Abstract

                                The potential of lignin and its challenge for valorization has become the gold-rush nowadays for emerging bio-refineries. In the present investigation, alkaline H₂O₂ pre-treated two lignocellulosic biomass (LCB), agro residue (pearl millet) and hardwood (Melia dubia) were subjected to catalytic depolymerization. Of the catalysts optimized, Ru/C 1% recovered higher monomeric yield of 67% over Ni/C on carbon supports. The alkaline H₂O₂ pre-treatment of pearl millet and M. dubia showed less than 40% of biomass conversion into aromatics with more than 50% cellulose and hemicellulosic derivatives. The solid cox and gaseous loss for alkaline H₂O₂ pearl millet biomass sample were found to be 16.13% and 4.42 % for Ru- and 30.00% and 35.43 % for 1% Ru+ respectively with highest monomeric (97.84%) and least polymeric (2.16%) yield. Sugar derivatives such as diols and acids were detected more compared to lignin derivatives in alkali pretreated pearl millet. On the other hand, the alkaline H₂O₂ pre-treated M. dubia lignin registered a solid cox of 16.97%, gaseous loss of 12.95% and highest monomeric yield of 69.53% for 1% Ru+ which includes p-propyl syringol (0.32 mg.ml^-1), p-propyl guaiacol (0.27 mg.ml^-1), tetra-hydrofurfurol (0.12 mg.ml^-1), p-ethyl syringol (0.08 mg.ml^-1), syringol (0.05 mg.ml^-1) and so on. From the results obtained, it can be concluded that alkaline H₂O₂ pre-treated M. dubia is a suitable candidate for lignin based bio-refineries for high value platform chemicals, whereas alkaline H₂O₂ pretreated pearl millet can be employed for bio-ethanol production.

Key words : Lignocellulosic-biomass, Alkaline H₂O₂, Catalysts, Depolymerization, Aromatics