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

Abstract

The invention provides a catalyst for preparing methanol through carbon dioxide hydrogenation as well as a preparation method and application of the catalyst, and relates to the technical field of catalysts. The catalyst comprises a metal oxide solid solution and a palladium element doped in the metal oxide solid solution; wherein the metal oxide solid solution comprises a zinc oxide-tungsten oxide compound. The catalyst provided by the invention is prepared by hydrothermal crystallization, has the characteristics of high activity, high methanol selectivity and long-time stable operation at relatively high temperature and pressure, and provides a wide prospect for subsequent industrial application and a subsequent conversion process of coupled methanol.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogenation of carbon dioxide to methanol, and particularly to a catalyst for hydrogenation of carbon dioxide to methanol, a preparation method thereof, and an application thereof. Background Art

[0002] CO2 is the main component of greenhouse gases in the atmosphere. Its generation comes from the combustion of a large amount of fossil fuels and has led to the increasingly deepening global climate change in the past few decades. Human activities emit nearly 40 billion tons of CO2 into the atmosphere every year. The CO2 content in the atmosphere reached 407 ppm in 2019, increasing by 20% in the past 40 years. Undoubtedly, reducing CO2 emissions has become an urgent issue. If CO2 can be converted into chemical raw materials through renewable energy, it can not only solve the problem of excessive CO2 emissions, but also make CO2 a new carbon source to replace traditional fossil fuels.

[0003] Methanol is an important chemical intermediate raw material and can be used as a fuel for internal combustion engines and fuel cells. With the gradual reduction of non-renewable energy, methanol, as an alternative chemical raw material, can synthesize various chemicals and fuels such as gasoline. The technology of hydrogenation of carbon dioxide to methanol can not only realize the resource conversion of carbon dioxide, help solve the problem of storage of renewable energy, but also realize carbon dioxide emission reduction and slow down ecological deterioration. Therefore, the hydrogenation of CO2 to methanol is regarded as an effective way for large-scale resource utilization of CO2. However, due to the chemical inertness of CO2, its efficient conversion to methanol is still extremely challenging. When traditional Cu-ZnO catalysts are applied to the hydrogenation of CO2 to methanol, the prominent problems are the difficulty in activating CO2 and the low selectivity of methanol.

[0004] Currently, the hydrogenation of CO2 to methanol mainly uses supported metal or metal oxide catalysts. For example, the Catalysis Research Institute of Zhejiang University prepared a Cu / Mn / Al system catalyst by the co-current coprecipitation method. The total conversion rate of CO2 was 15.8%, the selectivity of methanol was 20.8%, and the single-pass yield of methanol was 4.3%. For example, Xu Yong et al. from East China University of Science and Technology studied the hydrogenation of CO2 to methanol on a Cu-ZnO-Al2O3 catalyst, and the selectivity of methanol was 12.57%; the conversion rate of CO2 on a Cu-ZnO binary catalyst with CO2 and H2 was 18.71%, and the selectivity of methanol was 9.87%. And such catalysts have been widely studied in the CO2 hydrogenation reaction in inventions such as CN103272607A, CN101983765A, CN102000578A, CN102302934A, etc.

[0005] However, due to their high activity in the reverse water gas shift (RWGS), they have a low methanol selectivity and lack stability due to the water-induced sintering of the active phase. In recent years, transition metal-modified Cu-Zn materials have also been widely studied. For example, CuZnGa-hydrotalcite achieved a methanol yield of 0.59 kg CH3OH / Lcat·h at a CO2 conversion rate of 20%, but the methanol selectivity was only about 50% (ACS Catal. 2018, 8, 4390-4401). The methanol selectivity of the Pd / CeO2 catalyst loaded with noble metals reached 92%, but the CO2 conversion rate was not ideal (J. Catal., 1994, 150, 217-220).

[0006] Therefore, designing a catalyst that can operate stably under reaction conditions and has a high CO2 conversion rate and methanol selectivity is an urgent problem for the industrial application of CO2 hydrogenation to methanol.

[0007] In view of this, the present invention is specifically proposed. Summary of the Invention

[0008] The object of the present invention is to provide a catalyst for hydrogenating carbon dioxide to methanol, its preparation method and application. The catalyst of the present invention is prepared by hydrothermal crystallization. The catalyst in this application has the characteristics of high activity, high methanol selectivity, and long-term stable operation at high temperature and pressure, providing a broad prospect for subsequent industrial applications and coupling with the subsequent conversion process of methanol.

[0009] In order to achieve the above object of the present invention, the following technical solutions are specifically adopted:

[0010] In the first aspect, the present invention provides a catalyst for hydrogenating carbon dioxide to methanol, which comprises a metal oxide solid solution and palladium element doped in the metal oxide solid solution;

[0011] Among them, the metal oxide solid solution comprises a composite of zinc oxide-tungsten oxide.

[0012] Preferably, the chemical formula of the composite of zinc oxide-tungsten oxide is Zn x W y O;

[0013] Among them, x:y = 1:(1-10).

[0014] Preferably, the doping amount of palladium element in the catalyst is 0.1-1.0 wt%.

[0015] Preferably, the crystal morphology structure of the catalyst comprises a nanosphere structure.

[0016] Preferably, the catalyst is formed by piling up several nanospheres, the nanospheres are metal oxide solid solutions, and the metal oxide solid solutions include zinc oxide-tungsten oxide composites.

[0017] Preferably, the particle size of a single nanosphere is 10-300 nm.

[0018] Preferably, the catalyst further includes rod-shaped structures, the rod-shaped structures are metal oxides that do not form solid solutions, and the metal oxides that do not form solid solutions are zinc oxide.

[0019] Preferably, the length of the rod-shaped structure is 20-40 μm, the width of the rod-shaped structure is 0.5-2.0 μm, and the thickness of the rod-shaped structure is 500-800 nm.

[0020] In a second aspect, the present invention provides a preparation method of a catalyst for hydrogenating carbon dioxide to methanol as described in the first aspect, and the preparation method includes the following steps:

[0021] Dissolve a tungsten salt, a zinc salt and a palladium salt in water to obtain solution A;

[0022] Dissolve a surfactant in an acid solution to obtain solution B;

[0023] Add solution A to solution B, perform the first mixing and stirring to obtain solution C;

[0024] Add a precipitant to solution C, perform the second mixing and stirring, and then perform a crystallization reaction to obtain a crystallized solid;

[0025] Filter, wash and dry the crystallized solid, and then perform calcination, tabletting and pulverization to obtain the catalyst for hydrogenating carbon dioxide to methanol.

[0026] Preferably, the molar ratio of zinc element in the zinc salt to tungsten element in the tungsten salt is (0.15-1):1.

[0027] Preferably, the zinc salt is selected from water-soluble zinc salts, preferably any one or at least two combinations of zinc nitrate, zinc carbonate or zinc sulfate, and more preferably zinc nitrate.

[0028] Preferably, the tungsten salt is selected from water-soluble tungsten salts, preferably sodium tungstate and / or sodium metatungstate, and more preferably sodium tungstate.

[0029] Preferably, the palladium salt is selected from water-soluble palladium salts, preferably palladium nitrate and / or palladium acetate, and more preferably palladium nitrate.

[0030] Preferably, the surfactant is selected from PVP and / or P123.

[0031] Preferably, the mass ratio of the tungsten salt to the surfactant is 100:(5-15).

[0032] Preferably, the acid solution is selected from glacial acetic acid solution.

[0033] Preferably, the concentration of the acid solution is 0.5-3.0 mol / L, preferably 1.0-1.5 mol / L.

[0034] Preferably, the temperature for dissolving the surfactant in the acid solution is 40-80 °C.

[0035] Preferably, the temperature of the first mixing and stirring is 40-80 °C, and the time of the first mixing and stirring is 0.5-2.5 h.

[0036] Preferably, the precipitating agent is selected from urea and / or ammonia water, preferably urea and ammonia water.

[0037] Preferably, the molar ratio of urea to zinc element in the zinc salt is (5-10):1.

[0038] Preferably, the molar ratio of ammonia water to zinc element in the zinc salt is (2-8):1.

[0039] Preferably, the temperature of the second mixing and stirring is 40-80 °C, and the time of the second mixing and stirring is 0.5-2.5 h.

[0040] Preferably, the temperature of the crystallization reaction is 150-200 °C, and the time of the crystallization reaction is 15-48 h.

[0041] Preferably, the temperature of the drying is 80-120 °C.

[0042] Preferably, the temperature of the calcination is 300-600 °C, and the time of the calcination is 5-24 h.

[0043] Preferably, the particle size of the catalyst for hydrogenating carbon dioxide to methanol is 40-60 mesh.

[0044] In a third aspect, the present invention provides an application of the catalyst for hydrogenating carbon dioxide to methanol as described in the first aspect as a catalyst for hydrogenating carbon dioxide to methanol.

[0045] In a fourth aspect, the present invention provides a method for hydrogenating carbon dioxide to methanol, the method comprising the following steps:

[0046] In the presence of a catalyst, a raw material gas containing carbon dioxide and hydrogen undergoes a hydrogenation reaction to obtain methanol; wherein, the catalyst includes the catalyst for hydrogenating carbon dioxide to methanol as described in the first aspect.

[0047] Preferably, the hydrogenation reaction is carried out in a fixed-bed reactor.

[0048] Preferably, the space velocity of the feed gas is 2000 - 26000 h -1 .

[0049] Preferably, the molar ratio of hydrogen to carbon dioxide in the feed gas is (2 - 4):1.

[0050] Preferably, the temperature of the hydrogenation reaction is 300 - 400 °C, and the pressure of the hydrogenation reaction is 2.0 - 10.0 MPa.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] (1) The catalyst of the present invention has the characteristics of high activity, high methanol selectivity, and stable operation at high temperature and pressure for a long time, providing a broad prospect for subsequent industrial applications and coupling with the subsequent methanol conversion process (MTO, MTG);

[0053] (2) The preparation method of the catalyst of the present invention adopts the hydrothermal crystallization method to prepare an oxide solid solution with a nano-spherical structure. The catalyst preparation process is simple, easy to repeat, and can be prepared on a large scale;

[0054] (3) Through hydrothermal crystallization, the catalyst of the present invention promotes a small amount of Zn metal and Pd metal to enter the WO3 lattice to form element doping, thereby promoting the rapid separation of WO3 electron-hole pairs, increasing the concentration of free electrons, enhancing the adsorption and activation ability of CO2 molecules, and improving the CO2 conversion rate;

[0055] (4) A small amount of precious metal Pd is introduced into the oxide solid solution of the catalyst of the present invention. Utilizing the strong H2 adsorption performance of the precious metal, the reaction activity of the catalyst is improved. Description of the Drawings

[0056] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0057] Figure 1 SEM image of the catalyst prepared in Example 1. Detailed Embodiments

[0058] Unless otherwise defined herein, scientific and technical terms used in connection with the present invention shall have the meanings commonly understood by those of ordinary skill in the art. The meanings and scopes of the terms should be clear. However, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or extrinsic definition. In this application, unless otherwise specified, the use of "or" means "and / or". In addition, the use of the term "comprising" and other forms is non-restrictive.

[0059] It should be noted that specific details are set forth in the following description to facilitate a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0060] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0061] In a first aspect, the present invention provides a catalyst for hydrogenating carbon dioxide to methanol, the catalyst comprising a metal oxide solid solution and palladium element doped in the metal oxide solid solution;

[0062] Wherein, the metal oxide solid solution comprises a composite of zinc oxide-tungsten oxide.

[0063] In the present invention, a composite of zinc oxide-tungsten oxide, a metal oxide solid solution, is formed by Zn metal entering the WO3 lattice. Further, Pd is doped in the metal oxide solid solution to form element doping, thereby promoting the rapid separation of electron-hole pairs in WO3, increasing the concentration of free electrons, enhancing the adsorption and activation ability of CO2 molecules, and improving the CO2 conversion rate; and a small amount of noble metal Pd is introduced into the doped oxide solid solution of the catalyst, and the characteristics of strong H2 adsorption performance of the noble metal are utilized to further improve the reaction activity of the catalyst. This catalyst is used in the reaction of hydrogenating carbon dioxide to methanol, and has the characteristics of high activity, high methanol selectivity, and stable operation at high temperature and pressure for a long time.

[0064] As an optional embodiment, the chemical formula of the composite of zinc oxide-tungsten oxide is Zn x W y O; wherein, x:y = 1:(1-10), for example, it can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, etc.

[0065] As an alternative embodiment, x is 0.15 to 0.5, and for example, it can be 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, etc.

[0066] As an alternative embodiment, y is 0.5 to 0.75, and for example, it can be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, etc.

[0067] As an alternative embodiment, the doping amount of palladium element in the catalyst for hydrogenating carbon dioxide to methanol is 0.1 to 1.0 wt%, and for example, it can be 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, etc.

[0068] As an alternative embodiment, the crystal morphology structure of the catalyst for hydrogenating carbon dioxide to methanol includes a nano-sphere structure.

[0069] As an alternative embodiment, the catalyst for hydrogenating carbon dioxide to methanol is formed by stacking several nano-spheres, the nano-spheres are metal oxide solid solutions, and the metal oxide solid solutions include a composite of zinc oxide - tungsten oxide.

[0070] As an alternative embodiment, the particle size of a single nano-sphere is 10 to 300 nm, and for example, it can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 120 nm, 125 nm, 140 nm, 150 nm, 175 nm, 200 nm, 225 nm, 250 nm, 275 nm, 300 nm, etc.

[0071] As an alternative embodiment, the catalyst further includes a rod-like structure, the rod-like structure is a metal oxide that has not formed a solid solution, and the metal oxide that has not formed a solid solution is zinc oxide.

[0072] As an alternative embodiment, the length of the rod-like structure is 20 to 40 μm, and for example, it can be 20 μm, 22 μm, 24 μm, 25 μm, 26 μm, 28 μm, 30 μm, 32 μm, 34 μm, 35 μm, 36 μm, 38 μm, 40 μm, etc.

[0073] As an alternative embodiment, the width of the rod-like structure is 0.5 to 2.0 μm, and for example, it can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2.0 μm, etc.

[0074] As an alternative embodiment, the thickness of the rod-shaped structure is 500 to 800 nm, for example, it can be 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, etc.

[0075] In a second aspect, the present invention provides a method for preparing a catalyst for hydrogenating carbon dioxide to methanol as described in the first aspect, and the preparation method includes the following steps:

[0076] Dissolve a tungsten salt, a zinc salt, and a palladium salt in water to obtain solution A;

[0077] Dissolve a surfactant in an acid solution to obtain solution B;

[0078] Add solution A to solution B, and perform the first mixing and stirring to obtain solution C;

[0079] Add a precipitating agent to solution C, perform the second mixing and stirring, and then carry out a crystallization reaction to obtain a crystallized solid;

[0080] Filter, wash, and dry the crystallized solid, and then carry out calcination, tabletting, and pulverization to obtain the catalyst for hydrogenating carbon dioxide to methanol.

[0081] In the present invention, the preparation method of the catalyst adopts a hydrothermal crystallization method in an autoclave, which promotes a small amount of Zn metal and Pd metal to enter the WO3 lattice to form element doping, and prepares an oxide solid solution with a nanosphere crystal morphology structure. The catalyst preparation process is simple, easy to repeat, and can be prepared on a large scale.

[0082] As an alternative embodiment, the molar ratio of zinc element in the zinc salt to tungsten element in the tungsten salt is (0.15 to 1):1, for example, it can be 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1, 0.5:1, 0.55:1, 0.6:1, 0.65:1, 0.7:1, 0.8:1, 0.9:1, 1:1, etc.

[0083] As an alternative embodiment, the zinc salt is selected from water-soluble zinc salts.

[0084] As an alternative embodiment, the zinc salt is selected from any one or a combination of at least two of zinc nitrate, zinc carbonate, or zinc sulfate.

[0085] As a preferred embodiment, the zinc salt is preferably zinc nitrate.

[0086] As an alternative embodiment, the tungsten salt is selected from water-soluble tungsten salts.

[0087] As an alternative embodiment, the tungsten salt is selected from sodium tungstate and / or sodium metatungstate.

[0088] As a preferred embodiment, the tungsten salt is selected from sodium tungstate.

[0089] As an alternative embodiment, the palladium salt is selected from water-soluble palladium salts, preferably palladium nitrate and / or palladium acetate.

[0090] As a preferred embodiment, the palladium salt is selected from palladium nitrate.

[0091] As an alternative embodiment, the surfactant is selected from PVP (polyvinylpyrrolidone) and / or P123 (polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer).

[0092] As an alternative embodiment, the mass ratio of the tungsten salt to the surfactant is 100:(5 - 15), for example, it can be 100:5, 100:6, 100:7, 100:8, 100:9, 100:10, 100:11, 100:12, 100:13, 100:14, 100:15, etc.

[0093] As an alternative embodiment, the acid solution is selected from acetic acid solution.

[0094] As an alternative embodiment, the concentration of the acid solution is 0.5 - 3.0 mol / L, for example, it can be 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.2 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.8 mol / L, 2.0 mol / L, 2.2 mol / L, 2.4 mol / L, 2.5 mol / L, 2.6 mol / L, 2.8 mol / L, 3.0 mol / L, etc.

[0095] As a preferred embodiment, the concentration of the acid solution is selected to be 1.0 - 1.5 mol / L.

[0096] As an alternative embodiment, the temperature at which the surfactant is dissolved in the acid solution is 40 - 80 °C, for example, it can be 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, etc.

[0097] As a preferred embodiment, the temperature at which the surfactant is dissolved in the acid solution is 60 °C.

[0098] As an alternative embodiment, the temperature of the first mixing and stirring is 40 to 80 °C, for example, it can be 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, etc., and the time of the first mixing and stirring is 0.5 to 2.5 h, for example, it can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1 h, 1.0 h, 1.2 h, 1.4 h, 1.5 h, 1.6 h, 1.8 h, 2.0 h, 2.2 h, 2.4 h, 2.5 h, etc.

[0099] As a preferred embodiment, the temperature of the first mixing and stirring is 60 °C, and the time of the first mixing and stirring is 1 h.

[0100] As an alternative embodiment, the precipitant is selected from urea and / or ammonia water.

[0101] As a preferred embodiment, the precipitant is a combination of urea and ammonia water.

[0102] As an alternative embodiment, the molar ratio of urea to zinc element in the zinc salt is (5 to 10):1, for example, it can be 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc.

[0103] As an alternative embodiment, the molar ratio of ammonia water to zinc element in the zinc salt is (2 to 8):1, for example, it can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, etc.

[0104] As an alternative embodiment, the temperature of the second mixing and stirring is 40 to 80 °C, for example, it can be 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, etc., and the time of the second mixing and stirring is 0.5 to 2.5 h, for example, it can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1 h, 1.0 h, 1.2 h, 1.4 h, 1.5 h, 1.6 h, 1.8 h, 2.0 h, 2.2 h, 2.4 h, 2.5 h, etc.

[0105] As a preferred embodiment, the temperature of the second mixing and stirring is 60 °C.

[0106] As an alternative embodiment, the temperature of the crystallization reaction is 150 to 200 °C, such as 150 °C, 155 °C, 160 °C, 165 °C, 170 °C, 175 °C, 180 °C, 185 °C, 190 °C, 195 °C, 200 °C, etc., and the time of the crystallization reaction is 15 to 48 h, such as 15 h, 16 h, 18 h, 20 h, 22 h, 24 h, 26 h, 28 h, 30 h, 32 h, 34 h, 36 h, 38 h, 40 h, 42 h, 44 h, 46 h, 48 h, etc.

[0107] As an alternative embodiment, the temperature of the drying is 80 to 120 °C, such as 80 °C, 85 °C, 90 °C, 95 °C, 100 °C, 105 °C, 110 °C, 115 °C, 120 °C, etc.

[0108] As an alternative embodiment, the temperature of the calcination is 300 to 600 °C, such as 300 °C, 320 °C, 350 °C, 380 °C, 400 °C, 420 °C, 450 °C, 480 °C, 500 °C, 520 °C, 550 °C, 580 °C, 600 °C, etc., and the time of the calcination is 5 to 24 h, such as 5 h, 6 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, etc.

[0109] As an alternative embodiment, the particle size of the catalyst for hydrogenating carbon dioxide to methanol is 40 to 60 mesh, such as 40 mesh, 42 mesh, 44 mesh, 45 mesh, 46 mesh, 48 mesh, 50 mesh, 52 mesh, 54 mesh, 56 mesh, 58 mesh, 60 mesh, etc.

[0110] In a third aspect, the present invention provides an application of the catalyst for hydrogenating carbon dioxide to methanol as described in the first aspect as a catalyst for hydrogenating carbon dioxide to methanol.

[0111] In a fourth aspect, the present invention provides a method for hydrogenating carbon dioxide to methanol, the method comprising the following steps:

[0112] In the presence of a catalyst, a raw material gas containing carbon dioxide and hydrogen undergoes a hydrogenation reaction to obtain methanol; wherein, the catalyst comprises the catalyst for hydrogenating carbon dioxide to methanol as described in the first aspect.

[0113] As an alternative embodiment, the hydrogenation reaction is carried out in a fixed-bed reactor.

[0114] As an alternative embodiment, the space velocity of the raw material gas is 22000 to 26000 h -1 , such as 22000 h -1 , 22500 h -1 , 23000 h-1 、23500 h -1 、24000 h -1 、24500 h -1 、25000 h -1 、25500 h -1 、26000 h -1 etc.

[0115] As an optional embodiment, the molar ratio of carbon dioxide to hydrogen in the raw material gas is (2 - 4):1. For example, it can be 2:1, 2.2:1, 2.4:1, 2.5:1, 2.6:1, 2.8:1, 3:1, 3.2:1, 3.4:1, 3.5:1, 3.6:1, 3.8:1, 4:1, etc.

[0116] As an optional embodiment, the temperature of the hydrogenation reaction is 300 - 400 °C. For example, it can be 300 °C, 310 °C, 320 °C, 330 °C, 340 °C, 350 °C, 360 °C, 370 °C, 380 °C, 390 °C, 400 °C, etc. The pressure of the hydrogenation reaction is 2.0 - 10.0 MPa. For example, it can be 2.0 MPa, 2.5 MPa, 3.0 MPa, 3.5 MPa, 4.0 MPa, 4.5 MPa, 5.0 MPa, 5.5 MPa, 6.0 MPa, 6.5 MPa, 7.0 MPa, 7.5 MPa, 8.0 MPa, 8.5 MPa, 9.0 MPa, 9.5 MPa, 10.0 MPa, etc.

[0117] The present invention will be further described below through examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or directly purchased from the market.

[0118] Example 1

[0119] This example provides Cat-1 catalyst (0.1 wt% Pd-Zn 0.15 W 0.75 O). The Cat-1 catalyst is prepared by the following steps:

[0120] Weigh 28.7 g of sodium tungstate, 3.9 g of zinc nitrate and 0.004 g of palladium nitrate and dissolve them in deionized water to prepare solution A; weigh 2.3 g of PVP and dissolve it in 1.0 mol / L glacial acetic acid, heat to 60 °C and stir until completely dissolved to prepare solution B; add the prepared solution A dropwise to solution B, keep the solution temperature at 60 °C, stir for 1 h to prepare solution C. Weigh 6.2 g of urea and dissolve it in the above solution, keep the solution temperature at 60 °C, stir for 2.5 h, then transfer the mixture to an autoclave for crystallization, the crystallization temperature is 180 °C and the crystallization time is 20 h. After cooling and venting, filter to obtain the solid, wash it 5 times, then dry it in an oven at 80 °C, and then calcine it in air at 500 °C for 18 h, press and crush it to 40 - 60 mesh to obtain 0.1 wt% Pd-Zn 0.15 W 0.75 O catalyst, denoted as Cat-1 catalyst.

[0121] As Figure 1 shown, it can be seen that the catalyst prepared in Example 1 is a nanosphere structure crystal form. The spherical morphology is formed by the accumulation of countless nanospheres. The particle size of a single nanosphere is 20 - 100 nm. Part of the rod-like structure is the crystal morphology of ZnO that has not formed a solid solution, with a length of up to 30 μm, a width of 1 μm, and a thickness of 500 - 800 nm.

[0122] Example 2

[0123] This example provides the preparation of Cat-2 catalyst (0.2% Pd-Zn 0.15 W 0.75 O), and the Cat-1 catalyst is prepared by the following steps:

[0124] Weigh 28.7 g of sodium tungstate, 3.9 g of zinc nitrate and 0.009 g of palladium nitrate and dissolve them in deionized water to prepare solution A; weigh 1.4 g of P123 and dissolve it in 1.5 mol / L glacial acetic acid, heat to 60 °C and stir until completely dissolved to prepare solution B; add the prepared solution A dropwise to solution B, keep the solution temperature at 60 °C, stir for 1 h to prepare solution C. Weigh 1.4 g of urea and dissolve it in the above solution, weigh 3.6 g of ammonia water and slowly add it to the solution, keep the solution temperature at 60 °C, stir for 2.0 h, then transfer the mixture to an autoclave for crystallization, the crystallization temperature is 150 °C and the crystallization time is 48 h. After cooling and venting, filter to obtain the solid, wash it 5 times, then dry it in an oven at 80 °C, and then calcine it in air at 400 °C for 24 h, press and crush it to 40 - 60 mesh to obtain 0.2 wt% Pd-Zn 0.15 W 0.75 O catalyst, denoted as Cat-2 catalyst.

[0125] The catalyst prepared in Example 2 is a nanosphere-structured crystal form. The spherical morphology is formed by the accumulation of countless nanospheres. The particle size of a single nanosphere is 50 - 120 nm. Some rod-like structures are the crystal morphology of ZnO that has not formed a solid solution, with a length of up to 20 μm, a width of 0.5 μm, and a thickness of 300 - 500 nm.

[0126] Example 3

[0127] This example provides Cat-3 catalyst (0.5 wt% Pd-Zn 0.15 W 0.75 O). The Cat-1 catalyst is prepared by the following steps:

[0128] Weigh 28.7 g of sodium tungstate, 3.9 g of zinc nitrate, and 0.021 g of palladium nitrate and dissolve them in deionized water to prepare solution A; weigh 4.3 g of P123 and dissolve it in 1.5 mol / L glacial acetic acid, heat to 60 °C and stir until completely dissolved to prepare solution B; add the prepared solution A dropwise to solution B, keep the solution temperature at 60 °C, stir for 1 h to prepare solution C. Weigh 7.8 g of urea and dissolve it in the above solution, slowly add 3.6 g of ammonia water to the solution, keep the solution temperature at 60 °C, stir for 1.5 h, then transfer the mixed solution to an autoclave for crystallization, with a crystallization temperature of 200 °C and a crystallization time of 15 h. After cooling and venting, filter to obtain the solid, wash it 5 times, then dry it in an oven at 120 °C, and then calcine it in air at 300 °C for 24 h, press and crush it to 40 - 60 mesh to obtain 0.5 wt% Pd-Zn 0.15 W 0.75 O catalyst, denoted as Cat-3 catalyst.

[0129] The catalyst prepared in Example 3 is a nanosphere-structured crystal form. The spherical morphology is formed by the accumulation of countless nanospheres. The particle size of a single nanosphere is 50 - 120 nm. Some rod-like structures are the crystal morphology of ZnO that has not formed a solid solution, with a length of up to 25 μm, a width of 1 μm, and a thickness of 300 - 500 nm.

[0130] Example 4

[0131] This example provides Cat-4 catalyst (1 wt% Pd-Zn 0.15 W 0.75 O). The Cat-4 catalyst is prepared by the following steps:

[0132] Weigh 28.7 g of sodium tungstate, 3.9 g of zinc nitrate and 0.042 g of palladium nitrate and dissolve them in deionized water to prepare solution A; weigh 4.3 g of PVP and dissolve it in 1.5 mol / L glacial acetic acid, heat it to 60 °C and stir until completely dissolved to prepare solution B; add the prepared solution A dropwise to solution B, keep the solution temperature at 60 °C, stir for 1 h to prepare solution C. Weigh 14.6 g of ammonia water and slowly add it to the solution, keep the solution temperature at 60 °C, stir for 0.5 h and then transfer the mixture to an autoclave for crystallization, with a crystallization temperature of 180 °C and a crystallization time of 15 h. After cooling and venting, filter to obtain the solid, wash it 5 times, then dry it in an oven at 100 °C, and then calcine it in air at 500 °C for 18 h, press and crush it to 40 - 60 mesh to obtain a 1 wt% Pd-Zn 0.15 W 0.75 O catalyst, denoted as Cat-4 catalyst.

[0133] The catalyst prepared in Example 4 has a nanosphere structure crystal form. The spherical morphology is formed by the accumulation of countless nanospheres. The particle size of a single nanosphere is 20 - 120 nm. Part of the rod-like structure is the crystal morphology of ZnO that has not formed a solid solution, with a length of up to 35 μm, a width of 1 μm, and a thickness of 500 - 800 nm.

[0134] Example 5

[0135] This example provides Cat-5 catalyst (1 wt% Pd-Zn 0.33 W 0.67 O), and the Cat-5 catalyst is prepared by the following steps:

[0136] Weigh 22.1 g of sodium tungstate, 9.8 g of zinc nitrate and 0.044 g of palladium nitrate and dissolve them in deionized water to prepare solution A; weigh 2.2 g of PVP and dissolve it in 1.5 mol / L glacial acetic acid, heat it to 60 °C and stir until completely dissolved to prepare solution B; add the prepared solution A dropwise to solution B, keep the solution temperature at 60 °C, stir for 1 h to prepare solution C. Weigh 9.9 g of urea and dissolve it in the above solution, weigh 9.2 g of ammonia water and slowly add it to the solution, keep the solution temperature at 60 °C, stir for 2.0 h and then transfer the mixture to an autoclave for crystallization, with a crystallization temperature of 180 °C and a crystallization time of 18 h. After cooling and venting, filter to obtain the solid, wash it 5 times, then dry it in an oven at 100 °C, and then calcine it in air at 500 °C for 18 h, press and crush it to 40 - 60 mesh to obtain a 1 wt% Pd-Zn 0.33 W 0.67 O catalyst, denoted as Cat-5 catalyst.

[0137] The catalyst prepared in Example 5 is a nanosphere structure crystal form. The spherical morphology is formed by the accumulation of numerous nanospheres. The particle size of a single nanosphere is 30 - 120 nm. Some rod-like structures are the crystal morphology of ZnO that has not formed a solid solution, with a length of up to 30 μm, a width of 1.5 μm, and a thickness of 600 - 900 nm.

[0138] Example 6

[0139] This example provides the preparation of Cat-6 catalyst (1wt% Pd-Zn 0.5 W 0.5 O). The Cat-6 catalyst is prepared by the following steps:

[0140] Weigh 16.5 g of sodium tungstate, 15.0 g of zinc nitrate, and 0.046 g of palladium nitrate and dissolve them in deionized water to prepare solution A; weigh 2.0 g of PVP and dissolve it in 1.5 mol / L glacial acetic acid, heat it to 60 °C and stir until completely dissolved to prepare solution B; add the prepared solution A dropwise to solution B, keep the solution temperature at 60 °C, stir for 1 h to prepare solution C. Weigh 15.5 g of urea and dissolve it in the above solution, weigh 14.2 g of ammonia water and slowly add it to the solution, keep the solution temperature at 60 °C, stir for 2.0 h, then transfer the mixed solution to an autoclave for crystallization. The crystallization temperature is 160 °C and the crystallization time is 20 h. After cooling and venting, filter to obtain the solid, wash it 5 times, then dry it in an oven at 100 °C, and then calcine it in air at 450 °C for 20 h, press and crush it to 40 - 60 mesh to obtain the 1wt% Pd-Zn 0.5 W 0.5 O catalyst, denoted as Cat-6 catalyst.

[0141] The catalyst prepared in Example 6 is a nanosphere structure crystal form. The spherical morphology is formed by the accumulation of numerous nanospheres. The particle size of a single nanosphere is 35 - 120 nm. Some rod-like structures are the crystal morphology of ZnO that has not formed a solid solution, with a length of up to 40 μm, a width of 1.5 μm, and a thickness of 800 - 950 nm.

[0142] Example 7

[0143] This example provides the preparation of Cat-7 catalyst (0.1wt% Pd-Zn 0.15 W 0.75 O). The Cat-7 catalyst is prepared by the following steps:

[0144] Weigh 28.7 g of sodium tungstate, 3.9 g of zinc nitrate, and 0.004 g of palladium nitrate and dissolve them in deionized water to prepare Solution A; weigh 4.3 g of P123 and dissolve it in 1.0 mol / L glacial acetic acid, heat it to 60 °C and stir until completely dissolved to prepare Solution B; add the prepared Solution A dropwise to Solution B, keep the solution temperature at 60 °C, stir for 1 h to prepare Solution C. Weigh 3.9 g of urea and dissolve it in the above solution, slowly add 9.1 g of ammonia water to the solution, keep the solution temperature at 60 °C, stir for 2.5 h, then transfer the mixture to an autoclave for crystallization, with a crystallization temperature of 200 °C and a crystallization time of 20 h. After cooling and venting, filter to obtain the solid, wash it 5 times, then dry it in an oven at 80 °C, and then calcine it in air at 600 °C for 5 h, press and crush it to 40 - 60 mesh to obtain a 0.1 wt% Pd-Zn 0.15 W 0.75 O catalyst, denoted as Cat-7 catalyst.

[0145] The catalyst prepared in Example 7 has a nanosphere structure crystal form. The spherical morphology is formed by the accumulation of countless nanospheres. The particle size of a single nanosphere is 45 - 120 nm. Some rod-like structures are the crystal morphology of ZnO that has not formed a solid solution, with a length of up to 30 μm, a width of 1 μm, and a thickness of 400 - 600 nm.

[0146] Example 8

[0147] This example provides Cat-8 catalyst (0.1 wt% Pd-Zn 0.15 W 0.75 O). The difference from Example 1 is only that sodium tungstate is replaced with an equimolar amount of sodium metatungstate, zinc nitrate is replaced with an equimolar amount of zinc carbonate, and palladium nitrate is replaced with an equidoped amount of palladium acetate, and other steps are the same as those in Example 1.

[0148] Example 9

[0149] This example provides Cat-9 catalyst (0.1 wt% Pd-Zn 0.15 W 0.75 O). The difference from Example 1 is only that the crystallization temperature is 140 °C and the crystallization time is 50 h, and other steps are the same as those in Example 1.

[0150] Example 10

[0151] This example provides Cat-10 catalyst (0.1 wt% Pd-Zn 0.15 W 0.75 O). The difference from Example 1 is only that the crystallization temperature is 220 °C and the crystallization time is 12 h, and other steps are the same as those in Example 1.

[0152] Example 11

[0153] This example provides a Cat-11 catalyst (0.1 wt% Pd-Zn 0.15 W 0.75 O). The difference from Example 1 is only that the calcination temperature is 250 °C and the calcination time is 25 h, and other steps are the same as those in Example 1.

[0154] Example 12

[0155] This example provides a Cat-12 catalyst (0.1 wt% Pd-Zn 0.15 W 0.75 O). The difference from Example 1 is only that the calcination temperature is 650 °C and the calcination time is 4 h, and other steps are the same as those in Example 1.

[0156] Comparative Example 1

[0157] This comparative example provides a catalyst (Zn 0.15 W 0.75 O). The catalyst is prepared by the following steps:

[0158] Weigh 28.7 g of sodium tungstate and 3.9 g of zinc nitrate and dissolve them in deionized water to prepare solution A; weigh 2.3 g of PVP and dissolve it in 1.0 mol / L glacial acetic acid, heat to 60 °C and stir until completely dissolved to prepare solution B; add the prepared solution A dropwise to solution B, keep the solution temperature at 60 °C, stir for 1 h to prepare solution C. Weigh 6.2 g of urea and dissolve it in the above solution, keep the solution temperature at 60 °C, stir for 2.5 h, then transfer the mixed solution to an autoclave for crystallization, the crystallization temperature is 180 °C, and the crystallization time is 20 h. After cooling and venting, filter to obtain the solid, wash it 5 times, then dry it in an oven at 80 °C, and then calcine it in air at 500 °C for 18 h, press and crush it to 40-60 mesh to obtain the Zn 0.15 W 0.75 O catalyst.

[0159] Comparative Example 2

[0160] This comparative example provides a catalyst (0.1 wt% Pt-Zn 0.15 W 0.75 O). The Cat-1 catalyst is prepared by the following steps:

[0161] Weigh 28.7 g of sodium tungstate, 3.9 g of zinc nitrate, and 0.004 g of platinum nitrate and dissolve them in deionized water to prepare Solution A; weigh 2.3 g of PVP and dissolve it in 1.0 mol / L glacial acetic acid, heat it to 60 °C and stir until completely dissolved to prepare Solution B; add the prepared Solution A dropwise to Solution B, keep the solution temperature at [temperature value] °C, stir for 1 h to prepare Solution C. Weigh 6.2 g of urea and dissolve it in the above solution, keep the solution temperature at 60 °C, stir for 2.5 h, then transfer the mixture to an autoclave for crystallization, with a crystallization temperature of 180 °C and a crystallization time of 20 h. After cooling and venting, filter to obtain the solid, wash it 5 times, then dry it in an oven at 80 °C, and then calcine it in air at 500 °C for 18 h, press and crush it to 40 - 60 mesh to obtain 0.1 wt% Pt-Zn 0.15 W 0.75 O catalyst.

[0162] Comparative Example 3

[0163] This comparative example provides a catalyst (0.1 wt% Pd-WO3), and the Cat-1 catalyst is prepared by the following steps:

[0164] Weigh 32.6 g of sodium tungstate and 0.004 g of palladium nitrate and dissolve them in deionized water to prepare Solution A; weigh 2.3 g of PVP and dissolve it in 1.0 mol / L glacial acetic acid, heat it to 60 °C and stir until completely dissolved to prepare Solution B; add the prepared Solution A dropwise to Solution B, keep the solution temperature at 80 °C, stir for 1 h to prepare Solution C. Weigh 6.2 g of urea and dissolve it in the above solution, keep the solution temperature at 60 °C, stir for 2.5 h, then transfer the mixture to an autoclave for crystallization, with a crystallization temperature of 180 °C and a crystallization time of 20 h. After cooling and venting, filter to obtain the solid, wash it 5 times, then dry it in an oven at 80 °C, and then calcine it in air at 500 °C for 18 h, press and crush it to 40 - 60 mesh to obtain 0.1 wt% Pd-WO3 catalyst.

[0165] Comparative Example 4

[0166] This comparative example provides a catalyst (0.1 wt% Pd-Cu 0.15 W 0.75 O), and the Cat-1 catalyst is prepared by the following steps:

[0167] It should be noted that the [temperature value] in the translation of needs to be filled with the specific temperature value in the original text.Weigh 28.7 g of sodium tungstate, 3.6 g of copper nitrate, and 0.0034 g of palladium nitrate and dissolve them in deionized water to prepare Solution A; weigh 2.3 g of PVP and dissolve it in 1.0 mol / L glacial acetic acid, heat it to 60 °C and stir until completely dissolved to prepare Solution B; add the prepared Solution A dropwise to Solution B, keep the solution temperature at 80 °C, stir for 1 h to prepare Solution C. Weigh 6.2 g of urea and dissolve it in the above solution, keep the solution temperature at 60 °C, stir for 2.5 h, then transfer the mixture to an autoclave for crystallization, with a crystallization temperature of 180 °C and a crystallization time of 20 h. After cooling and venting, filter to obtain the solid, wash it 5 times, then dry it in an oven at 80 °C, and then calcine it in air at 500 °C for 18 h, press and crush it to 40 - 60 mesh to obtain a 0.1 wt% Pd-Cu 0.15 W 0.75 O catalyst.

[0168] Test Example 1

[0169] Test samples: The catalysts provided in Examples 1 - 12 and the catalysts provided in Comparative Examples 1 - 4.

[0170] Test method: Use a 5 mL fixed-bed reactor, with a catalyst loading of 1.0 g, diluted with 1.0 g of fine quartz sand, a reducing atmosphere of 5% H2 - 95% N2, a flow rate of 80 mL / min, a reduction temperature of 350 °C, and a reduction time of 8 h. After the reduction process is completed, use N2 to flush the pressure to 5.0 MPa, maintain a reaction temperature of 320 °C, and an inlet feed gas space velocity of 24000 h -1 , with the feed gas composition H2 / CO2 = 3.0, and start the reaction after the temperature and pressure are stable.

[0171] Tail gas analysis method: The reaction tail gas products are analyzed by on-line chromatography. The tail gas analysis conditions are: the chromatographic column is Porapak-T, the column temperature is 90 °C, the carrier gas is argon, the flow rate is 25 mL / min, the current is 60 mA, the liquid-phase products are collected by a cold trap, taken out and analyzed by chromatography. The analysis conditions are: the chromatographic column is TDX-01, the column temperature is 160 °C, the carrier gas is argon, the flow rate is 30 mL / min, and the current is 60 mA.

[0172] The test results are shown in Table 1 below:

[0173] Table 1

[0174]

[0175] Test Example 2

[0176] Test sample: The catalyst provided in Example 1.

[0177] Testing method: A 5 mL fixed-bed reactor was used. The catalyst was the catalyst Cat-1 provided in Example 1, with a loading amount of 1.0 g, diluted with 1.0 g of fine quartz sand. The reduction atmosphere was 5% H2 - 95% N2, the flow rate was 80 mL / min, the reduction temperature was 350 °C, and the reduction time was 8 h. After the reduction process was completed, the temperature was lowered to 300 °C, and the pressure was flushed to 8.0 MPa with N2. Different reaction temperatures were investigated, and the space velocity of the feed gas was 24000 h -1 , and the feed gas composition was H2 / CO2 = 3.0. The reaction started after the temperature and pressure were stabilized.

[0178] Tail gas analysis method: Online chromatography analysis was used. The tail gas analysis conditions were as follows: The chromatographic column was Porapak-T, the column temperature was 90 °C, the carrier gas was argon, the flow rate was 25 mL / min, and the current was 60 mA. The liquid-phase products were collected by a cold trap, taken out and analyzed by chromatography. The analysis conditions were: The chromatographic column was TDX-01, the column temperature was 160 °C, the carrier gas was argon, the flow rate was 30 mL / min, and the current was 60 mA.

[0179] The reaction performance of the Cat-1 catalyst at different temperatures is shown in Table 2 below:

[0180] Table 2

[0181]

[0182] Test Example 3

[0183] Test sample: The catalyst provided in Example 4.

[0184] Testing method: A 5 mL fixed-bed reactor was used. The catalyst was the catalyst Cat-4 provided in Example 4, with a loading amount of 1.0 g, diluted with 1.0 g of fine quartz sand. The reduction atmosphere was 5% H2 - 95% N2, the flow rate was 80 mL / min, the reduction temperature was 350 °C, and the reduction time was 8 h. After the reduction process was completed, the temperature was lowered to 320 °C, and the pressure was flushed to a certain pressure with N2. Different reaction pressures were investigated, and the space velocity of the feed gas was 24000 h -1 , and the feed gas composition was H2 / CO2 = 3.0. The reaction started after the temperature and pressure were stabilized.

[0185] Tail gas analysis method: Online chromatography analysis was used. The tail gas analysis conditions were as follows: The chromatographic column was Porapak-T, the column temperature was 90 °C, the carrier gas was argon, the flow rate was 25 mL / min, and the current was 60 mA. The liquid-phase products were collected by a cold trap, taken out and analyzed by chromatography. The analysis conditions were: The chromatographic column was TDX-01, the column temperature was 160 °C, the carrier gas was argon, the flow rate was 30 mL / min, and the current was 60 mA.

[0186] The reaction performance of the catalyst at different pressures is shown in Table 3 below:

[0187] Table 3

[0188]

[0189] In summary, the present invention provides a new Pd-precious metal-doped ZnWO3 solid solution catalyst and its preparation method, and the reaction performance is evaluated in a fixed-bed reactor. It has the characteristics of high activity, high methanol selectivity, and long-term stable operation at higher temperatures and pressures, providing broad prospects for subsequent industrial applications and coupling the subsequent methanol conversion processes (MTO, MTG).

[0190] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A catalyst for hydrogenating carbon dioxide to methanol, characterized in that, The catalyst includes a metal oxide solid solution and palladium elements doped in the metal oxide solid solution; Among them, the metal oxide solid solution includes a zinc oxide-tungsten oxide composite.

2. The catalyst for hydrogenating carbon dioxide to methanol according to claim 1, wherein The chemical formula of the zinc oxide-tungsten oxide composite is Zn x W y O; Among them, x:y = 1:(1-10).

3. The catalyst for hydrogenating carbon dioxide to methanol according to claim 1, wherein The doping amount of palladium elements in the catalyst is 0.1-1.0 wt%.

4. The catalyst for hydrogenating carbon dioxide to methanol according to claim 1, characterized in that, The crystal morphology structure of the catalyst includes a nanosphere structure; Preferably, the catalyst is formed by stacking nanospheres, the nanospheres are metal oxide solid solutions, and the metal oxide solid solutions include zinc oxide-tungsten oxide composites; Preferably, the particle size of a single nanosphere is 10-300 nm; Preferably, the catalyst also includes a rod-like structure, the rod-like structure is a metal oxide that does not form a solid solution, and the metal oxide that does not form a solid solution is zinc oxide; Preferably, the length of the rod-like structure is 20-40 μm, the width of the rod-like structure is 0.5-2.0 μm, and the thickness of the rod-like structure is 500-800 nm.

5. A method for preparing a catalyst for hydrogenating carbon dioxide to methanol according to any one of claims 1 to 4, characterized in that, The preparation method includes the following steps: Dissolve a tungsten salt, a zinc salt, and a palladium salt in water to obtain solution A; Dissolve a surfactant in an acid solution to obtain solution B; Add solution A to solution B, and perform the first mixing and stirring to obtain solution C; Add a precipitant to solution C, perform the second mixing and stirring, and then carry out a crystallization reaction to obtain a crystallized solid; Filter, wash, and dry the crystallized solid, and then carry out calcination, tabletting, and pulverization to obtain the catalyst for hydrogenating carbon dioxide to methanol.

6. The preparation method of the catalyst for hydrogenating carbon dioxide to methanol according to claim 5, characterized in that, The molar ratio of zinc elements in the zinc salt to tungsten elements in the tungsten salt is (0.15-1):1; Preferably, the zinc salt is selected from water-soluble zinc salts, preferably any one or at least two combinations of zinc nitrate, zinc carbonate, or zinc sulfate, and more preferably zinc nitrate; Preferably, the tungsten salt is selected from water-soluble tungsten salts, preferably sodium tungstate and / or sodium metatungstate, and more preferably sodium tungstate; Preferably, the palladium salt is selected from water-soluble palladium salts, preferably palladium nitrate and / or palladium acetate, and more preferably palladium nitrate; Preferably, the surfactant is selected from PVP and / or P123; Preferably, the mass ratio of the tungsten salt to the surfactant is 100:(5-15); Preferably, the acid solution is selected from acetic acid solutions; Preferably, the concentration of the acid solution is 0.5-3.0 mol / L, preferably 1.0-1.5 mol / L; Preferably, the temperature at which the surfactant is dissolved in the acid solution is 40-80 °C; Preferably, the temperature of the first mixing and stirring is 40-80 °C, and the time of the first mixing and stirring is 0.5-2.5 h.

7. The preparation method of the catalyst for hydrogenating carbon dioxide to methanol according to claim 5, characterized in that, The precipitant is selected from urea and / or ammonia water, preferably urea and ammonia water; Preferably, the molar ratio of urea to zinc elements in the zinc salt is (5-10):1; Preferably, the molar ratio of ammonia water to zinc elements in the zinc salt is (2-8):1; Preferably, the temperature of the second mixing and stirring is 40-80 °C, and the time of the second mixing and stirring is 0.5-2.5 h; Preferably, the temperature of the crystallization reaction is 150 - 200 °C, and the time of the crystallization reaction is 15 - 48 h; Preferably, the temperature of the drying is 80 - 120 °C; Preferably, the temperature of the calcination is 300 - 600 °C, and the time of the calcination is 5 - 24 h; Preferably, the particle size of the catalyst for hydrogenating carbon dioxide to methanol is 40 - 60 mesh.

8. Use of the catalyst for hydrogenating carbon dioxide to methanol according to any one of claims 1 - 4 as a catalyst for hydrogenating carbon dioxide to methanol.

9. A method for hydrogenating carbon dioxide to methanol, characterized in that, The method comprises the following steps: In the presence of a catalyst, a raw material gas containing carbon dioxide and hydrogen undergoes a hydrogenation reaction to obtain methanol; wherein, the catalyst comprises the catalyst for hydrogenating carbon dioxide to methanol according to any one of claims 1 - 4.

10. The method for hydrogenating carbon dioxide to methanol according to claim 9, characterized in that, The hydrogenation reaction is carried out in a fixed bed reactor; Preferably, the space velocity of the feed gas is 2000 - 26000 h -1 ; Preferably, the molar ratio of carbon dioxide to hydrogen in the raw material gas is (2 - 4):1; Preferably, the temperature of the hydrogenation reaction is 300 - 400 °C, and the pressure of the hydrogenation reaction is 2.0 - 10.0 MPa.

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