Characterization of Lignin Derived from Water-only and Dilute Acid Flowthrough Pretreatment of Poplar Wood at Elevated Temperatures

Flowthrough pretreatment of biomass has high potential to valorize lignin derivatives to high-value products, which is vital to enhance the economy of biorefinery plants.  Comprehensive understanding of lignin behaviors and solubilization chemistry in aqueous pretreatment such as water-only and dilute acid flowthrough pretreatment is of fundamental importance to achieve the goal of providing flexible platform for lignin utilization. In this study, poplar wood will be flowthrough pretreated by water-only or 0.05% (w/w) sulfuric acid under different temperature (200-300 C), flow rate (5-62.5mL/min), and residence time (0-60min). Mass balance and ultraviolet spectroscopy will be applied to reveal lignin precipitation, depolymerization as well as solubilization mechanism during the pretreatment. Py-GC/MS, GC/MS as well as FTIR, will be further carried out on recovered lignin isolates to reveal intrinsic structural modification of lignin under the tested pretreatment conditions. In this regard, the study will validate the characteristics of solubilized depolymerized lignin fragment and identify unique lignin dissolution features. The results show that both of water-only and dilute acid pretreatment are effective in separating lignin by selectively hydrolyze C-O-C bonds and lignin cross-linkages from biomass to reactive lignin intermediates for further conversion to high value chemicals and biofuels.