Effect of hydrogen peroxide on the depolymerization of prot lignin

Abstract

Lignin is an aromatic renewable polymer of lignocellulosic biomass, due to which it can be considered as a source for various chemical, bio-materials, polymers production. The complex structure of lignin is a big challenge for its valorization. Here, we have investigated the depolymerization of prot lignin into valuable compounds using ethanol and water (1:1) solvent mixture at various temperatures (100, 120, 140, 160 and 180 °C), residence time (15, 30, 60 and 120 min) in the presence of different amounts (0.25, 0.5, 1.0, 1.5, 3.0 and 5.0 ml) of 30 % H2O2, 5 bar molecular oxygen and 1 bar N2. Maximum bio-oil of 80.0 wt.% was obtained in the presence of 1.0 ml H2O2 at 120 °C for 30 min residence time. The characterization of bio-oil was carried out using various techniques such as 1H-NMR, FT-IR, and GC–MS. The char residue has been characterized using total organic carbon (TOC) analyser. The GC–MS compounds of bio-oil has been divided into four categories namely G, H, S type phenolics, and other type compounds. Among these GC–MS compounds (G, H, S, and other type compounds), S-type phenolics (66.7 wt.%) were observed to be the most abundant component of bio-oil in the presence of 0.5 ml H2O2. Maximum GC–MS area percentage of acetosyringone (59.3 %) was obtained as the major S-type phenolics at 120 °C temperature and 30 min residence time in the presence of 0.5 ml H2O2.