Modified indium oxide carbon composite material, preparation method thereof, and method for preparing methanol by carbon dioxide hydrogenation

Abstract

This invention relates to the field of catalysts and discloses a modified indium oxide carbon composite material and its preparation method, as well as a method for preparing methanol by carbon dioxide hydrogenation. The preparation method includes the following steps: (1) preparing a dispersion containing indium salt, modifier, carbon source and water; the modifier is zirconium oxide with a monoclinic crystal form; (2) reacting the dispersion in the supercritical state of water, and then heat-treating the obtained product; wherein the mass ratio of the indium salt and the modifier, calculated as oxides, is 1-6:1. This invention uses a simple and efficient supercritical fluid deposition technology. By introducing monoclinic zirconium oxide as a modifier, the indium salt instantly reaches a supersaturated state in the supercritical solution, forming a large number of crystal nuclei, and can effectively control the crystal orientation of indium oxide, thus obtaining a modified indium oxide carbon composite material containing cubic indium oxide / hexagonal indium oxide mixed crystals. The catalyst has good catalytic activity and stability.

Description

Technical Field

[0001] This invention relates to the field of catalysts, specifically to a modified indium oxide carbon composite material and its preparation method, and a method for preparing methanol by hydrogenation of carbon dioxide. Background Technology

[0002] Methanol, as an important raw material for chemicals and a substitute for fossil fuels, can be produced by reacting CO2 with H2 from renewable energy sources. This not only addresses greenhouse gas control but is also an effective way to replace fossil fuels.

[0003] In the CO2 hydrogenation to methanol reaction, modified copper-based catalysts are the most frequently reported catalysts, while traditional Cu-based catalysts for syngas-to-methanol production have been extensively studied in CO2-to-methanol conversion. However, for Cu-based catalysts, high activity of reactive side reactions (RWGS), H2O-induced sintering of the active phase, and poor stability limit their further application. In other catalytic systems, the high cost of precious metals and the low activity and easy migration of ZnO also limit their further application in this field. In2O3 possesses moderate CO2 and CO adsorption capacity, exhibiting significantly better methanol selectivity than Cu, Co, and precious metal catalysts, as well as higher catalytic activity than ZnO catalysts, thus attracting widespread attention from researchers. In the CO2 hydrogenation to methanol reaction, indium-based catalysts exhibit high methanol selectivity, but their CO2 conversion rate is not high. Designing and developing more effective modified indium oxide catalysts is of great significance for the industrial application of CO2 hydrogenation to methanol, although significantly improving its catalytic performance still faces considerable challenges. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of complex preparation process, poor reproducibility, and insufficient catalytic activity and stability of indium oxide catalysts in the existing technology for CO2 hydrogenation. This invention provides a modified indium oxide carbon composite material and its preparation method, as well as a method for preparing methanol by carbon dioxide hydrogenation. The modified indium oxide carbon composite material prepared by this method has high reactivity and high selectivity for the target product.

[0005] To achieve the above objectives, the present invention provides a method for preparing a modified indium oxide carbon composite material, comprising the following steps:

[0006] (1) Prepare a dispersion containing indium salt, modifier, carbon source and water;

[0007] The modifier is zirconium oxide with a monoclinic crystal structure;

[0008] (2) The dispersion is reacted in the supercritical state of water, and the resulting product is then heat-treated.

[0009] The mass ratio of the indium salt to the modifier, calculated as oxide, is 1-6:1.

[0010] A second aspect of the present invention provides a modified indium oxide carbon composite material prepared by the above-described preparation method;

[0011] The modified indium oxide carbon composite material includes indium oxide, a modifying element, and carbon; wherein the indium oxide includes cubic indium oxide and hexagonal indium oxide, the modifying element exists at least partially in the form of zirconium oxide, the zirconium oxide has a monoclinic crystal form, and the mass ratio of indium oxide to the modifying element (calculated as oxide) is 1.5-3:1.

[0012] A third aspect of the present invention provides a method for preparing methanol by hydrogenation of carbon dioxide, the method comprising:

[0013] Under the conditions of preparing methanol by hydrogenation of carbon dioxide, carbon dioxide and hydrogen are contacted in the presence of a catalyst; the catalyst is the modified indium oxide carbon composite material described in the second aspect.

[0014] This invention employs a simple and efficient supercritical fluid deposition technique. By introducing monoclinic zirconium oxide as a modifier, the indium salt instantly reaches a supersaturated state in the supercritical solution, forming a large number of crystal nuclei. Furthermore, it effectively controls the crystallization orientation of indium oxide, resulting in a modified indium oxide-carbon composite material containing a mixture of cubic and hexagonal indium oxide crystals. Simultaneously, the monoclinic zirconium oxide helps to regulate the oxygen hole concentration in the catalyst, further improving the catalyst's catalytic activity and stability. Attached Figure Description

[0015] Figure 1 This is the X-ray diffraction pattern of the modified indium oxide carbon composite material prepared in Example 1. Detailed Implementation

[0016] 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.

[0017] The first aspect of this invention provides a method for preparing a modified indium oxide carbon composite material, comprising the following steps:

[0018] (1) Prepare a dispersion containing indium salt, modifier, carbon source and water;

[0019] The modifier is zirconium oxide with a monoclinic crystal structure;

[0020] (2) The dispersion is reacted in the supercritical state of water, and the resulting product is then heat-treated.

[0021] The mass ratio of the indium salt to the modifier, calculated as oxide, is 1-6:1.

[0022] According to the present invention, supercritical water has strong reactivity and wide solubility. In a supercritical water environment, the solubility of metal oxides is low, resulting in a high nucleation rate, which is beneficial for the synthesis of nanoparticles. Under supercritical conditions, the monoclinic zirconia induces the crystal orientation of indium oxide, causing the indium salt to instantly reach supersaturation in the supercritical solution, forming a large number of crystal nuclei. This results in the catalyst simultaneously containing cubic and hexagonal indium oxide, forming a cubic / hexagonal indium oxide mixed crystal.

[0023] According to the present invention, the mass ratio of the indium salt to the modifier, calculated as oxide, is 1-6:1, for example, typical but not limiting ratios such as 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, or a range between the two. By controlling the amount of modifier within the above-mentioned preferred range, the catalytic activity and stability of the catalyst can be further improved while controlling the crystallization orientation of indium oxide. This may be due to the regulatory effect of the monoclinic zirconium oxide on the oxygen hole concentration in the catalyst. Preferably, the mass ratio of the indium salt to the modifier, calculated as oxide, is 1.5-3:1.

[0024] According to the present invention, preferably, the mass ratio of the total amount of the indium salt and modified metal (calculated as oxides) to the carbon source in the dispersion is 0.1-2:1, more preferably 0.2-1:1.

[0025] In this invention, there is no specific limitation on the type of carbon source, as long as it can provide carbon. Preferably, the carbon source is selected from at least one of starch, maltose, sucrose, glucose, cellulose, citric acid, fumaric acid, maleic acid, succinic acid, malic acid, tartaric acid, gluconic acid, terephthalic acid, pyridine dicarboxylic acid, ethylenediaminetetraacetic acid, and trimesic acid; more preferably, it is selected from at least one of sucrose, maleic acid, terephthalic acid, pyridine dicarboxylic acid, and tartaric acid.

[0026] In this invention, the modifier is zirconium oxide with a monoclinic crystal form. The source of the modifier is not particularly limited; it can be commercially available or prepared using any method known in the art. To further improve the catalytic activity of the modified indium oxide-carbon composite material, preferably, the average grain size of the modifier is 5-25 nm, more preferably 5-18 nm. In the above preferred cases, this is beneficial for both the crystallization orientation of indium oxide and the dispersion of zirconium oxide, further helping to control the oxygen hole concentration in the modified indium oxide-carbon composite material, and further improving the catalyst activity and stability.

[0027] In this invention, the average grain size of the modifier is calculated using JADE software.

[0028] In one specific embodiment of the present invention, the preparation method of the modifier includes: mixing a zirconium source and a precipitant, and carrying out a hydrothermal reaction at 120-200°C, preferably 150-200°C, for 15-25 hours, and then drying and calcining the product obtained from the hydrothermal reaction.

[0029] 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.

[0030] Preferably, the molar ratio of the amount of precipitant to the amount of zirconium source (calculated as zirconium element) is 4-15:1, more preferably 6-12:1.

[0031] The present invention has a wide range of choices for the types of precipitants. Preferably, the first precipitant is selected from at least one of urea, ammonia, (NH4)2CO3, Na2CO3 and NaOH, and is preferably urea.

[0032] According to a preferred embodiment of the present invention, the drying temperature is 80-150°C and the time is 15-25 hours.

[0033] According to a preferred embodiment of the present invention, the calcination temperature is 400-600℃ and the time is 3-6h.

[0034] According to the present invention, preferably, the concentration of indium salt in the dispersion is 0.1-4 mol / L, more preferably 0.15-0.8 mol / L.

[0035] This invention does not particularly limit the type of indium salt; any soluble indium salt conventionally used in the art can be applied to this invention. The soluble salt can be an inorganic salt and / or an organic compound; preferably, the soluble salt is selected from at least one of nitrates, sulfates, acetates, chlorides, and metal alkoxides.

[0036] In a further preferred embodiment, the dispersion also contains an oxidant, preferably H2O2, and preferably the oxidant is provided in solution form; by introducing an oxidant, the oxidizing power of supercritical water can be further improved.

[0037] Preferably, the amount of oxidant used is 0.001-1% by mass, more preferably 0.001-0.01 wt%, based on the total mass of the dispersion.

[0038] In this invention, there are no special requirements for the preparation method of the dispersion in step (1). The indium salt, modifier, and carbon source can be dispersed in water first, and then the oxidant can be introduced. Alternatively, the indium salt, modifier, and oxidant can be dissolved in water first, and then the carbon source can be added. The solvent water can be introduced in any of the above processes, as long as the total amount of water in the dispersion can meet the concentration requirements of the indium salt. For example, the solvent water in the mixed solution can be introduced separately as a solvent for the indium salt and / or the oxidant, or it can be added together.

[0039] To ensure sufficient dispersion of the indium salt, modifier, and carbon source, the dispersion is preferably prepared under stirring conditions.

[0040] According to the present invention, the reaction in step (2) can proceed spontaneously in the supercritical state of water. Therefore, the present invention has a wide range of specific conditions for the reaction, as long as the supercritical state of water is met.

[0041] According to a preferred embodiment of the present invention, in step (2), the reaction conditions include: a temperature of 400-600℃; a reaction pressure of 23-45MPa; and a reaction time of 1-200min; preferably, the temperature is 400-520℃; the reaction pressure is 24-35MPa; and the reaction time is 20-150min.

[0042] According to a specific embodiment of the present invention, the method further includes solid-liquid separation, optionally washing and drying, of the reaction product in step (2), followed by the heat treatment. Specifically, the solid-liquid separation process may include: depressurizing and cooling the reaction system, and filtering to achieve gas-solid-liquid separation. In the present invention, any conventional methods and conditions can be used for washing and drying, which are well known to those skilled in the art and will not be described in detail here.

[0043] According to the present invention, preferably, the heat treatment conditions include: a temperature of 250-500°C and a time of 1-5 hours under an inert atmosphere; preferably, a temperature of 350-420°C and a time of 1.5-3 hours.

[0044] In this invention, the inert atmosphere refers to a protective gas that does not participate in the reaction, such as nitrogen and / or argon.

[0045] A second aspect of the present invention provides a modified indium oxide carbon composite material prepared by the above preparation method.

[0046] The modified indium oxide carbon composite material includes indium oxide, modifying elements, and carbon; wherein the indium oxide includes cubic indium oxide and hexagonal indium oxide, and the modifying elements are present at least partially in the form of zirconium oxide.

[0047] Preferably, the mass ratio of cubic indium oxide to hexagonal indium oxide is 1:0.1-50, more preferably 1:0.5-20.

[0048] The modified indium oxide carbon composite material contains indium oxide with two crystal structures: cubic and hexagonal. These two crystal structures are mixed phases formed by oriented crystallization in the presence of modifying elements, rather than a purely physical mixture.

[0049] In this invention, the X-ray diffraction pattern of the modified indium oxide-carbon composite material 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 catalytic activity and stability of the modified indium oxide-carbon composite material.

[0050] In this invention, the crystal morphology of each component in the modified indium oxide carbon composite material 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 (JCPDS06-0416). 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 belong 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.

[0051] A third aspect of the present invention provides a method for preparing methanol by hydrogenation of carbon dioxide, the method comprising:

[0052] Under the conditions of preparing methanol by hydrogenation of carbon dioxide, carbon dioxide and hydrogen are contacted in the presence of a catalyst; the catalyst is the modified indium oxide carbon composite material described in the second aspect.

[0053] Preferably, the conditions for the reaction of hydrogenating carbon dioxide to prepare methanol include: a reaction pressure of 0.3-8 MPa, a reaction temperature of 100-500 °C, and a volume hourly space velocity of 1500-40000 h⁻¹. -1 The H2 / CO2 molar ratio is 1-7; more preferably, the conditions for the carbon dioxide hydrogenation reaction to prepare methanol include: a reaction pressure of 1-5 MPa, a reaction temperature of 200-400℃, and a volume hourly space velocity of 10000-20000 h⁻¹. -1 The H2 / CO2 molar ratio is 4-6. Preferably, the carbon dioxide hydrogenation reaction is carried out in a fixed-bed reactor.

[0054] Preferably, prior to the contact, the method further includes: reducing and activating the catalyst under atmospheric pressure and in a hydrogen atmosphere. The conditions for the reduction and activation include: a reduction temperature of 150-250°C, preferably 180-220°C, and a time of 1-4 hours, preferably 1.5-3 hours.

[0055] The hydrogen atmosphere can be provided by hydrogen or a mixture of hydrogen and an inert gas. Preferably, the hydrogen atmosphere is provided by a mixture of hydrogen and an inert gas, wherein the volume fraction of hydrogen in the mixture is 10%-50%.

[0056] The present invention will be described in detail below through embodiments.

[0057] Unless otherwise specified, all raw materials used in the following examples and comparative examples are commercially available.

[0058] The crystal morphology of each component in the modified indium oxide carbon composite material was characterized by X-ray diffraction. In the X-ray diffraction pattern of standard cubic indium oxide, characteristic diffraction peaks were 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 were observed at 2θ of 22.4°, 31.0°, 32.6°, and 45.7°, which belong 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.

[0059] Example 1

[0060] (1) Preparation of monoclinic zirconium oxide:

[0061] 42.68 g of ZrO(NO3)2·2H2O was dissolved in deionized water to a final volume of 400 mL, and the solution was stirred until dissolved. Then, 105.4 g of urea was weighed and added to the solution, and the mixture was stirred until dissolved. After dissolution, the solution was poured into a hydrothermal reactor, sealed, and placed in an oven at 180°C for 20 h for hydrothermal reaction. After the hydrothermal reaction was complete, the solution was allowed to cool naturally to room temperature. The reactor was then opened, and the hydrothermal product was filtered and washed. It was then dried in an oven at 120°C for 15 h. Finally, it was calcined in a muffle furnace at 400°C for 3 h to obtain ZrO2. XRD analysis showed that it had a monoclinic crystal form with an average particle size of 14.5 nm.

[0062] (2) 15.04g of In(NO3)3·4H2O and 2.37g of the monoclinic zirconium oxide were added to 100mL of deionized water, and 12g of sucrose were added. The mixture was stirred to prepare a mixed solution. The mixed solution was added to an autoclave, and 4g of 30wt% H2O2 solution and 120mL of deionized water were added. The temperature was then raised to 400℃ and the pressure was increased to 25MPa. The reaction was carried out for 20min. After the reaction was completed, the pressure was released and cooled to achieve gas-solid-liquid separation. The sample was washed, dried, and placed in a tube furnace and calcined at 350℃ for 3h in a N2 atmosphere to obtain the modified indium oxide carbon composite material A1.

[0063] The XRD pattern of the modified indium oxide-carbon composite material A1 is as follows: Figure 1As 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°; characteristic diffraction peaks of hexagonal indium oxide are observed at 2θ values ​​of 22.4°, 31.0°, 32.6°, and 45.7°; characteristic peaks of monoclinic zirconium oxide are observed at 2θ value of 30.3°; and characteristic peaks of carbon are observed at 2θ value of 26.2°. This demonstrates that the modified indium oxide carbon composite material contains a mixture of cubic and hexagonal indium oxide, with a mass ratio of 1:10.8. Simultaneously, zirconium exists at least partially in the form of monoclinic zirconium oxide.

[0064] Response evaluation

[0065] The modified indium oxide-carbon composite material was used as a catalyst in the hydrogenation of carbon dioxide to methanol. The reaction was carried out in a stainless steel reactor with an inner diameter of 8 mm. First, reduction was performed at 200°C for 2 h under a reducing atmosphere of 10% H₂ (vol.) / N₂. Then, carbon dioxide hydrogenation was carried out under the following conditions: 3 MPa, 300°C, and 9000 h⁻¹. -1 With n(H2) / n(CO2) = 4, the liquid product was collected in an ice-water bath after 100 h of reaction. The composition of the product was analyzed by gas chromatography, and the evaluation results are shown in Table 1.

[0066] Example 2

[0067] (1) Preparation of monoclinic zirconium oxide:

[0068] 7.23 g of ZrO(NO3)2·2H2O was dissolved in deionized water to a final volume of 100 mL, and the solution was stirred until dissolved. Then, 16.34 g of urea was weighed and added to the solution, and the mixture was stirred until dissolved. After dissolution, the solution was poured into a hydrothermal reactor, sealed, and placed in an oven at 160°C for 20 h for hydrothermal reaction. After the hydrothermal reaction was complete, the solution was allowed to cool naturally to room temperature. The reactor was then opened, and the hydrothermal product was filtered and washed. It was then dried in an oven at 110°C for 15 h. Finally, it was calcined in a muffle furnace at 450°C for 3 h to obtain ZrO2. XRD analysis showed that it had a monoclinic crystal form with an average particle size of 15.6 nm.

[0069] (2) 22.8g of In(NO3)3·4H2O and 5.45g of the monoclinic zirconium oxide were added to 100mL of deionized water, and 21g of fumaric acid were added. The mixture was stirred to prepare a mixed solution. The mixed solution was added to a high-pressure reactor, and 6g of 30wt% H2O2 solution and 120mL of deionized water were added. The temperature was then raised to 480℃ and the pressure was increased to 24MPa. The reaction was carried out for 25min. After the reaction was completed, the pressure was released and cooled to achieve gas-solid-liquid separation. The sample was washed, dried, and placed in a tube furnace and calcined at 380℃ for 2h in a N2 atmosphere to obtain modified indium oxide carbon composite material A2. XRD characterization showed that the modified indium oxide carbon composite material contained a mixture of cubic indium oxide and hexagonal indium oxide, and the mass ratio of cubic indium oxide to hexagonal indium oxide was 1:5.11.

[0070] The reaction was evaluated under the same conditions as in Example 1, and the evaluation results are shown in Table 1.

[0071] Example 3

[0072] (1) Preparation of monoclinic zirconium oxide:

[0073] 25.56 g of ZrO(NO3)2·2H2O was dissolved in deionized water to a final volume of 300 mL, and the solution was stirred until dissolved. Then, 64.67 g of urea was weighed and added to the solution, and the mixture was stirred until dissolved. After dissolution, the solution was poured into a hydrothermal reactor, sealed, and placed in an oven at 190 °C for 16 h for hydrothermal reaction. After the hydrothermal reaction was complete, the solution was allowed to cool naturally to room temperature. The reactor was then opened, and the hydrothermal product was filtered and washed. It was then dried in an oven at 100 °C for 16 h. Finally, it was calcined in a muffle furnace at 500 °C for 3 h to obtain ZrO2. XRD analysis showed that it had a monoclinic crystal form with an average particle size of 16.8 nm.

[0074] (2) 45.6 g of In(NO3)3·4H2O and 5.76 g of the monoclinic zirconium oxide were added to 300 mL of deionized water, along with 54 g of ethylenediaminetetraacetic acid. The mixture was stirred to prepare a mixed solution. The mixed solution was added to an autoclave, followed by 8 g of 30 wt% H2O2 solution and 300 mL of deionized water. The temperature was then raised to 520 °C and the pressure was increased to 25 MPa for 140 min. After the reaction, the pressure was released and cooled to achieve gas-solid-liquid separation. The sample was washed, dried, and calcined in a tube furnace at 400 °C for 2 h in a N2 atmosphere to obtain the modified indium oxide carbon composite material A3. XRD characterization confirmed that the modified indium oxide carbon composite material contained a mixture of cubic and hexagonal indium oxide phases, with a mass ratio of 1:8.78.

[0075] The reaction was evaluated under the same conditions as in Example 1, and the evaluation results are shown in Table 1.

[0076] Example 4

[0077] The method was followed in Example 1, except that the amount of monoclinic zirconium oxide used in step (2) was 1.66 g. Modified indium oxide carbon composite material A4 was obtained. XRD characterization confirmed that the modified indium oxide carbon composite material contained a mixture of cubic and hexagonal indium oxide, with a mass ratio of cubic to hexagonal indium oxide of 1:17.3.

[0078] The reaction was evaluated under the same conditions as in Example 1, and the evaluation results are shown in Table 1.

[0079] Example 5

[0080] The method was followed in Example 1, except that the amount of monoclinic zirconium oxide used in step (2) was 4.75 g. Modified indium oxide carbon composite material A5 was obtained. XRD characterization confirmed that the modified indium oxide carbon composite material contained a mixture of cubic and hexagonal indium oxide, with a mass ratio of cubic to hexagonal indium oxide of 1:0.36.

[0081] The reaction was evaluated under the same conditions as in Example 1, and the evaluation results are shown in Table 1.

[0082] Example 6

[0083] Following the method of Example 1, except that the preparation of monoclinic zirconium oxide included: dissolving 42.68 g of ZrO(NO3)2·2H2O in deionized water to a final volume of 400 mL and stirring until dissolved. Then, 105.4 g of urea was weighed and added to the above solution, and stirring continued until dissolved. After dissolution, the solution was poured into a hydrothermal reactor, sealed, and placed in an oven at 120°C for a hydrothermal reaction for 24 h. After the hydrothermal reaction was complete, the solution was allowed to cool naturally to room temperature. The hydrothermal reactor was opened, and the hydrothermal product was filtered and washed. It was then dried in an oven at 110°C for 12 h. Finally, it was calcined in a muffle furnace at 500°C for 4 h to obtain ZrO2, which, according to XRD analysis, exhibited a monoclinic crystal form with an average particle size of 18.9 nm.

[0084] The prepared modified indium oxide carbon composite material A6 was characterized by XRD to show that it contained a mixture of cubic and hexagonal indium oxide, with a mass ratio of 1:49.

[0085] The reaction was evaluated under the same conditions as in Example 1, and the evaluation results are shown in Table 1.

[0086] Example 7

[0087] The method is the same as in Example 1, except that no H2O2 solution is added.

[0088] The prepared modified indium oxide carbon composite material A7 was characterized by XRD to show that it contained a mixture of cubic and hexagonal indium oxide, with a mass ratio of 1:14.25.

[0089] The reaction was evaluated under the same conditions as in Example 1, and the evaluation results are shown in Table 1.

[0090] Example 8

[0091] The method is the same as in Example 1, except that the reaction conditions in step (2) are: 350°C, pressure increased to 20MPa, and reaction is carried out for 15 minutes.

[0092] The prepared modified indium oxide carbon composite material A8 was characterized by XRD to show that it contained a mixture of cubic and hexagonal indium oxide, with a mass ratio of 1:35.

[0093] The reaction was evaluated under the same conditions as in Example 1, and the evaluation results are shown in Table 1.

[0094] Comparative Example 1

[0095] The method was followed in Example 1, except that cubic zirconia of equal mass was used to replace zirconia with a monoclinic crystal structure. The resulting modified indium oxide-carbon composite material DA1 was characterized by XRD to show that it contained a mixture of cubic and hexagonal indium oxide, with a mass ratio of 1:49.

[0096] The reaction was evaluated under the same conditions as in Example 1, and the evaluation results are shown in Table 1.

[0097] Comparative Example 2

[0098] The method was followed in Example 1, except that the amount of monoclinic zirconium oxide used in step (2) was 8.35 g. Modified indium oxide carbon composite material DA2 was obtained. XRD characterization confirmed that the modified indium oxide carbon composite material contained a mixture of cubic and hexagonal indium oxide, with a mass ratio of 1:0.03.

[0099] The reaction was evaluated under the same conditions as in Example 1, and the evaluation results are shown in Table 1.

[0100] Table 1

[0101]

[0102] As can be seen from the results in Table 1, the carbon dioxide hydrogenation to methanol catalyst provided by this invention has good carbon dioxide catalytic activity, can improve the conversion rate of carbon dioxide while maintaining methanol selectivity, has good stability, and the carbon dioxide hydrogenation effect is obvious.

[0103] 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 method for preparing a modified indium oxide-carbon composite material, characterized in that, Includes the following steps: (1) Prepare a dispersion containing indium salt, modifier, carbon source and water; The modifier is zirconium oxide with a monoclinic crystal structure; (2) The dispersion is reacted in the supercritical state of water, and then the resulting product is heat-treated. The mass ratio of the indium salt to the modifier, calculated as oxide, is 1-6:

1.

2. The preparation method according to claim 1, wherein, The mass ratio of the indium salt to the modifier, calculated as oxide, is 1.5-3:

1.

3. The preparation method according to claim 1, wherein, In the dispersion, the total amount of the indium salt and modifier (calculated as oxides) to the carbon source is in a mass ratio of 0.1-2:

1.

4. The preparation method according to claim 3, wherein, In the dispersion, the total amount of the indium salt and modifier (calculated as oxides) to the carbon source is in a mass ratio of 0.2-1:

1.

5. The preparation method according to claim 1 or 2, wherein, The average grain size of the modifier is 5-25 nm.

6. The preparation method according to claim 5, wherein, The average grain size of the modifier is 10-18 nm.

7. The preparation method according to claim 1, wherein, The concentration of indium salt in the dispersion is 0.1-4 mol / L.

8. The preparation method according to claim 1, wherein, The indium salt is a soluble salt of indium, and the soluble salt is an inorganic salt and / or an organic salt.

9. The preparation method according to claim 8, wherein, The soluble salt is selected from at least one of nitrates, sulfates, acetates, chlorides, and metal alkoxides.

10. The preparation method according to claim 1, wherein, The carbon source is selected from at least one of sucrose, starch, glucose, maltose, cellulose, citric acid, maleic acid, fumaric acid, succinic acid, tartaric acid, malic acid, gluconic acid, terephthalic acid, ethylenediaminetetraacetic acid, pyridine dicarboxylic acid, and pyromellitic acid.

11. The preparation method according to claim 10, wherein, The carbon source is selected from at least one of sucrose, maleic acid, terephthalic acid, pyridine dicarboxylic acid, and tartaric acid.

12. The preparation method according to claim 1, wherein, The dispersion also contains an oxidizing agent.

13. The preparation method according to claim 12, wherein, The oxidant is H2O2.

14. The preparation method according to claim 12, wherein, The oxidant is provided in solution form.

15. The preparation method according to claim 12, wherein, Based on the total mass of the dispersion, the amount of oxidant used is 0.001-1 by mass.

16. The preparation method according to claim 15, wherein, Based on the total mass of the dispersion, the amount of oxidant used is 0.001-0.01 wt%.

17. The preparation method according to claim 1, wherein, In step (2), the reaction conditions include: temperature of 400-600℃; reaction pressure of 23-45MPa; and reaction time of 1-200min.

18. The preparation method according to claim 17, wherein, In step (2), the reaction conditions include: temperature of 400-520℃; reaction pressure of 24-35MPa; and reaction time of 20-150min.

19. The preparation method according to claim 1, wherein, The heat treatment conditions include: under an inert atmosphere, at a temperature of 250-500℃, for a time of 1-5 hours.

20. The preparation method according to claim 19, wherein, The heat treatment conditions include: a temperature of 350-420℃ and a time of 1.5-3h.

21. The modified indium oxide carbon composite material prepared by the preparation method according to any one of claims 1-20; The modified indium oxide carbon composite material comprises indium oxide, modifying elements, and carbon; wherein, The indium oxide includes cubic indium oxide and hexagonal indium oxide, and the modifying element exists at least partially in the form of zirconium oxide, which has a monoclinic crystal form.

22. 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 is the modified indium oxide carbon composite material as described in claim 21.

23. The method according to claim 22, wherein, The reaction conditions for the preparation of methanol by carbon dioxide hydrogenation include: a reaction pressure of 0.3-8 MPa, a reaction temperature of 100-500℃, and a volume hourly space velocity of 1500-40000 h⁻¹. -1 The H2 / CO2 molar ratio is 1-7.

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