Pd on anionic conductive ZrO2 for low-concentration methane oxidation: Synergetic effect of plasma and catalysis

Abstract

Methane (CH4) is the second largest greenhouse gas; its emission should be controlled. A plasma reactor coupled with a catalyst was used to control CH4 emission via oxidation. Compared with the traditional catalytic process, the activity of Pd/ZrO2/Al2O3 catalyst is significantly improved, the light-off temperature (T50) is at a level of 290 °C. X-ray photoelectron spectroscopy characterization results proved that synergetic effect of plasma and catalysis on CH4 oxidation was due to the increase in the amount of lattice oxygen on zirconia after plasma oxidation and the enhancement of the oxidation of Pd0 to PdO on 1.0Pd/10ZrO2/γ-Al2O3 catalyst. An operando plasma diffuse reflectance infrared Fourier transform spectroscopy mass spectrometer was used to demonstrate that CH4 oxidation on Pd/ZrO2/Al2O3 catalyst. It was found that 1.0Pd/10ZrO2/γ-Al2O3 with plasma can efficiently promote CH4 oxidation and convert surface formate and carbonate to gaseous CO2 and H2O. The plasma-generated O atoms can react with surface H2O to yield reactive OH radicals which can obviously improve CH4 oxidation at a temperature higher than 130 °C, this finding provides important enlightenment for the development of catalysts for plasma catalytic oxidation of CH4. The mechanism of CH4 plasma-catalysis oxidation was discussed.