Catalytic combustion of methane on La-, Ce-, and Co-based mixed oxides

The purpose of this work is to report the results of an experimental study devoted to the comparison of some transition-metal mixed oxides in the catalytic combustion of methane. It deals with finding a mixture composition that decreases the combustion temperature as much as possible, which is vital in catalytic combustion to eliminate NOx formation, but also active enough at low temperatures to completely convert methane, a very stable hydrocarbon fuel. La-, Ce-, and Co-based catalysts at four different compositions were prepared by the sol-gel citrate (SGC) method and characterized by scanning electron microscopy-energy-dispersive spectrometry (SEM-EDS), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) surface area analysis. Catalytic activity tests were performed in a quartz microreactor and placed in a temperature-programmable furnace. Gaseous products were analized online by gas chromatography/mass spectrometer/thermal conductivity detector (GC/MS/TCD) at the reactor outlet. Methane conversions as a function of the reaction temperature were calculated, and light off curves for the catalysts were obtained. The comparison of the catalysts showed that the nominal composition of the most active catalyst was La_0.1 Ce_0.4 Co_1.5 O_3±δ, with a T₅₀ temperature of 390 °C.