CN1264698A

CN1264698A - Process for directly synthesizing dimethyl carbonate from CO2 and methanol in supercritical condition

Info

Publication number: CN1264698A
Application number: CN00111405A
Authority: CN
Inventors: 房鼎业; 曹发海; 刘殿华
Original assignee: East China University of Science and Technology; China Petrochemical Corp
Current assignee: East China University of Science and Technology; China Petrochemical Corp
Priority date: 2000-01-01
Filing date: 2000-01-01
Publication date: 2000-08-30

Abstract

A process for directly synthesizing dimethyl carbonate features that under the existance of catalyst which is the mixture of magnesium or potassium carbonate and iodomethane, the CO2 and methanol directly take part in synthetic reaction in the supercritical condition of CO2 to obtain dimethyl carbonat. Its advantage is simple and environment-friend catalysis process.

Description

Method for directly synthesizing dimethyl carbonate from carbon dioxide and methanol under supercritical condition

The invention belongs to the technical field of dimethyl carbonate production, relates to a method for producing dimethyl carbonate, and particularly relates to a method for directly synthesizing dimethyl carbonate by adopting carbon dioxide and methanol.

Dimethyl carbonate (DMC) is a green chemical product withHas wide application. Such as the [ ═ CO]contained in the molecule]Can replace poisonous phosgene as a carbonylation agent; containing [ -CH]in the molecule₃]Can replace poisonous dimethyl sulfate as methylating agent; containing [ CH]in the molecule₃O-]As methoxylating agents; can be mutually dissolved with a plurality of organic matters to be used as a solvent; has high blending value and octane value, and can be used as gasoline additive.

At present, dimethyl carbonate is mainly produced by a phosgene-methanol method, an ester exchange method and a methanol oxidative carbonylation method. The former raw material is extremely toxic and pollutes the environment; with ethylene oxide or propylene oxide, CO₂The ester exchange method which takes methanol as raw material has the defects of too long process flow, large investment and the like; with methanol, CO and O₂The liquid phase and gas phase oxidation and carbonylation method which is used as raw material also has the defects of easy inactivation of catalyst, large corrosion to a reactor, difficult separation of products and the like. Due to CO₂The caused greenhouse effect is more and more a threat to people, and the carbon source is used as a carbon source to synthesize organic chemicals to meet the public desire for environmental protection. Thus, with CO₂And the direct synthesis of DMC by using methanol as raw material is a route with more theoretical and practical significance. The reaction formula of the route is:

only 4 patents were studied for this route:

(1) in the chinese patent CN 1131660a of jiangqi et al, magnesium methoxide is used as a catalyst, and the reaction is carried out in two steps;

(2) japanese patent JP 7903,012 to Yamazaki N.et al uses organic compounds of Sn and Ti as catalysts, respectively;

(3) and Japanese patent JP 9533,715 filed by Fujiaro O. uses methyl iodide and alkaline inorganic salt as catalysts;

(4) german patent Ger. Offen.2,748,718 to Hans Josef et al, Bayer corporation uses NaI and TlOH as catalysts.

In the 4 patents mentioned above, the CO content of one of the reactants is low due to the low pressure of the reaction₂It is difficult to activate effectively and the activity of the reaction is low. Therefore, a new one is developed and researchedThe preparation method of the dimethyl carbonate is very significant.

The invention aims to provide a novel catalyst prepared from CO₂And methanol as raw material to directly synthesize dimethyl carbonate.

The idea of the invention is that:

CO₂is a substance which is difficult to be activated under the conventional conditions, and CO is used in the supercritical reaction which is currently researched₂Usually, the reaction is not directly carried out, but the supercritical atmosphere is realized as a supercritical fluid to improve the selectivity or the catalyst activity of the composite reaction. Extensive experiments have demonstrated that under extreme reaction conditions, such as supercritical conditions, CO₂The molecule is polarized, and the polarity is changed, so that the activity is embodied, and the synthesis of new organic compounds is possible. Thus, the present invention converts CO₂And the dimethyl carbonate is directly synthesized with methanol under the supercritical condition by taking metal magnesium or a precursor taking the metal magnesium as a catalyst and a mixture of potassium carbonate and methyl iodide as the catalyst.

The method is also realized by the following steps:

introducing CO₂Putting the mixture and methanol into a reactor, adding a catalyst, reacting for 4-14 hours at 30-190 ℃ and 4.5-9 MPa, wherein the mole fraction of dimethyl carbonate in a liquid phase mixture of the reactor can reach 0.01-2.01%, and the preferable pressure is 6.5MPa ∞8.0 MPa; after the reaction is completed, the desired dimethyl carbonate can be separated from the reaction product by conventional methods such as distillation, etc., while the remaining CO₂Can be recycled with methanol. The reaction formula is as follows:

；

when the catalyst is metal magnesium, the preferable reaction temperature is 140-190 ℃, and the molar ratio of the materials in the reaction is as follows:

CO₂1: 1-10: 1-0.4 of methanol and a catalyst;

when the catalyst is a mixture of potassium carbonate and methyl iodide, the preferred reaction temperature is 60-120 ℃, and the molar ratio of materials in the reaction is: CO 2₂Methanol and a catalyst are 1 to (1-8) to (1-0.01);

the metal magnesium has a particle size of 40-120 meshes, preferably 60-100 meshes, and an excessively large mesh size increases the viscosity of the reaction liquid, which affects CO₂Thereby affecting conversion; too small, the diffusion resistance of the reactants in the catalyst body increases, which is disadvantageous for the reaction.

The molar ratio of the potassium carbonate to the methyl iodide is 1: 1-10.

The present invention will be further described with reference to the following examples.

Example 1

Weighing 10g of 60-80 mesh metal magnesium, adding the metal magnesium into a mechanical stirring reaction kettle, mixing the metal magnesium with 250 ml of anhydrous methanol (analytically pure), sealing the reaction kettle, and adding food-grade CO₂The gas in the steel cylinder is firstly replaced by the reaction kettle for a plurality of times, and then the pressure is increased and the temperature is raised. The reaction was carried out at 180 ℃ and 7.5MPa for 8 hours, and the mole fraction of dimethyl carbonate in the liquid phase mixture in the reactor was 1.96%.

Example 2

Weighing 10g of 60-80 mesh metal magnesium, adding the metal magnesium into a mechanical stirring reaction kettle, mixing the metal magnesium with 250 ml of anhydrous methanol (analytically pure), sealing the reaction kettle, and adding food-grade CO₂Cylinder gas displacementThe pressure of the reaction kettle is increased and the temperature is raised after a plurality of times. The reaction was carried out at 160 ℃ and 7.0MPa for 8 hours, and the mole fraction of dimethyl carbonate in the liquid phase mixture in the reactor was 0.91%.

Example 3

Weighing 10g of 60-80 mesh metal magnesium, adding the metal magnesium into a mechanical stirring reaction kettle, mixing the metal magnesium with 250 ml of anhydrous methanol (analytically pure), sealing the reaction kettle, and adding food-grade CO₂The gas in the steel cylinder is firstly replaced by the reaction kettle for a plurality of times, and then the pressure is increased and the temperature is raised. Reacting at 190 deg.C and 8.0MPa for 10 hr, wherein the mole fraction of dimethyl carbonate in the liquid phase mixture in the reactor is1.32％。

Example 4

Weighing 8g of 60-80 mesh metal magnesium, adding the metal magnesium into a mechanical stirring reaction kettle, mixing the metal magnesium with 250 ml of anhydrous methanol (analytically pure), sealing, and adding food-grade CO₂The gas in the steel cylinder is firstly replaced by the reaction kettle for a plurality of times, and then the pressure is increased and the temperature is raised. The reaction was carried out at 180 ℃ and 7.5MPa for 8 hours, and the mole fraction of dimethyl carbonate in the liquid phase mixture in the reactor was 1.34%.

Example 5

Respectively weighing 8g of potassium carbonate and 10 ml of methyl iodide, adding the potassium carbonate and the methyl iodide into a mechanical stirring reaction kettle, mixing the mixture with 150 ml of anhydrous methanol (analytically pure), sealing the reaction kettle, and using food-grade CO₂The gas in the steel cylinder is firstly replaced by the reaction kettle for a plurality of times, and then the pressure is increased and the temperature is raised. The reaction was carried out at 80 ℃ and 5.5MPa for 12 hours, and the mole fraction of dimethyl carbonate in the liquid phase mixture in the reactor was 1.25%.

Example 6

Respectively weighing 8g of potassium carbonate and 10 ml of methyl iodide, adding the potassium carbonate and the methyl iodide into a mechanical stirring reaction kettle, mixing the mixture with 150 ml of anhydrous methanol (analytically pure), sealing the reaction kettle, and using food-grade CO₂The gas in the steel cylinder is firstly replaced by the reaction kettle for a plurality of times, and then the pressure is increased and the temperature is raised. The reaction was carried out at 80 ℃ and 7.5MPa for 12 hours, and the mole fraction of dimethyl carbonate in the liquid phase mixture in the reactor was 1.97%.

Example 7

Respectively weighing 8g of potassium carbonate and 10 ml of methyl iodide, adding the potassium carbonate and the methyl iodide into a mechanical stirring reaction kettle, mixing the mixture with 150 ml of anhydrous methanol (analytically pure), sealing the reaction kettle, and using food-grade CO₂The gas in the steel cylinder is firstly replaced by the reaction kettle for a plurality of times, and then the pressure is increased and the temperature is raised. The reaction was carried out at 100 ℃ and 7.5MPa for 12 hours, and the mole fraction of dimethyl carbonate in the liquid phase mixture in the reactor was 2.01%.

Example 8

Respectively weighing 10g of potassium carbonate and 10 ml of methyl iodide, adding into a mechanical stirring reaction kettle, and reacting150 ml of absolute methanol (analytically pure) are mixed, sealed and then treated with food grade CO₂The gas in the steel cylinder is firstly replaced by the reaction kettle for a plurality of times, and then the pressure is increased and the temperature is raised. The reaction was carried out at 80 ℃ and 5.5MPa for 12 hours, and the mole fraction of dimethyl carbonate in the liquid phase mixture in the reactor was 0.97%.

Example 9

Respectively weighing 8g of potassium carbonate and 15 ml of methyl iodide, adding the potassium carbonate and the methyl iodide into a mechanical stirring reaction kettle, mixing the mixture with 150 ml of anhydrous methanol (analytically pure), sealing the reaction kettle, and using food-grade CO₂The gas in the steel cylinder is firstly replaced by the reaction kettle for a plurality of times, and then the pressure is increased and the temperature is raised. The reaction was carried out at 80 ℃ and 5.5MPa for 12 hours, and the mole fraction of dimethyl carbonate in the liquid phase mixture in the reactor was 1.12%.

According to the technical scheme and the embodiment disclosed above, the method breaks through the traditional method, and the conception is novel; from the supercritical technology field, CO₂Not only creating a supercritical atmosphere, but also directly participating in the reaction, thereby being an innovation; from CO₂The method is an environment-friendly catalytic process and has potential social significance in terms of comprehensive utilization and environment improvement. The method of the invention has simple operation and easy industrial implementation, and is a promising synthesis method of dimethyl carbonate.

Claims

1. A method for directly synthesizing dimethyl carbonate by carbon dioxide and methanol under supercritical condition,

the method is characterized in that:

introducing CO₂Putting the mixture and methanol into a reactor, adding a catalyst, reacting for 4-14 hours under the conditions of 30-190 ℃ and 4.5-9.0 MPa, and after the reaction is finished, separating the obtained dimethyl carbonate from the reaction product by adopting a conventional method, wherein the catalyst is metal magnesium or a mixture of a precursor taking the metal magnesium as the catalyst and potassium carbonate and methyl iodide.

2. The method of claim 1, wherein: the catalyst is metal magnesium, the reaction temperature is 30-190 ℃, and the molar ratio of the materials in the reaction is as follows:

CO₂methanol and a catalyst are 1 to (1-10) to (1-0.4).

3. The method of claim 1, wherein: the catalyst is a mixture of potassium carbonate and methyl iodide, the reaction temperature is 60-120 ℃, and the molar ratio of the materials in the reaction is as follows:

CO₂methanol and a catalyst are 1 to (1-8) to (1-0.01).

4. The method of claim 2, wherein: the particle size of the metal magnesium is 40-120 meshes.

5. The method of claim 4, wherein: the molar ratio of the potassium carbonate to the methyl iodide is 1: 1-10.