Novel Ru−Mg−Al−O Catalyst Derived from Hydrotalcite-like Compound for NO Storage/Decomposition/Reduction

Ru−Mg−Al hydrotalcite-like anionic clay (Mg/Al/Ru 90:29:1) was successfully prepared with a constant-pH coprecipitation method. Calcination of a hydrotalcite-like precursor at 600 °C in the air gave rise to the well-mixed oxide Ru−Mg−Al−O that possesses a good dispersion of Ru species. Ru−Mg−Al−O catalyst after suitable pretreatment exhibits quite high NOxstorage capability in the temperature range of 250−400 °C, and the highest NOxstorage capability of about 220 mol g-1is obtained at 350 °C with flowing 790 ppm NO and 8% O2in N2stream. Meanwhile, the decomposition of 25−60% NO to N2as well as N2O is clearly observed on the catalyst at 300−400 °C. In situ diffuse reflectance Fourier transform (DRIFT) spectra indicate that NOxis adsorbed and stored on a catalyst mainly in the form of various coordinated nitrites/nitrates. On the basis of the NOxadsorption−desorption profiles as well as the in situ DRIFTS spectra, we have proposed a schematic outline for NOxstorage and NO decomposition. Finally, the reduction of stored NOxspecies on the catalyst by H2was carried out at 350 °C, indicating that all adsorbed NOxspecies can be readily reduced by hydrogen.