Catalytic Oxidation of Methane over PdO/LnFe 0.5 Sb 1.5 O 6 (Ln = La, Ce, Pr, Nd, Sm) Catalysts

Highly efficient and stable catalysts PdO/LnFe 0.5 Sb 1.5 O 6 , Ln – La, Ce, Pr, Nd, Sm, promising in the reaction of complete methane oxidation have been obtained using the deposition–precipitation method. The catalysts contain complex oxides, which crystallize in a rosiaite-type structure (sp.gr. P 31 m ). These oxides have been used for the first time as support. The catalysts samples are characterized by a uniform distribution of PdO x particles the average size of which is 13 nm. The 90% methane conversion temperature, T 90 , for PdO/LnFe 0.5 Sb 1.5 O 6 , which were obtained without catalyst prе-activation, lie in the range of 367–382°C and does not depend on the REE ion radius. Catalytic activity dependence on the amount of supported active component is studied and the optimal content in terms of metal equal to 1 wt % Pd is found. The correlations between the synthesis conditions and catalytic activity of PdO/LnFe 0.5 Sb 1.5 O 6 are established. The catalyst PdO/LaFe 0.5 Sb 1.5 O 6 with the best catalytic characteristics is studied by X-ray photoelectron spectroscopy, IR spectroscopy, and O 2 -TPD. According to the XPS-data Pd oxidation state before and after catalytic reaction is Pd 2+ in PdO species. The promoting role of the oxide support with rosiaite structure is shown and the mechanism of CH 4 complete oxidation on PdO/LnFe 0.5 Sb 1.5 O 6 is proposed.