Synergistic Effects of Mesoporosity and Surface Acidity in Sepiolite-Based Catalysts for Low-Temperature CO2 Desorption

High regeneration energy remains a major limitation of amine-based CO2 capture. This study investigates sepiolite (SEP) modified with metal oxides as solid acid catalysts to enhance CO2 desorption from CO2-rich monoethanolamine at 88 °C. Ten composite catalysts incorporating Al2O3, CeO2, NiO, and CoO were synthesized via impregnation and characterized. Catalytic performance was evaluated in terms of desorption rate, CO2 release, and regeneration heat duty, and compared with pristine SEP and a blank system. All modified materials improved regeneration efficiency. The activity trend followed CoO@SEPs > NiO@SEPs > Al2O3@SEPs > CeO2@SEP > SEP > blank, with CoO@SEP-2/1 achieving a 77% increase in CO2 desorption and a 43.5% reduction in heat duty relative to the blank system, while maintaining stability over 20 cycles. Physicochemical characterization combined with machine learning analysis reveals that performance is governed not by total acidity alone but by a synergistic interplay between mesoporous accessibility and surface acidity arising from support-oxide interactions. Catalysts combining sufficient Lewis acid sites with moderate total acidity and limited strong Brønsted contributions exhibit the highest desorption efficiency. These findings establish structure–acidity–performance relationships in SEP-based catalysts and provide a scalable route to reduce the energy penalty of sorbent regeneration.