Selective fractionation and enhanced cellulose accessibility of corn Stover using a cetyltrimethylammonium bromide/ethylene glycol/tartaric acid ternary deep eutectic solvent.
Abstract
Efficient fractionation of lignocellulose is essential for sustainable biorefining but remains challenged by the structural recalcitrance of plant cell walls. In this study, several ternary deep eutectic solvents (TDESs) were designed to enhance corn stover deconstruction. Systematic screening of various organic acids as the third component led to the selection of tartaric acid (TA) for synthesizing the novel TDES composed of Cetyltrimethylammonium bromide (CTAB), ethylene glycol (EG), and TA at an optimal molar ratio of 1:4:1.8. Under optimal conditions, this process achieved removal efficiencies of 81.0% for xylan and 74.8% for lignin, producing furfural at 63.0% of the theoretical yield from xylan conversion and xylo-oligosaccharides at 33.2% based on the initial xylan content. Concurrently, substrate accessibility increased to 583.6 mg/g, while surface lignin area decreased to 597.2 m2/g, collectively contributing to an impressive saccharification efficiency of 86.9%. Multiscale characterization by SEM, FT-IR, and XRD showed that TDES disrupted the compact cell-wall morphology, attenuated lignin- and hemicellulose-associated spectral features, and increased the cellulose crystallinity index. Mass and energy flow analysis indicated that 87.6% of the theoretical energy contained in cellulose was recovered in the product streams, with 5.16 MJ of energy effectively recovered in lignin-rich stream. Static electrostatic potential calculations and independent gradient model analysis explored potential non-covalent interactions between TDES components and representative lignocellulosic units, providing theoretical insight into the interactions that may contribute to the pretreatment performance. This work provides a tailored approach for designing highly selective TDES to alter corn stover structure and maximize the agricultural residue valorization.