Exploring Synthesis Approaches of Co-based Catalysts for the Efficient Oxidation of CH 4 and CO

Co-based catalysts were synthesized and studied as novel oxidation catalysts, exploring and optimizing the effect of synthesis method on the redox behavior, the oxygen storage ability and thus the catalytic performance of the derived Co 3 O 4 materials in the complete CH 4 and/or CO oxidation reactions. Thus, a series of Co-based catalysts were synthesized applying either the precipitation and/or the hydrothermal method, using different precipitating agents (Na 2 CO 3 , NH 3 , urea or NaOH), Co precursor salt (nitrate or acetate) and finally varying the Co/Na ratio. In addition, the reaction time (6 or 24 h aging) was also investigated for the hydrothermally prepared Co 3 O 4 . The best catalysts for the CH 4 oxidation are the precipitated Co 3 O 4 , using cobalt acetate as precursor salt and NaOH as precipitating agent, presenting the highest surface areas and the lowest Co 3 O 4 particle sizes. On the other side, hydrothermally prepared cobalt oxides reveal higher performance for CO oxidation, with Co 3 O 4 prepared with cobalt acetate, NaOH and low aging time shown as the optimum materials. The best catalysts were further promoted with incorporation of Pd (0.5wt.%) and explored for both reactions. The addition of Pd enhanced the activity of Co 3 O 4 for CH 4 oxidation, while Pd did not improve any further the catalyst performance for CO oxidation, presenting thus the same activity with pure cobalt oxides.