Characterization and reactivity of soot from fast pyrolysis of lignocellulosic compounds and monolignols

Highlights: • Biomass soot samples were generated at fast pyrolysis conditions in a DTF at 1250 °C. • The reactivity of soot was determined in 40 vol.% CO₂ gasification by TGA. • The most reactive was cellulose soot with the largest separation distance. • The least reactive CH₃OH extracted lignin soot had the smallest separation distance. • The particle size and radical concentration of soot influenced the reactivity less. This study presents the effect of lignocellulosic compounds and monolignols on the yield, nanostructure and reactivity of soot generated at 1250 $°$C in a drop tube furnace. The structure of soot was characterized by electron microscopy techniques, Raman spectroscopy and electron spin resonance spectroscopy. The CO₂ reactivity of soot was investigated by thermogravimetric analysis. Soot from cellulose was more reactive than soot produced from extractives, lignin and monolignols. Soot reactivity was correlated with the separation distances between adjacent graphene layers, as measured using transmission electron microscopy. Particle size, free radical concentration, differences in a degree of curvature and multi-core structures influenced the soot reactivity less than the interlayer separation distances. Soot yield was correlated with the lignin content of the feedstock. The selection of the extraction solvent had a strong influence on the soot reactivity. The Soxhlet extraction of softwood and wheat straw lignin soot using methanol decreased the soot reactivity, whereas acetone extraction had only a modest effect.