Attapulgite as a cost-effective catalyst for low-energy consumption amine-based CO2 capture

Abstract

The extensive heat duty of solvent regeneration has significantly hampered the industrial application of amine-based CO2 capture technology. Catalytic CO2 desorption with solid acid catalysts has recently emerged as a promising and competitive strategy for improving solvent regeneration performance. The reported catalysts have exhibited poor activities and are relatively expensive, which has slowed the large-scale implementation of this technique. In this work, three low-cost and environmentally friendly clay catalysts, namely, attapulgite (ATP), activated bentonite (K-10), and sepiolite (SEP), were used to catalyze the CO2 desorption in the CO2-loaded 5 M monoethanolamine (MEA) solution at 88 °C. The findings revealed that ATP, K-10, and SEP catalysts accelerated CO2 desorption, and the ATP demonstrated better catalytic activity in the early stage of the desorption process. In particular, the introduction of ATP significantly increased the CO2 desorption rate by 54–57% and reduced the relative heat duty by about 32%, compared to the blank test. The superior catalytic performance of ATP might be attributed to its favorable surface area and medium acid sites. The catalytic effect of ATP was confirmed using FT-IR and Raman techniques, and a potential catalytic desorption mechanism was proposed. Furthermore, the stability of activated ATP was demonstrated using 15 CO2 absorption-desorption cycles. These results demonstrated that ATP significantly contributes to the advancement of the amine-based CO2 capture process and has significant potential for large-scale deployment. This work may pave the avenue for developing abundant and inexpensive clay-based solid acid catalysts for low-energy consuming CO2 capture technology.