Structural and catalytic stability assessment of Ni-La-Sn ternary mixed oxides for hydrogen production by steam reforming of ethanol.

Abstract

NixLaSn trimetallic catalysts (x=5 and 15% by weight) were prepared by a coprecipitation technique by pH change and then calcined at 700°C, 850°C, 900°C and 950°C. XRD analysis of the fresh and unreduced catalysts showed the formation of crystalline phases corresponding to the pyrochlore structure La2Sn2O7 and NiO following calcination at 850°C, 900°C and 950°C. Ni3Sn and Ni3Sn2 compounds were formed under a pure hydrogen atmosphere and 650°C in the well crystallized catalyst containing the pyrochlore. This catalyst was highly active in the ethanol steam reforming reaction at 650°C, giving yield to gaseous mixtures containing hydrogen, carbon monoxide, carbon dioxide and methane. XRD analysis of the spent catalyst showed the presence of Ni3Sn2, Ni3Sn and the pyrochlore as unique phases after 80 hours of reaction time. After an initial decay, H2 yield kept stable until the end of the test. Carbon formation was observed by TEM, TG and elemental analysis. Lanthanum carbonates were also revealed by Raman spectroscopy. The highly stable biphasic structure containing Ni-Sn intermetallic compounds and the La2Sn2O7 could be the basis of catalysts for the production of H2-rich gaseous mixtures starting from bioethanol.