Effects of support on bifunctional methanol oxidation pathways catalyzed by polyoxometallate Keggin clusters
作者:H Liu
DOI:10.1016/j.jcat.2004.01.012
日期:2004.4.1
polyoxometallate clusters and supports. Rates of CH3OH oxidative dehydrogenation per KU were higher on ZrO2 and TiO2 than on SiO2 at similar KU surface densities (0.28–0.37 KU/nm2) and dispersion, indicating that redox properties of Keggin clusters depend on the identity of the support used to disperse them. ZrO2 and TiO2 supports appear to enhance the reducibility of anchored polyoxometallate clusters. Rates
负载在ZrO 2,TiO 2,SiO 2和Al 2 O 3上的H 5 PV 2 Mo 10 O 40多金属氧酸盐Keggin团簇是CH 3 OH氧化反应形成HCHO,甲酸甲酯(MF)和二甲氧基甲烷(DMM)的有效催化剂)。负载簇的速率和选择性以及结构取决于氧化物载体的表面性质。拉曼光谱表明,在553 K的空气中处理后,Keggin结构在ZrO 2,TiO 2和SiO 2上基本上保持完整,但分解为MoO x和Al 2 O 3上的VO x低聚物。在CH 3 OH氧化过程中,通过用2,6-二叔丁基吡啶进行滴定,测量了每个Keggin单位(KU)的可接近质子。对于相似的KU表面密度(0.28–0.37 KU / nm 2),即使残留的二甲醚(DME),SiO 2上可及的质子数也大于ZrO 2和TiO 2上的质子数,而Al 2 O 3载体上的可质子数要少得多。滴定剂饱和后的合成速率表明,KU的分数分散在前三个载体上相似。支撑物对结构和H