Effect of zeolite structure and morphology on intracrystalline n-hexane diffusion in pentasil zeolites studied by the zero-length column method

Abstract

n-Hexane diffusion in ferrierite and silicalite-1, two molecular sieves belonging to the pentasil family, has been studied. The zero-length column method has been applied. Large, well shaped crystals were synthesised and used. For silicalite-1, the effect of macroscopic twinning has been verified by determining n-hexane diffusivities in ‘twinned’ and in single silicalite-1 crystals. It was found that ‘twinning’ has no effect on the transport diffusivity of n-hexane in silicalite-1. This is in accordance with structural data on ‘twinned’ MFI frameworks, presented in literature. The n-hexane diffusion in ferrierite is four orders of magnitude smaller than that in silicalite-1. This is proposed to be a consequence of structure faulting.