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.