SBA-15介孔分子筛担载的钒基氧化物催化剂对乙烷选择氧化性能

Selective Oxidation of Ethane over SBA-15 Mesoporous Zeolite Supported Vanadium-Based Oxide Catalysts

用等体积浸渍法制备了SBA-15担载的钒基(V/SBA-15)和钾修饰的钒基氧化物(K-V/SBA-15)催化剂,使用氮气吸附、小角X射线衍射(XRD)、紫外-可见漫反射光谱(UV-Vis DRS)和紫外激光拉曼光谱对这些催化剂的结构进行表征,并评价了这些催化剂对乙烷选择氧化的活性与选择性.实验结果表明介孔结构SBA-15对乙烷选择氧化的活性优于常规的SiO2;对于SBA-15担载的V/SBA-15和K-V/SBA-15催化剂,极低钒担载量(nV∶nSi≤0.1∶100)时隔离的四配位钒氧化物是乙烷选择氧化生成醛类化合物的活性物种,高钒担载量(nV∶nSi≥2.5∶100)时聚合的和微晶态的钒氧化物是乙烷氧化脱氢或深度氧化的活性物种.

A series of SBA-15 supported vanadium oxide（V/SBA-15） and K-modified vanadium oxide（K-V/SBA-15） catalysts with different active components were prepared by incipient-wetness impregnation.The structures of the catalysts were characterized using N2 adsorption,low angle X-ray diffraction（XRD）,UV-Vis diffuse reflectance spectroscopy（UV-Vis DRS） and UV-Raman spectroscopy techniques.Their catalytic performances for the selective oxidation of ethane were also investigated.The results showed that SBA-15 was a better support for the catalyst system than SiO2 for the selective oxidation of ethane to aldehydes.The SBA-15-supported low loading catalyst was a highly dispersed catalyst system and the SBA-15 supported K-V samples with low loading（nV∶nSi≤5.0∶100） had ordered hexagonal mesostructures.For the V/SBA-15 and K-V/SBA-15 catalysts,isolated vanadyl species with tetrahedral coordination are determined to be the active sites for aldehyde formation at very low vanadium loading（nV∶nSi≤0.1∶ 100）.The polymeric vanadyl species with octahedral coordination and the microcrystalline vanadium oxide constitute the active sites for the oxidative dehydrogenation or deep oxidation of ethane when the loading of vanadium is higher than 2.5∶100.