Magnesium-aluminum-doped indium oxide catalyst, method for preparing the same, and method for preparing methanol by carbon dioxide hydrogenation

Abstract

The application relates to the field of catalysts, and discloses a magnesium-aluminum-doped indium oxide catalyst, a preparation method thereof and a method for preparing methanol by carbon dioxide hydrogenation, the catalyst comprising a carrier and an active component loaded on the carrier; the active component is indium oxide, and the carrier comprises magnesium oxide and aluminum oxide; wherein the specific surface area of the catalyst is not less than 54 m<2> / g, the CO2 desorption amount of the catalyst in a temperature range of 150-400 DEG C is not less than 500 mu mol / g, and the CO2 desorption amount is measured by a temperature programmed desorption method. 2 The magnesium-aluminum-doped indium oxide catalyst provided by the application has a higher specific surface area, more moderate-strength basic sites, can obtain higher catalytic activity at a lower temperature and pressure, has high CO2 conversion rate, and has good methanol selectivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalysts, in particular to a magnesium-aluminum-doped indium oxide catalyst, a preparation method thereof and a method for preparing methanol by hydrogenation of carbon dioxide. BACKGROUND

[0002] The rapid development of global economy has led to an increase in CO2 emissions, causing environmental problems such as global warming due to the greenhouse effect. Therefore, an effective measure is needed to reduce the concentration of CO2 in the atmosphere by capturing and converting CO2. Methanol, as an important raw material for chemicals and a substitute for fossil fuels, is an effective way to solve the control of greenhouse gases and the substitution of fossil fuels by preparing methanol from CO2 and H2 from renewable energy.

[0003] Among numerous catalysts for the preparation of methanol by hydrogenation of CO2, modified copper-based catalysts have been studied and applied for a long time. Cu-based catalysts for the traditional synthesis of methanol have been widely studied in the preparation of methanol from carbon dioxide. However, the high activity of the side reaction (RWGS) and the characteristics of H2O-induced active phase sintering 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 some extent. In2O3 has moderate CO2 and CO adsorption capacity, showing significantly better methanol selectivity than Cu, Co and noble metal catalysts, and higher catalytic activity than ZnO catalysts, thus attracting widespread attention from researchers. CN110479235A discloses the use of a hydrothermal method to synthesize an indium oxide catalyst, but a higher catalytic activity can only be obtained after activation, and the synthesis time is long and the production efficiency is low. In addition, In2O3 is easy to load and modify on the surface, which can further promote the activation of carbon dioxide and H2, and stabilize the key intermediates to achieve high activity, high selectivity and stability, providing great potential for designing and preparing efficient methanol synthesis catalysts. In the prior art, indium oxide and the carrier are synthesized separately, and then solid-phase mixing or impregnation is performed to achieve the loading and modification of In2O3. However, the catalytic activity of the indium oxide catalyst prepared by the above method still cannot meet the requirements of industrial production, and it is essential to design and develop more effective indium oxide catalysts for the industrial application of CO2 hydrogenation to methanol, although there are still great challenges in greatly improving its catalytic performance. SUMMARY

[0004] The application aims to overcome the problems of the prior art, such as low catalytic activity of the indium oxide catalyst, complex preparation process and low production efficiency, and provides a magnesium-aluminum doped indium oxide catalyst, a preparation method thereof and a method for preparing methanol by carbon dioxide hydrogenation, the magnesium-aluminum doped indium oxide catalyst has a high specific surface area, excellent catalytic performance, high reaction activity and high selectivity of target products.

[0005] To achieve the above-mentioned object, the first aspect of the application provides a magnesium-aluminum doped indium oxide catalyst, the catalyst comprising a carrier and an active component loaded on the carrier; the active component is indium oxide, and the carrier comprises magnesium oxide and aluminum oxide.

[0006] The specific surface area of the catalyst is not less than 54 m 2 / g; the CO2 desorption amount of the catalyst at 150-400 DEG C is not less than 500 μmol / g, which is measured by temperature programmed desorption.

[0007] The second aspect of the application provides a preparation method of the magnesium-aluminum doped indium oxide catalyst, comprising the following steps:

[0008] (1) providing a solution A containing indium salt, magnesium salt and aluminum salt, and a solution B containing a precipitating agent;

[0009] (2) mixing the solution A and the solution B to obtain a mother liquor C;

[0010] (3) aging the mother liquor C under microwave reaction conditions;

[0011] The microwave reaction conditions comprise: microwave output power is 500-2000 W, reaction temperature is 60-200 DEG C, and aging time is 0.5-24 h;

[0012] (4) performing solid-liquid separation on the product obtained in step (3), and then drying and calcining to obtain the magnesium-aluminum doped indium oxide catalyst.

[0013] The third aspect of the application provides the magnesium-aluminum doped indium oxide catalyst prepared by the above-mentioned preparation method.

[0014] The fourth aspect of the application provides a method for preparing methanol by carbon dioxide hydrogenation, the method comprising: under the conditions of preparing methanol by carbon dioxide hydrogenation, contacting carbon dioxide and hydrogen in the presence of a catalyst; the catalyst comprises the magnesium-aluminum doped indium oxide catalyst according to the first aspect and the third aspect.

[0015] Through the above technical solution, the application has the following beneficial effects:

[0016] (1) The magnesium-aluminum doped indium oxide catalyst provided by the present invention has a high specific surface area, a large number of medium-strength basic sites, high reaction activity, high selectivity of target products, good reaction stability and low catalyst deactivation rate.

[0017] (2) The preparation method of magnesium-aluminum doped indium oxide catalyst provided by the present invention is simple to operate. It utilizes the response of the precipitant to microwaves to promote the rapid hydrolysis of metal complexes / coordination compounds, which is conducive to the formation of catalysts with large specific surface area and many oxygen vacancies. The one-step hydrothermal synthesis of magnesium-aluminum doped indium oxide catalyst with microwave assistance has a short reaction time, which is conducive to improving production efficiency and has the advantages of high efficiency and energy saving.

[0018] (3) The method for preparing methanol by carbon dioxide hydrogenation provided by the present invention uses the magnesium-aluminum doped indium oxide catalyst provided by the present invention, which can obtain high catalytic activity at lower temperature and pressure, high CO2 conversion rate and good methanol selectivity. Attached Figure Description

[0019] Figure 1 These are CO2-TPD curves of the catalysts in Examples 1, 2, and Comparative Example 1. Detailed Implementation

[0020] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0021] The first aspect of the present invention provides a magnesium-aluminum doped indium oxide catalyst, the catalyst comprising a support and an active component supported on the support; the active component is indium oxide, and the support comprises magnesium oxide and aluminum oxide;

[0022] The catalyst has a specific surface area of ​​not less than 54 m². 2 / g; the CO2 desorption capacity of the catalyst in the temperature range of 150-400℃ is not less than 500 μmol / g, as determined by temperature-programmed desorption.

[0023] The inventors of this invention discovered in their research that the above-mentioned magnesium-aluminum doped indium oxide catalyst has a high specific surface area and a large number of moderately strong basic sites. Conventional precipitation-based indium oxide catalysts have a low specific surface area, and the complex preparation methods are not conducive to implementation. The intermediate process remains unchanged and is controlled. The catalyst exhibits excellent catalytic performance in the reaction of carbon dioxide hydrogenation to methanol, which can effectively improve the conversion rate of carbon dioxide and the selectivity of methanol in the catalytic reaction. It has high selectivity for the target product, good reaction stability, and low catalyst deactivation rate.

[0024] In the present application, the CO2 desorption amount of the catalyst in the temperature range of 150-400℃ is calculated by the CO2 temperature programmed desorption method. It can be understood that the CO2 desorption amount can represent the basicity distribution of the catalyst surface. In a certain temperature range, the higher the CO2 desorption amount, the more basic sites of the catalyst surface in the temperature range.

[0025] According to the present application, the medium-strength basic sites of the catalyst surface are represented by the CO2 desorption amount in the temperature range of 150-400℃, and the inventors of the present application have found in the research that the appropriate amount of medium-strength basic sites of the catalyst surface is conducive to the chemical adsorption and conversion of CO2, and further conducive to improving the catalytic activity of the catalyst in the reaction of preparing methanol from carbon dioxide and hydrogen. Preferably, the integral area of the CO2 desorption peak of the catalyst in the temperature range of 150-400℃ is 500-1000 μmol / g, and further preferably 500-800 μmol / g.

[0026] Preferably, the specific surface area of the catalyst is 60-80 m 2 / g. In the above preferred case, the catalytic activity of the catalyst can be further improved, and the conversion rate of the raw material can be improved.

[0027] In the present application, the testing method of the specific surface area is as follows: the specific surface area of the catalyst is analyzed by low-temperature N2 constant temperature adsorption-desorption and conventional BET calculation processing. Before analysis, the sample is dried at 120℃ for 2h, and then subjected to air extraction treatment under vacuum and at 300℃. The adsorption medium is high-purity nitrogen. The adsorption / desorption experiment is carried out under liquid nitrogen cooling condition (-196℃).

[0028] In the catalyst provided by the present application, preferably, the content of indium oxide is 50-90wt%, and further preferably 60-85wt%, based on the total amount of the catalyst, and the content of the carrier is 10-50wt%, and further preferably 15-40wt%.

[0029] In the present application, preferably, the molar ratio of aluminum and magnesium, calculated on the basis of elements, is 1-5:1, and further preferably 1-3:1. In the above preferred case, the synergistic effect between the active component and the carrier can be further exerted, and the catalytic performance of the catalyst can be improved.

[0030] In the present application, the content of each component is tested by ICP-AES.

[0031] According to a preferred embodiment of the present application, the magnesium-aluminum doped indium oxide catalyst is prepared by microwave-assisted hydrothermal synthesis. The microwave-assisted one-step hydrothermal synthesis of the catalyst helps to improve the dispersion of the active component, increase the medium-strength basic sites in the catalyst, and enhance the synergistic effect between the active component and the carrier, thereby further improving the conversion rate of carbon dioxide and the selectivity of methanol.

[0032] In the carrier of the present application, magnesium oxide and aluminum oxide can be mixed in any ratio. Preferably, the content of magnesium oxide is 5-15 wt%, and the content of aluminum oxide is 10-35 wt%, based on the total amount of the catalyst.

[0033] The second aspect of the present application provides a preparation method of a magnesium-aluminum doped indium oxide catalyst, comprising the following steps:

[0034] (1) providing a solution A containing indium salt, magnesium salt and aluminum salt, and a solution B containing a precipitating agent;

[0035] (2) mixing the solution A and the solution B to obtain a mother liquor C;

[0036] (3) aging the mother liquor C under microwave reaction conditions;

[0037] wherein the microwave reaction conditions include a microwave output power of 500-2000 W, a reaction temperature of 60-200°C, and an aging time of 0.5-24 h;

[0038] (4) performing solid-liquid separation on the product obtained in step (3), and then drying and calcining to obtain the magnesium-aluminum doped indium oxide catalyst.

[0039] Microwave radiation is electromagnetic radiation with a frequency range of 0.3-300 GHz, corresponding to a wavelength of 1 cm-1 m. The commercial microwave reactors used in conventional chemical synthesis have a working frequency of 2.45 GHz (corresponding to a wavelength of 12.25 cm). The inventors of the present application have found that by microwave-assisted one-step hydrothermal synthesis of the catalyst, the use of local hot spots of microwaves promotes the rapid hydrolysis of the metal complex formed, and through molecular-scale mixing in the solution, it helps to improve the dispersion of the active component, ensure uniformity, and enhance the synergistic effect between the active component and the carrier in the catalyst. The magnesium-aluminum doped indium oxide catalyst obtained has a high specific surface area, more medium-strength basic sites, excellent catalytic performance, high reaction activity, high selectivity of the target product, good reaction stability, and low catalyst deactivation rate.

[0040] The concentration of the metal salt in the solution A can be determined by those skilled in the art according to actual conditions, preferably, the total concentration of the indium salt, the magnesium salt and the aluminum salt in the solution A is 0.5-5 mol / L, preferably 1-3 mol / L in terms of elements; under the above preferred conditions, the uniformity of the hydrothermal precipitation is improved.

[0041] In order to further exert the synergistic effect between the active component and the carrier and improve the conversion rate of carbon dioxide and the methanol selectivity, preferably, the amount of the indium salt, the magnesium salt and the aluminum salt is such that the content of indium oxide is 50-90 wt%, preferably 60-85 wt%, and the content of the carrier is 10-50 wt%, preferably 15-40 wt% based on the total amount of the prepared catalyst.

[0042] In the carrier of the present application, the relative content of the magnesium salt and the aluminum salt in the solution A can be in any ratio. Preferably, the molar ratio of the aluminum salt to the magnesium salt is 1-5:1, further preferably 1-3:1 in terms of metal elements.

[0043] Preferably, the amount of the magnesium salt and the aluminum salt is such that the content of magnesium oxide is 2-20 wt% and the content of aluminum oxide is 8-40 wt% based on the total amount of the prepared catalyst; further preferably, the content of magnesium oxide is 5-15 wt% and the content of aluminum oxide is 10-35 wt% based on the total amount of the prepared catalyst.

[0044] According to a preferred embodiment of the present application, the concentration of the precipitant in the solution B is 0.5-5 mol / L, preferably 1-3 mol / L.

[0045] According to a preferred embodiment of the present application, the total concentration of the indium salt, the magnesium salt and the aluminum salt in the solution A is 0.1-5 mol / L, preferably 0.5-2 mol / L in terms of elements;

[0046] Preferably, the amount of the precipitant is 1-4 times the stoichiometric ratio of the metal atom number in terms of precipitation or coordination; under the above preferred conditions, the metal salt solution and the precipitant are fully contacted, and the precipitation effect is improved.

[0047] In the preparation method of the present application, the above mixing can be stirring mixing, ultrasonic mixing or other feasible mixing modes. The stirring mixing can be magnetic stirring, mechanical stirring or manual stirring, etc. The conditions of the ultrasonic mixing and the stirring conditions can be determined by those skilled in the art according to actual conditions.

[0048] Preferably, the mixing in step (2) comprises: mixing solution B into solution A under stirring; further preferably, in the step (2), the mixing of solution B and solution A is performed by adding solution B into solution A and continuously stirring during the adding process and after the adding process.

[0049] Further preferably, the adding rate of solution B is 5-100 mL / min, further preferably 10-30 mL / min; such preferred embodiments can enable the metal salt solution and the precipitant to be in sufficient contact, thereby improving the precipitation effect.

[0050] In the present application, the mixing can be performed at room temperature or under heating, preferably, the temperature of the mixing is 20-80°C, preferably 40-60°C. At the above mixing temperature, the mixing uniformity can be improved.

[0051] In the present application, the indium salt, the magnesium salt and the aluminum salt can be any conventional selection in the art, preferably, the indium salt, the magnesium salt and the aluminum salt are soluble salts of indium, magnesium and aluminum, which can be organic salts and / or inorganic salts; further preferably, the indium salt, the magnesium salt and the aluminum salt are each independently selected from at least one of nitrate, acetate, sulfate and halide of indium, magnesium and aluminum.

[0052] According to the present application, in order to facilitate the enhancement of the response to microwave, increase the local hot spot of microwave, thereby promoting the rapid hydrolysis of the metal complex, preferably, the precipitant is a precipitant with polar substance characteristics; further preferably, the precipitant is selected from at least one of ammonia, ammonium carbonate, ammonium bicarbonate, urea and citric acid; more preferably at least one of urea, ammonium bicarbonate and ammonia.

[0053] In the present application, preferably, the solution A and the solution B further contain a solvent, which can be a conventional selection in the art, as long as the uniform mixing of the components in the solution A and the solution B can be achieved. Preferably, the solvent in the solution A and the solution B is each independently an organic solvent and / or water, preferably an organic solvent and water; further preferably, in the solvent, the volume ratio of water and the organic solvent is 0.1-10:1.

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

[0055] According to the present application, the magnesium-aluminum doped indium oxide catalyst is prepared by one-step microwave-assisted hydrothermal synthesis, which can further shorten the reaction time and improve the preparation efficiency. Preferably, in step (2), the microwave reaction conditions include: microwave output power of 500-1500 W, reaction temperature of 80-160℃, and aging time of 0.5-8 h; by using the above preferred embodiments, the reaction time can be further shortened while ensuring the catalytic activity of the catalyst.

[0056] According to the present application, there is no special requirement for the reaction device in step (2), and a conventional microwave synthesis instrument can be used for the reaction, wherein the frequency of the microwave is preferably 2.45 GHz.

[0057] Preferably, the method further comprises washing the product obtained in step (3), preferably washing until the pH value of the washing mother liquor is between 6-8. The purity of the obtained product can be improved. According to the present application, the washing method is not particularly limited and can be performed according to conventional technical means in the art. Preferably, the centrifugation method can be used, which can simultaneously achieve the above-mentioned solid-liquid separation and washing.

[0058] According to the present application, the drying and calcination in step (4) can be performed by conventional means and devices in the art. Preferably, in step (4), the drying conditions include: drying at 50-90℃ for 0.5-3 h.

[0059] Preferably, in step (4), the calcination conditions include: calcination at 200-600℃ for 1-5 h, and further preferably, the calcination conditions include: calcination at 300-500℃ for 2-4 h.

[0060] In the present application, preferably, the solution A further contains a template agent. The inventors of the present application found in the research that, under the cooperation of the template agent and the precipitating agent, the response to the microwave can be further enhanced, the local hot spots of the microwave can be increased, the rapid hydrolysis of the metal complex can be promoted, the uniformity can be improved, and the synergistic effect between the active components and the carrier in the catalyst can be enhanced.

[0061] Preferably, the amount of the template agent is 0.01-1:1 based on the total mass of the aluminum salt and the magnesium salt.

[0062] Preferably, the template agent is selected from at least one of cetyltrimethylammonium bromide, polyoxyethylene-polyoxypropylene-polyoxyethylene amphiphilic block copolymer (F127, preferably having a number average molecular weight of 1000-10000), polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123, preferably having a number average molecular weight of 500-10000), polyoxyethylene polyoxypropylene block polyether (F108, preferably having a number average molecular weight of 1000-10000), polyethylene glycol (PEG, preferably having a number average molecular weight of 200-5000), polyoxyethylene ether (preferably having a number average molecular weight of 2000-10000); preferably polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer and / or polyethylene glycol.

[0063] In the present application, in order to further improve the uniformity of the material mixing, preferably, the template agent and the solvent are mixed and dissolved, and after clarification, the aluminum salt and the magnesium salt are mixed to obtain a mixed solution.

[0064] According to the present application, preferably, the mixing in the above preparation method is carried out under stirring, and the stirring mode is not particularly limited, for example, conventional stirring modes such as ultrasonic can be used, as long as the mixture can be uniformly mixed. Preferably, the mixing time is 1-3h.

[0065] According to a particularly preferred embodiment of the present application, a preparation method of a magnesium-aluminum doped indium oxide catalyst is provided, which comprises the following steps:

[0066] (1) providing a solution A containing an indium salt, a magnesium salt and an aluminum salt, and a solution B containing a precipitating agent; the precipitating agent is urea and / or ammonia water, the total concentration of the indium salt, the magnesium salt and the aluminum salt in the solution A is 0.5-5mol / L, the concentration of the precipitating agent in the solution B is 1-3mol / L; the solution A further contains a template agent, and the template agent is polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer and / or polyethylene glycol;

[0067] (2) adding the solution B dropwise to the solution A in a 55℃ water bath, and continuously stirring during the adding process and after the adding is completed, to obtain a mother liquor C; the adding rate of the solution B is 10-30mL / min, the stirring rate is 100-400rpm, and the stirring time after the precipitation is completed is 5-60min;

[0068] (3) aging the mother liquor C under microwave reaction conditions;

[0069] wherein, the microwave reaction conditions include: microwave output power is 500-1500W, reaction temperature is 80-160℃, and aging time is 0.5-8h;

[0070] (4) performing solid-liquid separation on the product obtained in step (3), and then drying and calcining to obtain the magnesium-aluminum doped indium oxide catalyst, wherein the drying is performed at 60-90℃ for 0.5-3h, and the calcining is performed at 300-500℃ for 2-4h;

[0071] The content of the indium oxide is 60-90wt%, the content of the carrier is 10-40wt%, the content of the magnesium oxide is 5-15wt%, the content of the aluminum oxide is 10-35wt%, and the molar ratio of aluminum to magnesium is 1-3:1 in terms of elements, based on the total amount of the magnesium-aluminum doped carrier and the indium oxide.

[0072] The third aspect of the present application provides the magnesium-aluminum doped indium oxide catalyst prepared by the above preparation method.

[0073] In the present application, the particle size of the magnesium-aluminum doped indium oxide catalyst can be selected in a wide range, and can be adjusted according to actual reaction and production requirements. Preferably, the magnesium-aluminum doped indium oxide catalyst is obtained after tabletting, crushing and sieving, and the particle size of the catalyst is 40-60 mesh.

[0074] The fourth aspect of the present application provides a method for preparing methanol by carbon dioxide hydrogenation, which comprises: contacting carbon dioxide and hydrogen in the presence of a catalyst under the conditions of preparing methanol by carbon dioxide hydrogenation; and the catalyst comprises the above magnesium-aluminum doped indium oxide catalyst.

[0075] According to the present application, the reaction of preparing methanol by carbon dioxide hydrogenation can be performed under low temperature and low pressure conditions, with high CO2 conversion rate and high methanol selectivity. Preferably, the conditions of the reaction of preparing methanol by carbon dioxide hydrogenation comprise: a reaction pressure of 1-5MPa, preferably 2-5MPa, a reaction temperature of 200-400℃, preferably 250-400℃, a volume space velocity of 4500-18000h -1 , preferably 8000-12000h -1 , and a molar ratio of H2 / CO2 of 1-6, preferably 3-6.

[0076] According to the present application, preferably, the method further comprises, before the contacting, pretreating the catalyst in the presence of a hydrogen-containing gas.

[0077] Preferably, the pretreatment conditions comprise: a reaction pressure of 0.1-1MPa, a reaction temperature of 200-400℃, preferably 300-400℃, and a volume space velocity of the hydrogen-containing gas of 2000-8000h -1 , preferably 4000-6000h -1 .

[0078] In the present application, preferably, the hydrogen-containing gas is hydrogen gas or a mixture of hydrogen gas and inert gas; preferably, the inert gas is nitrogen.

[0079] In the present application, preferably, the content of hydrogen gas in the hydrogen-containing gas is 5-20 vol%, preferably 8-12 vol%.

[0080] The present application will be described in detail below by way of examples.

[0081] In the following examples, the specific surface area of the catalyst was analyzed by low-temperature N2 constant temperature adsorption-desorption and processed by conventional BET calculation. Before analysis, the sample was dried at 120°C for 2h, and then subjected to air extraction treatment under vacuum condition at 300°C. The adsorption medium was high-purity nitrogen. The adsorption / desorption experiment was carried out under liquid nitrogen cooling condition (-196°C).

[0082] Example 1

[0083] (1) 15.44g In(NO3)3·4H2O was added to a mixed solution of 80mL anhydrous ethanol and 48mL deionized water; 4.2g P123 and 80mL anhydrous ethanol were mixed and dissolved under ultrasonic; then 5.0g aluminum isopropoxide and 3.1g magnesium nitrate were added and mixed with the former indium solution to obtain solution A.

[0084] 16g urea was added to a mixed solution of 80mL anhydrous ethanol and 20mL deionized water to obtain solution B.

[0085] (2) Precipitant solution B was added to metal salt solution A at 55°C to obtain mother liquor C, the addition rate of the precipitant solution was 10mL / min, after the precipitation was completed, the stirring was continued for 0.5h, then the mother liquor C was added to a 200mL polytetrafluoroethylene-lined hydrothermal synthesis reactor, and was aged in a microwave synthesis instrument, the microwave output power was 1500W, the temperature was 150°C, and the aging time was 2h.

[0086] After the hydrothermal kettle was naturally cooled to room temperature, the mother solution was centrifuged with deionized water to pH 7, then dried at 60°C for 12h, and then calcined at 400°C for 3h to obtain a magnesium-aluminum-doped indium oxide catalyst, which was pressed into a sheet and sieved to 40-60 mesh. The composition and specific surface area data of the catalyst are shown in Table 1.

[0087] The CO2 adsorption and thermal desorption test was carried out at 50-500°C by temperature programmed desorption, the desorption peak is shown in Figure 1 , and the CO2 desorption amount of the catalyst in the temperature range of 150-400°C was calculated and shown in Table 1.

[0088] Catalyst evaluation:

[0089] The reaction of carbon dioxide hydrogenation to prepare methanol was carried out in a stainless steel reactor with an inner diameter of 8 mm. Before the reaction, the catalyst was pretreated. The hydrogen gas with a hydrogen volume fraction of 10% was mixed with nitrogen gas. The pressure was normal pressure. The temperature was 400 ℃. The volume space velocity was 4000 h -1 , and the pretreatment time was 2 h.

[0090] Then, the reaction of carbon dioxide hydrogenation to prepare methanol was carried out. The reaction conditions were as follows: 3.0 MPa, 280 ℃, 10000 h -1 , n(H2) / n(CO2)=4. After the reaction for 3 h, 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 2

[0092] (1) 10.0 g of In(NO3)3·4H2O was added to a mixed solution of 70 mL of anhydrous ethanol and 30 mL of deionized water; 3.8 g of P123 and 80 mL of anhydrous ethanol were mixed and dissolved under ultrasonic; then 9.5 g of aluminum isopropoxide and 4.0 g of magnesium nitrate were added and mixed with the former indium solution to obtain solution A.

[0093] 25 g of ammonium bicarbonate was added to a mixed solution of 60 mL of anhydrous ethanol and 20 mL of deionized water to obtain solution B.

[0094] (2) The precipitant solution was added to the metal salt solution at 55 ℃ to obtain mother solution C. The addition rate of the precipitant solution was 10 mL / min. After the precipitation was completed, the stirring was continued for 10 min. Then, the mother solution was added to a 200 mL polytetrafluoroethylene-lined hydrothermal synthesis reactor. The reactor was placed in a microwave synthesis instrument for aging. The microwave output power was 1500 W. The temperature was 150 ℃. The aging time was 4 h. After the hydrothermal reactor was naturally cooled to room temperature, the mother solution was centrifuged with deionized water until the pH was 7. Then, the solution was dried at 60 ℃ for 12 h. Then, the catalyst was calcined at 400 ℃ for 3 h to obtain a magnesium-aluminum-doped indium oxide catalyst. The catalyst was pressed and sieved to 40-60 mesh. The composition and specific surface area data of the catalyst are shown in Table 1.

[0095] The CO2 adsorption and thermal desorption test was carried out by temperature programmed desorption at 50-500 ℃. The desorption peak is shown in Figure 1 . The CO2 desorption amount of the catalyst in the temperature range of 150-400 ℃ was calculated and shown in Table 1.

[0096] Catalyst evaluation:

[0097] The reaction of carbon dioxide hydrogenation to prepare methanol was carried out in a stainless steel reactor with an inner diameter of 8 mm. Before the reaction, the catalyst was pretreated. The hydrogen gas with a hydrogen volume fraction of 10% was mixed with nitrogen gas. The pressure was normal pressure. The temperature was 400 ℃. The volume space velocity was 4000 h-1 , pretreatment 2h.

[0098] Then the carbon dioxide hydrogenation reaction to prepare methanol was carried out, and the reaction conditions were as follows: 5.0 MPa, 300℃, 6750h -1 , n(H2) / n(CO2) = 6, after 3h reaction, the liquid product was collected with ice water bath, the product composition was analyzed by gas chromatography, and the evaluation results are shown in Table 2.

[0099] Example 3

[0100] (1) 8.5g In(NO3)3·4H2O was added to a mixed solution of 50mL anhydrous ethanol and 25mL deionized water; 5.2g P123 and 100mL anhydrous ethanol were mixed and dissolved under ultrasonic; then 9.5g aluminum nitrate and 3.82g magnesium nitrate were added and mixed with the former indium solution to obtain solution A.

[0101] 8g urea was added to a mixed solution of 60mL anhydrous ethanol and 25mL deionized water to obtain solution B.

[0102] (2) The precipitant solution was added to the metal salt solution at 55℃ to obtain mother solution C, the addition rate of the precipitant solution was 10mL / min, after the precipitation was completed, the stirring was continued for 0.5h, then the mother solution was added to a 200mL polytetrafluoroethylene lined hydrothermal synthesis reactor, and was aged in a microwave synthesis instrument, the microwave output power was 1500W, the temperature was 180℃, and the aging time was 8h. After the hydrothermal reactor was naturally cooled to room temperature, the mother solution was centrifuged with deionized water to pH 7, then was dried at 60℃ for 12h, and then was calcined at 400℃ for 3h to obtain a magnesium-aluminum doped indium oxide catalyst, which was pressed into a tablet and sieved to 40-60 mesh. The composition and specific surface area data of the catalyst are shown in Table 1.

[0103] CO2 adsorption and thermal desorption tests were carried out at 50-500℃ by temperature programmed desorption, and the CO2 desorption amount of the catalyst in the temperature range of 150-400℃ was calculated and shown in Table 1.

[0104] Catalyst evaluation:

[0105] The carbon dioxide hydrogenation reaction to prepare methanol was carried out in a stainless steel reactor with an inner diameter of 8mm, and the catalyst was pretreated before the reaction. The hydrogen gas mixture with a hydrogen volume fraction of 10% was used, the pressure was normal pressure, the temperature was 400℃, and the volume space velocity was 4000h -1 , pretreatment 2h.

[0106] Then the carbon dioxide hydrogenation reaction to prepare methanol was carried out, and the reaction conditions were as follows: 5.0 MPa, 340℃, 18000h -1, n(H2) / n(CO2) = 4, after 3 h of reaction, the liquid product was collected in an ice water bath, the product composition was analyzed by gas chromatography, and the evaluation results are shown in Table 2.

[0107] Example 4

[0108] (1) 10.3 g of In(NO3)3·4H2O was added to a mixed solution of 80 mL of anhydrous ethanol and 40 mL of deionized water; 4.7 g of P123 and 90 mL of anhydrous ethanol were mixed and dissolved under ultrasonic; then 8.5 g of aluminum nitrate and 4.77 g of magnesium nitrate were added and mixed with the former indium solution to obtain solution A.

[0109] 9.2 g of urea was added to a mixed solution of 80 mL of anhydrous ethanol and 30 mL of deionized water to obtain solution B.

[0110] (2) The precipitant solution was added to the metal salt solution at 55°C to obtain mother solution C, the addition rate of the precipitant solution was 10 mL / min, after the precipitation was completed, the stirring was continued for 15 min, then the mother solution was added to a 200 mL polytetrafluoroethylene lined hydrothermal synthesis reactor, and was aged in a microwave synthesis instrument, the microwave output power was 1500 W, the temperature was 120°C, and the aging time was 12 h. After the hydrothermal reactor was naturally cooled to room temperature, the mother solution was centrifuged to pH 7 with deionized water, then was dried at 60°C for 12 h, and was calcined at 400°C for 3 h to obtain a magnesium-aluminum doped indium oxide catalyst, which was pressed into a tablet and sieved to 40-60 mesh. The composition and specific surface area data of the catalyst are shown in Table 1.

[0111] CO2 adsorption and thermal desorption tests were carried out at 50-500°C by temperature programmed desorption, and the CO2 desorption amount of the catalyst in the temperature range of 150-400°C was calculated and shown in Table 1.

[0112] Catalyst evaluation:

[0113] The carbon dioxide hydrogenation reaction for preparing methanol was carried out in a stainless steel reactor with an inner diameter of 8 mm, the catalyst was pretreated before the reaction, a mixed gas of hydrogen and nitrogen with a hydrogen volume fraction of 10% was used, the pressure was normal pressure, the temperature was 400°C, the volume space velocity was 4000 h -1 , and the pretreatment time was 2 h.

[0114] Then the carbon dioxide hydrogenation reaction for preparing methanol was carried out, the reaction conditions were as follows: 1.0 MPa, 280°C, 9000 h -1 , n(H2) / n(CO2) = 5, after 3 h of reaction, the liquid product was collected in an ice water bath, the product composition was analyzed by gas chromatography, and the evaluation results are shown in Table 2.

[0115] Example 5

[0116] (1) 6.4 g In(NO3)3.4H2O was added to a mixed solution of 40 mL anhydrous ethanol and 20 mL deionized water; 7.3 g P123 and 120 mL anhydrous ethanol were mixed and dissolved under ultrasonic; then 4.2 g aluminum nitrate and 5.73 g magnesium nitrate were added and mixed with the former indium solution to obtain solution A.

[0117] 6.5 g urea was added to a mixed solution of 50 mL anhydrous ethanol and 20 mL deionized water to obtain solution B.

[0118] (2) The precipitant solution was added to the metal salt solution at 65°C to obtain mother solution C, the adding rate of the precipitant solution was 10 mL / min, after the precipitation was completed, the stirring was continued for 15 min, then the mother solution was added to a 200 mL polytetrafluoroethylene lined hydrothermal synthesis reactor, and was aged in a microwave synthesis instrument, the microwave output power was 1500 W, the temperature was 120°C, and the aging time was 6 h. After the hydrothermal reactor was naturally cooled to room temperature, the mother solution was centrifuged with deionized water until the pH was 7, then was dried at 60°C for 12 h, and was calcined at 400°C for 3 h to obtain a magnesium-aluminum doped indium oxide catalyst, which was pressed into a tablet and sieved to 40-60 mesh. The composition and specific surface area data of the catalyst are shown in Table 1.

[0119] The CO2 adsorption and thermal desorption tests were carried out at 50-500°C by temperature programmed desorption, and the CO2 desorption amount of the catalyst in the temperature range of 150-400°C was calculated and shown in Table 1.

[0120] Catalyst evaluation:

[0121] The carbon dioxide hydrogenation reaction for preparing methanol was carried out in a 8 mm inner diameter stainless steel reactor, the catalyst was pretreated before the reaction, the hydrogen gas volume fraction was 10% of the mixed gas of hydrogen and nitrogen, the pressure was normal pressure, the temperature was 400°C, the volume space velocity was 4000 h -1 , and the pretreatment time was 2 h.

[0122] Then the carbon dioxide hydrogenation reaction for preparing methanol was carried out, the reaction conditions were as follows: 4.0 MPa, 280°C, 13000 h -1 , n(H2) / n(CO2)=6, after the reaction for 3 h, the liquid product was collected with an ice water bath, the product composition was analyzed by gas chromatography, and the evaluation results are shown in Table 2.

[0123] Example 6

[0124] According to the method in Example 1, except that the microwave output power was 1000 W and the reaction temperature was 100°C, the composition, specific surface area and CO2 desorption amount in the temperature range of 150-400°C of the obtained catalyst were shown in Table 1, and the evaluation results are shown in Table 2.

[0125] Example 7

[0126] The procedure of Example 1 was followed except that the urea solution was replaced by an aqueous ammonia solution. The composition, specific surface area, and CO2 desorption amount in the temperature range of 150-400°C of the obtained catalyst were shown in Table 1, and the evaluation results were shown in Table 2.

[0127] Example 8

[0128] The procedure of Example 1 was followed except that no template was added. The composition, specific surface area, and CO2 desorption amount in the temperature range of 150-400°C of the obtained catalyst were shown in Table 1, and the evaluation results were shown in Table 2.

[0129] Comparative Example 1

[0130] (1) 7.6 g of In(NO3)3.4H2O was added to a mixture of 40 mL of anhydrous ethanol and 24 mL of deionized water. 8 g of urea was added to a mixture of 40 mL of anhydrous ethanol and 10 mL of deionized water. The precipitant solution was added to the metal indium salt solution at 30°C to obtain a mother solution, and the addition rate of the precipitant solution was 10 mL / min based on 1 L of the indium salt solution, and the mother solution was stirred for 1 h, and then was added to a 200 mL polytetrafluoroethylene-lined hydrothermal synthesis reactor, and was placed in a drying oven for aging, and the microwave output power was 1500 W, the aging temperature was 120°C, and the aging time was 2 h. After the hydrothermal reactor was naturally cooled to room temperature, the mother solution was centrifuged with deionized water to pH 7, and then was dried at 60°C for 20 h, and then was calcined at 400°C for 3 h to obtain an indium oxide catalyst, which was pressed and sieved to 40-60 mesh. The composition and specific surface area of the catalyst were shown in Table 1. The CO2 adsorption and thermal desorption test was carried out at 50-500°C by using the temperature programmed desorption method, and the desorption peak was shown in Figure 1, and the CO2 desorption amount of the catalyst in the temperature range of 150-400°C was calculated and shown in Table 1. Figure 1

[0131] (2) The activity evaluation and catalyst BET analysis of the prepared indium oxide catalyst were carried out on a fixed bed reactor, and the reaction conditions were the same as in Example 1, and the test results were shown in Table 2.

[0132] Comparative Example 2

[0133] (1) The preparation of the indium oxide catalyst was the same as in Comparative Example 1.

[0134] (2) 10 g of alumina (SB) powder was mixed with 5 g of magnesium oxide powder, and was dried at 60°C for 48 h, and finally was calcined at 800°C for 3 h to obtain the doped carrier precursor catalyst.

[0135] ​(3) 3.5 g of the active component precursor and 2.5 g of the carrier precursor were mixed and then put into a ball mill, the rotation speed of the ball mill was set to 300 rpm, and the ball milling time was 2 h; then the solid powder obtained after ball milling was calcined at 400 ℃ for 3 h to obtain an aluminum-doped indium oxide catalyst, which was pressed into tablets and sieved to 40-60 mesh. The composition, specific surface area data, and CO2 desorption amount in the temperature range of 150-400 ℃ of the catalyst are shown in Table 1.

[0136] The catalyst evaluation reaction conditions were the same as in Example 1, and the activity test results are shown in Table 2.

[0137] Comparative Example 3

[0138] (1) 4.2 g of P123 and 80 mL of anhydrous ethanol were mixed and dissolved under ultrasonic; then 6.4 mL of concentrated nitric acid was added, and after clarification, 5.0 g of aluminum isopropoxide and 3.1 g of magnesium nitrate were added; stirring was performed for 5 h, drying was performed at 60 ℃ for 48 h, and finally calcination was performed at 800 ℃ for 3 h to obtain a doped carrier.

[0139] (2) 5.37 g of In (NO3)3·4H2O was weighed and dissolved in 10 g of water, and then poured into a beaker containing 1 g of the doped carrier, stirred for 1 h, and then the water was evaporated using a rotary evaporator, dried in an oven at 120 ℃ for 12 h, and then calcined at 400 ℃ for 3 h to obtain a catalyst, which was pressed into tablets and sieved to 40-60 mesh. The composition, specific surface area, and CO2 desorption amount in the temperature range of 150-400 ℃ of the catalyst are shown in Table 1.

[0140] The catalyst evaluation reaction conditions were the same as in Example 1, and the activity test results are shown in Table 2.

[0141] Table 1

[0142]

[0143]

[0144] Table 2

[0145]

[0146] As can be seen from the results in Table 2, the magnesium-aluminum-doped indium oxide catalyst prepared by the preparation method provided in the present application has higher catalytic activity at lower temperature and pressure, higher CO2 conversion rate, and good methanol selectivity, compared with the catalysts prepared in Comparative Examples 1-3. As can be seen from Example 4, too long aging time is not conducive to improving the catalytic activity of the catalyst.

[0147] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that each technical feature is combined in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A magnesium-aluminum-doped indium oxide catalyst, characterized by, The catalyst comprises a carrier and an active component supported on the carrier; the active component is indium oxide, and the carrier comprises magnesium oxide and aluminum oxide; The content of indium oxide is 50-90wt%, the content of magnesium oxide is 2-20wt%, and the content of aluminum oxide is 8-40wt%, based on the total amount of the catalyst. The specific surface area of the catalyst is not less than 54 m 2 / g; the amount of CO2 desorbed from the catalyst in the temperature range of 150-400°C is not less than 500 pmol / g, as determined by temperature-programmed desorption. The magnesium-aluminum doped indium oxide catalyst is obtained by microwave-assisted hydrothermal synthesis.

2. The catalyst of claim 1, wherein, The content of indium oxide is 60-85wt%, based on the total amount of the catalyst.

3. The catalyst of claim 1, wherein, The specific surface area of the catalyst is 60-80 m 2 / g.

4. The catalyst of claim 1, wherein, The catalyst has a CO2 desorption amount of 500-1000µmol / g in the temperature range of 150-400℃, measured by temperature programmed desorption.

5. The catalyst of claim 1, wherein, The content of magnesium oxide is 5-15wt%, and the content of aluminum oxide is 10-35wt%, based on the total amount of the catalyst.

6. The catalyst of claim 1, wherein, In the carrier, the molar ratio of aluminum to magnesium is 1-5:1, on an elemental basis.

7. The catalyst of claim 6, wherein, In the carrier, the molar ratio of aluminum to magnesium is 1-3:1, on an elemental basis.

8. A method for producing the magnesium-aluminum-doped indium oxide catalyst as claimed in any one of claims 1 to 7, characterized in that The method comprises the following steps: (1) providing a solution A containing indium salt, magnesium salt and aluminum salt, and a solution B containing a precipitant; (2) mixing the solution A and the solution B to obtain a mother liquor C; (3) aging the mother liquor C under microwave reaction conditions; The microwave reaction conditions comprise a microwave output power of 500-2000W, a reaction temperature of 60-200℃, and an aging time of 0.5-24h; (4) performing solid-liquid separation on the product obtained in step (3), followed by drying and calcination to obtain the magnesium-aluminum doped indium oxide catalyst.

9. The production method according to claim 8, wherein The total concentration of the indium salt, the magnesium salt and the aluminum salt in the solution A is 0.1-5mol / L, on an elemental basis.

10. The production method according to claim 9, wherein The total concentration of the indium salt, the magnesium salt and the aluminum salt in the solution A is 0.5-2mol / L, on an elemental basis.

11. The production method according to claim 8, wherein The molar ratio of the aluminum salt to the magnesium salt is 1-5:1, on a metal element basis.

12. The method of making according to claim 11, wherein, The molar ratio of the aluminum salt to the magnesium salt is 1-3:1, on a metal element basis.

13. The method of making according to claim 8, wherein, The concentration of the solution B is 0.5-5mol / L.

14. The production method according to claim 13, wherein The concentration of the solution B is 1-3mol / L.

15. The method of making according to claim 8, wherein, The molar amount of the precipitant is 1-4 times the stoichiometric amount of metal atoms.

16. The method of making according to claim 8, wherein, The mixing in step (2) comprises adding the solution B to the solution A under stirring.

17. The method of making according to claim 16, wherein, The mixing conditions comprise a mixing temperature of 20-80℃.

18. The method of making according to claim 16, wherein, The addition rate of the solution B is 5-100mL / min.

19. The method of making according to claim 18, wherein, The addition rate of the solution B is 10-30mL / min.

20. The method of making according to claim 16, wherein, Stirring is required during the mixing process.

21. The method of manufacturing according to claim 8, wherein, The indium salt, the magnesium salt and the aluminum salt are soluble salts of indium, magnesium and aluminum.

22. The method of making according to claim 21, wherein, The indium salt, the magnesium salt and the aluminum salt are each independently selected from at least one of nitrate, acetate, sulfate and halide of indium, magnesium and aluminum.

23. The method of manufacturing according to claim 8, wherein, The precipitant is selected from at least one of ammonia, ammonium carbonate, ammonium bicarbonate, urea and citric acid.

24. The method of manufacturing according to claim 23, wherein, The precipitant is selected from at least one of urea, ammonium bicarbonate and ammonia.

25. The method of manufacturing according to claim 8, wherein, The solvent in the solution A and the solution B is each independently an organic solvent and / or water, and the organic solvent is selected from at least one of methanol, ethanol, isopropanol, ethylene glycol, triethylene glycol and N,N-dimethylacetamide.

26. The method of manufacturing according to claim 25, wherein, The solvent in the solution A and the solution B is independently an organic solvent and water.

27. The method of manufacturing according to claim 8, wherein, In step (2), the microwave reaction conditions include: microwave output power is 500-1500 W, reaction temperature is 80-160℃, and aging time is 0.5-8 h.

28. The method of manufacturing according to claim 8, wherein, In step (4), the drying conditions include: drying at 40-90℃ for 0.5-3 h.

29. The method of producing according to claim 8, wherein, In step (4), the calcination conditions include: calcination at 200-600℃ for 1-5 h.

30. The method of manufacturing according to claim 29, wherein, In step (4), the calcination conditions include: calcination at 300-500℃ for 2-4 h.

31. The method of manufacturing according to claim 8, wherein, The solution A further contains a template agent.

32. The method of manufacturing according to claim 31, wherein, The amount of the template agent is 0.01-1:1 relative to the total mass of the metal salt.

33. The method of manufacturing according to claim 31, wherein, The template agent is at least one selected from the group consisting of cetyltrimethylammonium bromide, polyoxyethylene-polyoxypropylene-polyoxyethylene amphiphilic block copolymer, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polyoxyethylene polyoxypropylene block polyether, polyethylene glycol, and polyoxyethylene ether.

34. A process for the production of methanol by the hydrogenation of carbon dioxide, the process comprising: Carbon dioxide and hydrogen are contacted in the presence of a catalyst under conditions for preparing methanol by hydrogenation of carbon dioxide; The catalyst includes the magnesium-aluminum-doped indium oxide catalyst according to any one of claims 1-7.

35. The method of claim 34, wherein, The conditions of the reaction for preparing methanol by carbon dioxide hydrogenation include: reaction pressure is 1-5 MPa, reaction temperature is 200-400℃, volume space velocity is 4500-18000h -1 , and H2 / CO2 molar ratio is 1-6.

36. The method of claim 34, wherein, The method further includes, before the contacting, pretreating the catalyst in the presence of a hydrogen-containing gas.

37. The method of claim 36, wherein, The conditions of the pretreatment include: the reaction pressure is 0.1-1 MPa, the reaction temperature is 200-400℃, the volume space velocity of the hydrogen-containing gas is 2000-8000h -1 .

38. The method of claim 37, wherein, The conditions of the pretreatment include: reaction temperature 300-400℃, volume space velocity of hydrogen-containing gas 4000-6000h -1 .

39. The method according to claim 36, wherein the hydrogen-containing gas contains hydrogen in an amount of 5-20 vol%.

40. The method according to claim 39, wherein the hydrogen-containing gas contains hydrogen in an amount of 8-12 vol%.

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