Non-isothermal reduction kinetics and mechanisms by hydrogen of CuAl spinel solid solution

Abstract

The non-isothermal reduction kinetics by hydrogen of CuAl spinel solid solution was investigated using H2 temperature-programmed reduction at different heating rates methodology. The reduction process consists of four stages in terms of the reduction degree (α), corresponding to the reduction of non-spinel Cu2+, easily reducible spinel Cu2+, hardly reducible spinel Cu2+ (I), and hardly reducible spinel Cu2+ (II). The activation energy was between 83.2 and 122.1 kJ mol−1 when α < 0.72, but increased sharply to ∼500 kJ mol−1 at α = 0.95, leading to different reduction mechanisms for these Cu2+ species. Furthermore, the phase transformation, spinel structure evolution, as well as reduction mechanism were investigated.

Keywords

• CuAl spinel solid solution
• Non-isothermal
• Reduction kinetics
• Structure evolution
• Mechanisms