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]

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Summary

Introduction

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

Results and Discussion
Production of LA
Production of LA Using Delignified Biomass
Byproduct Formation during LA Conversion
Other Notes
Feedstock
Conversion of Biomass using Hydrochloric Acid
Analytical Methods
I—Results of Screening for
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