N-Methyl-2-Pyrrolidone CAS 872-50-4

The non-catalytic reaction of γ-butyrolactone and monomethylamine to synthesize N-methylpyrrolidone is the most classical synthesis method. As early as 1936, NMP was synthesized with greater than 90% conversion in a batch reactor with a large excess of methylamine. In 1946, it was introduced in the Proceedings of the American Chemical Society that the NMP yield was greater than 90% in a batch reactor with a temperature of 280 °C and a 1-fold excess of methylamine. In the 1990s, Pantohimi Co., Ltd. (Belgium) developed a process for the continuous non-catalytic synthesis of N-methylpyrrolidone by the reaction of γ-butyrolactone and monomethylamine, as shown in the figure:

Ammonia and methanol react under the action of an amination catalyst to form a mixture of monomethylamine, dimethylamine (DMA) and trimethylamine (TMA). Investment and operating costs increase. At the beginning of the 21st century, German BASF company developed a new process for preparing N-methylpyrrolidone using mixed amine as raw material instead of MMA. This process has the advantages of low investment, low raw material price and low consumption of public works. The water content is less than 0.05%.

The traditional method of synthesizing N-methylpyrrolidone by non-catalytic conversion of γ-butyrolactone often requires high temperature and pressure, high equipment requirements and large energy consumption, while the use of catalysts can reduce reaction conditions and save energy. SK Company in South Korea has explored and studied the catalytic synthesis process of molecular sieves to ease the reaction conditions. Puyang Maiqi Technology Co., Ltd. introduced a new type of ZSM molecular sieve-cerium oxide composite catalyst. The rare earth cerium is the main active catalytic component, which makes the reaction of γ-butyrolactone extremely sufficient, and the conversion rate and selectivity are high.

The process uses γ-butyrolactone with a purity of more than 99.0% and 40% monomethylamine solution as raw materials, the molar ratio of γ-butyrolactone to methylamine is 1:1.0~1.4, and the new ZSM molecular sieve composite rare earth cerium catalyst The addition amount is 0.01%～0.5% of the monomethylamine solution, wherein the content of rare earth cerium is 1%～10%, and the γ-butyrolactone and methylamine solution are continuously pumped into the casing with a high pressure metering pump in a molar ratio. The reaction is carried out in a type reactor. The pressure of the reaction is first controlled by the pressure control system to control the liquid level of the pressure balance tank to stabilize the pressure of 4.0~6.0 MPa. After the liquid level reaches 60%~70% of the total liquid level, the The nitrogen gas is withdrawn to the liquid level of 3% to 10% of the total liquid level, and the pressure of the whole process is kept stable at 4.0 to 6.0 MPa. The conversion rate of γ-butyrolactone is over 99.9%, and the selectivity of NMP obtained is 99%.

In the existing technology, some commercial γ-butyrolactones are obtained by using 1,4-butanediol as a raw material, through dehydrogenation reaction and rectification. (Zn) oxide was used as a catalyst to dehydrogenate 1,4-butanediol at a liquid hourly space velocity of 0.5 to 3.0 h – 1 at 200~250 ℃ and 0.1~0.5 MPa, and the result was 1, The conversion rate of 4-butanediol was 99%, and the selectivity of γ-butyrolactone was 97%. In this way, if 1,4-butanediol is used as a raw material, γ-butyrolactone is obtained by dehydrogenation reaction and rectification, and then N-methylpyrrolidone is prepared by amination reaction. Product cost increases.

For this reason, if the amination reaction is carried out after the direct dehydrogenation reaction of 1,4-butanediol, the intermediate step will be omitted, the process operation steps and energy consumption will be reduced, and the cost will be reduced. China Petrochemical Corporation developed a method for preparing N-methylpyrrolidone by dehydrogenation-amination of 1,4-butanediol in the 1990s. In a hydrogen atmosphere diluted by an inert gas, reduce at 150~300 °C and 0.1~1.0 MPa for 5~40 h, and then dissolve 1,4-butanediol in the presence of a diluent gas, and then continuously feed it into a pre-processed solution. The dehydrogenation reaction is carried out in the reactor of the reduced catalyst mentioned above.

1,4-Butanediol feed liquid hourly space velocity is 0.5~7.0 h, gas/alcohol molar ratio is 1~50:1 during the reaction, temperature is 175~230 °C, pressure is 0.1~- 1.0 MPa, and the effluent after the reaction is condensed , After degassing, it is directly mixed with methylamine and water according to the molar ratio of 1:(1~4):(2~9), and then sent to the amination reactor, pressure 5~10 MPa, temperature 200~300 ℃, stay For 0.5-5.0 h, the reaction product is subjected to condensation, gas-liquid separation and distillation to obtain N-methylpyrrolidone with a purity greater than 99%.