Catalyst for carbon dioxide hydrogenation to methanol, its preparation method and application

Abstract

The application discloses a catalyst for carbon dioxide hydrogenation to prepare methanol and a preparation method and application thereof, and belongs to the field of carbon dioxide hydrogenation to prepare methanol. The preparation method comprises the following steps: dissolving Zn salt, Zr salt and Al salt in water to prepare solution A; dissolving NaCO3 and NaOH in water to prepare an alkaline precipitant solution; dissolving Cu salt, Zn salt and an additive Y in water to prepare solution B; mixing the alkaline precipitant solution with solution A, and then aging to obtain slurry C; mixing solution B, slurry C and the alkaline precipitant solution to obtain slurry D; aging, separating, washing, drying and calcining slurry D to obtain Cu-based metal oxide; mixing the Cu-based metal oxide with a low-carbon alcohol to obtain slurry E; adding tetraethyl orthosilicate into slurry E, adding an ammonia water solution to stir, and then filtering, washing and drying to obtain amorphous silica-coated Cu-based metal oxide; mixing the amorphous silica-coated Cu-based metal oxide with liquid alkane under ultrasonic condition, then adding an organosilane agent, and continuing to ultrasonically treat, and then filtering, washing and drying to obtain the catalyst.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of carbon dioxide hydrogenation to methanol, and particularly relates to a catalyst for carbon dioxide hydrogenation to methanol and a preparation method and application thereof. BACKGROUND

[0002] Methanol, as a multifunctional organic chemical basic raw material, is applied in the fields of synthetic fibers, plastics, medicines, pesticides, dyes and synthetic biology, and is of great importance to modern industry. It not only serves the clean energy demand of direct methanol fuel cells and diesel engines, but also acts as a storage and transportation medium in the hydrogen energy economy. Recently, the technology of preparing green methanol from carbon dioxide (CO2) has attracted widespread attention, which not only helps to achieve carbon emission reduction, but also promotes the sustainable manufacturing of related chemical products, providing an innovative solution to environmental problems and energy transformation. Therefore, the technology of preparing green methanol from CO2 hydrogenation has great development potential and broad application prospects.

[0003] Precise construction of a catalyst is the technical core of CO2 hydrogenation to methanol. At present, CO2 hydrogenation synthesis methanol catalysts are divided into: high-temperature synthesis methanol catalysts represented by ZnZrO x , ZnCrO x and In2O3 solid solution; and low-temperature synthesis methanol catalysts represented by Cu-based catalysts and Pd-based catalysts. CO2 hydrogenation to methanol is a strong exothermic reversible reaction. From the perspective of thermodynamics, a lower reaction temperature is more conducive to the generation of methanol. Therefore, non-noble metal Cu-based low-temperature synthesis methanol catalysts are favored by researchers. Among them, Cu-Zn-Al series catalysts are widely studied due to their low cost and high methanol yield. However, the process of CO2 hydrogenation to methanol generates water, and the reverse water gas shift reaction also produces a large amount of water, which easily causes irreversible deactivation of the catalyst structure, loss of active components or sintering, and poor stability of the catalyst, greatly hindering the industrialization development. Therefore, the development of Cu-based low-temperature methanol with high stability and high activity has great significance for the industrialization of CO2 hydrogenation to methanol. SUMMARY

[0004] In view of the deficiencies of the prior art, the purpose of the present application is to provide a catalyst for carbon dioxide hydrogenation to methanol and a preparation method and application thereof, which solves the problems in the prior art.

[0005] The purpose of the present application can be achieved by the following technical solutions:

[0006] The preparation method of the catalyst for carbon dioxide hydrogenation to methanol comprises the following steps:

[0007] Zn salt, Zr salt and Al salt are dissolved in water to form solution A; NaCO3 and NaOH are dissolved in water to form alkaline precipitant solution; Cu salt, Zn salt and additive Y are dissolved in water to form solution B; the alkaline precipitant solution is mixed with solution A to form turbid liquid, and slurry C is obtained by aging; solution B, slurry C and the alkaline precipitant solution are mixed to obtain slurry D; Cu-based metal oxide is obtained by aging, separation, washing, drying and calcination of slurry D;

[0008] Cu-based metal oxide is mixed with low-carbon alcohol to obtain slurry E; tetraethyl orthosilicate is added to slurry E, and then ammonia solution is added after stirring; after filtration, washing and drying, amorphous silica-coated Cu-based metal oxide is obtained.

[0009] Amorphous silica-coated Cu-based metal oxide is mixed with liquid alkane under ultrasonic, then organosilane agent is added, and the mixture is continuously ultrasonicated; finally, the catalyst for carbon dioxide hydrogenation to methanol is obtained after filtration, washing and drying.

[0010] Further, the additive Y is at least one of Mg salt, Mn salt, Ni salt, La salt or Ce salt;

[0011] The Mg salt is at least one of magnesium acetate and magnesium nitrate; the Mn salt is at least one of manganese chloride and manganese nitrate; the Ni salt is at least one of nickel nitrate and nickel chloride; the La salt is lanthanum nitrate; and the Ce salt is cerium nitrate.

[0012] Further, the low-carbon alcohol is one of methanol, ethanol and isopropanol; the organosilane agent is at least one of trimethylchlorosilane, trimethoxymethylsilane and dimethyldichlorosilane; and the liquid alkane is one of n-hexane, cyclohexane and cyclopentane.

[0013] Further, the Zn salt is at least one of zinc acetate and zinc nitrate; the Cu salt is at least one of copper nitrate and copper sulfate; the Zr salt is at least one of zirconium oxychloride, zirconium nitrate and zirconium sulfate; and the Al salt is at least one of aluminum nitrate and aluminum sulfate.

[0014] Further, the molar ratio of Al salt, Zr salt and Zn salt in solution A is 1:(0.1-0.9):(0.1-0.9).

[0015] Further, the molar ratio of Cu salt, Zn salt and additive Y in solution B is (600-700):(200-300):(5-50).

[0016] Further, the molar ratio of amorphous silica-coated Cu-based metal oxide to organosilane agent is 1kg:(0.5-6)L.

[0017] The catalyst for carbon dioxide hydrogenation to methanol is prepared by the preparation method.

[0018] The application of the catalyst for carbon dioxide hydrogenation to methanol in the preparation of methanol by carbon dioxide hydrogenation.

[0019] Further, the step of preparing methanol by carbon dioxide hydrogenation is:

[0020] Step 1: the catalyst for carbon dioxide hydrogenation to methanol is loaded into a fixed bed reactor after being shaped and granulated, and is reduced in situ under normal pressure of hydrogen;

[0021] Step 2: then, CO2 and H2 mixed gas is introduced, and the reaction is carried out under pressure to prepare methanol.

[0022] The beneficial effects of the present application are:

[0023] 1. The catalyst provided by the present application is formed by wrapping high-dispersed Cu-based metal oxides with hydrophobic silicon dioxide, wherein the composition of the Cu-based metal oxides is controllable, the thickness of the silicon dioxide shell layer and the hydrophobicity degree are controllable. By optimizing the composition of the catalyst, the thickness of the silicon layer and the hydrophobicity thereof, the catalyst has high stability in the preparation of methanol by carbon dioxide hydrogenation, and has the industrial application value of producing methanol from carbon dioxide by one-step method.

[0024] 2. The catalyst provided by the present application introduces an additive, which can form a strong interaction interface with Cu / Zn, anchor the Cu active component in a high-dispersed manner, strengthen CO2 adsorption, and further improve the conversion rate and methanol selectivity of the catalytic reaction. The catalyst has wide application space in the production of methanol from carbon dioxide. DETAILED DESCRIPTION

[0025] The technical solutions of the present application will be described clearly and completely in combination with the embodiments in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0026] The catalyst for carbon dioxide hydrogenation to methanol is prepared by the preparation method.

[0027] The preparation process of the catalyst for carbon dioxide hydrogenation to methanol is described below through the following examples.

[0028] Example 1

[0029] The preparation process of the catalyst for carbon dioxide hydrogenation to methanol is as follows:

[0030] (1) Preparation of Cu-based metal oxide:

[0031] Zn salt (zinc nitrate), Zr salt (zirconium nitrate), and Al salt (aluminum nitrate) were sequentially dissolved in deionized water (molar ratio of Zn / Zr / Al was 1:0.5:0.5) to prepare solution A with a concentration of 1.2 mol / L. NaCO3 and NaOH were dissolved in deionized water at a mass ratio of 1:1 to prepare an alkaline precipitant solution with a concentration of 1.2 mol / L. Cu salt (copper nitrate), Zn salt (zinc nitrate), and Y magnesium salt (magnesium acetate) were sequentially dissolved in deionized water at a Cu / Zn / Y molar ratio of 700:200:5 to prepare solution B with a concentration of 1.0 mol / L.

[0032] 100 ml of deionized water was mixed with a certain amount of precipitant solution, and the pH was adjusted to 8.2. At room temperature, 50 ml of solution A was slowly added to the precipitant solution while stirring, and the pH value in the solution was maintained at 8.2-8.3 throughout the process. After the addition of solution A was completed, the stirring was continued for 2 h to form slurry C.

[0033] Subsequently, deionized water was added to slurry C to adjust the pH to 7.3, and 500 ml of metal solution B and precipitant solution were slowly added to slurry C while maintaining the pH at 7.2-7.3 to obtain slurry D. Then, the stirring of slurry D was continued, and the aging was carried out at a temperature of 80°C for 4 h. Finally, the precipitate was separated, washed several times with deionized water until the pH value was lower than 7.1, and the obtained solid was calcined at 150°C for 8 h and then at 450°C for 4 h to obtain Cu-based metal oxide.

[0034] (2) Preparation of the catalyst for carbon dioxide hydrogenation to methanol;

[0035] 1.0 g of the above Cu-based metal oxide was mixed with 300 ml of low-carbon alcohol (ethanol) and ultrasonicated for 30 min. Subsequently, 5 ml of tetraethyl orthosilicate was slowly added dropwise, and after stirring for 2 h, 5% ammonia water was added, and the stirring was continued for another 4 h. The precipitate was filtered and washed several times with low-carbon alcohol (ethanol), and finally the solid was placed in a vacuum drying oven and dried at 140°C for 15 h to obtain Cu-based metal oxide wrapped with amorphous silicon dioxide.

[0036] Example 1

[0037] Example 2

[0038] Example 2 differs from Example 1 only in that the molar ratio of the Al salt, the Zr salt and the Zn salt in solution A is 1 :0.9:0.1.

[0039] Example 3

[0040] Example 3 differs from Example 1 only in that the molar ratio of the Al salt, the Zr salt and the Zn salt in solution A is 1 :0.1 :0.9.

[0041] Example 4

[0042] Example 4 differs from Example 1 only in that the molar ratio of the Cu salt, the Zn salt and the Y promoter in solution B is 600:300:5.

[0043] Example 5

[0044] Example 5 differs from Example 1 only in that the molar ratio of the Cu salt, the Zn salt and the Y promoter in solution B is 700:200:50.

[0045] Example 6

[0046] Example 6 differs from Example 1 only in that the amount of tetraethyl orthosilicate added is 20 ml.

[0047] Example 7

[0048] Example 7 differs from Example 1 only in that the ratio of the amorphous silica-coated Cu-based metal oxide (Kg) to the organosilane agent (L) is 1 :0.5,

[0049] Example 8

[0050] Example 8 differs from Example 1 only in that the ratio of the amorphous silica-coated Cu-based metal oxide (Kg) to the organosilane agent (L) is 1 :6.

[0051] In some other embodiments, the Zn salt is at least one of zinc acetate and zinc nitrate; the Cu salt is at least one of copper nitrate and copper sulfate; the Zr salt is at least one of zirconium oxychloride, zirconium nitrate and zirconium sulfate; and the Al salt is at least one of aluminum nitrate and aluminum sulfate.

[0052] The auxiliary Y can be at least one of a Mg salt, a Mn salt, a Ni salt, a La salt or a Ce salt; wherein the Mg salt is at least one of magnesium acetate and magnesium nitrate; the Mn salt in the auxiliary is at least one of manganese chloride and manganese nitrate; the Ni salt in the auxiliary Y is at least one of nickel nitrate and nickel chloride; the La salt is lanthanum nitrate; and the Ce salt is cerium nitrate.

[0053] The low carbon alcohol is one of methanol, ethanol and isopropanol; the organosilane agent is at least one of trimethylchlorosilane, trimethoxymethylsilane and dimethyldichlorosilane; and the liquid alkane is one of n-hexane, cyclohexane and cyclopentane.

[0054] Comparative Example 1

[0055] The process for preparing the catalyst in Comparative Example 1 is different from that of Example 1 only in that the catalyst is a commercial methanol synthesis catalyst (Sichuan Shoutai).

[0056] Comparative Example 2

[0057] The process for preparing the catalyst in Comparative Example 2 is different from that of Example 1 only in that the catalyst is a commercial methanol synthesis catalyst (Liaoning Haitai).

[0058] Experimental verification

[0059] The catalysts prepared in Examples 1-8 and Comparative Examples 1-2 are applied to the preparation of methanol; the experimental process is as follows:

[0060] 1.0 g of the catalyst is weighed, shaped and granulated, and then loaded into a fixed bed reactor, reduced in situ under hydrogen at 280°C for 6 h, and then the pressure of the reactor is increased to 4.0 MPa, the reaction temperature is 240°C, and the raw gas gas hourly space velocity is 6000 h-1under the conditions of synthesis of methanol, and the raw gas used is a CO2 and H2 mixed gas, wherein the molar ratio of CO2 / H2 is 1:3. -1

[0061] After the reaction is stable, the tail gas obtained by the reaction is collected by a gas bag, and then analyzed by gas chromatography for its components, and the liquid components obtained by the reaction are collected by a cold trap connected to the fixed bed. The gas chromatography is used to quantitatively analyze by an external standard method, and the carbon balance before and after the reaction is maintained at more than 95%.

[0062] After 200 hours of reaction, the CO2 conversion rate and the methanol selectivity of Examples 1-8 and Comparative Examples 1-2 are compared, and the results are shown in Table 1 below:​

[0063] Table 1 Test results of examples and comparative examples

[0064] CO2 conversion (C mol %) Methanol selectivity (Cmol%) Example 1 32.1 69.4 Example 2 31.2 62.0 Example 3 24.5 66.7 Example 4 25.2 65.4 Example 5 32.5 59.5 Example 6 23.2 64.3 Example 7 27.4 61.4 Example 8 29.2 63.9 Comparative Example 1 28.4 55.1 Comparative Example 2 26.6 57.0

[0065] From the test results of Table 1, it can be seen that:

[0066] Examples 1-3 show that the proper Zr / Al ratio is conducive to improving the conversion of CO2 and the selectivity of methanol. Examples 1 and 4-5 show that the Cu component is the main active component for CO2 conversion, and reducing its content in the catalyst will lead to a decrease in CO2 conversion; increasing the content of the regulating additive Y in the catalyst can slightly improve the conversion of CO2, but will lead to excessive hydrogenation, resulting in an increase in the CH4 content in the product and a decrease in the selectivity of methanol. Examples 1 and 6 show that increasing the thickness of the Si layer will inhibit the adsorption of CO2 on the Cu active site, leading to a decrease in CO2 conversion, so the thickness of the Si layer of the catalyst should not be too high. Examples 1 and 7-8 show that a decrease or excessive increase in the hydrophobicity of the surface of the catalyst will lead to a decrease in the conversion of CO2 and the selectivity of methanol.

[0067] In general, proper Zr / Al ratio, Cu content, additive reference, Si shell thickness and hydrophilic / hydrophobic properties are conducive to the conversion of CO2 and the production of methanol. Among them, the CO2 conversion and the selectivity of methanol of Example 1 are both superior to the currently commercialized methanol synthesis catalyst (Comparative Examples 1-2), indicating that the catalyst provided by the present application is very advantageous in future industrialization applications.

[0068] In the description of the present specification, the description of the terms "one embodiment", "example", "specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0069] The basic principles, main features and advantages of the present application are shown and described above. It should be understood by those skilled in the art that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A method for producing a catalyst for the hydrogenation of carbon dioxide to methanol, characterized by, The method comprises the following steps: Zn salt, Zr salt and Al salt are dissolved in water to form solution A, wherein the molar ratio of Al salt, Zr salt and Zn salt is 1:0.5:0.5; NaCO3 and NaOH are dissolved in water to form an alkaline precipitant solution; Cu salt, Zn salt and additive Y are dissolved in water to form solution B, wherein the molar ratio of Cu salt, Zn salt and additive Y is 700:200:5, and the additive Y is Mg salt; the alkaline precipitant solution is mixed with solution A to form a turbid liquid, and slurry C is obtained after aging; Solution B, slurry C and the alkaline precipitant solution are mixed to obtain slurry D; Cu-based metal oxide is obtained after aging, separation, washing, drying and calcination of slurry D; Cu-based metal oxide is mixed with low-carbon alcohol to obtain slurry E; tetraethyl orthosilicate is added to slurry E, followed by stirring, then adding an ammonia solution, and continuing to stir; after filtration, washing and drying, amorphous silica-coated Cu-based metal oxide is obtained; Amorphous silica-coated Cu-based metal oxide is ultrasonically mixed with liquid alkane, followed by adding an organosilane agent, wherein the mass ratio of amorphous silica-coated Cu-based metal oxide to organosilane agent is 1 kg:2 L, and then continuing to ultrasonically treat; finally, after filtration, washing and drying, a catalyst for carbon dioxide hydrogenation to prepare methanol is obtained.

2. The method for preparing a catalyst for carbon dioxide hydrogenation to methanol according to claim 1, characterized by, The Mg salt is at least one of magnesium acetate and magnesium nitrate.

3. The method for preparing a catalyst for carbon dioxide hydrogenation to methanol according to claim 1, characterized by, The low-carbon alcohol is one of methanol, ethanol and isopropanol; the organosilane agent is at least one of trimethylchlorosilane, trimethoxymethylsilane and dimethyldichlorosilane; and the liquid alkane is one of n-hexane, cyclohexane and cyclopentane.

4. The method for preparing a catalyst for carbon dioxide hydrogenation to methanol according to claim 1, characterized by, The Zn salt is at least one of zinc acetate and zinc nitrate; the Cu salt is at least one of copper nitrate and copper sulfate; the Zr salt is at least one of zirconium oxychloride, zirconium nitrate and zirconium sulfate; and the Al salt is at least one of aluminum nitrate and aluminum sulfate.

5. Catalyst for the hydrogenation of carbon dioxide to methanol, characterized in that, The catalyst is prepared by the preparation method of any one of claims 2-4.

6. The catalyst for carbon dioxide hydrogenation to prepare methanol according to claim 5 is applied to the preparation of methanol by carbon dioxide hydrogenation.

7. Use according to claim 6, characterized in that, The steps of preparing methanol by carbon dioxide hydrogenation are as follows: Step 1: the catalyst for carbon dioxide hydrogenation to prepare methanol is shaped and granulated, and then loaded into a fixed-bed reactor for in-situ reduction under normal pressure of hydrogen; Step 2: CO2 and H2 mixed gas is introduced, and the reaction is carried out under pressure to prepare methanol.