Synergistic Effect of Ce in Metal-Promoted Cu/Zeolite Beta Catalysts for Selective Ammonia Oxidation.

As global carbon neutrality policies intensify, mitigating ammonia (NH3) slip in carbon-free energy systems is crucial. In this study, a series of Cu-M/Zeolite Beta catalysts (M = Co, Ce, Mn, Cr, V, W, Fe) were synthesized for selective NH3 oxidation. The optimal 10Cu-5Ce/ZB catalyst achieved over 90% NH3 conversion and high N2 selectivity above 350 °C (100 ppm of NH3, 10% O2, 10% H2O, GHSV of 35,000 h-1). Notably, this noble-metal-free catalyst exhibited comparable apparent performance to noble-metal-promoted benchmarks. Physicochemical characterizations (including XRD, TEM, XPS, H2-TPR, and NH3-TPD) revealed that Ce addition improved Cu dispersion while maintaining the zeolite framework. Strong Cu-Ce synergistic interactions increased the concentration of surface Ce3+, oxygen vacancies, and adsorbed oxygen (Oads). Additionally, the Ce-promoted catalyst exhibited a significant increase in Lewis acidity, enhancing NH3 adsorption and activation. These integrated structural and electronic effects suggest that 10Cu-5Ce/ZB has potential as a cost-effective candidate for ammonia oxidation processes, warranting further pilot-scale investigations.