A porous indium oxide catalyst, a method for preparing the same, and an application thereof

Abstract

The application provides a porous indium oxide catalyst and a preparation method and application thereof, and solves the technical problems of using multiple catalysts in the prior art step-by-step activation of carbon dioxide and hydrogen to prepare methanol, a complex catalyst system and a complicated preparation process. The application first controls the reaction temperature and reaction time through a simple one-step hydrothermal method in a strong alkali environment to prepare a cubic In(OH)3 precursor with uniform morphology, and then performs calcination and oxidation in an air atmosphere to convert the In(OH)3 into stable porous cubic structure In2O3.

Description

Technical Field

[0001] This invention belongs to the field of thermocatalysis technology, specifically relating to a porous indium oxide catalyst, its preparation method, and its application. Background Technology

[0002] Currently, methanol is mainly produced by the hydrogenation of carbon dioxide, with Cu / ZnO / Al2O3 as the primary catalyst. However, this catalyst system has several drawbacks. For example, the reaction requires high temperature and pressure conditions, which can easily trigger a reverse water-gas reaction, producing CO and H2O byproducts that deactivate the active sites, and causing ZnO agglomeration. Stepwise activation of carbon dioxide and hydrogen to produce methanol is a common process. While this method avoids high-temperature reaction conditions (because carbon dioxide readily forms carbonate compounds), it still faces challenges such as high-pressure reaction conditions, complex catalyst preparation processes, and the difficulty of using a single catalyst to simultaneously activate two molecules. For example, zirconium dioxide or cerium dioxide catalysts are used to produce dimethyl carbonate from carbon dioxide and methanol; Cu... (x) The / CeO2 catalyst enables the hydrogenation of organic carbonates (dimethyl carbonate) to methanol. In the stepwise activation process, two different catalysts are required to catalyze different reaction systems.

[0003] It is evident that in such heterogeneous catalytic reactions, the design and synthesis of catalysts play a crucial role in the reaction conditions and the catalytic performance during the reaction. However, as mentioned above, most existing catalysts are indeed difficult to achieve "one-to-many" application value, resulting in complex catalytic systems and cumbersome catalyst preparation processes.

[0004] In view of the current situation, this application proposes to design an integrated catalyst for the stepwise activation of carbon dioxide and hydrogen to produce methanol. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problems of the complex catalyst system and cumbersome preparation process in the existing stepwise activation of carbon dioxide and hydrogen to prepare methanol, and to provide a porous indium oxide catalyst, its preparation method and application.

[0006] The concept of this invention:

[0007] Because the reaction conditions of the stepwise activation process are milder, our research team aims to design a catalyst that can be used in the stepwise activation process to address the problems it faces. Considering the following points need to be met in the catalyst design for the preparation of dimethyl carbonate from carbon dioxide and methanol: 1) It must be able to adsorb and activate CO2 and CH3OH to convert them into the corresponding active intermediates; 2) It must not be loaded with other metals to avoid competitive adsorption of the two molecules and deactivation of oxygen vacancies in the catalyst. In the catalyst design for the preparation of methanol from dimethyl carbonate and hydrogen, the following points need to be met: 1) The steric hindrance when oxygen in dimethyl carbonate inserts into oxygen vacancies in the catalyst; 2) Whether the activation sites of hydrogen affect the adsorption of dimethyl carbonate, and thus affect further activation.

[0008] Therefore, considering the design requirements and current bottlenecks of catalysts for the production of dimethyl carbonate from carbon dioxide and methanol, and the production of methanol from dimethyl carbonate and hydrogen, our research team proposes to use In2O3 with controllable oxygen vacancies as a catalyst for stepwise activation. The unique oxygen vacancies can act as active sites to activate small molecules such as H2, CO2, and CH4. By optimizing the number of oxygen vacancies, the active sites can be optimized, thereby improving performance. However, the morphology of most In2O3 is difficult to control, which hinders the direct use of existing In2O3. The preparation process of regular In2O3 is cumbersome, or requires the addition of oleylamine, leading to complex post-processing of samples and residual impurities, making it difficult to establish a structure-activity relationship between the catalytic activity and structure of In2O3. To address this, our research team optimized the preparation process of In2O3, preparing a porous cubic In2O3 catalyst (PC-In2O3). By adjusting the reaction environment and controlling the calcination temperature, the oxygen vacancies of In2O3 can be regulated, thereby solving the activation problems of carbon dioxide and hydrogen and realizing the application of a bifunctional catalyst.

[0009] Based on the above inventive concept, and to achieve the above objectives, the technical solution provided by this invention is as follows:

[0010] A simple method for preparing porous indium oxide, characterized by the following steps:

[0011] 1) In a strong alkaline solution, add dropwise a solution prepared from In(NO3)3·5H2O (MACKLIN 99.99% metals basis) and ultrapure water (other solutions containing In can also be added). 3+ The present invention uses In(NO3)3·5H2O as a solution because of its good solubility and the fact that NO3... - (Ions do not affect the product and are easily removed by washing). An In(OH)3 precursor with a regular cubic morphology was prepared by a hydrothermal method. -The molar concentration in the reaction solution is 6M to 9M; in this invention, In is first precipitated by adding a strong base with a concentration of 6M to 9M. 3+ It is easy to form a uniform morphology, and through hydrothermal reaction, the crystallinity is improved and the growth of some crystal faces is inhibited, so as to prepare an In(OH)3 precursor with a uniform morphology.

[0012] 2) The In(OH)3 precursor obtained in step 1) was placed in an air atmosphere and calcined at 250℃~350℃ for 2~4 hours (after 2 hours of calcination, the morphology of the product tends to be stable). After natural cooling, a porous cubic structure indium oxide PC-In2O3 with uniform morphology was obtained (PC represents porous cubic structure).

[0013] Furthermore, in step 1), NaOH is chosen as the strong base, but other strong bases, such as KOH, can also be used. The specific steps are as follows:

[0014] NaOH was slowly added to a polytetrafluoroethylene liner containing ultrapure water and stirred. After the NaOH solution cooled, a solution prepared from In(NO3)3·5H2O and ultrapure water was slowly added dropwise. After the addition was complete, the mixture was stirred at room temperature and placed in a reaction vessel. The reaction was carried out at 100℃~120℃ for 12~24h. After the reaction was completed, the mixture was washed several times with water and alcohol alternately, and then dried at 60℃~80℃ for 8~12h to obtain the In(OH)3 precursor.

[0015] Furthermore, in step 1), the concentration of NaOH (Alfa Aesar 98%) in the reaction solution is 6M, at which a precursor with stable and uniform morphology can be obtained.

[0016] Further, in step 2), the In(OH)3 precursor obtained in step 1) is placed in a muffle furnace and calcined at 250°C for 2 hours in air at a heating rate of 5°C / min, followed by natural cooling to obtain porous cubic indium oxide. During the research process, the team discovered that the transformation temperature of In(OH)3 is around 200°C, and temperature affects the structure and morphology of the pores. 250°C is the temperature that best preserves the morphology; therefore, in step 2), 250°C is preferred as the calcination temperature. Based on the calcination temperature, the obtained porous cubic indium oxide can be named In2O3-250. Similarly, the product obtained by calcination at 350°C is named In2O3-350. The product can also be named In2O3-X based on the calcination temperature, where X represents different calcination temperatures.

[0017] This invention also provides porous cubic indium oxide prepared by the above preparation method, and its application as a catalyst in the stepwise activation of carbon dioxide and hydrogen to prepare methanol (a two-step process of preparing dimethyl carbonate from carbon dioxide and methanol, and preparing methanol from dimethyl carbonate and hydrogen). It can be seen that the catalyst prepared by this invention can be applied to two reactions in the preparation process at the same time, realizing the value of "one to many".

[0018] Based on the above applications, the present invention further provides a method for preparing dimethyl carbonate from carbon dioxide and methanol, characterized in that the operation is as follows:

[0019] The porous cubic indium oxide prepared by the above method was uniformly dispersed in anhydrous methanol, and then transferred to a high-pressure reactor and charged with CO2 at a pressure of not less than 1 MPa for reaction. The reaction temperature was 70℃~100℃. After the reaction was completed, dimethyl carbonate was obtained.

[0020] Furthermore, the method for preparing methanol from dimethyl carbonate and hydrogen is unique in that the operation is as follows:

[0021] The porous cubic indium oxide prepared by the above method was uniformly dispersed in a dimethyl carbonate solution, and then transferred to a high-pressure reactor and charged with H2 at a pressure of not less than 2 MPa for reaction. The reaction temperature was 70℃~100℃. After the reaction was completed, methanol was obtained.

[0022] The principle of this invention:

[0023] This invention first prepares a uniform cubic In(OH)3 precursor using a simple one-step hydrothermal method under a strongly alkaline environment, controlling the reaction temperature and time. Then, it undergoes calcination oxidation in air to convert In(OH)3 into a stable porous cubic In2O3 structure. To obtain a regular cubic structure, this invention chooses a strong alkaline solution such as sodium hydroxide, which is more conducive to the preparation of well-crystallized indium hydroxide; this condition is essential for the preparation of a regular cubic structure. Furthermore, different calcination temperatures affect the degree of conversion of In(OH)3 to In2O3, the number of surface oxygen vacancies, and the retention of the microstructure. This invention achieves the preparation of a bifunctional catalyst by controlling the molar concentration of the strong base in the reaction solution (6M–9M) and the calcination temperature (250℃–350℃). Transmission electron microscopy and nitrogen adsorption-desorption tests show that calcination at 250℃ maintains the best effect, preserving the uniform cubic structure and maximizing the specific surface area. Performance tests revealed that the In2O3-250 catalyst exhibited good catalytic activity in both reactions involving the stepwise activation of carbon dioxide and hydrogen to produce methanol.

[0024] The advantages of this invention are:

[0025] 1. This invention provides a simple method for synthesizing a porous cubic In₂O₃ catalyst and its application in the stepwise activation and conversion of CO₂ and H₂ to methanol. The In₂O₃ prepared by this method is very simple, requiring no additional substances or post-treatment. It has a regular cubic structure with a porous structure, and can be simultaneously applied in the reactions of carbon dioxide and methanol to produce dimethyl carbonate and dimethyl carbonate and hydrogen to produce methanol. This solves the problem that a single catalyst cannot simultaneously activate two types of molecules. Moreover, the catalyst prepared by this invention does not require the introduction of other metals and exhibits high activity at low temperatures and high methanol yield.

[0026] 2. The process flow of this invention is simple, and it controls the OH... - By adjusting the molar concentration in the reaction solution, a precursor In(OH)3 with a regular morphology was prepared. Simultaneously, by controlling the calcination temperature, an In₂O₃ catalyst with a high number of oxygen vacancies was prepared, which remained intact and undeactivated during the reaction. In particular, at a calcination temperature of 250℃, a uniformly sized porous cubic catalyst In₂O₃-250 was formed, which can be simultaneously applied to two reaction systems: the production of dimethyl carbonate from carbon dioxide and methanol, and the production of methanol from dimethyl carbonate and hydrogen. Both systems exhibited good catalytic performance, realizing the "one-to-many" catalyst design concept, improving catalyst utilization efficiency, and saving raw materials.

[0027] 3. Without loading other metals, the In2O3-catalyst prepared by this invention achieves stepwise activation and conversion of CO2 and H2 at low temperature, converting CO2 into value-added chemicals and realizing the effect of "turning waste into treasure". Attached Figure Description

[0028] Figure 1 The preparation process and morphological characterization of In2O3-250 are shown in the following figures: a) Flowchart of the experimental preparation; b) Transmission electron microscopy (TEM) image; cd) High-resolution TEM image; ef) Interplanar spacing diagram; g) High-angle annular dark field and corresponding elemental distribution diagram.

[0029] Figure 2 Morphological characterization of the In2O3-350 catalyst: a) Transmission electron microscopy (TEM) image; bc) High-resolution TEM image; df) High-angle annular dark field and corresponding elemental distribution diagram.

[0030] Figure 3 Morphological characterization of the In2O3-450 catalyst: a) Transmission electron microscopy (TEM) image; bc) High-resolution TEM image; df) High-angle annular dark field and corresponding elemental distribution diagram.

[0031] Figure 4 Structural characterization of different catalysts; a) Different catalysts O1s a) XPS spectrum; b) nitrogen adsorption-desorption curve; c) electron paramagnetic resonance spectrum;

[0032] Figure 5 The diagram shows the catalytic performance of different catalysts; a) Diagram of dimethyl carbonate production from carbon dioxide and methanol; b) Diagram of methanol production from dimethyl carbonate and hydrogen; c) Diagram of cycle performance.

[0033] Figure 6 Morphological characterization of the In2O3-1∶9 catalyst: a) Transmission electron microscopy (TEM) image; b) High-resolution transmission electron microscopy (HRTEM) image.

[0034] Figure 7 Morphological characterization of the In2O3-1∶3 catalyst: a) Transmission electron microscopy (TEM) image; b) High-resolution transmission electron microscopy (HRTEM) image.

[0035] Figure 8 The morphology of the In2O3-NH4OH catalyst is shown in the images: a) Transmission electron microscopy (TEM) image; b) High-resolution transmission electron microscopy (HRTEM) image.

[0036] Figure 9 Morphological characterization of the In2O3-Unheated catalyst: a) Transmission electron microscopy (TEM) image; b) High-resolution transmission electron microscopy (HRTEM) image.

[0037] Figure 10 The morphology of the NP-In2O3 catalyst is shown in the following diagrams: a) Transmission electron microscopy (TEM) image; b) High-resolution TEM image; c) Interplanar spacing diagram; df) High-angle annular dark field and corresponding elemental distribution diagram. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0039] This invention discloses a method for preparing a bifunctional catalyst In2O3 for the production of dimethyl carbonate from carbon dioxide and methanol and the production of methanol from dimethyl carbonate and hydrogen. The technical solution of this invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments.

[0040] Example 1

[0041] like Figure 1 As shown in a, a method for preparing porous cubic indium oxide includes the following steps:

[0042] (1) Preparation of In(OH)3 precursor

[0043] First, add 70 mL of ultrapure water to a 100 mL polytetrafluoroethylene inner liner and place a magnetic stirrer inside. Then, slowly add 19.2 g of sodium hydroxide to the 70 mL of ultrapure water and stir for 30 minutes. After the NaOH solution cools, slowly add the prepared solution containing In.3+ The solution (prepared by ultrasonically dispersing 1.203 g In(NO3)3·5H2O in 10 mL of ultrapure water) was used. During the dropwise addition, the solution gradually turned milky white. After the addition was complete, the mixture was stirred at room temperature for 30 minutes, then transferred to a reaction vessel and reacted at 100°C for 24 hours in a forced-air drying oven. After the reaction was completed, the mixture was washed three times alternately with water and alcohol, and then dried at 60°C for 8 hours in a forced-air drying oven to obtain the In(OH)3 precursor. In this example, the molar concentration of sodium hydroxide in the reaction solution was controlled at 6 M.

[0044] (2) Preparation of different In2O3-based catalysts

[0045] The precursor In(OH)3 obtained in step 1) was placed in a muffle furnace and calcined at 250°C for 2 hours in air atmosphere at a heating rate of 5°C / min. After natural cooling, the sample was obtained and named In2O3-250.

[0046] Example 2

[0047] The difference from Example 1 is that in step 2) of this example, calcination at 300°C for 2 hours is used to obtain sample In2O3-300.

[0048] Example 3

[0049] The difference from Example 1 is that in step 2) of this example, calcination at 350°C for 2 hours is used to obtain sample In2O3-350.

[0050] Example 4

[0051] The difference from Example 1 is that the amount of sodium hydroxide added in this example is increased, and the molar concentration of sodium hydroxide in the reaction solution is controlled at 9M to obtain sample In2O3-1∶9.

[0052] Comparative Example 1

[0053] The difference from Example 1 is that in step 2) of this example, calcination at 450°C for 2 hours is used to obtain sample In2O3-450.

[0054] Comparative Example 2

[0055] The difference from Example 1 is that the amount of sodium hydroxide added is reduced in this example, and the molar concentration of sodium hydroxide in the reaction solution is controlled at 3M to obtain sample In2O3-1∶3.

[0056] Comparative Example 3

[0057] The difference from Example 1 is that in step 1) of this example, sodium hydroxide is replaced with ammonia water, and the mass of ammonia water is 0.48g, resulting in sample In2O3-NH4OH.

[0058] Comparative Example 4

[0059] The difference from Example 1 is that in step 1) of this example, the hydrothermal method was not used to prepare the In(OH)3 precursor; only the prepared In-containing precursor was used. 3+ The solution was slowly added dropwise to a sodium hydroxide solution, stirred, and allowed to stand to generate the In(OH)3 precursor. The resulting sample was In2O3-Unheated.

[0060] Comparative Example 5

[0061] In this embodiment, an NP-In2O3 catalyst was prepared by the following method:

[0062] Weigh 1g In(NO3)3·5H2O and place it in a 50mL dry pot. Transfer the dry pot to a muffle furnace, set the heating rate to 5℃ / min, and calcine at 250℃ for 2 hours. After the reaction is complete, allow it to cool naturally to room temperature to obtain NP-In2O3.

[0063] Comparative Example 6

[0064] The Cu / ZnO / Al2O3 catalyst was prepared in this embodiment using the following method:

[0065] ① Prepare aqueous solutions of water-soluble salts of copper and zinc separately and mix them to obtain a copper-zinc mixed solution;

[0066] ② Mix water-soluble carbonates and bicarbonates and prepare an aqueous solution to obtain a dual-precipitant buffer solution;

[0067] ③ Add the copper-zinc mixed solution to the dual precipitant buffer solution at 70-80℃ with stirring until the pH value is 7.0-7.5. Then raise the temperature to 75-85℃ and stir for aging for 1-1.5h. During the aging process, continue to add copper-zinc mixed solution to keep the pH value at 7.0-7.5 to obtain copper-zinc suspension.

[0068] ④ Prepare aqueous solutions of water-soluble salts of aluminum, transition metals, and rare earth elements respectively, and mix them to obtain a carrier solution;

[0069] ⑤ Add ammonia water to the carrier solution at 65-80℃ with stirring and maintain the pH value at 7.0-7.5, then stir for 1-1.5h to obtain the carrier suspension;

[0070] ⑥ The carrier suspension is added to the copper-zinc suspension at 60-70°C under stirring and stirred for 20-40 minutes. After washing, filtering, drying, calcining and molding, a copper-based methanol synthesis catalyst is obtained.

[0071] To verify the catalytic performance of the porous indium oxide catalyst of the present invention, the following experimental examples were also conducted:

[0072] I. Morphological and structural characterization of indium oxide obtained under different conditions in Examples 1, 3, 4, and Comparative Examples 1-5:

[0073] Figure 1 The morphology and elemental distribution of the In2O3-250 catalyst are shown in the following diagram: Figure 1 Figure b shows that under a calcination temperature of 250℃, In₂O₃ forms uniformly sized blocky cubes; from Figure 1 As can be clearly seen from point c, the cube has a porous structure; Figure 1 The d-plane shows a spacing of 0.293 nm, which belongs to the (222) plane of In2O3; Figure 1 The ef is a crystal plane spacing intensity distribution diagram, which can accurately and scientifically show the crystal plane spacing; Figure 1 The g indicates that In (green) and O (yellow) elements are evenly distributed throughout the material.

[0074] Figure 2 The morphology and elemental distribution spectrum of the In2O3-350 catalyst are shown below: Figure 2 As shown in Figure a, the In2O3-350 catalyst has a porous cubic structure, and compared with In2O3-250, the bulk material shows accumulation at higher temperatures; for example... Figure 2 b shows that the edges of the blocky body overlap, and the morphology begins to change. Figure 2 The c-shaped structure shows a crystal plane spacing of 0.296 nm, which is consistent with the In2O3-250 catalyst and belongs to the (222) crystal plane of In2O3; Figure 2 The df data shows that In (green) and O (yellow) elements are evenly distributed throughout the material.

[0075] Figure 3 The morphology and elemental distribution spectrum of the In2O3-450 catalyst are shown below: Figure 3 As shown in Figure a, the In2O3-450 catalyst exhibits an irregular blocky structure. Compared to In2O3-250, the morphology of the catalyst changes significantly when the calcination temperature is increased to 450℃; for example... Figure 3 As shown in b, the porous structure is still maintained, but the number of pores is significantly reduced compared to In2O3-250 and In2O3-350; Figure 3 The c-shaped structure shows a crystal plane spacing of 0.296 nm, which is consistent with the In2O3-250 catalyst and belongs to the (222) crystal plane of In2O3; Figure 3 The df data shows that In (green) and O (yellow) elements are evenly distributed throughout the material.

[0076] Figure 6 Morphological characterization of the In2O3-1∶9 catalyst: (See figure) Figure 6 As shown in a, the In2O3-1∶9 catalyst, like the In2O3-250 catalyst in Example 1, is a uniformly sized blocky cube. Figure 6 As can be clearly seen from b, the cubic block has a porous structure, and undoubtedly, it has the same catalytic performance as the In2O3-250 catalyst in Example 1.

[0077] Figure 7 Morphological characterization of the In2O3-1∶3 catalyst: From Figure 7 As shown in Figure a, the In₂O₃⁻ 1:3 catalyst exhibits a random, blocky structure. Compared to In₂O₃⁻ 250, controlling the molar concentration of sodium hydroxide in the reaction solution to 3 M significantly alters the catalyst morphology, demonstrating the crucial importance of the molar concentration of hydroxide ions in the reaction solution. Figure 7 As shown in b, it retains a partially porous structure, but the number of pores is significantly reduced compared to In2O3-250, In2O3-350, and In2O3-1∶9.

[0078] Figure 8 Morphological characterization of the In2O3-NH4OH catalyst: From Figure 8 As shown in a, the In₂O₃-NH₄OH catalyst exhibits an irregular blocky structure, indicating that uniformly sized blocky cubes cannot be prepared in a weak base environment; for example... Figure 8 As shown in b, the structure retains many pores, but the number of pores is significantly reduced compared to the sample prepared under strong alkaline conditions.

[0079] Figure 9 Morphological characterization of the In2O3-Unheated catalyst: From Figure 9 As shown in a, the In2O3-Unheated catalyst is mostly an irregular blocky structure, indicating that the hydrothermal preparation process in step 1) is also a prerequisite for obtaining a uniformly sized blocky cubic structure; such as Figure 9 b shows that it maintains a porous structure, with a significantly reduced number of pores compared to the sample prepared under strong alkaline conditions.

[0080] Figure 10 The morphology characterization diagram of the NP-In2O3 catalyst is shown below; Figure 10 Figures a and b show that the NP-In2O3 catalyst has a random bulk structure and no pores; Figure 10 c shows that its interplanar spacing is 0.293 nm, which belongs to the (222) crystal plane of In2O3; Figure 10 The df data shows that In (green) and O (yellow) elements are evenly distributed throughout the material.

[0081] 2. Structural characterization of porous indium oxide obtained at different calcination temperatures and the catalyst NP-In2O3 prepared in Comparative Example 3.

[0082] Figure 4 For structural characterization and oxygen vacancy characterization: such as Figure 4 The result of a shows that, through the analysis of each catalyst O 1s Orbit fitting revealed that the In2O3-250 catalyst has 36.45% oxygen vacancies, significantly higher than other catalysts; for example... Figure 4 Figure b shows that the In2O3-250 catalyst has a large specific surface area of ​​56.11 g / m². 2 It also has a rich mesoporous structure; Figure 4 The c-value represents the oxygen vacancy further measured by electron paramagnetic resonance, which is consistent with the XPS results, indicating that the In2O3-250 catalyst has a high oxygen vacancy rate.

[0083] 3. The catalytic performance of porous indium oxide obtained at different calcination temperatures, as well as the NP-In₂O₃ catalyst prepared in Comparative Example 3 and the Cu / ZnO / Al₂O₃ catalyst prepared in Comparative Example 6, was tested.

[0084] The specific operations of the aforementioned methods for producing dimethyl carbonate from carbon dioxide and methanol, and for producing methanol from dimethyl carbonate and hydrogen, are as follows:

[0085] A porous cubic In₂O₃ catalyst was ultrasonically dispersed in anhydrous methanol (mass-volume ratio 2:1). The dispersed solution was then transferred to an inflatable pressure reactor (IKA), rinsed three times with CO₂, and reacted at a pressure of 1 MPa for 1 hour at 100°C. After the reaction, the container was immediately immersed in an ice-water bath. Once the temperature dropped below 20°C, the gas was collected using a gas collection bag, and its components were analyzed by gas chromatography. The liquid in the container was centrifuged to obtain the reacted catalyst and the mixed solution. A small amount of the solution was added to a glass bottle, and the liquid phase product was analyzed by chromatography. The space-time yield was calculated based on a standard curve.

[0086] The porous cubic In₂O₃ catalyst was ultrasonically dispersed in dimethyl carbonate (mass-volume ratio 2:1). The dispersed solution was then transferred to an inflatable pressure reactor (IKA), rinsed three times with H₂, and reacted at a pressure of 2 MPa for 2 h at a temperature of 100 °C. After the reaction, the product was analyzed in the same manner as in the dimethyl carbonate preparation system using carbon dioxide and methanol.

[0087] Figure 5The graph shows the catalyst performance test results. Under the same conditions, the In2O3-250 catalyst exhibits superior performance in activating both carbon dioxide and hydrogen, achieving the goal of converting carbon dioxide to methanol at low temperatures. Furthermore, the catalyst maintains good catalytic activity after six cycles, making it suitable for industrial applications.

[0088] In summary, the catalyst prepared by this invention can not only effectively solve the problem of complex preparation process of existing catalysts, but also solve the current problem of difficulty in achieving both high selectivity and high activity.

[0089] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. The application of a porous indium oxide with a cubic structure in the stepwise activation of carbon dioxide and hydrogen to prepare methanol, characterized in that: The stepwise activation refers to the use of porous indium oxide with a cubic structure as a catalyst to prepare dimethyl carbonate from carbon dioxide and methanol, and the use of porous indium oxide with a cubic structure as a catalyst to hydrogenate dimethyl carbonate to methanol; wherein, the preparation method of porous indium oxide with a cubic structure includes the following steps: 1) In a strong alkaline solution, a solution prepared by In(NO3)3·5H2O and ultrapure water is added dropwise to prepare the In(OH)3 precursor by hydrothermal method; OH - The molar concentration in the reaction solution is 6 M ~ 9 M; 2) Place the In(OH)3 precursor obtained in step 1) in an air atmosphere at 250°C. o Calcination at 350 °C for 2 to 4 hours yields porous indium oxide with a cubic structure.

2. The application according to claim 1, characterized in that, Step 1) Specifically: NaOH was slowly added to a polytetrafluoroethylene liner containing ultrapure water, and the mixture was stirred. After the NaOH solution cooled, a solution prepared from In(NO3)3·5H2O and ultrapure water was slowly added dropwise. After the addition was complete, the mixture was stirred at room temperature and placed in a reaction vessel at 100°C. o C~ 120 o The reaction was carried out at C for 12-24 hours. After the reaction was completed, the mixture was washed several times with water and alcohol alternately, and then subjected to a reaction at 60°C. o C ~ 80 o Drying at C for 8 to 12 hours yields the In(OH)3 precursor.

3. The application according to claim 2, characterized in that: In step 1), the concentration of NaOH in the reaction solution is 6M.

4. The application according to claim 3, characterized in that: In step 2), the In(OH)3 precursor obtained in step 1) is placed in a muffle furnace and heated in an air atmosphere at 5°C. o Calcination at 250 °C for 2 hours with a heating rate of C / min followed by natural cooling yielded porous indium oxide with a cubic structure.

5. A method for preparing dimethyl carbonate from carbon dioxide and methanol, characterized in that, The operation is as follows: The porous indium oxide with a cubic structure as described in any one of claims 1-4 is uniformly dispersed in anhydrous methanol, then transferred to a high-pressure reactor and charged with CO2 at a pressure of not less than 1 MPa for reaction at a reaction temperature of 70°C. o C ~ 100 o C, after the reaction is complete, dimethyl carbonate is obtained.

6. A method for preparing methanol from dimethyl carbonate and hydrogen, characterized in that, The operation is as follows: The porous indium oxide with a cubic structure as described in any one of claims 1-4 is uniformly dispersed in a dimethyl carbonate solution, and then transferred to a high-pressure reactor and charged with H2 at a pressure of not less than 2 MPa for reaction at a reaction temperature of 70°C. o C ~100 o C, after the reaction is complete, methanol is obtained.

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