Solid-state transformation of hollow silica microspheres into hierarchical ZSM-5 having tunable mesopores

Mesoporous hierarchical ZSM-5 zeolites have been prepared via direct solid-state transformation of hollow silica gel microspheres without changing their spherical geometry. A two-stage hydrothermal method was used where tetrapropylammonium (TPA+) directed the formation of the MFI subunits in the first stage. In the second stage these subunits aggregated around the self-assembled cetyltrimethylammonium micelles and then crystallized by TPA+ templation. The mesoporous structure proved to be tunable in the pore size range of 3.2–4.8 nm by the addition of swelling agent 1,3,5-trimethylbenzene. Catalytic propene oligomerization showed less coke formed over mesoporous than microporous ZSM-5 catalysts.