Biochar-mediated release of CO2 from monoethanolamine/H2O solution with low energy requirement over ZrO2/SiO2/biochar ternary catalysts

Abstract

CO2 absorption technology based on amine solutions has sustained appeal due to its high efficiency in post-combustion capture of CO2. However, the high energy penalty of solvent regeneration limits its large-scale industrial application. Therefore, designing inexpensive catalysts to reduce solvent regeneration energy consumption remains challenging. This study reports a recyclable ternary catalyst, ZrO2/SiO2/biochar, which was synthesized by co-pyrolysis of zirconium oxychloride and wheat flour in the presence of SiO2 nanoparticles. The incorporation of biochar improved the distribution of Lewis acidic sites (LAS) and Brønsted acidic sites (BAS). The improved BASs and LASs of ZrO2/SiO2/biochar catalyst were conductive to donate protons or accept electrons and thus, the amount and rate of CO2 desorption from CO2-saturated monoethanolamine (90 °C) were more than 24% and 26% higher, respectively, to compare with the catalyst-free system at the same conditions. As a result, the energy penalty was decreased by about 31%. A biochar-mediated proton-transfer mechanism that the presence of biochar increased the mesoporous proportion, the BAS and L/B ratio as well as the favorable charge transfer was inferred for the ZrO2/SiO2/biochar-catalyzed CO2 release through experimental evidence. The results reveal the role of biochar in solid acid catalysts for CO2 desorption, which will provide a novel strategy for building solid acid catalysts to reduce energy requirements in CO2 capture.