Abstract
The interaction between Ni 2+ and Mg 2+ species in Ni/MgO catalyst precursors prepared by impregnation of MgO with aqueous solutions of Ni(NO 3) 2 · 6H 2O, and the mechanism that produces Ni 2+ cations of very low reducibility after thermal treatments of the samples at low temperature are studied by temperature programmed methods (TPD, TPR) and DRIFTS and EXAFS spectroscopies. Results clearly demonstrate that during the impregnation and mild drying steps ( T ≤ 120 °C) a bulk reaction between MgO and the aqueous Ni 2+ solution yields a mixed hydroxide, where Mg 2+ and Ni 2+ cations occupy the same type of positions in a M(OH) 2 lattice with the brucite structure. NiO/MgO solid solutions are formed by decomposition of this mixed hydroxide after thermal treatments in the 250–400 °C range.
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