Fabrication of Cobalt-Doped Ceria Nanorods for <i>p</i>-Xylene Deep Oxidation: Effects of Cobalt Precursor and Loading

Abstract

In this work, a series of cobalt-doped ceria nanorods have been synthesized coming from two cobalt precursors by the impregnation method, based on ceria nanorods pre-formed by the hydrothermal method. The properties of obtained catalysts were investigated by various techniques, including Brunauer-Emmett-Teller nitrogen physisorption measurements (BET), X-ray powder diffraction (XRD), hydrogen temperature-programmed reduction (H2-TPR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The catalytic activities of as-prepared samples were studied in the deep oxidation of p-xylene at low temperatures (225–300°C). The catalyst characterizations evidenced the crystalline phase formations of CeO2 and Co3O4 with the average crystallite sizes of 17.5–45.8 nm and 11.1–23.4 nm, respectively. The cobalt addition by cobalt nitrate into CeO2 decreased the surface area of CeO2 nanorods (67.9 m2.g−1), in contrast to the increase using cobalt acetate (76.0–82.5 m2.g−1). Co3O4/CeO2 catalysts showed reduction peaks at much lower temperatures than that of pure nanorod ceria. 7.5 mass% Co3O4 supported on nanorod CeO2 catalyst synthesized from cobalt acetate as a type of cobalt precursor with the smallest nanoparticle size and high BET surface area was the most efficient for p-xylene deep oxidation, achieving more than 95% of p-xylene conversion to CO2 at 275°C, and its performance was stabilized for more than 100 hours tested.