介孔硅担载磷钨杂多酸催化剂的制备及其对环戊烯氧化反应的催化性能(英文)

Preparation of Heterogeneous Mesoporous Silica-Supported 12-Tungstophosphoric Acid Catalyst and Its Catalytic Performance for Cyclopentene Oxidation

采用离子交换法将Keggin型12-磷钨杂多酸负载到表面胺基化的介孔SBA-15分子筛上,并利用X射线衍射、N2吸附-脱附、傅里叶变换红外光谱、X射线光电子能谱和热重分析等手段对催化剂进行了表征.结果表明,所制备催化剂具有SBA-15分子筛的有序六方孔道结构,负载后的磷钨杂多酸的Keggin结构未遭到破坏.所制备催化剂对以过氧化氢为氧化剂的环戊烯氧化反应具有很高的催化活性,环戊烯转化率可达100%,戊二醛选择性可达81%.催化剂具有较高的稳定性,重复使用5次后,其催化活性没有明显下降.

Keggin-structured 12-tungstophosphoric acids were immobilized onto the surface of amine-modified mesoporous sieve SBA-15 as onium salts. All the catalyst materials were characterized by X-ray diffraction,N2 physisorption,Fourier transform infrared spectroscopy,thermal gravimetric analysis,and X-ray photoelectron spectroscopy for their structural integrity and physicochemical properties. Characteri-zation of the catalysts confirmed an ordered hexagonal mesostructure for SBA-15 and that the Keggin structure of the heteropolyanions on the amine-modified SBA-15 was preserved. The catalytic activities of the catalysts were evaluated for the liquid-phase oxidation of cyclopentene with 50% hydrogen peroxide as the oxidant in tert-butanol. A 100% conversion of cyclopentene and an 81% selectivity for glutaraldehyde were obtained and these were higher than that for the catalysts prepared by direct impregnation. The stability and reusability of the catalysts were studied and the catalysts could be reused at least five times,which indicates their excellent reusability. The influence of reaction temperature and reaction time was also investigated. In addition,a reaction mechanism was proposed.