Continuous Synthesis of N-Cyclohexyl-2-benzothiazole Sulfenamide with Microfluidics and Its Kinetic Study

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.