Synthesis of epsilon-caprolactam from cyclohexanone oxime using zeolites Hbeta, HZSM-5, and alumina pillared montmorillonite

The Beckmann rearrangement of cyclohexanone oxime (CHO) to epsilon -caprola ctam (epsilon -C) was Studied in a plug flow reactor at 300-400 degreesC un der atmospheric pressure by using H beta, ZSM-5, and alumina pillared montm orillonite. With H beta (X)Y zeolites, raising the SiO2/Al2O3 molar ratio ( X) results in the enhancement of catalyst acid strength with concomitant de crease of the total acid amount. Increasing the calcination temperature (Y) causes remarkable diminution of catalyst surface area, acid strength, and acid amount. A similar trend was found for AlPMY catalysts. In the reaction of CHO, the initial catalytic activity correlates well with the total acid amount of various catalysts except for H beta (IO)Y (Y > 600 degreesC). Th e reaction proceeds on both Bronsted and Lewis acid sites and the catalyst deactivation most likely occurs at the strong Bronsted acid sites. The effe ct of solvents in the feed on the catalytic results was also investigated; it was found that polar solvents such as ethanol or n-butanol give high eps ilon -C yield and longer catalyst lifetime. In the reaction of CHO/C2H5OH o ver H betaP(10)800 at 400 degreesC and W/F 74.6 g.h/mol, the CHO conversion and epsilon -C yield remain 100% and 92%, respectively, for at least 20 h time-on-stream. The reaction paths and the mechanism for epsilon -C formati on are proposed.