ACTIVITY STABILIZATION OF GA-MFI ZEOLITE CATALYST MODIFIED BY CHEMICAL-VAPOR-DEPOSITION

The chemical vapor deposition of silica on Ga-MFI zeolite was carried out using tetraethyl orthosilicate. The enhancement in para selectivit y during toluene alkylation with the extent of silica deposition was c losely monitored. The effect of reaction temperature on the behavior o f silica deposited Ga-MFI zeolite was established. A deactivation tren d in toluene conversion was observed when the zeolite was employed for alkylation for longer periods. The reasons for catalytic deactivation and stability enhancement by in situ coking are discussed.