Comprehensive Study for Vapor Phase Beckmann Rearrangement Reaction over Zeolite Systems

Replacement of homogeneous catalysis systems by heterogeneous catalysis systems is widely accepted throughout academia and industry due to ecological concerns, difficulty of separations, and nonrecyclability of homogeneous catalysts. Among several heterogeneous catalysts, the zeolite system has been focused extensively on vapor phase Beckmann reactions for a few decades. In this article a review of the factors affecting the cyclohexanone oxime conversion and e-caprolactam selectivity over different zeolite systems is presented. It can be concluded that several catalyst preparation parameters such as Si/Al ratio, different metal/nonmetal loading, micropore size, and postsynthesis treatment as well as catalyst preparation parameters like temperature and solvent have crucial roles in deciding cyclohexanone oxime conversion and product selectivity over microporous zeolite catalysts. In the last section, an attempt was made to summarize the reaction mechanism for this reaction over zeolite catalyst systems. This thorough study might be useful for efficient design of a microporous zeolite system toward Beckmann rearrangement reactions.