SO_4^(2-)/ZrO_2-SiO_2催化剂的酸性及结构表征

Characterization of Structure and Acidity of Catalyst SO 4 2- /ZrO 2 SiO 2

采用指示剂法及吸附吡啶的红外光谱法，考察了催化剂的酸性；用ＸＲＤ、ＩＲ、ＸＰＳ及热分析等对催化剂的结构进行了表征；用ＢＥＴ法测定了催化剂的比表面积，并研究了催化剂的组成及焙烧温度对催化剂比表面积的影响．实验结果表明，一般在４５０℃以上焙烧的ＳＯ４２－／ＺｒＯ２ＳｉＯ２催化剂均具有超强酸性，催化剂的酸强度随焙烧温度的增高有所增强；吸附吡啶的红外光谱表明该催化剂具有较高的Ｌｅｗｉｓ酸量．通常８００℃以下焙烧的催化剂均为非晶态，高于８００℃焙烧硅锆比大于９的样品时，可得到一种新的结晶态物质．催化剂的比表面积一般在４００ｍ２／ｇ左右．

The acidity of catalyst SO 4 2- /ZrO 2 SiO 2 was investigated by indicator method and IR spectra of pyridine adsorbed on catalyst. The structure of catalyst is characterized by XRD、IR、XPS and thermal analysis method. The specific surface area of catalyst is measured by BET method and the effects of composition and calcining temperature on the surface area were investieated. The experimental results show that the catalysts have superacid property when calcined above 450℃; the acid strength of catalyst is increased with the increase of calcining temperature. The IR spectra of pyridine absorbed on catalyst surface show that the SO 4 2- /ZrO 2 SiO 2 catalysts contain much more Lewis acid centers than catalyst SO 4 2- /ZrO 2. The catalysts containing SiO 2 usually exist in non crystalline state when calcined below 800℃, but when calcined above 800℃, they change into two types of crystalline forms according to the ratio of Zr to Si atoms. The specific surface area of catalyst is generally about 400 m 2/g.