Insertion of aluminium into high-silica-content zeolite frameworks. Part 3.—Hydrothermal transfer of aluminium from Al2O3 into [Al]ZSM-5 and [B]ZSM-5

Abstract

High-silica ZSM-5 and [B]ZSM-5 (both containing ca. 600 ppm Al) are catalytically activated by hydrothermal treatment in the presence of alumina. Aluminium is transported as an aquo-species from Al₂O₃ into the zeolite and enters the framework in the tetrahedral conformation. The presence of framework B induces enhanced activation, the degree of activation increasing with B content. This is due to the hydrolytic instability of framework B and hence its ready substitution by Al.