Low-Temperature Torrefaction of Phyllostachys heterocycla cv. pubescens: Effect of Two Torrefaction Procedures on the Composition of Bio-Oil Obtained

Abstract

Low-temperature torrefaction of pubescens was studied by one-step (RT–200 °C) and two-step (RT–120 °C first, and then 120–200 °C) ways. For one-step torrefaction, the cracking of intermolecular and intramolecular hydrogen bonds in cellulose promoted the formation of oligosaccharide, anhydrosugar, and levoglucosan intermediates with monosaccharide, carboxylic acid, furans, etc. The oligomers with 4-O-5, β-O-4 linkages were mainly derived from the cleavage of C–O–C bonds between lignin and cellulose, and p-hydoxyphenyl (H), ferulate (F) intermediates were derived from the cracking of β-O-4 and Cα–Cβ in lignin. In two-step torrefaction, the first step (RT–120 °C) tended to generate the intermediates of oligosaccharide, levoglucosan and pyranose, which mainly derived from the cleavage of intermolecular hydrogen bonds or ether bonds in amorphous cellulose. The lignin-based oligomers with 4-O-5 and β-O-4 linkages were mainly derived from the cracking of β-O-4 and dehydration. For the second step (120–200 °C), t...