Catalytic oxidation of methane over hexaaluminates and hexaaluminate-supported Pd catalysts

Abstract An aqueous (NH 4 ) 2 CO 3 coprecipitation method, based on that of Groppi et al. [Appl. Catal. A 104 (1993) 101–108] was used to synthesize Sr 1− x La x MnAl 11 O 19− α hexaaluminates. These materials were first synthesized by alkoxide hydrolysis. This synthesis route requires special handling of the starting materials and is not likely to be commercially practical. The materials prepared by (NH 4 ) 2 CO 3 coprecipitation have similar surface areas as those prepared by the alkoxide hydrolysis method. Their CH 4 oxidation activity, measured as the temperature needed for 10% conversion of methane, is higher than those prepared by alkoxide hydrolysis. The La-substantiated material, LaMnAl 11 O 19− α , shows high surface area with 19.3 m 2 /g after calcination at 1400°C for 2 h. It is active for CH 4 oxidation with T 10% at 450°C using 1% CH 4 in air and 70 000 cm 3 /h g space velocity. The stability and activity of LaMnAl 11 O 19− α prepared by (NH 4 ) 2 CO 3 coprecipitation method is a simple and important step forward for the application of CH 4 catalytic combustion for gas turbines.