NH3-Induced Challenges in CO2 Hydrogenation over the Cu/ZnO/Al2O3 Catalyst

High Resolution Image Download MS PowerPoint Slide Gas sources rich in CO 2 derived from biomass/waste gasification, anaerobic digestion, or industrial carbon capture often contain impurities such as H 2 S, H 2 O, and NH 3, which can significantly hinder catalyst performance. Here, we show the role of NH 3 on the reverse water–gas shift (RWGS) reaction over a commercial Cu/ZnO/Al 2 O 3 catalyst, examining its effects on both the catalytic activity and the catalyst structure. We found that NH 3 reversibly decreases CO 2 conversion immediately by suppressing carbonate hydrogenation and CO desorption. This effect intensifies with an increase in NH 3 concentration but decreases at higher temperatures. However, prolonged exposure (over 100 h) to RWGS conditions in the presence of 1.4% NH 3 leads to near-total and irreversible deactivation of the Cu/ZnO/Al 2 O 3 catalyst. Under NH 3 exposure, the catalyst loses Cu + sites on the surface, causing a spatial separation of Cu and ZnO. Finally, to address this challenge, we propose a novel strategy to mitigate NH 3 inhibition by decomposing NH 3 into N 2 and H 2 .