Monitoring and Analyzing Process Streams Towards Understanding Ionic Liquid Pretreatment of Switchgrass (Panicum virgatum L.)

Fundamental understanding of biomass pre- treatment and its influence on saccharification kinetics, total sugar yield, and inhibitor formation is essential to develop efficient next-generation biofuel strategies, capable of displacing fossil fuels at a commercial level. In this study, we investigated the effect of residence time and temperature during ionic liquid (IL) pretreat- ment of switchgrass using 1-ethyl-3-methyl imidazolium acetate. The primary metrics of pretreatment perfor- mance are biomass delignification, xylan and glucan depolymerization, porosity, surface area, cellulase ki- netics, and sugar yields. Compositional analysis and quantification of process streams of saccharides and lignin demonstrate that delignification increases as a function of pretreatment temperature and is hypothe- sized to be correlated with theapparent glass transition temperature of lignin. IL pretreatment did not generate monosaccharides from hemicellulose. Compared to untreated switchgrass, Brunauer-Emmett-Teller surface area of pretreated switchgrass increased by a factor of ∼30, with a corresponding increase in saccharification kinetics of a factor of ∼40. There is an observed dependence of cellulase kinetics with delignification efficiency. Although complete biomass dissolution is observed after 3 h of IL pretreatment, the pattern of sugar release, saccharification kinetics, and total sugar yields are strongly correlated with temperature.