| Gas-phase Beckmann rearrangement（BR）of cyclohexanone oxime（CHO）is a key solution for the clean production of caprolactam（CPL）.The literature has reported that the catalytic activity of TS-1 titanosilicate in the gas-phase Beckman rearrangement reaction is better than that of Silicalite-1（S-1）zeolite.In this paper,with purpose to develop highly effective TS-1 catalyst for the gas-phase BR reaction,chemical modification of TS-1 and its activity evaluation in the BR reaction have been carried out,which is composed of following two parts.First,the gas-phase Beckmann rearrangement（BR）of cyclohexanone oxime to caprolactam has been studied over various titanosilicates with different topologies.Superior to Ti-MWW,Ti-Beta and Ti-MOR,TS-1 showed the best catalytic performance.The effecting factors of Ti content,reaction parameters and regeneration test on the BR reaction over TS-1 have also been investigated.The hydroxyl groups,generated form adjacent to the“open”Ti sites,were proved to be the active centers for catalyzing BR reaction form CHO to CPL,whereas the Lewis acid sites directly related to tetrahedral Ti were not the true active ones.Other silanols including external silanols,hydrogen-bonded silanols and hydrogen-bonded silanol nests were also considered to be the active centers of BR reaction.Secondary,the chemical modifications have been optimized for the exploration of more effective TS-1 for the Beckamnn rearrangement reaction.The results demonstrated that the composition of 1 Si O2:0.03 TPAOH:0.03（NH4）2CO3:18 H2O and hydrothermal treatment at 443 K for 24 h were the best modification conditions.In addition,hierarchically porous TS-1 was synthesized successfully by post-treatment to investigate the effect of diffusion properties on catalytic performance.Moreover,the modified materials were used to screen out the catalytic reaction conditions for the gas-phase Beckman rearrangement.The regeneration of the catalyst was also investigated in gas-pahse Beckmann rearrangement. |
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