Effect of the acid properties on the diffusion of C7 hydrocarbons in UL-ZSM-5 materials

In this study, a series of UL-MFI materials with different Si/Al ratios has been synthesized following a solid-state crystallization starting from amorphous wormhole-like mesostructured aluminosilicates. The acid properties of UL-MFI materials are varied by changing the content of aluminum as observed by FTIR spectra of adsorbed pyridine. The effect of the acid properties on the diffusion of C-7 hydrocarbons n-heptane and toluene in UL-MFI materials was further studied using the ZLC technique. As expected, the interaction with the acid sites causes a decrease in the diffusivities of both sorbates. The values of the activation energy of diffusion for both C-7 hydrocarbons in H-form UL-MFI materials are higher than those in Na-forms. The effect of the acid properties on the decrease of these values is more pronounced at high Si/Al ratio. (c) 2005 Published by Elsevier Inc.