Preferred sites for the isomoprhous substituted for boron in ZSM-5 zeolite structure

Abstract

he semiempirical quantum chemical MNDO (modified neglect of diatomic overlap) technique is adopted to calculate the substitution energy for boron at different possible framework sites in the ZSM-5 zeolite structure. The topological analysis of the preferred boron substitution site indicates that boron in present in the 10-member ring of the straight and sinusoidal channel. The relative strengths of different acid sites in boron-substituted ZSM-5 are evaluated from the calculated proton affinity values. We have attempted to correlate the substitution energy and proton binding energy to acidic and catalytic properties observed for BZSM-5.