Kinetics of the hydrogen reduction of nickel ions in silica–magnesia

Abstract

The H2 reduction of Ni2+-substituted silica–magnesia gel was studied in the ranges 613–753 K and 1.3–13 kN m–2. The reaction is slow and requires an activation energy of 174 ± 20 kJ mol–1. The rate varies with the hydrogen pressure up to 6.5 kN m–2. The reduction is not complete under the experimental conditions. The mechanism of the overall reaction appears to comprise a nucleation process together with the migration of Ni2+ ions and desorption of the water formed.