(477g) Optimization of Woody Biomass Conversion Via Amine-Based Solvent Pretreatment

The development of scalable and cost-efficient biomass pretreatment methods to enhance the conversion of biomass has been a challenging problem over the past decades. The purpose of this work is to optimize the conversion of woody biomass feedstocks (walnut, almond) to fermentable sugars when subjected to a process using distillable amine-based solvents, as well as demonstrating high solvent recovery and characterizing the resulting biomass fractions. Therefore, pretreatment experiments were performed at a bench-scale using an almond and walnut mix (80/20, w/w) with butylamine, ethanolamine,
ethylenediamine, triethylamine (boiling points; 78, 170, 117, and 89 °C, respectively), and amine-water mixtures at different weight ratios (10-75 wt%). The biomass-solvent ratio was maintained at a fixed value and the pretreatment was performed in a pressure tube reactor for a specified reaction time. The pretreated biomass slurry was processed in three pathways: (1) washed with water, (2) distilled (3) distilled and washed with water. Each of the fractions along with raw untreated biomass were characterized for glucan/xylan composition, CHN content, and sugar release efficacy. The glucan and xylan compositions suggested that the glucan/xylan content were improved by ~18-36 % with decreasing water percentage. Results indicate that pathway-1 showed >90 % sugar release, about 41-43 % higher than pathways-2 or 3. Elemental analysis via CHN analyzer showed that a reduction in C/N ratio follows their boiling point order after distillation. Washing of distilled biomass increases the C/N ratio by 19%, 384%, and 232% for butylamine, ethanolamine, and ethylenediamine, respectively, suggesting washing could hardly remove any butylamine as chemical bonding might be present. In addition, adding water in the amine-based solvent showed higher solid recovery, implying lower sugar release than standalone amine-based solvent. Ongoing solvent recycling experiments suggested promising recovery of these amine-based solvents after lignocellulosic biomass pretreatment.

Keywords: Biomass; Pretreatment; Amine-based solvent, Enzymatic hydrolysis; Sugar;