Ethanol steam reforming over Ni-Fe-based hydrotalcites: Effect of iron content and reaction temperature

摘要

Ethanol steam reforming has been evaluated over nickel-iron based hydrotalcite-like compounds with Ni/Fe molar ratios of 1 and 0.5. Calcined materials have been characterized by XRD, TEM, BET and TPR. The introduction of iron leads to the formation of a mixture of Ni(Fe)O_x and spinel phase upon calcination, which results in variations of structural and catalytic properties. With a Ni/Fe ratio of 1, a remarkable improvement in catalytic activity as well as selectivity to hydrogen is observed with respect to the catalyst with Ni/Fe ratio of 0.5. This is due to the enhanced nickel dispersion, the high surface area, and small Ni° crystallite size over the Ni(Fe)O_x + NiFe_2O_4 mixture. However, a further increase in iron content leads to the formation of a low surface area spinel phase (NiFe_2O_4), which results in lower activity and faster deactivation in the reaction through Ni° sintering. The effect of reaction temperature has been evaluated over the most active catalyst (Ni/Fe = 1).