Autothermal steam reforming of ethanol over La2Ce2-xRuxO7 (x=0-0.35) catalyst for hydrogen production

Pyrochlore phases solid solutions, La₂Ce_2-xRu_xO₇ (x=0-0.35) were prepared with a sol-gel process and used as catalysts for the autothermal steam reforming of ethanol. The samples as prepared were characterized with powder X-ray diffraction (PXRD), X-ray photoelectron spectra (XPS), and temperature-programmed reduction (TPR). The XPS and TPR spectra revealed the effect of doped Ruⁿ⁺ to oxidation states of La and Ce sites. The low temperature reduction ability and relative concentration of Ce⁴⁺ ions are increased as the cell-dimension decreased. Tests of catalytic activity showed that the reforming performance of La₂Ce_2-xRu_xO₇ catalysts was affected by the Ru/Ce loading ratio. For all catalysts, partial oxidation was favored at a large C/O composition; incomplete ethanol conversion was observed for C/O≥0.7. The optimized catalyst was La₂Ce_1.8Ru_0.2O₇ with hydrogen production rate (rH2) 2.01×10^-3mols^-1g_cat ^-1 (autothermal temperature ∼600°C and 97% ethanol conversion at C/O=0.6). The catalyst exhibited stable rH2 over 26h of the reaction with ethanol conversion >95%. rH2 of the catalyst gradually decreased thereafter because LaAlO₃ started to formed and affected catalytic process. For the catalyst, the Ru ions remained well dispersed before and after the AESR reaction.