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

Abstract

The invention relates to the technical field of catalysts, and discloses a catalyst for preparing methanol through carbon dioxide hydrogenation as well as a preparation method and application thereof. The catalyst comprises a carrier and an active component loaded on the carrier, the carrier is C (at) CuxMo2C, x is equal to 0.01-1, and the active component is selected from one or more of Cu, Zn, Al, Zr, In, Ce and Ga. The catalyst provided by the invention does not use noble metal, is low in price and simple in preparation method, can modulate carrier components and loaded metal, and is easy for batch production. The catalyst can be used for preparing methanol through carbon dioxide hydrogenation, and the conversion rate of carbon dioxide and the selectivity of methanol can be improved.

Description

Technical Field

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

[0002] Methanol is a basic organic chemical raw material with a wide range of uses. Methanol has a simple molecular structure, and the process of preparing methanol using CO2 is relatively easy to implement. By preparing methanol from CO2, we can rely on the existing C1 chemical system to achieve green manufacturing of chemical products. Therefore, methanol is expected to become an important direction for the resource utilization of CO2. CO2 is a non-polar linear molecule, and CO is a linear polar molecule. CO2 is more stable and more difficult to activate in terms of kinetics and thermodynamics. In the process of CO2 hydrogenation, a higher temperature is required to activate the CO2 molecule, and the CO2 hydrogenation reaction is an exothermic reaction. Increasing the temperature is not conducive to the reaction. Therefore, it is crucial to rationally design the catalyst to prepare a CO2 hydrogenation catalyst with high catalytic activity to produce methanol.

[0003] Copper-based catalysts have the advantages of low price, high activity, good low-temperature performance, few side reactions, good methanol selectivity, and high purity of crude methanol. They are widely used in industrial methanol synthesis. Among them, Cu / ZnO2 / Al2O3 catalytic synthesis gas hydrogenation is currently the main method for industrial methanol synthesis. This method usually uses synthesis gas (CO and H2 as the main components) as raw materials, with a reaction pressure of 50-100 bar and a temperature of 200-300℃.

[0004] CN109794276A discloses a Cu-C3N4-M-ZnO carbon dioxide hydrogenation to methanol catalyst, but the CO2 conversion rate is low (<6%).

[0005] CN103272607A discloses a copper-based catalyst for synthesizing methanol by hydrogenation of CO2. The catalyst is prepared by a parallel flow coprecipitation method using a high molecular polymer as a stabilizer. The catalyst is heated to 250°C, 5.0 MPa, a H2 / CO2 volume ratio of 3 / 1, and a GHSV of 4000 h -1 Under the reaction conditions, the catalyst has good stability, but the CO2 conversion rate and methanol selectivity are low. Summary of the invention

[0006] The purpose of the present invention is to overcome the problems of low carbon dioxide conversion rate and poor methanol selectivity in the prior art of carbon dioxide hydrogenation to methanol, and to provide a carbon dioxide hydrogenation to methanol catalyst and a preparation method and application thereof. The catalyst can be used for carbon dioxide hydrogenation to methanol and can improve the carbon dioxide conversion rate and methanol selectivity.

[0007] In order to achieve the above object, the present invention provides a catalyst for producing methanol by hydrogenation of carbon dioxide in the first aspect, the catalyst comprising a carrier and an active component supported on the carrier, wherein the carrier is C@Cu x Mo2C, x=0.01-1, the active component is selected from one or more of Cu, Zn, Al, Zr, In, Ce and Ga.

[0008] A second aspect of the present invention provides a method for preparing a catalyst for producing methanol by hydrogenating carbon dioxide, the method comprising the following steps:

[0009] The activated carbon is dispersed in a solution containing a Cu source and a Mo source, stirred, and freeze-dried to obtain a precursor; the precursor is kept at 600-800°C for 1-5 hours under a hydrogen atmosphere, and the carrier C@Cu is obtained after cooling. x Mo2C, where x = 0.01-1;

[0010] The carrier is passivated, and then the passivated carrier is dispersed in a metal salt solution, and a precipitant is added for precipitation to obtain a precipitate; the precipitate is calcined and reduced to obtain a catalyst.

[0011] The third aspect of the present invention provides a method for producing methanol by hydrogenating carbon dioxide, the method comprising: reacting carbon dioxide with hydrogen in the presence of a catalyst as described in any one of the first aspect or a catalyst prepared by the preparation method as described in any one of the second aspect.

[0012] Through the above technical solution, the beneficial technical effects achieved by the present invention are as follows:

[0013] 1) The catalyst of the present invention does not use precious metals, is inexpensive, and has a simple preparation method. Both the carrier component and the loaded metal can be adjusted, and it is easy to mass produce.

[0014] 2) The catalyst of the present invention can be used for producing methanol by hydrogenating carbon dioxide, and has the characteristics of high methanol selectivity, high CO2 conversion rate, excellent recycling performance, etc. In the temperature range of 180-270°C, the methanol selectivity is above 90%, and the single-pass conversion rate of carbon dioxide is above 17%. When the catalyst contains two active components, the single-pass conversion rate of carbon dioxide is above 19%. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a TEM image of the catalyst C1 sample prepared in Example 1;

[0016] Figure 2 This is the TEM-mapping element distribution map of the catalyst C1 sample prepared in Example 1. DETAILED DESCRIPTION

[0017] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0018] The first aspect of the present invention provides a catalyst for producing methanol by hydrogenation of carbon dioxide, the catalyst comprising a carrier and an active component supported on the carrier, wherein the carrier is C@Cu x Mo2C, x=0.01-1, the active component is selected from one or more of Cu, Zn, Al, Zr, In, Ce and Ga.

[0019] The inventors of the present invention have found through extensive research that in the CO2 hydrogenation to methanol reaction, under the formic acid mechanism, water on the surface of the copper-based catalyst can inhibit the further hydrogenation or decomposition process of HCOO to methanol, reducing the methanol selectivity and yield in the product. Therefore, it is considered to add the Mo element to the catalyst to improve the methanol selectivity, but since MO and C are not tightly combined, adding Cu as an intermediate can also improve the dispersion of the active component Cu, thereby improving the carbon dioxide conversion rate and methanol selectivity. The Cu-modified Mo2C coating is modified on the activated carbon carrier to form a composite material C@Cu x Mo2C. The Mo2C coating has good interface bonding with both Cu and C, forming a interconnected network structure.

[0020] The catalyst of the present invention is C@Cu x Mo2C is used as a carrier and one or more metals among Cu, Zn, Al, Zr, In, Ce and Ga as active components. When used for carbon dioxide hydrogenation to produce methanol, good methanol selectivity and CO2 conversion rate can be achieved.

[0021] In some embodiments of the present invention, the content of Mo is 0.5-20 wt %, preferably 0.7-5 wt %, based on the total weight of the carrier.

[0022] In the present invention, during the CO2 hydrogenation process, since the CO2 molecular structure is relatively stable and requires higher energy to open the C=O bond, and the CO bond has a strong polarity and is easy to break to participate in the reaction, appropriately increasing the CO content is conducive to the hydrogenation reaction. The introduction of molybdenum carbide can accelerate the conversion of carbon dioxide to carbon monoxide, and then the surface active components of the carrier can simultaneously catalyze the hydrogenation of CO2 and CO to produce methanol, which can improve the carbon dioxide conversion efficiency. Compared with single CO2 hydrogenation, the introduction of Mo2C will increase the methanol yield and CO2 conversion rate, but too high Mo2C will lead to excessive CO and reduced product selectivity.

[0023] In some embodiments of the present invention, based on the total weight of the catalyst, the content of the carrier is 50-96.5 wt %, and the content of the active component is 3.5-50 wt %.

[0024] In some preferred embodiments of the present invention, based on the total weight of the catalyst, the content of the carrier is 60-95 wt%, and the content of the active component is 5-40 wt%.

[0025] In some embodiments of the present invention, the carrier C@Cu x The specific surface area of ​​Mo2C is 100-1500m 2 / g, preferably 500-1000m 2 / g, the mass content of Mo does not exceed 10wt%, for example 9wt%, 8wt%, 7wt%, 6wt%, 5wt%, 4wt%, 3wt%, 2wt%, 1wt% and any value in the range consisting of any two values, preferably 6-9wt%.

[0026] A second aspect of the present invention provides a method for preparing a catalyst for producing methanol by hydrogenating carbon dioxide, the method comprising the following steps:

[0027] The activated carbon is dispersed in a solution containing a Cu source and a Mo source, stirred, and freeze-dried to obtain a precursor; the precursor is kept at 600-800°C for 1-5 hours under a hydrogen atmosphere, and the carrier C@Cu is obtained after cooling. x Mo2C, where x = 0.01-1;

[0028] The carrier is passivated, and then the passivated carrier is dispersed in a metal salt solution, and a precipitant is added for precipitation to obtain a precipitate; the precipitate is calcined and reduced to obtain a catalyst.

[0029] The catalyst of the present invention is used for preparing methanol by hydrogenating carbon dioxide, and has the characteristics of high methanol selectivity, high CO2 conversion rate, excellent recycling performance, etc. In the temperature range of 180-270°C, the methanol selectivity is above 90%, and the single-pass conversion rate of carbon dioxide is above 17%. When the catalyst contains two active components, the single-pass conversion rate of carbon dioxide is above 19%.

[0030] In some embodiments of the present invention, the average particle size of the activated carbon is 500nm-10μm, and the specific surface area is 200-1800m 2 / g, pore volume is 0.2-0.7cm 3 / g.

[0031] In some embodiments of the present invention, the activated carbon is selected from one or more of wood activated carbon, fruit shell activated carbon, coal-based activated carbon, regenerated carbon and petroleum-based activated carbon.

[0032] In some embodiments of the present invention, the activated carbon has a morphology of one or more of fiber, sphere and flake.

[0033] In some embodiments of the present invention, the Cu source is selected from one or more of copper nitrate, copper sulfate, copper chloride and copper oxide.

[0034] In some embodiments of the present invention, the Mo source is selected from ammonium heptamolybdate ((NH4)6Mo7O 24 ), one or more of molybdenum chloride and sodium molybdate.

[0035] In some embodiments of the present invention, the molar ratio of the Cu source, the Mo source and the activated carbon is 0.2-2.5:0.1-1.2:6.5-9.7, preferably 1-2:0.5-1:6-9.

[0036] In some embodiments of the present invention, the metal salt solution is selected from soluble salts of at least one metal selected from Cu, Zn, Al, Zr, In, Ce and Ga.

[0037] In the present invention, the soluble salt is preferably nitrate.

[0038] In the present invention, the soluble salt used is preferably a nitrate corresponding to a metal such as Cu, Zn, Al, Zr, In, Ce, or Ga.

[0039] In some embodiments of the present invention, the mass ratio of the carrier to the metal salt in the metal salt solution is 0.5-5:1.

[0040] In some embodiments of the present invention, the concentration of the metal salt in the metal salt solution is 0.01-2 mol / L.

[0041] In some embodiments of the present invention, the precipitating agent is one or more of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide and potassium hydroxide.

[0042] In some embodiments of the present invention, the concentration of the precipitant is 0.05-0.5 mol / L, and the pH of the precipitate is 6.5-7.5.

[0043] In some embodiments of the present invention, the temperature of the passivation treatment is 20-30° C. and the time is 1-3 hours.

[0044] In some embodiments of the present invention, the passivation treatment gas is a mixture of oxygen and an inert gas, wherein the volume content of oxygen in the mixed gas is 0.05-1%, for example, 1% O2 / N2.

[0045] In the present invention, the inert gas is selected from one or more of nitrogen, argon and helium.

[0046] In some embodiments of the present invention, the calcination is performed under a nitrogen atmosphere, the calcination temperature is 300-500° C., and the calcination time is 0.33-0.66 h.

[0047] In some embodiments of the present invention, the reduction is carried out under H2 atmosphere, the reduction temperature is 200-250°C, and the time is 2-5h.

[0048] The third aspect of the present invention provides a method for producing methanol by hydrogenating carbon dioxide, the method comprising: reacting carbon dioxide with hydrogen in the presence of a catalyst as described in any one of the first aspect or a catalyst prepared by the preparation method as described in any one of the second aspect.

[0049] In the present invention, during the CO2 hydrogenation process, since the CO2 molecular structure is relatively stable and requires a high energy to open the C=O bond, and the CO bond has a strong polarity and is easy to break to participate in the reaction, appropriately increasing the CO content is conducive to the hydrogenation reaction. The introduction of molybdenum carbide can accelerate the conversion of CO2 to CO, and then the surface active components of the carrier can simultaneously catalyze the hydrogenation of CO2 and CO to produce methanol, which can improve the carbon dioxide conversion efficiency. The catalyst can promote the conversion of part of CO2 into CO and methanol, and then CO and CO2 are further hydrogenated on the metal active components to produce methanol, so as to improve the carbon dioxide conversion rate and methanol selectivity.

[0050] In some embodiments of the present invention, the volume ratio of carbon dioxide to hydrogen is 1:1-1:10, and the space velocity is 2000-20000h -1 .

[0051] In some embodiments of the present invention, the reaction temperature is 180-280° C. and the pressure is 3-8 MPa.

[0052] The effects and effects of the method of the present invention are specifically described below in conjunction with embodiments, but the following embodiments do not constitute a limitation to the scheme of the present invention.

[0053] In the following examples and comparative examples, if no specific conditions are specified, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, if no manufacturer is specified, are all conventional products that can be obtained through commercial channels.

[0054] C@Cu x The component content of the Mo2C carrier was detected by using an ICS-900 inductively coupled plasma emission spectrometer from DIONEX.

[0055] Example 1

[0056] Weigh 10g of activated carbon and disperse it in 200ml of Cu(NO3)2 (0.0184g) and (NH4)6Mo7O 24 (1.732 g) of the solution, stirred thoroughly for 3 h, and then freeze-dried to obtain the precursor; the precursor was placed in a tube furnace, kept at 700 ° C for 3 hours under a hydrogen atmosphere, and cooled to obtain C@Cu 0.081 Mo2C support, among which C@Cu 0.081 The component content of Mo2C carrier was detected by ICS-900 inductively coupled plasma emission spectrometer of DIONEX Company;

[0057] The obtained C@Cu 0.081 The Mo2C carrier was placed in 1% O2 / N2 and passivated at 30°C for 2h;

[0058] Weigh 5 g of the passivated carrier and fully disperse it in 200 ml of Cu(NO3)2 (0.75 g), Al(NO3)39H2O (0.52 g) and Zn(NO3)2 6H2O (0.68 g) solution, stir it for 3 hours, then slowly add sodium carbonate (0.1 mol / L) until the solution pH = 7; after centrifugation, washing and drying, place it in a tubular furnace and calcine it at 300°C for 0.60 hour under nitrogen atmosphere to obtain catalyst C1.

[0059] 0.2 g of catalyst C1 (20-40 mesh) was weighed and loaded into a reaction tube with an inner diameter of 8 mm, and reduced at 200°C for 5 h in pure H2 at normal pressure with a flow rate of 30 mL / min. Then, the raw gas n(H2):n(CO2)=3:1 was switched, and the reaction was carried out at 5 MPa and 250°C. The catalyst evaluation results are shown in Table 1.

[0060] like Figure 1 The TEM image of the catalyst C1 sample is shown. Figure 2 The TEM-mapping element distribution diagram of catalyst C1 sample is shown. Figure 1 and Figure 2 It can be seen that the catalyst C1 sample contains the elements O, Al, Mo, Cu and Zn, and the Cu, Zn and Al elements are distributed on the matrix composed of Mo / Cu.

[0061] Example 2

[0062] Weigh 10g of activated carbon and fully disperse it in 200ml of Cu(NO3)2 (0.368g) and (NH4)6Mo7O 24 (1.732 g) of the solution, stirred thoroughly for 3 hours, and then freeze-dried to obtain the precursor; the precursor was placed in a tube furnace, kept at 750 ° C for 2 hours under a hydrogen atmosphere, and cooled to obtain C@Cu 0.34 Mo2C carrier;

[0063] The obtained C@Cu 0.34 The Mo2C carrier was passivated in 1% O2 / N2 at 20°C for 3 h;

[0064] Weigh 5 g of the passivated carrier and fully disperse it in 200 ml of Cu(NO3)2 (0.62 g), In(NO3)36H2O (0.88 g) and Ga(NO3)36H2O (1.14 g) solution, stir it for 3 hours, and then slowly add sodium bicarbonate (0.1 mol / L) until the solution pH = 7; after centrifugation, washing and drying, place it in a tubular furnace and calcine it at 500°C for 0.33 hours under a nitrogen atmosphere to obtain catalyst C2.

[0065] 0.2 g of catalyst C2 (20-40 mesh) was weighed and loaded into a reaction tube with an inner diameter of 8 mm, and reduced at 250°C for 2 h in pure H2 at normal pressure with a flow rate of 30 mL / min, and then the raw gas n(H2):n(CO2)=10:1 was switched, and the reaction was carried out at 3 MPa and 210°C. The catalyst evaluation results are shown in Table 1.

[0066] Example 3

[0067] Weigh 10g of activated carbon and fully disperse it in 200ml of Cu(NO3)2 (0.092g) and (NH4)6Mo7O 24 (0.866 g) solution, stirred for 3 hours, and then freeze-dried to obtain a precursor; the precursor was placed in a tube furnace, kept at 600 ° C for 5 hours under a hydrogen atmosphere, and cooled to obtain C@Cu 0.12 Mo2C carrier;

[0068] The obtained C@Cu 0.12 The Mo2C carrier was placed in 1% O2 / N2 and passivated at 30°C for 1 h;

[0069] Weigh 5 g of the passivated carrier and fully disperse it in 200 ml of Cu(NO3)2 (0.21 g), Zr(NO3)4 (0.13 g) and In(NO3)3 (0.16 g) solution, stir it for 3 hours, and then slowly add potassium carbonate (0.1 mol / L) until the solution pH = 7; after centrifugation, washing and drying, place it in a tubular furnace and calcine it at 400°C for 0.50 hour under a nitrogen atmosphere to obtain catalyst C3.

[0070] 0.2 g of catalyst C3 (20-40 mesh) was weighed and loaded into a reaction tube with an inner diameter of 8 mm, and reduced at 220°C for 4 h in pure H2 at normal pressure with a flow rate of 20 mL / min, and then the raw gas n(H2):n(CO2)=1:1 was switched, and the reaction was carried out at 8 MPa and 180°C. The catalyst evaluation results are shown in Table 1.

[0071] Example 4

[0072] Weigh 10g of activated carbon and fully disperse it in 200ml of Cu(NO3)2 (0.276g) and (NH4)6Mo7O 24 (0.866 g) of the solution, stirred for 3 hours, and then freeze-dried to obtain the precursor; the precursor was placed in a tube furnace, kept at 800 ° C for 1 hour under a hydrogen atmosphere, and cooled to obtain C@Cu 0.51 Mo2C carrier;

[0073] The obtained C@Cu 0.51 The Mo2C carrier was passivated in 1% O2 / N2 at 30°C for 2h;

[0074] Weigh 5 g of the passivated carrier and fully disperse it in 200 ml of In(NO3)3 (1.12 g) and Ce(NO3)4 (0.93 g) solution, stir it for 3 hours, and then slowly add potassium bicarbonate (0.1 mol / L) until the solution pH = 7; after centrifugation, washing and drying, place it in a tubular furnace and calcine it at 350°C for 0.40 hour under nitrogen atmosphere to obtain catalyst C4.

[0075] 0.2 g of catalyst C4 (20-40 mesh) was weighed and loaded into a reaction tube with an inner diameter of 8 mm, and reduced at 230°C for 3 h in pure H2 at normal pressure with a flow rate of 30 mL / min, and then the raw gas n(H2):n(CO2)=6:1 was switched, and the reaction was carried out at 6 MPa and 240°C. The catalyst evaluation results are shown in Table 1.

[0076] Example 5

[0077] Weigh 10g of activated carbon and fully disperse it in 200ml of Cu(NO3)2 (0.46g) and (NH4)6Mo7O 24 (0.866 g) solution, stirred for 3 hours, and then freeze-dried to obtain a precursor; the precursor was placed in a tube furnace, kept at 700 ° C for 4 hours under a hydrogen atmosphere, and cooled to obtain C@Cu 0.9 Mo2C carrier;

[0078] The obtained C@Cu 0.9 The Mo2C carrier was passivated in 1% O2 / N2 at 25°C for 3 h;

[0079] 5 g of the passivated carrier was weighed and fully dispersed in 200 ml of Cu(NO3)2 (0.67 g) and Zr(NO3)4 (0.82 g) solution, stirred for 3 hours, and then sodium hydroxide (0.1 mol / L) was slowly added dropwise until the solution pH = 7. After centrifugation, washing, and drying, it was placed in a tube furnace and calcined at 300°C for 0.66 hours under a nitrogen atmosphere to obtain catalyst C5.

[0080] 0.2 g of catalyst C5 (20-40 mesh) was weighed and loaded into a reaction tube with an inner diameter of 8 mm, and reduced at 240°C for 2 h in pure H2 at normal pressure with a flow rate of 30 mL / min, and then the raw gas n(H2):n(CO2)=8:1 was switched, and the reaction was carried out at 5 MPa and 270°C. The catalyst evaluation results are shown in Table 1.

[0081] Example 6

[0082] Weigh 10g of activated carbon and fully disperse it in 200ml of Cu(NO3)2 (0.0092g) and (NH4)6Mo7O 24 (0.866 g) solution, stirred for 3 hours, and then freeze-dried to obtain a precursor; the precursor was placed in a tube furnace, kept at 600 ° C for 5 hours under a hydrogen atmosphere, and cooled to obtain C@Cu 0.015 Mo2C carrier;

[0083] The obtained C@Cu 0.015 The Mo2C carrier was placed in 1% O2 / N2 and passivated at 30°C for 1 h;

[0084] Weigh 5 g of the passivated carrier and fully disperse it in 200 ml of Zr(NO3)4 (0.5 g) solution, stir it for 3 hours, and then slowly add potassium carbonate (0.1 mol / L) until the solution pH = 7; after centrifugation, washing and drying, place it in a tubular furnace and calcine it at 400°C for 0.50 hour under a nitrogen atmosphere to obtain catalyst C6.

[0085] 0.2 g of catalyst C6 (20-40 mesh) was weighed and loaded into a reaction tube with an inner diameter of 8 mm, and reduced at 220°C for 4 h in pure H2 at normal pressure with a flow rate of 20 mL / min, and then the raw gas n(H2):n(CO2)=1:1 was switched, and the reaction was carried out at 8 MPa and 180°C. The catalyst evaluation results are shown in Table 1.

[0086] Comparative Example 1

[0087] Weigh 10g of activated carbon and fully disperse it in 200ml of Cu(NO3)2 (0.0092g) and (NH4)6Mo7O 24 (0.866 g) solution, stirred thoroughly for 3 h, and then freeze-dried to obtain a precursor; the precursor was placed in a tube furnace, kept at 600 ° C for 5 h under a hydrogen atmosphere, and cooled to obtain C@Cu 0.014 Mo2C carrier;

[0088] The obtained C@Cu 0.014 The Mo2C carrier was placed in 1% O2 / N2 and passivated at 30°C for 1 h to obtain catalyst D1.

[0089] 0.2 g of catalyst D1 (20-40 mesh) was weighed and loaded into a reaction tube with an inner diameter of 8 mm, and reduced at 220°C for 4 h in pure H2 at normal pressure with a flow rate of 20 mL / min, and then the raw gas n(H2):n(CO2)=1:1 was switched, and the reaction was carried out at 8 MPa and 180°C. The catalyst evaluation results are shown in Table 1.

[0090] Comparative Example 2

[0091] Weigh 0.21g of Cu(NO3)2, 0.13g of Zr(NO3)4 and 0.16g of In(NO3)3, fully disperse them in 200ml of solution, stir them thoroughly for 3 hours, then slowly add potassium carbonate (0.1mol / L) until the solution pH = 7; after centrifugation, washing and drying, place in a tubular furnace and calcine at 400℃ for 0.50 hour under nitrogen atmosphere to obtain catalyst D2.

[0092] 0.2 g of catalyst D2 (20-40 mesh) was weighed and loaded into a reaction tube with an inner diameter of 8 mm, and reduced at 220°C for 4 h in pure H2 at normal pressure with a flow rate of 20 mL / min, and then the raw gas n(H2):n(CO2)=1:1 was switched, and the reaction was carried out at 8 MPa and 180°C. The catalyst evaluation results are shown in Table 1.

[0093] Comparative Example 3

[0094] Weigh 5 g of alumina carrier and fully disperse it in 200 ml of Cu(NO3)2 (0.21 g), Zr(NO3)4 (0.13 g) and In(NO3)3 (0.16 g) solution, stir it thoroughly for 3 hours, and then slowly add potassium carbonate (0.1 mol / L) until the solution pH = 7; after centrifugation, washing and drying, place it in a tubular furnace and calcine it at 400°C for 0.50 hour under a nitrogen atmosphere to obtain catalyst D3.

[0095] 0.2 g of catalyst D3 (20-40 mesh) was weighed and loaded into a reaction tube with an inner diameter of 8 mm, and reduced at 220°C for 4 h in pure H2 at normal pressure with a flow rate of 20 mL / min, and then the raw gas n(H2):n(CO2)=1:1 was switched, and the reaction was carried out at 8 MPa and 180°C. The catalyst evaluation results are shown in Table 1.

[0096] Table 1 Catalyst evaluation results

[0097]

[0098] From the results in Table 1, it can be seen that the catalysts prepared by using Examples 1-6 of the present invention for hydrogenation of carbon dioxide to methanol have high methanol selectivity of more than 90%, even reaching 97.56; high CO2 conversion rate, the single-pass conversion rate of carbon dioxide is more than 17%, and the catalysts prepared by Examples 1-5 contain two active components, and the single-pass conversion rate of carbon dioxide is more than 19%. Compared with the catalysts prepared by Comparative Examples 1-3, the catalysts prepared by the examples of the present invention have significantly better catalytic effects.

[0099] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A catalyst for preparing methanol by hydrogenating carbon dioxide, characterized in that: The catalyst comprises a carrier and an active component supported on the carrier, wherein the carrier is C@Cu x Mo2C, x=0.01-1, the active component is selected from one or more of Cu, Zn, Al, Zr, In, Ce and Ga.

2. The catalyst according to claim 1, wherein Based on the total weight of the carrier, the content of Mo is 0.5-20wt%, preferably 0.7-5wt%.

3. The catalyst according to claim 1 or 2, wherein Based on the total weight of the catalyst, the content of the carrier is 50-96.5wt%, and the content of the active component is 3.5-50wt%; Preferably, based on the total weight of the catalyst, the content of the carrier is 60-95wt%, and the content of the active component is 5-40wt%.

4. The catalyst according to any one of claims 1 to 3, wherein The carrier C@Cu x The specific surface area of ​​Mo2C is 100-1500m 2 / g, preferably 500-1000m 2 / g, and the mass content of Mo does not exceed 10wt%.

5. A method for preparing a catalyst for producing methanol by hydrogenating carbon dioxide, characterized in that: The preparation method comprises the following steps: The activated carbon is dispersed in a solution containing a Cu source and a Mo source, stirred, and freeze-dried to obtain a precursor; the precursor is kept at 600-800°C for 1-5 hours under a hydrogen atmosphere, and the carrier C@Cu is obtained after cooling. x Mo2C, where x = 0.01-1; The carrier is passivated, and then the passivated carrier is dispersed in a metal salt solution, and a precipitant is added for precipitation to obtain a precipitate; the precipitate is calcined and reduced to obtain a catalyst.

6. The preparation method according to claim 5, wherein: The average particle size of the activated carbon is 500nm-10μm, and the specific surface area is 200-1800m 2 / g, pore volume is 0.2-0.7cm 3 / g; And / or, the activated carbon is selected from one or more of wood activated carbon, fruit shell activated carbon, coal-based activated carbon, regenerated carbon and petroleum-based activated carbon; And / or, the Cu source is selected from one or more of copper nitrate, copper sulfate, copper chloride and copper oxide; And / or, the Mo source is selected from one or more of ammonium heptamolybdate, molybdenum chloride and sodium molybdate; And / or, the molar ratio of the Cu source, the Mo source and the activated carbon is 0.2-2.5:0.1-1.2:6.5-9.7; And / or, the metal salt in the metal salt solution is a soluble salt of at least one metal selected from Cu, Zn, Al, Zr, In, Ce and Ga; preferably, the mass ratio of the carrier to the metal salt in the metal salt solution is 0.5-5:1; And / or, the precipitant is one or more of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide and potassium hydroxide. Preferably, the concentration of the precipitant is 0.05-0.5 mol / L, and the pH of the precipitation is 6.5-7.

5.

7. The preparation method according to claim 5 or 6, wherein: The temperature of the passivation treatment is 20-30°C and the time is 1-3h; And / or, the gas for the passivation treatment is a mixed gas of oxygen and inert gas, wherein the volume content of oxygen in the mixed gas is 0.05-1%.

8. The preparation method according to any one of claims 5 to 7, wherein: The calcination is carried out in a nitrogen atmosphere, the calcination temperature is 300-500° C., and the calcination time is 0.33-0.66 h; And / or, the reduction is carried out under H2 atmosphere, the reduction temperature is 200-250°C, and the time is 2-5h.

9. A method for preparing methanol by hydrogenating carbon dioxide, characterized in that: The method comprises: reacting carbon dioxide with hydrogen in the presence of the catalyst described in any one of claims 1 to 4 or the catalyst prepared by the preparation method described in any one of claims 5 to 8.

10. The method according to claim 9, wherein: The volume ratio of carbon dioxide to hydrogen is 1:1-1:10, and the space velocity is 2000-20000h -1 ; And / or, the reaction temperature is 180-280° C. and the pressure is 3-8 MPa.

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