Abstract
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.
Highlights
Levulinic acid (LA) has been identified as a promising platform chemical for the generation fuels and chemicals; for example, γ-valerolactone (GVL) and methyltetranhydrofuran (MTHF) as gasoline additives, ethyl levulinate as a diesel additive, and 2,5-furandicarboxylic acid (2,5-FDCA) as a substitute for terephthalic acid (PTA) [1]
Green liquor pretreatment was proven effective for the extraction of lignin [16]
It has been reported that green liquor pretreatment at 140–160 ◦ C for 60–120 min to be effective for pretreatment of corn stover (CS) [22,23]
Summary
Levulinic acid (LA) has been identified as a promising platform chemical for the generation fuels and chemicals; for example, γ-valerolactone (GVL) and methyltetranhydrofuran (MTHF) as gasoline additives, ethyl levulinate as a diesel additive, and 2,5-furandicarboxylic acid (2,5-FDCA) as a substitute for terephthalic acid (PTA) [1]. The lignocellulosic biomass is converted to 5-HMF (210–220 ◦ C, 25 bar, 12 s) and in the second stage, HMF undergoes hydration to yield LA and formic acid under less severe conditions (190–200 ◦ C, 14 bar, 20 min) [19]. Miscanthus (MS), a perennial grass, is currently utilized in Europe as a commercial energy crop because of its high cellulose content (40–48%) and high annual biomass yield [20,21] Owing to their abundance and diversity in chemical composition, these four herbaceous biomass species were selected as feedstock in this study
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