Selective catalytic reduction of NOx by methane over Co/ZrO2 catalysts

The effect of the preparation on the catalytic performances of Co/ZrO2 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 degreesC. All samples show a maximum NO conversion in the temperature interval 300-350 degreesC, 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 degreesC to produce an organic nitrogen-containing deposit that is known to react with NOx to form nitrogen. Compared with the reference Co-ZSM-5 catalyst, the nitrates on Co/ZrO2 samples react with methane at a higher temperature, which accounts for their catalytic performances. Copyright (C) 2001 John Wiley & Sons, Ltd.