Catalyst for synthesizing methanol as well as preparation method and application of catalyst

Abstract

The invention belongs to the technical field of catalyst preparation, and particularly relates to hexagonal-phase indium oxide rich in oxygen vacancies, a preparation method and a method for preparing methanol through low-temperature efficient catalysis of carbon dioxide hydrogenation. The preparation method of the hexagonal-phase indium oxide comprises the following steps: mixing indium precursor salt, a precipitator and a solvent to obtain a reaction solution, and crystallizing the reaction solution to obtain a hexagonal-phase indium oxide precursor; roasting the obtained hexagonal indium oxide precursor to obtain hexagonal phase indium oxide; wherein the precipitator is at least one of sodium hydroxide, ammonia water and urea; the solvent is acetone or a mixed solution of acetone and ethanol. The preparation method disclosed by the invention is simple, controllable and good in reproducibility; as a catalyst for preparing methanol through CO2 hydrogenation, the catalyst has the advantages of high reaction stability, excessive reduction resistance, high target product yield, low temperature, high efficiency and the like in a reaction for preparing methanol through CO2 hydrogenation.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and relates to a catalyst for synthesizing methanol, a preparation method and application thereof, and in particular to a hexagonal indium oxide rich in oxygen vacancies, a preparation method thereof, and a method for preparing methanol by catalytic hydrogenation of carbon dioxide at low temperature and high efficiency. Background Art

[0002] The production and application of methanol plays an extremely important role in the chemical industry. Methanol has multiple identities. It can be regarded as a clean energy source and an important bulk chemical raw material in the chemical industry. Methanol is widely used in the traditional chemical industry to synthesize basic chemicals such as formaldehyde, methyl tert-butyl ether (MTBE), acetic acid, methylamine, dimethyl ether, etc. Further processing converts methanol into various daily chemical products such as resins, paints, adhesives, silicones, plastics and protective materials. In addition, methanol, as a raw material for the industrial production of olefins, plays a key role in the MTO (Methanol to Olefins) reaction. On the other hand, CO 2 As one of the main greenhouse gases, its hydrogenation resource utilization is not only an important way to achieve the goal of carbon neutrality, but also an effective path that the industry has high hopes for. It can be used to synthesize high value-added products.

[0003] Catalysts for the hydrogenation of carbon dioxide to methanol mainly include Cu-based catalysts, precious metal catalysts (such as Pt and Pd), metal oxide catalysts, etc. Among them, Cu-based catalysts are widely used due to their high activity and low price, but they have low selectivity and copper is easily sintered and deactivated by water vapor produced by the side reaction of reverse water gas conversion. Although precious metal catalysts are highly active, they are expensive. Recently, a large number of studies have shown that metal oxide catalysts can efficiently catalyze CO 2 Hydrogenation to methanol reaction, where In 2 O 3 It has attracted much attention due to its selectivity exceeding 90%. 2 O 3 There are two main crystal phases, cubic phase and hexagonal phase. The stable crystal phase cubic c-In is easy to prepare and synthesize. 2 O 3 In comparison, the metastable hexagonal phase h-In 2 O 3 Catalytic CO 2The activity of hydrogenation is higher. For example: CN 110479235A provides a method for preparing hexagonal indium oxide with a nano-multilevel structure, wherein a metal indium salt and a precipitant are dissolved in two solvents respectively, wherein the metal indium salt includes one or both of indium nitrate and indium chloride, and the solvents are a mixed solution of deionized water and ethanol, and then the precipitant is added dropwise to the metal indium salt solution for hydrothermal crystallization; CN 105668612 A discloses a method for preparing hexagonal tubular indium oxide, wherein indium oxide is prepared using an indium (III)-terephthalic acid complex as a precursor and its morphology and size are controlled; CN 109205659A uses fluid cross-flow shearing in a microreactor to achieve rapid mixing of an indium chloride solution and a sodium hydroxide solution, and simultaneously passes a subsequent coil for high-temperature reaction to achieve rapid growth of particles in an indium oxide precursor suspension; CN 116216768 A uses indium salt, urea, weak acid and strong base salt and deionized water for hydrothermal crystallization, and then anneals in air atmosphere to achieve the goal of adjustable indium oxide crystal form and adjustable phase composition; CN 116037094A discloses the preparation of a magnesium-aluminum doped indium oxide catalyst and its application in the preparation of methanol by hydrogenation of carbon dioxide, wherein the active component is hexagonal indium oxide; CN 101117236A uses trace transition metal ions (Fe, Co, Ni, Cu, Cr, Mn) as dopants, and obtains indium oxide with controllable cubic and hexagonal crystal forms by a simple precipitation method. It can be seen from the above prior art that h-In 2 O 3 The preparation conditions are very harsh, the steps are complicated, and cubic indium oxide (c-In 2 O 3 ) or other mixed phases, and hexagonal phase h-In 2 O 3 The reproducibility is very poor, making the obtained indium oxide catalyst unstable and easy to deactivate. As mentioned in Z.Krist.Cryst.Mater., 2017, 232, 129-140 and Nanoscale, 2021, 13, 4038-4050, when hexagonal indium oxide is hydrothermally synthesized with an alcohol-water mixture, the ratio is very harsh and impurities are very likely to appear. In addition, since the hydrogenation catalytic reaction is carried out in the presence of hydrogen, the prior art is also prone to excessive reduction of indium oxide and deactivation.

[0004] Moreover, CO 2 The hydrogenation reaction to produce methanol is an exothermic reaction and is suitable for low temperature reactions. 2 Due to the kinetics of activation, a higher reaction temperature is required, but side reactions are serious at high temperatures. Therefore, the key to solving this problem is to develop and design effective catalysts with low temperature and stable performance.

[0005] Therefore, how to provide a simple synthesis method with good reproducibility, stable catalytic performance, and suitable for low-temperature catalytic CO2 Indium oxide catalyst for hydrogenation to methanol is a technical problem that needs to be solved at present. Summary of the invention

[0006] In view of the above technical problems, the present invention provides a catalyst for synthesizing methanol, a preparation method and application thereof, and particularly relates to a hexagonal indium oxide rich in oxygen vacancies and a preparation method thereof, and a method and application thereof for catalyzing the hydrogenation of carbon dioxide to produce methanol at low temperature and high efficiency. The hexagonal indium oxide of the present invention is a pure hexagonal indium oxide rich in oxygen vacancies, which has the advantages of high efficiency in activating CO at low temperature. 2 The technical advantages of the present invention are not only that, but also that the preparation method of the present invention is simple, controllable and has good reproducibility; as CO 2 The hydrogenation catalyst for methanol production exhibits the advantages of high reaction stability, resistance to over-reduction, high yield of target products, low temperature and high efficiency in the reaction of carbon dioxide hydrogenation for methanol production.

[0007] The first aspect of the present invention is to provide a method for preparing hexagonal indium oxide, comprising mixing an indium precursor salt, a precipitant and a solvent to obtain a reaction solution, crystallizing the reaction solution to obtain a hexagonal indium oxide precursor; calcining the obtained hexagonal indium oxide precursor to obtain hexagonal indium oxide;

[0008] Wherein, the precipitant is at least one of sodium hydroxide, ammonia water and urea;

[0009] The solvent is acetone, or a mixture of acetone and ethanol.

[0010] According to the present invention, the indium precursor salt can be selected from a wide range. In a preferred embodiment of the present invention, the indium precursor salt is selected from at least one of indium nitrate, indium acetylacetonate, and indium chloride.

[0011] According to the present invention, the molar ratio of the precipitant to the indium precursor salt can be selected within a wide range. In a preferred embodiment of the present invention, the molar ratio of the precipitant to the indium precursor salt is (1.2-2):1.

[0012] According to the present invention, the amount of the solvent can be selected within a wide range. In a preferred embodiment of the present invention, the amount of the solvent is 1250-5000 mL per 1 mol of indium precursor salt.

[0013] According to the present invention, the solvent is acetone, or a mixture of acetone and ethanol. Preferably, when the solvent is a mixture of acetone and ethanol, the volume percentage of acetone is ≥60%.

[0014] In a preferred embodiment of the present invention, the solvent is acetone or a mixture of acetone and ethanol with a volume percentage of acetone ≥ 60%.

[0015] According to the present invention, the crystallization conditions can be selected within a wide range. In a preferred embodiment of the present invention, the crystallization conditions include: a temperature of 90-180° C.; and / or a time of 5-20 h.

[0016] According to the present invention, the roasting conditions can be selected within a wide range. In a preferred embodiment of the present invention, the roasting conditions include: a roasting temperature of 300-800°C, and / or a roasting time of 1-5h; preferably, the temperature is increased to the roasting temperature at a heating rate of 1-3°C / min.

[0017] In a preferred embodiment of the present invention, the preparation method further comprises the steps of separation, optional washing, and optional drying after crystallization. The conditions for the above separation, washing, and drying are conventional conditions in the art and will not be described in detail here.

[0018] In a preferred embodiment of the present invention, the hexagonal indium oxide is pure phase hexagonal indium oxide.

[0019] In a preferred embodiment of the present invention, the grain size of the hexagonal indium oxide is 10-20 nm.

[0020] Preferably, the XPS method is used to detect the binding energy of O1s, and the total amount of all oxygen species on the surface is 100%, and the proportion of oxygen vacancies in the hexagonal indium oxide in all oxygen species on the surface is above 30%, that is, the pure-phase hexagonal indium oxide of the present invention is oxygen-rich pure-phase hexagonal indium oxide.

[0021] The second aspect of the present invention is to provide a hexagonal indium oxide, which is a pure phase hexagonal indium oxide; the binding energy of O1s is detected by the XPS method, and the total amount of all oxygen species on the surface is 100%, and the proportion of oxygen vacancies in the hexagonal indium oxide in all oxygen species on the surface is above 30%; and / or, the hexagonal indium oxide is prepared by the preparation method described in the first aspect.

[0022] Preferably, the grain size of the hexagonal indium oxide is 10-20 nm.

[0023] The third aspect of the present invention is to provide a use of the hexagonal indium oxide prepared by the preparation method described in the first aspect or the hexagonal indium oxide described in the second aspect as a hydrogenation catalyst preferably in the production of methanol. For example, this catalyst can be used in the reaction of hydrogenating carbon dioxide to produce methanol, and can also be used as a catalyst for hydrogenating carbon monoxide / carbon dioxide to produce olefins.

[0024] The fourth aspect of the present invention is to provide a method for producing methanol, wherein carbon dioxide and hydrogen are contacted with a catalyst to react to produce methanol; wherein the catalyst is the hexagonal indium oxide produced by the preparation method described in the first aspect or the hexagonal indium oxide described in the second aspect.

[0025] According to the present invention, the conditions of the contact reaction can be selected in a wide range. In a preferred embodiment of the present invention, the conditions of the contact reaction include: a temperature of 150-250°C, and / or a pressure of 2-5 MPa; and / or a space velocity of 24000-96000 ml·h -1 ·g -1 and / or,

[0026] The contact reaction is carried out in a fixed bed reactor.

[0027] In a preferred embodiment of the present invention, the temperature is first raised to the temperature of the contact reaction, and then carbon dioxide and hydrogen are introduced to contact the catalyst; more preferably,

[0028] The atmosphere during the heating process is at least one of hydrogen, argon and nitrogen; more preferably, it is one of hydrogen, argon, a mixture of hydrogen and argon, and nitrogen.

[0029] The catalyst in the above technical solution is heated to 150°C-250°C in a hydrogen atmosphere and subjected to CO 2 In the hydrogenation to methanol reaction, the catalyst can operate stably for 150 hours, and the catalyst obtained after the reaction has no obvious deactivation and over-reduction.

[0030] The catalyst mentioned in the present invention can be a low-temperature and high-efficiency catalyst CO 2 The hydrogenation reaction to produce methanol seriously inhibits the occurrence of the reverse water gas side reaction.

[0031] In summary, the catalyst preparation step of the present invention is simple, and it can catalyze CO 2 The hydrogenation to methanol was stably operated for 150 hours, and the catalyst was stable after the reaction without over-reduction. The problem of indium oxide being easily over-reduced in the reaction was solved, and the catalyst could perform catalytic reaction at a relatively low temperature of 150-250°C. The present invention provides a catalyst for methanol production and a preparation method thereof, which can be applied to industrial preparation of hexagonal indium oxide and methanol production technology.

[0032] In summary, the advantages of the present invention are:

[0033] The present invention relates to a simple preparation method of hexagonal indium oxide and its application as a catalyst in the hydrogenation of carbon dioxide to methanol, which solves the problems of complicated preparation method, easy occurrence of impurities and poor reproducibility in the preparation of hexagonal indium oxide in the prior art. 2 O 3 . The oxide is characterized by XRD, and all hexagonal indium oxides of different sizes are pure phases, and can stably catalyze the hydrogenation of carbon dioxide to produce methanol for a long period of time, and there is no obvious deactivation during the reaction. The catalyst provided by the present invention and its preparation method can meet the requirements of obtaining pure hexagonal indium oxide with a simple preparation method, and have good reproducibility, and show high reaction stability, resistance to over-reduction, and high yield of the target product in the reaction of hydrogenation of carbon dioxide to produce methanol. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1-1 The pure phase h-In of the methanol catalyst in Example 1 of the present invention 2 O 3 XRD pattern of

[0035] Figure 1-2 The pure phase h-In of the methanol catalyst in Example 1 of the present invention 2 O 3 O1s spectrum;

[0036] Figure 2 is h-In in Example 1 of the present invention 2 O 3 In CO 2 Stability evaluation in hydrogenation to methanol;

[0037] Figure 3-1 h-In in Example 1 of the present invention 2 O 3 XRD diffraction pattern after 150h reaction;

[0038] Figure 3-2 h-In in Example 1 of the present invention 2 O 3 In3d spectrum after 150h reaction;

[0039] Figure 4 The methanol catalyst In in Comparative Example 1 of the present invention 2 O 3 XRD pattern of

[0040] Figure 5 The methanol catalyst In in Comparative Example 2 of the present invention 2 O 3 XRD pattern of

[0041] Figure 6The methanol catalyst In of Comparative Example 4 (1) of the present invention is 2 O 3 XRD pattern of . DETAILED DESCRIPTION

[0042] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0043] The raw materials involved in the following examples and comparative examples are all commercially available.

[0044] In the following examples and comparative examples, gas chromatography was used to analyze the products online. TCD detector was used to analyze CH 4 , Ar, CO and CO 2 , where Ar is the internal standard gas. FID is used to detect CH 4 and CH 3 OH.

[0045] CO 2 The conversion rate is calculated as:

[0046] The methanol selectivity is calculated as:

[0047] The calculation method of space-time yield is:

[0048] Example 1

[0049] Preparation of catalyst: Weigh 4.5124g of indium nitrate and 2.16g of sodium hydroxide as precipitant, dissolve in 50ml of acetone and stir for 3h, then add water and heat in autoclave for crystallization, keep at 150℃ for 10h. After cooling to room temperature, centrifuge, wash with the same solvent until neutral, and dry. Put the dried sample into a muffle furnace, heat to 500℃ at a rate of 3℃ / min, and roast for 3h. Use XRD to characterize the crystal phase of the catalyst, and use XPS to characterize the surface oxygen defects of the material, such as Figure 1-1 , Figure 1-2 As shown, it is pure h-In 2 O 3 The XPS method is used to detect the binding energy of O1s. Taking the total amount of all oxygen species on the surface as 100%, the proportion of oxygen vacancies in the hexagonal indium oxide in the surface oxygen species is 33%, which belongs to the oxygen-rich pure phase h-In 2 O 3 .

[0050] 1g of sample was put into the mold, and the pressed piece was taken out after being pressed at 20MPa for 5min. The pressed piece was crushed in a mortar and sieved with a 40-60 mesh screen to granulate the catalyst. After the catalyst was granulated, the temperature was raised to 200°C in a hydrogen atmosphere, and then the reaction gas was switched to increase the pressure and react. The specific reaction conditions included: 180°C, 4MPa gauge pressure, and an air velocity of 24000ml·h -1 ·g -1 , the volume ratio of hydrogen to carbon dioxide is 4:1.

[0051] The activity evaluation results of the catalyst are shown in Figure 2 From the figure, it can be seen that the catalyst has stable performance. After 150 hours of reaction, the activity of the catalyst has not decreased at all. In order to understand the surface composition and structural changes of the catalyst after the reaction, XRD diffraction analysis was performed. Figure 3-1 ,Depend on Figure 3-1 , Figure 3-2 It can be seen that the structure of the catalyst after the reaction has not changed compared with the fresh catalyst, and no reduction peak of indium species was observed.

[0052] Example 2

[0053] The catalyst synthesis steps shown in Example 1 were followed, with only the type of solvent changed to a mixed solution of acetone and anhydrous ethanol, with the volume ratio of acetone / anhydrous ethanol being 9. The catalyst evaluation method was the same as in Example 1, and the catalytic reaction results are shown in Table 1.

[0054] Example 3

[0055] The catalyst synthesis steps shown in Example 1 were followed, with only the type of solvent changed to a mixed solution of acetone and anhydrous ethanol, with the volume ratio of acetone / anhydrous ethanol being 4. The catalyst evaluation method was the same as in Example 1, and the catalytic reaction results are shown in Table 1.

[0056] Example 4

[0057] The catalyst synthesis steps shown in Example 1 were followed, with only the type of precipitant being changed, using urea corresponding to Example 4(1) and ammonia water corresponding to Example 4(2) in the same molar amount as sodium hydroxide. The catalyst evaluation method was the same as that in Example 1, and the catalytic reaction results are shown in Table 1.

[0058] Example 5

[0059] According to the catalyst synthesis steps shown in Example 1, the catalyst calcination time and temperature were changed to obtain the catalyst of the present invention. The preparation method of the catalyst is shown in Table 2. When the catalyst calcination temperature is less than 600°C, the space-time yield is greater than 0.55 g MeOH / g cat. / h. When the calcination temperature is greater than 800 °C, the catalyst particles sinter and the activity decreases slightly, but the pure phase h-In2 O 3 .

[0060] Example 6

[0061] According to the catalyst synthesis steps shown in Example 1, the same molar amount of indium chloride as in Example 1 was used as the precursor indium salt, the same molar amount of urea as the precipitant, a mixed solution of acetone and anhydrous ethanol (the volume ratio of acetone / anhydrous ethanol was 9, and crystallization was carried out at 120° C. for 16 h. The same method as in Example 1 was used for verification, and it was found that the results were similar to those in Example 1.

[0062] Example 7

[0063] According to the catalyst synthesis steps shown in Example 1, the same molar amount of indium chloride as in Example 1 was used as the precursor indium salt, 1.5 times the amount of ammonia water as the precipitant of Example 1, a mixed solution of acetone and anhydrous ethanol, the volume ratio of acetone / anhydrous ethanol was 3 / 2, and crystallization was carried out at 200° C. for 5 hours. The same method as in Example 1 was used for verification, and the results were found to be similar to those in Example 1.

[0064] The indium oxide catalysts obtained in Examples 2-7 were all pure h-In by the same method as in Example 1. 2 O 3， The proportion of oxygen vacancies in the hexagonal indium oxide to the surface oxygen species is above 30%.

[0065] Comparative Example 1

[0066] Preparation of catalyst: Weigh 4.5124g of indium nitrate and 2.16g of sodium hydroxide as precipitant, dissolve in 50ml of isopropanol and stir for 3h, then add water and heat in autoclave for crystallization, keep at 150℃ for 10h. After cooling to room temperature, centrifuge, wash with the same solvent until neutral, and dry. Put the dried sample in a muffle furnace, heat to 500℃ at a rate of 3℃ / min, and roast for 3h. XRD is used to characterize the crystal phase of the catalyst, such as Figure 4 As shown, it is a mixed phase In 2 O 3 .

[0067] The evaluation method of the catalyst is the same as that of Example 1. The catalytic reaction results are shown in Table 1.

[0068] Comparative Example 2

[0069] Preparation of catalyst: Weigh 4.5124g of indium nitrate and 2.16g of sodium hydroxide as precipitant, dissolve in 50ml of 1,4-dioxane and stir for 3h, then add water to heat the autoclave for crystallization, and keep at 150℃ for 10h. After cooling to room temperature, centrifuge, wash with the same solvent until neutral, and dry. Put the dried sample into a muffle furnace, heat to 500℃ at a rate of 3℃ / min, and roast for 5h. Use XRD to characterize the crystal phase of the catalyst, such as Figure 5 As shown, it is a mixed phase In 2 O 3 .

[0070] The evaluation method of the catalyst is the same as that of Example 1. The catalytic reaction results are shown in Table 1.

[0071] Comparative Example 3

[0072] Preparation of catalyst: Weigh 4.5124g of indium nitrate and 2.16g of sodium hydroxide as precipitant, dissolve in 50ml of tetrahydrofuran and stir for 3h, then add water and heat in autoclave for crystallization, keep at 150℃ for 10h. After cooling to room temperature, centrifuge, wash with the same solvent until neutral, and dry. Put the dried sample in a muffle furnace, heat to 500℃ at a rate of 3℃ / min, and roast for 3h. The catalyst shows heterogeneous In 2 O 3 .

[0073] The evaluation method of the catalyst is the same as that of Example 1. The catalytic reaction results are shown in Table 1.

[0074] Comparative Example 4

[0075] Preparation of catalyst: Weigh 4.5124g of indium nitrate and 3.61g of precipitant urea, dissolve in 50ml of a mixed solution of anhydrous ethanol and deionized water (wherein the volume of anhydrous ethanol is 48ml corresponding to Example 4(1), the volume of anhydrous ethanol is 40ml corresponding to Example 4(2), and the volume of anhydrous ethanol is 25ml corresponding to Example 4(3), stir for 3h, then add water to a hot autoclave for crystallization, and keep at 150℃ for 10h. After cooling to room temperature, centrifuge, wash with the same anhydrous ethanol and deionized water solvent until neutral, and dry. Put the dried sample into a muffle furnace, heat to 500℃ at a rate of 3℃ / min, and calcine for 3h. The crystal phase of the catalyst is characterized by XRD, as shown in FIG. Figure 6 As shown, it is a mixed phase In 2 O 3 .

[0076] The evaluation method of the catalyst is the same as that of Example 1. The catalytic reaction results are shown in Table 1.

[0077] Comparative Example 5

[0078] Preparation of catalyst: Weigh 4.5124g of indium nitrate and 2.16g of sodium hydroxide as precipitant, dissolve in 50ml of a mixed solution of acetone and isopropanol, with a volume ratio of acetone / isopropanol of 3 / 2, stir for 3h, then add water to a hot autoclave for crystallization, and keep at 150℃ for 10h. After cooling to room temperature, centrifuge, wash with the same solvent until neutral, and dry. Put the dried sample into a muffle furnace, heat to 500℃ at a rate of 3℃ / min, and roast for 5h. The crystal phase of the catalyst was characterized by XRD, showing a heterogeneous phase In 2 O 3 .

[0079] The evaluation method of the catalyst is the same as that of Example 1. The catalytic reaction results are shown in Table 1.

[0080] Table 1

[0081]

[0082]

[0083] Table 2

[0084] Example 5 Calcination temperature / ℃ Calcination time / h Grain size / nm 1 400 3 9 2 500 1 12 3 500 3 15 4 500 6 30 5 600 3 19 6 700 3 26 7 800 3 30

[0085] As shown in Table 1, the catalyst of the present invention can catalyze CO at low temperature and high efficiency. 2 Hydrogenation to methanol can stably catalyze the operation of carbon dioxide hydrogenation to methanol for a long period of time, and there is no obvious deactivation during the reaction. In the carbon dioxide hydrogenation to methanol reaction, it shows high reaction stability, resistance to over-reduction, and high yield of the target product.

[0086] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

[0087] All publications, patent applications, patents and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of a conflict, the definition in this specification shall prevail.

[0088] When this specification uses the prefix "well-known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by the prefix cover those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become recognized in the art as being suitable for similar purposes.

[0089] The endpoints and any values ​​of the scope disclosed in the present application document are not limited to the precise scope or value, and these scopes or values ​​should be understood to include values ​​close to these scopes or values. For numerical ranges, between the endpoint values ​​of each scope, between the endpoint values ​​of each scope and a separate point value, and between separate point values, one or more new numerical ranges can be combined with each other, and these numerical ranges should be considered as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be considered as specifically disclosed in this article.

[0090] In the context of the present specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

[0091] Moreover, any embodiment described in this document may be freely combined with one or more other embodiments described in this document, and the technical solutions or technical ideas formed thereby are deemed to be part of the original disclosure or original record of the present invention, and should not be regarded as new content that has not been disclosed or anticipated in this document, unless a person skilled in the art considers that the combination is obviously unreasonable.

Claims

1. A method for preparing hexagonal indium oxide, comprising mixing an indium precursor salt, a precipitant and a solvent to obtain a reaction solution, crystallizing the reaction solution to obtain a hexagonal indium oxide precursor; calcining the obtained hexagonal indium oxide precursor to obtain hexagonal indium oxide; in, The precipitant is at least one of sodium hydroxide, ammonia water and urea; The solvent is acetone, or a mixture of acetone and ethanol.

2. The preparation method according to claim 1, Features: The indium precursor salt is selected from at least one of indium nitrate, indium acetylacetonate and indium chloride; and / or, The molar ratio of the precipitant to the indium precursor salt is (1.2-2):

1.

3. The preparation method according to claim 1, Features: The amount of the solvent used is 1250-5000 mL per 1 mol of the indium precursor salt; and / or, When the solvent is a mixture of acetone and ethanol, the volume percentage of acetone is ≥60%.

4. The preparation method according to claim 1, Features: The crystallization conditions include: a temperature of 90-180° C.; and / or a time of 5-20 h.

5. The preparation method according to claim 1, Features: The calcination conditions include: a calcination temperature of 300-800° C., and / or a calcination time of 1-5 h; preferably, the temperature is increased to the calcination temperature at a heating rate of 1-3° C. / min.

6. The preparation method according to any one of claims 1 to 5, Features: The hexagonal indium oxide is pure hexagonal indium oxide; and / or, The grain size of the hexagonal indium oxide is 10-20 nm; Preferably, the binding energy of O1s is detected by XPS method, and the proportion of oxygen vacancies in the hexagonal indium oxide in all oxygen species on the surface is above 30%, taking the total amount of all oxygen species on the surface as 100%.

7. A hexagonal indium oxide, wherein the hexagonal indium oxide is pure phase hexagonal indium oxide, and the binding energy of O1s is detected by XPS method, and the proportion of oxygen vacancies in the hexagonal indium oxide in all oxygen species on the surface is greater than 30%, based on the total amount of all oxygen species on the surface as 100%; and / or, The hexagonal indium oxide is prepared by the preparation method described in any one of claims 1 to 6; preferably, The grain size of the hexagonal indium oxide is 10-20 nm.

8. Use of the hexagonal indium oxide prepared by the preparation method according to claims 1 to 6 or the hexagonal indium oxide according to claim 7 as a hydrogenation catalyst, preferably in the production of methanol.

9. A method for producing methanol, wherein carbon dioxide and hydrogen are contacted with a catalyst to react to produce methanol; in, The catalyst is hexagonal indium oxide prepared by the preparation method described in claims 1-6 or the hexagonal indium oxide described in claim 7.

10. The method according to claim 9, Features: The contact reaction conditions include: a temperature of 150-250° C., and / or a pressure of 2-5 MPa; and / or a space velocity of 24000-96000 ml·h -1 ·g -1 and / or, The contact reaction is carried out in a fixed bed reactor.

11. The method according to claim 9 or 10, Features: First, the temperature is raised to the temperature of the contact reaction, and then carbon dioxide and hydrogen are introduced to contact the catalyst; preferably, The atmosphere during the heating process is at least one of hydrogen, argon and nitrogen; more preferably, it is one of hydrogen, argon, a mixture of hydrogen and argon, and nitrogen.

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