Promoting effect of microwave irradiation on CeO2-TiO2 catalyst for selective catalytic reduction of NO by NH3

Abstract

In this work we prepared several CeO2-TiO2 catalysts for the NH3-SCR reactionusing co-precipitation with assistance of microwave irradiation. The catalytic NH3-SCR activities over CeO2-TiO2 catalysts at low temperatures are largely enhanced by the treatment of microwave irradiation, the operation temperature window is also broadened. For better understanding the promotion mechanism, the catalyst prepared by conventional co-precipitation with and without microwave irradiation treatment was characterized with H2-TPR, NH3-TPD, XPS, XRD and BET. Microwave irradiation treatment accelerates the crystallite rate of CeO2-TiO2 catalysts, and greatly enlarges their surface area by adjusting their microstructures. The resistance to SO2 and H2O is also improved via regulating the hierarchical pore structure by the microwave irradiation. Microwave irradiation treatment can also improve the redox property and increase the acid sites over the catalyst surfaces. The result of in situ DRIFTS suggests that the microwave irradiation treatment generates more Brønsted acid sites on CeO2-TiO2-2 h catalyst, helpful in SCR reactions. XPS results show that after microwave irradiation on the CeO2-TiO2 catalysts, the surface demonstrates an elevated concentration of chemisorbed oxygen, consequently leading to better oxidation of NO to NO2. Additionally, the molar ratio of Ce3+/Ce4+ has been elevated after being treated by microwave irradiation, a vital factor in enhancing the NH3-SCR activities.