摘要
在XRD相定量分析的阈值时,MoO_3/TiO_2(锐钛矿)界面上,MoO_3和TiO_2都有一个单分子层左右的非晶相分散,当MoO_3在催化剂中的含量超过阈值时,则它的非晶相量将增加为该含量的(1—0.73)倍。在这个非晶相层中,主要是聚钼酸和少量的MoO_3集合体,TiO_2则是表面层结构的畸变,它们的红外特征是:Mo=O的伸缩振动由993cm^(-1)红移到960cm^(-1),MoO_3集合体的伸缩振动为828cm^(-1),未发现MoO_4^(-2)的伸缩振动(898cm^(-1)),766和603cm^(-1)是畸变的TiO_2表面层同含Mo物种形成的表面化学键的特征伸缩振动,这个表面化学键对邻二甲苯选择氧化有利。
The dispersion capacity of MoO3 and TiO2 at the interface of MoO3/ TiO2 calcined at 500℃ for 5 h was studied by XRD and FT-IR difference spectra. There is about one monolayer of non-crystalline phase of MoO3 and TiO2 at the interface. When MoO3 content is higher than the threshold value, the amount of non-crystalline phase of MoO3 increases to (1-0.73) times of MoO3 content. The predominant species in the layer of non-crystalline phase are polymolybdate, MoO3 cluster and the distorted crystal lattice of octahedral TiO6 of TiO2 .The stretching vibration of Mo = O of polymolybdate shifts to red from 993 to 960 cm-1, the stretching vibration of MoO3 cluster is found at 828 cm-1, and the stretching vibration of adsorbed Mo-O-Ti band is found at 766 and 603 cm-1. The formation of chemical bond between TiO2 and MoO3 at the interface is favorable to the selective oxidation of o-xylene.
基金
国家自然科学基金
