Catalytic decomposition of N2O over Mg-Co and Mg-Mn-Co composite oxides

Mg-Co and Mg-Mn-Co composite oxides with different compositions were prepared by sol-gel method for N2O catalytic decomposition in the presence of oxygen. Of Mg-Mn-Co catalysts, the one with higher activity was impregnated by K2CO3 solution to make K-modified catalyst. These catalysts were characterized by X-ray diffraction (XRD), nitrogen physisorption (BET), scanning electron microscopy (SEM), temperature-programmed reduction of hydrogen (H2-TPR), and temperature-programmed desorption of oxygen (O2-TPD). The effect of preparation parameters such as compositions and potassium loadings on their catalytic activity has been investigated. The results show that K-modified catalysts exhibit better activity and higher resistance towards water in contrast to un-modified catalyst due to the weakness of surface metal-oxygen bonds. Among these catalysts, 0.02K/MgMn0.2Co1.8O4 is the most active, over which 97% and 60% conversions of N2O can be reached at 400°C after continuous running for 50 h under the atmosphere of oxygen-alone and oxygen-steam together, respectively. When the steam is switched off, the catalytic activity of 0.02K/MgMn0.2Co1.8O4 can be restored to large extent, indicating the good water-resistance of K-modified catalyst.