A Two-Step Catalytic Depolymerization of Alkali Treated Pennisetum glaucum L. and Melia dubia cav. into Low Molecular Weight (LMW) Aromatics


                                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, p-propyl guaiacol (0.27, tetra-hydrofurfurol (0.12, p-ethyl syringol (0.08, syringol (0.05 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

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