Theoretical Study on Vapor Phase Beckmann Rearrangement of Cyclohexanone Oxime over a High Silica MFI Zeolite

摘要

High silica MFI zeolite catalyst has developed for the vapor phase Beckmann rearrangement of cyclohexanone oxime to epsilon-caprolactam. Sumitomo Chemical Co., Ltd. has started the vapor phase process in 1999 at Niihama. This catalyst does not possess acidity that can be detected by ammonia TPD. We have studied an activation mechanism of cyclohexanone oxime in a pore of high silica MFI zeolite by using PIO analysis proposed by H. Fujimoto et al. DFT calculation reveals that the bond length of N-OH becomes longer when water coordinates on oxygen of oxime. The PIO clearly shows out-of-phase interaction between N and O. This out-of-phase interaction is also observed in the PIO of oxime/MFI zeolite cluster model and weakens the N-O bond. Hydrogen bond of Si-OH of nest silanols to oxime is a trigger of vapor phase Beckmann rearrangement.