Tailoring the impact of synthetic strategies on the catalytic upgrading of crude glycerol to produce bio-based aromatics in hierarchical HZSM-5

Abstract

The catalytic upgrading of renewable biomass derived crude glycerol to generate bio-based aromatics is a promising alternative to petroleum route for the synthesis of valuable and versatile aromatics. The effects of synthetic strategies on the physicochemical property of hierarchical HZSM-5 as well as their corresponding catalytic upgrading performances of crude glycerol to bio-based aromatics were systematically investigated in this work. HZSM-5/0.3M NaOH catalyst exhibited smaller improvement in aromatic yields than microporous HZSM-5, which could be ascribed to the uncontrollable large intra-mesopore diameter and less increment in the amounts of acid sites during the introduction of mesoporosity via destructive alkali treatment. The soft templated HZSM-5/TPOAC catalyst produced more BTX and C9+ monocyclic aromatics, which could be attributed to its larger crystal sizes, higher external surfaces, luxuriant L acid amounts, uniform and small mesopore sizes. However, the hard templated HZSM-5/CNT-OH catalyst exhibited higher yields of polycyclic aromatic hydrocarbons and coke during the crude glycerol upgrading process, which could be assigned to its smaller crystal sizes, abundant B acid quantities, uniform and large mesopore diameters. The reusability of desilicated HZSM-5/0.3M NaOH was also deteriorated than the templated HZSM-5/CNT-OH and HZSM-5/TPOAC due to the inferior stability of incorporated mesoporosity via desilication. Finally, plausible reaction pathway involved catalytic upgrading of crude glycerol to produce aromatics was proposed in detail.