MoO3-Cu2O-WO3 / Mn2O3 catalyst and its preparation method and application

Abstract

The present invention discloses a MoO3-Cu2O-WO3 / Mn2O3 catalyst, its preparation method, and application, belonging to the field of catalyst technology. The technical solution includes the following steps: 1) Synthesis of a Mn2O3 carrier: Adding ammonia water to a hexahydrate manganese nitrate solution to induce precipitation, followed by calcination; 2) Preparation of MoO3 / Mn2O3: Adding Na2MoO4•2H2O, adding urea to react, and allowing to stand to obtain a precipitate; 3) Preparation of MoO3-Cu2O / Mn2O3: Dispersing MoO3 / Mn2O3 in water, adding copper acetate, evaporating to dryness, cooling, and drying; 4) Preparation of the MoO3-Cu2O-WO3 / Mn2O3 catalyst: Placing the catalyst and ammonia water in water, adding sodium tungstate dihydrate and a precipitant, and calcining the resulting solid to obtain the product. The preparation method of the present invention is simple and can be used to produce methanol from carbon dioxide hydrogenation, achieving high CO2 conversion and methanol yield.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to a MoO3-Cu2O-WO3 / Mn2O3 catalyst and a preparation method and application thereof. Background Art

[0002] Methanol, as an important chemical feedstock, can be used to synthesize chemicals such as dimethyl ether, olefins, and aromatics. It can also be used as a fuel or fuel additive, and is widely used in transportation and energy storage. However, due to the chemical stability of CO2, direct hydrogenation requires overcoming high activation energy, making catalyst design a key technology.

[0003] Carbon dioxide hydrogenation to methanol technology, which reacts carbon dioxide with hydrogen to produce methanol, not only helps reduce atmospheric carbon dioxide concentrations but also converts greenhouse gases into high-value chemical feedstocks or fuels. The research and application of this technology has garnered widespread attention worldwide, and the production of green methanol has become a key focus for low-carbon fuels and chemical feedstocks.

[0004] Existing catalysts generally include copper-based catalysts, oxide catalysts and precious metal catalysts. Copper-based catalysts are the most studied type of catalyst and are widely used in industrial production due to their good activity and selectivity. However, copper-based catalysts still have problems such as low CO2 conversion rate and unstable methanol selectivity. Oxide catalysts such as zinc-iron spinel oxide and indium oxide-based catalysts have received widespread attention in recent years. In2O3-based catalysts show high methanol selectivity in CO2 hydrogenation reactions due to their surface oxygen vacancy characteristics, but their conversion rate is still low. Therefore, it is necessary to develop a new catalyst for catalytic carbon dioxide hydrogenation to methanol with good catalytic activity, selectivity and stability and low cost. Summary of the Invention

[0005] The invention provides a MoO3-Cu2O-WO3 / Mn2O3 catalyst and a preparation method and application thereof. The preparation method is simple, pollution-free and industrializable, and is used for preparing methanol by hydrogenating carbon dioxide with a high conversion rate.

[0006] The technical solution of the present invention is:

[0007] In a first aspect, a method for preparing a MoO3-Cu2O-WO3 / Mn2O3 catalyst is disclosed, comprising the following steps:

[0008] 1) Synthesis of the Mn2O3 support: Ammonia was added to a solution of manganese nitrate hexahydrate to induce precipitation. The mixture was stirred at room temperature for 12-24 hours, filtered, washed, and dried. The precipitate was calcined to obtain the Mn2O3 support.

[0009] 2) Preparation of MoO3 / Mn2O3: Disperse the Mn2O3 carrier in water, add Na2MoO4•2H2O with stirring, continue stirring at room temperature for 2-4 hours, add urea as a precipitant, react at 80-100°C for 7-9 hours, and let stand at room temperature for 10-15 hours to obtain a precipitate. After filtering, washing, drying, and calcining in a muffle furnace, the precipitate is obtained to obtain the MoO3 / Mn2O3 catalyst.

[0010] 3) Preparation of MoO3-Cu2O / Mn2O3: MoO3 / Mn2O3 was dispersed in water, and copper acetate was added with stirring. After stirring at room temperature for 2-4 hours, the mixture was stirred in an oil bath at 80-100°C until evaporated to dryness. The mixture was then cooled to room temperature and calcined in a tubular furnace under nitrogen or helium to obtain the catalyst MoO3-Cu2O / Mn2O3.

[0011] 4) Preparation of MoO3-Cu2O-WO3 / Mn2O3 catalyst: MoO3-Cu2O / Mn2O3 and ammonia water are placed in water to form a mixed solution. Then, sodium tungstate dihydrate is added to the mixed solution, followed by precipitant thiourea. The mixture is stirred in a 60-100°C water bath for 6-12 hours, precipitated at room temperature for 12-24 hours, filtered, washed, and dried at 60-100°C for 8-16 hours. The resulting solid is ground to 300-500 μm, calcined under nitrogen or helium, ground to 100-200 μm, and calcined a second time to obtain the target product, MoO3-Cu2O-WO3 / Mn2O3 catalyst.

[0012] Preferably, the mass ratio of manganese nitrate hexahydrate, Na2MoO4•2H2O, copper acetate and sodium tungstate dihydrate is (35-40): (2-3): (3-5): 2.

[0013] Preferably, in step 1), the mass ratio of manganese nitrate hexahydrate to ammonia water is 1:(0.1-0.2), and in step 1), the drying is performed at 80-100° C. for 24-36 hours; and the calcination is performed at 500-600° C. for 2-4 hours.

[0014] Preferably, in step 2), the mass ratio of Na2MoO4•2H2O to urea is 1:(0.04-0.06); in step 2), the drying is performed at 80-100°C for 6-8 hours, and the calcination is performed at 400-500°C for 6-8 hours.

[0015] Preferably, the calcination in step 3) is carried out at 500-600° C. for 5-6 hours.

[0016] Preferably, the mass ratio of sodium tungstate dihydrate, thiourea and ammonia in step 4) is 1: (0.06-0.1): (0.03-0.06); the calcination in step 4) is carried out in a tubular furnace at 400-500° C. for 3-6 hours under a nitrogen or helium atmosphere; and the secondary calcination is carried out in a tubular furnace at 500-600° C. for 1-2 hours.

[0017] In the second aspect, a MoO3-Cu2O-WO3 / Mn2O3 catalyst prepared by a preparation method is disclosed.

[0018] In a third aspect, the use of the catalyst in catalytic hydrogenation of carbon dioxide to produce methanol is disclosed, comprising the following steps:

[0019] (1) Add 800 mg of MoO3-Cu2O-WO3 / Mn2O3 catalyst to a fixed-bed reactor and pretreat it with nitrogen at a flow rate of 100-200 mL / min for 30-60 min. Set the temperature of the preheater and the fixed-bed reactor to 100-200°C and 250-300°C, then heat and heat. Set the reaction pressure to 2-4 MPa.

[0020] (2) The raw gas is set to H2 and CO2, and the molar ratio of H2 and CO2 is (2.8-3.6):1, and the gas phase product methanol is obtained. The content of the product is analyzed online by gas chromatography-mass spectrometry.

[0021] The low methanol selectivity of conventional copper-based catalysts during CO2 hydrogenation is attributed to weak metal-support interactions and a dominant reverse water-gas shift reaction pathway. Mn2O3 loaded with MoO3, Cu2O, and WO3 enhances metal-support interactions and oxygen vacancies, addressing the issues of insufficient CO2 activation and H2 dissociation seen on conventional copper-based catalysts. By loading Mn2O3 with MoO3, Cu2O, and WO3, the enhanced oxygen vacancies and moderate basic sites suppress the reverse water-gas shift reaction pathway, favoring conversion to methanol. MoO3-Cu2O-WO3 / Mn2O3 enhances metal-support interactions, promoting oxygen vacancies and Cu2O dispersion. This dual optimization enhances CO2 adsorption, H2 dissociation, and methanol selectivity while suppressing CO byproducts.

[0022] During the reaction, H2 reduces some of the MoO3 and WO3 to MoO2 and WO2, which then activate CO2. The activated CO2 then accepts active hydrogen on the Cu2O surface and undergoes hydrogenation to produce methanol. The water generated during the reaction flows out along with the methanol and other gaseous products and then recondenses, promoting the forward reaction and improving methanol selectivity.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The preparation method of the MoO3-Cu2O-WO3 / Mn2O3 catalyst of the present invention has a simple process and the prepared catalyst can be recycled.

[0025] 2. The MoO3-Cu2O-WO3 / Mn2O3 catalyst prepared by the method of the present invention has a large specific surface area and many oxygen vacancies, which increases the catalytic effect.

[0026] 3. The MoO3-Cu2O-WO3 / Mn2O3 catalyst prepared by the present invention is used to produce methanol by hydrogenation of carbon dioxide with high conversion rate.

[0027] 4. The staged calcination process during catalyst preparation effectively regulates the morphology of the crystals, ensuring uniform distribution and a dense structure, thereby stabilizing the catalyst skeleton. This not only enhances the mechanical properties and thermal stability of the catalyst, but also provides more active sites for the reaction, resulting in higher catalytic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a scanning electron microscope image of the catalyst prepared in Example 1 of the present invention.

[0029] Figure 2 This is a morphology picture of the catalyst prepared in Example 1 of the present invention under a high-power microscope.

[0030] Figure 3 This is the XRD test pattern of the catalyst prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0032] Example 1

[0033] The MoO3-Cu2O-WO3 / Mn2O3 catalyst comprises a Mn2O3 carrier and loaded MoO3, Cu2O and WO3, wherein the loading amounts of MoO3, Cu2O and WO3 are 14wt%, 14wt% and 13wt% of the Mn2O3 carrier, respectively.

[0034] The preparation method of the MoO3-Cu2O-WO3 / Mn2O3 catalyst comprises the following steps:

[0035] 1) Synthesis of the Mn2O3 support: 38 g of manganese nitrate hexahydrate was added to 100 mL of water to form a solution, to which 5.7 g of aqueous ammonia was added to induce precipitation. The mixture was stirred at room temperature for 16 h, filtered, washed with distilled water and ethanol, and dried at 90°C for 30 h. The precipitate was calcined at 550°C for 3 h to obtain the Mn2O3 support.

[0036] 2) Preparation of MoO3 / Mn2O3: The Mn2O3 carrier was dispersed in 100 mL of water, 2.5 g of Na2MoO4·2H2O was added with stirring, and stirring was continued at room temperature for 3 h. 0.13 g of urea as a precipitant was added, and the mixture was reacted at 90°C for 8 h. The precipitate was allowed to stand at room temperature for 12 h to obtain a precipitate. After filtration, the precipitate was washed three times with deionized water, dried at 90°C for 7 h, and calcined in a muffle furnace at 450°C for 7 h to obtain the MoO3 / Mn2O3 catalyst.

[0037] 3) Preparation of MoO3-Cu2O / Mn2O3: MoO3 / Mn2O3 was dispersed in water, 4 g of copper acetate was added with stirring, and the mixture was stirred at room temperature for 3 h. The mixture was then stirred in a 90°C oil bath until evaporated to dryness. The mixture was then cooled to room temperature and calcined in a tubular furnace at 550°C for 5.5 h under nitrogen to obtain the MoO3-Cu2O / Mn2O3 catalyst.

[0038] 4) Preparation of MoO3-Cu2O-WO3 / Mn2O3 catalyst: MoO3-Cu2O / Mn2O3 and 0.1g ammonia water were placed in 100mL water to form a mixed solution. Then, 2g sodium tungstate dihydrate was added to the mixed solution, followed by 0.16g precipitant thiourea. The mixture was stirred in an 80℃ water bath for 8h, precipitated at room temperature for 15h, filtered, washed, and dried at 80℃ for 10h. The obtained solid was ground to 400μm, calcined in a tube furnace at 450℃ for 5h under nitrogen, ground to 150μm, and calcined again in a tube furnace at 550℃ for 1.5h to obtain the target product MoO3-Cu2O-WO3 / Mn2O3 catalyst. The scanning electron microscope morphology of the catalyst is shown in Figure 2. Figure 1 As shown in the figure, the morphology of the catalyst under high magnification is as follows Figure 2 As shown, it shows MoO3, Cu2O and WO3 phases supported on the Mn2O3 support, and the XRD pattern is as follows Figure 3 shown.

[0039] The application of the catalyst in catalytic carbon dioxide hydrogenation to produce methanol is as follows:

[0040] (1) 800 mg of MoO3-Cu2O-WO3 / Mn2O3 catalyst was added to the fixed-bed reactor and pretreated with nitrogen at a flow rate of 150 mL / min for 40 min. The temperature of the preheater and the fixed-bed reactor was set to 150 °C and 280 °C, respectively. The temperature was increased and the reaction pressure was set to 3 MPa.

[0041] (2) The raw gases were set to H2 and CO2, with the molar ratio of H2 to CO2 being 3:1, and methanol was obtained as a gas phase product. The content of the product was analyzed online by gas chromatography-mass spectrometry.

[0042] Example 2

[0043] The MoO3-Cu2O-WO3 / Mn2O3 catalyst comprises a Mn2O3 carrier and loaded MoO3, Cu2O and WO3, wherein the loading amounts of MoO3, Cu2O and WO3 are 12wt%, 11wt% and 15wt% of the Mn2O3 carrier, respectively.

[0044] The preparation method of the MoO3-Cu2O-WO3 / Mn2O3 catalyst comprises the following steps:

[0045] 1) Synthesis of the Mn2O3 support: 35 g of manganese nitrate hexahydrate was added to 100 mL of water to form a solution, to which 3.5 g of aqueous ammonia was added to induce precipitation. The mixture was stirred at room temperature for 12 h, filtered, washed with distilled water and ethanol, and dried at 80°C for 36 h. The precipitate was calcined at 500°C for 4 h to obtain the Mn2O3 support.

[0046] 2) Preparation of MoO3 / Mn2O3: The Mn2O3 carrier was dispersed in 100 mL of water. 2 g of Na2MoO4·2H2O was added with stirring. Stirring was continued at room temperature for 2 h. 0.08 g of urea (precipitant) was added and the mixture was reacted at 80°C for 9 h. The mixture was allowed to stand at room temperature for 10 h to obtain a precipitate. The precipitate was filtered, washed with deionized water, dried at 80°C for 8 h, and calcined in a muffle furnace at 400°C for 8 h to obtain the MoO3 / Mn2O3 catalyst.

[0047] 3) Preparation of MoO3-Cu2O / Mn2O3: MoO3 / Mn2O3 was dispersed in water, 3 g of copper acetate was added with stirring, and the mixture was stirred at room temperature for 2 h. The mixture was then stirred in an 80°C oil bath until evaporated to dryness. The mixture was then cooled to room temperature and calcined in a tubular furnace at 500°C for 6 h under helium to obtain the MoO3-Cu2O / Mn2O3 catalyst.

[0048] 4) Preparation of MoO3-Cu2O-WO3 / Mn2O3 catalyst: MoO3-Cu2O / Mn2O3 and 0.06 g of aqueous ammonia were placed in 100 mL of water to form a mixed solution. Then, 2 g of sodium tungstate dihydrate was added to the mixed solution, followed by a precipitant 0.12 g of thiourea. The mixture was stirred in a 60°C water bath for 12 h, precipitated at room temperature for 12 h, filtered, washed, and dried at 60°C for 16 h. The resulting solid was ground to 300 μm, calcined in a tube furnace at 400°C for 6 h under a helium atmosphere, ground to 100 μm, and calcined a second time in a tube furnace at 500°C for 2 h to obtain the target product, MoO3-Cu2O-WO3 / Mn2O3 catalyst.

[0049] The use of the catalyst in catalytic carbon dioxide hydrogenation to produce methanol comprises the following steps:

[0050] (1) 800 mg of MoO3-Cu2O-WO3 / Mn2O3 catalyst was added to the fixed-bed reactor and pretreated with nitrogen at a flow rate of 100 mL / min for 60 min. The temperature of the preheater and the fixed-bed reactor was set to 100 °C and 250 °C, respectively. The temperature was increased and the reaction pressure was set to 2 MPa.

[0051] (2) The raw gases were set to H2 and CO2, with the molar ratio of H2 to CO2 being 2.8:1, and methanol was obtained as a gas phase product. The content of the product was analyzed online by gas chromatography-mass spectrometry.

[0052] Example 3

[0053] The MoO3-Cu2O-WO3 / Mn2O3 catalyst comprises a Mn2O3 carrier and loaded MoO3, Cu2O and WO3, wherein the loading amounts of MoO3, Cu2O and WO3 are 16wt%, 16wt% and 13wt% of the Mn2O3 carrier, respectively.

[0054] The preparation method of the MoO3-Cu2O-WO3 / Mn2O3 catalyst comprises the following steps:

[0055] 1) Synthesis of Mn2O3 support: 40 g of manganese nitrate hexahydrate was added to 100 mL of water to form a solution, to which 8 g of aqueous ammonia was added to induce precipitation. The mixture was stirred at room temperature for 24 h, filtered, washed with distilled water and ethanol, and dried at 100°C for 24 h. The solution was then calcined at 600°C for 2 h to obtain the Mn2O3 support.

[0056] 2) Preparation of MoO3 / Mn2O3: The Mn2O3 carrier was dispersed in water, 3 g of Na2MoO4·2H2O was added with stirring, and stirring was continued at room temperature for 4 h. 0.18 g of urea as a precipitant was added, and the mixture was reacted at 100°C for 7 h. The precipitate was allowed to stand at room temperature for 15 h to obtain a precipitate. After filtration, the precipitate was washed three times with deionized water, dried at 100°C for 6 h, and calcined in a muffle furnace at 500°C for 6 h to obtain the MoO3 / Mn2O3 catalyst.

[0057] 3) Preparation of MoO3-Cu2O / Mn2O3: MoO3 / Mn2O3 was dispersed in water, 5 g of copper acetate was added with stirring, and the mixture was stirred at room temperature for 4 h. The mixture was then stirred in an oil bath at 100°C until evaporated to dryness. The mixture was then cooled to room temperature and calcined in a tube furnace at 600°C for 5 h under nitrogen to obtain the MoO3-Cu2O / Mn2O3 catalyst.

[0058] 4) Preparation of MoO3-Cu2O-WO3 / Mn2O3 catalyst: MoO3-Cu2O / Mn2O3 and 0.12 g of aqueous ammonia were placed in 100 mL of water to form a mixed solution. Then, 2 g of sodium tungstate dihydrate was added to the mixed solution, followed by 0.2 g of thiourea as a precipitant. The mixture was stirred in a 100°C water bath for 6 h, precipitated at room temperature for 24 h, filtered, washed, and dried at 100°C for 8 h. The resulting solid was ground to 500 μm, calcined in a tube furnace at 500°C for 3 h under a helium atmosphere, ground to 200 μm, and calcined a second time in a tube furnace at 600°C for 1 h to obtain the target product, MoO3-Cu2O-WO3 / Mn2O3 catalyst.

[0059] The use of the catalyst in catalytic carbon dioxide hydrogenation to produce methanol comprises the following steps:

[0060] (1) Add 800 mg of MoO3-Cu2O-WO3 / Mn2O3 catalyst into a fixed-bed reactor and pretreat with nitrogen at a flow rate of 200 mL / min for 30 min. Set the temperature of the preheater and the fixed-bed reactor to 200 °C and 300 °C, then heat and heat. Set the reaction pressure to 4 MPa.

[0061] (2) The raw gases were set to H2 and CO2, with the molar ratio of H2 to CO2 being 3.6:1, and methanol was obtained as a gas phase product. The content of the product was analyzed online by gas chromatography-mass spectrometry.

[0062] Comparative Example 1

[0063] The difference from Example 1 is that this comparative example does not include step 4), and the rest of the preparation method is the same as that of Example 1. That is, the catalyst does not contain WO3, and the catalyst MoO3-Cu2O / Mn2O3 is prepared.

[0064] Comparative Example 2

[0065] Different from Example 1, this comparative example does not contain Cu2O. The preparation method is as follows:

[0066] The preparation method of the MoO3-WO3 / Mn2O3 catalyst comprises the following steps:

[0067] 1) Synthesis of the Mn2O3 support: 38 g of manganese nitrate hexahydrate was dissolved in 100 mL of water to form a solution. 5.7 g of aqueous ammonia was added to induce precipitation. The mixture was stirred at room temperature for 16 h, filtered, washed with distilled water and ethanol, and dried at 90°C for 30 h. The precipitate was calcined at 550°C for 3 h to obtain the Mn2O3 support.

[0068] 2) Preparation of MoO3 / Mn2O3: The Mn2O3 carrier was dispersed in 100 mL of water, 2.5 g of Na2MoO4·2H2O was added with stirring, and stirring was continued at room temperature for 3 h. 0.13 g of urea as a precipitant was added, and the mixture was reacted at 90°C for 8 h. The precipitate was allowed to stand at room temperature for 12 h to obtain a precipitate. After filtration, the precipitate was washed three times with deionized water, dried at 90°C for 7 h, and calcined in a muffle furnace at 450°C for 7 h to obtain the MoO3 / Mn2O3 catalyst.

[0069] 3) Preparation of MoO3-WO3 / Mn2O3 catalyst: MoO3 / Mn2O3 and 0.1 g of aqueous ammonia were placed in 100 mL of water to form a mixed solution. 2 g of sodium tungstate dihydrate was then added to the mixed solution, followed by 0.16 g of thiourea as a precipitant. The mixture was stirred in an 80°C water bath for 8 h, precipitated at room temperature for 15 h, filtered, washed, and dried at 80°C for 10 h. The resulting solid was ground to 400 μm, calcined in a tubular furnace at 450°C for 5 h under nitrogen, ground to 150 μm, and calcined a second time in a tubular furnace at 550°C for 1.5 h to obtain the target product, MoO3-WO3 / Mn2O3 catalyst.

[0070] Comparative Example 3

[0071] The difference from Example 1 is that this comparative example does not contain MoO3. The preparation method is as follows:

[0072] The preparation method of the Cu2O-WO3 / Mn2O3 catalyst comprises the following steps:

[0073] 1) Synthesis of the Mn2O3 support: 38 g of manganese nitrate hexahydrate was added to 100 mL of water to form a solution, to which 5.7 g of aqueous ammonia was added to induce precipitation. The mixture was stirred at room temperature for 16 h, filtered, washed with distilled water and ethanol, and dried at 90°C for 30 h. The precipitate was calcined at 550°C for 3 h to obtain the Mn2O3 support.

[0074] 2) Preparation of Cu2O / Mn2O3: Mn2O3 was dispersed in 100 mL of water, and 4 g of copper acetate was added with stirring. The mixture was stirred at room temperature for 3 h, and then continued to stir in a 90°C oil bath until evaporated to dryness. The mixture was then cooled to room temperature and calcined in a tubular furnace at 550°C for 5.5 h under nitrogen to obtain the Cu2O / Mn2O3 catalyst.

[0075] 3) Preparation of Cu2O-WO3 / Mn2O3 catalyst: Cu2O / Mn2O3 and 0.1 g of aqueous ammonia were placed in 100 mL of water to form a mixed solution. 2 g of sodium tungstate dihydrate was then added to the mixed solution, followed by 0.16 g of thiourea as a precipitant. The mixture was stirred in an 80°C water bath for 8 h, precipitated at room temperature for 15 h, filtered, washed, and dried at 80°C for 10 h. The resulting solid was ground to 400 μm, calcined in a tube furnace at 450°C for 5 h under nitrogen, ground to 150 μm, and calcined a second time in a tube furnace at 550°C for 1.5 h to obtain the target product, Cu2O-WO3 / Mn2O3 catalyst.

[0076] Comparative Example 4

[0077] Unlike Example 1, step 4) of this comparative example does not include secondary calcination. Step 4) is: MoO3-Cu2O / Mn2O3 and 0.1g of ammonia water are placed in 100mL of water to form a mixed solution, and then 2g of sodium tungstate dihydrate is added to the mixed solution, followed by adding 0.16g of precipitant thiourea, and the mixture is stirred in an 80°C water bath for 8h, precipitated at room temperature for 15h, filtered, washed, and dried at 80°C for 10h. The obtained solid is ground to 400μm, calcined at 450°C in a tubular furnace under nitrogen for 5h, and ground to 150μm to obtain the target product MoO3-Cu2O-WO3 / Mn2O3 catalyst.

[0078] The steps for using the catalysts in Comparative Examples 1-4 in catalytic carbon dioxide hydrogenation to produce methanol are the same as those in Example 1, except that the catalysts prepared in the comparative examples are used.

[0079] The catalysts prepared in the above examples and comparative examples were subjected to performance tests, and the test results are shown in Table 1.

[0080] Table 1 Test results

[0081]

[0082] The performance of the catalysts prepared in the above examples and comparative examples for catalyzing the production of methanol from carbon dioxide is shown in Table 2. The CO2 conversion rate ( ), the selectivity of methanol (S) is calculated according to the following formula:

[0083]

[0084] .

[0085] Table 2 Performance evaluation of catalysts for methanol production

[0086]

[0087] As shown in Table 2, the absence of WO3 in Comparative Example 1 reduces the oxygen vacancy concentration on the catalyst surface, weakening the CO2 adsorption activation ability and reducing the conversion rate. WO3 also provides moderate alkaline sites, inhibiting the reverse water-gas shift reaction (RWGS: CO2 + H2 → CO + H2O). Its absence exacerbates side reactions, increasing CO byproducts and reducing methanol selectivity.

[0088] Comparative Example 2: After the lack of Cu2O, H2 cannot be effectively dissociated into active hydrogen, the hydrogenation step is hindered, resulting in a sharp drop in the CO2 conversion rate, the MoO3-Cu2O interface promotes the formation of oxygen vacancies, and the lack of Cu2O weakens the overall synergistic effect.

[0089] Comparative Example 3 does not contain MoO3, and the catalyst is easily sintered during high-temperature reaction, resulting in a reduction in active sites. At the same time, it may lead to excessive alkalinity, promote RWGS side reactions, and reduce methanol selectivity.

[0090] In Comparative Example 4, there is no secondary calcination, which affects the mechanical strength and thermal stability of the structure. The catalyst is prone to structural collapse and active site failure in high temperature and high pressure reactions.

[0091] For the catalyst prepared in Example 1, after the reaction was completed, nitrogen was introduced to exhaust the gas in the reactor, and then oxygen was introduced into the fixed bed. The fixed bed reactor was set to a temperature of 300°C for 3 hours, and then cooled to room temperature for use in the next experiment. The catalyst prepared in Example 1 was cycled 10 times. The cycle performance of catalyzing carbon dioxide to produce methanol is shown in Table 3.

[0092] Table 3 Cyclic performance results

[0093]

[0094] As can be seen from the table, the catalyst prepared by the present invention can be recycled, and the catalytic performance of the recycled catalyst remains good. With the increase of the number of cycles, the CO2 conversion rate and methanol selectivity are relatively stable.

Claims

1. A method for preparing a MoO3-Cu2O-WO3 / Mn2O3 catalyst, characterized in that: The following steps are involved: 1) Synthesis of the Mn2O3 support: Ammonia was added to a solution of manganese nitrate hexahydrate to induce precipitation. The mixture was stirred at room temperature for 12-24 hours, filtered, washed, and dried. The precipitate was calcined to obtain the Mn2O3 support. 2) Preparation of MoO3 / Mn2O3: Disperse the Mn2O3 carrier in water, add Na2MoO4•2H2O with stirring, continue stirring at room temperature for 2-4 hours, add urea as a precipitant, react at 80-100°C for 7-9 hours, and let stand at room temperature for 10-15 hours to obtain a precipitate. After filtering, washing, drying, and calcining in a muffle furnace, the precipitate is obtained to obtain the MoO3 / Mn2O3 catalyst. 3) Preparation of MoO3-Cu2O / Mn2O3: MoO3 / Mn2O3 was dispersed in water, and copper acetate was added with stirring. After stirring at room temperature for 2-4 hours, the mixture was stirred in an oil bath at 80-100°C until evaporated to dryness. The mixture was then cooled to room temperature and calcined in a tubular furnace under nitrogen or helium to obtain the catalyst MoO3-Cu2O / Mn2O3. 4) Preparation of MoO3-Cu2O-WO3 / Mn2O3 catalyst: MoO3-Cu2O / Mn2O3 and ammonia water are placed in water to form a mixed solution. Then, sodium tungstate dihydrate is added to the mixed solution, followed by precipitant thiourea. The mixture is stirred in a 60-100°C water bath for 6-12 hours, precipitated at room temperature for 12-24 hours, filtered, washed, and dried at 60-100°C for 8-16 hours. The resulting solid is ground to 300-500 μm, calcined under nitrogen or helium, ground to 100-200 μm, and calcined a second time to obtain the target product, MoO3-Cu2O-WO3 / Mn2O3 catalyst.

2. The method for preparing the MoO3-Cu2O-WO3 / Mn2O3 catalyst according to claim 1, wherein The mass ratio of manganese nitrate hexahydrate, Na2MoO4•2H2O, copper acetate and sodium tungstate dihydrate is (35-40): (2-3): (3-5):

2.

3. The method for preparing the MoO3-Cu2O-WO3 / Mn2O3 catalyst according to claim 1, wherein In step 1), the mass ratio of manganese nitrate hexahydrate to ammonia water is 1:(0.1-0.2). In step 1), the drying step is performed at 80-100° C. for 24-36 hours; and the calcination step is performed at 500-600° C. for 2-4 hours.

4. The method for preparing the MoO3-Cu2O-WO3 / Mn2O3 catalyst according to claim 1, wherein In step 2), the mass ratio of Na2MoO4•2H2O to urea is 1:(0.04-0.06); in step 2), the drying is performed at 80-100°C for 6-8 hours, and the calcination is performed at 400-500°C for 6-8 hours.

5. The method for preparing the MoO3-Cu2O-WO3 / Mn2O3 catalyst according to claim 1, wherein In step 3), the calcination is carried out at 500-600° C. for 5-6 hours.

6. The method for preparing the MoO3-Cu2O-WO3 / Mn2O3 catalyst according to claim 1, wherein In step 4), the mass ratio of sodium tungstate dihydrate, thiourea and ammonia water is 1: (0.06-0.1): (0.03-0.06); the calcination in step 4) is carried out in a tubular furnace at 400-500° C. for 3-6 hours under a nitrogen or helium atmosphere; the secondary calcination is carried out in a tubular furnace at 500-600° C. for 1-2 hours.

7. A MoO3-Cu2O-WO3 / Mn2O3 catalyst prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the catalyst according to claim 7 in catalytic carbon dioxide hydrogenation to produce methanol, characterized in that: The following steps are involved: (1) Add 800 mg of MoO3-Cu2O-WO3 / Mn2O3 catalyst to a fixed-bed reactor and pretreat it with nitrogen at a flow rate of 100-200 mL / min for 30-60 min. Set the temperature of the preheater and the fixed-bed reactor to 100-200°C and 250-300°C, then heat and heat. Set the reaction pressure to 2-4 MPa. (2) The raw gas is set to H2 and CO2, and the molar ratio of H2 and CO2 is (2.8-3.6):1, and the gas phase product methanol is obtained. The content of the product is analyzed online by gas chromatography-mass spectrometry.

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