Magnesium-aluminum doped 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 doped indium oxide catalyst, a preparation method and an application thereof, and a method for hydrogenating carbon dioxide to prepare methanol. The catalyst comprises an active component and a carrier. The active component is indium oxide with a hexagonal structure, and the carrier comprises magnesium oxide and aluminum oxide. Based on the total amount of the catalyst, the content of indium oxide is 50-85% by weight, and the content of the carrier is 15-50% by weight. The magnesium-aluminum doped indium oxide catalyst has better catalytic effect and can effectively improve the conversion rate of carbon dioxide and the selectivity of methanol.

Description

Technical Field

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

[0002] As an important raw material for chemicals and a substitute for fossil fuels, methanol can be prepared by reacting CO 2 with H from renewable energy 2 , which can not only solve greenhouse gas control but also be an effective way to replace fossil fuels. Therefore, the catalytic conversion of carbon dioxide into methanol products has received more attention.

[0003] Due to the stable chemical properties and difficult activation of CO 2 , the conversion rate of this reaction is generally low. And the formation of methanol is an exothermic reaction. Thermodynamically, low temperature is favorable for methanol production but not for the activation of carbon dioxide. Therefore, it is necessary to select an appropriate reaction temperature and design an efficient catalyst.

[0004] Currently, the catalysts widely studied for methanol synthesis include modified copper-based catalysts, noble metal catalysts, and zinc oxide catalysts. However, in the modified statistical catalytic system, the high activity of the side reaction reverse water gas shift (RWGS) and the characteristics such as H 2 O-induced sintering of the active phase and poor stability limit its further application. In the noble metal catalytic system and the zinc oxide catalytic system, the high cost of noble metals and the low active sites and easy migration of zinc oxide also limit the further application of such catalysts in the field of carbon dioxide hydrogenation to some extent. In 2 O 3 has moderate CO 2 and CO adsorption capacities, shows significantly better methanol selectivity than Cu, Co, and noble metal catalysts, and higher catalytic activity than ZnO catalysts, thus attracting extensive attention of scientific researchers. However, the catalytic effect of In 2 O 3 catalysts in the prior art still needs to be further improved. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problem that the catalytic effect of In 2 O 3 catalysts in the prior art needs to be further improved, and to provide a magnesium-aluminum doped indium oxide catalyst, a preparation method and an application thereof, and a method for preparing methanol by hydrogenating carbon dioxide. The magnesium-aluminum doped indium oxide catalyst has a better catalytic effect and can effectively improve methanol selectivity.

[0006] To achieve the above object, on the one hand, the present invention provides a magnesium-aluminum doped indium oxide catalyst, which catalyst comprises an active component and a carrier. The active component is indium oxide having a hexagonal structure, and the carrier comprises magnesium oxide and aluminum oxide. Based on the total amount of the catalyst, the content of indium oxide is 50-85% by weight, and the content of the carrier is 15-50% by weight.

[0007] Preferably, based on the total amount of the catalyst, the content of magnesium oxide is 3-15% by weight; the weight ratio of aluminum oxide to magnesium oxide is 2.5-9.5:1.

[0008] Preferably, the carrier has an ordered mesoporous structure.

[0009] On the second aspect, the present invention provides a method for preparing a magnesium-aluminum doped indium oxide catalyst, which method comprises the following steps:

[0010] (1) Mix a magnesium-aluminum doped carrier containing aluminum oxide and magnesium oxide with indium oxide having a hexagonal structure, and then optionally grind them;

[0011] (2) Calcinate the product obtained in step (1).

[0012] Based on the total amount of the magnesium-aluminum doped carrier and indium oxide, the content of indium oxide is 50-85% by weight, and the content of the magnesium-aluminum doped carrier is 15-50% by weight.

[0013] Preferably, the preparation of the indium oxide comprises the following steps:

[0014] (a) Mix a solution containing a metal indium precursor with a precipitant solution to obtain a precipitation mother liquor;

[0015] (b) Age the precipitation mother liquor to form a precipitate;

[0016] (c) Perform solid-liquid separation on the product obtained in step (b), and then perform drying and calcination.

[0017] Preferably, the method for preparing the magnesium-aluminum doped carrier comprises: mixing an acid, an aluminum precursor and a magnesium precursor in the presence of a surfactant and in the presence of a solvent, and then performing drying and calcination.

[0018] On the third aspect, the present invention provides an application of the magnesium-aluminum doped indium oxide catalyst in the reaction of preparing methanol from carbon dioxide, wherein the magnesium-aluminum doped indium oxide catalyst is the magnesium-aluminum doped indium oxide catalyst described in the first aspect above or the magnesium-aluminum doped indium oxide catalyst prepared by the preparation method described in the second aspect above.

[0019] The fourth aspect of the present invention provides a method for preparing methanol by hydrogenating carbon dioxide, which method comprises: contacting carbon dioxide and hydrogen under the conditions of hydrogenating carbon dioxide in the presence of a catalyst; the catalyst is the indium oxide doped with magnesium and aluminum described in the first aspect above or the indium oxide doped with magnesium and aluminum prepared by the preparation method described in the second aspect above.

[0020] The indium oxide doped with magnesium and aluminum of the present invention uses indium oxide with a hexagonal structure as the active component and combines magnesium oxide and aluminum oxide as the carrier, which can effectively promote the occurrence of the methanol catalytic reaction. It can be seen from the example part that the indium oxide doped with magnesium and aluminum of the present invention has high catalytic activity and selectivity, and can improve the conversion rate of carbon dioxide and the content of methanol in the product. For example, under the conditions of 3 MPa and 10000 h -1 conditions, the selectivity of this catalyst for catalytically preparing methanol can reach 78%; under the conditions of 5 MPa and 6750 h -1 conditions, the selectivity of this catalyst for catalytically preparing methanol can reach 98%. Moreover, this catalyst can still meet a relatively high carbon dioxide conversion rate and methanol selectivity during the long-term operation of the reaction, and the catalyst deactivation rate is relatively low.

[0021] Other features and advantages of the present invention will be described in detail in the subsequent specific embodiment part. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the XRD pattern of the hexagonal indium oxide prepared in Example 1 of the present invention;

[0023] Figure 2 is the XRD pattern of the ordered mesoporous doped carrier prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] The endpoints and any values disclosed in this article for ranges are not limited to the exact range or value, and 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 and a single point value, and between single 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 in this article.

[0025] As described above, the first aspect of the present invention provides an indium oxide doped with magnesium and aluminum catalyst, which catalyst comprises an active component and a carrier, the active component is indium oxide with a hexagonal structure, and the carrier comprises magnesium oxide and aluminum oxide. Based on the total amount of the catalyst, the content of indium oxide is 50-85% by weight, and the content of the carrier is 15-50% by weight.

[0026] The content of each component in the catalyst of the present invention can be obtained by X-ray fluorescence spectroscopy (XRF) test. The hexagonal structure of the indium oxide is characterized by XRD.

[0027] In the research process, the inventors of the present invention found that when the magnesium-aluminum doped indium oxide catalyst as described above is applied to the reaction of catalytic hydrogenation of carbon dioxide to prepare methanol, it can effectively improve the catalytic efficiency of the catalyst, increase the conversion rate of carbon dioxide and the selectivity of methanol in the catalytic reaction, and promote the formation of methanol. Moreover, the catalyst inactivation rate is relatively low and the reaction stability is good.

[0028] In order to further exert the synergistic effect between the active component and the carrier and improve the catalytic performance of the catalyst, preferably, based on the total amount of the catalyst, the content of indium oxide is 60-80% by weight, and the content of the carrier is 20-40% by weight.

[0029] In the carrier of the present invention, magnesium oxide and aluminum oxide can be mixed in any proportion. Preferably, based on the total amount of the catalyst, the content of magnesium oxide is 3-15% by weight; the weight ratio of aluminum oxide to magnesium oxide is 2.5-9.5:1. Adopting this preferred embodiment can further exert the synergistic effect between the carrier and the active component, thereby further increasing the conversion rate of carbon dioxide and the selectivity of methanol.

[0030] In order to further exert the synergistic effect between the carrier and the active component, preferably, based on the total amount of the catalyst, the content of magnesium oxide is 3-8% by weight; the weight ratio of aluminum oxide to magnesium oxide is 2.6-4.5:1.

[0031] Preferably, the mass ratio of the active component to the carrier is 1-6:1. Under this ratio condition, the synergistic effect between the active component and the carrier can be further exerted, thereby increasing the conversion rate of carbon dioxide and the selectivity of methanol. More preferably, the mass ratio of the active component to the carrier is 1-3:1.

[0032] The carrier mainly needs to meet the above limitations to achieve the purpose of the present invention. In order to further improve the catalytic performance of the catalyst. Preferably, the carrier has an ordered mesoporous structure.

[0033] The ordered mesoporous structure of the carrier can be determined by small-angle XRD test.

[0034] As described above, the second aspect of the present invention provides a method for preparing a magnesium-aluminum doped indium oxide catalyst, which method includes the following steps:

[0035] (1) Mix the magnesium-aluminum doped carrier containing aluminum oxide and magnesium oxide with indium oxide having a hexagonal structure, and then optionally grind them into powder;

[0036] (2) Calcinate the product obtained in step (1).

[0037] Based on the total amount of the magnesium-aluminum doped support and indium oxide, the content of indium oxide is 50-85 wt%, and the content of the magnesium-aluminum doped support is 15-50 wt%.

[0038] In the preparation method of the present invention, the above mixing can be stirring mixing, ultrasonic mixing or other feasible mixing methods. Stirring mixing can be magnetic stirring, mechanical stirring or manual stirring, etc. The conditions of ultrasonic mixing and stirring conditions can be determined by those skilled in the art according to the actual situation. After mixing the magnesium-aluminum doped support containing alumina and magnesia and indium oxide, the obtained product after mixing can be optionally pulverized, or not pulverized. The pulverization method can be pulverization by a pulverizer or pulverization by grinding. Preferably, after mixing the magnesium-aluminum doped support containing alumina and magnesia and indium oxide, it is ground in a ball mill. Preferably, the rotation speed of the ball mill is set to 200-800 rpm, and the ball milling time is 5-30 h.

[0039] According to the present invention, preferably, the conditions of the calcination include: the temperature is 300-500 °C, and the time is 1-5 h.

[0040] In order to further exert the synergistic effect between indium oxide and the magnesium-aluminum doped support and improve the conversion rate of carbon dioxide and the selectivity of methanol, preferably, based on the total amount of the magnesium-aluminum doped support and indium oxide, the content of indium oxide is 60-80 wt%, and the content of the magnesium-aluminum doped support is 20-40 wt%.

[0041] In the support of the present invention, magnesia and alumina can be mixed in any proportion. Preferably, based on the total amount of the magnesium-aluminum doped support and indium oxide, the content of magnesia is 3-15 wt%; the weight ratio of alumina to magnesia is 2.5-9.5:1. It can further exert the synergistic effect between the magnesium-aluminum doped support and indium oxide, thereby further improving the conversion rate of carbon dioxide and the selectivity of methanol.

[0042] In order to further exert the synergistic effect between the magnesium-aluminum doped support and indium oxide, preferably, based on the total amount of the magnesium-aluminum doped support and indium oxide, the content of magnesia is 3-8 wt%; the weight ratio of alumina to magnesia is 2.6-4.5:1.

[0043] Preferably, the mass ratio of indium oxide to the magnesium-aluminum doped support is 1-6:1. Under this ratio condition, the synergistic effect between indium oxide and the magnesium-aluminum doped support can be further exerted, thereby improving the conversion rate of carbon dioxide and the selectivity of methanol. Further preferably, the mass ratio of indium oxide to the magnesium-aluminum doped support is 1-3:1.

[0044] In the present invention, preferably, the indium oxide is prepared by a precipitation method. The indium oxide with a hexagonal structure prepared by the precipitation method has a better catalytic effect and can effectively improve the conversion rate of carbon dioxide and the selectivity of methanol.

[0045] Further preferably, the preparation of the indium oxide comprises the following steps:

[0046] (a) Mixing a solution containing a metal indium precursor with a precipitant solution to obtain a precipitation mother liquor;

[0047] (b) Aging the precipitation mother liquor to form a precipitate;

[0048] (c) Separating the solid and liquid of the product obtained in step (b), and then drying and calcining.

[0049] According to the present invention, the metal indium precursor may be a soluble metal indium salt containing indium ions, such as In(NO 3 ) 3 , InCl 3 and In 2 (SO 4 ) 3 or at least one of them, preferably at least one of In(NO 3 ) 3 and InCl 3 . The precipitant is a substance in the prior art that can cause the metal indium precursor to precipitate slowly. Preferably, the precipitant is urea.

[0050] The mixing in step (a) can be carried out by any feasible method disclosed in the prior art. Preferably, in step (a), the method of mixing the solution containing the metal indium precursor with the precipitant solution is: dropping the precipitant solution drop by drop into the solution containing the metal indium precursor, and continuously stirring during the dropping process and after the dropping is completed. Preferably, the stirring time is 1 - 10 h. This preferred embodiment can make the metal indium precursor and the precipitant fully contact, thereby improving the precipitation effect.

[0051] The method of solid - liquid separation can be the filtration separation method commonly used in the art, such as filtration or centrifugal separation. Preferably, the centrifugal separation method is adopted, and the centrifugal conditions include: the rotation speed is 5000 - 10000 rpm, and the time is 5 - 10 min.

[0052] The aging reaction in step (b) is a hydrothermal reaction. Preferably, the aging reaction is carried out under closed conditions. As a specific embodiment of the present invention, in step (b), the precipitation mother liquor is placed in a hydrothermal reactor, and the hydrothermal reactor is placed in an oven to age the precipitation mother liquor. Preferably, the aging conditions include: a temperature of 80-180°C and a time of 12-22 h. Further preferably, the aging conditions include: a temperature of 120-160°C and a time of 18-20 h. Aging under this temperature condition can further improve the catalytic effect of the obtained indium oxide.

[0053] According to the present invention, the solvents in the solution containing the metal indium precursor and the precipitant solution are each independently an organic solvent and / or water, preferably an organic solvent and water. The mixing ratio of the organic solvent and water can be determined by those skilled in the art according to the actual situation so as to form a solution containing the metal indium precursor and a precipitant solution.

[0054] The organic solvent is preferably selected from at least one of methanol, ethanol, isopropanol, ethylene glycol, triethylene glycol, and N,N-dimethylacetamide.

[0055] The concentration of the solution of the metal indium precursor and the concentration of the precipitant solution can be determined by those skilled in the art according to the actual situation. Under preferred conditions, the concentration of the solution containing the metal indium precursor is 0.1-1 mol / L, and the concentration of the precipitant solution is 1-3 mol / L.

[0056] According to the present invention, the dosage ratio of the metal indium precursor and the precipitant is such that the metal indium precursor can be converted into indium oxide precipitate.

[0057] Preferably, the method further includes washing the product obtained in step (b), preferably washing until the pH value of the product obtained in step (b) is between 6 and 8. This can improve the purity of the obtained product.

[0058] According to the present invention, the conditions for the calcination in step (c) include: a temperature of 300-500°C and a time of 3-6 h. Calcination under this temperature condition can further improve the catalytic effect of the obtained indium oxide. The conditions for the drying can be: a temperature of 50-100°C and a time of 12-24 h.

[0059] In order to further improve the loading effect of the support on indium oxide and thus further exert the synergistic effect between indium oxide and the magnesium-aluminum doped support, preferably, a solvent evaporation-induced self-assembly method is used to prepare the magnesium-aluminum doped support. The magnesium-aluminum doped support prepared by the solvent evaporation-induced self-assembly method has an ordered mesoporous structure, which can further improve the loading effect on indium oxide and thus improve the catalytic performance of the obtained catalyst.

[0060] Further preferably, the method for preparing the magnesium-aluminum doped support 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.

[0061] According to the present invention, preferably, the surfactant is selected from at least one of P123, cetyltrimethylammonium bromide (CTAB), malic acid, sodium 2-ethylhexyl sulfosuccinate, and nonylphenol polyoxyethylene ether.

[0062] According to the present invention, preferably, the solvent is selected from at least one of methanol, ethanol, isopropanol, ethylene glycol, triethylene glycol, and N,N-dimethylacetamide.

[0063] According to the present invention, preferably, the acid is at least one of nitric acid, hydrochloric acid, and phosphoric acid.

[0064] According to the present invention, preferably, the aluminum precursor is at least one of aluminum isopropoxide, aluminum nitrate, aluminum chloride, and aluminum sulfate.

[0065] According to the present invention, preferably, the magnesium precursor is magnesium nitrate and / or magnesium chloride.

[0066] Preferably, the molar ratio of the organic solvent, the surfactant, the acid, and the aluminum precursor is 10-80:0.01-0.05:1-6:1. More preferably, it is 20-50:0.01-0.03:1.5-3:1.

[0067] Research has shown that under the above conditions, the magnesium-aluminum doped support has a higher loading rate for indium oxide, thereby effectively improving the catalytic effect of the magnesium-aluminum doped indium oxide catalyst.

[0068] According to the present invention, preferably, the mixing time of the acid, the aluminum precursor, and the magnesium precursor is 3-9 h, which can achieve a better mixing effect. Preferably, the mixing is carried out under stirring conditions. The drying conditions can be: the temperature is 30-120 °C, and the time is 10-60 h.

[0069] Preferably, the calcination conditions include: the temperature is 600-1200 °C, and the time is 3-6 h. Research has shown that the magnesium-aluminum doped support obtained under these calcination conditions has a better loading effect.

[0070] As mentioned above, the third aspect of the present invention provides the application of the magnesium-aluminum doped indium oxide catalyst described in the first aspect or the magnesium-aluminum doped indium oxide catalyst prepared by the preparation method described in the second aspect in the reaction of hydrogenating carbon dioxide to prepare methanol. Applying the catalyst provided by the present invention to the reaction of hydrogenating carbon dioxide to prepare methanol can significantly improve the selectivity of methanol.

[0071] As described above, the fourth aspect of the present invention provides a method for preparing methanol by hydrogenating carbon dioxide, which includes: contacting carbon dioxide and hydrogen under the condition of hydrogenating carbon dioxide in the presence of a catalyst; the catalyst is the magnesium-aluminum doped indium oxide catalyst described in the first aspect or the magnesium-aluminum doped indium oxide catalyst prepared by the preparation method of the second aspect.

[0072] According to the present invention, 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 raw material volume space velocity is between 4500 - 18000 h -1 between, H 2 / CO 2 The molar ratio is between 1 - 6; more preferably, the carbon dioxide hydrogenation conditions include: the reaction pressure is between 3.0 - 5.0 MPa, the reaction temperature is between 240 - 280 °C, the raw material volume space velocity is between 8000 - 12000 h -1 between, H 2 / CO 2 The molar ratio is between 3 - 6.

[0073] According to a particularly preferred embodiment of the present invention, a preparation method of a magnesium-aluminum doped indium oxide catalyst is provided, which includes the following steps:

[0074] (1) Mix the magnesium-aluminum doped carrier containing alumina and magnesia with indium oxide, place it in a ball mill for grinding, set the ball mill rotation speed to 200 - 800 rpm, and the ball milling time to 5 - 30 h;

[0075] Among them, the preparation method of indium oxide includes the following steps:

[0076] (a) Dropwise add the precipitant solution to the solution containing the metal indium precursor, and continuously stir during the dropping process and after the dropping is completed (the total stirring time is 1 - 10 h) to obtain a precipitation mother liquor; the metal indium precursor is at least one of In(NO 3 ) 3 and InCl 3 , the precipitant is urea, the concentration of the solution containing the metal indium precursor is 0.1 - 1 mol / L, the concentration of the precipitant solution is 1 - 3 mol / L, the solvents in the solution containing the metal indium precursor and the precipitant solution are organic solvents and water, and the organic solvent is selected from at least one of methanol, ethanol, isopropanol, ethylene glycol, triethylene glycol, and N,N-dimethylacetamide;

[0077] (b) Age the precipitation mother liquor (temperature is 80 - 160 °C, time is 12 - 22 h) to form a precipitate;

[0078] (c) Separate the solid and liquid of the product obtained in step (b), and then perform drying (temperature: 50 - 80 °C, time: 12 - 24 h) and calcination (temperature: 300 - 500 °C, time: 3 - 6 h);

[0079] The preparation method of the magnesium-aluminum doped support includes the following steps:

[0080] In the presence of a surfactant and in the presence of a solvent, mix an acid, an aluminum precursor, and a magnesium precursor, and then perform drying (temperature: 50 - 70 °C, time: 42 - 54 h) and calcination (temperature: 600 - 1200 °C, time: 3 - 6 h); 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; the magnesium precursor is selected from magnesium nitrate and / or magnesium chloride, and the molar ratio of the organic solvent, the surfactant, the acid, and the aluminum precursor is 20 - 50:0.01 - 0.03:1.5 - 3:1;

[0081] (2) Calcinate the product obtained in step (1) (temperature: 300 - 500 °C, time: 1 - 5 h);

[0082] Based on the total amount of the magnesium-aluminum doped support and indium oxide, the content of indium oxide is 60 - 80 wt%, the content of magnesium oxide is 3 - 8 wt%, the weight ratio of aluminum oxide to magnesium oxide is 2.6 - 4.5:1, and the mass ratio of indium oxide to the magnesium-aluminum doped support is 1 - 3:1.

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

[0084] In the following examples, the gas chromatograph was purchased from Agilent Technologies (China) Co., Ltd.; P123 is poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol), a commercially available product with the company brand of sigma-aldrich; absolute ethanol, urea, and nitric acid were purchased from the National Pharmaceutical Group.

[0085] Example 1

[0086] (1) Take 15.4 g of In(NO 3 ) 3 ·4H 2O was added to a mixed solution of 80 mL of absolute ethanol and 48 mL of deionized water to dissolve and obtain a solution containing a metal indium precursor. 16 g of urea was added to a mixed solution of 80 mL of absolute ethanol and 20 mL of deionized water to dissolve and obtain a precipitant solution. At 25 °C, the precipitant solution was added to the solution containing the metal indium precursor to obtain a precipitation mother liquor, which was stirred thoroughly for 5 h. Then, the precipitation mother liquor was added to a hydrothermal synthesis reactor lined with 100 mL of polytetrafluoroethylene, and placed in a forced-air drying oven for static aging. The aging temperature was 120 °C and the aging time was 20 h. After the hydrothermal synthesis reactor naturally cooled to room temperature, the aging solution was centrifuged with deionized water until the pH was 7, then dried at 60 °C for 20 h, and then calcined at 350 °C for 3 h to obtain indium oxide. The obtained indium oxide was subjected to XRD ( Figure 1 ) characterization analysis. The results showed that indium oxide had a hexagonal structure.

[0087] (2) 4.2 g of P123 and 80 ml of absolute ethanol were mixed and dissolved under ultrasound; then 6.4 mL of concentrated nitric acid was added. After clarification, 5.0 g of aluminum isopropoxide and 3.1 g of magnesium nitrate were added; stirred for 5 h, dried at 60 °C for 48 h, and finally calcined at 800 °C for 3 h to obtain a doped support. The obtained doped support was subjected to XRD ( Figure 2 ) characterization analysis. The results showed that the doped support had an ordered mesoporous structure.

[0088] (3) 2 g of indium oxide and 1 g of the doped support were mixed and placed in a ball mill. The rotation speed of the ball mill was set at 300 rpm and the ball milling time was 5 h; then the solid powder obtained after ball milling was calcined at 350 °C for 3 h to obtain a magnesium-aluminum doped indium oxide catalyst, which was pressed and sieved into 40-60 mesh, and the composition is shown in Table 1.

[0089] (4) 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 reaction conditions were as follows: 3.0 MPa, 280 °C, 10000 h -1 , n(H 2 ) / n(CO 2 ) = 4. The liquid-phase products were collected in an ice-water bath, and the product composition was analyzed by gas chromatography. The evaluation results are shown in Table 2.

[0090] Example 2

[0091] (1) 7.3 g of In(NO 3 ) 3 ·4H 2O was added to a mixed solution of 40 mL of absolute ethanol and 25 mL of deionized water to dissolve and obtain a solution containing a metal indium precursor. 8 g of urea was added to a mixed solution of 60 mL of absolute ethanol and 20 mL of deionized water to dissolve and obtain a precipitant solution. At 30 °C, the precipitant solution was added to the solution containing the metal indium precursor to obtain a precipitation mother liquor, which was stirred thoroughly for 6 h. Then, the precipitation mother liquor was added to a 100 mL hydrothermal synthesis reactor lined with polytetrafluoroethylene and placed in a blast drying oven for static aging. The aging temperature was 140 °C and the aging time was 15 h. After the hydrothermal synthesis reactor naturally cooled to room temperature, the aging solution was centrifuged with deionized water until the pH was 7.5, then dried at 60 °C for 24 h, and then calcined at 300 °C for 3 h to obtain indium oxide. The obtained indium oxide was characterized by XRD analysis. The results showed that indium oxide had a hexagonal structure.

[0092] (2) 3.8 g of P123 and 80 ml of absolute ethanol were mixed and dissolved under ultrasonic waves; then 6.1 mL of concentrated nitric acid was added. After clarification, 9.5 g of aluminum isopropoxide and 1.6 g of magnesium nitrate were added; it was stirred for 5 h, dried at 60 °C for 48 h, and finally calcined at 800 °C for 3 h to obtain a doped support. The obtained doped support was characterized by XRD analysis. The results showed that the doped support had an ordered mesoporous structure.

[0093] (3) 1 g of indium oxide and 1 g of the doped support were mixed and placed in a ball mill. The rotation speed of the ball mill was set at 500 rpm and the ball milling time was 8 h; then the solid powder obtained after ball milling was calcined at 500 °C for 1 h to obtain a magnesium-aluminum doped indium oxide catalyst, which was pressed and sieved into 40 - 60 mesh, and the composition is shown in Table 1.

[0094] (4) The reaction for the hydrogenation of carbon dioxide to methanol was carried out in a stainless steel reactor with an inner diameter of 8 mm, and the reaction conditions were as follows: 5.0 MPa, 200 °C, 6750 h -1 、n(H 2 ) / n(CO 2 ) = 6. The liquid-phase products were collected in an ice-water bath, and the product composition was analyzed by gas chromatography. The evaluation results are shown in Table 2.

[0095] Example 3

[0096] (1) 8.5 g of In(NO 3 ) 3 ·4H 2O was added to a mixed solution of 50 mL of absolute ethanol and 25 mL of deionized water to dissolve and obtain a solution containing indium metal precursor. 8 g of urea was added to a mixed solution of 60 mL of absolute ethanol and 20 mL of deionized water to dissolve and obtain a precipitant solution. At 30 °C, the precipitant solution was added to the solution containing indium metal precursor to obtain a precipitation mother liquor, which was stirred thoroughly for 4 h. Then the precipitation mother liquor 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 120 °C and the aging time was 18 h. After the hydrothermal synthesis reactor naturally cooled to room temperature, the aging solution was centrifuged with deionized water until the pH was 8, then dried at 60 °C for 15 h, and then calcined at 380 °C for 3 h to obtain indium oxide. XRD characterization analysis was carried out on the obtained indium oxide, and the results showed that indium oxide had a hexagonal structure.

[0097] (2) 5.2 g of P123 and 100 ml of absolute ethanol were mixed and dissolved under ultrasonic waves; then 7.3 mL of concentrated nitric acid was added. After clarification, 10.7 g of aluminum isopropoxide and 3.8 g of magnesium nitrate were added; stirred for 5 h, dried at 60 °C for 48 h, and finally calcined at 800 °C for 3 h to obtain a doped support. XRD characterization analysis was carried out on the obtained doped support, and the results showed that the doped support had an ordered mesoporous structure.

[0098] (3) 1.8 g of indium oxide and 1.2 g of the doped support were mixed and then put into a ball mill. The rotation speed of the ball mill was set at 450 rpm and the ball milling time was 6 h; then the solid powder obtained after ball milling was calcined at 400 °C for 3 h to obtain a magnesium-aluminum doped indium oxide catalyst, which was pressed and sieved into 40 - 60 mesh, and the composition is shown in Table 1.

[0099] (4) The reaction of hydrogenation of carbon dioxide to prepare methanol was carried out in a stainless steel reactor with an inner diameter of 8 mm, and the reaction conditions were as follows: 5.0 MPa, 340 °C, 12000 h -1 、n(H 2 ) / n(CO 2 ) = 4. The liquid-phase products were collected in an ice-water bath, and the product composition was analyzed by gas chromatography. The evaluation results are shown in Table 2.

[0100] Example 4

[0101] (1) 10.3 g of In(NO 3 ) 3 ·4H 2O was added to a mixed solution of 80 mL of absolute ethanol and 40 mL of deionized water to dissolve and obtain a solution containing indium metal precursor. 9.2 g of urea was added to a mixed solution of 80 mL of absolute ethanol and 30 mL of deionized water to obtain a precipitant solution. The precipitant solution was added to the solution containing indium metal precursor at 30 °C to obtain a precipitation mother liquor, which was stirred thoroughly for 7 h. Then, the precipitation mother liquor was added to a 100 mL hydrothermal synthesis reactor lined with polytetrafluoroethylene and placed in a blast drying oven for static aging. The aging temperature was 130 °C and the aging time was 20 h. After the hydrothermal synthesis reactor naturally cooled to room temperature, the aging solution was centrifuged with deionized water until the pH was 6, then dried at 80 °C for 12 h, and then calcined at 450 °C for 3 h to obtain indium oxide. XRD characterization analysis was performed on the obtained indium oxide, and the results showed that indium oxide had a hexagonal structure.

[0102] (2) 4.7 g of P123 and 90 ml of absolute ethanol were mixed and dissolved under ultrasound; then 7.6 mL of concentrated nitric acid was added. After clarification, 8.5 g of aluminum isopropoxide and 4.8 g of magnesium nitrate were added; stirred for 5 h, dried at 60 °C for 48 h, and finally calcined at 800 °C for 3 h to obtain a doped support. XRD characterization analysis was performed on the obtained doped support, and the results showed that the doped support had an ordered mesoporous structure.

[0103] (3) 2.8 g of indium oxide and 1.2 g of doped support were mixed and placed in a ball mill. The rotation speed of the ball mill was set at 600 rpm and the ball milling time was 10 h; then the solid powder obtained after ball milling was calcined at 450 °C for 3 h to obtain a magnesium-aluminum doped indium oxide catalyst, which was pressed and sieved into 40-60 mesh, and the composition is shown in Table 1.

[0104] (4) The reaction of hydrogenation of carbon dioxide to prepare methanol was carried out in a stainless steel reactor with an inner diameter of 8 mm, and the reaction conditions were as follows: 1.0 MPa, 400 °C, 9000 h -1 、n(H 2 ) / n(CO 2 ) = 5. The liquid-phase products were collected in an ice-water bath, and the product composition was analyzed by gas chromatography. The evaluation results are shown in Table 2.

[0105] Example 5

[0106] (1) 5.4 g of In(NO 3 ) 3 ·4H 2In was added to a mixed solution of 40 mL of absolute ethanol and 20 mL of deionized water to dissolve and obtain a solution containing a metal indium precursor. 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 to the solution containing the metal indium precursor at 30 °C to obtain a precipitation mother liquor, which was stirred thoroughly for 6 h. Then, the precipitation mother liquor was added to a 100 mL hydrothermal synthesis reactor lined with polytetrafluoroethylene and placed in a blast drying oven for static aging. The aging temperature was 150 °C and the aging time was 16 h. After the hydrothermal synthesis reactor naturally cooled to room temperature, the mother solution was centrifuged with deionized water until the pH reached 7.5, then dried at 80 °C for 14 h, and then calcined at 500 °C for 3 h to obtain indium oxide. XRD characterization analysis was performed on the obtained indium oxide, and the results showed that indium oxide had a hexagonal structure.

[0107] (2) 7.3 g of P123 and 120 ml of absolute ethanol were mixed and dissolved under ultrasound; then 8.5 mL of concentrated nitric acid was added. After clarification, 7.1 g of aluminum isopropoxide and 4.3 g of magnesium nitrate were added; it was stirred for 5 h, dried at 60 °C for 48 h, and finally calcined at 800 °C for 3 h to obtain the doped support. XRD characterization analysis was performed on the obtained doped support, and the results showed that the doped support had an ordered mesoporous structure.

[0108] (3) 1.6 g of indium oxide and 0.4 g of the doped support were mixed and placed in a ball mill. The rotation speed of the ball mill was set at 350 rpm and the ball milling time was 15 h; then the solid powder obtained after ball milling was calcined at 550 °C for 3 h to obtain a magnesium-aluminum doped indium oxide catalyst, which was pressed and sieved into 40-60 mesh, and the composition is shown in Table 1.

[0109] (4) The reaction of hydrogenation of carbon dioxide to methanol was carried out in a stainless steel reactor with an inner diameter of 8 mm, and the reaction conditions were as follows: 4.0 MPa, 240 °C, 13000 h -1 、n(H 2 ) / n(CO 2 ) = 6. 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.

[0110] Example 6

[0111] According to the method of Example 1, the difference is that the preparation of the doped support in step (2) includes:

[0112] 4.2 g of P123 and 80 ml of absolute ethanol were mixed and dissolved under ultrasound; then 6.4 mL of concentrated nitric acid was added. After clarification, 8.5 g of aluminum isopropoxide and 0.6 g of magnesium nitrate were added; it was stirred for 5 h, dried at 60 °C for 48 h, and finally calcined at 800 °C for 3 h to obtain the doped support. XRD characterization analysis was performed on the obtained doped support, and the results showed that the doped support had an ordered mesoporous structure.

[0113] The composition is shown in Table 1, and the evaluation results are shown in Table 2.

[0114] Example 7

[0115] According to the method of Example 1, the difference is that the preparation of the doped support in step (2) includes:

[0116] Mix 4.2 g of P123 and 80 ml of absolute ethanol and dissolve them under ultrasonic treatment; then add 6.4 mL of concentrated nitric acid. After clarification, add 3.7 g of aluminum isopropoxide and 5.1 g of magnesium nitrate; stir for 5 h, dry at 60 °C for 48 h, and finally calcine at 800 °C for 3 h to obtain the doped support. The obtained doped support was characterized by XRD analysis. The results showed that the doped support had an ordered mesoporous structure.

[0117] The composition is shown in Table 1, and the evaluation results are shown in Table 2.

[0118] Comparative Example 1

[0119] (1) The preparation of indium oxide is the same as that in Example 1.

[0120] (2) The activity of the prepared indium oxide was evaluated on a fixed-bed reactor under the same reaction conditions as in Example 1, and the test results are shown in Table 2.

[0121] Comparative Example 2

[0122] (1) The preparation of indium oxide is the same as that in Example 1.

[0123] (2) Mix 4.2 g of P123 and 80 ml of absolute ethanol and dissolve them under ultrasonic treatment; then add 6.4 mL of concentrated nitric acid. After clarification, add 8.2 g of aluminum isopropoxide; stir for 5 h, dry at 60 °C for 48 h, and finally calcine at 800 °C for 3 h to obtain an alumina support.

[0124] (3) Mix 2 g of indium oxide and 1 g of alumina support and put them into a ball mill. Set the ball mill rotation speed to 300 rpm and the ball milling time to 5 h; then calcine the solid powder obtained after ball milling at 350 °C for 3 h to obtain an aluminum-doped indium oxide catalyst, which was pressed and sieved to 40-60 mesh.

[0125] (4) The reaction conditions for the activity test are the same as those in Example 1, and the activity test results are shown in Table 2.

[0126] Comparative Example 3

[0127] (1) Mix 4.2 g of P123 and 80 ml of absolute ethanol and dissolve them under ultrasound; then add 6.4 mL of concentrated nitric acid. After it becomes clear, add 5.0 g of aluminum isopropoxide and 3.1 g of magnesium nitrate; stir for 5 h, dry at 60 °C for 48 h, and finally calcine at 800 °C for 3 h to obtain the doped support precursor catalyst.

[0128] (2) Weigh 5.37 g of In(NO 3 ) 3 ·4H 2 O, dissolve it in 10 g of water, then pour it into 1 g of the doped support precursor catalyst, stir for 1 h, evaporate the water using a rotary evaporator, dry it in an oven at 120 °C 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.

[0129] (3) The reaction conditions for the activity test are the same as those in Example 1, and the activity test results are shown in Table 2.

[0130] Table 1

[0131]

[0132] Note: The content of each component in Table 1 is in mass percentage

[0133] Table 2

[0134]

[0135]

[0136] It can be seen from the results in Table 2 that, compared with Comparative Examples 1 - 3, it can be known that using the catalysts of Examples 1 - 7 of the present invention to catalyze the hydrogenation of carbon dioxide can effectively improve the conversion rate of carbon dioxide and can also improve the selectivity of methanol, indicating that the catalysts within the protection scope of the present invention have good catalytic effects and good methanol selectivity.

[0137] 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 all fall within the protection scope of the present invention.

Claims

1. A magnesium-aluminum doped indium oxide catalyst, which catalyst comprises an active component and a carrier, wherein the active component is indium oxide having a hexagonal structure, and the carrier comprises magnesium oxide and aluminum oxide. Based on the total amount of the catalyst, the content of indium oxide is 50-85% by weight, and the content of the carrier is 15-50% by weight; Based on the total amount of the catalyst, the content of magnesium oxide is 3-15% by weight; the weight ratio of aluminum oxide to magnesium oxide is 2.5-9.5:1; The mass ratio of the active component to the carrier is 1-6:1; The carrier has an ordered mesoporous structure; A method for preparing a magnesium-aluminum doped indium oxide catalyst, which method comprises the following steps: (1) Mix a magnesium-aluminum doped carrier containing aluminum oxide and magnesium oxide and indium oxide having a hexagonal structure, and then optionally pulverize; (2) Calcinate the product obtained in step (1).

2. The catalyst according to claim 1, wherein, Based on the total amount of the catalyst, the content of indium oxide is 60-80% by weight, and the content of the carrier is 20-40% by weight.

3. The catalyst according to claim 1, wherein, Based on the total amount of the catalyst, the content of magnesium oxide is 3-8% by weight; the weight ratio of aluminum oxide to magnesium oxide is 2.6-4.5:

1.

4. The catalyst according to any one of claims 1-3, wherein, The mass ratio of the active component to the carrier is 1-3:

1.

5. A method for preparing a magnesium-aluminum doped indium oxide catalyst according to any one of claims 1-4, which method comprises the following steps: (1) Mix a magnesium-aluminum doped carrier containing aluminum oxide and magnesium oxide and indium oxide having a hexagonal structure, and then optionally pulverize; (2) Calcinate the product obtained in step (1); Based on the total amount of the magnesium-aluminum doped carrier and indium oxide, the content of indium oxide is 50-85% by weight, and the content of the magnesium-aluminum doped carrier is 15-50% by weight.

6. The preparation method according to claim 5, wherein, The conditions of the calcination include: the temperature is 300-500 °C, and the time is 1-5 h.

7. The preparation method according to claim 5, wherein, Based on the total amount of the magnesium-aluminum doped carrier and indium oxide, the content of indium oxide is 60-80% by weight, and the content of the magnesium-aluminum doped carrier is 20-40% by weight.

8. The preparation method according to claim 5, wherein, Based on the total amount of the magnesium-aluminum doped carrier and indium oxide, the content of magnesium oxide in the magnesium-aluminum doped carrier is 3-15% by weight; the weight ratio of aluminum oxide to magnesium oxide is 2.5-9.5:

1.

9. The preparation method according to claim 8, wherein, Based on the total amount of the magnesium-aluminum doped carrier and indium oxide, the content of magnesium oxide in the magnesium-aluminum doped carrier is 3-8% by weight; the weight ratio of aluminum oxide to magnesium oxide is 2.6-4.5:

1.

10. The preparation method according to claim 5, wherein, The mass ratio of the amounts used of indium oxide and the magnesium-aluminum doped carrier is 1-6:

1.

11. The preparation method according to claim 10, wherein, The mass ratio of the amounts used of indium oxide and the magnesium-aluminum doped carrier is 1-3:

1.

12. The preparation method according to claim 5, wherein, the indium oxide is prepared by a precipitation method.

13. The preparation method according to claim 12, wherein, the preparation of the indium oxide comprises the following steps: (a) Mixing a solution containing a metal indium precursor with a precipitant solution to obtain a precipitation mother liquor; (b) Aging the precipitation mother liquor to form a precipitate; (c) Separating the solid and liquid of the product obtained in step (b), and then drying and calcining.

14. The preparation method according to claim 13, wherein, the solvents in the solution containing the metal indium precursor and the precipitant solution are independently an organic solvent and / or water.

15. The preparation method according to claim 14, wherein, the solvents in the solution containing the metal indium precursor and the precipitant solution are an organic solvent and water, and the organic solvent is selected from at least one of methanol, ethanol, isopropanol, ethylene glycol, triethylene glycol, and N,N-dimethylacetamide.

16. The preparation method according to claim 13, wherein, the concentration of the solution containing the metal indium precursor is 0.1 - 1 mol / L.

17. The preparation method according to claim 13, wherein, the concentration of the precipitant solution is 1 - 3 mol / L.

18. The preparation method according to claim 13, wherein, the precipitant is urea.

19. The preparation method according to claim 13, wherein, the mixing in step (a) is carried out under stirring conditions.

20. The preparation method according to claim 19, wherein, the mixing in step (a) is carried out for 1 - 10 h under stirring conditions.

21. The preparation method according to claim 13, wherein, the aging conditions in step (b) include: temperature is 80 - 160 °C, and time is 12 - 22 h.

22. The preparation method according to claim 13, wherein, the method further comprises washing the product obtained in step (b).

23. The preparation method according to claim 22, wherein, washing until the pH value of the product obtained in step (b) is between 6 - 8.

24. The preparation method according to claim 13, wherein, the calcining conditions in step (c) include: temperature is 300 - 500 °C, and time is 3 - 6 h.

25. The preparation method according to any one of claims 5 - 24, wherein, a magnesium-aluminum doped carrier is prepared by a solvent evaporation-induced self-assembly method.

26. The preparation method according to claim 25, wherein, the preparation method of the magnesium-aluminum doped carrier comprises: 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.

27. The preparation method according to claim 26, wherein, The surfactant is selected from at least one of P123, cetyltrimethylammonium bromide, malic acid, sodium 2-ethylhexane sulfosuccinate, and nonylphenol polyoxyethylene ether; the solvent is selected from at least one of methanol, ethanol, 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 selected from at least one of aluminum isopropoxide, aluminum nitrate, aluminum chloride, and aluminum sulfate.

28. The preparation method according to claim 26, wherein, the mixing time of the acid, the aluminum precursor, and the magnesium precursor is 3 - 9 h.

29. The preparation method according to claim 28, wherein, the mixing is carried out under stirring conditions.

30. The preparation method according to claim 26, wherein, the calcination conditions include: the temperature is 600 - 1200 °C, and the time is 3 - 6 h.

31. A method for preparing methanol by hydrogenating carbon dioxide, the method comprises: contacting carbon dioxide and hydrogen under the condition of hydrogenating carbon dioxide in the presence of a catalyst; the catalyst is the magnesium-aluminum doped indium oxide catalyst described in any one of claims 1 - 4 or the magnesium-aluminum doped indium oxide catalyst prepared by the preparation method described in any one of claims 5 - 30.

32. The method according to claim 31, 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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