Green Catalysis Of Liquid-phase Rearrangement For Cyclohexanone Oxime To ε-caprolactam

s-caprolactam (CPL) is a major organic chemical material and a monomer of Nylon 6 and other polyamide plastics mainly used in textile and the electronic industry. It is industrially produced mostly by Beckmann rearrangement process. Traditionally these reactions are carried out under strong acids (oleum and sulfuric acid), leading to several disadvantages, such as equipment erosion, environment pollution and generation of a large amount of ammonium sulfate. Nowadays, new gas-phase Beckmann rearrangement route has got attention by researchers, but it also comes with some disadvantages such as catalyst deposition and deactivation. Therefore, the development of novel catalysts for this process has become particularly important which can overcome all these problems, In the current research, several solid acid catalysts used for liquid phase Backman rearrangement catalytic performance for preparing caprolactam were investigated. The results showed that the sulfonic acid resin Amberlyst36 (sulfonic acid resin acid 4.9 mmol H+/g) exhibited best catalytic effect among others. The conditions were:the reaction temperature 110 ℃, the reaction time 7 h, cyclohexanone oxime:catalyst= 2:1, the raw material concentration 0.1 g·mL-1, the conversion rate of CHO 93.93%, the selectivity of CPL 87.54%. The catalytic mechanism of this catalyst is also elaborated. Also, several novel functional B acid ionic liquids were prepared and characterized. All of these are researched for their effect on liquid phase rearrangement reaction. It was found that the acidic ionic liquid [HSO3Bmim][HSO4] demonstrated the best catalytic performance in the study. The rearrangement reaction conditions for the catalyst were optimized. The reaction parameters used are the reaction time, reaction temperature, amount of ionic liquid and the amount of ZnCl2 with the yield of CPL as the outcome. The influence of a variety of factors by using Design-expert software is also discussed. The experimental results show that the optimal conditions of rearrangement reaction catalyzed by ionic liquid were reaction time 5.7 h, the reaction temperature 80℃, the amount of catalyst 0.24 mmol, ZnCl2 dosage is 1 mmol and the maximum yield of caprolactam is 79.47%. Finally, the ionic liquid was supported on graphite oxide obtaining the supported ionic liquid catalyst. It was easy to separate from the product, environmentally friendly and recyclable. Experimental results showed that using supported ionic liquid as catalyst, cyclohexanone oxime conversion rate can reach 89.46%, the selectivity of caprolactam can achieve 96.35%. It is assumed that this study will be beneficial in future research for Beckmann rearrangement reaction using ionic liquids in view of green chemistry concepts.