The influence of pore-architecture over n-heptane cracking using MFI, *BEA and MSE zeolite catalysts: Multipore versus hierarchical porosity

Abstract

The catalytic properties of zeolitic materials are governed by the intricate interplay between catalytic and transport processes, which, in turn, depend critically on the topology and morphology features. Here, the catalytic performance of typical three dimensional zeolites, including medium pore MFI, large pore *BEA and multi-pore MSE topologies with comparable Si/Al ratios are employed as n-heptane cracking catalysts to inspect the influence of topology on product slates for naphtha molecules. Furthermore, a bead-milling coupled with porogen assisted recrystallization method is used to fabricate hierarchically porous MSE zeolite for the first time. The catalytic n-heptane cracking properties of hierarchical MSE zeolite are compared with the hierarchical MFI and *BEA analogues, derived from the cracking mechanism ratio and the hydrogen transfer coefficient, respectively, to exam the influence of transport on product distributions. Multi-pore MSE zeolite outperforms MFI and *BEA zeolites in terms of light olefin selectivity and yield, owing to an exaggerated contribution from Haag-Dessau mechanism mediated cracking and a reduced probability for side-reactions, as a consequence of decreased residence time for the primary cracking product olefins. The developed methods to fabricated hierarchical zeolites and the revelation of structure-catalysis relationship may inspire future catalyst design for catalytic naphtha cracking.