阅读说明：本技术 使用铜/氧化亚铜纳米片催化剂热催化甲醇与二氧化碳生成碳酸二甲酯的方法 (Method for preparing dimethyl carbonate by using copper/cuprous oxide nanosheet catalyst to thermally catalyze methanol and carbon dioxide ) 是由 张晓东 金森 谢毅 于 2020-05-09 设计创作，主要内容包括：本发明提供了一种使用铜/氧化亚铜纳米片催化剂热催化甲醇与二氧化碳生成碳酸二甲酯的方法,属于有机合成技术领域。本发明在较低温度与较低压力下,以有机物为溶剂,铜/氧化亚铜纳米片为催化剂,直接利用二氧化碳和甲醇一锅反应生成碳酸二甲酯。其原子利用率高,环境友好,反应步骤简单,成本低,可适用于大规模生产。(The invention provides a method for generating dimethyl carbonate by using a copper/cuprous oxide nanosheet catalyst to thermally catalyze methanol and carbon dioxide, and belongs to the technical field of organic synthesis. The invention directly utilizes carbon dioxide and methanol to react in one pot to generate dimethyl carbonate by taking organic matters as solvent and copper/cuprous oxide nanosheets as catalyst at lower temperature and lower pressure. The method has the advantages of high atom utilization rate, environmental friendliness, simple reaction steps and low cost, and is suitable for large-scale production.)

1. A method for generating dimethyl carbonate by using a copper/cuprous oxide heterojunction nanosheet catalyst through thermocatalysis comprises the following steps:

s1, adding a copper/cuprous oxide heterojunction nanosheet catalyst into an organic solvent, and violently stirring to obtain a mixed solution;

s2, adding methanol into the mixed solution obtained in the step S1, and introducing inert gas to obtain a reaction solution;

s3, transferring the reaction liquid obtained in the step S2 to a closed high-pressure kettle, and introducing pure carbon dioxide;

s4, keeping the carbon dioxide in the autoclave at the pressure of 0.1-10Mp under the condition of stirring, isolating air, heating to the reaction temperature for reaction,

s5, centrifuging and taking supernatant to obtain a product;

wherein the copper/cuprous oxide heterojunction nanosheet catalyst is prepared by the following steps:

(1) adding an organic solvent into an alcohol solvent, and uniformly stirring to obtain a mixed solution;

(2) adding copper acetylacetonate and a surfactant into the mixed solution obtained in the step (1), and violently stirring to obtain a reaction solution;

(3) transferring the reaction liquid in the step (2) into a polytetrafluoroethylene reaction kettle, sealing, and heating to 100-200 ℃ to obtain a product;

(4) and washing, drying and grinding the product to obtain the copper/cuprous oxide heterojunction nanosheet catalyst.

2. The method of claim 1, wherein in step S1, the organic solvent comprises cyclohexane, acetonitrile, n-hexane, benzene, and combinations thereof;

preferably, in step S1, the ratio of the copper/cuprous oxide heterojunction nanosheet catalyst to the organic solvent is from 0.002 to 0.1 g/mL;

preferably, in step S1, the stirring is selected from magnetic stirring and mechanical stirring; preferably, the stirring rate is 100-.

3. The method of claim 1, wherein in step S2, the inert gas comprises argon, nitrogen, and combinations thereof;

preferably, in step S2, the volume ratio of methanol to the mixed solution is 1:100 to 1: 10;

preferably, in step S2, the inert gas is introduced at 20-80 mL/min.

4. The method of claim 1, wherein in step S3, the ratio of the volume of the reaction solution to the volume of the reaction kettle is 1:1 to 1: 5;

preferably, in step S3, pure carbon dioxide is introduced at 50-150mL/min for 2-10 min.

5. The method according to claim 1, wherein in step S4, the temperature rise is a temperature programmed rise; preferably, the temperature is raised to a reaction temperature of 80-160 ℃; preferably, the speed of temperature programming is 5-10 ℃/min; preferably, the reaction time is 8 to 24 hours.

Preferably, in step S4, the stirring is selected from magnetic stirring and mechanical stirring; preferably, the stirring rate is 100-.

6. The method as claimed in claim 1, wherein in step S5, centrifugation is performed at a rotation speed of 10000-.

7. The method according to claim 1, wherein in step (1), the organic solvent is selected from the group consisting of N, N-dimethylformamide, N-methylpyrrolidone, a derivative thereof, or any combination thereof; or

Preferably, in step (1), the alcoholic solvent is selected from C_1-6An alcohol, preferably methanol, ethanol and derivatives thereof or any combination thereof; or

Preferably, in step (1), the volume ratio of the alcohol solvent to the organic solvent is 1:1-6: 1;

preferably, in step (1), stirring is performed by using a magnetic stirrer, and the rotating speed is 1000-4000r/min for 10 minutes to 1 hour.

8. The method according to claim 1, wherein in step (2), the surfactant is cetyl trimethyl ammonium bromide, dodecyl trimethyl ammonium bromide, polyvinyl pyrrolidone, sodium oleate, or any combination thereof;

preferably, in step (2), the molar ratio of copper acetylacetonate to surfactant is from 6:1 to 8: 1;

preferably, in step (2), stirring is performed by using a magnetic stirrer, and the rotating speed is 1000-4000r/min for 10 minutes to 1 hour.

9. The method of claim 1, wherein in step (3), the volume ratio of the reaction solution to the polytetrafluoroethylene reaction vessel is 1:2 to 1: 4;

preferably, in the step (3), the temperature rise is a temperature programmed to the reaction temperature; preferably, the heating rate is 5-10 ℃/min; preferably, the reaction time is 6 to 12 hours.

10. The method according to claim 1, wherein in the step (4), the washing is performed by washing with deionized water until the pH value of the supernatant is 7, and then washing with absolute ethyl alcohol twice;

preferably, in the step (4), the drying is a treatment at 60 to 80 ℃ for 8 to 24 hours.

Technical Field

The invention provides a method for generating dimethyl carbonate by using a copper/cuprous oxide nanosheet catalyst to thermally catalyze methanol and carbon dioxide, and belongs to the technical field of organic synthesis.

Background

As a major gas causing greenhouse effect, excessive carbon dioxide disturbs the balance of carbon cycle, water cycle and even the entire ecosystem of the earth environment. Thus, successful conversion of carbon dioxide to useful chemicals and fuels by fixed reactions using suitable catalysts can effectively reduce the deleterious effects on the ecosystem. Meanwhile, as a potential carbon resource for solving the problem of the shortage of energy and basic chemical raw materials, various organizations around the world, including national and international governments, establish some interesting cooperative projects for solving the problem of carbon dioxide. With technological advances, gaseous products such as carbon dioxide (CO), methane (CH4), ethylene (C2H2) or C1 liquids such as formic acid (HCOOH) have been well studied, and their obvious properties of low cost and unfavorable long-range mass transport have led to the idea of fixing carbon dioxide to more valuable long-carbon-chain high energy density products.

Dimethyl carbonate, as an important starting material and intermediate for organic synthesis, can be used as a carbonylation, methylation and carbonyl methylation reagent instead of toxic and harmful phosgene, dimethyl sulfate and methyl chloroformate due to the active functional groups such as carbonyl, methyl, methoxy and the like in the molecular structure. Because the dimethyl carbonate has the advantages of no toxicity, excellent environmental protection performance, wide application and the like, people have led to extensive research on the dimethyl carbonate. Compared with the traditional synthesis method, the direct synthesis of dimethyl carbonate by using the greenhouse gas carbon dioxide as a raw material and methanol through a catalytic reaction is more important for research.

Since the direct synthesis of dimethyl carbonate from carbon dioxide and methanol is positive in the range of 0.1MPa and 0-800 ℃, the direct synthesis is difficult to carry out thermodynamically, resulting in low conversion rate. The main reason for this is that the preparation of highly active catalysts has been the key to the reaction due to the high stability of carbon dioxide. At present, the catalysts used for synthesizing dimethyl carbonate by directly reacting carbon dioxide with methanol include alkoxy metal organic compounds, alkali metals, copper-based supported metal catalysts, transition metal oxides, and the like. Among them, the copper-based supported catalyst is limited in practical application due to severe reaction conditions, low conversion rate, and the like.

Disclosure of Invention

The invention aims to solve the problems of complex process, high energy consumption and the like of the existing copper-based catalyst applied to directly synthesizing dimethyl carbonate by using carbon dioxide and methanol. In order to achieve the purpose, the traditional copper-based catalyst is changed, cuprous oxide is introduced, activation energy is reduced in a heterojunction mode, the surface area of a sample is enlarged in a nanosheet mode, the temperature and pressure required by reaction are reduced, and the product conversion rate is improved.

Specifically, the invention provides a method for synthesizing dimethyl carbonate by thermal catalysis, which comprises the following steps:

s1, adding a copper/cuprous oxide heterojunction nanosheet catalyst into an organic solvent, and violently stirring to obtain a mixed solution;

s2, adding methanol into the mixed solution obtained in the step S1, and introducing inert gas to obtain a reaction solution;

s3, transferring the reaction liquid obtained in the step S2 to a closed high-pressure kettle, and introducing pure carbon dioxide;

s4, under the stirring condition, keeping the carbon dioxide in the autoclave at the pressure of 0.1-10Mp, isolating air, and heating to the reaction temperature for reaction;

s5, centrifuging and taking supernatant to obtain a product;

wherein the copper/cuprous oxide heterojunction nanosheet catalyst is prepared by the following steps:

(1) adding an organic solvent into an alcohol solvent, and uniformly stirring to obtain a mixed solution;

(2) adding copper acetylacetonate and a surfactant into the mixed solution obtained in the step (1), and violently stirring to obtain a reaction solution;

(3) transferring the reaction liquid in the step (2) into a polytetrafluoroethylene reaction kettle, sealing, and heating to 100-200 ℃ to obtain a product;

(4) and washing, drying and grinding the product to obtain the copper/cuprous oxide heterojunction nanosheet catalyst.

In some embodiments, in step S1, the organic solvent includes cyclohexane, acetonitrile, n-hexane, benzene, and combinations thereof.

In some embodiments, in step S1, the ratio of copper/cuprous oxide nanosheet catalyst to organic solvent is from 0.002 to 0.1 g/mL.

In some embodiments, in steps S1 and S4, the stirring may be selected from magnetic stirring and mechanical stirring; preferably, the stirring rate is 100-.

In some embodiments, in step S2, the inert gas includes argon, nitrogen, and combinations thereof.

In some embodiments, in step S2, the volume ratio of methanol to the mixed solution is from 1:100 to 1: 10.

In some embodiments, in step S2, an inert gas is introduced at 20-80 mL/min.

In some embodiments, in step S3, the ratio of the volume of the reaction solution to the volume of the reaction vessel is from 1:1 to 1: 5.

In some embodiments, pure carbon dioxide is passed in step S3 at 50-150mL/min for 2-10 min.

In some embodiments, in step S4, the temperature increase is a temperature programmed; preferably, the temperature is raised to a reaction temperature of 80-160 ℃; preferably, the speed of temperature programming is 5-10 ℃/min; preferably, the reaction time is 8 to 24 hours.

In some embodiments, in step S5, centrifugation is performed at 10000-.

In some embodiments, in step (1), the organic solvent is selected from N, N-dimethylformamide, N-methylpyrrolidone, derivatives thereof, or any combination thereof.

In some embodiments, in step (1), the alcoholic solvent is selected from C_1-6Alcohols, preferably methanol, ethanol and their derivatives or any combination thereof.

In some embodiments, in step (1), the volume ratio of alcoholic solvent to organic solvent is from 1:1 to 6: 1.

In some embodiments, in step (1), the stirring is performed using a magnetic stirrer at a rotation speed of 1000-4000r/min for a time period of 10 minutes to 1 hour.

In some embodiments, in step (2), the surfactant is cetyl trimethyl ammonium bromide, dodecyl trimethyl ammonium bromide, polyvinyl pyrrolidone, sodium oleate, or any combination thereof.

In some embodiments, in step (2), the molar ratio of copper acetylacetonate to surfactant is from 6:1 to 8: 1.

In some embodiments, in step (2), the stirring is performed using a magnetic stirrer at a rotation speed of 1000-4000r/min for a time period of 10 minutes to 1 hour.

In some embodiments, in step (3), the ratio of the volume of the reaction solution to the volume of the polytetrafluoroethylene reaction vessel is from 1:2 to 1: 4.

In some embodiments, in step (3), the warming is a temperature programmed to the reaction temperature; preferably, the heating rate is 5-10 ℃/min; preferably, the reaction time is 6 to 12 hours.

In some embodiments, in step (4), the washing is performed by washing with deionized water until the pH of the supernatant is 7, and then washing with absolute ethanol twice.

In some embodiments, in step (4), the drying is treatment at 60-80 ℃ for 8-24 hours.

The invention has the beneficial effects that: according to the invention, the copper/cuprous oxide nanosheet catalyst is used for directly synthesizing dimethyl carbonate from carbon dioxide and methanol, the reaction activity of the catalyst is enhanced in a heterojunction mode, and the contact area with a reactant is enhanced through the shape of the nanosheet, so that the practical application of the product is facilitated.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 shows a scanning electron microscopy analysis of the catalyst of example 1;

FIG. 2 shows a scanning electron microscopy analysis of the catalyst of example 2;

FIG. 3 shows a nuclear magnetic resonance carbon spectrum analysis of the product of example 3;

figure 4 shows a graph of nmr hydrogen spectroscopy analysis of the product of example 4.

Detailed Description

The following describes embodiments of the present invention in detail. The embodiments described by referring to the drawings are exemplary only for the purpose of illustrating the invention and are not to be construed as limiting the invention.