Ruthenium substituted pyrochlore metal oxide catalysts Y₂Ce_2-xRu_xO_7-δ (x = 0–0.4) for oxidative steam reforming of ethanol

Metal oxides Y₂Ce_2-xRu_xO_7-δ (x = 0–0.4) with partial substitution of Ruⁿ⁺ cations in the host structure were synthesized to study their catalytic activity on oxidative steam reforming of ethanol (OSRE). The samples were characterized using X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and temperature-programmed reduction (TPR). The performances investigated by varied temperatures, Ru ion content, carbon-to-oxygen ratios and long-term stability. The lowest activation temperature on OSRE is 300 °C, which is significantly lower than that of La₂Ce_2-xRu_xO_7-δ (400 °C). The cell dimension of Y₂Ce_2-xRu_xO_7-δ was reduced compare to La₂Ce_2-xRu_xO_7-δ for the replacement of the Y³⁺ ion with La³⁺ ion. The reduced unit cell in the host structure not only increase the surface composition of the Ce⁴⁺ ions, but also induce the synergetic effect of Ruⁿ⁺/Ru⁴⁺ (n > 4) and Ce⁴⁺/Ce³⁺, which lead to the enhanced OSRE activity. The optimized catalyst Y₂Ce_1.6Ru_0.4O_7-δ showed selectivity of hydrogen S_H2 = 84(4)% (Y_H2 = 2.5(1) mol/mol EtOH) and carbon monoxide S_CO = 48(1)% for long-term stability test at T = 300 °C, C/O = 0.5, and O₂/C₂H₅OH = 1.5.