Green Catalytic Research On Caprolactam Preparation By Liquid-phase Beckmann Rearrangement Of Cyclohexanone Oxime

Caprolactam is an important chemical raw material and organic synthesis intermediate,which is widely used in transportation,machinery,computer and other fields.The Beckmann rearrangement of cyclohexanone oxime in liquid phase using fuming sulfuric acid as a catalyst is a traditional method,which brings many problems,such as environmental pollution,corrosion of equipment,and difficulty in treating byproduct ammonium sulfate.Therefore,it is necessary to find a green,recyclable,and mild catalyst.In this paper,silica gel supported Chlorosulfuric acid was first studied as a solid acid catalyst for Beckmann rearrangement reaction,and the best reaction conditions for preparing the catalyst and Beckmann rearrangement were discussed.The best catalytic conditions were found to be the raw material silica gel:chlorosulfonic acid=1:0.2(mass ratio),reaction condition at room temperature,stirring time 3h,solvent dichloromethane,silica gel mesh number 100-200,cyclohexanone oxime:catalyst=1:1(mass ratio),The temperature is 140℃,the solvent is benzonitrile,the volume is 40mL,the reaction time is 5h,the cyclohexanone oxime conversion is 74%,and the caprolactam selectivity is 40%。Then the experiment of preparing caprolactam by Beckmann rearrangement in liquid phase using silica gel supported trifluoromethanesulfonic acid as solid acid catalyst was investigated.The best reaction conditions for preparing the catalyst and Beckmann rearrangement were discussed.The best catalytic conditions were found to be the raw material silica gel:trifluoromethanesulfonic acid=1:0.2(mass ratio),reaction conditions at room temperature,stirring time of 2.5h,solvent acetonitrile,silica gel mesh number of 100-200,Cyclohexanone oxime:catalyst=1:2(mass ratio),temperature:130℃ solvent:benzonitrile,volume:30mL,reaction time:4h,cyclohexanone oxime conversion rate:90%,caprolactam selectivity:90%。...