Cyclohexanone ammoximation over TS-1 catalyst without organic solvent in a microreaction system

We herein propose a highly efficient technology for the synthesis of cyclohexanone oxime, a key intermediate for the production of caprolactam. The classical cyclohexanone ammoximation over TS-1 catalyst needs t-butanol as the organic solvent to change the reaction system from liquid-liquid-solid to liquid-solid for much better reaction performances, which greatly increases the reactor size and the downstream separation cost. In this work, a solvent-free liquid-liquid-solid heterogeneous reaction was successfully implemented in a microreaction system containing two T-junction microreactors. The effects of temperature, pressure, residence time, concentrations of reactants and catalyst on the reaction performance were systematically investigated. This developed technology resulted in a 99.87% conversion of cyclohexanone and nearly 100% selectivity to cyclohexanone oxime within 3 min. These results indicate that the new process could provide a more environmental friendly and economic approach to caprolactam industry.