Redox equilibria in zeolites

The interaction between hydrogen and zeolites containing different reducible cations (Ni2+, Cu2+, Ag+) has been investigated at temperatures between 280 and 400 °C. The first stage of this interaction ‐ leading to a reduced state of the cations in the solid ‐ can be reversed in all systems investigated. The inner‐crystalline equilibrium between Ni2+ and reduced nickel in the solid follows approximately the mass action law, the degree of reduction depending on the hydrogen pressure. A subsequent slow recrystallization of reduced nickel into larger particles outside the zeolite was observed in certain systems.