阅读说明：本技术 一种在低压下直接制备碳酸二甲酯的方法 (Method for directly preparing dimethyl carbonate under low pressure ) 是由 刘春� 刘凯 于 2019-12-04 设计创作，主要内容包括：一种低压条件下由二氧化碳和甲醇直接合成碳酸二甲酯的方法,其属于化学合成领域。该方法采用二氧化碳和甲醇为原料,1,8-二氮杂二环十一碳-7-烯(DBU)、咪唑盐与二溴甲烷为活化剂,乙腈作为溶剂来制备碳酸二甲酯。在优化的反应条件下,碳酸二甲酯收率为82%。该方法反应条件温和,操作简便,收率高,是制备碳酸二甲酯的优良体系。(A method for directly synthesizing dimethyl carbonate from carbon dioxide and methanol under low pressure belongs to the field of chemical synthesis. The method adopts carbon dioxide and methanol as raw materials, 1, 8-diazabicycloundecen-7-ene (DBU), imidazolium salt and dibromomethane as activators, and acetonitrile as a solvent to prepare the dimethyl carbonate. Under the optimized reaction conditions, the yield of the dimethyl carbonate is 82%. The method has the advantages of mild reaction conditions, simple and convenient operation and high yield, and is an excellent system for preparing the dimethyl carbonate.)

1. A method for directly preparing dimethyl carbonate from carbon dioxide and methanol under the condition of low pressure is characterized in that: preparing dimethyl carbonate by using carbon dioxide and methanol as raw materials and using 1, 8-diazabicycloundecen-7-ene, dibromomethane and imidazole salt as activators; the structural formula of the 1, 8-diazabicycloundecen-7-ene and imidazole salt is shown as follows:

1, 8-diazabicycloundecen-7-ene:

imidazole salt:

the dosage of the 1, 8-diazabicycloundecen-7-ene is 0.5-2.5 equiv of the dosage of the methanol, the dosage of the imidazole salt is 1-1.5 equiv of the dosage of the methanol, and the dosage of the dibromomethane is 3-7 equiv of the dosage of the methanol.

2. The process of claim 1 for the direct production of dimethyl carbonate from carbon dioxide and methanol at low pressure, wherein: the method adopts acetonitrile or dibromomethane as a solvent, the initial pressure of carbon dioxide is 0.1-1.5 MPa, and the reaction temperature is 25-100 ℃.

3. The process of claim 1 for the direct production of dimethyl carbonate from carbon dioxide and methanol at low pressure, wherein: the method adopts acetonitrile as a solvent, the initial pressure of carbon dioxide is normal pressure, and the reaction temperature is 25-100 ℃.

4. A method for directly preparing dimethyl carbonate from carbon dioxide and methanol under the condition of low pressure is characterized in that: preparing dimethyl carbonate by using carbon dioxide and methanol as raw materials and 1, 8-diazabicycloundecene-7-ene and dibromomethane as activators; the dosage of the 1, 8-diazabicycloundecen-7-ene is 0.5-2.5 equiv of the dosage of the methanol, and the dosage of the dibromomethane is 3-7 equiv of the dosage of the methanol; the method adopts acetonitrile as a solvent, the initial pressure of carbon dioxide is normal pressure, and the reaction temperature is 25-100 ℃.

Technical Field

The invention relates to a method for directly preparing dimethyl carbonate from carbon dioxide and methanol under the condition of low pressure, belonging to the field of chemical synthesis.

Background

Dimethyl carbonate is an important Organic synthetic intermediate and has been widely used as a methylating agent, a carbonylating agent, a good solvent and a gasoline additive (Organic Letters, 2001, 3, 4279; Accounts of chemical research, 2002, 35, 706; Journal of Organic Chemistry, 2003, 68, 1954).

Direct synthesis of dimethyl carbonate from carbon dioxide and methanol is one of the effective methods for preparing dimethyl carbonate (Green Chemistry, 2002, 4, 230; Journal of CO)₂Utilization, 2013, 3, 98, Fuel, 2015, 166, 495, Chinese Journal of Chemistry, 2019, 40, 553). The method has the advantages of cheap raw materials and high atom utilization rate. However, the catalyst systems reported have disadvantages such as high reaction pressure and low yield (Fuel Processing Technology, 2013, 115, 233; Journal of CO)₂Utilization,2015, 12, 49; Journal of Catalysis, 2019, 371, 88）。

To bring the direct process to the level of industrial applicability, further developments are needed to obtain reaction systems with higher DMC yields at low pressures.

Disclosure of Invention

The invention aims to provide a novel chemical synthesis technology for directly preparing dimethyl carbonate from carbon dioxide and methanol under the action of an activating agent under the conditions of low pressure and mild conditions.

The present application develops a process for the direct preparation of dimethyl carbonate from carbon dioxide and methanol under mild conditions. The method has the advantages of mild reaction conditions, simple and convenient operation and high yield.

A method for directly preparing dimethyl carbonate adopts carbon dioxide and methanol as raw materials, 1, 8-diazabicycloundecen-7-ene (DBU), imidazole salt and dibromomethane as activators, and acetonitrile as a solvent to prepare the dimethyl carbonate. The structural formulas of DBU and imidazole salt are shown as follows:

1, 8-diazabicycloundecen-7-ene (DBU):

imidazole salt:

the initial pressure of the carbon dioxide used in the invention is 0.1-1.5 MPa, and the reaction temperature is 25-100 ℃.

The dosage of DBU used in the invention is 0.5-2.5 equiv of the dosage of methanol, the dosage of imidazole salt is 1-1.5 equiv of the dosage of methanol, and the dosage of dibromomethane is 3-7 equiv of the dosage of methanol.

A method for directly preparing dimethyl carbonate from carbon dioxide and methanol under low pressure condition adopts the carbon dioxide and the methanol as raw materials, and 1, 8-diazabicycloundecen-7-ene and dibromomethane as activators to prepare the dimethyl carbonate; the dosage of the 1, 8-diazabicycloundecen-7-ene is 0.5-2.5 equiv of the dosage of the methanol, and the dosage of the dibromomethane is 3-7 equiv of the dosage of the methanol; the method adopts acetonitrile as a solvent, the initial pressure of carbon dioxide is normal pressure, and the reaction temperature is 25-100 ℃.

System 1: reacting in an autoclave (initial pressure of 0.1-1.5 MPa) by taking acetonitrile as a solvent and 1-ethyl-3-methylimidazole hexafluorophosphate, dibromomethane and DBU as activators;

system 2: dibromomethane is used as a solvent, 1-ethyl-3-methylimidazole hexafluorophosphate and DBU are used as activators, and the reaction is carried out in a high-pressure kettle (the initial pressure is 0.1-1.5 MPa);

system 3: reacting in a common glass bottle by taking acetonitrile as a solvent and 1-ethyl-3-methylimidazole hexafluorophosphate, dibromomethane and DBU as activators, and hanging a carbon dioxide balloon;

system 4: acetonitrile is used as a solvent, 1-ethyl-3-methylimidazole hexafluorophosphate is not added, dibromomethane and DBU are used as activators, and the materials are reacted in a common glass bottle and hung with a carbon dioxide balloon.

The implementation process of the invention is as follows: imidazole salt (1.0 mmol), acetonitrile (0.3mL), dibromomethane (3.0mmol), DBU (1.5mmol), methanol (1.0 mmol) and biphenyl (10 mg, an internal standard substance) are added into a 25 mL high-pressure reaction kettle, then carbon dioxide is introduced for reaction, and the yield of the product dimethyl carbonate is obtained through quantitative analysis by a gas chromatography internal standard method after the reaction is finished.

The invention has the beneficial effects that:

the method can prepare the dimethyl carbonate with higher yield by taking carbon dioxide and methanol as raw materials under lower carbon dioxide pressure. From the comparison of the 4 groups of systems, the yield of the dimethyl carbonate is 25 percent in the system without adding 1-ethyl-3-methylimidazolium hexafluorophosphate; the system 1, the system 2 and the system 3 added with the 1-ethyl-3-methylimidazole hexafluorophosphate have the yield improved by more than 2 times compared with the system 1, and the effect of the 1-ethyl-3-methylimidazole hexafluorophosphate, dibromomethane and DBU which are matched as an activating agent is very obvious. A reaction system which takes acetonitrile as a solvent and 1-ethyl-3-methylimidazolium hexafluorophosphate, dibromomethane and DBU as activators and reacts under the pressure of 0.1-1.5 MPa is optimal, and the yield can reach 82%. The method has the advantages of cheap and easily-obtained raw materials, mild reaction conditions, simple and convenient operation and high yield.

Detailed Description