Effect of the precipitation pH on the characteristics and performance of Co3O4 catalysts in the total oxidation of toluene and propane

Abstract

Co3O4 catalysts were prepared via carbonate precipitation at different pH, characterized using TG/DTA, FTIR, XRD, Raman, N2 adsorption and TPR techniques, and tested in the total oxidation of toluene or propane. The precipitation pH may affect the composition of the cobalt oxide precursors as well as the physicochemical properties and the performance of Co3O4 catalysts. By controlling the precipitation pH at 9.5, a Co3O4 catalyst with the smallest crystalline size, the largest surface area, the most defective structure, and the best reducibility was obtained. The activity of the as-prepared Co3O4 catalysts in the oxidation of toluene was linearly dependent on the low temperature reducibility of the oxide. Among all catalysts, Co-9.5 exhibited the highest catalytic activity (T10 = 197 °C and T90 = 244 °C), excellent cycling-stability and good durability upon long-term activity test. In propane oxidation, residual sodium at the surface of the Co3O4 catalyst had a marked poisoning effect on the catalytic performance, evidencing the importance of washing procedure upon catalyst preparation.