Experimental and kinetic studies on the photocatalysis of UV–vis light irradiation for low concentrations of the methane

Abstract

The photocatalytic elimination of atmospheric methane offers a potential clean strategy for fighting global warming, but methane has a high CH bond energy and is present in low concentrations. In the paper, the light intensity distribution, flow, and mass transfer characteristics of low concentration methane (20–200 ppm) in a flow-bed photocatalyst reactor were investigated. The kinetic parameters of the methane photocatalytic reaction were obtained. The 3D mathematical model was developed and validated using experimental data. Within the light intensity range of 450–1530 W/m², the kinetic rate constant, Langmuir adsorption equilibrium constant, and exponent of the reaction model were 1.41 × 10⁻¹⁰, 286.49, and 1, respectively. This study revealed that the photocatalytic efficiency could be improved by reducing the methane concentration, increasing the light intensity, or lowering the flow rate. Notably, the methane photocatalytic efficiency reached 55.88 % when $C_0$ = 20 ppm, I = 1200 W/m², and $Q_v$ = 50 mL/min. Moreover, the percentage of methane completely oxidized to carbon dioxide was higher at elevated flow rates or lower methane concentrations. These results highlight the viability of the photocatalytic removal of low-concentration methane and the utility of the established mathematical model for future engineering projects