Enhanced methane combustion over Co3O4 catalysts prepared by a facile precipitation method: Effect of aging time

A series of Co3O4 catalysts were prepared by a facile precipitation method just changing the aging time and tested for methane combustion. It was found that the activity for the reaction increased firstly and then decreased with increasing aging time in the form of a volcano curve. The Co3O4 aged for 8 h (Co3O4-8) exhibited the best catalytic performance with the specific reaction rate (R-s) of 25.91 nmols(-1) m(-2) at 340 degrees C, which was 29.5 times than Co3O4-96 sample, although the Co3O4-8 catalyst showed the minimum BET surface area and the largest particle size. The XPS and Raman results indicated that the Co3O4-8 catalyst possessed the highest ratio of A(Tetrahedral)/A(octahedral) at the surface of the catalyst. H-2-TPR and in situ XRD results also confirmed the Co3O4-8 catalyst behaved with excellent high-temperature reduction ability. In combination with the activity performance, the Co3O4-8 catalyst had the best performance of methane combustion due to abundant active tetrahedral Co2+ cationic species. The long-term stability tests demonstrated that the step of aging in the process of preparation can improve water tolerance of Co3O4 catalyst for methane combustion. (C) 2017 Elsevier B.V. All rights reserved.