US Patent 5 101 045 reported that mixed oxides such as Co, Cu, and Mn (after activation) were used as catalysts to directly synthesize Methyl Pyrrolidone by reacting with methylamine at 250°C and 20MPa high pressure, with a yield of more than 80%. The one-step method for synthesizing Methyl Pyrrolidone from maleic anhydride is derived from the fact that y-butyrolactone is prepared by partial catalytic hydrogenation of maleic anhydride.
When preparing the potassium salt of the main catalyst 2-pyrrolidone, no special method is required to remove the water generated by the reaction, because this type of co-catalyst has a protective effect on the potassium salt of 2-pyrrolidone main catalyst, making the activity of the main catalyst basically unaffected by trace water. Therefore, when preparing the main catalyst, it is sufficient to carry out the reaction at 90~120°C for 0.5~1.5h to remove the generated water, and there is no need to use reduced pressure distillation to remove the generated water. When the water content in the raw material 2-pyrrolidone reaches 5×10~", the yield of the target product NVP can also reach more than 90%.
So far, the Reppe method is still the main method for NVP production. Due to its defects, such as many reaction steps, long processes, harsh conditions, many by-products, low yield, and high operating risk, people have been continuously studying the improvement of the Reppe method for a long time. The focus of the research is on changing the synthesis route and developing new catalytic systems.
The raw material pyrrolidone in the pyrrolidone method is prepared by the reaction of y-butyrolactone and anhydrous ammonia, while the direct dehydration method and the indirect dehydration method both use y-butyrolactone as the starting material. It can be seen that in the synthesis of NVP, maleic anhydride, and deca-butyrolactone occupy an irreplaceable position as raw materials for the synthesis reaction. NVP and N-methyl pyrrolidone have similar structures, both belong to pyrrolidone substances, and their preparation methods are similar. It can be foreseen that the one-step method of preparing NVP is not only a monomer for synthesizing PVP, but also a compound with important uses.
