Energy-saving CO2 desorption from amine solution over Fe/SiO2/biochar catalysts: Desorption performance, structure-activity relationship, and mechanism

Abstract

Solid acid-catalyzed regeneration of amine-based absorbents is an available choice for reducing the energy requirements of CO2 capture, but it faces crucial challenges in optimizing catalyst structure and comprehending reaction mechanisms. In this work, a series of ternary solid acid catalysts containing SiO2, Fe3O4, and biochar were designed to evaluate their catalytic efficiency and mechanism for the regeneration of CO2-rich monoethanolamine (MEA) solutions. In the presence of SiO2 nanoparticles, FeCl3 and wheat flour were used as precursors to prepare Fe/SiO2/biochar composites with different amounts of iron through a one-pot pyrolysis method. Fe3O4 nanocrystals with abundant Brønsted/Lewis acid sites are connected to SiO2 nanoparticles through porous biochar to form aggregates. The presence of biochar increased the specific surface area of the composite catalysts and provided additional proton donors and nonacidic catalytic sites. The evaluation of catalytic desorption performance showed that compared to the thermal desorption, the optimized ternary catalyst increased the CO2 desorption amount by 35% and reduced the relative heat duty by 34%. The catalysts exhibited superior stability, with a decrease of only 6.1% in relative energy consumption during five cycles. A mechanism of proton donor-assisted charge transfer enhancement has been proposed to explain the acceleration of CO2 desorption and the reduction of energy consumption. The charge transfer enhancement mechanism mediated by the carbonaceous component allows for a novel design approach to fabricate superior solid acid catalysts for amine solvent regeneration. The simple methods and cheap feedstocks are suitable for large-scale production, providing attractive options for the industrial application of CO2 capture.