Quantification and kinetic study of the main compounds in biocrude produced by hydrothermal carbonization of lignocellulosic biomass

Abstract

The biomass hydrothermal carbonization (HTC) reaction pathway to the formation of primary and secondary hydrochar is proposed in this study. Total sugars were the main product in biocrude at low temperature; their concentration decreased as the temperature increased, producing organic acids and furans. Kinetic study reveals that the hydrolysis activation energy increased as hemicellulose content decreased. Indeed, a value of 63.08 kJ/mol was found for biomass rich in hemicellulose (avocado stone) while for biomass composed of a hemicellulose-cellulose mixture (agave bagasse) the value was 85.02 kJ/mol, and for α-cellulose it was 136.24 kJ/mol. Contrastively, the activation energy for furans formation was higher than that for organic acids in any case. A proposed14-reactions mechanism adequately describes the HTC process considering intermediate to final products (R2 > 0.98). The higher heating value (HHV) of hydrochars was between 22 and 26 MJ/kg, with an energy densification of 34 to 49% compared to the corresponding feedstock.