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The effect of the preparation on the catalytic performances of Co/ZrO 2 catalysts in the selective catalytic reduction of nitrogen oxides with methane was studied. The samples were prepared by grafting and impregnation with different solutions of cobalt salts. X-ray photoelectron spectroscopy analysis showed that the cobalt oxidation state is 2+ in all samples. It was found that a high cobalt dispersion favours nitrogen selectivity, especially at temperatures below 350• C. All samples show a maximum NO conversion in the temperature interval 300-350• C, but the nitrogen selectivity decrease at this temperature range. The Fourier transform infrared spectroscopic studies showed that although the surface nitrates formed on bare zirconia are highly inert, the nitrates on cobalt particles fully interact with methane at 300• C to produce an organic nitrogen-containing deposit that is known to react with NO x to form nitrogen. Compared with the reference Co-ZSM-5 catalyst, the nitrates on Co/ZrO 2 samples react with methane at a higher temperature, which accounts for their catalytic performances.

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