Ordered mesoporous Co3O4 (3D) and the bulk counterpart Co3O4 (B) were prepared by a nanocasting route and precipitation method, respectively. Pd was next loaded on both of them by an impregnation method. All catalysts were tested for the total oxidation of o-xylene in the temperature range of 150-300 C. Mesoporous Co3O4 (3D) exhibited better activity than Co3O4 (B), and Pd addition further improved the catalytic activity of both the mesoporous and bulk Co3O4. The BET and TEM results indicated that the mesoporous catalysts had uniform channel dimensions and the mesostructure was little affected by Pd addition. The TPR and XPS data indicated that Pd was much more exposed on the surface of Co3O4 (3D) than that of Co3O4 (B). TPD results showed that Pd/Co3O4 (3DL) could activate the oxygen species more easily than Pd/Co3O4 (BL). Therefore, Pd/Co3O4 (3DL) presented the best activity among the four catalysts and achieved 90% conversion of 150 ppm o-xylene at 249 degrees C at a space velocity of 60,000 mL g(-1) h(-1). (C) 2014 Elsevier B.V. All rights reserved.