Renaissance of fly ash as eco-friendly catalysts for rapid CO2 release from amines

Abstract

Catalyst-assisted amine regeneration has emerged as a prominent strategy for enhancing the desorption rate of CO₂ from amine solutions at lower temperatures (<100 °C), thereby reducing the massive energy penalty of post-combustion carbon capture process. To make this strategy practical and commercially relevant, it is crucial to develop economically viable, abundant, and eco-friendly catalysts. In this context, we synthesized catalysts from fly ash (FA) through treatment with three acidic solutions of H₂SO₄, H₃PO₄, and HNO₃ and used them in amine regeneration process with evaluating their catalytic performance in terms of CO₂ desorption rate, desorbed CO₂ quantity, and regeneration heat duty. The acid treatment increased the BET surface area and generated surface acid sites of the FA, both of which played a vital role in increasing the CO₂ desorption from monoethanolamine (MEA) solution at 86 °C. The prepared catalysts increased the CO₂ desorption rate by up to 91 % and desorbed CO₂ amount by up to 61 %, while reducing the regeneration heat duty by up to 38 % compared to the uncatalyzed amine solution. The studied catalysts could be easily separated and used in successive amine regeneration cycles, which makes them suitable for industrial application.