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Ceramic open cell foams (OCF) are characterized by lower pressure drop, high geometric surface area, and enhanced radial convection in comparison with monolith-type supports. In this work, silicon carbide (SiC) and zirconia (Zir) OCF with different pore per inch (ppi) density were coated with 200 mg of Co3O4 by solution combustion synthesis and doped with 3 wt % of Pd via wetness impregnation. Their catalytic activity was tested toward the lean oxidation of methane at different weight hourly space velocities. Zir OCF with 30 ppi exhibits the best catalytic activity for all reacting conditions, followed by Zir 45 ppi, SiC 45 ppi, and SiC 30 ppi. The better performance of Zir OCF was rationalized considering their lower volumetric heat exchange coefficients, which favor the reaction heat removal by convection via the flue gases. A 200 h stability test on the best structured catalyst demonstrated full methane conversion at a temperature below 400 °C. These results confirm the fundamental role of thermal conductivity of the structured catalysts’ support.

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In this work a series of cobalt spinel catalysts was synthesized by different methods and doped with 1 wt% of palladium via incipient wetness impregnation or solution combustion synthesis (SCS). Both undoped and Pd-doped spinels were characterized from the structural and surface point of view (XRD, XRF, lRS, BET, FESEM) and tested toward the oxidation of methane in lean conditions, in gas mixtures containing from 0.5 to 2 vol% of CH 4 . These methane concentrations are typical of processes involving combustion of CH 4 in lean conditions as the after-treatment of unconverted CH 4 in compressed natural gas-fed vehicle exhausts, or the treatment of fugitive CH 4 from leaks in coal mines. The temperature window for the catalytic activity of the undoped Co 3 O 4 materials spread from 350 to 600°C. The preparation method affected the catalytic activity of undoped Co 3 O 4 , with the best catalytic activity related to the spinel prepared by SCS employing urea. The addition of 1 wt% of Pd lowered the temperature window for the catalytic activity to the range of 250-500°C, with insignificant differences for the various preparation methods. The beneficial effect of Pd-doping was assigned to the enhancement of the reduction of cobalt in the oxide structure.