Zinc-zirconium catalyst for methanol production by thermal reduction of co2 and preparation method thereof

Abstract

The application discloses a zinc-zirconium catalyst for preparing methanol by thermal reduction of CO2 and a preparation method of the catalyst. The preparation method comprises the following steps: step (1), preparing a ZnZrOx catalyst by a coprecipitation method; step (2), dry etching the ZnZrOx catalyst; calcining the ZnZrOx catalyst prepared in step (1) at a high temperature; then, protecting oxygen vacancies obtained by etching with an oxygen vacancy protective agent; step (3), loading hydrogen overflow metal monomers by an impregnation method: mixing the ZnZrOx catalyst with an etching oxygen vacancy in step (2) with a water solution of a metal M precursor in a molar ratio of y% and stirring, then drying and calcining to obtain a zinc-zirconium catalyst loaded with hydrogen overflow metal monomers. The zinc-zirconium catalyst prepared by the preparation method is loaded with hydrogen overflow metal in the form of monomers, the crystal structure of the zinc-zirconium catalyst is not changed, the loading stability of the metal monomers is good, the conversion rate of methanol is high when the zinc-zirconium catalyst is used for catalyzing thermal reduction of CO2 to prepare methanol, and the selectivity of methanol is greater than 60%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalyst preparation, in particular to a zinc-zirconium catalyst for the thermal reduction of CO2 to methanol and a preparation method thereof. BACKGROUND

[0002] The statements in this section merely provide background information related to the present disclosure and can not constitute the prior art.

[0003] In recent years, recycling and converting carbon dioxide into hydrocarbon fuels has become a promising and economically valuable way of utilization, which is one of the important ways to address greenhouse effect and energy shortage.

[0004] Due to the stable chemical properties of CO2 molecules and the multi-electron reduction process involved in the reduction products, it is very difficult to catalytically reduce CO2 with high efficiency and high selectivity. The existing CO2 methanol catalysts cannot achieve high conversion rate and selectivity at the same time. Therefore, it is an urgent need to develop a high-efficiency thermal catalyst with high selectivity and high conversion rate to improve the catalytic efficiency of CO2 conversion to methanol, which is an urgent need to solve the problem of carbon utilization.

[0005] Transition metal single-atom catalysts not only have high atom utilization rate, excellent thermal chemical properties and high chemical stability, but also have hydrogen overflow effect which can improve the activation ability of hydrogen gas, thereby efficiently catalyzing the reduction of CO2. However, there are some problems in the preparation and catalysis of such catalysts, such as poor stability of metal single-atom loading in the preparation process, and many by-products such as CO and CH4 in the catalytic process. The existing co-precipitation method for preparing single-atom catalysts can cause changes in the crystal phase of the catalyst and the problem of hydrogen overflow metal segregation and agglomeration in the hydrogenation catalytic process. The loading stability of high-load concentration hydrogen overflow transition metal single-atom catalysts is not high. SUMMARY

[0006] The present application aims to overcome the deficiencies of the prior art and provides a zinc-zirconium catalyst for the thermal reduction of CO2 to methanol and a preparation method thereof. The hydrogen overflow metal single atoms on the catalyst have high loading stability, and the catalyst has high adsorption capacity for CO2 and intermediate products, thereby improving the selectivity of CO2 conversion to methanol and reducing the by-products in the product.

[0007] The technical solution of the present application is as follows:

[0008] A preparation method of a zinc-zirconium catalyst for the thermal reduction of CO2 to methanol, comprising the following steps:

[0009] Step (1) ZnZrO x .

[0010] Dissolve 20 g of Zr(N03)4*5H20 in 10 L of deionized water at 50-70 °C. After complete dissolution, cool the solution to room temperature, then add 7 g of Zn(N03)2*6H20 to the solution and stir until completely dissolved. Slowly add a mixture of 100 mL of saturated ammonia and anhydrous ethanol to the above solution. After stirring for 10 min, a gel is formed, which is aged in a water bath at 25-70 °C for 5-10 min, the precipitate is filtered to neutral with deionized water, and the precipitate is placed in an oven at 60-110 °C overnight. The dried solid is calcined at 500-700 °C at a temperature rise rate of 5-20 °C / min for 3-6 h, and the obtained zinc-zirconium solid solution is represented as ZnZrO x (ZZ).

[0011] (2) Etching ZnZrO x ;

[0012] Take 5 g of ZZ in step (1) and 1 g of NaBH4 and ball mill, then calcine the obtained mixture in a tube furnace at 350-450 °C at a temperature rise rate of 10-30 °C / min for 1 h until the color of the mixture changes, then rinse with a large amount of oxygen vacancy protectant until no bubbles are generated, and finally rinse with an oxygen vacancy protectant auxiliary agent and dry at 120 °C in an argon atmosphere for 12 h to obtain a zinc-zirconium solid solution with etched oxygen vacancies, represented as ZZ-l. After etching, the proportion of ZZ-l vacancy oxygen in the surface oxygen species is more than 30%, and the lattice structure is tetragonal. The etched dry method is calcined at high temperature, rather than the traditional wet method of reducing precipitation in solution. Rinsing the calcined catalyst precursor with an oxygen vacancy protectant and an oxygen vacancy protectant auxiliary agent can ensure the stability of the oxygen vacancy before loading the hydrogen overflow metal monatomic species. The phase transition ability of the oxygen vacancy protectant auxiliary agent is stronger than that of the oxygen vacancy protectant, and it is easier to separate from the catalyst precursor after rinsing than the oxygen vacancy protectant. The oxygen vacancy protectant auxiliary agent can remove residual oxygen vacancies and reduce drying time.

[0013] The zinc-zirconium solid solution with etched oxygen vacancies has better ability to load hydrogen overflow metal monatomic species, making the hydrogen overflow metal monatomic species more stable on the zinc-zirconium solid solution. The phase transition ability of the oxygen vacancy protectant auxiliary agent is stronger than that of the oxygen vacancy protectant, and it is easier to separate from the catalyst precursor after rinsing than the oxygen vacancy protectant.

[0014] Preferably, before etching, ZZ should be dried to remove internal moisture.

[0015] (3) Load hydrogen overflow metal monatomic by impregnation method.

[0016] Take 10 g of solid product ZZ-l in step (2) and 30 mL of y% aqueous solution of the corresponding M metal precursor (for example, 1% is 0.29 g of Cu (NO3) 2•2H2O) and stir for 4 h. Then, evaporate the water in a rotary evaporator at 50 mbar and 60°C. Dry the recovered powder at 120°C for 12 h or more, and finally calcine it at 500~700°C for 6 h under argon atmosphere to obtain a zinc zirconium solid solution oxide catalyst loaded with hydrogen over-flow metal monatomic atoms, which is referred to as y% M-ZnZrO x (for example, y=1, 1% Cu-ZnZrO x ).

[0017] Preferably, the M metal includes Pt, Pd, Ru, Cu, Co, Ni.

[0018] Preferably, the ZnZrO x obtained in step (1) is tetragonal phase.

[0019] Preferably, the M-ZnZrO x contains 0.5%~2% of M metal of hydrogen over-flow metal by mole ratio.

[0020] Preferably, the oxygen vacancy protecting agent used in step (2) is a polar solvent that can isolate oxygen and dissolve and remove the etchant NaBH4, and the oxygen vacancy protecting agent auxiliary is a solvent that can isolate oxygen and has a better volatilization effect than the oxygen vacancy protecting agent.

[0021] Preferably, it further comprises step (4): activation of the catalyst.

[0022] Preferably, the activation step is, for example:

[0023] (4.1) The thermal reduction conditions of the catalyst prepared by the aforementioned method for preparing a zinc zirconium catalyst for the thermal reduction of CO2 to methanol are: take 0.2 g (40~60 mesh) of the zinc zirconium solid solution oxide catalyst loaded with hydrogen over-flow metal monatomic atoms prepared, mix it with quartz sand of the same mesh in a mass ratio of 1:5 to dilute the catalyst and prevent local overheating;

[0024] (4.2) Fill the y% M-ZnZrO x into the fixed bed constant temperature section reaction tube, and use quartz wool as the interval at both ends. After temperature programming, use 5% hydrogen / nitrogen for 4 h of pretreatment, and after the reduction is completed, naturally cool down to obtain the activated y% M-ZnZrO x for the thermal reduction of CO2 to methanol.

[0025] Preferably, in step (4.2), the hydrogen reduction temperature of the y% M-ZnZrO x is less than 400°C.

[0026] Another aspect of the present application also provides a catalyst prepared by the preparation method of the aforementioned hydrogen overflow metal monatomic zinc zirconium metal oxide solid solution catalyst, and the crystal structure of the y% M-ZnZrOx is tetragonal phase.

[0027] Another aspect of the present application also provides a use method of the zinc zirconium catalyst for preparing methanol by thermal reduction of CO2, comprising the following steps:

[0028] (1) loading the activated catalyst y% M-ZnZrOx prepared by the preparation method as described above, and adjusting the reaction conditions to catalytically prepare methanol.

[0029] Preferably, the reaction conditions of "adjusting the reaction conditions" in step (1) are the optimal catalytic conditions of the catalyst. The optimal catalytic conditions of the catalyst are: the reaction pressure is 5.0-7.0 MPa, the reaction temperature is 310-350℃, the space velocity is 3000-12000 h-1, and the feed CO2:H2 is 1:3-1:10. -1

[0030] Compared with the prior art, the present application has the following beneficial effects:

[0031] 1. A zinc zirconium catalyst for preparing methanol by thermal reduction of CO2 and a preparation method thereof, wherein the hydrogen overflow metal loading significantly improves the hydrogen activation capacity of the catalyst, solves the problem of low activity of the zinc zirconium solid solution catalyst due to weak hydrogenation capacity, breaks through the hydrogen dissociation limiting step, and increases the carbon dioxide conversion rate of the catalyst by two times. Under the catalyst reaction conditions of the present application, the carbon dioxide methanol yield can reach 18.4% (carbon conversion rate 26%, methanol selectivity 71%), which is much higher than the methanol yield (about 11.2%) of the traditional zinc zirconium solid solution catalyst under the same conditions.

[0032] 2. A hydrogen overflow metal loaded zinc zirconium catalyst, wherein compared with the metal monatomic catalyst prepared by the coprecipitation method, the hydrogen overflow metal monatomic atom loaded by the etching impregnation method has a higher monatomic atom loading rate, and at the same time solves the problems of crystal phase change of the monatomic catalyst prepared by the coprecipitation method and hydrogen overflow metal segregation and agglomeration in the hydrogenation catalytic process, thereby having higher monatomic atom loading stability. In the 200h evaluation of the performance of the fixed bed catalyst, the loading of the monatomic atom is basically stable and unchanged.

[0033] 3. A hydrogen overflow metal loaded zinc zirconium catalyst, wherein compared with the catalytic hydrogenation product of the cluster loaded catalyst, the byproduct of the hydrogen overflow metal monatomic zinc zirconium oxide solid solution catalyst is almost only carbon monoxide, and no methane is generated, so that the catalyst has great industrial application potential. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 ​A preparation process of a hydrogen overflow metal supported zinc zirconium catalyst 1%Cu-ZnZrOx

[0035] Figure 2 XRD patterns of ZnZrO x etched with and without oxygen vacancy protectant

[0036] Figure 3 Micro-morphology characterization of 1%Cu-ZnZrO x prepared in Example 1

[0037] Figure 4 XRD patterns of zinc zirconium solid solution before and after loading of metal monatomic atoms in Example 2 and Example 3

[0038] Figure 5 XRD characterization patterns of catalysts with different Co loadings prepared in Example 3-6

[0039] Figure 6 (a) TEM image and cobalt element Mapping image of 1%Co-ZnZrOx prepared in Example 3 Figure 6 (b) TEM image and cobalt element Mapping image of 5%Co-ZnZrOx in Example 4 DETAILED DESCRIPTION

[0040] The features and performances of the present application are further described in detail below in combination with examples. The following examples facilitate better understanding of the present application. In the following examples, the test methods are conventional methods, unless otherwise specified. The test materials used in the following examples are commercially available. The zirconium nitrate, zinc nitrate, copper nitrate, cobalt nitrate, nickel nitrate, palladium nitrate, ruthenium nitrate, platinum nitrate, sodium borohydride, ethanol and quartz sand used in the present application are purchased from China National Pharmaceutical Group Chemical Reagent Co., Ltd.

[0041] Example 1 Preparation of a hydrogen overflow metal supported zinc zirconium catalyst and use thereof for thermal reduction of CO2 to methanol

[0042] As shown in Figure 1 , the specific steps are as follows:

[0043] Step (1) ZnZrO x was prepared by co-precipitation method.

[0044] Dissolve 20 g of Zr(N03)4*5H20 in 10 L of deionized water at 50-70 °C. After complete dissolution, cool the solution to room temperature, then add 7 g of Zn(N03)2*6H20 to the solution and stir until complete dissolution. Slowly add a mixture of 100 mL of saturated ammonia and anhydrous ethanol to the above solution. After stirring for 10 min, a gel is formed, which is aged in a water bath at 25-70 °C for 5-10 min, the precipitate is filtered to neutral with deionized water, and the precipitate is placed in an oven at 60-110 °C overnight. The dried solid is calcined at 500-700 °C at a temperature rise rate of 5-20 °C / min for 3-6 h, and the obtained zinc-zirconium solid solution is represented as ZnZrO x (ZZ).

[0045] (2) Etching ZnZrO x .

[0046] Take 5 g of ZZ in step (1) and 1 g of NaBH4 and mix them by ball milling. The obtained mixture is calcined in a tube furnace at 350-450 °C at a temperature rise rate of 10-30 °C / min for 1 h until the color of the mixture changes, after which it is rinsed with a large amount of an oxygen vacancy protecting agent (such as a solvent mainly composed of DMF or DMSO) until no gas bubbles are generated, and finally rinsed with an oxygen vacancy protecting agent auxiliary agent (such as a solvent mainly composed of chloroform or a lower alcohol) and dried at 120 °C under an argon atmosphere for 12 h to obtain a zinc-zirconium solid solution etched with oxygen vacancies, represented as ZZ-l.

[0047] Perform O1s orbital X-ray photoelectron spectroscopy comparison on ZnZrO x recorded as ZZ-0) and ZnZrOx (recorded as ZZ-l) etched with an oxygen vacancy protecting agent. The comparison chart is shown in Figure 2 The O1s signal can be deconvoluted into two different oxygen species: 532.2 eV represents vacancy oxygen, and 529.9 eV represents lattice oxygen. The ratio of vacancy oxygen is used as a qualitative indicator of the amount of surface oxygen vacancies. The higher the amount of oxygen vacancies, the more single atoms are ultimately loaded. As shown in Figure 2 , the oxygen vacancy ratio of ZZ-0 is 17%, and the oxygen vacancy ratio of ZZ-1 is 37%, indicating that the ZnZrO x etched with an oxygen vacancy protecting agent has a significantly higher oxygen vacancy ratio than the ZnZrO x .

[0048] (3) Load hydrogen overflow metal copper single atoms by impregnation method.

[0049] Take 10 g of solid product ZZ-l in step (2) and mix with 30 mL of 1% aqueous solution of copper metal precursor (containing 0.29 g of Cu(NO3)2•2H2O) and stir for 4 h. Then, evaporate water in a rotary evaporator at 50 mbar and 60°C. Dry the recovered powder at 120°C for 12 h above, and finally calcine under argon atmosphere at 500~700°C for 6 h to obtain a zinc zirconium solid solution oxide catalyst loaded with hydrogen over-flow metal monatomic atoms, which is referred to as 1%Cu-ZnZrOx. x .

[0050] (4) Take 0.2 g of the zinc zirconium solid solution oxide catalyst loaded with hydrogen over-flow metal monatomic atoms obtained in step (3) (40~60 mesh), mix with quartz sand of the same mesh in a mass ratio of 1:5 to dilute the catalyst to prevent local overheating.

[0051] (5) Fill the catalyst into a fixed bed constant temperature section reaction tube, and use quartz wool as spacer at both ends. After programmed temperature rising, use 5% hydrogen / nitrogen for pretreatment for 4 h, and the reduction temperature is less than 400°C. After reduction is completed, naturally cool down to the reaction temperature to obtain a reduced and activated CO2 methanol catalyst.

[0052] (6) Cut in the raw material gas (composition: CO is 1~5%, CO2 is 8~22%, Ar+CH4+N2≤12%, and the rest is H2), control the reaction pressure at 5.0~7.0 MPa, the reaction temperature at 310~350°C, and the space velocity at 3000~12000 h-1, and test the catalytic performance of the catalyst for CO2 thermal reduction to methanol. -1

[0053] Use the online testing method to detect the product composition of CO2 thermal reduction, and Ar gas is used as internal standard. After heat preservation, the gas phase product is directly introduced into a gas chromatograph, and the gas chromatograph is equipped with an automatic sampler, and the sampling interval is 30 min. The carbon conversion rate of the catalyst prepared by this method for methanol production from carbon dioxide can reach 25%, and the methanol selectivity can reach 68% (byproduct is carbon monoxide). In the 200 h evaluation of the performance of the fixed bed catalyst, the monatomic loading is basically stable and unchanged.

[0054] Figure 3 The micro-morphology characterization graph of the catalyst sample loaded with 1% Cu-ZnZrOx obtained in Example 1. From the graph, it can be seen that the Cu element is highly dispersed on the surface of the zinc zirconium solid solution in the form of monatomic atoms.

[0055] Example 2

[0056] Example 2 is a further illustration of Example 1, and the difference between Example 2 and Example 1 is that step (3) in Example 2 is:

[0057] ​Step (3) loading hydrogen over-flow metal nickel monatomic by impregnation method.

[0058] Take 10 g of solid product ZZ-l in step (2) and mix with 30 mL of 1% aqueous solution of nickel metal precursor (containing 0.31 g of Ni(NO3)2•6H2O) and stir for 4 h. Then, evaporate water in a rotary evaporator at 50 mbar and 60 °C. Dry the recovered powder at 120 °C for 12 h above, and finally calcine under argon atmosphere at 500-700 °C for 6 h to obtain a zinc-zirconium solid solution oxide catalyst loaded with hydrogen over-flow metal monatomic, which is called 1%Ni-ZnZrO x .

[0059] The remaining steps are the same as Example 1.

[0060] The carbon conversion rate of the catalyst prepared in this example for carbon dioxide to methanol can reach 15%, and the methanol selectivity can reach 82% (by-product is carbon monoxide). The loading of monatomic atoms is basically stable without change in the 200 h evaluation of the performance of the fixed bed catalyst.

[0061] Example 3

[0062] Example 3 is a further illustration of Example 1, and the difference between Example 3 and Example 1 is that step (3) in Example 3 is:

[0063] Step (3) loading hydrogen over-flow metal cobalt monatomic by impregnation method.

[0064] Take 10 g of solid product ZZ-l in step (2) and mix with 30 mL of 1% aqueous solution of cobalt metal precursor (containing 0.31 g of Co(NO3)2•6H2O) and stir for 4 h. Then, evaporate water in a rotary evaporator at 50 mbar and 60 °C. Dry the recovered powder at 120 °C for 12 h above, and finally calcine under argon atmosphere at 500-700 °C for 6 h to obtain a zinc-zirconium solid solution oxide catalyst loaded with hydrogen over-flow metal monatomic, which is called 1%Co-ZnZrO x .

[0065] The remaining steps are the same as Example 1.

[0066] The carbon conversion rate of the catalyst prepared in this method for carbon dioxide to methanol can reach 26%, and the methanol selectivity can reach 71% (by-product is carbon monoxide). The loading of monatomic atoms is basically stable without change in the 200 h evaluation of the performance of the fixed bed catalyst.

[0067] Figure 4XRD patterns of the samples obtained in Example 2 and Example 3. From the figure, it can be seen that the loaded metal does not destroy the original tetragonal lattice structure of the zinc-zirconium solid solution, and there is no cluster and nanoparticle structure bond, which proves that the metal single atom is loaded in the present patent.

[0068] Example 4

[0069] Example 4 is a further illustration of Example 3, and the difference between Example 4 and Example 3 is that step (3) in Example 4 is:

[0070] Step (3): loading hydrogen overflow metal cobalt single atom by impregnation method.

[0071] Take 10 g of the solid product ZZ-l in step (2) and mix it with 30 mL of a 5% aqueous solution of cobalt metal precursor (containing 1.55 g of Co(N03)2·6H20) and stir for 4 h. Then, evaporate the water in a rotary evaporator at 50 mbar and 60°C. Dry the recovered powder at 120°C for more than 12 h, and finally calcine it at 500-700°C for 6 h under an argon atmosphere to obtain a zinc-zirconium solid solution oxide catalyst loaded with hydrogen overflow metal single atom cobalt, which is called 5%Co-ZnZrO x .

[0072] The carbon conversion rate of the catalyst prepared in this example for carbon dioxide to methanol can reach 34%, and the methanol selectivity can reach 33% (by-product is carbon monoxide). In the fixed bed catalyst performance evaluation for 200 h, the loading of single atom is basically stable and unchanged.

[0073] Example 5

[0074] Example 5 is a further illustration of Example 3, and the difference between Example 5 and Example 3 is that step (3) in Example 5 is:

[0075] Step (3): loading hydrogen overflow metal cobalt single atom by impregnation method.

[0076] Take 10 g of the solid product ZZ-l in step (2) and mix it with 30 mL of a 5% aqueous solution of cobalt metal precursor (containing 1.55 g of Co(N03)2·6H20) and stir for 4 h. Then, evaporate the water in a rotary evaporator at 50 mbar and 60°C. Dry the recovered powder at 120°C for more than 12 h, and finally calcine it at 500-700°C for 6 h under an argon atmosphere to obtain a zinc-zirconium solid solution oxide catalyst loaded with hydrogen overflow metal single atom cobalt, which is called 5%Co-ZnZrO x .

[0077] The catalyst prepared in this embodiment achieves a carbon conversion rate of 27% and a methanol selectivity of 77% (with carbon monoxide as a byproduct). During the 200-hour evaluation of the fixed-bed catalyst performance, the single-atom loading remained essentially stable without change.

[0078] Example 6

[0079] Example 6 is a further explanation of Example 3. The difference between Example 6 and Example 3 is that step (3) in Example 6 is as follows:

[0080] Step (3): Load hydrogen overflow metal cobalt single atoms by impregnation method.

[0081] Take 10g of the solid product ZZ-l from step (2) and mix it with 30mL of a 2% aqueous solution of cobalt metal precursor (containing 0.62g Co(NO3)2·6H2O) and stir for 4h. Then, evaporate the water in a rotary evaporator at 50mbar and 60℃. Dry the recovered powder at 120℃ for more than 12h, and finally calcine it at 500~700℃ for 6h under an argon atmosphere to obtain a zinc zirconium solid solution oxide catalyst supported on hydrogen overflow metal single atoms, which is called 2%Co-ZnZrO x .

[0082] The catalyst prepared by this method achieves a carbon conversion rate of up to 31% and a methanol selectivity of up to 66% (with carbon monoxide as a byproduct). During a 200-hour evaluation of the fixed-bed catalyst performance, the single-atom loading remained essentially stable without change.

[0083] Comparing the conversion rate and selectivity data of the catalysts prepared in Examples 4 and 3, 5 and 6 in actual use, it can be seen that the methanol selectivity of the 5% Co-ZnZrOx prepared in Example 4 is significantly reduced.

[0084] The XRD characterization spectra of the catalysts with different Co loadings prepared in Examples 3-6 are as follows: Figure 5 As shown, from Figure 5 It can be seen that all CoZnZrO x It exhibits tetragonal zirconium oxide (i.e., t-ZrO2). When a small amount of Co is introduced, i.e., the loading is <1%wt, the XRD shows an increase in the full width at half maximum (FWHM), indicating a decrease in crystal size; when the loading is >2%wt, the XRD shows a decrease in the FWHM, indicating an increase in crystal size.

[0085] The 1% Co-ZnZrO prepared in Example 3 x Characterization yielded TEM images and cobalt elemental mapping images, such as... Figure 6 As shown in (a); the TEM image and cobalt elemental mapping diagram of the 5% Co-ZnZrOx in Example 4 were obtained by characterization, as shown in (a).Figure 6 As shown in (b). By Figure 6 (b) The TEM image (left) shows that the sample is in an amorphous state (the stripes are not neat). The ordered structure of the tetragonal zirconium oxide catalyst has been destroyed. Amorphous cobalt oxide nanoparticles with a lattice spacing of 0.25 nm were found, indicating that Co has agglomerated rather than being dispersed in the sample in a single atomic state. Figure 6 The element mapping in (b) (right) shows that Co is unevenly dispersed, indicating that some Co aggregates in particulate form within the catalyst. Figure 6 (a) The TEM image (left) shows that the sample exhibits obvious lattice fringes, indicating that the tetragonal zirconium oxide of the sample retains the ordered structure of the catalyst, and the dark spots are single Co atoms; ​ (a) The elemental mapping diagram (right) illustrates that Co is highly dispersed in the catalyst in a single-atom state.

[0086] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

Claims

1. A method for preparing a zinc-zirconium catalyst for the thermal reduction of CO2 to methanol, characterized in that, The method comprises the following steps: Step (1) Preparation of ZnZrO by co-precipitation method x ; Step (2) Dry etching of ZnZrO x ; The ZnZrO prepared in step (1) was calcined at high temperature x ; and the etched oxygen vacancies were then protected using an oxygen vacancy protector Step (3) impregnation method is used to load hydrogen overflow metal monatomic: ZnZrO of step (2) is etched x The ZnZrO of step (2) is etched with a solution of water mixed with the molar percentage y% of M metal precursor and stirred, then dried and calcined, obtaining a zinc-zirconium solid solution oxide catalyst loaded with hydrogen overflown metal monosatoms: y% M-ZnZrO x ; In step (3), the hydrogen overflow metal M metal comprises Pt, Pd, Ru, Cu, Co and Ni; In step (3), the molar percentage y% of the M metal precursor is 0.5% to 2%; Step (2) dry etching ZnZrO x Specifically: taking the ZnZrO prepared in step (1) x , ball-milling with NaBH4, then calcining at 350-450°C with a temperature rising rate of 10-30°C / min until the color of the mixture changes, then flushing the mixture with an oxygen vacancy protection agent until no bubbles are generated, finally flushing with an oxygen vacancy protection agent auxiliary agent and drying to obtain ZnZrO with etched oxygen vacancies x ; In step (2), the oxygen vacancy protective agent is a polar solvent which can isolate oxygen and dissolve and remove the etchant NaBH4; the oxygen vacancy protective agent auxiliary agent is a solvent which can isolate oxygen and has a better volatilization effect than the oxygen vacancy protective agent.

2. A zinc-zirconium catalyst for the reduction of CO2 to methanol by heat, characterized in that, The zinc-zirconium catalyst for preparing methanol by reducing CO2 is prepared by using the preparation method of the zinc-zirconium catalyst for preparing methanol by reducing CO2 according to claim 1.

3. The zinc-zirconium catalyst for the reduction of CO2 to methanol by heat according to claim 2, characterized in that, The y% M-ZnZrO x The crystal structure is tetragonal.

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