Kinetic and hydrogen production analysis in the sequential valorization of a Populus clone by cold alkaline extraction and pyrolysis

This work employed a two-step biorefining process, consisting of a hemicellulose-rich liquor production through ultrasound-assisted cold alkaline extraction (CAE), followed by thermochemical treatment of the resultant solid phase. The post-CAE solid phase's pyrolytic potential was assessed by application of thermogravimetric analysis (TGA) and Friedman's isoconversional method, and also from hydrogen production. The solid phases remaining after the CAE treatment were more reactive than the untreated raw material. Notably, the alkali concentration employed in the first step was the individual variable most pronounced influence on their activation energy (E-a). Thus, at a degree of conversion alpha = 0.50, E-a ranged from 109.7 to 254.3 kJ/mol for the solid phases, compared to 177 kJ/mol for the raw material; this value decreased with rising glucan content. At maximal degradation, the post-CAE solid phases produced up to 15.57% v/v more hydrogen than did the untreated raw material.