Constructing active copper species in Cu-zeolites for coal-gas-SCR and elucidating the synergistic catalytic function of CuO and Cu2+ ion species

Abstract

Coal-gas-SCR, initially proposed in this work, is a low-cost and effective strategy to eliminate NO_x emission in the iron and steel industry. In this work, the Cu-ZSM-5-IE+CP catalyst prepared by liquid ion exchange combined with coprecipitation was filtered out for NO_x abatement with coke-oven gas (H₂, CH₄, and CO). By means of XRD, TEM, H₂-TPR, EPR, UV-vis, XPS, etc., active centers of Cu-ZSM-5-IE+CP were studied. Combined with DFT calculations and ab initio thermodynamic (AIT) analyses, it was confirmed that highly dispersed CuO nanoparticles with the (111) planes exposed and [ZCuOH]/[Z₂Cu] in the Z[Cu(II)]-6R-D_4h structure are the most possible main active motifs for the coal-gas-SCR. Moreover, the synergistic effect of Cu²⁺ ions and CuO species was elucidated. In situ DRIFTS and SCR-TPD results revealed that surface species can migrate between CuO and Cu²⁺ ions, which could further accelerate intermediate species (NCO, CH₃NO, and NH₄⁺) formation, resulting in better deNO_x efficiency.