Integrative process for a sugarcane bagasse biorefinery to produce glucose, bio-oil and carbon microspheres

Selective fractionation of cellulose from sugarcane bagasse (SCB) for the production of fermentable sugars was studied. The SCB was pretreated by hydrothermal pretreatment using five different types of solid acid catalysts (SACs): (1) self-synthesis SiO₂–OSO₃H, (2) SO₄²⁻/TiO₂/Fe₃O₄/WO₃, (3) sulfonated bentonite and commercial SAC, (4) Amberlyst^® 15, and (5) Dowex^® 50WX8. Fractionation of SCB was conducted in a combination with choline acetate (ChOAc) ionic liquid (IL) at moderate temperature. After enzyme hydrolysis, the highest total reducing sugar (TRS) yield of 78.1% was achieved when pretreated with SiO₂–OSO₃H. For the black liquor from fractionation, the highest amount of lignin could be precipitated from ChOAc IL through treatment with SO₄²⁻/TiO²/Fe₃O₄/WO₃. Pyrolysis of dry precipitated lignin was performed at 400 and 500 °C under a nitrogen atmosphere, and phenolic-rich oil was produced. Carbon microspheres appeared in the solid phase from the pyrolysis. It was postulated that lignin was first degraded to phenol with an aromatic structure, while other sugar residues (C5 and C6) in the lignin molecule formed ring compounds. These compounds underwent condensation polymerization as a shell-like shape, and carbon rich microspheres were thus formed.