Ruthenium substituted pyrochlore metal oxide catalysts Y2Ce2-xRuxO7-δ (x = 0–0.4) for oxidative steam reforming of ethanol

Abstract

Metal oxides Y2Ce2-xRuxO7-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 La2Ce2-xRuxO7-δ (400 °C). The cell dimension of Y2Ce2-xRuxO7-δ was reduced compare to La2Ce2-xRuxO7-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 Y2Ce1.6Ru0.4O7-δ showed selectivity of hydrogen SH2 = 84(4)% (YH2 = 2.5(1) mol/mol EtOH) and carbon monoxide SCO = 48(1)% for long-term stability test at T = 300 °C, C/O = 0.5, and O2/C2H5OH = 1.5.