高稳定性层柱粘土分子筛的催化性能

本文用酸碱滴定和红外光谱等方法对新型多孔材料——高稳定性层柱粘土分子筛(简称AlR)的表面酸性,催化活性和选择性进行了测定和研究,发现AlR的催化特性与HY和U8Y沸石有明显差别。根据实验研究,可以推测,AlR这种新型催化剂材料适用于有效酸强度较弱的大分子酸催化反应。

ATALYTIC PERFORMANCE OF PILLARED INTERLAYERED CLAY MOLECULAR SIEVE WITH HIGH THERMAL STABILITY

The surface acidity of a kind of pillared interlayered clay molecular sieve with high thermal and hydrothermal stabilities (AIR)has been studied using titration and IR methods, and the experimental data obtained have been compared with that of HY and USY zeolites The acid site density of A1R amounts to about 0.45 mmoleg~(-1), which is 4—5 times less than that of HY and USY zeolites. There are two maximums on the acid strength distribution curve of A1R corresponding to two types of acid sites with medium (H_0=-3.0-0.8) and weak (H_0=3.3-4.8) acid strengths. In comparison with AIR, HY has more acid sites with medium acid strength and USY has additional acid sites with strong acid strength (H_0<-5.6). IR pyridine adsorption spectra of AIR show that the acid sites on AIR are mainly Lewis acid sites from the alumina pillars.The catalytic behavior of pillared interlayered clay molecular sieve was compared with those of HY and USY zeolites. For acid-catalyzed reactions such as dehydration of isopropanol and conversion of cyclohexene, in which acid sites with wask and medium acid strengths take the part of active sites, the activities of AIR are lower than that of HY and USY. For cracking of cumene and decalin which are known as reactions catalyzed by strong acid sites the activities ofAIR arealmost negligible. The activity of AIR towards dealkylation of bulky molecules as 1,3,5-tri-tert-butylbenzene (0.94 nm) increases sharply and becomes comparable with HY and USY, and the product distributions of the three catalysts are different. This increase in activity and change in selectivity are unigue to pillared interlayered clay molecular sieves.