Method for producing dimethyl carbonate by urea alcoholysis method

Abstract

The invention discloses a method for producing dimethyl carbonate by a urea alcoholysis method. The method comprises the following steps: preparing urea by using carbon dioxide and liquid ammonia as raw materials, and then preparing dimethyl carbonate and ammonia by directly allowing urea and methanol as raw materials to react under the basic compound liquid catalyst condition. The basic compound liquid catalyst is prepared from methylamine, sodium methoxide and methanol, wherein the methylamine accounts for 25% to 35%, the sodium methoxide accounts for 15% to 25%, and the methanol accounts for 45% to 55%. The method and the novel catalyst provided by the invention solve the problems that the raw materials are high in cost, the catalyst is high in cost, the use amount is large, and by-products are difficult to separate in the prior art, the urea conversion rate and the product yield are greatly improved, the amounts of dimethyl ether and other by-products are reduced, and the service life of the catalyst is also greatly prolonged. The method provided by the invention has important and practical significance for improving the overall technical level of dimethyl carbonate industry in China.

Description

technical field [0001] The invention relates to a method for producing dimethyl carbonate by urea alcoholysis. Background technique [0002] Dimethyl carbonate has a variety of reactivity characteristics and a variety of excellent performance characteristics, and is widely used in coatings, food, medicine, fuel additives, energy and other fields. According to incomplete statistics, dimethyl carbonate, as the source material of fine chemical synthesis, has accounted for 12.7% of the entire organic fine chemical industry. Dimethyl carbonate is an environmentally friendly green raw material. It has passed the registration of non-toxic chemicals in Europe. It is called "green chemical" and is recognized as the "new cornerstone" of green organic synthesis. At the same time, it can also be used as a green additive for other products. Because it is a "green chemical" product and meets the requirements of the sustainable development strategy, all countries in the world have streng...

AI Technical Summary

Problems solved by technology

[0004] 1. The methanol solution of sodium methoxide is used as a catalyst in the production of dimethyl carbonate by transesterification. The core is that sodium methoxide plays a catalytic role. The process is mature and the conversion rate is high. The disadvantage is that the dosage is large, and the proportion of ingredients is propylene carbon: methanol: sodium methoxide = 100:126:7

The amount of sodium methoxide is large, accounting for a high production cost

[0005] 2. In the transesterification reaction between propylene carbonate and methanol to generate dimethyl carbonate, it is difficult to separate the propylene glycol and sodium methoxide catalyst in the reaction product system

Because sodium methoxide is strongly alkaline, it is not only easy to corrode equipment, but also causes propylene glycol and catalysts to easily form viscous aggregates. At the same time, a large number of high polymers such as dipropylene glycol and tripropylene glycol are produced by side reactions, which gradually accumulate in the production device system. In order to ensure the normal operation of the production unit, it must be discharged regularly, reducing the yield of propylene glycol and easily causing environmental pollution

[0006] 3. The propylene glycol recovery system adopts vacuum intermittent rectification or continuous rectification process. During the rectification process, it is difficult to accurately control the propylene glycol stripping period. 2% polypropylene glycol high boilers are entrained in propylene glycol, which makes the product quality difficult to stabilize. Affect the color of the product; at the same time, the water in the system causes the sodium methoxide catalyst to form sodium carbonate solid and deposit, which affects the normal operation of the equipment

[0007] 4. The raw material propylene oxide takes up a large proportion of the production cost, and the price changes rapidly, fluctuating. The price of propylene oxide directly determines the profit of dimethyl carbonate, and the domestic production is low. It is mainly supplied to the polyether production industry. It is difficult to guarantee the normal supply of raw materials

Images