Catalytic hydrothermal liquefaction of biomass with K₂CO₃ for production of gasification feedstock

ABSTRACT

The introduction of alkali catalyst during hydrothermal liquefaction (HTL) improves conversion and allows the aqueous liquid product to be used as gasification feedstock. This study investigates the effect of reaction temperature (240–300°C), sawdust mass fraction (9.1–25%) and reaction time (0–60 min) during K₂CO₃-catalytic HTL of pine sawdust. The highest biomass conversion (75.2% carbon conversion and 83.0% mass conversion) was achieved at a reaction temperature of 270°C, 9.1% sawdust mass fraction and 30 min reaction time; meanwhile, the maximum aqueous product (AP) yield (69.0% carbon yield and 73.5% mass yield) was found at a reaction temperature of 300°C, 9.1% sawdust mass fraction and 60 min reaction time. Based on the main experimental results, models for carbon and mass yields of the products were developed according to face-centered central composite design using response surface methodology. Biomass conversion and product yields had a positive correlation with reaction temperature and reaction time, while they had an inverse correlation with sawdust mass fraction. Further investigation of the effects of biomass/water and biomass/K₂CO₃ ratios revealed that both high water loading and high K₂CO₃ loading enhanced conversion and AP yield.

KEYWORDS:

• Hydrothermal liquefaction
• pine sawdust
• K₂CO₃
• response surface methodology

Acknowledgements

This work was supported by the Japan Society for the Promotion of Science (JSPS) and the Swedish Foundation for International Cooperation in Research and Higher Education (STINT) through the Japan–Sweden Research Collaboration Program. Flabianus Hardi thanks the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan for a Japanese government scholarship. The contributions of (1) Gustav Häggström from the Luleå University of Technology for support during the commissioning of the batch reactor; (2) Dr. Akiko Nakagawa-Izumi from the University of Tsukuba and Dai Xin from the Tokyo Institute of Technology, for lignocellulosic analysis; and (3) Prof. Hirofumi Hinode from the Tokyo Institute of Technology, for ICP-AES analysis support, are deeply appreciated.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary Information

The supplementary material for this article can be accessed at https://figshare.com/articles/Supplementary_material/6139742.

Additional information

Funding

This work was supported by the Japan Society for the Promotion of Science (JSPS); Swedish Foundation for International Cooperation in Research and Higher Education (STINT, grant number JA2014-5724); Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan.