Production of hydrogen by ethanol steam reforming using Ni–Co-ex-hydrotalcite catalysts stabilized with tungsten oxides

Abstract

Ni–Co/ex-hydrotalcite catalysts stabilized with tungsten oxides (WOx) were investigated in the ethanol steam reforming (ESR) reaction to produce H2. The catalyst with a Ni/Co atomic ratio of 2.22 turned out to be the best in conversion and selectivity to H2. This Ni–Co catalyst showed the highest number of small particles (<50 nm) compared to the monometal catalysts of Ni and Co. NiO was completely reduced to Ni metal and Co3O4 was partially reduced to CoO and Co. Ni metal and Co-oxide particles were supported on MgO, MgAl2O4, and Al2O3 stabilized with WOx. The addition of small amounts of W (0.5 wt%) thermally stabilized the ex-hydrotalcite oxides and Al2O3. A cooperative action between Ni and Co is observed where partially oxidized Co prevents carbon nucleation on Ni particles. The Ni–Co, Ni and Co catalysts proved to be stable in the ESR reaction with regeneration “in situ” in cyclical operation at 600 °C.