Renewable gasoline-range aromatics and hydrogen-enriched fuel gas from biomass via catalytic microwave-induced pyrolysis

Abstract

A novel pathway was investigated to produce gasoline-range aromatics and hydrogen-enriched fuel gas by microwave-induced pyrolysis of cellulose integrated with packed-bed catalysis in the presence of a solid phase catalyst. The employed catalyst was well-promoted ZSM-5 after the couplings of hydrothermal and calcined treatments, completely converting volatile vapors derived from microwave pyrolysis into aromatics and non-condensable gases. A central composite experimental design (CCD) was employed to investigate the effects of catalytic temperature and inverse weight hourly space velocity (WHSV)⁻¹ on the pyrolysis-oils composition. It was observed that the chemical compounds of the upgraded bio-oils from catalytic microwave pyrolysis of cellulose were aromatic hydrocarbons, phenols, and aromatic oxygenates. Aromatic hydrocarbons that accounted for the largest selectivity of these compounds were in the range from 82.93 to 96.60% in bio-oils depending on alterations of catalytic conditions. Up to 48.56% selectivity towards aromatics in the upgraded bio-oil belongs to gasoline-range aromatics under the mild conditions. The maximum selectivity of aromatic hydrocarbons (96.60%) was gained at a packed-bed temperature of 500 °C and a WHSV⁻¹ of 0.067 h. Gaseous results show that hydrogen was the dominant composition, occupying approximately 40 vol%. The high amounts of gasoline-range aromatics and valuable hydrogen are attributed to the technologies of microwave-assisted pyrolysis and ex situ catalysis. These findings from this study pave a new route for biorefinery industries to produce developed products (aromatics and hydrogen-rich gases) through microwave-induced technologies.