阅读说明：本技术 一种合成n-甲基氨基甲酸甲酯的方法 (Method for synthesizing N-methyl carbamate ) 是由 仲力 于 2020-12-18 设计创作，主要内容包括：一种合成N-甲基氨基甲酸甲酯的方法,涉及精细化工产品的化学合成技术领域。在反应釜内具有氮气的氛围中,将尿素和过量甲醇混合进行反应,反应结束后,经降温、卸压、移出反应物、回收甲醇后进行蒸馏,收集167～168℃馏段,即得N-甲基氨基甲酸甲酯。本发明转化率高,原料易得、流程简单、原料转化率高、产品选择性好、副产物也有良好的商业价值,制备过程中不使用任何催化剂,既减少后续分离工序的麻烦,也提高生产的安全性。(A method for synthesizing N-methyl carbamate relates to the technical field of chemical synthesis of fine chemical products. Mixing urea and excessive methanol in a nitrogen atmosphere in a reaction kettle for reaction, cooling, releasing pressure, removing reactants, recovering methanol, distilling, and collecting 167-168 ℃ fraction to obtain the N-methyl carbamate. The method has the advantages of high conversion rate, easily obtained raw materials, simple flow, high raw material conversion rate, good product selectivity and good commercial value of byproducts, does not use any catalyst in the preparation process, reduces the trouble of subsequent separation procedures, and improves the production safety.)

1. A method for synthesizing N-methyl carbamate is characterized in that: mixing urea and excessive methanol in an atmosphere with nitrogen in a reaction kettle, heating the materials in the reaction kettle to 220-240 ℃, keeping the pressure at 5.92-7.96 MPa, reacting, cooling, relieving the pressure, removing the reactants, recovering the excessive methanol, distilling, and collecting the fraction at 167-168 ℃ to obtain the N-methyl carbamate.

2. The process for the synthesis of methyl N-methylcarbamate according to claim 1, wherein: the mixed feeding of the urea and the methanol is performed according to the molar ratio of 1: 10-20.

3. The process for the synthesis of methyl N-methylcarbamate according to claim 1, wherein: and heating the materials in the reaction kettle to 220-240 ℃ at a heating rate of 3-4 ℃/min.

Technical Field

The invention relates to the technical field of synthesis of N-methyl carbamate.

Background

Methyl N-methylcarbamate is an important fine chemical product. The raw materials can be used for producing various high-efficiency and low-toxicity carbamate pesticides in the pesticide industry; can be used for synthesizing intermediate raw materials of the antithrombotic drug riociguat in medicine; the electrolyte is used for developing liquid electrolyte and gel electrolyte in the lithium battery industry; it also has wide application in chemical industry and paint industry.

At present, the product is still in the development stage in China, and the published literature records mainly comprise the following synthetic methods:

the method comprises the following steps: the Chinese patent application publication No. CN103524381A is prepared by mixing dimethyl carbonate and 1, 3-dimethyl urea as raw materials according to a molar ratio of 15-1: 1, and reacting at 80-200 ℃ and 0.1-5.0 MPa under the action of a catalyst of dibutyl tin oxide (DBTO).

The second method comprises the following steps: the synthesis of N-methyl carbamate is disclosed in Fine chemical industry 2014, 31, No. 5, and the raw material route and the process conditions are basically the same.

In the method, the adopted raw material 1, 3-dimethylurea is not easy to obtain, a catalyst is required to be used in the reaction, and the invalid catalyst needs to be treated as solid waste according to the current environmental protection laws and regulations, so that the environmental protection is influenced to a certain extent. Except increasing production cost, filtration and separation are required during subsequent treatment, the poor separation can also influence the product purity, and the environmental protection treatment difficulty of the spent catalyst is high.

Disclosure of Invention

The invention aims to overcome the defects and provides a novel method for synthesizing N-methyl carbamate.

The technical scheme of the invention is as follows: mixing urea and excessive methanol in an atmosphere with nitrogen in a reaction kettle, heating the materials in the reaction kettle to 220-240 ℃, keeping the pressure at 5.92-7.96 MPa, reacting, cooling, relieving the pressure, removing the reactants, recovering the excessive methanol, distilling, and collecting the fraction at 167-168 ℃ to obtain the N-methyl carbamate.

Through repeated research, the inventor finds that excessive methanol is beneficial to the reaction for generating the N-methyl carbamate and is beneficial to improving the selectivity of the N-methyl carbamate. The main product of the reaction under the above conditions is N-methyl carbamate, the total conversion rate of the urea raw material is up to 99.5% by urea, the selectivity once-through yield of the N-methyl carbamate is 61.2-78.35%, and the purity of the obtained N-methyl carbamate reaches 99.5%.

The invention has high conversion rate, the distillation residue is methyl carbamate and a small amount of urea condensate, and the methyl carbamate fraction can be separated and refined separately to be sold as a product. The excessive methanol can be recycled after being recovered.

The method has the advantages of easily available raw materials, simple flow, high conversion rate of the raw materials, good product selectivity and good commercial value of byproducts, does not use any catalyst in the preparation process, reduces the trouble of subsequent separation procedures, improves the production safety, and is a synthetic method suitable for industrial mass production of the N-methyl carbamate.

The mixed feeding of the urea and the methanol is performed according to the molar ratio of 1: 10-20. Repeated research shows that if the feeding molar ratio of urea to methanol is less than 1: 10, the selectivity of N-methyl carbamate is reduced; if the feeding mol ratio of the urea to the methanol is more than 1: 20, the selectivity is not obviously improved, the output capacity of the unit volume of the reaction kettle is reduced, and the energy consumption is increased when the turnover amount of the methanol is too large. The factors of product selectivity, equipment productivity and energy consumption are comprehensively considered, and the feeding molar ratio of urea to methanol is proper to be 1: 10-20.

In addition, the temperature of the materials in the reaction kettle is increased to 220-240 ℃ at a temperature increasing speed of 3-4 ℃/min. The temperature rise speed not only considers the safe use of high-pressure equipment, but also ensures that reaction materials enter an optimal reaction temperature area as soon as possible, and improves the selectivity of the N-methyl carbamate.

Detailed Description

Firstly, preparing N-methyl carbamate:

example 1:

adding 60g (1 mol) of urea and 300g of methanol into a 1L high-pressure reaction kettle with an alcohol-ammonia separator, sealing the reaction kettle, filling nitrogen into the reaction kettle to 0.6MPa, discharging to 0.1MPa, continuously replacing for 4 times, and keeping the nitrogen residual pressure of 0.1MPa at the last time.

And (3) after checking that valves of the reaction kettle and the alcohol-ammonia separator are in correct positions, opening a stirrer (the rotating speed is 100-200 rpm), opening an electric heating system, heating the material to 220 ℃ at the heating speed of 3-4 ℃/min, and keeping the equilibrium pressure at 5.92MPa at the temperature. After maintaining the temperature for 15 minutes, separating methanol, ammonia gas and carbon dioxide by an alcohol-ammonia separator, returning the methanol to the reaction kettle, continuously discharging the ammonia gas and the carbon dioxide generated by the reaction out of the reaction system, and introducing the ammonia gas and the carbon dioxide into an absorption device.

When the temperature of the reaction mass is kept at 220 ℃ and the total pressure is reduced to about 4.24 MPa, the reaction is basically finished. Stopping heating, cooling the material to normal temperature through cooling liquid, extruding out reactant by nitrogen, and transferring into a rectifying tower.

According to the conventional operation, a 65-78 ℃ fraction is collected, mainly excess methanol, and is reused for the next reaction. The front cut fraction is at 78-165 ℃. And collecting a 166-168 ℃ fraction to obtain 54.5g of N-methyl carbamate with the product selectivity of 61.2%.

Example 2:

the other process conditions were the same as in example 1, and the raw materials and reaction temperature were as follows:

60g of urea and 300g of methanol are added, and the reaction temperature is 240 ℃, so that 61.9 g of a product is obtained.

Example 3:

the other process conditions were the same as in example 1, and the raw materials and reaction temperature were as follows:

60g of urea and 390g of methanol are added, and the reaction temperature is 220 ℃, so that 58.5 g of a product is obtained.

Example 4:

the other process conditions were the same as in example 1, and the raw materials and reaction temperature were as follows:

60g of urea and 500g of methanol are added, and the reaction temperature is 220 ℃, so that 64.4 g of the product is obtained.

Example 5:

the other process conditions were the same as in example 1, and the raw materials and reaction temperature were as follows:

60g of urea and 600g of methanol are added, the reaction temperature is 230 ℃, and the product g is 69.7 g.

Comparative data for the second and the above examples are shown in the following table:

as can be seen from the above table: under the conditions that the feeding molar ratio of urea to methanol is within 1: 10-20, the reaction temperature is 220-240 ℃ and the pressure is 5.92-7.96 MPa, the urea conversion rate is close to 100 percent, and the yield (selectivity) of the N-methyl carbamate is 61.2-78.3 percent.