Evolution of the Nil -active centres into ex hydrotalcite oxide catalysts during the CO-free hydrogen production by methane decomposition

The preparation of three different types of mixed nickel oxides is described. These systems include: (i) the perovskite LaNiO3 oxide, (ii) a mixed-oxide derived from a hydrotalcite Ni-Al (64:38) precursor, and (iii) the spinel-type NiAl2O4 oxide. These systems were prepared with the aim of studying the activation procedure that develops small nickel nanoparticles deposited on a La2O3 or Al2O3 substrate active in H2 production through catalytic decomposition of CH4. Different preparation procedures have been applied to each precursors (i)-(iii). Perovskite-type oxide LaNiO3 was prepared by the sol-gel methodology (citrates method). Mixed oxide derived from hydrotalcite was obtained by co-precipitation using urea as a basic agent. NiAl2O4 spinel synthesis was performed by the ceramic method. The three oxide-type materials were characterized by XRD, BET specific area, TPR and XPS. Characterization results showed that the preparation methods used allow formation of highly crystalline and homogeneous oxide precursors. After activation, the oxide precursors showed a high activity in the decomposition reaction of CH4. The catalysts derived from hydrotalcite mixed oxide showed the highest activity with CH4 conversions reaching 50% at 500 8C.