Carbon dioxide hydrogenation to methanol catalyst and preparation method thereof, and method for preparing methanol by carbon dioxide hydrogenation

Abstract

The application relates to the technical field of carbon dioxide hydrogenation catalysts, and discloses a carbon dioxide hydrogenation methanol catalyst, a preparation method of the carbon dioxide hydrogenation methanol catalyst and a carbon dioxide hydrogenation methanol method, the catalyst comprising modified indium oxide and an active metal component loaded on the modified indium oxide, wherein the active metal component is Pd; the modified indium oxide comprises indium oxide and a modified element, the modified element is zirconium, the indium oxide comprises cubic phase indium oxide and hexagonal phase indium oxide, and the mass ratio of the cubic phase indium oxide to the hexagonal phase indium oxide is 1:0.1-50; the modified element at least partially exists in the form of zirconium oxide, and the zirconium oxide has a monoclinic crystal type. The catalyst provided by the application has high carbon dioxide conversion rate and methanol selectivity, and the catalyst has good stability.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide hydrogenation catalyst technology, specifically to a carbon dioxide hydrogenation catalyst for methanol production and its preparation method, and a method for producing methanol by carbon dioxide hydrogenation. Background Technology

[0002] Global warming is a serious problem facing humankind, and carbon dioxide (CO2), as a major greenhouse gas, has received widespread attention, making CO2 emission reduction an urgent priority. As the simplest C1 resource, CO2 chemistry has become a research hotspot in recent years due to its potential usability and economic viability. Methanol is a viable clean alternative fuel to gasoline and diesel, and also one of the most basic organic chemical raw materials. Utilizing H2 from renewable energy sources to catalytically convert carbon dioxide into methanol is one of the effective ways to rationally utilize CO2. Improvements in carbon dioxide hydrogenation technology for methanol production are crucial for the successful development of a "methanol economy" and "liquid sunshine."

[0003] Common catalysts for CO2 hydrogenation to methanol mainly include copper-based catalysts and noble metal-supported catalysts. Copper-based catalysts often suffer from low catalytic activity, low methanol selectivity, and short lifespan; noble metal catalysts are costly; and the low activity and easy migration of ZnO also limit its further application. In2O3 possesses moderate CO2 and CO adsorption capacity and is easily supported and surface-modified, promoting the activation of CO2 and H2 and stabilizing key intermediates to achieve high activity, high selectivity, and stability. However, the catalytic performance of In2O3 catalysts in current technologies still needs further improvement. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem in the prior art that it is difficult to simultaneously achieve methanol selectivity and carbon dioxide conversion rate in carbon dioxide hydrogenation to methanol catalysts, and to provide a carbon dioxide hydrogenation to methanol catalyst and its preparation method, as well as a method for preparing methanol by carbon dioxide hydrogenation. This catalyst has excellent catalytic effect in the carbon dioxide hydrogenation to methanol production, and can improve the carbon dioxide conversion rate while effectively improving methanol selectivity.

[0005] To achieve the above objectives, the first aspect of the present invention provides a catalyst for the hydrogenation of carbon dioxide to methanol, the catalyst comprising modified indium oxide and an active metal component supported on the modified indium oxide, wherein the active metal component is Pd;

[0006] The modified indium oxide comprises indium oxide and a modifying element, wherein the modifying element is zirconium, and the indium oxide comprises cubic indium oxide and hexagonal indium oxide, wherein the mass ratio of cubic indium oxide to hexagonal indium oxide is 1:0.1-50; the modifying element exists at least partially in the form of zirconium oxide, wherein the zirconium oxide has a monoclinic crystal form.

[0007] A second aspect of this invention provides a method for preparing a catalyst for the hydrogenation of carbon dioxide to methanol, comprising the following steps:

[0008] (1) Mix indium salt, first precipitant and modifier to obtain precipitate mother liquor;

[0009] The modifier is zirconium oxide with a monoclinic crystal structure;

[0010] (2) The precipitated mother liquor is aged;

[0011] The aging conditions include: a temperature of 120-200℃ and a time of 8-48 hours.

[0012] (3) The product obtained in step (2) is subjected to solid-liquid separation, and then dried and calcined to obtain modified indium oxide;

[0013] (4) Contact the solution containing palladium salt with the modified indium oxide.

[0014] The third aspect of the present invention provides a catalyst for the hydrogenation of carbon dioxide to methanol prepared by the above preparation method.

[0015] A fourth aspect of the present invention provides a method for preparing methanol by carbon dioxide hydrogenation, the method comprising: contacting carbon dioxide and hydrogen under carbon dioxide hydrogenation conditions in the presence of a catalyst; wherein the catalyst is a carbon dioxide hydrogenation catalyst for methanol preparation provided in the first aspect or the third aspect.

[0016] The carbon dioxide hydrogenation to methanol catalyst provided by this invention has high carbon dioxide hydrogenation catalytic activity, can simultaneously improve the conversion rate of carbon dioxide and the selectivity of methanol, and has good catalyst stability.

[0017] The method for preparing a catalyst for the hydrogenation of carbon dioxide to methanol provided by this invention can effectively control the crystal orientation of indium oxide under the action of monoclinic zirconium oxide, synthesize cubic indium oxide / hexagonal indium oxide mixed crystal material, and then load the active metal component palladium. The process steps are simple, which can effectively reduce its production cost and enable mass production. Attached Figure Description

[0018] Figure 1 This is the X-ray diffraction pattern of the modified indium oxide prepared in Example 1;

[0019] Figure 2 This is the result of catalyst A1 prepared in Example 1 operating stably for 1000 hours in the reaction of carbon dioxide hydrogenation to methanol. Detailed Implementation

[0020] 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.

[0021] The first aspect of the present invention provides a catalyst for the hydrogenation of carbon dioxide to methanol, the catalyst comprising modified indium oxide and an active metal component supported on the modified indium oxide, wherein the active metal component is Pd;

[0022] The modified indium oxide comprises indium oxide and a modifying element, wherein the modifying element is zirconium, and the indium oxide comprises cubic indium oxide and hexagonal indium oxide, wherein the mass ratio of cubic indium oxide to hexagonal indium oxide is 1:0.1-50; the modifying element exists at least partially in the form of zirconium oxide, wherein the zirconium oxide has a monoclinic crystal form.

[0023] In the catalyst described in this invention, the modified indium oxide is a mixed-crystal material, meaning that the indium oxide simultaneously possesses both cubic and hexagonal crystal structures. These two crystal structures are a mixed phase formed through oriented crystallization in the presence of the modifying element, rather than a purely physical mixture. The inventors discovered that during the synthesis of hexagonal indium oxide, a cubic / hexagonal indium oxide mixed crystal can be formed under the synergistic effect of monoclinic zirconium oxide. This mixed-crystal structure allows the catalyst to maintain high methanol selectivity while improving CO2 conversion, thus enhancing the catalyst's reactivity. Simultaneously, the synergistic effect of the active metal element Pd with indium oxide improves reaction stability and results in a low catalyst deactivation rate.

[0024] In this invention, the X-ray diffraction pattern of the catalyst confirms that the modifying element exists at least partially in the form of zirconium oxide, and that the zirconium oxide has a monoclinic crystal form. The modifying element promotes the formation of the aforementioned cubic / hexagonal indium oxide mixed crystal structure, and the introduction of monoclinic zirconium oxide helps to regulate the oxygen hole concentration in the catalyst, further improving the catalyst's activity and stability.

[0025] In this invention, the crystal morphology of each component in the catalyst is characterized by X-ray diffraction. In the X-ray diffraction pattern of standard cubic indium oxide, characteristic diffraction peaks are observed at 2θ of 21.5°, 30.6°, 35.5°, 51.0°, and 60.7°, which correspond to the (211), (222), (400), (440), and (622) crystal planes of cubic indium oxide, respectively (JCPDS 06-0416). In the X-ray diffraction pattern of standard hexagonal indium oxide, characteristic diffraction peaks are observed at 2θ of 22.4°, 31.0°, 32.6°, and 45.7°, which are attributed to the (012), (104), (110), and (024) crystal planes of hexagonal indium oxide, respectively (JCPDS 22-0336). The content of each crystal form of indium oxide was further calculated using the formula Wc(%) = [Ac / (Ac+3.4Ah)]×100%. Here, Ac and Ah represent the fitting intensity (fitting peak area) of the c-In2O3(222) and h-In2O3(104) crystal planes, respectively, and the constant coefficient 3.4 is the ratio of the fitting intensity of the two peaks, which can be obtained through preliminary XRD experiments.

[0026] In this invention, preferably, the mass ratio of cubic indium oxide to hexagonal indium oxide is 1:3-22. For example, it can be a typical but not limiting ratio or a range between two points, such as 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, 1:21, 1:22, etc. Controlling the ratio of cubic indium oxide to hexagonal indium oxide in the catalyst within the above-mentioned preferred range can achieve both high methanol selectivity and high CO2 conversion.

[0027] In this invention, the selection range for the indium and zirconium content in the modified indium oxide is relatively wide. Preferably, based on the total weight of the modified indium oxide, the indium content, calculated as oxide, is 40-90 wt%, preferably 60-80 wt%; the zirconium content is 10-60 wt%, preferably 20-40 wt%. For example, the indium content, calculated as oxide, can be typical but not limiting contents such as 60 wt%, 61 wt%, 62 wt%, 63 wt%, 64 wt%, 65 wt%, 66 wt%, 67 wt%, 68 wt%, 69 wt%, 70 wt%, 71 wt%, 72 wt%, 73 wt%, 74 wt%, 75 wt%, 76 wt%, 77 wt%, 78 wt%, 79 wt%, 80 wt%, or a range between the two. The zirconium content, calculated as oxide, can be a typical but not limiting content or a range between the two, such as 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, 35wt%, 36wt%, 37wt%, 38wt%, 39wt%, 40wt%, etc.

[0028] In this invention, the contents of indium oxide and zirconium oxide are determined by XRF method.

[0029] In this invention, it is not excluded that some of the modifying elements exist in the form of indium / zirconium composite oxides.

[0030] In existing technologies, zirconium oxide is more often used as a catalyst support, such as the supported indium oxide catalysts disclosed in US20200061582A1 and US20210322957A1. In these catalysts, zirconium oxide exhibits high crystallinity and its content is much higher than that of indium oxide because the zirconium oxide support disperses the indium oxide. However, in this invention, as mentioned above, zirconium is used as a modifying element to promote mixed crystal formation and improve catalyst activity. Preferably, the zirconium oxide content in the catalyst is not higher than the indium oxide content.

[0031] In a further preferred embodiment, the modified indium oxide has an indium to zirconium mass ratio of 1-6:1, based on the oxide content. For example, typical but not limiting ratios include 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, and 6:1. Preferably, the indium to zirconium mass ratio is 1.5-3.5:1, based on the oxide content. In the above preferred embodiments, it is beneficial to form an appropriate amount of cubic / hexagonal indium oxide mixed crystals, and simultaneously beneficial to improving the catalytic activity of the catalyst.

[0032] In this invention, the selection range for the content of the active metal component in the catalyst is relatively wide, and those skilled in the art can select it according to the actual application requirements. Preferably, based on the total amount of the catalyst, the content of the modified indium oxide is 85-99.99 wt%, more preferably 90-99.5 wt%; and based on elemental composition, the content of the active metal component is 0.01-15 wt%, more preferably 0.5-10 wt%. Within the above-mentioned preferred composition range, it is beneficial to balance the catalytic activity and stability of the catalyst.

[0033] A second aspect of this invention provides a method for preparing a catalyst for the hydrogenation of carbon dioxide to methanol, comprising the following steps:

[0034] (1) Mix indium salt, first precipitant and modifier to obtain precipitate mother liquor;

[0035] The modifier is zirconium oxide with a monoclinic crystal structure;

[0036] (2) The precipitated mother liquor is aged;

[0037] The aging conditions include: a temperature of 120-200℃ and a time of 8-48 hours.

[0038] (3) The product obtained in step (2) is subjected to solid-liquid separation, and then dried and calcined to obtain modified indium oxide;

[0039] (4) Contact the solution containing palladium salt with the modified indium oxide.

[0040] The inventors of this invention discovered in their research that during the aging process of the precipitate mother liquor, monoclinic zirconium oxide can induce the crystal orientation of indium oxide, so that the catalyst simultaneously contains cubic and hexagonal indium oxide, forming a cubic / hexagonal indium oxide mixed crystal; and the monoclinic zirconium oxide helps to regulate the oxygen hole concentration in the catalyst, further improving the catalyst activity and stability.

[0041] This invention offers a wide range of options for the amounts of indium salt and modifier. Preferably, the amounts of indium salt and modifier are such that, based on the total weight of the modified indium oxide, the indium content, calculated as oxide, is 40-90 wt%, preferably 60-80 wt%; and the zirconium content is 10-60 wt%, preferably 20-40 wt%. For example, the indium content, calculated as oxide, can be 60 wt%, 61 wt%, 62 wt%, 63 wt%, 64 wt%, 65 wt%, 66 wt%, 67 wt%, 68 wt%, 69 wt%, 70 wt%, 71 wt%, 72 wt%, 73 wt%, 74 wt%, etc. Typical, but not limiting, contents of zirconium, such as 75wt%, 76wt%, 77wt%, 78wt%, 79wt%, 80wt%, or a range thereof, may be present. The zirconium content, calculated as oxide, may be typical, but not limiting, contents of 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, 35wt%, 36wt%, 37wt%, 38wt%, 39wt%, 40wt%, or a range thereof, may be present.

[0042] In a further preferred embodiment, the mass ratio of the indium salt to the modifier, calculated as oxide, is 1-6:1, for example, typical but not limiting ratios or ranges between 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, etc. Preferably, the mass ratio of the indium salt to the modifier, calculated as oxide, is 1.5-3.5:1.

[0043] According to a preferred embodiment of the present invention, the mixing in step (1) is carried out under stirring conditions. The present invention does not impose any particular limitation on the stirring conditions, as long as sufficient dispersion of the components is ensured. Preferably, the mixing temperature is 20-50°C, and the mixing time is 1-10 hours.

[0044] The present invention does not have a particular limitation on the mixing order. The indium salt, the first precipitant, and the modifier can be added to the reactor together for mixing, or the indium salt and the first precipitant can be mixed first, and then the modifier can be added. In a further preferred embodiment, the mixing in step (1) includes: a first mixing of the indium salt and the precipitant, followed by a second mixing with the modifier. Using the above preferred embodiments facilitates the formation of appropriate amounts of cubic and hexagonal indium oxide, improving the methanol selectivity and CO2 conversion rate of the catalyst.

[0045] According to the present invention, preferably, the precipitate mother liquor further contains a solvent, wherein the solvent is an organic solvent and / or water. More preferably, the solvent is a mixture of an organic solvent and water, wherein the volume ratio of the organic solvent to water is preferably 1-5:1.

[0046] In this invention, the organic solvent may be an alcohol and / or an amide solvent. Preferably, the organic solvent is selected from at least one of ethanol, methanol, isopropanol, ethylene glycol, triethylene glycol, and N,N-dimethylacetamide.

[0047] According to a particularly preferred embodiment of the present invention, the solvent is a mixture of ethanol and water, wherein the volume ratio of ethanol to water is 1-3:1.

[0048] The present invention does not have a particular limitation on the timing of the introduction of the solvent. The indium salt and the first precipitant can be added to the solvent to obtain the indium salt solution and the first precipitant solution, and then the mixing described in step (1) can be carried out. Alternatively, the indium salt, the first precipitant and the modifier can be mixed and then the solvent can be added for dispersion.

[0049] In a further preferred embodiment, the indium salt is provided in the form of an indium salt solution with a concentration of 0.1-0.8 mol / L, preferably 0.1-0.4 mol / L.

[0050] The present invention allows for a wide range of choices regarding the specific type of indium salt, as long as indium is available. Conventional soluble indium salts in the art can be used in this invention. For example, the indium salt can be selected from at least one of indium nitrate, indium chloride, and indium sulfate. The indium salt may also contain water of crystallization, as is well known to those skilled in the art and will not be elaborated upon here.

[0051] Preferably, the first precipitant is provided in the form of a first precipitant solution, the concentration of which is 1-3 mol / L, preferably 1.5-2.8 mol / L.

[0052] In this invention, the compositions of the solvents in the indium salt solution and the first precipitant solution may be the same or different, both satisfying the definition range of the solvent composition described above.

[0053] Preferably, the first precipitant is selected from at least one of urea, ammonia, (NH4)2CO3, Na2CO3 and NaOH, and is preferably urea.

[0054] According to the present invention, preferably, the molar ratio of the first precipitant to the indium salt (based on indium element) is 5-10:1, for example, it can be a typical but not limiting ratio such as 5:1, 5.2:1, 5.4:1, 5.6:1, 5.8:1, 6:1, 6.2:1, 6.4:1, 6.6:1, 6.8:1, 7:1, 7.2:1, 7.4:1, 7.6:1, 7.8:1, 8:1, 8.2:1, 8.4:1, 8.6:1, 8.8:1, 9:1, 9.2:1, 9.4:1, 9.6:1, 9.8:1, 10:1. Preferably, the molar ratio of the first precipitant to the indium salt (based on indium element) is 5.5-9.8:1.

[0055] In this invention, the modifier is zirconium oxide with a monoclinic crystal form. This invention does not particularly limit the source of the modifier; it can be commercially available or prepared using any method known in the art.

[0056] In one specific embodiment of the present invention, the preparation method of the modifier includes: mixing a zirconium source and a second precipitant, carrying out a hydrothermal reaction at 120-200°C for 15-25 hours, and then drying and calcining the product obtained from the hydrothermal reaction.

[0057] According to a preferred embodiment of the present invention, the drying temperature is 80-150°C and the time is 15-25 hours.

[0058] According to a preferred embodiment of the present invention, the calcination temperature is 400-600℃ and the time is 3-6h.

[0059] The present invention allows for a wide range of choices regarding the specific type of zirconium source, as long as zirconium element can be provided, such as zirconium nitrate and / or zirconium oxynitrate. The zirconium source may also contain water of crystallization, as is well known to those skilled in the art and will not be elaborated upon here.

[0060] In this invention, the selection range of the second precipitant and the first precipitant can be the same, and their specific selection can be the same or different. This invention does not have any particular limitation on this.

[0061] Preferably, the molar ratio of the second precipitant to the zirconium source (calculated as zirconium element) is 5-10:1, more preferably 5-8:1.

[0062] According to the present invention, preferably, in step (2), the aging conditions include: a temperature of 120-150°C, such as typical but not limiting aging temperatures of 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, etc.; and an aging time preferably of 16-20 hours, such as typical but not limiting times of 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, etc. By using the modifier and the aging temperature and time, it is possible to control the formation of an appropriate amount of cubic indium oxide in the hexagonal indium oxide, but an excessively long aging time may result in an excessive content of cubic indium oxide.

[0063] According to the present invention, in step (3), the solid-liquid separation can be carried out using conventional operating methods and conditions in the art, and the solid-liquid separation process preferably also includes a washing step. For example, the product can be washed with deionized water, and then the solid-liquid separation can be carried out by centrifugation.

[0064] According to the present invention, preferably, in step (3), the drying conditions include: a temperature of 50-100°C, preferably 60-80°C; and a time of 12-25h, preferably 14-22h.

[0065] Preferably, in step (3), the calcination conditions include: a temperature of 300-600℃, preferably 350-450℃; and a time of 1-8h, preferably 3-6h.

[0066] In this invention, the contact described in step (4) is used to load palladium onto modified indium oxide, and can be carried out using conventional active metal component loading methods in the art.

[0067] According to a specific embodiment of the present invention, the contact in step (4) includes: impregnating the modified indium oxide with a solution containing palladium salt.

[0068] In a further preferred embodiment, the contact in step (4) is carried out under stirring conditions. The present invention does not particularly limit the specific stirring conditions, as long as they can promote the dispersion of the active metal components. Preferably, the contact temperature is 20-35°C and the contact time is 0.5-2 hours.

[0069] Preferably, the amount of palladium salt solution and modified indium oxide is such that the content of modified indium oxide in the prepared catalyst is 85-99.99 wt%, preferably 90-99.5 wt%; and the content of palladium is 0.01-15 wt%, preferably 0.5-10 wt%.

[0070] In this invention, the selection range of palladium salts is relatively wide, and conventional palladium-soluble salts in the art can all be used in this invention. Preferably, the palladium salt is selected from at least one of palladium nitrate, chloride, and acetate.

[0071] Preferably, the concentration of the palladium salt-containing solution is 0.001-0.05 wt%.

[0072] According to the present invention, step (4) further includes: subjecting the product obtained by contact to a second drying and a second calcination.

[0073] Preferably, the second drying is rotary evaporation drying. The preferred conditions for rotary evaporation drying are: temperature 35-72℃, rotation speed 10-30 rpm, vacuum degree 0.05-0.1 MPa, and evaporation time 1-3 h.

[0074] Preferably, the conditions for the second calcination include: a temperature of 300-500℃ and a time of 1-5 hours.

[0075] In one specific embodiment of the present invention, step (4) further includes: shaping and sieving the product obtained from the second calcination. The present invention does not particularly limit the shaping method; those skilled in the art can choose according to actual needs, for example, tableting can be used.

[0076] The third aspect of the present invention provides a catalyst for the hydrogenation of carbon dioxide to methanol prepared by the above preparation method.

[0077] The fourth aspect of the present invention provides a method for preparing methanol by carbon dioxide hydrogenation, the method comprising: contacting carbon dioxide and hydrogen in the presence of a catalyst under carbon dioxide hydrogenation conditions; wherein the catalyst is the carbon dioxide hydrogenation catalyst for methanol preparation described in the first or third aspect.

[0078] Preferably, the carbon dioxide hydrogenation conditions include: a reaction temperature of 200-400℃, more preferably 240-280℃; a reaction pressure of 1-5 MPa, more preferably 3-5 MPa; and a volume hourly space velocity of 4500-18000 h⁻¹. -1 Preferably 8000-12000h -1 The H2 / CO2 molar ratio is 1-6, preferably 3-6.

[0079] According to a preferred embodiment of the present invention, the catalyst further includes a step of reducing and activating the active metal component before being used in the reaction of carbon dioxide hydrogenation to prepare methanol.

[0080] Preferably, the reduction activation includes: reducing and activating the catalyst by contacting it with hydrogen gas at atmospheric pressure.

[0081] Preferably, the reduction activation conditions include: a reduction temperature of 180-220℃, more preferably 190-200℃; and a reduction time of 1-4h, more preferably 1.5-2.5h.

[0082] According to the present invention, the reduction activation can be carried out in pure hydrogen or in a mixture of hydrogen and an inert gas. If it is carried out in a mixture of hydrogen and nitrogen and / or argon, the volume content of hydrogen in the mixture can be 5-15%.

[0083] The present invention will be described in detail below through embodiments.

[0084] Unless otherwise specified, all raw materials used in the following examples and comparative examples were purchased commercially from Sinopharm Group.

[0085] The phase structure, cubic indium oxide, and hexagonal indium oxide content in the catalyst were determined by X-ray diffraction. The X-ray diffraction pattern of standard cubic indium oxide showed characteristic diffraction peaks at 2θ values ​​of 21.5°, 30.6°, 35.5°, 51.0°, and 60.7°, corresponding to the (211), (222), (400), (440), and (622) crystal planes of cubic indium oxide (JCPDS06-0416), respectively. The X-ray diffraction pattern of standard hexagonal indium oxide showed characteristic diffraction peaks at 2θ values ​​of 22.4°, 31.0°, 32.6°, and 45.7°, belonging to the (012), (104), (110), and (024) crystal planes of hexagonal indium oxide (JCPDS 22-0336), respectively. The content of each crystal form of indium oxide was further calculated using the formula Wc(%) = [Ac / (Ac+3.4Ah)]×100%. Here, Ac and Ah represent the fitting intensity (fitting peak area) of the c-In2O3(222) and h-In2O3(104) crystal planes, respectively, and the constant coefficient 3.4 is the ratio of the fitting intensity of the two peaks, which can be obtained through preliminary XRD experiments.

[0086] The content of each component in the catalyst was determined by XRF method.

[0087] The composition of the products from the reaction of carbon dioxide hydrogenation to methanol was analyzed using a gas chromatograph purchased from Agilent Technologies (China) Co., Ltd.

[0088] Example 1

[0089] (1) Dissolve 6.65g of ZrO(NO3)2·2H2O in deionized water to a final volume of 70mL and stir until dissolved. Then weigh 10.03g of urea and add it to the above solution, stirring until dissolved. After dissolution, pour the solution into a 100mL hydrothermal reactor, seal it, and place it in an oven at 170℃ for hydrothermal reaction for 20h. After the hydrothermal reaction is complete, allow it to cool naturally to room temperature. Open the hydrothermal reactor, filter and wash the hydrothermal product. Then dry it in an oven at 110℃ for 14h. Finally, calcine it in a muffle furnace at 400℃ for 4h to obtain monoclinic ZrO2;

[0090] (2) Add 6.2g of In(NO3)3·4H2O to a mixture of 50mL anhydrous ethanol and 25mL deionized water to obtain a solution containing indium salt. Add 8g of urea to a mixture of 60mL anhydrous ethanol and 20mL deionized water to obtain a precipitant solution. Add the precipitant solution dropwise to the solution containing indium salt at 30℃. Then add 1.3g of monoclinic ZrO2 and stir thoroughly at 200rpm for 4h to obtain the precipitate mother liquor.

[0091] (3) Add the precipitate mother liquor obtained in step (2) into a 100mL hydrothermal synthesis reactor lined with polytetrafluoroethylene, place it in a forced-air drying oven and let it stand for aging. The aging temperature is 120℃ and the aging time is 18h to form a precipitate.

[0092] (4) After the product obtained in step (3) is naturally cooled to room temperature, it is centrifuged, washed with deionized water until the pH is 8, dried at 60°C for 15 hours, and then calcined at 380°C for 3 hours to obtain modified indium oxide.

[0093] X-ray diffraction pattern of modified indium oxide as follows Figure 1 As shown, characteristic diffraction peaks of cubic indium oxide are observed at 2θ values ​​of 21.5°, 30.6°, 35.5°, 51.0°, and 60.7°, while characteristic diffraction peaks of hexagonal indium oxide are observed at 2θ values ​​of 22.4°, 31.0°, 32.6°, and 45.7°, proving that the modified indium oxide contains a mixed crystal of cubic and hexagonal indium oxide. Simultaneously, a characteristic peak of monoclinic zirconium oxide is observed at 2θ value of 30.3°, proving that zirconium in the modified indium oxide exists at least partially in the form of monoclinic zirconium oxide.

[0094] (5) Weigh 0.15g of palladium nitrate and dissolve it in 10mL of deionized water to obtain a palladium salt solution. Then weigh 4g of the above-mentioned modified indium oxide and add it to the palladium salt solution. Stir at 25℃ for 1h, then dry by rotary evaporation at 40℃, 20ppm, and 0.1MPa for 2h. Finally, calcine at 350℃ for 4h to obtain catalyst A1. Compress the catalyst into tablets and sieve them to 40-60 mesh. The content of each component in the catalyst is shown in Table 1.

[0095] (6) The reaction for the hydrogenation of carbon dioxide to methanol was carried out in a stainless steel reactor with an inner diameter of 8 mm. Catalyst A1 was used as the catalyst. The reaction was carried out under a reducing atmosphere of 10% H2 (vol.) / N2 at 200℃ for 2 h, followed by the reaction. The reaction conditions were as follows: reaction pressure of 5 MPa, reaction temperature of 285℃, and volume hourly space velocity of the raw materials (carbon dioxide and hydrogen) of 18000 h⁻¹. -1 The H2 / CO2 molar ratio was 5. After reacting for 1000 h, the liquid product was collected in an ice-water bath. The product composition was analyzed by gas chromatography, and the evaluation results are shown in Table 2. The stable operation results are as follows: Figure 2 As shown.

[0096] Example 2

[0097] (1) Dissolve 3.56 g of ZrO(NO3)2·2H2O in deionized water to a final volume of 50 mL and stir until dissolved. Then weigh 6.13 g of urea and add it to the above solution and continue stirring until dissolved. After dissolution, pour the solution into a 100 mL hydrothermal reactor, seal it, and place it in an oven at 150 °C for hydrothermal reaction for 15 h. After the hydrothermal reaction is complete, allow it to cool naturally to room temperature. Open the hydrothermal reactor, filter and wash the hydrothermal product. Then dry it in an oven at 100 °C for 12 h. Finally, calcine it in a muffle furnace at 400 °C for 4 h to obtain monoclinic ZrO2;

[0098] (2) Add 5.9g of In(NO3)3·4H2O to a mixture of 80mL anhydrous ethanol and 40mL deionized water to obtain a solution containing indium salt. Add 9.2g of urea to a mixture of 80mL anhydrous ethanol and 30mL deionized water to obtain a precipitant solution. Add the precipitant solution dropwise to the solution containing indium salt at 30℃. Then add 0.8g of monoclinic ZrO2 and stir thoroughly at 150rpm for 7h to obtain the precipitate mother liquor.

[0099] (3) Add the precipitate mother liquor obtained in step (2) into a 100mL hydrothermal synthesis reactor lined with polytetrafluoroethylene, place it in a forced-air drying oven and let it stand for aging at 130℃ for 20h to form a precipitate.

[0100] (4) After the product obtained in step (3) is naturally cooled to room temperature, it is centrifuged, washed with deionized water until the centrifuged precipitate reaches pH 8, dried at 80°C for 12 hours, and then calcined at 450°C for 3 hours to obtain modified indium oxide.

[0101] (5) Weigh 0.02g of palladium nitrate and dissolve it in 8mL of deionized water to obtain a palladium salt solution. Then weigh 1g of the above modified indium oxide and add it to the palladium salt solution. Stir at 25℃ for 1h, then dry by rotary evaporation at 35℃, 22ppm and 0.1MPa for 3h, and finally calcine at 350℃ for 4h to obtain catalyst A2. Press the tablets and sieve them to 40-60 mesh. The composition is shown in Table 1.

[0102] (6) The reaction of carbon dioxide hydrogenation to prepare methanol was carried out in a stainless steel reactor with an inner diameter of 8 mm. Catalyst A2 was used as the catalyst. The reduction was carried out at 200 °C for 2 h under a reducing atmosphere of 10% H2 (vol.) / N2, followed by the reaction. The reaction conditions were as follows: reaction pressure of 1 MPa, reaction temperature of 400 °C, and volume hourly space velocity of the raw materials (carbon dioxide and hydrogen) of 9000 h⁻¹. -1 The H2 / CO2 molar ratio was 4. After reacting for 1000 h, the liquid product was collected in an ice-water bath. The composition of the product was analyzed by gas chromatography, and the evaluation results are shown in Table 2.

[0103] Example 3

[0104] (1) Weigh 8.57 g of ZrO(NO3)2·2H2O, dilute to 90 mL with deionized water, and stir to dissolve. Then weigh 10.56 g of urea and add it to the above solution, stirring to dissolve. After dissolution, pour into a 100 mL hydrothermal reactor, seal, and place in an oven at 180 °C for hydrothermal reaction for 15 h. After the hydrothermal reaction is complete, allow to cool naturally to room temperature. Open the hydrothermal reactor, filter and wash the hydrothermal product. Then place it in an oven at 110 °C for drying for 16 h. Finally, calcine in a muffle furnace at 500 °C for 3 h to obtain monoclinic ZrO2;

[0105] (2) Add 9.1g of In(NO3)3·4H2O to a mixture of 40mL anhydrous ethanol and 24mL deionized water to obtain a solution containing indium salt. Add 8g of urea to a mixture of 40mL anhydrous ethanol and 10mL deionized water to obtain a precipitant solution. Add the precipitant solution dropwise to the solution containing indium salt at 30℃. Then add 2g of monoclinic ZrO2 and stir thoroughly at 150rpm for 6h to obtain the precipitate mother liquor.

[0106] (3) Add the precipitate mother liquor obtained in step (2) into a 100mL hydrothermal synthesis reactor lined with polytetrafluoroethylene, place it in a forced-air drying oven and let it stand for aging. The aging temperature is 160℃ and the aging time is 20h to form a precipitate.

[0107] (4) After the product obtained in step (3) is naturally cooled to room temperature, it is centrifuged, washed with deionized water until the centrifuged precipitate reaches pH 7, dried at 60°C for 20 h, and then calcined at 350°C for 3 h to obtain modified indium oxide.

[0108] (5) Weigh 0.07g of palladium nitrate and dissolve it in 10mL of deionized water to obtain a palladium salt solution. Then weigh 2g of the above modified indium oxide and add it to the palladium salt solution. Stir at 25℃ for 1h, then dry by rotary evaporation at 55℃, 15ppm and 0.1MPa for 1.5h. Finally, calcine at 350℃ for 4h to obtain catalyst A3. Compress the catalyst into tablets and sieve them to 40-60 mesh. The composition is shown in Table 1.

[0109] (6) The reaction for preparing methanol by hydrogenation of carbon dioxide was carried out in a stainless steel reactor with an inner diameter of 8 mm. The above-mentioned catalyst A3 was used as the catalyst. The reduction was carried out at 200 °C for 2 h under a reducing atmosphere of 10% H2 (vol.) / N2, and then the reaction was carried out. The reaction conditions were as follows: reaction pressure of 3 MPa, reaction temperature of 280 °C, and volume hourly space velocity of raw materials (carbon dioxide and hydrogen) of 9000 h⁻¹. -1 The H2 / CO2 molar ratio was 4. After reacting for 1000 h, the liquid product was collected in an ice-water bath. The composition of the product was analyzed by gas chromatography, and the evaluation results are shown in Table 2.

[0110] Example 4

[0111] (1) Dissolve 5.36 g of ZrO(NO3)2·2H2O in deionized water to a final volume of 60 mL and stir until dissolved. Then weigh 7.67 g of urea and add it to the above solution, stirring until dissolved. After dissolution, pour the solution into a 100 mL hydrothermal reactor, seal it, and place it in an oven at 170 °C for hydrothermal reaction for 20 h. After the hydrothermal reaction is complete, allow it to cool naturally to room temperature. Open the hydrothermal reactor, filter and wash the hydrothermal product. Then dry it in an oven at 120 °C for 15 h. Finally, calcine it in a muffle furnace at 500 °C for 3 h to obtain monoclinic ZrO2.

[0112] (2) Add 8.5g of In(NO3)3·4H2O to a mixture of 48mL of anhydrous ethanol and 25mL of deionized water to obtain a solution containing indium salt. Add 8g of urea to a mixture of 46mL of anhydrous ethanol and 12mL of deionized water to obtain a precipitant solution. Add the precipitant solution dropwise to the solution containing indium salt at 30℃. Then add 1g of monoclinic ZrO2 and stir thoroughly at 150rpm for 6h to obtain the precipitate mother liquor.

[0113] (3) Add the precipitate mother liquor obtained in step (2) into a 100mL hydrothermal synthesis reactor lined with polytetrafluoroethylene, place it in a forced-air drying oven and let it stand for aging. The aging temperature is 180℃ and the aging time is 20h to form a precipitate.

[0114] (4) After the product obtained in step (3) is naturally cooled to room temperature, it is centrifuged, washed with deionized water until the pH is 7, dried at 60°C for 24 hours, and then calcined at 300°C for 3 hours to obtain modified indium oxide.

[0115] (5) Weigh 0.05g of palladium nitrate and dissolve it in 10mL of deionized water to obtain a palladium salt solution. Then weigh 2g of the above modified indium oxide and add it to the palladium salt solution. Stir at 45℃ for 1h, then dry by rotary evaporation at 40℃, 18ppm and 0.1MPa for 2h, and finally calcine at 350℃ for 4h to obtain catalyst A4. Press the catalyst into tablets and sieve them to 40-60 mesh. The composition is shown in Table 1.

[0116] (6) The reaction for the hydrogenation of carbon dioxide to methanol was carried out in a stainless steel reactor with an inner diameter of 8 mm. The above-mentioned catalyst A4 was used as the catalyst. The reduction was carried out at 200 °C for 2 h under a reducing atmosphere of 10% H2 (vol.) / N2, and then the reaction was carried out. The reaction conditions were as follows: reaction pressure of 5 MPa, reaction temperature of 220 °C, and volume hourly space velocity of the raw materials (carbon dioxide and hydrogen) of 7000 h⁻¹. -1 The H2 / CO2 molar ratio was 6. After reacting for 1000 h, the liquid product was collected in an ice-water bath. The composition of the product was analyzed by gas chromatography, and the evaluation results are shown in Table 2.

[0117] Example 5

[0118] (1) Weigh 6.09 g of ZrO(NO3)2·2H2O, dilute to 90 mL with deionized water, and stir to dissolve. Then weigh 8.68 g of urea and add it to the above solution, stirring to dissolve. After dissolution, pour into a 100 mL hydrothermal reactor, seal, and place in an oven at 180 °C for hydrothermal reaction for 16 h. After the hydrothermal reaction is complete, allow to cool naturally to room temperature. Open the hydrothermal reactor, filter and wash the hydrothermal product. Then place it in an oven at 120 °C for drying for 16 h. Finally, calcine in a muffle furnace at 530 °C for 3 h to obtain monoclinic ZrO2;

[0119] (2) Add 6.3g of In(NO3)3·4H2O to a mixture of 60mL of anhydrous ethanol and 28mL of deionized water to obtain a solution containing indium salt. Add 6g of urea to a mixture of 65mL of anhydrous ethanol and 22mL of deionized water to obtain a precipitant solution. Add the precipitant solution dropwise to the solution containing indium salt at 30℃. Then add 1.0g of zirconium oxide and stir thoroughly at 220rpm for 5h to obtain the precipitate mother liquor.

[0120] (3) Add the precipitate mother liquor obtained in step (2) into a 100mL hydrothermal synthesis reactor lined with polytetrafluoroethylene, place it in a forced-air drying oven and let it stand for aging. The aging temperature is 140℃ and the aging time is 15h to form a precipitate.

[0121] (4) After the product obtained in step (3) is naturally cooled to room temperature, it is centrifuged, washed with deionized water until the pH is 8, dried at 60°C for 18 hours, and then calcined at 350°C for 3 hours to obtain modified indium oxide.

[0122] (5) Weigh 0.5g of palladium nitrate and dissolve it in 10mL of deionized water to obtain a salt solution. Then weigh 2g of modified indium oxide and add it to the salt solution. Stir at 25℃ for 2h, then dry by rotary evaporation at 40℃, 20ppm and 0.1MPa for 1h. Finally, calcine at 350℃ for 4h to obtain catalyst A5. Press the tablets and sieve them to 40-60 mesh. The composition is shown in Table 1.

[0123] (6) The reaction of carbon dioxide hydrogenation to prepare methanol was carried out in a stainless steel reactor with an inner diameter of 8 mm. The catalyst obtained in step (5) was used as the reaction catalyst. The reaction was carried out at 200 °C for 2 h under a reducing atmosphere of 10% H2 (vol.) / N2, and then the reaction was carried out. The reaction conditions were as follows: reaction pressure of 2 MPa, reaction temperature of 240 °C, and volume hourly space velocity of raw materials (carbon dioxide and hydrogen) of 15000 h⁻¹. -1 The H2 / CO2 molar ratio was 6. After reacting for 1000 h, the liquid product was collected in an ice-water bath. The composition of the product was analyzed by gas chromatography, and the evaluation results are shown in Table 2.

[0124] Example 6

[0125] The method of Example 1 was followed, except that the amount of monoclinic ZrO2 added was 2.2g, and the resulting catalyst was designated as A6. The contents of each component are shown in Table 1.

[0126] The activity of the prepared catalyst was evaluated in a fixed-bed reactor under the same reaction conditions as in Example 1. The test results are shown in Table 2.

[0127] Example 7

[0128] The method of Example 1 was followed, except that the amount of monoclinic ZrO2 added was 0.5g, and the resulting catalyst was designated as A7. The contents of each component are shown in Table 1.

[0129] The activity of the prepared catalyst was evaluated in a fixed-bed reactor under the same reaction conditions as in Example 1. The test results are shown in Table 2.

[0130] Example 8

[0131] The method of Example 1 was followed, except that the amount of Pd added was 0.03g, and the resulting catalyst was designated as A8. The contents of each component are shown in Table 1.

[0132] The activity of the prepared catalyst was evaluated in a fixed-bed reactor under the same reaction conditions as in Example 1. The test results are shown in Table 2.

[0133] Comparative Example 1

[0134] (1) Add 6.2g of In(NO3)3·4H2O to a mixture of 50mL anhydrous ethanol and 25mL deionized water to obtain a solution containing indium salt. Add 8g of urea to a mixture of 60mL anhydrous ethanol and 20mL deionized water to obtain a precipitant solution. Add the precipitant solution dropwise to the solution containing indium salt at 30℃ and stir thoroughly at 200rpm for 4h to obtain the precipitate mother liquor.

[0135] (2) Add the precipitate mother liquor obtained in step (1) into a 100mL hydrothermal synthesis reactor lined with polytetrafluoroethylene, place it in a forced-air drying oven and let it stand for aging at 120℃ for 18h to form a precipitate.

[0136] (3) After the product obtained in step (2) is naturally cooled to room temperature, it is centrifuged, washed with deionized water until the pH is 8, dried at 60°C for 15 hours, and then calcined at 380°C for 3 hours to obtain hexagonal indium oxide.

[0137] (4) Weigh 0.15g of palladium nitrate and dissolve it in 10mL of deionized water to obtain a palladium salt solution. Then weigh 4g of the indium oxide prepared above and add it to the palladium salt solution. Stir at 25℃ for 1h, then dry by rotary evaporation at 40℃, 20ppm, and 0.1MPa for 2h. Finally, calcine at 350℃ for 4h to obtain catalyst A1. Compress the catalyst into tablets and sieve them to 40-60 mesh. The content of each component in the catalyst is shown in Table 1.

[0138] (5) The activity of the prepared palladium-supported indium oxide was evaluated in a fixed-bed reactor under the same reaction conditions as in Example 1. The test results are shown in Table 2.

[0139] Comparative Example 2

[0140] The method of Example 1 is followed, except that in step (2), commercially available cubic zirconium oxide is used instead of monoclinic zirconium oxide. The resulting catalyst is denoted as DA2.

[0141] The activity of the prepared catalyst was evaluated in a fixed-bed reactor under the same reaction conditions as in Example 1. The test results are shown in Table 2.

[0142] Comparative Example 3

[0143] The method was followed as in Example 1, except that the aging temperature in step (3) was 80°C and the aging time was 10 hours. The resulting catalyst was designated DA3.

[0144] The activity of the prepared catalyst was evaluated in a fixed-bed reactor under the same reaction conditions as in Example 1. The test results are shown in Table 2.

[0145] Comparative Example 4

[0146] Commercially available cubic indium oxide was mixed and ground with hexagonal indium oxide prepared in Comparative Example 1 at a mass ratio of 1:19.4. Pd was then loaded onto the mixture according to the method in Example 1, and the resulting product was designated DA4. The activity of the prepared catalyst was evaluated in a fixed-bed reactor under the same reaction conditions as in Example 1. The test results are shown in Table 2.

[0147] Table 1

[0148]

[0149] Table 2

[0150]

[0151]

[0152] As can be seen from the results in Table 2, the carbon dioxide hydrogenation to methanol catalyst provided by the present invention has high carbon dioxide hydrogenation catalytic activity, can simultaneously improve the conversion rate of carbon dioxide and the selectivity of methanol, and has good catalyst stability.

[0153] 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 for the hydrogenation of carbon dioxide to methanol, characterized in that, The catalyst comprises modified indium oxide and an active metal component supported on the modified indium oxide, wherein the active metal component is Pd; The modified indium oxide comprises indium oxide and a modifying element, wherein the modifying element is zirconium, and the indium oxide comprises cubic indium oxide and hexagonal indium oxide, wherein the mass ratio of cubic indium oxide to hexagonal indium oxide is 1:0.1-50; the modifying element exists at least partially in the form of zirconium oxide, wherein the zirconium oxide has a monoclinic crystal form.

2. The catalyst according to claim 1, wherein, The mass ratio of cubic indium oxide to hexagonal indium oxide is 1:3-22.

3. The catalyst according to claim 1 or 2, wherein, Based on the total weight of the modified indium oxide, the indium content is 40-90 wt% and the zirconium content is 10-60 wt% (calculated as oxide).

4. The catalyst according to claim 3, wherein, Based on the total weight of the modified indium oxide, the indium content is 60-80 wt% and the zirconium content is 20-40 wt% (calculated as oxide).

5. The catalyst according to claim 1, wherein, The mass ratio of indium to zirconium, calculated as oxides, is 1-6:

1.

6. The catalyst according to claim 5, wherein, The mass ratio of indium to zirconium, calculated as oxides, is 1.5-3.5:

1.

7. The catalyst according to claim 1, wherein, Based on the total amount of the catalyst, the content of the modified indium oxide is 85-99.99 wt%; The content of the active metal component is 0.01-15 wt% by element.

8. The catalyst according to claim 7, wherein, Based on the total amount of the catalyst, the content of the modified indium oxide is 90-99.5 wt%; The content of the active metal component is 0.5-10 wt% by element.

9. A method for preparing a catalyst for the hydrogenation of carbon dioxide to methanol, characterized in that, Includes the following steps: (1) Mix indium salt, first precipitant and modifier to obtain precipitate mother liquor; The modifier is zirconium oxide with a monoclinic crystal structure; (2) The precipitated mother liquor is aged; The aging conditions include: a temperature of 120-200℃ and a time of 8-48 hours. (3) The product obtained in step (2) is subjected to solid-liquid separation, and then dried and calcined to obtain modified indium oxide; (4) Contact the solution containing palladium salt with the modified indium oxide.

10. The preparation method according to claim 9, wherein, The amounts of the indium salt and modifier are such that, based on the total weight of the modified indium oxide, the indium content is 40-90 wt% and the zirconium content is 10-60 wt%.

11. The preparation method according to claim 10, wherein, The amounts of the indium salt and modifier are such that, based on the total weight of the modified indium oxide, the indium content is 60-80 wt% and the zirconium content is 20-40 wt%.

12. The preparation method according to claim 9, wherein, The mass ratio of the indium salt to the modifier, calculated as oxide, is 1-6:

1.

13. The preparation method according to claim 12, wherein, The mass ratio of the indium salt to the modifier, calculated as oxide, is 1.5-3.5:

1.

14. The preparation method according to claim 9, wherein, The mixing described in step (1) is carried out under stirring conditions.

15. The preparation method according to claim 9, wherein, The mixing in step (1) includes: first mixing the indium salt and the first precipitant, and then second mixing with the modifier.

16. The preparation method according to claim 9, wherein, The precipitate mother liquor also contains a solvent, which is an organic solvent and / or water.

17. The preparation method according to claim 16, wherein, The solvent is a mixture of an organic solvent and water.

18. The preparation method according to claim 16, wherein, The organic solvent is selected from at least one of ethanol, methanol, isopropanol, ethylene glycol, triethylene glycol, and N,N-dimethylacetamide.

19. The preparation method according to claim 9, wherein, The molar ratio of the first precipitant to the indium salt (calculated as indium) is 5-10:

1.

20. The preparation method according to claim 19, wherein, The molar ratio of the amount of the first precipitant to the indium salt, calculated as indium, is 5.5-9.8:

1.

21. The preparation method according to claim 9, wherein, The indium salt is selected from at least one of indium nitrate, indium chloride, and indium sulfate.

22. The preparation method according to claim 21, wherein, The indium salt is provided in the form of an indium salt solution with a concentration of 0.1-0.8 mol / L.

23. The preparation method according to claim 9, wherein, The first precipitant is selected from at least one of urea, (NH4)2CO3, Na2CO3 and NaOH.

24. The preparation method according to claim 23, wherein, The first precipitant is provided in the form of a first precipitant solution, the concentration of which is 1-3 mol / L.

25. The preparation method according to claim 9, wherein, In step (2), the aging conditions include: a temperature of 120-150℃ and a time of 16-28h.

26. The preparation method according to claim 9, wherein, In step (3), the drying conditions include a temperature of 50-100℃ and a time of 12-25h.

27. The preparation method according to claim 9, wherein, In step (3), the calcination conditions include: a temperature of 300-600℃ and a time of 1-8h.

28. The preparation method according to claim 27, wherein, In step (3), the calcination conditions include: a temperature of 350-450℃ and a time of 3-6h.

29. The preparation method according to claim 9, wherein, The amount of palladium salt solution and modified indium oxide used is such that the content of modified indium oxide in the prepared catalyst is 85-99.99 wt% and the content of palladium is 0.01-15 wt%.

30. The preparation method according to claim 29, wherein, The amount of palladium salt solution and modified indium oxide used is such that the content of modified indium oxide in the prepared catalyst is 90-99.5 wt% and the content of palladium is 0.5-10 wt%.

31. The preparation method according to claim 9, wherein, The palladium salt is selected from at least one of palladium nitrate, chloride and acetate.

32. The preparation method according to claim 31, wherein, The concentration of the palladium salt-containing solution is 0.001-0.05 wt%.

33. The preparation method according to claim 9, wherein, The contact described in step (4) is carried out under stirring conditions, with a contact temperature of 20-35℃ and a contact time of 0.5-2h.

34. A catalyst for the hydrogenation of carbon dioxide to methanol prepared by the preparation method according to any one of claims 9-33.

35. A method for preparing methanol by hydrogenation of carbon dioxide, the method comprising: In the presence of a catalyst, carbon dioxide and hydrogen are brought into contact under carbon dioxide hydrogenation conditions; The catalyst is the carbon dioxide hydrogenation to methanol catalyst according to any one of claims 1-8 and 34.

36. The method according to claim 35, wherein, The conditions for carbon dioxide hydrogenation include: a reaction temperature of 200-400℃, a reaction pressure of 1-5 MPa, and a volume hourly space velocity of 4500-18000 h⁻¹. -1 The H2 / CO2 molar ratio is 1-6.

Images