Skeletal Isomerization of n-Butenes on Zeolite Catalysts: Effects of Acidity

Abstract

ZSM-5 and ZSM-11 zeolites with different contents of aluminum and boron have been synthesized to control their acidity. Results of catalytic studies suggest that there are synergistic effects between framework boron and aluminum to enhance skeletal isomerization activity. In the absence of boron, the competitive reactions like oligomerization, cracking, and H-transfer will dominate, which produce undesired products. In the absence of aluminum, the isomerization activity is low. Incorporation of boron into the framework of aluminum zeolites can reduce the acidity. Consequently, the isomerization activity increases, and the activity of oligomerization, cracking, and H-transfer reaction decrease to some extent. Alumina binder also has effects on boron zeolites because of the migration of aluminum into the framework.