Continuous Synthesis of <i>N</i>-Cyclohexyl-2-benzothiazole Sulfenamide with Microfluidics and Its Kinetic Study
Hanrong Li, Feiyan Han, Linjing Jiang, Tongqian Yang, Le Du, Jiqin Zhu
Abstract
Sulfenamides have attracted much attention for their significant role in rubber vulcanization. In this study, a continuous process to synthesize N-cyclohexyl-2-benzothiazole sulfenamide (CBS) with microfluidics was developed. The catalytic oxidation of 2-mercaptobenzothiazole (MBT) and cyclohexylamine using pure oxygen was performed in capillary microreactors with gas–liquid segmented flow. The residence time was shortened to 200 s owing to the enhancement of mass transfer in the microreactor. Reaction conditions such as flow rates, concentrations of copper acetate monohydrate and ammonia, temperatures, and pressures were systematically investigated. A high yield toward CBS of 87% was obtained. A simplified kinetic model (0 and 0.56 order with respect to MBT and pure oxygen, respectively) was established with operation in the kinetic-control region based on eliminating mass transfer resistance.