Enhanced propane and carbon monoxide oxidation activity by structural interactions of CeO2 with MnOx/Nb2O5-x catalysts

Abstract

A series of CeO2-MnOx/Nb2O5-x catalysts, with monoclinic Nb2O5-x (pre-calcined at 1025 °C) as the carrier, were synthesized and evaluated for catalytic oxidation of C3H8 and CO. Strong interactions between CeO2 and MnOx/Nb2O5-x were observed, and the catalyst with an optimal Mn/Ce ratio of 5.45 (1.24 wt% of CeO2) achieved 90% propane conversion at 290 °C and 90% CO conversion at 174 °C. The light-off temperature for 20% propane conversion occurred at ∼192 °C and 20% CO conversion occurred at ∼87 °C. The catalyst also showed very high stability during the long-term testing, even in the presence of water. Physicochemical characterizations and in-situ DRIFTS indicated that the addition of CeO2 greatly reduces the MnOx particle sizes, increases the dispersion of MnOx, and results in the formation of a Ce-Mn-O solid solution as well as a new Nb-Mn-Ce based phase. The interaction between Nb2O5-x and Ce-Mn mixed oxides with an optimized Mn/Ce ratio promotes the formation of oxygen vacancies and reduced species (Nb4+, Ce3+ and Mn3+), which leads to the upgrading of redox properties and enhances the ability for binding intermediates during reaction, contributing to the high oxidation activity of the catalysts.