SO_4^（2－）／ZrO_2超强酸催化剂的XPS研究

XPS STUDY OF SULFATE ION PROMOTED ZIRCONIUM OXIDE SUPERACID CATALYST

用ＸＰＳ技术对不同焙烧温度、不同Ｈ＿２ＳＯ＿４浓度制得的／ＺｒＯ＿２和不同反应温度下反应后／ＺｒＯ＿２超强酸催化剂的表面元素电子结合能及表面元素的相对含量进行了分析。结果表明，焙烧温度和反应温度对催化剂表面元素Ｚｒ、Ｏ和Ｓ的氧化态没有影响，但Ｚｒ和Ｏ的电子结合能随温度的升高而下降；Ｏ（－２）至少可归结为三种存在形式的氧；可以在催化剂表面富集，且当Ｈ＿２ＳＯ＿４浓度为０．５ｍｏｌ／Ｌ时，表面富集最显著；Ｈ＿２ＳＯ＿４浓度为１ｍｏｌ／Ｌ时，催化剂表面和总体含硫量都较高；太低和太高的Ｈ＿２ＳＯ＿４浓度时，催化剂表面和总体含硫量都很低。当焙烧温度高至８５３Ｋ或反应温度高至６２３Ｋ以后，催化剂表面含硫量迅速下降。此外，还对催化剂表面的Ｂｒｏｎｓｔｅｄ酸中心的存在形式和催化剂的失活进行了探讨。

The binding energy and relative content of surface elements of cal-cined and used at different temperatures were analysed by XPS.It was found that the oxid-ing states of Zr,O and S did not change with calcination and reaction temperatures, but thebinding energy of Zr and O decreased with increasing calcination and reaction temperatures. The oxide ion O(-2) exists at least in three forms:ZrO_2,and -OH. Sulfate ion is en-riched on the surface of catalyst,and the enrichment is maximum when H_2SO_4 is 0.5 mol/L. When H_2SO_4 is 1 mol/L,both the surface and bulk sulfur contents are high.The surface sul-fur content of catalyst after reaction decreased rapidly when the reaction temperature is high-er than 623K. In addition,a probable structure of Bronsted site for catalyst wasalso proposed.