新型WO3/HMS催化剂的制备及其对环戊烯选择氧化反应的催化性能

 采用草酸络合方法将WO3固载到六方介孔全硅分子筛HMS上,制得新型WO3/HMS非均相催化剂. 利用SEM,TEM,N2吸附,XRD及激光拉曼光谱等手段对催化剂进行了表征,研究了催化剂在环戊烯选择性氧化合成戊二醛反应中的催化性能. 结果表明,在WO3/HMS催化下环戊烯和H2O2的转化率均可达100%,戊二醛的选择性可达72%. WO3以高分散状态存在于催化剂表面. 单次反应后钨的溶脱量(5.5 μg/ml)很小,对反应几乎没有影响. 催化剂具有较高的稳定性,可以重复套用6次. 失活后的催化剂可通过简单焙烧的方式再生.

Preparation of Novel WO3/HMS Catalyst and Its Catalytic Performance for the Selective Oxidation of Cyclopentene

The novel heterogeneous WO_3/HMS catalyst was prepared by immobilization of tungstic acid on hexagonal mesoporous silica (HMS) by a special method using oxalic acid as the complexing agent, and was characterized by means of SEM, TEM, N_2 adsorption, XRD and laser Raman spectroscopy. The influences of Si/W molar ratio on the catalytic performance of WO_3/HMS, WO_3/SiO_2 and WO_3/MCM-41 for the selective oxidation of cyclopentene to glutaraldehyde under mild conditions were investigated. The as-prepared WO_3/HMS catalyst with a Si/W molar ratio of 30 showed excellent catalytic activity and selectivity. The conversions of both cyclopentene and H_2O_2 were near 100% and the selectivity for glutaraldehyde reached 72%, which are much higher than those over the WO_3/SiO_2 catalyst and even exceed those over the homogeneous tungstic acid catalyst. The WO_3/HMS catalyst remained similar morphology and hexagonal mesoporous structure as pure HMS. The highly dispersed WO_3 on the HMS surface was identified as the active phase of the catalyst. The leaching of the active species was very low and had little effect on the catalytic performance. In addition, the WO_3/HMS catalyst was very stable and could be reused for at least six times. The deactivated catalyst could be regenerated by simple calcination.