Metal Oxyhydroxide Catalysts Promoted CO₂ Absorption and Desorption in Amine-Based Carbon Capture: A Feasibility...

The huge energy penalty of CO₂ desorption is the greatest challenge impeding the commercial application of amine-based CO₂ capture. To deal with this problem, a series of metal oxide and oxyhydroxide catalysts were synthesized in this study to kinetically facilitate the CO₂ desorption from 5.0 M monoethanolamine (MEA). The effects of selected catalysts on CO₂ absorption kinetics, CO₂ absorption capacity, CO₂ reaction enthalpy, and desorption duty reduction of 2.0 M MEA were investigated by a true heat flow reaction calorimeter to access the practical feasibility of the catalytic CO₂ desorption. The kinetic study of catalytic CO₂ desorption was also carried out. CO₂ desorption chemistry, catalyst characterization, and structure-function relationships were investigated to reveal the underlying mechanisms. Results show that addition of the catalyst had slight effects on the CO₂ absorption kinetics and CO₂ reaction enthalpy of MEA. In contrast, the CO₂ desorption efficiency greatly increased from 28% in reference MEA to 52% in ZrO(OH)₂-aided MEA. Compared to the benchmark catalyst HZSM-5, ZrO(OH)₂ exhibited a 13% improvement in CO₂ desorption efficiency. More importantly, compared to the reference MEA, the CO₂ desorption duties of ZrO(OH)₂ and FeOOH-aided MEA significantly reduced by 45 and 47% respectively, which are better than those of most other reported catalysts. The large surface area, pore volume, pore diameter, and amount of surface hydroxyl groups of ZrO(OH)₂ and FeOOH afforded the catalytic performance by promoting the adsorption of alkaline speciation (e.g., MEA and HCO₃ ^-) onto the particle surface.