According to the raw materials, there are more than 10 synthetic methods for accelerator M, such as aniline method (also known as high pressure method), o-nitrochlorobenzene method (also known as normal pressure method), N-methylaniline method, N,N- The dimethylformamide method, the benzothiazole method, etc., but most of the methods have not been industrialized due to low yield and high cost. The industrialized methods include the aniline method and the o-nitrochlorobenzene method. The o-nitrochlorobenzene method has been basically eliminated at home and abroad due to the high cost of raw materials and the production of a large amount of high-salt wastewater that is difficult to handle. At present, the production of accelerator m basically adopts the high pressure synthesis method with aniline as raw material. There are mainly two kinds of high-pressure synthesis methods using aniline as raw material. One is the batch production method of pure aniline system (also known as the stuffy tank method), which is currently adopted by most domestic manufacturers; the other is to replace part of aniline with nitrobenzene. It is reported that only Sinopec Nanjing Chemical Industry Co., Ltd. adopts this method in China.

1. Aniline method (batch method)

The aniline method is to put a certain proportion of aniline, carbon disulfide and sulfur into the autoclave at one time, and after heating up, keep the reaction temperature at 250-260°C and the pressure at 9-10MPa'F to react to generate crude accelerator m and waste gas hydrogen sulfide, Then, the temperature is lowered and the pressure is lowered. The exhaust gas hydrogen sulfide is purged and incinerated back to sulfur through the Claus incinerator. The crude accelerator m is purified by the acid-base method or the solvent method to obtain the finished accelerator M. This method is intermittently produced, operates frequently, has problems of flammability and explosion, easy leakage of toxic and harmful gases, poor safety and environment; poor material mixing, low yield in terms of aniline, about 85%. Reaction formula of aniline synthesis accelerator m.

2. Aniline/nitrobenzene method (continuous method)

Aniline, nitrobenzene method (continuous method): aniline, nitrobenzene and benzothiazole used for recycling are mixed in a certain mass ratio to prepare raw material NEX (the mass of nitrobenzene accounts for 0-40% of the mass of NEX), carbon disulfide and The sulfur is mixed to form the raw material CAS, and then the two materials are pumped into the high-pressure reactor by a high-pressure pump in a certain proportion, and the reaction is carried out at a temperature of 220-280 ° C and a pressure of 7 MPa. The resulting accelerator M, benzothiazole, hydrogen sulfide and other mixtures from The autoclave is depressurized and then discharged into the stripping tower. After stripping, the liquid phase substance is used to obtain the crude product accelerator M, and the crude product accelerator M is purified by the acid-base method or solvent method to obtain the finished product accelerator m; the gas phase substance is cooled. , After condensation, thiazole and carbon disulfide are recovered, and hydrogen sulfide gas is sent to incineration equipment to prepare sulfuric acid and by-product steam. The method realizes continuous operation and safety interlocking, high degree of automatic control, good production operation environment and safety, better material mixing than batch production, and realizes the recovery and application of benzothiazole. The yield in terms of aniline is About 89%, currently exploring to strengthen the mixing of materials by adding a reactor stirring device, adjusting the ratio of nitrobenzene mass to NEx mass, and using catalysts that can reduce temperature and pressure, improve yield and reduce by-products to optimize production. process to further improve product yield. Reaction formula of aniline, nitrobenzene synthesis accelerator M.