Mechanistic insights into the effects of phosphoric acid-hydrogen peroxide pretreatment on pine biomass pyrolysis and product quality enhancement

This work examines how phosphoric acid-hydrogen peroxide (PHP) pretreatment influences the pyrolysis behavior of pine biomass and the characteristics of the resulting products. The results indicate substantial removal of hemicellulose and lignin from the biomass following PHP pretreatment, resulting in a looser biomass structure, decreased surface oxygen-containing functionalities, and a reduced apparent activation energy during pyrolysis. After pretreatment, the bio-oil yield increases from 15.16% to over 30%, and the bio-oil yield of the sample pretreated with a concentrated phosphoric acid-hydrogen peroxide mixture at a concentration ratio of 50.0-10.0 wt% reaches 34.64%. Meanwhile, acid and carbonyl contents are substantially decreased, while phenolic species become more prevalent, reflecting a pronounced enhancement in fuel quality. In situ FTIR analysis reveals that PHP pretreatment accelerates the cleavage and transformation of hydroxyl and carbonyl groups, promoting the formation of oxygenated intermediates. Regarding biochar, PHP pretreatment enhances the specific surface area and microporous structure, enriches active functional groups, including hydroxyl, carboxyl, and thus increases the adsorption capacity for 2-naphthol by 18.66 times.