Enhanced low-temperature catalytic activity and stability in methane combustion of Pd−CeO2 nanowires@SiO2 by Pt dispersion

Abstract

The long-standing contradiction between low-temperature activity and high-temperature stability is one of the difficulties in catalytic combustion of low-concentration methane. The traditional Pd−CeO catalyst system has been applied to the oxidation of methane with low concentrations. However, the problem of sintering at high temperatures still exists. In this work, we prepared the Pt-modified Pd−CeO nanowires (NW) sample (in which the actual Pt, Pd, and Ce contents were 0.12, 0.86, and 9.8 wt%, respectively) using the one-pot reverse-micelle emulsion method. It was found that Pt-Pd−CeONW@SiO showed the highest low-temperature catalytic activity at a space velocity of 20,000 mL/(g h) and the best water resistance and high-temperature stability in the combustion of methane. The and (the temperatures for achieving methane conversions of 50 and 90 %) were 298 and 342 ℃, respectively, methane reaction rate at 270 ℃ was 0.49 μmol/(g s), and turnover frequency (TOF) at 270 °C was 0.198 s over Pt-Pd−CeONW@SiO; whereas over Pd−CeONW@SiO (in which the actual Pd and Ce contents were 0.82 and 10.6 wt%, respectively), the and were 360 and 420 ℃, respectively, methane reaction rate at 270 ℃ was 0.074 μmol/(g s), and TOF at 270 °C was 0.032 s. The introduction of the highly dispersed Pt to Pd−CeONW@SiO could effectively increase the PdO sites of unsaturated coordination through the electron-donating interaction of the Pt with PdO, which played an important role in activating the C−H bonds in methane. In addition, the unique structure of encapsulation also rendered the Pt-Pd−CeONW@SiO sample to possess good water resistance and thermal stability in methane combustion. We are sure that the present work provides a possibility for developing the catalysts with stable catalytic and water-resistant performance at low and high temperatures in the combustion of methane.