Activity and basicity of BaO modified zeolite and zeolite-type catalysts

BaO modified zeolite and zeolite-type catalysts provide new and valuable data about the alternative reaction for ethylbenzene and styrene formation-the oxidative methylation of toluene with methane. Over BaO modified X, Y, mordenite, ZSM-5, silicalite and AIPO(4)-5 catalysts, the toluene conversion, selectivity and yield of C-8 hydrocarbons (ethylbenzene and styrene) are affected to a different degree by the reaction temperature. Both activity and basicity (measured by TPD Of CO2) are resultant from the combined effect of chemical composition and geometry of zeolite and zeolite-type structures, as well as from the accessibility of BaO modifier to the reagents. The Si/Al atomic ratio determines the catalytic and basic properties within a series of the same structural type. The zeolite and zeolite-type structural geometry determines the accessibility of the introduced BaO. Higher accessibility of BaO used for modification favors the activity. Basicity measurements by X-ray photoelectron spectroscopy (XPS) are mainly sensitive towards the chemical composition of the zeolite and zeolite-type framework. (C) 2002 Elsevier Science B.V. All rights reserved.