A novel Fe2O3/Al2O3 porous media catalyst prepared by ultrasonic-assisted impregnation for low-concentration methane catalytic combustion

Porous media (PM) catalytic combustion offers a potential strategy for stable and efficient combustion of low-concentration methane (LCM). Herein, a porous media catalyst loaded with Fe2O3 as the active component (Fe2O3/Al2O3) was developed by ultrasonic-assisted impregnation for LCM catalytic combustion in a four-layer porous media burner. The influences of the gas flows, velocities, equivalence ratios, and PM arrangement patterns on the temperature distribution, combustion stability, methane conversion, and emissions were investigated in detail. The results indicated that the Fe2O3/Al2O3 catalyst possessed exceptional catalytic activity and thermal stability at medium-to-high temperatures, which broadened the limiting equivalence ratio for CH4 stationary combustion to 0.43 with the CH4 conversion exceeding 99 %. LCM enabled higher combustion stability in the PM burner with a gradually varied configuration, achieving steady combustion for more than 120 min under the lean combustion condition (0.43 equivalence ratio and 50 L/min). The high-quality flue gas from LCM catalytic combustion with an average temperature over 600 ℃, lower CO (< 150 ppm) and NOx emissions (< 10 ppm) could serve for the comprehensive utilization of power generation, heating, and cooling. The catalytic oxidation of LCM on the Fe2O3 surface was primarily divided into four steps with the second-step CH4 dehydrogenation in CH4 dissociation being the dominant rate-limiting step. This work proves that the catalyst fabricated by ultrasonic-assisted impregnation can effectively break through the lean combustion threshold, which provides a valiant reference for the clean and efficient utilization of LCM.