Effect of heat treatment on the catalytic activity and selectivity of action of high-silica zeolites in transformations of xylenes

1.In studying the isomerization and disproportionation of xylenes, the temperature range of the formation and destruction of active centers in zeolites of the pentasil and mordenite type was established. Active centers resistant to heat treatment at 973–1073 K are present on the surface of zeolites prepared by direct synthesis.2.After treatment of zeolite of the pentasil type with air at 1073–1273 K, the selectivity with respect to formation of p-xylene increased significantly, and the reaction of disproportionation of the xylenes with a decrease in the total catalytic activity was inhibited.