Conversion of levulinic acid from various herbaceous biomass species using hydrochloric acid and effects of particle size and delignification

Acid catalyzed hydrothermal conversion of levulinic acid (LA) from various herbaceous materials including rice straw (RS), corn stover (CS), sweet sorghum bagasse (SSB), and Miscanthus (MS) was evaluated. With 1 M HCl, 150^◦C, 5 h, 20 g/L solid loading, the yields of LA from untreated RS, CS, SSB and MS based on the glucan content were 60.2, 75.1, 78.5 and 61.7 wt %, respectively. It was also found that the particle size had no significant effect on LA conversion yield with >3 h reaction time. With delignification using simulated green liquor (Na₂CO₃-Na₂S, 20 wt % total titratable alkali (TTA), 40 wt % sulfidity) at 200^◦C for 15 min, lignin removal was in the range of 64.8-91.2 wt %. Removal of both lignin and xylan during delignification increased the glucan contents from 33.0-44.3 of untreated biomass to 61.7-68.4 wt % of treated biomass. Delignified biomass resulted in much lower conversion yield (50.4-56.0 wt %) compared to 60.2-78.5 wt % of untreated biomass. Nonetheless, the concentration of LA in the product was enhanced by a factor of ~1.5 with delignification.