Catalytic Decomposition Of N₂O Over Ni-Based Catalysts

Catalytic decomposition is one effective method for the removal of N2O. In this work, NiO particle catalysts with different morphologies (hollow spheres, nanosheets, flower-like, nanocubes and nanorods) were prepared by different methods, and the effect of morphology of NiO on the catalytic activity for the decomposition of N2O was investigated. The hollow spheres NiO catalyst showed the highest activity among the prepared NiO catalysts. Over the NiO hollow spheres catalyst,100% conversion of N2O was achieved at 350? in the absence or presence of oxygen. The activity decreased in the order of hollow spheres> nanosheets> flower-like> nanocubes> nanorods. Different methods (BET,XRD,SEM,TEM,HRTEM,H2-TPR,XPS) have been used to characterize the above catalysts. Different morphology leads to different crystal plane exposed and different redox ability, which is closely related to the catatlytic performance of NiO catalyst for the N2O decomposition. The hollow sphere NiO catalyst with the lowest apparent activation energy is the most active catalyst.Considering that NiO showed the preferable activity for the decomposition of N2O, we futher prepared a series of Ni-M (M=Ce> Mg> Co) mixed oxides catalysts by the hydrothermal method and their catalytic activities for the decomposition of N2O have been investigated. NiCe(Ni:Ce= 8:1), NiMg(Ni:Mg= 5:1) and NiCo(Ni:Co= 1:1) mixed oxides catalysts were found to be active for the decomposition of N2O. Based on the characterization (BET, XRD, SEM, H2-TPR,XPS), it was found the NiO in Ni-M compound oxide catalysts in amorphous form,this suggests that the NiO in Ni-M compound oxide catalysts surface has good dispersion.The doping of M promote the interaction between Ni and M, thus changing the structure of Ni-M compound oxides. The content of Ni2+increased and the surface adsorption of oxygen content reduced, leading to improved redoc property. As a result, the decomposition activity of catalysts in the presence oxygen has been enhanced.