Effects of in-situ chemical vapour deposition using tetraethoxysilane on the catalytic and sorption properties of ZSM-5

Abstract

The external surface of HZSM-5 crystals was gradually modified by in-situ CVD of tetraethoxysilane. Using the particular procedures described in the paper, it was shown from probe reactions in combination with sorption studies that the external surface was deactivated and the pore-opening size was reduced while the intracrystalline pore space remained unmodified. The positive effect of the CVD treatment procedure on the shape selective properties of HZSM-5 was demonstrated by an enhancement in p-selectivity during toluene disproportionation. The paper discusses the relation between the effects of the CVD treatment procedure on catalytic properties, sorption properties and structural properties and conclusions are made on the use of the conversion of 1,2,4-trimethylbenzene, 1,3,5-triisopropylbenzene, toluene and n-hexane, respectively, to probe the effects of external surface modifications on properties of ZSM-5.