ZSM-5沸石上Brönsted酸的红外光谱测定法及改性ZSM-5沸石的表面酸性研究

研究各种 ZSM-5沸石样品的红外光谱发现: 在1875和2000 cm~(-1)附近有两个强红外吸收谱带, 两个谱带吸光度的比值是个特征值。本文提出了以2000 cm~(-1)谱带为“内标”, 用相对吸光度的办法处理ZSM-5沸石的红外光谱, 测定了各种改性ZSM-5样品的Brönsted酸, 并同电位滴定法所测得的Brönsted 酸浓度和异丙苯裂解活性分别关联, 都有较好的对应关系。文中以实验为依据讨论了1875和2000 cm~(-1)谱带的归属, 并根据Beer-Lambert定律, 推导出了相对吸光度与浓度的关系, 从而确立了ZSM-5沸石上红外光谱定量处理方法的理论基础。

AN INFRARED SPECTROSCOPY METHOD FOR MEASURING THE BRÖNSTED ACID OF ZSM-5 AND THE STUDY OF SURFACE ACIDITY OF MODIFIED ZSM-5 ZEOLITES

Based on the studies of IR Spectra of various ZSM-5 zeolites it was found that there are two strong bands at ca. 1875 and 2000 cm~(-1) and their absorbance ratio is a characteristic value. A method to treat the data of IR spectra by using relative absorbance with 2000 cm~(-1) band as a “internal standard” has been develo- ped. The acidity of various ZSM-5 samples has been determined by this method and related to their concentrations of Brönsted acid measured by potential titration and activity of cumeue cracking. Good relationships have been found. The assignment of 1875 cm~(-1) and 2000 cm~(-1) bands has been discussed according to the experimental results. The theoretical base of this quantitive method for treating the IR spectra of ZSM-5 zeolite has been found by inferring the relation between relative absorbance and the concentration by the Beer-Lambert law.