(441d) A Modified Mixed-Acid Catalytic System for Beckmann Rearrangement of Cyclohexanone Oxime in a Microreactor

ε-Caprolactam (CPL), the precursor of nylon-6, is mainly produced through Beckmann rearrangement of cyclohexanone oxime catalyzed by oleum in industry. To improve the mixing performance and reaction selectivity of this conventional process, a mixed-acid catalytic system which contains trifluoroacetic acid (TFA) and oleum was firstly proposed and modified in a microchemical system. The effects of experimental parameters on the content of octahydrophenazine (OHP), which are SO₃ concentration, temperature, TFA to oleum ratio (T/A), oleum to oxime ratio (A/O), and TFA distribution in two fluids, were investigated in the microreactor. The content of OHP was reduced with the decrease of temperature and the increase of SO₃ concentration. T/A, and A/O. In addition, a proper TFA distribution is also beneficial for the reaction. A very low content (<1.0 ppm) of OHP was reached under the optimized conditions, which is accord with the requirement of superior-quality CPL.