Green solvents to enhance hydrochar quality and clarify effects of secondary char

Giulia Ischia; Jillian L Goldfarb; Antonio Miotello; Luca Fiori

doi:10.1016/j.biortech.2023.129724

Green solvents to enhance hydrochar quality and clarify effects of secondary char

Bioresour Technol. 2023 Nov:388:129724. doi: 10.1016/j.biortech.2023.129724. Epub 2023 Sep 6.

Authors

Giulia Ischia¹, Jillian L Goldfarb², Antonio Miotello³, Luca Fiori⁴

Affiliations

¹ Department of Civil, Environmental and Mechanical Engineering, University of Trento, Via Mesiano 77, 38123 Trento, Italy; Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY 14853, USA.
² Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY 14853, USA; Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY 14853, USA.
³ Department of Physics, University of Trento, Via Sommarive 14, 38123 Trento, Italy.
⁴ Department of Civil, Environmental and Mechanical Engineering, University of Trento, Via Mesiano 77, 38123 Trento, Italy; Center Agriculture Food Environment (C3A), University of Trento, San Michele all'Adige, 38010 Trento, Italy. Electronic address: luca.fiori@unitn.it.

PMID: 37683708
DOI: 10.1016/j.biortech.2023.129724

Abstract

Several limitations hinder the industrial-scale implementation of hydrothermal carbonization (HTC) of biomass, especially the quality of as-carbonized hydrochar. This work investigates solvent extraction of hydrochars to enhance their potential applications. Hydrochars were produced at several HTC temperatures (190, 220, 250 °C) from cellulose and extracted using combinations of green polar solvents (ethyl acetate, acetone, and methanol). Results show that the composition of the extractable fraction resembles that of the HTC liquor, rich in carboxylic acids and furan derivatives, while the non-extractable solid phase shows improved thermal profiles devoid of highly volatile compounds. Carbon microspheres (non-dissolvable secondary char) are unaffected by extraction. The organics adsorbed on the hydrochar surface comprise highly volatile species and solvent washing effectively removes them.

Keywords: Cellulose; HTC; Hydrothermal carbonization; Solvent extraction; Thermal stability.