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

The Beckmann rearrangement of cyclohexanone oxime (CHO) to epsilon -caprolactam (epsilon -C) was Studied in a plug flow reactor at 300-400 degreesC under atmospheric pressure by using H beta, ZSM-5, and alumina pillared montmorillonite. With H beta (X)Y zeolites, raising the SiO2/Al2O3 molar ratio (X) results in the enhancement of catalyst acid strength with concomitant decrease 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). The reaction proceeds on both Bronsted and Lewis acid sites and the catalyst deactivation most likely occurs at the strong Bronsted acid sites. The effect 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 epsilon -C yield and longer catalyst lifetime. In the reaction of CHO/C2H5OH over 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 formation are proposed.