Study On Synthesis Of Pendimethalin By Green Nitration With Microreactor

N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitroaniline, commonly known as pendimethalin, is a typical one of many dinitroaniline compounds. However, the catalytic hydrogenation process cost a lot and the synthesis is associated with generation of nitrosamines byproducts. In this dissertation, a low-cost and green synthesis process without any nitrosamines byproducts is explored by optimizing the reaction conditions with microreactor.3,4-dimethylaniline,3-pentanone, ethanol, NaBH4, HNO3 were set as reactants and N-(1-ethylpropyl)-3,4-dimethylaniline was generated first. And then pendimethalin was synthesized by green nitration through microreactor technology, benefitting from its incomparably great specific surface area and excellent heat and mass transfer characteristics. The effects of solvent, catalyst material ratio, liquid hourly space velocity (LHSV), reaction time and other factors on the reaction were focused.During the imine synthesis stage: when the content of cyclohexane as solvent was 71% (of total molar amount), acetic acid catalyst was 3%(of total mass), the molar ratio of 3,4 dimethylaniline and 3-pentanone was 1:1.2, reflux time was 8h, the reaction conversion rate was 97.2%; At the imine reduction stage in NaBH4-ethanol system, when the molar ratio of imine and NaBH4 was 1:1.5, the reaction time was 1.5h, the yield of N-(1-ethyl-propyl)-3,4-dimethyl aniline was 98.8%.At the stage of pendimethalin synthesized by N-(1-ethylpropyl)-3,4-dimethylaniline, to eliminate carcinogenic nitrosamine by-products, three steps were conducted in the microreactor. During the experiment, the effect of liquid hourly space velocity (LHSV), residence time and reactants ratio was studied and the desired result was obtained:single-step yield was over 98% and the total yield of three steps was over 95.8%.