Highly efficient Ag/Ce-Zr catalyst for catalytic oxidation of NVOCs: balance of redox ability and acidity

Due to the presence of nitrogen, nitrogen-containing volatile organic compounds (NVOCs) are more difficult to remove than conventional volatile organic compounds (VOCs). Both catalytic activity and N-2 selectivity should be considered in the design of suitable catalysts. A series of Ag/Ce-Zr solid solution (Ag/CZ) catalysts were prepared and applied to the catalytic oxidation of N,N-dimethylformamide (DMF). Redox ability and acidity were regulated by modifying the Zr content. The introduction of Zr promoted the formation of active oxygen species until the molar ratio of Zr reached 0.5, after which the formation decreased. Moreover, adding Zr increased the number of weak and medium acidic sites, which significantly improved DMF adsorption. The improved DMF adsorption hindered the combination of nitrogen and active oxygen, thus reducing the generation of NOx effectively. Therefore, the Ag/CZ (5:5) catalyst, with suitable redox ability and acidity, exhibited the highest activity (T90 = 176 degrees C), the lowest elimination temperature of organic compounds (T = 255 degrees C), satisfactory N-2 yield (95%-75% in the range of 240-400 degrees C), and outstanding stability under both common and humid conditions (at least 50 h). The reaction mechanism was investigated based on the in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results. During the catalytic oxidation of DMF, the surface lattice oxygen directly participated in the dehydrogenation and dissociation of the C(O)-N bonds. The generated dimethylamine (DMA) was then oxidized by active oxygen species to form the final product.