Catalytic upgradation of crude glycerol to produce bio-based aromatics over hierarchical MFI zeolite: Effect of bimodal hierarchical porosity enhancement and porosity-acidity interaction

Abstract

The transformation of renewable biomass derived crude glycerol into value-added BTX aromatics is an attractive approach to facilitate carbon neutrality and recycling economy. Herein, two kinds of hierarchical HZSM-5 with distinct hierarchical porosity and acidity distribution were synthesized based on a seed-induced method by utilizing CTAB and TPOAC as soft mesoporogens, respectively. And the effects of bimodal hierarchical porosity and porosity-acidity interaction on the upgradation efficiency during the conversion of crude glycerol over hierarchical HZSM-5 were investigated. The abundant intra-mesopores and promoted porosity-acidity interaction in hierarchical HZSM-5 facilitated the transformation of macromolecules in crude glycerol into small oxygenated chemicals and olefins, resulting in higher BTX yield and longer catalyst lifetime. Among all catalysts, the hierarchical HZSM-5 sample templated with TPOAC exhibited the maximum carbon yields of BTX (38.5%) and longest lifetime (23 h) due to the better interconnectivity of shape-selective micropores and high mass transfer intra-mesopores. The reaction route and product distribution of upgradation of crude glycerol was strongly dependent on the morphology, bimodal hierarchical porosity and acidity variation resulting from the generation of intra-mesopores in HZSM-5 catalysts by the usage of different soft mesoporogens. The liquid route and side alkylation reaction was accelerated over HZSM-5/TPOAC catalyst while the gas route and secondary coking reaction was promoted over HZSM-5/CTAB sample.