TAP Study of Adsorption and Diffusion of 2,2,4-Trimenthylpentane and 2,5-Dimethylhexane on β and USY Zeolites

Abstract

The dimensionless equilibrium constant, apparent heats of adsorption, intraparticle diffusivities, and activation energies are determined under high vacuum conditions for 2,2,4-trimethylpentane and 2,5-dimethylhexane. These are representative of the products formed in the alkylation process of isobutane–butene mixtures on solid acid catalysts such as β and USY zeolites. It is observed that in the straight and zigzag channels of β zeolites, dimethyl-branched C8 isoalkane is strongly adsorbed and diffuses at a slower rate in comparison to trimethyl-branched C8 isoalkane. In contrast, in the super cages of USY zeolites, both C8 isoalkanes demonstrate similar sorption and transport properties. On the basis of this understanding, it is concluded that the ideal solid acid catalyst for alkylation processes requires super cages of USY zeolite rather than zigzag channels of β-zeolites in order to increase product selectivity, decrease catalyst deactivation, and decrease the energy requirement for regeneration.