| 内容提要: |
A density functional theory (DFT) study has been conducted to investigate the structural and electronic properties of TiO2/USY and thereby the relationship between the adsorption site of TiO2, the acidity and the reactivity of TiO2/USY. The study shows that the titanium atom is four-coordinated with oxygen atoms, two of which belong to framework of zeolite. The H proton transfers from zeolite to oxygen atom of TiO2 during the modification process, and lead to a decrease in acidity of TiO2/USY. The analysis of the Mulliken population shows that there exists a charge transfer between TiO2 and zeolite. Therefore, the interaction between zeolite and the metal atom is increased. By comparing the acidity indicators of these TiO2/USY clusters, the modification of TiO2 decreases the acidity of USY and different adsorbed site has different acidity. The components of the frontier molecular orbital of these cluster models come mainly from the Ti and the oxygen atoms of zeolite. The DFT calculations confirm that there is a close relationship between the acidity and the reactivity of TiO2/USY. That is, the smaller the acidity, the stronger the reactivity. Therefore, the high active catalyst could be designed and developed by adjusting the acidity through changing the adsorption sites of TiO2 on USY. |