Effect of Ag on toluene oxidation over Ag supported wire-like MnO2 catalysts

Ag/MnO2 two-component catalysts with different loading of Ag are synthesized by liquid-phase chemical reduction and the synergistic catalytic effect mechanism for toluene oxidation is investigated. The catalytic performance is significantly affected by the addition of silver and the reaction activity is directly related to the loading amount of silver. 4% Ag/MnO2 catalyst exhibits the best catalytic performance for toluene oxidation and the complete oxidation temperature for toluene into water and carbon dioxide occurs at temperature of 220°C. More importantly, the activity at temperature lower than 200°C becomes quite high because of the interaction of Ag and MnO2. The redox ability and the amount of surface lattice oxygen in catalyst rise firstly and then drop with the increasing amount of Ag. 4% Ag/MnO2 shows the lowest reduction temperature, and gives the most amount of surface lattice oxygen and toluene desorption, therefore proper amount of Ag species is essential for the promotion of MnOx structure properties and catalytic performance. The Ag loading improves the activation of toluene molecules to be oxidized into carboxylate intermediate species, which directly causes the high activity at low temperature on 4% Ag/MnO2.