CN114160117A

CN114160117A - A kind of catalyst for preparing methanol by CO2 hydrogenation, its preparation method and use

Info

Publication number: CN114160117A
Application number: CN202111492078.6A
Authority: CN
Inventors: 孙予罕; 王慧; 吴兆萱; 王浩渺; 黄超杰; 夏林
Original assignee: Shanghai Cluster Rui Low Carbon Energy Technology Co ltd; Shanghai Advanced Research Institute of CAS
Current assignee: Shanghai Cluster Rui Low Carbon Energy Technology Co ltd; Shanghai Advanced Research Institute of CAS
Priority date: 2021-12-08
Filing date: 2021-12-08
Publication date: 2022-03-11

Abstract

本发明提供一种CO₂加氢制备甲醇的催化剂及其制备方法和用途。该催化剂为金属氧化物固溶体，所述金属氧化物固溶体的通式为Zn_xM_1‑xO，其中，x为0.05～0.3，M选自Ce、Cr和Ga中的至少一种。该制备方法包括如下步骤：1)将锌盐和M元素的盐共沉淀；2)将步骤1)得到的产物进行过滤和焙烧，得到所述催化剂。该催化剂在二氧化碳加氢制备甲醇中的用途。CO₂和H₂在该催化剂存在下进行反应，获得甲醇。本发明催化剂可在高温即高于300℃条件下运行，并具有较高的甲醇选择性，为后续工业应用以及耦合甲醇后续转化过程(MTO，MTG)提供了广泛前景。The present invention provides a catalyst for preparing methanol by hydrogenation of CO ₂ , and a preparation method and application thereof. The catalyst is a metal oxide solid solution, and the general formula of the metal oxide solid solution is Zn _x M _1-x O, wherein x is 0.05-0.3, and M is selected from at least one of Ce, Cr and Ga. The preparation method includes the following steps: 1) co-precipitating zinc salt and salt of M element; 2) filtering and calcining the product obtained in step 1) to obtain the catalyst. Use of the catalyst in the hydrogenation of carbon dioxide to prepare methanol. _CO2 and _H2 react in the presence of this catalyst to obtain methanol. The catalyst of the invention can operate at a high temperature, that is, higher than 300° C., and has high methanol selectivity, which provides broad prospects for subsequent industrial applications and coupled methanol subsequent conversion processes (MTO, MTG).

Description

CO (carbon monoxide)2Catalyst for preparing methanol by hydrogenation, preparation method and application thereof

Technical Field

The invention relates to CO₂The technical field of hydrogenation catalytic conversion, in particular to CO₂A catalyst for preparing methanol by hydrogenation, a preparation method and application thereof.

Background

The combustion of carbon-based fossil fuels for power generation (oil, coal and natural gas) is accompanied by the emission of large quantities of anthropogenic greenhouse gases (GHG), mainly CO, into the atmosphere₂Is discharged in the form of (1). 2018 year global CO₂About 33 hundred million tons of CO are emitted₂Increased from 280ppm to 410ppm before the industrial revolution. The resulting greenhouse effect leads to significant environmental effects such as global warming, ocean acidification, sea level elevation, and climate change. Thus, green carbon science, including efficient carbon resource processing, utilization and recycling, is of great significance to close carbon cycles, reduce emissions, mitigate greenhouse effects, and reduce dependence on fossil fuels. Compared with Carbon Capture and Sequestration (CCS) technology, the method can not only reduce greenhouse gas emission and fossil resource consumption, but also recover CO through the processes of thermocatalysis, electrocatalysis and photocatalysis₂Preparing fuel, chemicals and materials with high added value. At present, CO is directly utilized₂The chemical industry as raw materials comprises synthetic urea, methanol (additive for synthesis gas), carbonates, carboxylic acids, etc. Wherein heterogeneous catalysis has several advantages in terms of stability, separation, catalyst recovery and reactor design. In particular CO₂The heterogeneous catalytic hydrogenation of hydrogen can produce a variety of high value-added fuels and chemicals, such as methanol, dimethyl ether (DME), hydrocarbons (lower olefins, gasoline, aromatics, etc.), methane, carbon monoxide, formates, and formic acid.

Methanol is an important chemical intermediate raw material, and can be used as raw materialAs the fuel of internal combustion engines and fuel cells, along with the gradual reduction of non-renewable energy sources, methanol as a replaceable chemical raw material can synthesize various chemicals and fuels such as gasoline and the like. The dimethyl ether which is the product of methanol dehydration has a high cetane number of 55-60, and is an excellent diesel fuel substitute and household fuel gas. Dimethyl ether can also replace Liquefied Petroleum Gas (LPG) and Liquefied Natural Gas (LNG) in most applications. In addition to being a key raw material for various chemicals such as formaldehyde and methyl, tertiary butyl ether (MTBE), acetic acid, alkyl halides and the like, methanol can be further converted into hydrocarbons and various chemical products obtained from petrochemical resources and fossil resources. In recent years, with the development of technologies such as a molecular sieve catalyst, Methanol To Olefin (MTO), Methanol to aromatic (MTG), and the like, the Demand of a fuel obtained from Methanol in the international market has been rapidly increasing (Johnson, d.global Methanol Demand Growth; IHS inc., 2016). The traditional industrial preparation of methanol adopts a synthesis gas conversion method, but mainly faces to a catalyst (Cu/ZnO/Al)₂O₃) The active sites are easy to sinter under the reaction conditions, which causes poor stability, and moreover, the raw material synthesis gas output of the process is often accompanied with the consumption of fossil resources such as coal, natural gas and the like and CO caused by the conversion process₂Discharge and environmental pollution.

At present, CO₂The hydrogenation for preparing methanol mainly adopts a supported metal or metal oxide catalyst, such as traditional Cu/ZnO/Al₂O₃,Cu/ZrO₂The conventional Cu-based catalyst has a very low methanol selectivity at temperatures above 300 ℃.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, it is an object of the present invention to provide a CO₂The catalyst for preparing methanol by hydrogenation, the preparation method and the application thereof can operate at high temperature, namely higher than 300 ℃, have higher methanol selectivity and provide wide prospects for subsequent industrial application and coupling with subsequent methanol conversion processes (MTO, MTG).

To achieve the above and other related objects, the first aspect of the present invention provides a CO₂Catalyst for preparing methanol by hydrogenation, wherein the catalyst is a solid solution of metal oxideA body of a solid solution of said metal oxide of the general formula Zn_xM_1-xO, wherein x is 0.05 to 0.3, such as 0.05 to 0.1, 0.1 to 0.15, 0.15 to 0.2, 0.2 to 0.25 or 0.25 to 0.3, and M is at least one selected from Ce, Cr and Ga.

The second aspect of the present invention provides a method for preparing the above catalyst, comprising the steps of:

1) co-precipitating a zinc salt and a salt of the M element;

2) filtering, washing, drying and roasting the product obtained in the step 1) to obtain the catalyst.

Preferably, at least one of the following technical features is also included:

11) in the step 1), the zinc salt is selected from at least one of zinc nitrate and zinc sulfate;

12) in the step 1), the salt of the M element is selected from at least one of cerous nitrate, chromium nitrate and gallium nitrate;

13) in step 1), the coprecipitation specifically includes the following steps: reacting an aqueous solution containing a zinc salt and a salt of an M element with an alkaline solution;

14) in step 1), the temperature of the coprecipitation is 60-80 ℃, such as 60-70 ℃ or 70-80 ℃, and can be 60 ℃, 65 ℃, 70 ℃, 75 ℃ or 80 ℃.

21) In the step 2), the drying temperature is 50-80 ℃, such as 50-60 ℃ or 60-80 ℃;

22) in the step 2), the roasting temperature is 450-550 ℃, for example 450-500 ℃ or 500-550 ℃.

More preferably, in feature 13), at least one of the following technical features is further included:

131) the alkali solution is ammonium carbonate aqueous solution;

132) the concentration of the alkali solution is 0.30-0.32 mol/L, such as 0.30-0.315 mol/L or 0.315-0.32 mol/L;

133) the molar ratio of the total metal elements to the alkali in the aqueous solution containing the zinc salt and the salt of the M element is 1: 1.4-1: 1.6, as 1: 1.4-1: 1.5 or 1: 1.5-1: 1.6.

more preferably, in the feature 13), the concentration of the total metal element in the aqueous solution containing the zinc salt and the salt of the M element is 0.190 to 0.204mol/L, such as 0.190 to 0.192mol/L, 0.192 to 0.193mol/L, 0.193 to 0.195mol/L, 0.195 to 0.196mol/L, 0.196 to 0.198mol/L, or 0.198 to 0.204 mol/L.

In a third aspect, the present invention provides the use of the above catalyst in the hydrogenation of carbon dioxide to produce methanol.

Preferably, the catalyst is subjected to hydrogenation reduction prior to use in the hydrogenation of carbon dioxide to produce methanol.

More preferably, at least one of the following technical characteristics is also included:

1) the temperature of the hydrogenation reduction is 300-400 ℃, such as 300-320 ℃, 320-360 ℃ or 360-400 ℃, and can be 300 ℃, 350 ℃ or 400 ℃;

2) the hydrogenation reduction time is 6-16 h, such as 6-12 h or 12-16 h, and can be 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h or 16 h;

3) the hydrogenation reduction pressure is 0.01-0.5 MPa, such as 0.01-0.1 MPa or 0.1-0.5 MPa, and may be 0.05MPa, 0.1MPa, 0.15MPa, 0.2MPa, 0.25MPa, 0.3MPa, 0.35MPa, 0.4MPa, 0.45MPa or 0.5 MPa;

4) the space velocity of hydrogen for hydrogenation reduction is 2500-3500 ml/g/h, such as 2500-3000 ml/g/h or 3000-3500 ml/g/h.

In a fourth aspect, the present invention provides a CO₂Method for preparing methanol by hydrogenation, CO₂And H₂The reaction is carried out in the presence of the above catalyst to obtain methanol.

Preferably, at least one of the following technical features is also included:

1)CO₂and H₂Is 1: 2-1: 7, as shown in 1: 2-1: 3 or 1: 3-1: 7; more preferably, CO₂And H₂The volume ratio of (A) to (B) is 1: 3;

2) the reaction temperature is 300-400 ℃, such as 300-320 ℃ or 320-400 ℃; more preferably, the reaction temperature is 320 ℃;

3) the reaction pressure is 2-7 MPa, such as 2-5 MPa or 5-7 MPa; more preferably, the reaction pressure is 5 MPa;

4) the reaction space velocity is 5000-24000 ml/g/h.

As described above, the invention has at least one of the following advantageous effects:

1) the invention dopes metal Zn into MO_xIn the crystal lattice, H is dissociated by ZnO₂The characteristic of strong performance, improves the reaction activity of the catalyst, and utilizes M³⁺/M⁴⁺The proportion is regulated and controlled, so that the crystal lattice of the oxide solid solution is subjected to expansion strain, the catalytic performance of the oxide solid solution is effectively regulated and controlled, and meanwhile Zn can help cerium oxide to resist sintering and generate more oxygen vacancies.

2) The catalyst has excellent catalytic performance and methanol selectivity, has a stable structure particularly at high temperature and pressure, stably runs for a long time, and provides wide prospects for subsequent industrial application and coupling methanol subsequent conversion processes (MTO, MTG).

3) The catalyst of the invention can operate under high temperature condition and has higher methanol selectivity.

4) The catalyst of the invention can cause Zn through regulating and controlling the doping amount of M_xM_1-xThe change of the number of oxygen vacancies of O solid solution, thereby changing the selectivity of methanol, proves that the improvement of the doping amount of M has better CO in the reaction₂Conversion rate and methanol yield, and is beneficial to large-scale industrial application.

5) The preparation process of the catalyst is simple and easy to repeat, and the catalyst can be prepared in a large scale.

Drawings

Fig. 1 is an XRD spectrum of the catalysts of examples 1 to 6.

FIG. 2 is an electron micrograph of the catalyst of example 3.

Detailed Description

The invention is further illustrated by the following examples. It should be understood that these examples are only for illustrating the present invention, and are not to be construed as limiting the scope of the present invention. The experimental methods and reagents of the formulations not specified in the following examples were carried out or configured according to the conventional conditions or the conditions recommended by the manufacturers.

Example 1

Preparation of ZnCe oxide by coprecipitation methodSolid solution of matter (Zn)_xCe_1-xO). Zinc nitrate and cerous nitrate in a molar ratio of 0.05:0.95 are dissolved in 240mL of deionized water to form a salt solution A (the mass of the added two nitrates is 0.5g and 14g respectively), and the solution is stirred for 1h at 30 ℃. 6.660g of ammonium carbonate was dissolved in 220mL of deionized water and thoroughly stirred to form an alkali solution B. The A solution was transferred to a round bottom flask and preheated in a 70 ℃ oil bath, then the B solution was added to the round bottom flask with a peristaltic pump at 3ml/min under nitrogen purge, after which stirring was continued at 70 ℃ for 3 h. Cooling the obtained precipitate to room temperature, separating the precipitate from the solution under high-speed centrifugation, washing the precipitate with deionized water, centrifuging again, repeating the steps for three times, drying the precipitate at 60 ℃ for 12 hours, and roasting in the air at 500 ℃ for 3 hours to obtain the ZnCe oxide solid solution (Zn)_xCe_1-xO) catalyst (x ═ 0.05).

The obtained ZnCe oxide solid solution (Zn)_xCe_1-xO) catalyst is placed in a fixed bed high-pressure micro reactor, hydrogen is introduced to carry out reduction under normal pressure, the reduction space velocity is 3000ml/g/H, the reduction temperature is 400 ℃, the reduction time is 12H, after the reduction process is finished, the reaction furnace is cooled to the room temperature, and H is introduced₂/CO₂The reaction is carried out by the reaction gas with the ratio of 3, the reaction pressure is 5MPa, and the reaction space velocity is 5000ml g^-1·h^-1The reaction temperature was 320 ℃ and the results of activity evaluation are shown in Table 1.

Example 2

Preparation of ZnCe oxide solid solution (Zn) by coprecipitation method_xCe_1-xO). Zinc nitrate and cerous nitrate in a molar ratio of 0.1:0.9 are dissolved in 240mL of deionized water to form a salt solution A (the mass of the added two nitrates is 1g and 13.3g respectively), and the solution is stirred for 1h at 30 ℃. 6.660g of ammonium carbonate was dissolved in 220mL of deionized water and thoroughly stirred to form an alkali solution B. The A solution was transferred to a round bottom flask and preheated in a 70 ℃ oil bath, then the B solution was added to the round bottom flask with a peristaltic pump at 3ml/min under nitrogen purge, after which stirring was continued at 70 ℃ for 3 h. Cooling the precipitate to room temperature, separating the precipitate from the solution under high speed centrifugation, washing the precipitate with deionized water, centrifuging again, repeating the process for three times, and drying the precipitate at 60 deg.CDrying for 12h, and then roasting for 3 hours at 500 ℃ in the air to obtain ZnCe oxide solid solution (Zn)_xCe_1-xO) catalyst (x ═ 0.1).

Example 3

Preparation of ZnCe oxide solid solution (Zn) by coprecipitation method_xCe_1-xO). Zinc nitrate and cerous nitrate in a molar ratio of 0.15:0.85 are dissolved in 240mL of deionized water to form a salt solution A (the mass of the added two nitrates is 1.5g and 12.5g respectively), and the solution is stirred for 1h at 30 ℃. 6.660g of ammonium carbonate was dissolved in 220mL of deionized water and thoroughly stirred to form an alkali solution B. The A solution was transferred to a round bottom flask and preheated in a 70 ℃ oil bath, then the B solution was added to the round bottom flask with a peristaltic pump at 3ml/min under nitrogen purge, after which stirring was continued at 70 ℃ for 3 h. Cooling the obtained precipitate to room temperature, separating the precipitate from the solution under high-speed centrifugation, washing the precipitate with deionized water, centrifuging again, repeating the steps for three times, drying the precipitate at 60 ℃ for 12 hours, and roasting in the air at 500 ℃ for 3 hours to obtain the ZnCe oxide solid solution (Zn)_xCe_1-xO) catalyst (x ═ 0.15).

Example 4

Preparation of ZnCe oxide solid solution (Zn) by coprecipitation method_xCe_1-xO). Zinc nitrate and cerous nitrate in a molar ratio of 0.2:0.8 are dissolved in 240mL of deionized water to form a salt solution A (the mass of the added two nitrates is 2g and 11.8g respectively), and the solution is stirred at 30 ℃ for 1 h. 6.660g of ammonium carbonate was dissolved in 220mL of deionized water and thoroughly stirred to form an alkali solution B. The A solution was transferred to a round bottom flask and preheated in a 70 ℃ oil bath, then the B solution was added to the round bottom flask with a peristaltic pump at 3ml/min under nitrogen purge, after which stirring was continued at 70 ℃ for 3 h. Cooling the obtained precipitate to room temperature, separating the precipitate from the solution under high-speed centrifugation, washing the precipitate with deionized water, centrifuging again, repeating the steps for three times, drying the precipitate at 60 ℃ for 12 hours, and roasting in the air at 500 ℃ for 3 hours to obtain the ZnCe oxide solid solution (Zn)_xCe_1-xO) catalyst (x ═ 0.2).

Example 5

Preparation of ZnCe oxide solid solution (Zn) by coprecipitation method_xCe_1-xO). Zinc nitrate and cerous nitrate in a molar ratio of 0.25:0.75 are dissolved in 240mL of deionized water to form a salt solution A (the mass of the added two nitrates is 2.5g and 11.05g respectively), and the solution is stirred for 1h at 30 ℃. 6.660g of ammonium carbonate was dissolved in 220mL of deionized water and thoroughly stirred to form an alkali solution B. The A solution was transferred to a round bottom flask and preheated in a 70 ℃ oil bath, then the B solution was added to the round bottom flask with a peristaltic pump at 3ml/min under nitrogen purge, after which stirring was continued at 70 ℃ for 3 h. Cooling the obtained precipitate to room temperature, and separating at high speedSeparating the precipitate and the solution under the heart, washing the precipitate with deionized water, centrifuging again, repeating for three times, drying the precipitate at 60 ℃ for 12h, and then roasting in the air at 500 ℃ for 3h to obtain ZnCe oxide solid solution (Zn)_xCe_1-xO) catalyst (x ═ 0.25).

Example 6

Preparation of ZnCe oxide solid solution (Zn) by coprecipitation method_xCe_1-xO). Dissolving zinc nitrate and cerous nitrate in a molar ratio of 0.3:0.7 in 240mL of deionized water to form a salt solution A (the mass of the added two nitrates is 3g and 10.3g respectively), and stirring at 30 ℃ for 1 h. 6.660g of ammonium carbonate was dissolved in 220mL of deionized water and thoroughly stirred to form an alkali solution B. The A solution was transferred to a round bottom flask and preheated in a 70 ℃ oil bath, then the B solution was added to the round bottom flask with a peristaltic pump at 3ml/min under nitrogen purge, after which stirring was continued at 70 ℃ for 3 h. Cooling the obtained precipitate to room temperature, separating the precipitate from the solution under high-speed centrifugation, washing the precipitate with deionized water, centrifuging again, repeating the steps for three times, drying the precipitate at 60 ℃ for 12 hours, and roasting in the air at 500 ℃ for 3 hours to obtain the ZnCe oxide solid solution (Zn)_xCe_1-xO) catalyst (x ═ 0.3).

The obtained ZnCe oxide solid solution (Zn)_xCe_1-xO) catalyst is placed in a fixed bed high-pressure micro reactor, hydrogen is introduced to carry out reduction under normal pressure, the reduction space velocity is 3000ml/g/H, the reduction temperature is 400 ℃, the reduction time is 12H, after the reduction process is finished, the reaction furnace is cooled to the room temperature, and H is introduced₂/CO₂The reaction gas with the ratio of 3 is reacted with the reaction pressure of 5MPa, reaction space velocity of 5000ml g^-1·h^-1The reaction temperature was 320 ℃ and the results of activity evaluation are shown in Table 1.

The XRD patterns of the catalysts of examples 1 to 6 are shown in FIG. 1, and if the XRD patterns are enlarged in the range of 25 to 30 degrees in the XRD pattern, CeO can be seen as increasing the Zn content from 0 to 15 percent₂The diffraction peak shifts to a high angle, indicating that the Zn atom is doped with CeO₂The interplanar spacing is reduced, while an electron micrograph of the catalyst of example 3, see fig. 2, shows CeO₂The change of the interplanar spacing shows that the catalysts of examples 1 to 6 are solid solutions and the catalyst structure is stable.

Example 7

Preparation of ZnCe oxide solid solution (Zn) by coprecipitation method_xCe_1-xO). Zinc nitrate and cerous nitrate in a molar ratio of 0.05:0.95 are dissolved in 240mL of deionized water to form a salt solution A (the mass of the added two nitrates is 0.5g and 14g respectively), and the solution is stirred for 1h at 30 ℃. 6.660g of ammonium carbonate was dissolved in 220mL of deionized water and thoroughly stirred to form an alkali solution B. The A solution was transferred to a round bottom flask and preheated in a 70 ℃ oil bath, then the B solution was added to the round bottom flask with a peristaltic pump at 3ml/min under nitrogen purge, after which stirring was continued at 70 ℃ for 3 h. Cooling the obtained precipitate to room temperature, separating the precipitate from the solution under high-speed centrifugation, washing the precipitate with deionized water, centrifuging again, repeating the steps for three times, drying the precipitate at 60 ℃ for 12 hours, and roasting in the air at 500 ℃ for 3 hours to obtain the ZnCe oxide solid solution (Zn)_xCe_1-xO) catalyst (x ═ 0.05).

The obtained ZnCe oxide solid solution (Zn)_xCe_1-xO) catalyst is placed in a fixed bed high-pressure micro reactor, hydrogen is introduced to carry out reduction under normal pressure, the reduction space velocity is 3000ml/g/H, the reduction temperature is 300 ℃, the reduction time is 12H, after the reduction process is finished, the reaction furnace is cooled to the room temperature, and H is introduced₂/CO₂The reaction is carried out by the reaction gas with the ratio of 3, the reaction pressure is 5MPa, and the reaction space velocity is 5000ml g^-1·h^-1The reaction temperature was 320 ℃ and the results of activity evaluation are shown in Table 1.

Example 8

The obtained ZnCe oxide solid solution (Zn)_xCe_1-xO) catalyst is placed in a fixed bed high-pressure micro reactor, hydrogen is introduced to carry out reduction under normal pressure, the reduction space velocity is 3000ml/g/H, the reduction temperature is 320 ℃, the reduction time is 12H, after the reduction process is finished, the reaction furnace is cooled to the room temperature, and H is introduced₂/CO₂The reaction is carried out by the reaction gas with the ratio of 3, the reaction pressure is 5MPa, and the reaction space velocity is 5000ml g^-1·h^-1The reaction temperature was 320 ℃ and the results of activity evaluation are shown in Table 1.

Example 9

Preparation of ZnCe oxide solid solution (Zn) by coprecipitation method_xCe_1-xO). Zinc nitrate and cerous nitrate in a molar ratio of 0.05:0.95 are dissolved in 240mL of deionized water to form a salt solution A (the mass of the added two nitrates is 0.5g and 14g respectively), and the solution is stirred for 1h at 30 ℃. 6.660g of ammonium carbonate was dissolved in 220mL of deionized water and thoroughly stirred to form an alkali solution B. The A solution was transferred to a round bottom flask and preheated in a 70 ℃ oil bath, then the B solution was added to the round bottom flask with a peristaltic pump at 3ml/min under nitrogen purge, after which stirring was continued at 70 ℃ for 3 h. Cooling the obtained precipitate to room temperature, and separating under high speed centrifugationWashing the precipitate with deionized water, centrifuging again, repeating for three times, drying the precipitate at 60 deg.C for 12h, and calcining at 500 deg.C in air for 3 hr to obtain ZnCe oxide solid solution (Zn)_xCe_1-xO) catalyst (x ═ 0.05).

The obtained ZnCe oxide solid solution (Zn)_xCe_1-xO) catalyst is placed in a fixed bed high-pressure micro reactor, hydrogen is introduced to carry out reduction under normal pressure, the reduction space velocity is 3000ml/g/H, the reduction temperature is 360 ℃, the reduction time is 12H, after the reduction process is finished, the reaction furnace is cooled to the room temperature, and H is introduced₂/CO₂The reaction is carried out by the reaction gas with the ratio of 3, the reaction pressure is 5MPa, and the reaction space velocity is 5000ml g^-1·h^-1The reaction temperature was 320 ℃ and the results of activity evaluation are shown in Table 1.

Example 10

The obtained ZnCe oxide solid solution (Zn)_xCe_1-xO) catalyst is placed in a fixed bed high-pressure micro reactor, hydrogen is introduced to carry out reduction under normal pressure, the reduction space velocity is 3000ml/g/H, the reduction temperature is 400 ℃, the reduction time is 12H, after the reduction process is finished, the reaction furnace is cooled to the room temperature, and H is introduced₂/CO₂Reaction gas with the ratio of 3 is reacted under the reaction pressure of 5MPaThe airspeed should be 24000ml g^-1·h^-1The reaction temperature was 320 ℃ and the results of activity evaluation are shown in Table 1.

TABLE 1 catalytic Performance data in examples 1 to 10

The above examples are intended to illustrate the disclosed embodiments of the invention and are not to be construed as limiting the invention. In addition, various modifications of the methods and compositions set forth herein, as well as variations of the methods and compositions of the present invention, will be apparent to those skilled in the art without departing from the scope and spirit of the invention. While the invention has been specifically described in connection with various specific preferred embodiments thereof, it should be understood that the invention should not be unduly limited to such specific embodiments. Indeed, various modifications of the above-described embodiments which are obvious to those skilled in the art to which the invention pertains are intended to be covered by the scope of the present invention.

Claims

1. a catalyst for preparing methanol by _CO hydrogenation, characterized in that the catalyst is a metal oxide solid solution, and the general formula of the metal oxide solid solution is Zn _x M _1-x O, wherein x is 0.05～ 0.3, M is selected from at least one of Ce, Cr and Ga.

2. the preparation method of catalyst as claimed in claim 1, is characterized in that, comprises the steps:

1) coprecipitating the zinc salt and the salt of the M element;

2) Filtering, washing, drying and calcining the product obtained in step 1) to obtain the catalyst.

3. the preparation method of catalyst as claimed in claim 2, is characterized in that, also comprises at least one in following technical characteristic:

11) In step 1), the zinc salt is selected from at least one of zinc nitrate and zinc sulfate;

12) In step 1), the salt of the M element is selected from at least one of cerous nitrate, chromium nitrate and gallium nitrate;

13) In step 1), the co-precipitation specifically includes the following steps: the aqueous solution containing the salt of zinc salt and the M element reacts with the alkaline solution;

14) in step 1), the temperature of co-precipitation is 60～80 ℃;

21) In step 2), the drying temperature is 50～80°C;

22) In step 2), the calcination temperature is 450-550°C.

4. the preparation method of catalyzer as claimed in claim 3 is characterized in that, in feature 13), also comprises at least one in following technical characteristic:

131) the alkaline solution is an aqueous ammonium carbonate solution;

132) the concentration of the alkali solution is 0.30～0.32mol/L;

133) The molar ratio of total metal elements to alkali in the aqueous solution containing zinc salt and salt of M element is 1:1.4-1:1.6.

5 . The method for preparing a catalyst according to claim 3 , wherein in feature 13), the concentration of total metal elements in the aqueous solution containing zinc salt and salt of M element is 0.190-0.204 mol/L. 6 .

6. Use of the catalyst as claimed in claim 1 in the hydrogenation of carbon dioxide to prepare methanol.

7. The use of the catalyst according to claim 6, characterized in that, before being used for hydrogenation of carbon dioxide to prepare methanol, the catalyst is subjected to hydrogenation reduction.

8. the purposes of the catalyst as claimed in claim 7, is characterized in that, also comprises at least one in following technical characteristic:

1) The temperature of hydrogenation reduction is 300～400℃;

2) The time of hydrogenation reduction is 6～16h;

3) The pressure of hydrogenation reduction is 0.01～0.5MPa;

4) The hydrogen space velocity of hydrogenation reduction is 2500～3500ml/g/h.

9 . A method for preparing methanol by CO ₂ hydrogenation, characterized in that, CO ₂ and H ₂ are reacted in the presence of the catalyst according to claim 1 to obtain methanol.

10. The method for preparing methanol by _CO hydrogenation as claimed in claim 9, further comprising at least one of the following technical features:

1) The volume ratio of CO ₂ to H ₂ is 1:2 to 1:7;

2) the reaction temperature is 300～400 ℃;

3) The reaction pressure is 2～7Mpa;

4) The reaction space velocity is 5000～24000ml/g/h.