Fractionation of lignin from corncob with high−yield p − coumaric acid production in deep eutectic solvents followed by pyrolysis to produce monophenols

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Two distinctive aromatic units, p − coumarate and ferulate, exist in corncob lignin, which have the potential to yield p − coumaric acid (pCA) and ferulic acid (FA). Although pCA and FA are primarily extracted from corncob lignin utilizing strong acids and bases, extremely acidic or alkaline conditions result in the disruption of the aromatic unit structure of the residual lignin. Herein, lactic acid coupled with choline chloride was utilized as acidic deep eutectic solvent (DES), while K2CO3 with glycerin was used as alkaline DES, thereby facilitating the extraction of pCA, FA and lignin from corncob in a mild environment. Furthermore, the differences in monophenol yields from pyrolysis of lignin were investigated. The alkaline DES exhibited a stronger extraction capacity for these acids. The yields of pCA and FA were 15.47 mg/g and 7.44 mg/g (based on the weight of corncob). Contrastively, the subsequent pyrolysis process yielded a higher amount of monophenol from the lignin extracted using acidic DES, with notably greater quantities of low methoxy phenolic monomers. This renders it a preferred option for subsequent processing into high−calorific biofuels. This work presents a straightforward and efficient strategy for the deconstruction of the lignin from corncob to enhance the utilization value of agricultural waste.