Highly active CuO/OMS-2 catalysts for low-temperature CO oxidation

Manganese oxide octahedral molecular sieves (OMS-2) were synthesized using MnSO4 and KMnO4 as precursors by a reflux method under acidic conditions. CuO/OMS-2 catalysts were prepared by an impregnation method and tested for CO oxidation. The synthesized OMS-2 molecular sieves were nanorods, with the cryptomelane-type structure. X-ray photoelectron spectra (XPS) and hydrogen temperature program reduction (H2-TPR) results indicated that the OMS-2 support contained high concentration of Mn4+ (50%) in the OMS-2 support and an interaction between CuO and OMS-2. The CuO/OMS-2 catalysts showed higher activities for CO oxidation compared with the CuO/MnOx catalyst. Among the CuO/OMS-2 catalysts, the highest reactivity was obtained on CuO15/OMS-2 catalyst, with a T90 (the lowest temperature for 90% conversion of CO) of 55 °C. The interaction between the highly dispersed CuO and OMS-2 support generates active sites for CO oxidation. CO oxidation may follow the Mars-van-Krevelen mechanism with Cu2+–O2−–Mn4+ ↔ Cu+–□–Mn3+ + O2 redox couple.