Deactivation by fouling and/or poisoning of micro-mesoporous “hierarchical” solid Brønsted acid zeolite catalysts during upgrading of bulky (poly)aromatic hydrocarbons poses limitations on selectivity to desired bulky products, maximum conversions, and single-pass catalyst lifetimes, particularly under severely diffusion-constrained systems, like liquid-phase or plastic upcycling reactions. The wide variety of bottom-up (synthetic) and top-down (post-synthetic) mesopore incorporation methods into conventionally microporous zeolites necessitates study of the morphological and active site distribution impacts on the location and extent of buildup for water, low molecular weight organics, coke precursors, and coke within spent catalysts. Here, we use thermogravimetric analysis, mass spectrometry, transmission electron microscopy, and N2 physisorption to characterize spent and fresh catalysts employed for the liquid-phase alkylation of 1,3,5-trimethylbenzene (TMB) with benzyl alcohol (BA) ([TMB]0/[BA]0 = 35) to form 1,3,5-trimethyl-2-benzylbenzene (TM2B), a reaction that competes with the self-etherification of benzyl alcohol to form dibenzyl ether (DBE) and the secondary formation of TM2B and BA from DBE and TMB. We found that, despite morphological nuances among parent and hierarchical zeolites of varying pore size distributions and dimensionalities, overarching collapsible trends in water and organic buildup exist as functions of surface area, mesopore volume, and extent of reaction.

Insights into (hierarchical) zeolite deactivation during conversions of bulky organics

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