Study of ruthenium supported on Ta2O5–ZrO2 and Nb2O5–ZrO2 as catalysts for the partial oxidation of methane

Ru-based catalysts supported on Ta2O5–ZrO2 and Nb2O5–ZrO2 are studied in the partial oxidation of methane at 673–873 K. Supports with different Ta2O5 or Nb2O5 content were prepared by a sol–gel method, and RuCl3 and RuNO(NO3)3 were used as precursors to prepare the catalysts (ca. 2 wt.% Ru). At 673 K high selectivity to CO2 was found. An increase of temperature up to 773 K produced an increase in the selectivity to syngas (H2/CO = 2.2–3.1), and this is related with the transformation of RuO2 to metallic Ru as was determined from XRD and XPS results. At 873 K and with co-fed CO2 an increase of the catalytic activity and CO selectivity was found. A TOF value of 5.7 s−1 and H2/CO ratio ca. 1 was achieved over Ru(Cl)/6TaZr. Catalytic results are discussed as a function of the support composition and characteristics of Ru-based phases.