氧化铝表面钛改性的机理分析

用钛对氧化铝表面进行改性，制备了不同钛含量的钛改性氧化铝载体；通过透射电镜(TEM)、X射线衍射(XRD)、X射线荧光（XRF）等方法表征了氧化钛在氧化铝载体表面的状态；通过傅里叶变换红外吸收光谱（FT-IR）研究了钛改性后氧化铝载体表面羟基的变化。结果表明：钛均匀负载在氧化铝表面；波数在3 725 cm-1处的红外振动吸收峰是氧化铝载体表面弱酸性的四面体-八面体桥连羟基，当钛负载时，钛优先取代该桥连羟基上的氢离子，而后逐渐取代其它羟基上的氢；钛改性对波数在1 000~2 000 cm-1范围内氧化铝的中强L酸位和弱L酸位也有一定影响。

MECHANISM ANALYSIS OF Ti-MODIFIED ALUMINA SUPPORT

A series of Ti-modified alumina samples having various TiO2 contents was prepared.The dispersion state of TiO2 on the alumina support was characterized by TEM,XRD and XRF.Furthermore,the effect of TiO2 on the surface hydroxyl groups of alumina support was studied by FT-IR.Results show that Ti species is dispersed on the alumina surface uniformly.The IR absorption peak of alumina at wave number of 3 725 cm-1 is related to weak acidic hydroxyl group bridged with octahedral Al3+ and tetrahedral Al3+,with the loading of TiO2,the H+ of this bridged hydroxyl is substituted by Ti species firstly,followed by substituting H+ of other hydroxyl groups gradually.It can be seen that in wave number range of 1 000—2 000 cm-1 the related medium strong and weak Lewis acid sites of alumina are affected by Ti-modification in certain aspect.