Effect of Hydrothermal Pretreatment on the Properties of Lignin-Based Porous Carbon and the Adsorption Mechanisms of Co2

Abstract

The present study reports the economic and sustainable syntheses of functional porous carbon microsphere from biomass for CO2 capture applications. Lignin was used as a carbon source, and successfully converted into a series of lignin-based porous carbon (LPCs) through adjusting pH value of hydrothermal carbonization and followed by the CO2 physical activation. The results show that the LPCs-pH 1 was the only one having the structure with typical carbon microspheres, which has the characteristics of the highest carboxyl content, higher specific surface area and the great stability of CO2 adsorption cycle. The pH value of hydrothermal solution affected the polymerization and aromatization stages of spheroidization. In addition, the CO2 adsorption mechanism was further proved by simulated calculation used Gaussian 16. The influence factors of CO2 adsorption were divided into the electrostatic attraction of functional groups and the diffusion of CO2, the main control factor was the former at lower temperatures, because the carboxyl groups have the strongest electrostatic attraction to CO2, while CO2 diffusion resistance became a key factor as the adsorption temperature increased. This study illustrates the lignin as a low value biomass product can be converted into a highly functional carbon material for CO2 adsorption.

Keywords: lignin, hydrothermal, carbon microspheres, CO2 adsorption mechanism