Decomposition of N2O by Ruthenium Catalysts – RuO2 as Active Phase on Non‐Reducible Supports

Ruthenium has been supported on specifically chosen non‐reducible supports (Al2O3, SiO2, Al2O3‐SiO2 mixed oxides, Mg/ZnAl2O4 spinel, and AlF3), and these catalysts have been tested in the decomposition of nitrous oxide, N2O, to identify the catalytically active phase of ruthenium. Pure, bulk ruthenium dioxide, RuO2, and isolated Ru surface complexes have been synthesized and investigated for comparison. The catalysts were characterized by X‐ray diffraction, H2 chemisorption, N2 physisorption, temperature‐programmed reduction, and desorption (TPR/TPD) and in situ infrared spectroscopy (IR). All aimed experiments strongly indicate that the decomposition of N2O occurs on ruthenium dioxide, RuO2, instead of metal particles. H2 pre‐reduction to Ru metal has inhibitory effects for all oxygen‐containing supports. The activity increases with the dispersion of ruthenium oxide. Bulk RuO2 showed the best catalytic performance. Comparative studies of ruthenium on non‐reducible support materials for the catalytic N2O decomposition strongly indicate ruthenium dioxide RuO2 as the catalytically active species. Pure bulk RuO2 exhibits the highest catalytic activity. Higher RuO2 dispersion results in higher activity. The redox steps occur only on the active RuO2 phase's outermost surface during the reaction.