离子液体功能化有序介孔SBA-15孔壁定域化磷钨酸催化活性中心构建及其催化性能

采用溶胶-凝胶法合成了一种桥键嵌入型双咪唑离子液体功能化介孔硅基材料(Bis-PImBr-PMO-SBA-15),然后离子交换将Keggin型磷钨酸负载于其上,制备了PW-Bis-PImBr-PMO-SBA-15催化剂,并运用X射线衍射、N2吸附-脱附、透射电子显微镜、傅里叶变换红外光谱和热重分析等手段对其进行表征.结果表明,该催化剂具有SBA-15分子筛的有序六方孔道结构,且负载后的磷钨酸阴离子仍保持其完整的Keggin结构.在以水为溶剂,30%H2O2为氧化剂的苯甲醇氧化反应中,该催化剂表现出比均相的或负载于SBA-15表面的Keggin型HPW更高的催化活性,苯甲醇转化率和苯甲醛选择性分别可达95%和94%.离子液体的咪唑阳离子可调节磷钨酸阴离子的氧化-还原性能,从而有利于提高催化剂的催化活性..

Preparation and Catalytic Performance of Phosphotungstic Acid Active Sites Supported on Periodic Mesoporous Organosilica of SBA-15

A functionalized periodic mesoporous organosilica(PMO),Bis-PImBr-PMO-SBA-15,incorporated with bridging bis-imidazolium ionic liquid moieties was synthesized via a sol-gel procedure.Keggin-type 12-phosphotungstic acid(H3PW12O40? xH2O) was immobilized onto Bis-PImBr-PMO-SBA-15 by the way of anion-exchange,which provided the mesoporous organosilica-supported Keggin-type 12-tungstophosphate catalyst(PW-Bis-PImBr-PMO-SBA-15).X-ray diffraction,N2 adsorption-desorption,transmission electron microscopy,Fourier transform infrared spectroscopy,and thermal analysis results showed that both Bis-PImBr-PMO-SBA-15 and PW-Bis-PImBr-PMO-SBA-15 maintained the typical characteristics of the mesoporous material,and the Keggin-structure of the 12-phosphotungstate anion was intact after immobilization.The catalytic performance of PW-Bis-PImBr-PMO-SBA-15 in the selective oxidation of benzyl alcohol by 30% H2O2 was investigated.The PW-Bis-PImBr-PMO-SBA-15 showed higher catalytic activity than bulk HPW or siliceous SBA-15-supported Keggin-type 12-tungstophosphate catalyst(HPW/SBA-15),the conversion of benzyl alcohol and the selectivity to benzaldehyde were as high as 95% and 94%,respectively.The bis-imidazolium cations were thought to mediate the redox behavior of the Keggin PW12 anions,which in turns enhanced the activity and stability of the catalyst.