(35b) Parametric Study for the Optimization of Biomass Ionic Liquid Pretreatment for Conversion of Corn Stover to Soluble Sugars

An efficient lignocellulosic biomass pretreatment is one of the key requirements for the conversion of lignocellulosic biomass. Pretreatment with certain ionic liquids (IL), such as 1-ethyl-3-methylimidazolium acetate ([C₂C₁Im][OAc]), is highly effective at reducing biomass recalcitrance by disrupting the lignin-carbohydrate complex and increasing the accessibility of the cellulose to saccharification. It has also been demonstrated that certain ILs can efficiently process lignocellulosic biomass at high solids loading (50wt%), large particle sizes (>4mm), and low enzyme loads (5 mg/g glucan) that lower costs and enhance the commercial viability of this pretreatment technology.

Based on these initial results, we have conducted a thorough parametric study of the efficacy of [C₂C₁Im][OAc] for the pretreatment of corn stover at 140 ^oC for 3 h in order to establish the upper and lower limits for IL pretreatment. This was achieved by focusing on the extremes of biomass pretreatment and enzyme loading. This included evaluating the impact of high (50 wt%) and low (15 wt%) biomass loading for milled and non-milled corn stover on IL pretreatment efficiency, as well as the impact of high (20 mg/g glucan) and low (5 mg/g glucan) enzyme loading on measured sugar yields. The results indicate that [C₂C₁Im][OAc] is very effective in pretreating large particle sized corn stover at high biomass loading, thus avoiding the requirement for size reduction without compromising overall sugar recovery. The results also indicate that high sugar yields can be obtained at the lowest enzyme loading studied. The knowledge gained from the material balance calculations from these process conditions will be presented and are an essential step to demonstrating the commercial viability of this promising pretreatment technology, and we will also present the results from technoeconomic modeling of this process.