Screening microwave susceptors for microwave-assisted pyrolysis of lignin: Comparison of product yield and chemical profile

摘要

Lignin was pyrolyzed with microwave heating in the presence of different microwave susceptors including silicon carbide (SiC), activated carbon (AC), and biochar (BC). The heating profiles of microwave heating with different susceptors were characterized. With SiC as the susceptor, three distinct heating stages were observed, which were believed to correspond to the three main stages of lignin decomposition. The effects of temperature, susceptor loading weight, and susceptor type on product yield and composition were investigated. Higher pyrolysis temperatures favored char reduction, demethoxylation and alkylation of phenols, and H-2 formation. Higher SiC loading weight promoted the formation of alkyl phenols and syngas (CO and H-2). Compared with SiC, both AC and BC enhanced the production of syngas, accounting for 74.5% and 70.1% in volume percentage, respectively. AC contributed to the highest bio-oil and gas production while BC showed highest selectivity to phenol and alkyl phenols, up to 58.2% and 37.7%, respectively.