Elucidating the synergistic interaction and reaction pathway between the individual lignocellulosic components during flash pyrolysis

Abstract

• Homogeneous volatile-volatile interaction is overwhelming in flash pyrolysis. • Oxygen-bearing radicals induced volatile reactions between aliphatics and aromatics. • Lignin char is the most catalytically active for secondary reactions of volatiles. • Cellulose char is the most active in trapping heavy molecules derived from lignin. • The interaction between cellulose/xylan and lignin promotes the overall conversion. In this study, systematic experiments have been conducted to elucidate the synergistic interaction during the flash pyrolysis of lignocellulosic biomass. Through the use of Pyroprobe coupled with GC-FID and TCD, and the testing of individual components, their derivatives, model compounds and blends, the interaction of biomass components was confirmed to be affected by both heterogeneous char-volatile and homogeneous volatile-volatile interactions. The latter interaction was overwhelming in contributing to an enhanced bio-oil yield by the transferring of oxygen-bearing radicals from cellulose/xylan-bound hydroxyl to the volatiles such as p-cresol from lignin, and vice versa, by an induction effect of the lignin-derived volatiles on the release/transformation of cellulose/xylan volatiles. Alternatively, the heterogeneous char-volatile interaction was crucial in improving the non-condensable gas yield. The lignin char was the most catalytically active for the deoxygenation of volatiles, followed sequentially by xylan char, and cellulose char which was the most active in trapping the heavy molecules derived from lignin. The synergy of cellulose/xylan and lignin also promoted the overall conversion to complete more quickly.