Catalyst suitable for preparing methanol through carbon dioxide hydrogenation and preparation method thereof

Abstract

The invention discloses a catalyst applicable to preparation of methanol by hydrogenation of carbon dioxide and a preparation method of the catalyst, relates to the technical field of hydrogenation catalysts, and aims to solve the problems that active sites are few and sintering is easy at high temperature. The preparation method comprises the following steps: taking a Fe and Zn doped metal precursor and a main body Zr precursor as raw materials, preparing a gel catalyst intermediate product through a sol-gel method, carrying out supercritical drying, and then carrying out high-temperature calcination to prepare the Fe-Zn co-doped ZrO2 catalyst, and the activity of the Fe-Zn co-doped ZrO2 catalyst comes from rich oxygen vacancies and asymmetric active sites brought by metal doping; according to the invention, asymmetric active sites are constructed through metal doping to activate CO2, the prepared catalyst can realize more efficient reaction for preparing methanol through carbon dioxide hydrogenation at high space velocity in a high-temperature region, and the space-time rate of methanol can be directly increased by one order of magnitude.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogenation catalysts, and in particular to a catalyst suitable for producing methanol by hydrogenating carbon dioxide and a preparation method thereof. Background Art

[0002] As one of the Sustainable Development Goals (SDGs), ensuring that humans have access to sustainable, reliable and affordable modern energy has received increasing attention. Carbon dioxide (CO2), as a carbon-containing substance, is a major greenhouse gas. Its excessive emissions have led to global climate change and have become one of the major challenges facing human society. In addition, carbon dioxide is also an important carbon source. Its efficient conversion into zero-carbon chemicals is an important supplement to fossil resources. The hydrogenation of CO2 into methanol (CO2+3H2→CH3OH+H2O) provides a catalytic method to alleviate the excessive emission of CO2. The conversion of CO2 into methanol can not only effectively alleviate the greenhouse effect, but also realize the recycling of carbon resources, which has important sustainable development significance. Therefore, the development of efficient and stable CO2 hydrogenation to methanol catalyst has important scientific value and practical application prospects.

[0003] At present, the commercial low-temperature catalyst is copper / zinc oxide / aluminum oxide (Cu / ZnO / Al2O3). However, CO2 molecules are highly stable, and their activation and conversion require efficient catalysts. Traditional Cu / ZnO / Al2O3 catalysts show good methanol selectivity at low temperatures, but are easily deactivated at high temperatures, limiting their industrial applications. ZrO2 has abundant surface oxygen vacancies and acid-base bifunctional properties, which can effectively adsorb and activate CO2 molecules. ZrO2 catalysts show certain performance in the CO2 hydrogenation to methanol reaction in the high temperature zone (250-400 ℃). The pure ZrO2 catalyst has fewer active sites and is easy to sinter at high temperatures, so the catalytic performance is low. Therefore, a catalyst suitable for the hydrogenation of carbon dioxide to methanol and its preparation method are urgently needed to solve this problem. Summary of the invention

[0004] The object of the present invention is to provide a catalyst suitable for producing methanol by hydrogenation of carbon dioxide and a preparation method thereof, so as to solve the problem of having fewer active sites and being easy to sinter at high temperature.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical scheme: a method for preparing a catalyst suitable for hydrogenating carbon dioxide to methanol, comprising using Fe, Zn doped metal precursors and a main Zr precursor as raw materials, preparing a gel catalyst intermediate by a sol-gel method, and obtaining a Fe-Zn co-doped ZrO2 catalyst by high-temperature calcination after supercritical drying, the activity of which comes from the abundant oxygen vacancies and asymmetric active sites brought by metal doping.

[0006] Preferably, the preparation method comprises the following specific contents: the Fe and Zn doped metal precursors in the raw materials are Fe and Zn nitrates, the Zr precursor is selected from zirconium oxynitrate and zirconium carbonate, the molar ratio of Zr:Zn:Fe in the raw materials is (5-10):1:(0.01-1), the raw materials are added to the dispersant and stirred to dissolve, and the gelling agent is added and stirred to a gel state; the wet gel is sealed in an autoclave and supercritically dried, and the dried solid is calcined at high temperature to obtain a metal-doped ZrO2 catalyst.

[0007] Preferably, the dispersant is a mixed solvent of ethanol and water, the volume concentration of ethanol is 20%-100%, the ratio of the total amount of metal substances of doped metal and Zr to the amount of dispersant is 1 mol:500-700 ml, and the gelling agent is a mixture of propylene oxide, formamide and acetic acid, and the molar ratio of the three is 1:(0.06-0.1):(0.08-0.12).

[0008] Preferably, the specific operating conditions of the supercritical drying are: the pressure in the autoclave is maintained at about 6-8 MPa, the autoclave is heated to 90-280°C and maintained for 1-5 h; the temperature of the high-temperature calcination is 400-600°C, and the insulation time is 1-5 h.

[0009] Preferably, at least one of the doping metal type, sol-gel method and supercritical drying in the above preparation method is replaced: the doping metal is replaced with any one of Cr, Ce, Ga, In, Cd, Zn, and Fe, and the molar ratio of Zr to the doping metal is 5-10:1; the sol-gel method is replaced with one of a coprecipitation method, a hydrothermal method, and a calcination method, and when replaced with the calcination method, no calcination is performed after drying; supercritical drying is replaced with one of ordinary drying, vacuum drying, and freeze drying.

[0010] Preferably, in the above preparation method:

[0011] The hydrothermal method is to dissolve the doped metal precursor and the Zr precursor in water, then gradually add the (NH4)2CO3 solution to the solution, then transfer the mixture to a reactor, perform a hydrothermal reaction at 160-200 °C for 10 h and then dry;

[0012] The calcination method is to grind the doped metal precursor and the Zr precursor solid, then calcine at 500-700 °C for 4 h, wash with distilled water and collect by filtration to be dried;

[0013] The co-precipitation method is to dissolve the doped metal precursor and the Zr precursor in an ethanol aqueous solution and heat it to prepare solution A, dissolve (NH4)2CO3 in water to obtain solution B, and add solutions A and B to a beaker at the same time. The co-precipitation operation is carried out in a 70°C water bath. The pH value of the mixed solution is adjusted to 9 to 10. After aging at room temperature for 6 hours, the precipitate is collected by centrifugation or filtration for drying.

[0014] Another technical solution provided by the present invention is a catalyst suitable for producing methanol by hydrogenating carbon dioxide, which is prepared by the above-mentioned preparation method.

[0015] Another technical solution provided by the present invention is the use of the above catalyst suitable for producing methanol by hydrogenating carbon dioxide in the reaction of producing methanol by hydrogenating carbon dioxide.

[0016] Preferably, at 5.0 MPa, 24000 mL g cat -1 h -1 , 300 ° C, the methanol selectivity on the catalyst exceeds 80%; at 5.0 MPa, 36000 ml g cat -1 h -1 Under the conditions of 360°C, the methanol space-time yield on the catalyst can exceed 180 g / kg cat ∙h -1 .

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The catalyst suitable for the hydrogenation of carbon dioxide to methanol and its preparation method adopt the sol-gel method combined with supercritical drying technology to synthesize the ZrO2-based composite aerogel catalyst; the study found that by doping metals into ZrO2 aerogels and constructing asymmetric sites, its surface electronic structure can be regulated, the oxygen vacancy concentration can be increased, and the thermal stability can be improved, thereby significantly enhancing its performance in catalyzing the hydrogenation of CO2 to methanol. Among them, the Fe and Zn metal-doped aerogel catalysts can achieve a more efficient reaction of hydrogenation of carbon dioxide to methanol at high space velocity in high temperature zones. By constructing asymmetric active sites by metal doping to activate CO2, the methanol space velocity of the aerogel catalyst can be directly increased by an order of magnitude.

[0019] 2. The catalyst suitable for producing methanol by hydrogenation of carbon dioxide and its preparation method significantly improves the specific surface area and pore volume of the FeZn co-doped ZrO2 catalyst through the hyperlink drying method, which further facilitates the reaction of producing methanol by hydrogenation of carbon dioxide.

[0020] 3. The metal doping strategy proposed in the catalyst suitable for hydrogenation of carbon dioxide to methanol and its preparation method provides inspiration for the design of aerogel catalysts for converting CO2 through asymmetric site activation, and also shows broad prospects for the industrial application of aerogel catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The XRD pattern of ZrO2 obtained in Example 1;

[0022] Figure 2 XRD patterns of some metal-doped ZrO2 obtained in Examples 2 and 3;

[0023] Figure 3 XRD patterns of FeZn-ZrO2 with different doping ratios synthesized by sol-gel method combined with supercritical drying in Example 4. For specific ratios, see Table 1;

[0024] Figure 4 This is the TEM image of 2FeZn-ZrO2 prepared in Example 4.

[0025] Figure 5 These are the EPR images of Zn co-doped ZrO2 prepared in Example 2, ZrO2 prepared in Example 1, and 2FeZn-ZrO2 prepared in Example 4. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters for implementation. It is particularly important to point out that all similar replacements and modifications are obvious to those skilled in the art, and they all fall within the scope of protection of the present invention. The methods and applications of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications of this article without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0027] Efficient catalysts are the key to improving CO2 conversion and methanol selectivity. Traditional Cu / ZnO / Al2O3 catalysts show good methanol selectivity at low temperatures, but are easily deactivated at high temperatures, limiting their industrial applications. ZrO2 catalysts show certain performance in the CO2 hydrogenation to methanol reaction in the high temperature range (250-400°C). However, pure ZrO2 catalysts have fewer active sites and are easily sintered at high temperatures, so their catalytic performance is relatively low.

[0028] Therefore, in view of the deficiencies in the prior art, the present invention provides a metal co-doped ZrO2 catalyst, specifically a Zn and Fe co-doped ZrO2 catalyst;

[0029] The optimal preparation method can be summarized as using the sol-gel method, adding Zn, Fe, and Zr precursors to the system at the same time, and combining supercritical drying technology to synthesize ZnFe co-doped ZrO2 catalyst. The obtained catalyst is recorded as FeZn-ZrO2 catalyst;

[0030] The present invention is further described in detail by several examples. The experimental raw materials used in the following examples of the present invention are all common commercial products.

[0031] Example 1

[0032] First, 10.7 g of Zr(NO3)2∙2H2O was dissolved in a mixed solution of 325 mL of ethanol solution and 75 mL of water. After stirring at room temperature for 1 hour, 1.8 g of formamide, 30.2 g of propylene oxide, and 2.7 g of acetic acid were added to the mixture in sequence. The mixed solution was stirred continuously again until it became a gel. The wet gel was sealed into an autoclave, and supercritical CO2 flowed into the autoclave through a high-pressure pump, and the pressure in the autoclave was maintained at about 7.5 MPa. The autoclave was then heated to 260°C and maintained for 1 h for CO2 supercritical drying. The dried solid was calcined at 550°C for 5 h, and the resulting catalyst was a ZrO2 catalyst.

[0033] Example 2

[0034] Based on the method of Example 1, a certain amount of Zn(NO3)2 and Zr(NO3)2∙2H2O were simultaneously dissolved in a mixed solution of 325 mL of ethanol solution and 75 mL of water. After stirring at room temperature for 1 hour, 1.8 g of formamide, 30.2 g of propylene oxide and 2.7 g of acetic acid were added to the mixture in sequence. The mixed solution was stirred again until it became a gel; the molar ratio of Zr to Zn was 8:1, and the Zn-doped ZrO2 catalyst was obtained after supercritical drying and calcination.

[0035] Example 3

[0036] A certain amount of M(NO3)2 and Zr(NO3)2∙2H2O were simultaneously dissolved in a mixed solution of 325 mL of ethanol solution and 75 mL of water. After stirring at room temperature for 1 hour, 1.8 g of formamide, 30.2 g of propylene oxide and 2.7 g of acetic acid were added to the mixture in sequence. The mixed solution was stirred again until it became a gel; M was Ce, Ga, In, Cd or Fe; the molar ratio of Zr to M was 8:1, and the M-doped ZrO2 catalyst was obtained after supercritical drying and calcination.

[0037] Example 4

[0038] In this example, 4 groups of catalysts were prepared in parallel. The preparation process of the first group was as follows:

[0039] A certain amount of Fe(NO3)2∙9H2O, Zn(NO3)2 and Zr(NO3)2∙2H2O were dissolved in a mixed solution of 325 mL ethanol solution and 75 mL water. The molar ratio of Zr: Zn: Fe was 8:1:0.25, and the total amount of metal substances did not exceed 0.8 mol. After stirring at room temperature for 1 hour, 1.8 g formamide, 30.2 g propylene oxide and 2.7 g acetic acid were added to the mixture in sequence. The mixed solution was stirred again until it became a gel; after supercritical drying and calcination, the Fe-Zn co-doped ZrO2 catalyst was obtained, which was labeled as 2FeZn-ZrO2.

[0040] In the other two groups, the molar ratio of Zr: Zn: Fe was adjusted, and the remaining steps were the same as the first group. The products were labeled 1FeZn-ZrO2 and 3FeZn-ZrO2, respectively. The specific adjusted results are shown in Table 1.

[0041] The last group was prepared into gels using the same protocol as the first group, but the drying step was replaced by vacuum drying at 70 °C overnight, followed by calcination to obtain the catalyst product.

[0042] Example 5

[0043] A certain amount of ZrO(NO3)2∙2H2O, Fe(NO3)2∙9H2O and Zn(NO3)2 were dissolved in 45 mL of water. The molar ratio of Zr:Zn:Fe was 8:1:0.25, but the amount of total metal substances did not exceed 0.8 mol. Then a certain amount of 1 M (NH4)2CO3 solution was gradually added dropwise to the above solution to adjust the pH value to 9-10. The mixture was then transferred to a reactor and subjected to a hydrothermal reaction at 180°C for 10 hours. After centrifugation and washing, the product was vacuum dried at 70°C overnight and calcined at 550°C for 5 h. Fe-Zn co-doped ZrO2 catalyst was obtained.

[0044] The specific temperature of the hydrothermal method can be selected to be 160-200°C.

[0045] Example 6

[0046] A certain amount of ZrO(NO3)2∙2H2O and Fe(NO3)2∙9H2O, Zn(NO3)2 solid was ground. The molar ratio of Zr: Zn: Fe was 8:1:0.25. Subsequently, after calcination at 600℃ for 4h, it was washed with distilled water and collected by filtration. After drying overnight, Fe-Zn co-doped ZrO2 catalyst was obtained.

[0047] In the calcination method, the specific calcination temperature can be selected to be 500-700°C.

[0048] Example 7

[0049] 0.08 mol ZrO(NO3)2∙2H2O and a certain amount of Fe(NO3)2∙9H2O and Zn(NO3)2 were dissolved in 90 mL water at the same time, and the molar ratio of Zr:Zn:Fe was 8:1:0.25, which was solution A. Subsequently, 0.2 mol (NH4)2CO3 was dissolved in 200 mL water to obtain solution B. Solutions A and B were added dropwise to a beaker at the same time, and a coprecipitation operation was performed under a 70-degree water bath condition. The pH value of the mixed solution was adjusted to about 9 to 10. After aging at room temperature for 6 hours, the precipitate was collected by centrifugation or filtration. The product was dried overnight in supercritical ethanol at 260°C and calcined at 550°C for 5 h. The coprecipitated Fe-Zn co-doped ZrO2 catalyst was obtained.

[0050] Except for the calcination method of Example 6, the temperature of the high-temperature calcination after drying can be selected to be 400-600° C., and the insulation time is preferably 1-5 h.

[0051] The ZrO2 aerogel catalyst exhibits a tetragonal and monoclinic mixed crystalline structure ( Figure 1 ). After the introduction of metal doping, the diffraction peak of the monoclinic phase began to disappear. Zn-ZrO2 aerogel is still composed of tetragonal and monoclinic phase structures ( Figure 2 ). However, only tetragonal phase was observed in ZrO2 aerogels doped with Ce, In, Cd, Ce, etc. The bonding of monoclinic phase is stronger than that of tetragonal phase, so tetragonal ZrO2 is more conducive to CO2 activation. In order to further enrich the defects, Zn-ZrO2 aerogel was further doped with iron, and FeZn co-doped ZrO2 aerogel only showed tetragonal phase structure ( Figure 3 ). In addition, XRF measurements also showed the content of each element in the aerogel catalyst (Table 1)

[0052] And the introduction of iron and zinc can further increase the specific surface area of ​​the aerogel catalyst (Table 2). In terms of synthesis methods, the supercritical drying method significantly improves the specific surface area and pore volume of the FeZn co-doped ZrO2 catalyst (Table 3), and the catalyst prepared by the sol-gel method is significantly better than other methods; for reference, the specific operating conditions of supercritical drying in the present invention can be selected as follows: the pressure in the autoclave is maintained at about 6-8 MPa, and the autoclave is heated to 90-280°C and maintained for 1-5 h.

[0053] The oxygen vacancy content in the aerogel catalyst was directly determined by monitoring the unpaired electrons absorbed on the oxygen vacancies through EPR measurement. Figure 4 ). The EPR intensity of FeZn co-doped ZrO2 aerogel is the strongest. This indicates that the doping treatment has a positive effect on the formation of oxygen vacancies.

[0054] Table 1. Content of each element in the aerogel catalyst measured by XRF

[0055]

[0056] Table 2. Catalyst specific surface area test results

[0057]

[0058] Table 3. Test results of specific surface area of ​​catalysts using different synthesis methods

[0059]

[0060] CO2 hydrogenation performance test:

[0061] Methanol synthesis by hydrogenation of carbon dioxide to methanol was carried out in a continuous fixed-bed reactor at 360 °C, 5.0 MPa and 24000 mL g cat -1 h -1 The catalytic performance of the metal-doped ZrO2 catalyst was tested under the following conditions. As shown in Table 4, the ZrO2 catalyst showed a CO2 conversion rate of 4.4%, and the product was mainly CO, accounting for 82% of all products. The ZrO2 catalyst doped with Ce, Ga, In, Cd, Zn, etc., while maintaining the stability of the ZrO2 phase, broke the symmetric Zr-O bond on the surface of ZrO2, providing sites for the activation of CO2. After the introduction of metal doping, the CO2 conversion rate was significantly improved, and the CO ratio began to decrease. Compared with the ZrO2 catalyst, the rich asymmetric sites of the catalyst after metal doping played an important role in the activation of carbon dioxide, and the conversion capacity of carbon dioxide was significantly improved.

[0062] Among them, Zn-ZrO2 achieved a CO2 conversion rate of 10.7% and a methanol selectivity of 39.8%. In order to further enrich the asymmetric active sites and reduce the CO ratio in the product, iron was further doped on the basis of Zn-ZrO2. The introduction of iron and zinc directly enhanced the adsorption capacity of the catalyst for CO2. In addition, the performance of FeZn-ZrO2 synthesized by different synthesis methods was tested (Table 5). In Example 4, 2FeZn-ZrO2 synthesized by sol-gel method combined with supercritical drying had the highest CO2 conversion rate and methanol selectivity.

[0063] Table 4. Activity test results of ZrO2 catalysts doped with different metals

[0064]

[0065] Table 5. Activity test results of FeZn-ZrO2 catalysts synthesized by different methods

[0066] Fe and Zn are evenly dispersed in ZrO2 nanocrystals, and the asymmetric active center constructed by bimetallic doping is used to efficiently convert carbon dioxide into methanol. With the introduction of iron, the CO selectivity of the FeZn co-doped ZrO2 catalyst decreased significantly. The CO2 conversion rate of the 2FeZn-ZrO2 catalyst was further improved to 11.4%, and the methanol selectivity reached 51.2%. Its methanol space-time yield (STY) also increased accordingly, reaching 135.98 g / kg cat ∙h -1 (Table 6).

[0067] At 5.0 MPa and 24000 mL g cat -1 h -1 The ability of 2FeZn-ZrO2 to produce methanol from CO2 hydrogenation at different temperatures under different conditions. With the increase of temperature, the CO2 conversion rate and CO selectivity on the catalyst are gradually improved. At 360℃, the methanol space-time yield (STY) is the highest, which is 135.98 g / kg cat ∙h -1 The methanol selectivity on 2FeZn-ZrO2 catalyst can reach up to 81.9% at 300℃. The methanol space-time yield (STY) is volcanic (Table 7).

[0068] Table 6. Activity test results of FeZn-ZrO2 catalysts with different element ratios

[0069]

[0070] Table 7. Activity test results of 2FeZn-ZrO2 catalyst at different temperatures

[0071]

[0072] The activity comparison of FeZn-ZrO2 aerogel at different space velocities at 360℃ and 5.0 MPa is shown in Table 8. With the increase of space velocity, the CO2 conversion rate on the aerogel catalyst decreases. However, the methanol selectivity and space-time yield (STY) first increase and then decrease with the increase of space velocity. cat -1 h -1 At the same time, the CO selectivity was further reduced to 41.3% and the methanol selectivity was 56.5. The FeZn-ZrO2 aerogel catalyst had the highest methanol space-time yield (STY), which was 187.15 g / kg. cat ∙h -1(Table 8) The metal-doped ZrO2 aerogel catalyst with abundant asymmetric active sites has obvious advantages in the methanol synthesis reaction.

[0073] Table 8. Activity test results of 2FeZn-ZrO2 catalysts at different space velocities

[0074]

[0075] The metal co-doped ZrO2 catalyst provided by the present invention uses co-doping to introduce metals to synthesize the catalyst. Studies have found that this strategy is conducive to the generation of asymmetric sites, and a large number of asymmetric active sites on the catalyst are conducive to the activation of CO2 to promote the formation and conversion of HCOO* and COOH* intermediates during the synthesis of CH3OH. By doping metals into ZrO2 and constructing asymmetric sites, its surface electronic structure can be regulated, the oxygen vacancy concentration can be increased, and the thermal stability can be improved, thereby significantly enhancing its performance in catalyzing CO2 hydrogenation to methanol.

[0076] By constructing asymmetric active sites for CO2 activation by metal doping, the methanol hourly space velocity of the aerogel catalyst can be directly increased by an order of magnitude. The performance of each FeZn-ZrO2 gel catalyst synthesized by the method in Example 4 is more outstanding, especially on 2FeZn-ZrO2 synthesized by sol-gel method combined with supercritical drying in Example 4 with abundant asymmetric active sites. When reacting at 300°C, CO selectivity is as low as 17.7%, and methanol selectivity is as high as 81.9%. At the same time, at high temperature (360°C), ultra-high space velocity (36000 ml g cat -1 h -1 )The aerogel catalyst has excellent stability while maintaining ultra-high activity.

[0077] In addition, in addition to the methods mentioned in the above embodiments, one or more of the three types of doped metals, sol-gel method and supercritical drying in the preparation method of the present invention can be replaced. For example, the doped metal is any one of Cr, Ce, Ga, In, Cd, Zn, and Fe, and the molar ratio of Zr to the doped metal is 5-10:1. Of course, any two of the above metals can be selected as co-doped metals. Regardless of the type of doped metal, the above-mentioned sol-gel method, coprecipitation method, hydrothermal method, and calcination method can be used, and supercritical drying, ordinary drying, vacuum drying, freeze drying, etc. can also be used. The catalyst obtained after replacement still complies with the metal doping strategy proposed in the present invention, that is, rich oxygen vacancies and asymmetric active sites are brought about by metal doping.

[0078] Furthermore, in the present invention, the gel catalyst FeZn-ZrO2 prepared by co-doping Zn and Fe, sol-gel method and supercritical drying has more outstanding performance; for reference, in this preferred method, the dispersant can be a mixed solvent of ethanol and water, the volume concentration of ethanol can be selected to be 20-100%, the total amount of metal substances doped with metal and Zr and the amount of dispersant can be 1 mol:500-700 ml, and the gelling agent used is a mixture of propylene oxide, formamide and acetic acid, and the molar ratio of the three is 1:(0.06-0.1):(0.08-0.12).

[0079] The above are only preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope defined by the claims.

[0080] The matters not described in detail in the present invention are all known technologies to those skilled in the art.

Claims

1. A method for preparing a catalyst suitable for hydrogenating carbon dioxide to methanol, characterized in that: The method includes using Fe and Zn doped metal precursors and main Zr precursors as raw materials, preparing a gel catalyst intermediate by a sol-gel method, and then supercritical drying and high-temperature calcination to obtain a Fe-Zn co-doped ZrO2 catalyst, the activity of which comes from the abundant oxygen vacancies and asymmetric active sites brought by metal doping.

2. The method for preparing a catalyst suitable for producing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The preparation method comprises the following specific contents: Fe and Zn doped metal precursors in the raw materials are Fe and Zn nitrates, the Zr precursor is selected from zirconium oxynitrate and zirconium carbonate, the molar ratio of Zr:Zn:Fe in the raw materials is (5-10):1:(0.01-1), the raw materials are added into a dispersant and stirred to dissolve, a gelling agent is added and stirred to a gel state; the wet gel is sealed into an autoclave, supercritically dried, and the dried solid is calcined at high temperature to obtain a metal-doped ZrO2 catalyst.

3. The method for preparing a catalyst suitable for hydrogenating carbon dioxide to methanol according to claim 2, characterized in that: The dispersant is a mixed solvent of ethanol and water, the volume concentration of ethanol is 20%-100%, the amount of the total metal substance of the doped metal and Zr to the dispersant is 1 mol:500-700 ml, and the gelling agent is a mixture of propylene oxide, formamide and acetic acid, and the molar ratio of the three is 1:(0.06-0.1):(0.08-0.12).

4. The method for preparing a catalyst suitable for producing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The specific operating conditions of the supercritical drying are: the pressure in the autoclave is maintained at about 6-8 MPa, the autoclave is heated to 90-280°C and maintained for 1-5 h; the temperature of the high-temperature calcination is 400-600°C, and the insulation time is 1-5 h.

5. The method for preparing a catalyst suitable for producing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: In the preparation method, at least one of the doping metal type, sol-gel method and supercritical drying is replaced: the doping metal is replaced with any one of Cr, Ce, Ga, In, Cd, Zn and Fe, and the molar ratio of Zr to the doping metal is 5-10:1; the sol-gel method is replaced with one of a coprecipitation method, a hydrothermal method and a calcination method, and when replaced with the calcination method, calcination is no longer performed after drying; the supercritical drying is replaced with one of ordinary drying, vacuum drying and freeze drying.

6. The method for preparing a catalyst suitable for producing methanol by hydrogenation of carbon dioxide according to claim 5, characterized in that: The hydrothermal method is to dissolve the doped metal precursor and the Zr precursor in water, then gradually add the (NH4)2CO3 solution to the solution, then transfer the mixture to a reactor, perform a hydrothermal reaction at 160-200°C for 10 h, and then dry; The calcination method comprises grinding the doped metal precursor and the Zr precursor solid, then calcining at 500-700°C for 4 hours, washing with distilled water and filtering and collecting to be dried; The coprecipitation method comprises dissolving the doped metal precursor and the Zr precursor in an ethanol aqueous solution and heating the solution to prepare solution A, dissolving (NH4)2CO3 in water to obtain solution B, dropping the A and B solutions into a beaker at the same time, performing the coprecipitation operation in a 70°C water bath, adjusting the pH value of the mixed solution to 9 to 10, aging at room temperature for 6 hours, and collecting the precipitate by centrifugation or filtration for drying.

7. A catalyst suitable for producing methanol by hydrogenating carbon dioxide, prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the catalyst suitable for producing methanol by hydrogenation of carbon dioxide as claimed in claim 7 in the reaction of producing methanol by hydrogenation of carbon dioxide.

9. The use according to claim 8, characterized in that: At 5.0 MPa, 24000 mL g cat -1 h -1 , 300 ° C, the methanol selectivity on the catalyst is more than 80%; at 5.0 MPa, 36000 ml g cat -1 h -1 Under the conditions of 360°C, the methanol space-time yield on the catalyst can exceed 180 g / kg cat ∙h -1 .

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