Effective low-temperature catalytic methane oxidation over MnCeOx catalytic compositions

Methane is classified as one of the most dangerous air pollutant with a warming potential over 20 times higher than that of CO2. Then, methane abatement trough catalytic oxidation processes, especially using low-cost, noble-metal-free catalysts, falls in line with the most important challenges of environmental catalysis. Therefore, a series of MnCeOx composite materials, with different compositions (0.10 < χCe<0.75), have been prepared via, a facile, eco-friendly redox-precipitation route and their catalytic performance on methane total oxidation reaction were evaluated from 200 °C to 700 °C, at a space velocity of 30,000 h−1. A significant improvement of activity was observed by increasing the fraction of CeO2 in the catalytic compositions. An almost complete methane conversion (already at 600 °C) and characteristic T50 value of 475 °C were recorded with the most active catalyst (i.e. Mn-to-Ce ratio of 1:3). Bulk and surface characterization techniques provide evidence of strong synergism between the different oxide phases, favouring Mn ions dispersion at quasi-molecular level, through the incorporation of Mn2+ ions into ceria lattice, enhancing surface area and redox functionality too. The superior catalytic performance of the MnCeOx composite catalysts, especially at high χCe, is therefore associated with enhanced textural properties, along with the presence of highly dispersed manganese species and structural defects on the surface, leading to an improved “oxygen mobility” and low-temperature reducibility.