift reaction. It exhibits high catalytic activity and high methanol selectivity in the carbon dioxide hydrogenation to methanol reaction.

[0029] According to the present invention, A, B, and C in the composite carrier may be the same or different, and each may be independently selected from the aforementioned element types. Preferably, A, B, and C are different element types; more preferably, A is selected from at least one of In, Cu, and Mo, B is selected from at least one of Zr, Ce, La, and Al, and C is selected from at least one of Zn, Ca, and Mg; under the above preferred conditions, CO2 adsorption is facilitated.

[0030] According to a preferred embodiment of the present invention, a = 0.3-0.6, b = 0.01-0.4, c = 0.01-0.3; controlling the composition of the composite carrier within the above range is beneficial for regulating the appropriate interaction strength with CO2.

[0031] In this invention, the selection range of the active metal component is relatively wide. Preferably, the active metal component is a Group VIII and / or Group IB metal, more preferably at least one of Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, Ag, and Au, more preferably at least one of Pd, Pt, Cu, and Au, and most preferably Pd and / or Pt. Using the above-mentioned preferred embodiments helps to improve methanol selectivity.

[0032] According to the present invention, the composite support can be prepared using conventional methods in the art, as long as the above-mentioned structural composition and physical property requirements can be obtained. Preferably, the composite support is obtained by microwave-assisted hydrothermal synthesis. Microwave radiation is electromagnetic radiation with a frequency range of 0.3-300 GHz and a corresponding wavelength of 1 cm-1 m. Currently, commercially available microwave reactors used in conventional chemical synthesis operate at a frequency of 2.45 GHz (corresponding to a wavelength of 12.25 cm).

[0033] In this invention, the specific surface area is tested using a low-temperature N2 isothermal adsorption-desorption method followed by conventional BET calculations to analyze the catalyst's specific surface area. Before analysis, the sample is dried at 120°C for 2 hours, and then subjected to vacuum treatment at 300°C. The adsorption medium is high-purity nitrogen. Adsorption / desorption experiments are conducted under liquid nitrogen cooling conditions (-196°C).

[0034] According to a preferred embodiment of the present invention, the catalyst has a specific surface area of ​​not less than 50 m². 2 / g, preferably 50-100m 2 / g; Under the above preferred conditions, the catalytic activity can be further improved and the feed conversion rate can be increased.

[0035] According to a preferred embodiment of the present invention, the content of the composite support is 50-99.9 wt% based on the total weight of the catalyst, and the content of the active metal component is 0.1-50 wt% based on the oxide content; preferably, the content of the composite support is 60-99.8 wt% based on the total weight of the catalyst, and the content of the active metal component is 0.2-40 wt% based on the oxide content.

[0036] According to the present invention, those skilled in the art will understand that the content of the active metal component can be adaptively adjusted for different types of active metal components. For example, when the active metal component is a noble metal, preferably, based on the total weight of the catalyst, the content of the composite support is 90-99.8 wt%, more preferably 95-99.8 wt%; and based on oxides, the content of the active metal component is 0.2-10 wt%, more preferably 0.2-5 wt%. When the active metal component is a non-noble metal, preferably, based on the total weight of the catalyst, the content of the composite support is 50-90 wt%, more preferably 60-80 wt%; and based on oxides, the content of the active metal component is 10-50 wt%, more preferably 20-40 wt%.

[0037] In this invention, the content of each of the above components was tested using ICP-AES.

[0038] A second aspect of the present invention provides a method for preparing a catalyst containing a composite support, comprising the following steps:

[0039] (1) Provide a mixed solution containing salt A, salt B, salt C and auxiliaries;

[0040] Wherein, A is selected from at least one of Zn, In, Cr, Cu, Fe and Mo, B is selected from at least one of Ce, Zr, Al, La and Si, and C is selected from at least one of Zn, Cr, Cd, Zr, Ca and Mg; the auxiliary agent is a precipitant and / or a template agent;

[0041] (2) The mixed solution is reacted under microwave reaction conditions;

[0042] The microwave reaction conditions include: microwave output power of 500-2000W, reaction temperature of 60-200℃, and reaction time of 0.5-24h.

[0043] (3) The product obtained in step (2) is subjected to solid-liquid separation, washing, drying and calcination to obtain a composite carrier;

[0044] (4) Introduce active metal components onto the composite support to obtain a catalyst containing the composite support.

[0045] According to the present invention, the response of the additive to microwaves is used to assist in the hydrothermal synthesis of the composite carrier. The local hot spots of microwaves promote the rapid hydrolysis of the formed metal complexes / coordination compounds. The homogeneity is ensured by mixing at the molecular scale in the solution. After drying and calcination, it is beneficial to form a composite oxide with a large specific surface area and many oxygen vacancies.

[0046] According to a preferred embodiment of the present invention, in the mixed solution, the total concentration of salts A, B, and C, based on the molar amounts of elements A, B, and C, is 0.1-4 mol / L, preferably 0.2-2 mol / L. Under these preferred conditions, it is beneficial to improve the uniformity of hydrothermal precipitation.

[0047] According to a preferred embodiment of the present invention, in the mixed solution, the molar ratio of salt A: salt B: salt C, based on the molar amounts of elements A, B, and C, is (0.1-0.7):(0.01-0.5):(0.01-0.4), preferably (0.3-0.6):(0.01-0.4):(0.01-0.3).

[0048] According to a preferred embodiment of the present invention, A, B, and C may be the same or different, and each may be independently selected from the aforementioned element types. Preferably, A, B, and C are different element types, wherein A is selected from at least one of In, Cu, and Mo, B is selected from at least one of Zr, Ce, La, and Al, and C is selected from at least one of Zn, Ca, and Mg.

[0049] According to a preferred embodiment of the present invention, the selection range for the specific types of salt A, salt B, and salt C is relatively wide, and is preferably a soluble salt of A, B, and C; more preferably, salt A, salt B, and salt C are each independently selected from at least one of nitrates, acetates, sulfates, and halides of A, B, and C.

[0050] According to a preferred embodiment of the present invention, the mixed solution further contains a solvent, which can be a conventionally chosen solvent in the art, as long as it can achieve uniform mixing of the components in the mixed solution; the solvent is preferably water and / or ethanol, and more preferably water and ethanol. When water and ethanol are used as solvents, the volume ratio of water to ethanol in the solvent is 0.1-10:1.

[0051] According to the present invention, the auxiliary agent may be selected from precipitants and / or template agents conventionally chosen in the art. Preferably, the auxiliary agent is a precipitant and / or template agent with polar substance properties, which is beneficial to enhance the response to microwaves, increase the local hot spots of microwaves, and thus promote the rapid hydrolysis of metal complexes / complexes. Preferably, the auxiliary agent is a mixture of precipitants and template agents with polar substance properties.

[0052] According to a preferred embodiment of the present invention, the precipitant is selected from at least one of ammonia, ammonium carbonate, urea, citric acid, oxalic acid, ethylenediaminetetraacetic acid, and sodium hydroxide, preferably at least one of urea, citric acid, ammonium carbonate, and oxalic acid.

[0053] According to a preferred embodiment of the present invention, the amount of the precipitant is calculated based on the theoretical stoichiometric ratio of the number of metal atoms of A, B, and C during precipitation or coordination. Preferably, the molar amount of the precipitant is 1-3 times the theoretical stoichiometric ratio of the number of metal atoms of A, B, and C during precipitation or coordination, and more preferably 1-2 times.

[0054] According to a preferred embodiment of the present invention, the template agent is selected from at least one of the following: ethylene oxide-polyoxypropylene-polyoxyethylene amphiphilic block copolymer (F127, preferably with a number average molecular weight of 1000-10000), ethylene oxide-polyoxypropylene-polyoxyethylene triblock copolymer (P123, preferably with a number average molecular weight of 500-10000), ethylene oxide-polyoxypropylene segmented polyether (F108, preferably with a number average molecular weight of 1000-10000), polyethylene glycol (PEG, preferably with a number average molecular weight of 200-5000), and polyoxyethylene ether (preferably with a number average molecular weight of 2000-10000); preferably ethylene oxide-polyoxypropylene-polyoxyethylene triblock copolymer and / or polyethylene glycol.

[0055] According to a preferred embodiment of the present invention, the ratio of the amount of the template agent to the total mass of salt A, salt B, and salt C is 0.01-10:1, preferably 0.05-2:1.

[0056] By using the above-mentioned preferred amounts of precipitant and template agent, the response of the additives to microwaves can be further optimized, which is beneficial to hydrothermal molding.

[0057] In this invention, there are no special limitations on the mixing method and the order of addition of the mixed solution. Salt A, salt B, salt C, and the additive can be dissolved separately in a solvent before mixing, or salt A, salt B, and salt C can be dissolved together in a solvent before introducing the additive, as long as the concentration of each component in the mixed solution meets the requirements. Preferably, the mixed solution is provided by: dissolving salt A, salt B, and salt C in a solvent to obtain a first solution, dissolving the additive in a solvent to obtain a second solution, and then adding the second solution to the first solution to obtain the mixed solution.

[0058] According to a preferred embodiment of the present invention, in step (2), the microwave reaction conditions include: microwave output power of 500-1500W, reaction temperature of 120-200℃, and reaction time of 1-8h.

[0059] According to a preferred embodiment of the present invention, the method further includes, after the microwave reaction in step (2) is completed, natural cooling aging is performed; more preferably, the aging time is 1-3 hours. The above preferred embodiment is beneficial for crystallization aging.

[0060] According to the present invention, there are no special requirements for the reaction apparatus in step (2), and a conventional microwave synthesizer can be used for the reaction, wherein the microwave frequency is preferably 2.45 GHz.

[0061] According to the present invention, the washing, drying and calcination in step (3) can be carried out using conventional methods and apparatus in the art, and will not be described in detail here. Preferably, the washing process includes: washing and filtering with deionized water multiple times until the filtrate is neutral.

[0062] According to a preferred embodiment of the present invention, in step (3), the drying conditions include drying at 60-130°C for 1-4 hours.

[0063] According to a preferred embodiment of the present invention, in step (3), the calcination conditions include calcination at 200-600°C for 1-6 hours, and more preferably, the calcination conditions include calcination at 250-400°C for 2-4 hours.

[0064] In this invention, step (4) can employ any conventional method in the art to introduce the active metal component into the composite support. Preferably, the process of introducing the active metal component in step (4) includes: impregnating the composite support in a salt solution of the active metal, followed by drying and calcination to obtain a catalyst containing the composite support. The impregnation method can be selected from equal-volume impregnation or excess impregnation. Preferably, the volume ratio of the amount of the active metal salt solution to the water absorption of the composite support is 1-1.5:1. Using the above preferred embodiments facilitates the uniform dispersion of the active component and maximizes the adsorption capacity.

[0065] According to a preferred embodiment of the present invention, the drying conditions include: drying at 30-60°C for 0.5-3 hours under vacuum conditions; preferably, the vacuum degree is 50-500 kPa.

[0066] According to a preferred embodiment of the present invention, the calcination conditions include: calcination at 200-600°C for 1-6 hours, preferably calcination at 250-400°C for 2-4 hours.

[0067] In this invention, the selection range of the active metal component is relatively wide. Preferably, the active metal component is a metal of Group VIII and / or Group IB, more preferably at least one of Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, Ag and Au, more preferably at least one of Pd, Pt, Cu and Au, and most preferably Pd and / or Pt.

[0068] According to a preferred embodiment of the present invention, the salt of the active metal is selected from organic salts and / or inorganic salts of the active metal; preferably, the inorganic salt of the active metal is selected from at least one of nitrates, nitrates, acetates, sulfates and halides of the active metal.

[0069] According to a preferred embodiment of the present invention, the concentration of the salt solution of the active metal is 0.1-3 mol / L, preferably 0.1-2 mol / L, based on the molar amount of the active metal.

[0070] According to a preferred embodiment of the present invention, the amount of composite support and active metal salt solution used is such that, based on the total weight of the catalyst, the content of the composite support is 50-99.9 wt%, and the content of the active metal component, calculated as oxide, is 0.1-50 wt%, preferably 0.2-40 wt%, and more preferably 0.2-20 wt%.

[0071] According to the present invention, those skilled in the art will understand that the content of the active metal component can be adaptively adjusted for different types of active metal components. For example, when the active metal component is a noble metal, preferably, based on the total weight of the catalyst, the content of the composite support is 90-99.8 wt%, more preferably 95-99.8 wt%; and based on oxides, the content of the active metal component is 0.2-10 wt%, more preferably 0.2-5 wt%. When the active metal component is a non-noble metal, preferably, based on the total weight of the catalyst, the content of the composite support is 50-90 wt%, more preferably 60-80 wt%; and based on oxides, the content of the active metal component is 10-50 wt%, more preferably 20-40 wt%.

[0072] A third aspect of this invention provides a catalyst containing a composite support prepared by the above-described method. The composite support is synthesized using microwave-assisted hydrothermal synthesis. The catalyst exhibits a high specific surface area, excellent catalytic performance, high reactivity, and high CO2 conversion and methanol selectivity.

[0073] A fourth aspect of the present invention provides a method for preparing methanol by hydrogenation of carbon dioxide, the method comprising: contacting carbon dioxide and hydrogen in the presence of a catalyst under conditions for preparing methanol by hydrogenation of carbon dioxide; wherein the catalyst comprises the catalyst containing a composite support as described in the first and third aspects.

[0074] In this invention, the particle size of the catalyst containing the composite support has a wide selection range and can be adjusted according to actual reaction and production needs. Preferably, the catalyst containing the composite support is obtained by tableting, crushing, and sieving, and the particle size of the catalyst is 40-60 mesh.

[0075] According to a preferred embodiment of the present invention, the conditions for the reaction of hydrogenating carbon dioxide to prepare methanol include: a reaction pressure of 1-8 MPa, a reaction temperature of 200-400°C, and a volume hourly space velocity of 2000-30000 h⁻¹. -1 The H2 / CO2 molar ratio is 1-8, preferably, the reaction pressure is 1-6 MPa, the reaction temperature is 250-350℃, and the volume hourly space velocity is 3000-20000 h⁻¹. -1 The H2 / CO2 molar ratio is 2-6. Adopting the above-described preferred embodiment is beneficial for improving CO2 conversion rate and methanol selectivity.

[0076] According to a preferred embodiment of the present invention, the catalyst is further subjected to a pre-reduction treatment before use; preferably, the pre-reduction treatment conditions include: reduction at 200-600°C for 1-12 hours under an H2 and / or CO atmosphere, a pre-reduction pressure of 0.1-1 MPa, and a volume hourly space velocity of 500-100000 h⁻¹.-1 Further preferably, the pre-reduction treatment conditions include: reduction at 250-450℃ for 2-6 hours, pre-reduction pressure of 0.1-0.5 MPa, and volumetric hourly space velocity of 1000-40000 h⁻¹. -1 .

[0077] The present invention will be described in detail below through embodiments.

[0078] In the following examples, all raw materials used were commercially available.

[0079] Example 1

[0080] 15.02 g of indium nitrate tetrahydrate, 11.55 g of zirconium nitrate pentahydrate, and 4.00 g of zinc nitrate hexahydrate were dissolved in 100 mL of ethanol and 50 mL of deionized water to obtain the first solution. 32.00 g of urea and 30 g of PEG (Mn = 2000) were dissolved in 80 mL of ethanol and 50 mL of deionized water to obtain the second solution. The second solution was poured into the first solution and stirred at room temperature for 1 hour. After mixing evenly, the mixture was transferred to a hydrothermal reactor and placed in a microwave synthesizer. The temperature was raised to 150°C under microwave output power of 1500W and frequency of 2.45GHz. After holding at this temperature for 4 hours, microwave heating was stopped, and the mixture was allowed to cool naturally for 2 hours. The mixture was then washed three times with deionized water, filtered three times, dried at 60°C for 2 hours, and calcined at 350°C for 3 hours to obtain the composite support. 0.23g of palladium nitrate dihydrate was dissolved in 5mL of water to prepare a solution, which was then poured into a flask containing 6g of the composite support. The resulting solid was dried by rotary evaporation at 120°C under a vacuum of 100kPa for 2 hours, and then calcined at 300°C for 2 hours to obtain catalyst S1 containing the composite support. The physicochemical properties of the catalyst are shown in Table 1.

[0081] The catalyst powder was pressed into tablets at 15 MPa, crushed, and screened to a mesh size of 40-60 for reaction evaluation.

[0082] 0.2g of the selected catalyst was weighed and loaded into a reaction tube with an inner diameter of 8mm. It was reduced at 300℃ for 2h under normal pressure and in pure H2. The volume hourly space velocity of H2 was 15000h. -1 ;

[0083] Then, methanol is prepared by carbon dioxide hydrogenation under the following conditions: 5 MPa, 280 °C, and 10,000 h⁻¹. -1 With n(H2) / n(CO2) = 4, the liquid phase product was collected in an ice-water bath, and the product composition was analyzed by gas chromatography. The catalyst evaluation results are shown in Table 2.

[0084] Example 2

[0085] The method described in Example 1 was followed, except that 32.00 g of urea was replaced with 48 g of ammonium carbonate. Catalyst S2 containing a composite support was obtained, and its physicochemical properties are shown in Table 1. The catalyst evaluation results are shown in Table 2.

[0086] Example 3

[0087] The method described in Example 1 was followed, except that 32.00 g of urea was replaced with 30 g of citric acid. Catalyst S3 containing a composite support was obtained, and its physicochemical properties are shown in Table 1. The catalyst evaluation results are shown in Table 2.

[0088] Example 4

[0089] Following the method in Example 1, except that 32.00 g of urea and 30 g of PEG (Mn = 2000) were replaced with 30 g of oxalic acid. Catalyst S4 containing a composite support was obtained, and its physicochemical properties are shown in Table 1. Catalyst evaluation results are shown in Table 2.

[0090] Example 5

[0091] Following the method in Example 1, except that 32.00 g of urea and 30 g of PEG (Mn = 2000) were replaced with 10 g of NaOH. Catalyst S5 containing a composite support was obtained, and its physicochemical properties are shown in Table 1. The catalyst evaluation results are shown in Table 2.

[0092] Example 6

[0093] 20.00 g of indium nitrate tetrahydrate, 13.42 g of aluminum nitrate nonahydrate, and 5.32 g of zinc nitrate hexahydrate were dissolved in 120 mL of ethanol and 60 mL of deionized water to obtain the first solution. 32.00 g of urea and 3.00 g of P123 (Mn = 8400) were dissolved in 80 mL of ethanol and 50 mL of deionized water to obtain the second solution. The second solution was poured into the first solution, stirred at room temperature for 1 hour, and after thorough mixing, transferred to a hydrothermal reactor and placed in a microwave synthesizer. The mixture was heated to 150 °C at a microwave output power of 1500 W and a frequency of 2.45 GHz, held at this temperature for 4 hours, then microwave heating was stopped. The mixture was allowed to cool naturally for 2 hours, washed three times with deionized water, filtered three times, dried at 60 °C for 2 hours, and calcined at 350 °C for 3 hours to obtain the composite carrier.

[0094] Weigh 0.39 g of palladium nitrate dihydrate and dissolve it in 12 mL of water to prepare a solution. Pour the solution into a flask containing 13.5 g of composite support. Dry the obtained solid by rotary evaporation at 120 °C under a vacuum of 100 kPa for 2 h, and then calcine it at 300 °C for 2 h to obtain catalyst S6 containing composite support. The physicochemical properties of the catalyst are shown in Table 1.

[0095] The catalyst powder was pressed into tablets at 15 MPa, crushed, and screened to a mesh size of 40-60 for reaction evaluation.

[0096] 0.2g of the selected catalyst was weighed and loaded into a reaction tube with an inner diameter of 8mm. It was reduced at 300℃ for 2h under normal pressure and in pure H2. The volume hourly space velocity of H2 was 15000h. -1 ;

[0097] Then, methanol is prepared by carbon dioxide hydrogenation under the following conditions: 3 MPa, 280 °C, 10000 h. -1 With n(H2) / n(CO2) = 5, the liquid phase product was collected in an ice-water bath, and the product composition was analyzed by gas chromatography. The catalyst evaluation results are shown in Table 2.

[0098] Example 7

[0099] The method was followed as in Example 1, except that the microwave output power was 1000W, the reaction temperature was 120℃, and the reaction was carried out at this temperature for 12 hours. Catalyst S7 containing the composite support was obtained, and its physicochemical properties are shown in Table 1. The catalyst evaluation results are shown in Table 2.

[0100] Example 8

[0101] The method described in Example 1 was followed, except that 0.23 g of palladium nitrate dihydrate was replaced with 0.52 g of chloroplatinic acid hexahydrate. Catalyst S8 containing a composite support was obtained, and its physicochemical properties are shown in Table 1. The catalyst evaluation results are shown in Table 2.

[0102] Example 9

[0103] Solution A was prepared by dissolving 20.00 g indium nitrate tetrahydrate, 12.00 g cerium nitrate hexahydrate, and 10.00 g magnesium nitrate hexahydrate in 150 mL of ethanol and 70 mL of deionized water. Solution B was prepared by dissolving 40.00 g urea and 25.00 g PEG (Mn = 2000) in 100 mL of ethanol and 70 mL of deionized water. Solution B was poured into solution A and stirred at room temperature for 1 hour. After mixing evenly, the mixture was transferred to a hydrothermal reactor and placed in a microwave synthesizer. The temperature was raised to 200°C under microwave output power of 1500W and frequency of 2.45GHz. After holding at this temperature for 4 hours, microwave heating was stopped, and the mixture was allowed to cool naturally for 2 hours. The mixture was then washed three times with deionized water, filtered three times, dried at 60°C for 2 hours, and calcined at 350°C for 3 hours to obtain the composite support. 0.23g of palladium nitrate dihydrate was dissolved in 5mL of water to obtain solution C, which was poured into a flask containing 6g of the composite support. The resulting solid was dried by rotary evaporation at 120°C under a vacuum of 100kPa for 2 hours, and then calcined at 300°C for 2 hours to obtain catalyst S9 containing the composite support. The physicochemical properties of the catalyst are shown in Table 1.

[0104] The catalyst powder was pressed into tablets at 15 MPa, crushed, and screened to a mesh size of 40-60 for reaction evaluation.

[0105] 0.2g of the selected catalyst was weighed and loaded into a reaction tube with an inner diameter of 8mm. It was reduced at 300℃ for 2h under normal pressure and in pure H2. The volume hourly space velocity of H2 was 15000h. -1 ;

[0106] Then, methanol is prepared by carbon dioxide hydrogenation under the following conditions: 3 MPa, 280 °C, 10000 h. -1 With n(H2) / n(CO2) = 5, the liquid phase product was collected in an ice-water bath, and the product composition was analyzed by gas chromatography. The catalyst evaluation results are shown in Table 2.

[0107] Comparative Example 1

[0108] 15.02 g of indium nitrate tetrahydrate, 11.55 g of zirconium nitrate pentahydrate, and 4 g of zinc nitrate hexahydrate were dissolved in 50 mL of ethanol and 30 mL of deionized water to obtain the first solution. 32 g of urea was dissolved in 80 mL of ethanol and 50 mL of deionized water to obtain the second solution. The second solution was poured into the first solution, stirred at room temperature for 4 hours, and after thorough mixing, transferred to a hydrothermal reactor. The mixture was heated to 120 °C in a drying oven and held at that temperature for 20 hours. After natural cooling and stirring for 2 hours, the mixture was naturally filtered, washed three times with deionized water, filtered three times under vacuum, dried at 60 °C for 2 hours, and calcined at 350 °C for 3 hours to obtain the oxide support. 0.23 g of palladium nitrate dihydrate was weighed, dissolved in water, impregnated with an equal volume, and dried. The resulting sample was dried at 120 °C for 2 hours and then calcined at 300 °C for 2 hours to obtain catalyst DS1. The physicochemical properties of the catalyst are shown in Table 1. The catalyst was pressed into tablets at 15 MPa, crushed, and sieved through a 40-60 mesh screen for reaction evaluation. The catalyst evaluation procedure was the same as in Example 1, and the catalyst evaluation results are shown in Table 2.

[0109] Comparative Example 2

[0110] 15.02 g of indium nitrate tetrahydrate, 11.55 g of zirconium nitrate pentahydrate, and 4 g of zinc nitrate hexahydrate were dissolved in 50 mL of ethanol and 30 mL of deionized water to obtain the first solution. 32 g of urea was dissolved in 80 mL of ethanol and 50 mL of deionized water to obtain the second solution. The second solution was poured into the first solution and stirred at room temperature for 4 hours. After mixing thoroughly, the mixture was transferred to a hydrothermal reactor and heated to 120°C in a drying oven. The temperature was maintained for 20 hours, followed by natural cooling and stirring for aging. The mixture was then naturally filtered, washed three times with deionized water, filtered three times under vacuum, dried at 60°C for 2 hours, and calcined at 350°C for 3 hours to obtain catalyst DS2. The physicochemical properties of the catalyst are shown in Table 1. The catalyst was pressed into tablets at 15 MPa, crushed, and screened into 40-60 mesh powder for reaction evaluation. The catalyst evaluation steps were the same as in Example 1, and the catalyst evaluation results are shown in Table 2.

[0111] Comparative Example 3

[0112] 18 mmol Cu(NO3)2·3H2O, 9 mmol Zn(NO3)2·6H2O, and 3 mmol Al(NO3)3·9H2O were weighed and prepared into a 100 mL aqueous solution. 36 mmol Na2CO3 was weighed and prepared into a 100 mL aqueous solution. 200 mL of deionized water was placed in a 500 mL beaker, and a pH meter was inserted. The metal salt solution and Na2CO3 aqueous solution were co-precipitated at 70 °C under concurrent flow, with a stirring speed of 600 r / min, pH controlled at 7, and a precipitation rate of 3 mL / min. The resulting precipitate was aged at 70 °C for 1 h, cooled, and naturally filtered. The precipitate was washed five times with deionized water until no sodium ions were present in the filtrate. The filtrate was then filtered under vacuum, dried at 60 °C, and calcined in air at 350 °C for 3 h to obtain catalyst DS3. The physicochemical properties of the catalyst are shown in Table 1. The catalyst powder was pressed into tablets at 15 MPa, crushed, and screened to a mesh size of 40-60 for evaluation. The catalyst evaluation procedure was the same as in Example 1, and the evaluation results are shown in Table 2.

[0113] Comparative Example 4

[0114] The method was followed as in Example 1, except that the microwave output power was 200W, the reaction temperature was 80℃, and the reaction was maintained at that temperature for 3 hours. Catalyst DS4 containing a composite support was obtained, and its physicochemical properties are shown in Table 1. The catalyst evaluation results are shown in Table 2.

[0115] Comparative Example 5

[0116] Following the method in Example 1, except that 15.02 g of indium nitrate tetrahydrate and 4 g of zinc nitrate hexahydrate were dissolved in 100 mL of ethanol and 50 mL of deionized water to obtain solution A. Catalyst DS5 containing the composite support was obtained, and the physicochemical properties of the catalyst are shown in Table 1. The catalyst evaluation results are shown in Table 2.

[0117] Table 1

[0118]

[0119]

[0120] Table 2

[0121]

[0122] Combining the results in Tables 1 and 2, it can be seen that, compared with traditional hydrothermal synthesis, the catalyst containing a composite support prepared by microwave-assisted hydrothermal synthesis using specific precipitants or templates in response to microwave conditions has the characteristics of large specific surface area and uniform composition. It exhibits high catalytic activity and high methanol selectivity in the reaction of carbon dioxide hydrogenation to methanol.

[0123] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A catalyst containing a composite support for the hydrogenation of carbon dioxide to methanol, characterized in that, The catalyst comprises a composite support and an active metal component supported on the composite support; The composite carrier comprises a(AO) x )-b(BO y )-c(CO z ), wherein A is selected from at least one of In and Mo, B is selected from at least one of Zr, Ce, La and Al, and C is selected from at least one of Zn, Ca and Mg; wherein a = 0.1-0.7, b = 0.01-0.5, c = 0.01-0.4, x = 1-3, y = 1-3, z = 1-3; The catalyst has a specific surface area of ​​50-100 m². 2 / g; The active metal component is at least one of Pd, Pt and Au; The composite carrier was obtained by microwave-assisted hydrothermal synthesis.

2. The catalyst according to claim 1, wherein, a=0.3-0.6, b=0.01-0.4, c=0.01-0.

3.

3. The catalyst according to claim 1, wherein, Based on the total weight of the catalyst, the content of the composite support is 50-99.9 wt%, and the content of the active metal component, calculated as oxide, is 0.1-50 wt%.

4. The catalyst according to claim 3, wherein, Based on the total weight of the catalyst, the content of the composite support is 60-99.8 wt%, and the content of the active metal component, calculated as oxide, is 0.2-40 wt%.

5. A method for preparing a catalyst containing a composite support for the hydrogenation of carbon dioxide to methanol, characterized in that, Includes the following steps: (1) Provide a mixed solution containing salt A, salt B, salt C and auxiliaries; Wherein, A is selected from at least one of In and Mo, B is selected from at least one of Zr, Ce, La, and Al, and C is selected from at least one of Zn, Ca, and Mg; the auxiliary agent is a precipitant and a template agent; (2) The mixed solution is reacted under microwave reaction conditions; The microwave reaction conditions include: microwave output power of 500-2000W, reaction temperature of 60-200℃, and reaction time of 0.5-24h. (3) The product obtained in step (2) is washed, dried and calcined to obtain a composite carrier; (4) Introduce an active metal component onto the composite support to obtain a catalyst containing the composite support; The active metal is selected from at least one of Pd, Pt, and Au.

6. The preparation method according to claim 5, wherein, In the mixed solution, the total concentration of salts A, B, and C, based on the molar amounts of elements A, B, and C, is 0.1-4 mol / L.

7. The preparation method according to claim 6, wherein, In the mixed solution, the total concentration of salts A, B, and C, based on the molar amounts of elements A, B, and C, is 0.2-2 mol / L.

8. The preparation method according to claim 7, wherein, In the mixed solution, the molar ratio of salt A: salt B: salt C, based on the molar amounts of elements A, B, and C, is (0.1-0.7):(0.01-5):(0.01-4).

9. The preparation method according to claim 8, wherein, In the mixed solution, the molar ratio of salt A: salt B: salt C, based on the molar amounts of elements A, B, and C, is (0.3-0.6):(0.01-0.4):(0.01-0.3).

10. The preparation method according to claim 5, wherein, Salt A, salt B, and salt C are each independently selected from at least one of the nitrate, acetate, sulfate, and halide of A, B, and C.

11. The preparation method according to claim 5, wherein, The mixed solution also contains a solvent.

12. The preparation method according to claim 11, wherein, The solvent is water and / or ethanol.

13. The preparation method according to claim 5, wherein, The precipitant is selected from at least one of ammonia, ammonium carbonate, urea, citric acid, oxalic acid, and ethylenediaminetetraacetic acid.

14. The preparation method according to claim 5, wherein, The molar amount of the precipitant is 1-3 times the stoichiometric ratio of the atomic number of metals A, B, and C during precipitation or coordination theory.

15. The preparation method according to claim 5, wherein, The template agent is selected from at least one of the following: hexadecyltrimethylammonium bromide, polyoxyethylene-polyoxypropylene-polyoxyethylene amphiphilic block copolymer, polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer, polyoxyethylene-polyoxypropylene block polyether, polyethylene glycol, and polyoxyethylene ether.

16. The preparation method according to claim 5, wherein, The ratio of the amount of the template agent to the total mass of salts A, B, and C is 0.01-10:

1.

17. The preparation method according to claim 5, wherein, In step (2), the microwave reaction conditions include: microwave output power of 500-1500W, reaction temperature of 120-200℃, and reaction time of 1-8h.

18. The preparation method according to claim 5, wherein, The method also includes, After the microwave reaction in step (2) is completed, natural cooling and aging are carried out.

19. The preparation method according to claim 18, wherein, The aging time is 1-3 hours.

20. The preparation method according to claim 5, wherein, In step (3), the drying conditions include drying at 60-130℃ for 1-4 hours.

21. The preparation method according to claim 5, wherein, In step (3), the calcination conditions include calcination at 200-600℃ for 1-6 hours.

22. The preparation method according to claim 21, wherein, The calcination conditions include calcination at 250-400℃ for 2-4 hours.

23. The preparation method according to claim 5, wherein, The process of introducing the active metal component in step (4) includes: immersing the composite support in a salt solution of the active metal, and then drying and calcining it to obtain a catalyst containing the composite support.

24. The preparation method according to claim 23, wherein, The drying conditions include drying at 30-60°C for 0.5-3 hours under vacuum.

25. The preparation method according to claim 23, wherein, The calcination conditions include calcination at 200-600℃ for 2-6 hours.

26. The preparation method according to claim 23, wherein, The salt of the active metal is selected from the organic salt and / or inorganic salt of the active metal.

27. The preparation method according to claim 26, wherein, The inorganic salt of the active metal is selected from at least one of the nitrate, acetate, sulfate and halide of the active metal.

28. The preparation method according to claim 23, wherein, The concentration of the salt solution of the active metal is 0.1-3 mol / L, based on the molar amount of the active metal.

29. The preparation method according to claim 23, wherein, The amount of active metal salt solution used is such that the content of active metal component in the prepared catalyst, calculated as oxide, is 0.1-50 wt%.

30. The preparation method according to claim 29, wherein, The amount of active metal salt solution used is such that the content of active metal component in the prepared catalyst, calculated as oxide, is 0.2-40 wt%.

31. The preparation method according to claim 23, wherein, The volume ratio of the amount of the active metal salt solution to the water absorption of the composite carrier is 1-1.5:

1.

32. The catalyst containing a composite support prepared by the preparation method according to any one of claims 5-31.

33. A method for preparing methanol by hydrogenation of carbon dioxide, the method comprising: In the process of preparing methanol by hydrogenation of carbon dioxide, carbon dioxide and hydrogen are brought into contact in the presence of a catalyst. The catalyst includes the catalyst containing a composite support as described in any one of claims 1-4 and 32.

34. The method according to claim 33, wherein, The conditions for the carbon dioxide hydrogenation reaction to prepare methanol include: a reaction pressure of 1-8 MPa, a reaction temperature of 200-400℃, and a volume hourly space velocity of 2000-30000 h⁻¹. -1 The H2 / CO2 molar ratio is 1-8.

35. The method according to claim 33, wherein, The catalyst is also pre-reduced before use.

36. The method according to claim 35, wherein, The pre-reduction treatment conditions include: reduction at 200-600℃ for 1-12 hours in an H2 and / or CO atmosphere, a pre-reduction pressure of 0.1-1 MPa, and a volume hourly space velocity of 500-100000 h⁻¹. -1 .

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