Abstract: Nanostructured LaCo_1-xZn_xO₃ (x = 0, 0.05, 0.1, 0.2, 0.3 and 0.5) perovskites were synthesized by a one-step citric acid-complexing method for hydrogen production by the steam reforming of ethanol. For comparison, 8% CoO/ZnO and 8% CoO/La₂O₃ were prepared by impregnation and evaluated. The catalyst samples were characterized by X-ray diffraction, temperature-programmed reduction, and X-ray photoelectron spectroscopy. The results indicated that zinc did not favor the formation of the LaCo_1-xZn_xO₃ perovskite and the structures of the substituted samples were stronger than that of LaCoO₃. Some segregation was observed for x ≥ 0.1. The reactivity of the studied samples was sensitive to the zinc content and lower substitution values were found to be better. An unexpected phase (Co₃O₄) appeared in the fresh LaCo_0.9Zn_0.1O₃ sample. The presence of the Co₃O₄ phase increased the reactivity toward hydrogen production by the steam reforming of ethanol. The presence of La₂O₂CO₃ is responsible for the low carbon deposition and the CH₄ selectivity in the aged samples.

Key words: one-step citric acid-complexing method, perovskite, multiple nanosized-cores, zinc, ethanol, steam reforming, carbon deposition