Shape selectivity conversion of biomass derived glycerol to aromatics over hierarchical HZSM-5 zeolites prepared by successive steaming and alkaline leaching: Impact of acid properties and pore constraint

Abstract

The selective production of light aromatics starting from biomass derived glycerol provides excellent prospect in reducing dependency on fossil resources and carbon dioxide emissions. The catalytic perfomances in glycerol to aromatics (GTA) procedure were systematically investigated for HZSM-5 catalysts with various porosity and acidic property, which were prepared by separate or multi-step treatments using NaOH and steaming on HZSM-5 zeolites. A consecutive steaming-alkali treatment of HZSM-5 zeolite enables the introduction of higher amounts of intra-mesoporosity with smaller-aperture (mainly at the range of 2–4 nm), which could be ascribed to the easier extraction of Si species in steaming treated HZSM-5 interior than that in steaming treated HZSM-5 outer surface. However, the combination of alkali-steaming treatment of HZSM-5 zeolite leads to a remarkable collapsion in the generated micro-mesopore hierarchical structure. Both the GTA reaction and coking process were varied with the HZSM-5 catalyst prepared by different post treatment means. Among all catalysts, 3 h 450 °C/0.3 M NaOH/HZSM-5 catalyst exhibited the highest BTX aroamtics yield, lowest coking rate and longest catalyst lifetime, which could be ascribed to the synergistic effect between the shape selectivity of micropores and size confinement of mesopores coupling with moderate acidity distribution in HZSM-5 crystals interior and surface for GTA process.