Fast Synthesis Of Titanium Silicalites-1

As an important member of the family of microporous molecular sieves,titanium silicalite-1?TS-1?has been widely used in propylene epoxidation because of its excellent catalytic performance in selective oxidation reaction with hydrogen peroxide as the oxidant.However,in the preparation of TS-1,the production cost is high due to the heavy use of expensive template.In order to reduce the consumption of template in the preparation process of TS-1 and reduce the cost,it is of great significance to find a preparation method with simpler operation and higher efficiency.In this paper,we develop an NMP-assisted method to synthesize TS-1 with tetraethyl orthosilicate?TEOS?,tetrabutyl titanate?TBOT?and TPAOH as silicon source,titanium source,and template agent,respectively.By adding N-methyl-2-pyrrolidone?NMP?or amide into the synthetic gel,high-performance TS-1 samples were rapidly prepared,which greatly shortened the crystallization time.Meanwhile,TS-1 with higher yield can be obtained at lower amount of template.The samples were characterized by XRD,UV-Vis and FT-IR,and used as catalysts in propylene epoxidation.The results are as follows:1.TS-1 was synthesized by hydrothermal method using NMP as promoter.The effects of NMP on the required crystallization time and NMP the amount of template to obtain TS-1 and the way of adding NMP on the synthesis and catalytic performance of TS-1 were investigated.After the addition of NMP promoter,the optimum crystallinity can be achieved for 6¹2h and the crystallinity decreases with prolonging the crystallization time.The optimal catalytic performance of TS-1 was obtained at n?NMP?:n?SiO₂?=0.005,with X_H2O2 and U _H2O2 about95%.At the same time,with the assist of NMP promoter,the crystallinity and yield of TS-1remains well even reducing the template from n?TPAOH?:n?SiO₂?=0.25 to 0.125.2.TS-1 was prepared by hydrothermal crystallization in 6 hours after adding NMP etc.to the synthetic gel at a low templating dosage?n?TPAOH?:n?SiO₂?=0.125?.The effects of amount and types of the additives on the synthesis and catalytic performance of TS-1were investigated.When reducing the dosage of template TPAOH,higher TS-1 yield could be achieved by adding acetamide,caprolactam,DMF,polyvinyl pyrrolidone or NMP.The catalytic performance of TS-1 synthesized adding caprolactam and NMP was optimal,with X_H2O2,S_PO and U_H2O2 exceeding 95%.