Evolution properties of cellulose- and lignin-derived pyrolysis tars after interacting with coal chars

- Cellulose and lignin volatiles were subjected to interactions with coal char.
- Lignin tars were more refractory to reforming/cracking than cellulose tars.
- Lignin tars had higher ratio of large aromatic ring systems than cellulose tars.
- Both tars underwent the transition from phenolics to PAHs with temperature.
- Biomass volatiles resulted in coke deposition on anthracite chars below 800 °C.

The reforming characteristics of biomass volatiles on anthracite chars were investigated by comparing the structural evolution of tars derived from cellulose and lignin as the major biomass components. In a two-stage quartz reactor, the pyrolysis volatiles of cellulose and lignin were produced in the first stage and then reformed in the second stage with or without the presence of anthracite chars between 600 and 900 °C. The results show that the presence of anthracite chars enhanced the destruction of volatiles of both feedstocks. Furthermore, the tar yields of lignin showed a slower decreasing trend with temperature than those of cellulose, suggesting that the lignin volatiles were more refractory to be reformed. The lignin tars had higher molecular weights and contained higher percentage of compounds with large aromatic ring systems (≥3 fused benzene rings) than cellulose tars in the studied temperature range. Compositional analysis revealed that tars of both feedstocks experienced the transition from phenolic compounds to polycyclic aromatic hydrocarbons with increasing temperature. The surface areas of anthracite chars were reduced because of coke deposition after interacting with the volatiles of both feedstocks below 800 °C, above which the net gasification of chars took place.