Combustion of methane, ethane and propane and of mixtures of methane with ethane or propane on Pd/γ-Al2O3 catalysts

Abstract

The influence of adding ethane or propane in the feed during catalytic combustion of methane on Pd(2 wt.%)/γ-Al 2 O 3 catalyst was investigated. The addition of ethane or propane inhibits the ignition of methane. Palladium particles sinter during reaction. Palladium seems to be slightly less oxidized in presence of ethane or propane. Catalytic combustion of methane on a Pd(2 wt.%)/γ-Al 2 O 3 catalyst (♢, dotted line). Effect of the addition of increasing concentrations of ethane (500 (♦), 1000 (■), 1500 (▴) and 2000 ppm (●)) on the conversion of methane (solid lines). In a first step, the catalytic combustion of methane, ethane and propane on a Pd(2 wt.%)/γ-Al 2 O 3 catalyst was investigated. The order of reactivity of these three gases is propane > ethane > methane. In a second step, the influence of adding ethane or propane in the feed during the catalytic combustion of methane was studied. At low temperature, the addition of ethane or propane inhibits the ignition of methane. This inhibition could be explained by a competition for the surface oxygen species on the surface of palladium. At high temperature, the same competitive effect would explain the inhibition observed at high ethane concentration. In the presence of propane, a thermal effect seems to have an important role. This effect is minor in the presence of ethane. In all cases, palladium particles sinter during reaction and their surface is more oxidized after test than before running the reaction. However, when ethane or propane is added in the methane feed, palladium seems to be slightly less oxidized than in the presence of pure methane. In this last case the sintering effect seems to be more pronounced. The migration of oxygen species from the bulk seems to play an important role in the oxidation of palladium. These results support previous studies using H 2 -assisted methane combustion. Implications of the presence of ethane and propane in the combustion of natural gas are also discussed.