The reducibility of highly stable Ni-containing species in catalysts derived from hydrotalcite-type precursors

Abstract

A study was conducted on the speciation and reducibility of Ni in catalysts derived from hydrotalcite-type (HT) precursors intercalated by silicates. Silicate and nickel contents in Ni/Mg/Al HT precursors varied and the products obtained by thermal decomposition in the 773–1373 K range were characterized. Sample properties were related to the amount of silicates and nickel. The former altered the formation of the spinel-type phase and decreased the ratio between MgO and MgAl₂O₄ phases in which the active species were stabilized. On the other hand, the Ni distribution depended on the Ni-loading. Ni-containing species in the spinel phase were more abundant for high Ni-loaded catalysts, and were readily reduced by H₂ treatment at 1023 K, whereas those in the Ni_1−xMg_xO solid solution remained partially unreduced.