正硅酸四乙酯(TEOS)水解行为对TS-1分子筛钛物种分布的影响

Effect of hydrolysis of tetraethyl orthosilicate(TEOS) on titanium distribution of TS-1 zeolite

采用FT-IR技术跟踪正硅酸四乙酯(TEOS)水解过程并结合XRF、UV-vis等表征探讨了水解时间对TS-1分子筛中钛物种分布的影响。以1-己烯环氧化为模型反应对TS-1分子筛的催化氧化性能进行了评价。结果表明,TEOS适度水解能有效抑制非骨架钛形成,提高骨架钛含量,而水解时间较短或过长均不利于钛进入骨架,并会明显降低TS-1分子筛的催化性能。TEOS水解2 h后制得的TS-1分子筛具有最佳的1-己烯环氧化催化性能,在常压60℃反应条件下1-己烯转化率可达到37.5%,产物1,2-环氧己烷选择性可维持在85%左右,这一结果对费托烯烃环氧化催化剂的开发具有指导作用。

The hydrolysis process of tetraethyl orthosilicate(TEOS) was tracked by FT-IR analysis,and the effect of hydrolysis time on the distribution of titanium species in TS-1 zeolites was discussed through XRF and UV-Vis.The catalytic oxidation performance of TS-1 zeolite was tested by 1-hexene epoxidation as a model reaction.The results show that moderate hydrolysis of tetraethyl orthosilicate can effectively inhibit the formation of extraframework Ti and increase the content of framework Ti.However,shorter or longer hydrolysis time is not conducive to the entry of titanium into the skeleton,and reduce the catalytic performance of TS-1 zeolites.TS-1 prepared with2 h TEOS hydrolysis time has the best catalytic performance for epoxidation of 1-hexene.Under the reaction conditions of atmospheric pressure and 60 ℃,the conversion of 1-hexene can reach 37.5% and the selectivity of1,2-epoxy hexane can maintain at about 85%,and the result has a guiding role for the development of olefin epoxidation catalyst.