Niobium-Modified HZSM-5 Zeolite Catalyzes Low-Energy Regeneration of CO2-Captured Amine Solution

Monoethanolamine (MEA)-based carbon dioxide absorption is one of the effective carbon capture, utilization, and storage (CCUS) technologies but is significantly restricted by the high energy consumption in the regeneration of rich amine solution. Solid acid catalysts have the potential to reduce energy consumption, while the exploration of highly active catalysts with abundant Bro̷nsted and Lewis acid sites remains needing. We developed an efficient solid acid catalyst, niobium-modified HZSM-5 (Nb/HZ), to facilitate CO2 desorption from the CO2-captured MEA solutions. The Nb/HZ catalysts with various niobium loadings were synthesized by using an impregnation method. HZSM-5 retained its pore structure and large surface area after niobium incorporation. The catalyst with 4% Nb (4.0-Nb/HZ) has the highest activity and stability, with 61% increase in the desorption rate, 50% increase in the desorbed CO2 amount, and 37% reduction of relative heat duty. According to theoretic calculations and experimental analyses, the Nb/HZ catalyst provides abundant Bro̷nsted and Lewis acid sites to facilitate carbamate adsorption, proton transfer, and carbamate breakdown, thus reducing the activation energy for CO2 desorption. This work provides a valuable solid acid catalyst for amine-based CO2 capture and also brings insights for the development of a novel solid acid for diverse catalysis.