CERIUM IMPREGNATED H-MORDENITE AS A CATALYST FOR SHAPE-SELECTIVE ISOPROPYLATION OF NAPHTHALENE - SELECTIVE DEACTIVATION OF ACID SITES ON THE EXTERNAL SURFACE

The impregnation of cerium is the effective method for the deactivation of external acid sites of H-mordenite, The selectivity of 2,6-DIPN in the isopropylation of naphthalene was enhanced by the impregnation with such a large amount as 30-50 wt.-% of cerium without significant decrease of catalytic activity. The highest selectivity of 2,6-DIPN was achieved up to 70% over a highly dealuminated H-mordenite, (HM(128); SiO2/Al2O3 = 128), with 30 wt.-% of cerium. The enhancement of the selectivity is ascribed to the deactivation of external acid sites judging from the activity of the cracking reaction of 1,3,5-triisopropylbenzene. The effective pore radius was not reduced by the modification. The ceria is highly dispersed only on the external surface of H-mordenite without any formation of new kinds of acid sites. The Xe-129 NMR observation suggests that cerium is not in the pores, but on the external surfaces. The deactivation of the external acid sites is a characteristic property for cerium. Lanthanum and neodymium inhibited catalytic activity of the isopropylation because the pores were narrowed by their impregnation. A possible reason of the deactivation is ascribed to the amphoteric property of ceria.