Highly Active and Stable Co3O4/ZSM-5 Catalyst for Propane Oxidation: Effect of the Preparation Method

Co3O4 supported on ZSM-5 (Co3O4/ZSM-5) catalysts were prepared by impregnation (IM), deposition precipitation (DP), and hydrothermal (HT) methods. Their catalytic performances for the total oxidation of propane were tested, and their physicochemical properties were investigated by low-temperature N2 adsorption, XRD, FT-IR absorption spectroscopy, XPS, H2-TPR, TEM, and CO chemisorption. The results show that the catalytic activity of Co3O4/ZSM-5 for propane oxidation is higher than that of 1.5 wt % Pd/ZSM-5, and the preparation methods remarkably affect the catalytic activity of Co3O4/ZSM-5. Among four Co3O4/ZSM-5 catalysts prepared by different methods, the catalyst prepared by the HT method possesses the highest catalytic activity for propane oxidation, and their catalytic activities are varied in the order of HT > DP > IM. For the Co3O4/ZSM-5 (DP) catalysts, the precipitant has an evident influence on their catalytic activities. For instance, the DP catalyst prepared with ammonium bicarbonate precipitant has a higher catalytic activity than the catalyst prepared with sodium hydroxide precipitant. The excellent catalytic activity of Co3O4/ZSM-5 (HT) may be attributed to the better reducibility of Co3+, higher Co3+ content, higher surface concentration, and fast migration of the lattice oxygen of Co3O4 on this catalyst. Furthermore, the Co3O4/ZSM-5 catalyst prepared by the HT method exhibits a high stability after being used at 500 °C for 40 h.