DISPERSION STATE OF ZINC OXIDE ON SURFACE OF SILICA GEL AND SURFACE ACIDITY OF ZnO/SiO₂

【摘要】 <正> The dispersion threshold level of zinc oxide on silica gel was determined by X-ray quantitative phase analysis. And the results of XPS experiments show that the surface of the sample is enriched with ZnO and there is a limit for the ZnO amount dispersed on the surface. The value of this limit is corresponding with the threshold level obtained by XRD. The measurements of surfaee acidity show that there are some stronger acid sites on the surface of ZnO/SiO₂, they have not been found on the ZnO or SiO₂ individually, and the total amount of acid increases remarkably. The acidity depends on the ZnO concentration in the surface phase and reaches the maximum at the threshold value.In this paper, we propose a new point of view for the origin of the acidity on surface of the ZnO/SiO₂ samples. ZnO is well dispersed on the surface of SiO₂ gel in a monolayer state. In this situation, some new surface structure units emerge as a result of interaction between dispersed ZnO and the carrier, which are responsible更多还原

【Abstract】 The dispersion threshold level of zinc oxide on silica gel was determined by X-ray quantitative phase analysis. And the results of XPS experiments show that the surface of the sample is enriched with ZnO and there is a limit for the ZnO amount dispersed on the surface. The value of this limit is corresponding with the threshold level obtained by XRD. The measurements of surfaee acidity show that there are some stronger acid sites on the surface of ZnO/SiO₂, they have not been found on the ZnO or SiO₂ individually, and the total amount of acid increases remarkably. The acidity depends on the ZnO concentration in the surface phase and reaches the maximum at the threshold value.In this paper, we propose a new point of view for the origin of the acidity on surface of the ZnO/SiO₂ samples. ZnO is well dispersed on the surface of SiO₂ gel in a monolayer state. In this situation, some new surface structure units emerge as a result of interaction between dispersed ZnO and the carrier, which are responsible for the acidity of the surfaces of samples.更多还原