Supercritical ethanol as an enhanced medium for lignocellulosic biomass liquefaction: Influence of physical process parameters

• Published in: Energy (Oxford) Vol. 59; pp. 173 - 182
• Main Authors: Brand, Steffen, Susanti, Ratna Frida, Kim, Seok Ki, Lee, Hong-shik, Kim, Jaehoon, Sang, Byung-In
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15.09.2013; Elsevier
• Subjects: Applied sciences; Biocrude; Biomass; carbon; catalysts; Conversion; Energy; Ethanol; Ethyl alcohol; Exact sciences and technology; feedstocks; heat; hydrogen; Hydrogen donor; Lignocellulose; Lignocellulosic biomass; Liquefaction; molecular weight; Natural energy; nitrogen; oxygen; Process parameters; Supercritical ethanol; temperature; Wood; Biocrude; Supercritical ethanol; Liquefaction; Lignocellulosic biomass; Hydrogen donor; Lignocellulosics; Biomass
• ISSN: 0360-5442
• DOI: 10.1016/j.energy.2013.06.049

In this study, the influence of various physical process parameters on the liquefaction of lignocellulosic biomass (pine wood) in supercritical ethanol was investigated. The parameters include reaction temperature (280–400 °C), initial nitrogen pressure (0.4–7.5 MPa), reaction time (0–240 min), and biomass-to-solvent ratio (0.06–0.25 g/g). The reaction temperature and residence time were found to have a more significant effect on biomass conversion and product yield than pressure and biomass-to-solvent ratio had; conversion in the range 34.0–98.1% and biocrude yield in the range 15.8–59.9 wt% were observed depending on the process parameters. Despite the absence of catalysts and external hydrogen source, solid biomass to liquid and gaseous products conversion of 98.1%, and a high biocrude yield of approximately 65.8 wt% were achieved at 400 °C, 120 min, and a biomass-to-solvent ratio of 0.06 g/g. Moreover, the biocrude contained considerably lower amounts of oxygen and higher amounts of carbon and hydrogen, resulting in a substantially higher heating value (>30 MJ/kg) as compared to raw feedstock (20.4 MJ/kg). A comparison with sub- or supercritical water-based liquefaction revealed that supercritical ethanol produced biocrude with a lower molecular weight and much better yield. Finally, a new biomass liquefaction reaction mechanism associated with supercritical ethanol is proposed. •Influence of physical parameters on biomass liquefaction in supercritical ethanol.•Benefits of supercritical ethanol as a solvent in biomass liquefaction.•High conversion (98%) and high biocrude yield (66 wt%) achieved.•Comparison with sub- and supercritical water liquefaction has been made.•New reaction mechanism of supercritical alcohol has been proposed.