Biomass hydrothermal conversion under CO2 atmosphere: A way to improve the regulation of hydrothermal products

In this study, batched hydrothermal experiments on corn stalk were conducted at 240–330 °C under CO 2 or inert (N 2 ) atmosphere. The distribution and characteristics of gaseous, solid, and liquid products were analyzed in detail to comprehensively investigate the effects of CO 2 on the hydrothermal conversion of biomass, especially on the cellulose and lignin in biomass. The results demonstrate that compared with N 2 , CO 2 slightly increased the liquid and gas yields and significantly improved the control effect of temperature on bio-oil components. Under CO 2 atmosphere, bio-oil achieved effective enrichment of ketones and phenols at 240 °C and 300 °C, respectively, and their highest relative contents reached 44.8% and 62.0%, respectively. In addition, the hydrochar obtained under CO 2 atmosphere showed higher crystallinity , which is conducive to its subsequent utilization. This study explored the feasibility of introducing CO 2 into the biomass hydrothermal process to realize the high-value utilization of biomass waste and the reuse of CO 2 .