Catalytic depolymerization of organosolv lignin from bagasse by carbonaceous solid acids derived from hydrothermal of lignocellulosic compounds

Abstract

In the present work, depolymerization of isolated lignin from organosolv fractionation of bagasse in the presence of several homogeneous and heterogeneous acid catalysts was studied. The catalysts included homogeneous acids (i.e. H2SO4, H3PO4 and HCl), and heterogeneous carbonaceous solid acids (CSAs) synthesized from the hydrothermal treatment of glucose, cellulose and lignin. It was found that the highest phenolic monomers yield was achieved from CSA derived from lignin (CSAlignin). In addition, this catalyst showed the highest activity and stability after 5 consecutive cycles, which was related to its high acidity as well as its low acid leaching compared to CSACellulose and CSAGlucose. The effects of catalyst loading, reaction temperature, reaction time, and solvent type (i.e. methanol, ethyl acetate, methyl isobutyl ketone (MIBK), acetone) on the depolymerization performance were also performed. It was observed that the reaction at 350 °C for 3 h using MIBK as solvent with CSAlignin loading of 10 wt% gave the maximum total phenolic yield of 32.8%, from which 4-ethylphenol and guaiacol were the major phenolic products from the reaction. The results in the work suggest that catalytic depolymerization of organosolv lignin in the presence of CSA is a promising way for production of high value-added chemicals.