Hydrothermal Liquefaction of Rice Straw Using Methanol as Co-Solvent

Attada Yerrayya, A. K. Shree Vishnu, S. Shreyas, S. R. Chakravarthy and Ravikrishnan Vinu
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Attada Yerrayya: Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai 600036, India
A. K. Shree Vishnu: Department of Aerospace Engineering, Indian Institute of Technology Madras, Chennai 600036, India
S. Shreyas: Department of Aerospace Engineering, Indian Institute of Technology Madras, Chennai 600036, India
S. R. Chakravarthy: Department of Aerospace Engineering, Indian Institute of Technology Madras, Chennai 600036, India
Ravikrishnan Vinu: Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai 600036, India

Energies, 2020, vol. 13, issue 10, 1-19

Abstract: Hydrothermal liquefaction (HTL) is a promising thermochemical process to treat wet feedstocks and convert them to chemicals and fuels. In this study, the effects of final temperature (300, 325, and 350 °C), reaction time (30 and 60 min), rice-straw-to-water ratio (1:1, 1:5, 1:10, and 1:15 (wt./wt.)), methanol-to-water ratio (0:100, 25:75, 50:50, and 75:25 (vol.%/vol.%)), and alkali catalysts (KOH, NaOH, and K 2 CO 3 ) on product yields, composition of bio-crude, higher heating value (HHV) of bio-crude and bio-char, and energy recovery on HTL of rice straw are investigated. At the optimal processing condition corresponding to the final temperature of 300 °C, 60 min reaction time, and rice-straw-to-water ratio of 1:10 at a final pressure of 18 MPa, the bio-crude yield was 12.3 wt.% with low oxygen content (14.2 wt.%), high HHV (35.3 MJ/kg), and good energy recovery (36%). The addition of methanol as co-solvent to water at 50:50 vol.%/vol.% improved the yield of bio-crude up to 36.8 wt.%. The selectivity to phenolic compounds was high (49%–58%) when only water was used as the solvent, while the addition of methanol reduced the selectivity to phenolics (13%–22%), and improved the selectivity to methyl esters (51%–73%), possibly due to esterification reactions. The addition of KOH further improved the yield of bio-crude to 40 wt.% in an equal composition of methanol:water at the optimal condition. The energy-consumption ratio was less than unity for the methanol and catalyst system, suggesting that the process is energetically feasible in the presence of a co-solvent.

Keywords: hydrothermal liquefaction; rice straw; bio-crude; methanol; phenols; esters; energy-consumption ratio (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (4)

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