NiB2O4 (B = Mn or Co) catalysts for NH3-SCR of NOx at low-temperature in microwave field

Microwave-assisted selective catalytic reduction of nitrogen oxides (NOx) was investigated over Ni-based metal oxides. The NiMn2O4 and NiCo2O4 catalysts were synthesized by the co-precipitation method and their activities were evaluated as potential candidate catalysts for low-temperature NH3-SCR in a microwave field. The physicochemical properties and structures of the catalysts were characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), N-2-physisorption, NO adsorption-desorption in the microwave field, H-2-temperature programmed reduction (H-2-TPR) and NH3-temperature programmed desorption (NH3-TPD). The results verified that microwave radiation reduced the reaction temperature required for NH3-SCR compared to conventional heating, which needed less energy. For the NiMn2O4 catalyst, the catalytic efficiency exceeded 90% at 70 C and reached 96.8% at 110 C in the microwave field. Meanwhile, the NiMn2O4 also exhibited excellent low-temperature NH3-SCR reaction performance under conventional heating conditions, which is due to the high BET specific surface area, more suitable redox property, good NO adsorption-desorption in the microwave field and rich acidic sites.