(673h) Water Induced Ammonia Production on CuO/Al2O3 Catalyst in NO + CO Reaction

Based on our prior knowledge that CuO based catalysts exhibited superior catalytic performance in NO reduction by CO [1], CuO/Al₂O₃ serial catalysts with different CuO loadings (x wt.% CuO/Al₂O₃, denoted as xCu/Al) were synthesized using incipient wetness impregnation (IWI) method and evaluated for the possible NH₃ production from NO, CO and H₂O. With the increase of CuO loadings from 1 to 12 wt.%, monotonically increased NO removal efficiency was achieved on xCu/Al catalysts under dry condition (Fig. 1a). However, when 5 vol.% H₂O was added to the feeding stream, the NO conversion on 5Cu/Al increased significantly, achieving almost the same level as that on 12Cu/Al (Fig. 1b). Abundant NH₃ was formed on xCu/Al catalysts with the addition of H₂O to the feeding stream (Fig. 1c and 1d). The NH₃ generation on 5Cu/Al was the most vigorous, which started at the lowest temperature (275 ^oC). The efficient conversion of NO to NH₃ and the possible reaction between NH₃ and NO should be the main reason for the noticeable enhancement of NO reduction efficiency on 5Cu/Al in the presence of H₂O. Unlike that isolated Cu ions or crystalline CuO particles were formed on CuO/Al₂O₃ catalysts with lower (≤ 3 wt.%) or higher (≥ 7 wt.%) CuO loadings, respectively, highly dispersed CuO_x clusters were formed on 5Cu/Al. The highly dispersed CuO_x clusters with superior redox performance could better facilitate the activation/dissociation of H₂O to react with NO and CO, forming NH₃ and CO₂. This work provides a new strategy for NH₃ production from two common air pollutants with the assistance of H₂O on economic CuO/Al₂O₃ catalysts under mild reaction conditions.

References:

[1] W. Tan, Y. Cai, S. Xie, J. Xu, K. Ma, K. Ye, L. Ma, S. N. Ehrlich, W. Zou, F. Gao, L. Dong, F. Liu. Chem. Eng. J. 456: 140807, 2023.