Oxidative steam reforming of ethanol over M La CeRuO (M = Mg, Ca) catalysts: effect of alkaline earth metal substitution and support on stability and activity.

Alkaline earth metal substitutions on the A-site of pyrochlore oxide M La CeRuO (M = Mg, Ca) were studied as catalyst materials for oxidative/autothermal steam reforming of ethanol (OSRE/ATR). The as-prepared oxides were synthesized by a combustion method and characterized using powder X-ray diffraction (PXRD), and X-ray photoelectron and absorption spectroscopy (XPS and XAS). PXRD Rietveld analysis and elemental analysis (ICP-AES) support the formation of a pyrochlore-type structure (space group 3̄) with a distorted coordination environment. The substitution of Mg and Ca ions affects the oxidation states of Ce and Ru ions and creates oxygen vacancies, which leads to enhanced catalytic activity and reduced ethylene selectivity. A long-term stability test showed optimized catalysts MgLaCeRuO and CaLaCeRuO with = 101(1)% and = 91(2)% under OSRE conditions. The initial operation temperatures were lower than that of the unsubstituted catalyst LaCeRuO . Catalysts supported on LaZrO showed stable OSRE/ATR performance and low carbon deposition compared to catalysts supported on AlO. We ascribe the enhanced activity to well-dispersed alkaline earth metal and Ru ions in a solid solution structure, synergistic effects of (Mg, Ca)/Ce/Ru ions, and a strong catalyst-support interaction that optimized the ethanol conversion and hydrogen production.