Magnesium-aluminum modified indium oxide catalyst, its preparation method and application, and method for preparing methanol by hydrogenation of carbon dioxide

Abstract

The present invention relates to the technical field of catalysts, and discloses a magnesium-aluminum modified indium oxide catalyst, a preparation method and application thereof, and a method for hydrogenating carbon dioxide to prepare methanol. The magnesium-aluminum modified indium oxide catalyst comprises an active component and a doping component. The active component is indium oxide having a cubic structure, and the doping component is a mixture of magnesium oxide and aluminum oxide. The content of the active component accounts for 40-85% of the total mass of the catalyst, and the doping component accounts for 15-60% of the total mass of the catalyst. The preparation method of the magnesium-aluminum modified indium oxide catalyst of the present invention includes: mixing a solution containing a metal indium salt, a precipitant solution and a doping component to obtain a precipitation mother liquor; aging the precipitation mother liquor to form a precipitate; separating the precipitate product from solid and liquid, and then performing drying and calcination. The magnesium-aluminum modified indium oxide catalyst of the present invention has the advantages of excellent catalytic performance, high reaction activity, high selectivity of target products, etc., and the process steps are simple, which can effectively reduce its production cost.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and particularly relates to a magnesium-aluminum modified indium oxide catalyst, a preparation method and application thereof, and a method for hydrogenating carbon dioxide to prepare methanol. Background Art

[0002] As an important raw material for chemicals and a substitute for fossil fuels, methanol is prepared by reacting CO 2 with H from renewable energy 2 This is not only an effective way to control greenhouse gases but also to replace fossil fuels.

[0003] For the hydrogenation of CO 2 to prepare methanol, a variety of catalyst systems have been developed, such as copper-based catalysts, cobalt-based catalysts, noble metal catalysts, ZnO catalysts, etc. Among these catalysts, modified copper-based catalysts have been studied and applied for a long time. The traditional copper-based catalysts for synthesizing methanol from syngas have been widely studied in the hydrogenation of carbon dioxide to methanol. However, the methanol selectivity in this catalytic reaction process is only about 60%, the side reaction (RWGS) activity is high, and the characteristics of H 2 O-induced sintering of the active phase and poor stability limit its further application. In other catalytic systems, the high cost of noble metals and the low activity and easy migration of ZnO also limit the further application of these catalysts in this field to a certain extent.

[0004] Indium oxide has moderate CO 2 and CO adsorption capacities, showing significantly better methanol selectivity than copper, cobalt, and noble metal catalysts, and higher catalytic activity than ZnO catalysts. Therefore, it has attracted extensive attention from scientific researchers. How to further design and develop more effective indium oxide catalysts to promote the activation of carbon dioxide and H 2 and stabilize key intermediates to achieve high activity, high selectivity, and high stability is still the research focus of the efficient hydrogenation of CO 2 to methanol. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problem that the catalytic performance of indium oxide in the prior art needs to be further improved, and to provide a magnesium-aluminum modified indium oxide catalyst, a preparation method and application thereof, and a method for hydrogenating carbon dioxide to prepare methanol. The catalyst provided by the present invention has excellent catalytic performance, high reaction activity, high selectivity for target products, and a simple preparation process and low production cost.

[0006] To achieve the above object, a first aspect of the present invention provides a magnesium-aluminum modified indium oxide catalyst, which comprises an active component and a doping component. The active component is indium oxide having a cubic structure, and the doping component is a mixture of magnesium oxide and aluminum oxide. Among them, the content of the active component accounts for 40-85% of the total mass of the catalyst, and the doping component accounts for 15-60% of the total mass of the catalyst.

[0007] A second aspect of the present invention provides a method for preparing a magnesium-aluminum modified indium oxide catalyst, which comprises the following steps:

[0008] (1) Mix a solution containing a metal indium salt, a precipitant solution and a doping component to obtain a precipitation mother liquor;

[0009] (2) Age the precipitation mother liquor to form a precipitate;

[0010] (3) Perform solid-liquid separation on the product obtained in step (2), and then perform drying and calcination;

[0011] The doping component is a mixture of magnesium oxide and aluminum oxide.

[0012] A third aspect of the present invention provides the use of the magnesium-aluminum modified indium oxide catalyst of the present invention or the magnesium-aluminum modified indium oxide catalyst prepared by the preparation method of the present invention in the reaction of hydrogenating carbon dioxide to prepare methanol.

[0013] A fourth aspect of the present invention provides a method for preparing methanol by hydrogenating carbon monoxide, which comprises: contacting carbon dioxide and hydrogen with a catalyst under the condition of hydrogenating carbon dioxide; the catalyst is the magnesium-aluminum modified indium oxide catalyst of the present invention or the magnesium-aluminum modified indium oxide catalyst prepared by the preparation method of the present invention.

[0014] Through the above technical solutions, the magnesium-aluminum modified indium oxide catalyst of the present invention uses a mixture of magnesium oxide and aluminum oxide as the doping component of the indium oxide catalyst, effectively improving the contact and catalytic effect between the active component indium oxide and the catalytic substrate (such as carbon dioxide and H 2 ), not only can promote the activation of the catalytic substrate, but also effectively improve the selectivity of hydrogenating carbon dioxide to methanol. Under the conditions of 3 MPa and 10,000 h -1 , the selectivity of methanol on this catalyst can reach 78%. Under the condition of 5 MPa, the selectivity of methanol on this catalyst can reach 98%.

[0015] The preparation method of the magnesium-aluminum modified indium oxide catalyst according to the present invention forms indium oxide by aging precipitation treatment in the presence of doping components. This not only enables the effective infiltration of doping components into indium oxide for modification, resulting in a catalyst with excellent catalytic performance, high reaction activity, and high selectivity for target products, but also has simple process steps, can effectively reduce its production cost, and can achieve mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the TEM image of the doping component prepared in Example 1 of the present invention;

[0017] Figure 2 is the XRD pattern of the magnesium-aluminum modified indium oxide catalyst prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0019] The first aspect of the present invention provides a magnesium-aluminum modified indium oxide catalyst. The catalyst includes an active component and a doping component. The active component is indium oxide with a cubic structure, and the doping component is a mixture of magnesium oxide and aluminum oxide. Among them, the content of the active component accounts for 40 - 85% of the total mass of the catalyst, and the doping component accounts for 15 - 60% of the total mass of the catalyst.

[0020] The content of each component in the catalyst of the present invention can be obtained by XRF method, and the structure of the active component is obtained by XRD method.

[0021] According to the present invention, in the magnesium-aluminum modified indium oxide catalyst, magnesium oxide and aluminum oxide are used as doping components to modify indium oxide through doping with indium oxide, effectively promoting the contact and catalytic effect between the active component indium oxide and the catalytic substrate (such as carbon dioxide and H 2 )), which can not only promote the activation of the catalytic substrate, but also effectively improve the selectivity of hydrogenation of carbon dioxide to methanol.

[0022] According to the present invention, the doping component can be magnesium oxide and aluminum oxide with a conventional structure. In order to further increase the contact area between the active component and the catalytic substrate and improve the catalytic effect while modifying the active component, preferably, the doping component has an ordered mesoporous structure.

[0023] According to the present invention, the ordered mesoporous structure of the doping component can be determined by testing with the TEM method.

[0024] According to the present invention, in order to further improve the catalytic performance of the magnesium-aluminum modified indium oxide catalyst, preferably, the content of the active component accounts for 65-75% of the total mass of the catalyst, and the doping component accounts for 25-35% of the total mass of the catalyst.

[0025] According to the present invention, in order to further improve the catalytic performance of the magnesium-aluminum modified indium oxide catalyst and the selectivity for the target product, preferably, the mass ratio of the active component to the doping component is 1-6:1, and more preferably 1-3:1.

[0026] According to the present invention, in order to improve the modification effect of the doping component on the active component and enhance the stability of the catalyst, preferably, magnesium oxide accounts for 3-24% of the total mass of the catalyst, and more preferably 3.75-10.5%; aluminum oxide accounts for 12-51% of the total mass of the catalyst, and more preferably 17.5-29.75%.

[0027] The second aspect of the present invention provides a method for preparing a magnesium-aluminum modified indium oxide catalyst, and the method includes the following steps:

[0028] (1) Mix a solution containing a metal indium salt, a precipitant solution and a doping component to obtain a mother liquor of the precipitate;

[0029] (2) Age the mother liquor of the precipitate to form a precipitate;

[0030] (3) Perform solid-liquid separation on the product obtained in step (2), and then perform drying and calcination;

[0031] The doping component is a mixture of magnesium oxide and aluminum oxide.

[0032] According to the present invention, there is no particular limitation on the specific operation methods of solid-liquid separation, drying and calcination, and they can be carried out according to the conventional operation means in the art.

[0033] According to the present invention, in the method for preparing a magnesium-aluminum modified indium oxide catalyst, aging precipitation treatment is adopted in the presence of a doping component to form the active component indium oxide. Not only can the doping component effectively penetrate into indium oxide for modification, making the prepared catalyst have excellent catalytic performance, high reaction activity, high selectivity for the target product, good reaction stability, low catalyst deactivation rate and other advantages, but also the process steps are simple, the production cost can be effectively reduced, and large-scale production can be realized.

[0034] According to the present invention, in order to improve the catalytic performance of the magnesium-aluminum modified indium oxide catalyst, preferably, the amounts of the metal indium salt and the doping component are such that in the prepared catalyst, the indium oxide content accounts for 40-85% of the total mass of the catalyst, and the doping component accounts for 15-60% of the total mass of the catalyst. In a further preferred case, the amounts of the metal indium salt and the doping component are such that in the prepared catalyst, the indium oxide content accounts for 65-75% of the total mass of the catalyst, and the doping component accounts for 25-35% of the total mass of the catalyst;

[0035] According to the present invention, in order to further improve the catalytic performance of the magnesium-aluminum modified indium oxide catalyst and the selectivity for the target product, preferably, the mass ratio of the metal indium salt and the doping component in terms of oxides is 1-6:1, and more preferably 1-3:1.

[0036] According to the present invention, there is no particular limitation on the type of the metal indium salt, as long as it can form a corresponding salt solution form and react with a precipitating agent to form indium oxide. For example, it can be at least one of indium nitrate, indium chloride, and indium sulfate. The above substances are all conventional selections in the art and can be obtained through commercial purchase.

[0037] According to the present invention, preferably, the precipitating agent is urea. In this preferred embodiment, it is more beneficial to enable the precipitation mother liquor formed by mixing the precipitating agent with the metal indium salt and the doping component to form indium oxide with a cubic structure in the form of aging precipitation, and at the same time realize the modification effect of the doping component on indium oxide.

[0038] According to the present invention, preferably, the solvents in the solution containing the metal indium salt and the precipitating agent solution in step (1) are independently an organic solvent and / or water, and preferably an organic solvent and water.

[0039] Preferably, the organic solvent is selected from at least one of ethanol, methanol, isopropanol, ethylene glycol, triethylene glycol, and N,N-dimethylacetamide. Exemplarily, the solution containing the metal indium salt is obtained by dissolving the metal indium salt in a mixed solution of ethanol and deionized water, and the precipitating agent solution is obtained by dissolving the precipitating agent in a mixed solution of ethanol and deionized water. Among them, the usage ratio of ethanol to deionized water is not particularly limited as long as the metal indium salt or the precipitating agent can be effectively dissolved respectively.

[0040] According to the present invention, the concentrations of the indium metal salt solution and the precipitant solution are not particularly limited. To promote the full reaction of the indium metal salt and the precipitant and improve the reaction efficiency, preferably, the concentration of the indium metal salt solution is 0.1 - 0.8 mol / L, specifically it can be 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.7 mol / L, 0.8 mol / L, or any value within the range formed by any two of the above values; preferably, the concentration of the precipitant solution is 1 - 2 mol / L, specifically it can be 1 mol / L, 1.5 mol / L, 2 mol / L, or any value within the range formed by any two of the above values.

[0041] According to the present invention, the dosage ratio of the indium metal salt and the precipitant is such that it can fully convert the indium metal salt into indium oxide. Under preferred conditions, the molar ratio of indium in the indium metal salt to the precipitant is 1:6 - 7. Research has shown that under this molar ratio condition, the carbon dioxide conversion rate and methanol yield can be greatly improved.

[0042] According to the present invention, in order to make the indium metal salt, the precipitant, and the doping component in the precipitation mother liquor fully mixed and uniform, and improve the efficiency of aging precipitation, preferably, the mixing in step (1) is carried out under stirring conditions, preferably for 1 - 10 h, wherein the stirring speed can be 100 rpm - 500 rpm.

[0043] According to the present invention, preferably, the mixing in step (1) includes first mixing the indium metal salt solution and the precipitant solution, and then adding the doping component. The first mixing can be carried out by a conventional mixing method, for example, adding the indium metal salt solution to the precipitant solution for mixing. To optimize the mixing effect of the two, preferably, the process of the first mixing is: adding the precipitant solution dropwise to the indium metal salt solution.

[0044] According to the present invention, when preparing the magnesium-aluminum modified indium oxide catalyst, the doping component can be commercially available magnesium oxide and aluminum oxide, or magnesium oxide and aluminum oxide prepared by existing methods. In order to modify the active component while further increasing the contact area between the active component and the catalytic substrate and enhancing the catalytic effect, preferably, the preparation method of the doping component makes the doping component have an ordered mesoporous structure, and further preferably, the solvent evaporation-induced self-assembly method is used to prepare the doping component.

[0045] According to a preferred embodiment of the present invention, the preparation method of the doping component includes: in the presence of a surfactant and in the presence of a solvent, mixing an acid, an aluminum precursor, and a magnesium precursor, and then drying and calcining.

[0046] According to the present invention, in order to improve the modification effect of the doping component on indium oxide and enhance the stability of the catalyst, preferably, the amounts of the aluminum precursor and the magnesium precursor are such that in the prepared catalyst, magnesium oxide accounts for 3-24% of the total mass of the catalyst, more preferably 3.75-10.5%; aluminum oxide accounts for 12-51% of the total mass of the catalyst, more preferably 17.5-29.75%.

[0047] According to the present invention, preferably, the surfactant is selected from at least one of P123 (polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer), CTAB (cetyltrimethylammonium bromide), malic acid, sodium 2-ethylhexane sulfosuccinate, and nonylphenol polyoxyethylene ether.

[0048] According to the present invention, preferably, the solvent is selected from at least one of ethanol, methanol, isopropanol, ethylene glycol, triethylene glycol, and N,N-dimethylacetamide.

[0049] According to the present invention, preferably, the acid is at least one of nitric acid, hydrochloric acid, and phosphoric acid.

[0050] According to the present invention, preferably, the aluminum precursor is at least one of aluminum isopropoxide, aluminum nitrate, aluminum chloride, and aluminum sulfate.

[0051] In the present invention, there is no particular limitation on the type of the magnesium precursor, as long as it contains magnesium element. For example, it can be at least one of magnesium nitrate, magnesium chloride, and magnesium oxide.

[0052] The above substances can all be obtained through commercial purchase.

[0053] Preferably, the preparation method of the doping component in the present invention includes: mixing P123 and absolute ethanol and dissolving them under ultrasonic treatment, then adding concentrated nitric acid, and after clarification, adding aluminum isopropoxide and magnesium nitrate, and carrying out stirring reaction followed by drying and calcination.

[0054] Preferably, the molar ratio of the surfactant, the solvent, the acid to the aluminum precursor is 0.01-0.05:10-80:1-10:1, more preferably 0.01-0.03:20-50:2-6:1.

[0055] According to the present invention, in the preparation method of the doping component, the mixing time is 3-9 h, and more preferably the mixing is carried out under stirring conditions.

[0056] According to the present invention, the drying conditions in the preparation method of the doping component preferably include: the temperature is 60-90°C, specifically it can be 60°C, 70°C, 80°C, 90°C, or any value within the range formed by any two of the above values; the time is 36-60h, specifically it can be 36h, 40h, 45h, 50h, 55h, 60h, or any value within the range formed by any two of the above values; the roasting conditions preferably include: the temperature is 600-1200°C, specifically it can be 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, or any value within the range formed by any two of the above values; the time is 3-6h, specifically it can be 3h, 4h, 5h, 6h, or any value within the range formed by any two of the above values.

[0057] According to the present invention, preferably, the aging conditions in step (2) include: the temperature is 80-180°C, specifically it can be 80°C, 100°C, 120°C, 140°C, 160°C, 180°C, or any value within the range formed by any two of the above values, and more preferably it is 120-160°C; the time is 12-22h, specifically it can be 12h, 14h, 16h, 18h, 20h, 22h, or any value within the range formed by any two of the above values, and more preferably it is 18-20h. The aging reaction in step (2) is a hydrothermal reaction, and preferably the aging reaction is carried out under closed conditions. The aging of the precipitation mother liquor can be carried out in a hydrothermal synthesis reactor. Specifically, the precipitation mother liquor can be placed in a hydrothermal synthesis reactor, and the hydrothermal synthesis reactor can be placed in an oven for the aging.

[0058] According to a preferred embodiment of the present invention, the method further includes washing the product obtained in step (2), and preferably washing until the pH value of the product obtained in step (2) is between 6 and 8. According to the present invention, the washing method is not particularly limited and can be carried out according to the conventional technical means in the art. Preferably, the centrifugation method can be adopted, and centrifugation can simultaneously achieve the above-mentioned solid-liquid separation and washing.

[0059] According to the present invention, preferably, the drying conditions in step (3) include: the temperature is 60-90°C, specifically it can be 60°C, 70°C, 80°C, 90°C, or any value within the range formed by any two of the above values; the time is 12-24h, specifically it can be 12h, 14h, 16h, 18h, 20h, 22h, 24h, or any value within the range formed by any two of the above values.

[0060] According to the present invention, preferably, the conditions of the roasting in step (3) include: the temperature is 300 - 500 °C, specifically it can be 300 °C, 350 °C, 400 °C, 450 °C, 500 °C, or any value within the range formed by any two of the above values; the time is 3 - 6 h, specifically it can be 3 h, 4 h, 5 h, 6 h, or any value within the range formed by any two of the above values.

[0061] According to a particularly preferred embodiment of the present invention, a method for preparing a magnesium-aluminum modified indium oxide catalyst, the method comprising the following steps:

[0062] (1) Mix a surfactant and a solvent, dissolve them under ultrasonic waves, then add an acid. After clarification, add an aluminum precursor and a magnesium precursor, stir for 3 - 9 h, dry at 60 - 90 °C for 36 - 60 h, and then roast at 600 - 1200 °C for 3 - 6 h to obtain a doped component;

[0063] (2) Dissolve a metal indium salt in a solvent to prepare a solution containing the metal indium salt, and dissolve a precipitant in a solvent to prepare a precipitant solution; dropwise add the precipitant solution to the solution containing the metal indium salt, and then add the doped component obtained in step (1), stir for 1 h - 10 h to obtain a precipitation mother liquor;

[0064] (3) Age the precipitation mother liquor obtained in step (2) at a temperature of 80 - 160 °C for 12 - 22 h to form a precipitate;

[0065] (4) After solid-liquid separation of the product obtained in step (3), wash it until the pH value is between 6 - 8, then dry at 60 - 90 °C for 12 - 24 h, and roast at 300 - 500 °C for 3 - 6 h to obtain the magnesium-aluminum modified indium oxide catalyst.

[0066] The magnesium-aluminum modified indium oxide catalyst provided by the present invention has the advantages of high reaction activity, high selectivity for the target product, good reaction stability, and low catalyst deactivation rate when used in the reaction of hydrogenating carbon dioxide to prepare methanol. Therefore, in the third aspect of the present invention, there is provided the use of the magnesium-aluminum modified indium oxide catalyst described in the present invention or the magnesium-aluminum modified indium oxide catalyst prepared by the preparation method described in the present invention in the reaction of hydrogenating carbon dioxide to prepare methanol.

[0067] In the fourth aspect of the present invention, there is provided a method for preparing methanol by hydrogenating carbon monoxide, the method comprising: under the conditions of hydrogenating carbon dioxide, bringing carbon dioxide and hydrogen into contact with a catalyst; the catalyst is the magnesium-aluminum modified indium oxide catalyst described in the present invention or the magnesium-aluminum modified indium oxide catalyst prepared by the preparation method described in the present invention. By this method, the above-mentioned magnesium-aluminum modified indium oxide catalyst is used in a fixed bed for the reaction of hydrogenating carbon monoxide to prepare methanol.

[0068] According to the present invention, in order to improve the reaction efficiency of hydrogenation of carbon dioxide to methanol, preferably, the carbon dioxide hydrogenation conditions include: the reaction pressure is between 1.0 - 5.0 MPa, the reaction temperature is between 200 - 400 °C, the volume space velocity of the raw materials (including carbon dioxide and hydrogen) is between 4500 - 18000 h -1 between, H 2 / CO 2 The molar ratio is between 1 - 6. Further preferably, the carbon dioxide hydrogenation conditions include: the reaction pressure is between 3 - 5 MPa, the reaction temperature is between 240 - 300 °C, the volume space velocity of the raw materials is between 7000 - 12000 h -1 between, H 2 / CO 2 The molar ratio is between 3 - 6.

[0069] The present invention will be described in detail below through examples.

[0070] In the following examples and comparative examples, unless otherwise specified, the substances used are all commercially available, and the room temperature is 25 ± 5 °C;

[0071] P123 is commercially available from Sigma - aldrich, and its brand is poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol).

[0072] The structure of the magnesium - aluminum modified indium oxide catalyst was measured by XRD, and the content of each component in the catalyst was tested by the XRF method.

[0073] Example 1

[0074] (1) Mix 5.1 g of surfactant P123 and 100 mL of absolute ethanol, dissolve them under ultrasound, then add 7.3 mL of concentrated nitric acid. After clarification, add 10.7 g of aluminum isopropoxide and 3.8 g of magnesium nitrate, stir and mix for 5 h, dry at 60 °C for 48 h, and finally calcine at 800 °C for 3 h to obtain the doped component. Perform TEM analysis on the obtained doped component, Figure 1 The results show that the doped component has an ordered mesoporous structure;

[0075] (2) Add 8.2 g of In(NO 3 ) 3 ·4H 2O is added to a mixture of 50 mL of anhydrous ethanol and 25 mL of deionized water to obtain a solution containing a metal indium salt, 8 g of urea is added to a mixture of 60 mL of anhydrous ethanol and 20 mL of deionized water to obtain a precipitant solution, the precipitant solution is added dropwise to the solution containing the metal indium salt at 30° C., and then 1.2 g of the doping component obtained in step (1) is added, and the mixture is stirred at a speed of 200 rpm for 4 h to obtain a precipitation mother solution;

[0076] (3) adding the precipitation mother solution obtained in step (2) into a 100 mL polytetrafluoroethylene-lined hydrothermal synthesis reactor, placing the reactor in a forced air drying oven for aging at 120° C. for 18 h to form a precipitate;

[0077] (4) The product obtained in step (3) was naturally cooled to room temperature and then centrifuged, and the centrifugal precipitate was washed with deionized water until the pH value was 8, and then dried at 60° C. for 15 h, and then calcined at 380° C. for 3 h to obtain a magnesium aluminum modified indium oxide catalyst (the contents of each component are shown in Table 1), and the tablets were sieved into 40-60 mesh; the obtained magnesium aluminum modified indium oxide catalyst was characterized and analyzed by XRD, Figure 2 The results show that its indium oxide has a cubic structure;

[0078] (5) In a stainless steel reactor with an inner diameter of 8 mm, the carbon dioxide was hydrogenated to produce methanol, and the magnesium-aluminum modified indium oxide catalyst prepared in step (4) was used as the reaction catalyst. The reaction conditions were as follows: the reaction pressure was 5.0 MPa, the reaction temperature was 340° C., and the volume space velocity of the raw materials (carbon dioxide and hydrogen) was 18000 h -1 , H 2 / CO 2 The molar ratio was 5. After the reaction was completed, the liquid product was collected in an ice-water bath. The product composition was analyzed by gas chromatography. The evaluation results are shown in Table 2.

[0079] Example 2

[0080] (1) 4.6 g of surfactant P123 and 90 ml of anhydrous ethanol were mixed and dissolved under ultrasound, and then 7.6 mL of concentrated nitric acid was added. After clarification, 8.4 g of aluminum isopropoxide and 4.8 g of magnesium nitrate were added, and the mixture was stirred for 5 h, dried at 60 ° C for 48 h, and finally calcined at 800 ° C for 3 h to obtain a doping component with an ordered mesoporous structure;

[0081] (2) 9.3 g In(NO 3 ) 3 ·4H 2O is added to a mixture of 80 mL of anhydrous ethanol and 40 mL of deionized water to obtain a solution containing a metal indium salt, 9.2 g of urea is added to a mixture of 80 mL of anhydrous ethanol and 30 mL of deionized water to obtain a precipitant solution, the precipitant solution is added dropwise to the solution containing the metal indium salt at 30° C., and then 1.2 g of the doping component obtained in step (1) is added, and the mixture is stirred at a speed of 150 rpm for 7 h to obtain a precipitation mother solution;

[0082] (3) adding the precipitation mother solution obtained in step (2) into a 100 mL polytetrafluoroethylene-lined hydrothermal synthesis reactor, placing the reactor in a forced air drying oven for aging at a temperature of 130° C. for 20 h to form a precipitate;

[0083] (4) The product obtained in step (3) was naturally cooled to room temperature and then centrifuged, washed with deionized water to obtain a centrifugal precipitate with a pH of 6, and then dried at 80° C. for 12 h, and then calcined at 450° C. for 3 h to obtain a magnesium-aluminum modified indium oxide catalyst (the contents of each component of which are shown in Table 1), which was pressed into tablets and sieved into 40-60 mesh. The indium oxide in the obtained catalyst had a cubic structure;

[0084] (5) The reaction of hydrogenating carbon dioxide to produce methanol was carried out in a stainless steel reactor with an inner diameter of 8 mm, using the magnesium-aluminum modified indium oxide catalyst prepared in step (4) as the reaction catalyst, and the reaction conditions were as follows: reaction pressure of 1.0 MPa, reaction temperature of 400° C., volume space velocity of raw materials (carbon dioxide and hydrogen) of 9000 h -1 , H 2 / CO 2 The molar ratio was 4. After the reaction was completed, the liquid product was collected in an ice-water bath. The product composition was analyzed by gas chromatography. The evaluation results are shown in Table 2.

[0085] Example 3

[0086] (1) 4.1 g of surfactant P123 and 80 mL of anhydrous ethanol were mixed and dissolved under ultrasound, and then 6.3 mL of concentrated nitric acid was added. After clarification, 4.9 g of aluminum isopropoxide and 1.2 g of magnesium nitrate were added, and the mixture was stirred for 5 h, dried at 60 ° C for 48 h, and finally calcined at 800 ° C for 3 h to obtain a doping component with an ordered mesoporous structure;

[0087] (2) 7.6 g In(NO 3 ) 3 ·4H 2O is added to a mixture of 40 mL of anhydrous ethanol and 24 mL of deionized water to obtain a solution containing a metal indium salt, 8 g of urea is added to a mixture of 40 mL of anhydrous ethanol and 10 mL of deionized water to obtain a precipitant solution, the precipitant solution is added dropwise to the solution containing the metal indium salt at 30° C., and then 2 g of the doping component obtained in step (1) is added, and the mixture is stirred at a speed of 150 rpm for 6 h to obtain a precipitation mother solution;

[0088] (3) adding the precipitation mother solution obtained in step (2) into a 100 mL polytetrafluoroethylene-lined hydrothermal synthesis reactor, placing the reactor in a forced air drying oven for aging at a temperature of 120° C. for 20 h to form a precipitate;

[0089] (4) The product obtained in step (3) was naturally cooled to room temperature and then centrifuged, washed with deionized water to obtain a centrifugal precipitate with a pH of 7, and then dried at 60° C. for 20 h, and then calcined at 350° C. for 3 h to obtain a magnesium-aluminum modified indium oxide catalyst (the contents of each component of which are shown in Table 1), which was pressed into tablets and sieved to 40-60 mesh. The indium oxide in the obtained catalyst had a cubic structure;

[0090] (5) In a stainless steel reactor with an inner diameter of 8 mm, the carbon dioxide was hydrogenated to produce methanol, and the magnesium-aluminum modified indium oxide catalyst prepared in step (4) was used as the reaction catalyst. The reaction conditions were as follows: the reaction pressure was 3.0 MPa, the reaction temperature was 280° C., and the volume space velocity of the raw materials (carbon dioxide and hydrogen) was 9000 h -1 , H 2 / CO 2 The molar ratio was 4. After the reaction was completed, the liquid product was collected in an ice-water bath. The product composition was analyzed by gas chromatography. The evaluation results are shown in Table 2.

[0091] Example 4

[0092] (1) 3.9 g of surfactant P123 and 80 ml of anhydrous ethanol were mixed and dissolved under ultrasound; then 6.1 mL of concentrated nitric acid was added, and after clarification, 9.4 g of aluminum isopropoxide and 1.6 g of magnesium nitrate were added, stirred and mixed for 5 h, dried at 60° C. for 48 h, and finally calcined at 800° C. for 3 h to obtain a doping component with an ordered mesoporous structure;

[0093] (2) 7.3 g In(NO 3 ) 3 ·4H 2O is added to a mixture of 40 mL of anhydrous ethanol and 25 mL of deionized water to obtain a solution containing a metal indium salt, 8 g of urea is added to a mixture of 60 mL of anhydrous ethanol and 20 mL of deionized water to obtain a precipitant solution, the precipitant solution is added dropwise to the solution containing the metal indium salt at 30° C., and then 1 g of the doping component obtained in step (1) is added, and the mixture is stirred at a speed of 100 rpm for 6 h to obtain a precipitation mother solution;

[0094] (3) adding the precipitation mother solution obtained in step (2) into a 100 mL polytetrafluoroethylene-lined hydrothermal synthesis reactor, placing the reactor in a forced air drying oven for aging at a temperature of 140° C. for 15 h to form a precipitate;

[0095] (4) The product obtained in step (3) was naturally cooled to room temperature and then centrifuged, and the centrifugal precipitate was washed with deionized water until the pH value was 7.5, and then dried at 60° C. for 24 h, and then calcined at 300° C. for 3 h to obtain a magnesium-aluminum modified indium oxide catalyst (the contents of each component of which are shown in Table 1), which was pressed into tablets and sieved into 40-60 mesh. The indium oxide in the obtained catalyst had a cubic structure;

[0096] (5) In a stainless steel reactor with an inner diameter of 8 mm, the carbon dioxide was hydrogenated to produce methanol, and the magnesium-aluminum modified indium oxide catalyst prepared in step (4) was used as the reaction catalyst. The reaction conditions were as follows: the reaction pressure was 5.0 MPa, the reaction temperature was 220° C., and the volume space velocity of the raw materials (carbon dioxide and hydrogen) was 7000 h -1 , H 2 / CO 2 The molar ratio was 6. After the reaction was completed, the liquid product was collected in an ice-water bath. The product composition was analyzed by gas chromatography. The evaluation results are shown in Table 2.

[0097] Example 5

[0098] (1) 6.3 g of surfactant P123 and 120 ml of anhydrous ethanol were mixed and dissolved under ultrasound, and then 8.5 ml of concentrated nitric acid was added. After clarification, 4.1 g of aluminum isopropoxide and 5.3 g of magnesium nitrate were added, and the mixture was stirred for 5 h, dried at 60 ° C for 48 h, and finally calcined at 800 ° C for 3 h to obtain a doping component with an ordered mesoporous structure;

[0099] (2) 5.4 g In(NO 3 ) 3 ·4H 2O was added to a mixed solution of 40 mL of absolute ethanol and 20 mL of deionized water to obtain a solution containing indium metal salt. 6 g of urea was added to a mixed solution of 50 mL of absolute ethanol and 20 mL of deionized water to obtain a precipitant solution. The precipitant solution was added dropwise to the solution containing indium metal salt at 30 °C, and then 0.4 g of the doping component obtained in step (1) was added. It was sufficiently stirred at a rotation speed of 150 rpm for 6 h to obtain a precipitation mother liquor;

[0100] (3) The precipitation mother liquor obtained in step (2) was added to a 100 mL hydrothermal synthesis reactor with a polytetrafluoroethylene inner lining, and placed in a forced-air drying oven for static aging. The aging temperature was 150 °C and the aging time was 16 h to form a precipitate;

[0101] (4) After the product obtained in step (3) was naturally cooled to room temperature, it was centrifuged, and the centrifuged precipitate was washed with deionized water until the pH was 7.5, then dried at 80 °C for 14 h, and then calcined at 500 °C for 3 h to obtain a magnesium-aluminum modified indium oxide catalyst (the contents of its components are shown in Table 1). It was tableted and sieved to 40-60 mesh, and the indium oxide in the obtained catalyst had a cubic structure;

[0102] (5) The reaction of hydrogenation of carbon dioxide to methanol was carried out in a stainless-steel reactor with an inner diameter of 8 mm. The magnesium-aluminum modified indium oxide catalyst prepared in step (4) was used as the reaction catalyst, and the reaction conditions were as follows: the reaction pressure was 4.0 MPa, the reaction temperature was 240 °C, the volume space velocity of the raw materials (carbon dioxide and hydrogen) was 15000 -1 、H 2 / CO 2 The molar ratio was 6. After the reaction, the liquid-phase product was collected in an ice-water bath, and the product composition was analyzed by gas chromatography. The evaluation results are shown in Table 2.

[0103] Example 6

[0104] According to the method of Example 3, the difference is that step (3) is replaced by:

[0105] The precipitation mother liquor obtained in step (2) was added to a 100 mL hydrothermal synthesis reactor with a polytetrafluoroethylene inner lining, and placed in a forced-air drying oven for static aging. The aging temperature was 200 °C and the aging time was 15 h to form a precipitate.

[0106] Example 7

[0107] The method of Example 3 is followed, except that the doping component is prepared by adding 9.0 g of aluminum nitrate and 3.0 g of magnesium nitrate to 500 mL of water to prepare a salt solution, adding 6.5 g of sodium carbonate to 500 mL of deionized water to prepare a precipitant solution, subjecting the two solutions to co-current precipitation, controlling the pH to about 7.5, stirring the mixed solution for 1 h, allowing it to stand for aging for 2 h, washing it three times by centrifugation with deionized water, drying it at 60° C. for 48 h, and finally calcining it at 800° C. for 3 h to obtain the doping component.

[0108] Example 8

[0109] The method of Example 3 is followed, except that the amount of magnesium nitrate in step (1) is replaced by 8.6 g.

[0110] Comparative Example 1

[0111] (1) 7.6 g In(NO 3 ) 3 ·4H 2 O is added to a mixture of 40 mL of anhydrous ethanol and 24 mL of deionized water to obtain a solution containing a metal indium salt, 8 g of urea is added to a mixture of 40 mL of anhydrous ethanol and 10 mL of deionized water to obtain a precipitant solution, the precipitant solution is added dropwise to the solution containing the metal indium salt at 30°C, and the mixture is stirred at a speed of 150 rpm for 6 hours to obtain a precipitation mother solution;

[0112] (2) adding the precipitation mother solution obtained in step (1) into a 100 mL polytetrafluoroethylene-lined hydrothermal synthesis reactor, placing the reactor in a forced air drying oven for aging at a temperature of 120° C. for 20 h to form a precipitate;

[0113] (3) The product obtained in step (2) was naturally cooled to room temperature and then centrifuged, the centrifugal precipitate was washed with deionized water until the pH value was 7, and then dried at 60° C. for 20 h, and then calcined at 350° C. for 3 h to obtain an indium oxide catalyst, which was pressed into tablets and sieved into 40-60 mesh;

[0114] (4) In a stainless steel reactor with an inner diameter of 8 mm, the indium oxide catalyst prepared in step (3) was used as a reaction catalyst. The reaction conditions were as follows: reaction pressure of 3.0 MPa, reaction temperature of 280° C., volume space velocity of raw materials (carbon dioxide and hydrogen) of 9000 h / min -1 , H 2 / CO 2 The molar ratio was 4. After the reaction was completed, the liquid product was collected in an ice-water bath. The product composition was analyzed by gas chromatography. The evaluation results are shown in Table 1.

[0115] Comparative Example 2

[0116] (1) 4.1 g of surfactant P123 and 80 ml of anhydrous ethanol were mixed and dissolved under ultrasound, and then 6.3 ml of concentrated nitric acid was added. After clarification, 8.1 g of aluminum isopropoxide was added, stirred and mixed for 5 h, dried at 60 ° C. for 48 h, and finally calcined at 800 ° C. for 3 h to obtain a doping component;

[0117] (2) 15.34 g In(NO 3 ) 3 ·4H 2 O is added to a mixture of 80 mL of anhydrous ethanol and 48 mL of deionized water to obtain a solution containing a metal indium salt, 16 g of urea is added to a mixture of 80 mL of anhydrous ethanol and 20 mL of deionized water to obtain a precipitant solution, the precipitant solution is added to the solution containing a metal indium salt at 30° C., and then 2 g of the doping component obtained in step (1) is added, and the mixture is stirred at a speed of 150 rpm for 6 h to obtain a precipitation mother solution;

[0118] (3) adding the precipitation mother solution obtained in step (2) into a 100 mL polytetrafluoroethylene-lined hydrothermal synthesis reactor, placing the reactor in a forced air drying oven for aging at 120° C. for 20 h to form a precipitate;

[0119] (4) The product obtained in step (3) was naturally cooled to room temperature and then centrifuged, and the centrifugal precipitate was washed with deionized water until the pH value was 7, and then dried at 60° C. for 20 h, and then calcined at 350° C. for 3 h to obtain a magnesium aluminum modified indium oxide catalyst, which was pressed into tablets and sieved into 40-60 mesh;

[0120] (5) In a stainless steel reactor with an inner diameter of 8 mm, the carbon dioxide was hydrogenated to produce methanol, and the magnesium-aluminum modified indium oxide catalyst prepared in step (4) was used as the reaction catalyst. The reaction conditions were as follows: the reaction pressure was 3.0 MPa, the reaction temperature was 280° C., and the volume space velocity of the raw materials (carbon dioxide and hydrogen) was 9000 h -1 , H 2 / CO 2 The molar ratio was 4. After the reaction was completed, the liquid product was collected in an ice-water bath. The product composition was analyzed by gas chromatography. The evaluation results are shown in Table 1.

[0121] Comparative Example 3

[0122] (1) 4.1 g of surfactant P123 and 80 ml of anhydrous ethanol were mixed and dissolved under ultrasound, and then 6.3 mL of concentrated nitric acid was added. After clarification, 4.9 g of aluminum isopropoxide and 3.0 g of magnesium nitrate were added, and the mixture was stirred for 5 h, dried at 60° C. for 48 h, and finally calcined at 800° C. for 3 h to obtain a doping component;

[0123] (2) Weigh 5.37 g In(NO 3 )3 ·4H 2 Dissolve 10 g of O in 100 g of water, then pour it into 1 g of the doped component obtained in step (1), and stir well at a rotation speed of 150 rpm for 1 h. Evaporate the water to dryness using a rotary evaporator, then place it in an oven at 120 °C and dry for 12 h, and then calcine it at 350 °C for 3 h to obtain the catalyst. Press and sieve it to 40 - 60 mesh;

[0124] (3) Carry out the reaction of hydrogenation of carbon dioxide to methanol in a stainless steel reactor with an inner diameter of 8 mm, using the catalyst prepared in step (2) as the reaction catalyst. The reaction conditions are as follows: the reaction pressure is 3.0 MPa, the reaction temperature is 280 °C, and the volume space velocity of the raw materials (carbon dioxide and hydrogen) is 9000 h -1 、H 2 / CO 2 The molar ratio is 4. After the reaction, collect the liquid-phase product in an ice-water bath, and analyze the product composition by gas chromatography. The evaluation results are shown in Table 1.

[0125] Comparative Example 4

[0126] According to the method of Example 3, the difference is that in step (1), the amount of aluminum isopropoxide is replaced with 5.0 g and the amount of magnesium nitrate is replaced with 2 g, and in step (2), the amount of the doped component is replaced with 0.3 g.

[0127] Table 1

[0128]

[0129]

[0130] Note: The content of each component in Table 1 is the mass percentage content

[0131] Table 2

[0132]

[0133] It can be seen from the results in Table 1 that when the magnesium-aluminum modified indium oxide catalyst prepared by the method provided by the present invention in Examples 1 - 8 is used for the reaction of hydrogenation of carbon dioxide to methanol, compared with the catalysts prepared in Comparative Examples 1 - 4, it has significantly better catalytic performance, and high reaction activity and high selectivity of the target product.

[0134] 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 technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A magnesium-aluminum modified indium oxide catalyst, characterized in that, the catalyst comprises an active component and a doping component, the active component is indium oxide with a cubic structure, and the doping component is a mixture of magnesium oxide and aluminum oxide; wherein, the content of the active component accounts for 40-85% of the total mass of the catalyst, and the doping component accounts for 15-60% of the total mass of the catalyst; the doping component has an ordered mesoporous structure; the mass ratio of the active component to the doping component is 1-6:1; magnesium oxide accounts for 3-24% of the total mass of the catalyst, and aluminum oxide accounts for 12-51% of the total mass of the catalyst; A method for preparing a magnesium-aluminum modified indium oxide catalyst, the method comprising the following steps: (1) Mix a solution containing a metal indium salt, a precipitant solution and a doping component to obtain a mother liquor of the precipitate; (2) Age the mother liquor of the precipitate to form a precipitate; (3) Separate the solid and liquid of the product obtained in step (2), and then perform drying and calcination; the doping component is a mixture of magnesium oxide and aluminum oxide.

2. The catalyst according to claim 1, wherein, the content of the active component accounts for 65-75% of the total mass of the catalyst, and the doping component accounts for 25-35% of the total mass of the catalyst.

3. The catalyst according to claim 1, wherein, the mass ratio of the active component to the doping component is 1-3:

1.

4. The catalyst according to any one of claims 1-3, wherein, magnesium oxide accounts for 3.75-10.5% of the total mass of the catalyst; aluminum oxide accounts for 17.5-29.75% of the total mass of the catalyst.

5. A method for preparing a magnesium-aluminum modified indium oxide catalyst according to any one of claims 1-4, the method comprises the following steps: (1) Mix a solution containing a metal indium salt, a precipitant solution and a doping component to obtain a mother liquor of the precipitate; (2) Age the mother liquor of the precipitate to form a precipitate; (3) Separate the solid and liquid of the product obtained in step (2), and then perform drying and calcination; the doping component is a mixture of magnesium oxide and aluminum oxide.

6. The method according to claim 5, wherein, the dosages of the metal indium salt and the doping component are such that in the prepared catalyst, the content of indium oxide accounts for 40-85% of the total mass of the catalyst, and the doping component accounts for 15-60% of the total mass of the catalyst.

7. The method according to claim 6, wherein, the dosages of the metal indium salt and the doping component are such that in the prepared catalyst, the content of indium oxide accounts for 65-75% of the total mass of the catalyst, and the doping component accounts for 25-35% of the total mass of the catalyst.

8. The method according to claim 5, wherein, the mass ratio of the metal indium salt and the doping component in terms of oxides is 1-6:

1.

9. The method according to claim 8, wherein, the mass ratio of the metal indium salt and the doping component in terms of oxides is 1-3:

1.

10. The method according to claim 5, wherein, in step (1), the solvents in the solution containing the metal indium salt and the precipitant solution are independently organic solvents and / or water.

11. The method according to claim 10, wherein, In step (1), the solvents in the solution containing indium metal salt and the precipitant solution are organic solvents and water, and the organic solvents are selected from at least one of ethanol, methanol, isopropanol, ethylene glycol, triethylene glycol, and N,N-dimethylacetamide.

12. According to the method described in claim 5, wherein, the concentration of the solution containing indium metal salt is 0.1 - 0.8 mol / L.

13. According to the method described in claim 5, wherein, the concentration of the precipitant solution is 1 - 2 mol / L.

14. According to the method described in claim 5, wherein, the precipitant is urea.

15. According to the method described in claim 5, wherein, the mixing is carried out under stirring conditions.

16. According to the method described in claim 15, wherein, the mixing is carried out for 1 - 10 h under stirring conditions.

17. According to the method described in claim 5, wherein, the mixing includes first mixing the solution containing indium metal salt and the precipitant solution, and then adding the doping component.

18. According to the method described in claim 5, wherein, the solvent evaporation-induced self-assembly method is used to prepare the doping component.

19. According to the method described in claim 18, wherein, the preparation method of the doping component includes: in the presence of a surfactant and in the presence of a solvent, mixing an acid, an aluminum precursor, and a magnesium precursor, and then drying and calcining.

20. According to the method described in claim 19, wherein, the dosages of the aluminum precursor and the magnesium precursor are such that in the prepared catalyst, magnesium oxide accounts for 3 - 24% of the total mass of the catalyst; aluminum oxide accounts for 12 - 51% of the total mass of the catalyst.

21. According to the method described in claim 20, wherein, the dosages of the aluminum precursor and the magnesium precursor are such that in the prepared catalyst, magnesium oxide accounts for 3.75 - 10.5% of the total mass of the catalyst; aluminum oxide accounts for 17.5 - 29.75% of the total mass of the catalyst.

22. According to the method described in claim 19, wherein, the surfactant is selected from at least one of P123, CTAB, malic acid, sodium 2-ethylhexane sulfosuccinate, and nonylphenol polyoxyethylene ether; the solvent is selected from at least one of ethanol, methanol, isopropanol, ethylene glycol, triethylene glycol, and N,N-dimethylacetamide; the acid is at least one of nitric acid, hydrochloric acid, and phosphoric acid; the aluminum precursor is at least one of aluminum isopropoxide, aluminum nitrate, aluminum chloride, and aluminum sulfate.

23. According to the method described in claim 19, wherein, the mixing time is 3 - 9 h.

24. According to the method described in claim 23, wherein, the mixing is carried out under stirring conditions.

25. According to the method described in claim 19, wherein, the calcination conditions include: the temperature is 600 - 1200 °C, and the time is 3 - 6 h.

26. According to the method described in claim 5, wherein, the aging conditions in step (2) include: the temperature is 80 - 180 °C, and the time is 12 - 22 h.

27. According to the method described in any one of claims 5 - 26, wherein, the method further includes washing the product obtained in step (2).

28. The method according to claim 26, wherein, the pH value of the product obtained by washing to step (2) is between 6 and 8.

29. The method according to any one of claims 5-26, wherein, the conditions of the calcination in step (3) include: the temperature is 300-500 °C and the time is 3-6 h.

30. A method for preparing methanol by hydrogenating carbon dioxide, the method comprises: under the conditions of hydrogenating carbon dioxide, contacting carbon dioxide and hydrogen with a catalyst; the catalyst is the magnesium-aluminum modified indium oxide catalyst according to any one of claims 1-4 or the magnesium-aluminum modified indium oxide catalyst prepared by the preparation method according to any one of claims 5-29.

31. The method according to claim 30, wherein, The carbon dioxide hydrogenation conditions include: the reaction pressure is between 1.0 - 5.0 MPa, the reaction temperature is between 200 - 400 °C, the raw material volume space velocity is between 4500 - 18000 h -1 between, H 2 / CO 2 The molar ratio is between 1 - 6.

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