Continuous kilogram-scale process for the synthesis strategy of 1,3,5-trimethyl-2-nitrobenzene in microreactor

Abstract

1,3,5-trimethyl-2-nitrobenzene is a valuable synthetic intermediate with essential applications in the dyes industry. Because of poor micro-mixing and the large consumption of waste acid using the traditional reactor, the content of impurity and the yield of 1,3,5-trimethyl-2-nitrobenzene are not stable. Therefore, a continuous kilogram-scale process for the synthesis strategy of 1,3,5-trimethyl-2-nitrobenzene in microreactor was reported in this paper. Two microreactors and three pumps quickly assemble the microflow system. Mesitylene was first mixed with nitric acid and then combined with sulfuric acid under-designed experimental parameters. The effects of process parameters in the three synthetic strategies, including an organic solvent, temperature, molar ratio, flow rate, and sulfuric acid content, were systemically investigated. Based on the results of process parameter optimization, the production of 1,3,5-trimethyl-2-nitrobenzene at the kilogram level was achieved in a microreactor with two microreactors in series. Compared with the traditional batch reactor, sulfuric acid consumption was decreased by 7.6 times, and the reaction time was reduced from 4h to 60s. Compared with the synthesis methods reported in the literature, the two-step synthesis method proposed in this paper has better advantages in terms of reaction time, product purity, and conversion rate. It provides a new synthetic strategy for the industrial production of aromatic compounds by nitration reaction.