Structure and kinetic investigations of surface-stepped CeO2-supported Pd catalysts for low-concentration methane oxidation.

Lamellar octahedral ceria (LOC) was synthesized by a facile hydrothermal route. The catalyst properties of Pd-supported on the as-synthesized LOC material for low-concentration methane oxidation and reaction kinetics were also investigated. The structure and morphology of samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen ad/desorption, X-ray photoelectron spectroscopy and hydrogen temperature-programmed reduction techniques. As-synthesized ceria has octahedral morphology and surface-stepped microstructures, and this unique structural CeO 2 exposes (1 1 0) crystal planes superior to general (1 1 1) facet in catalyst. The results show that LOC-supported Pd catalyst exhibits excellent low-temperature activity and stability by optimizing Pd loadings. The properties are further enhanced by introducing guest metal into the LOC material and the advantage of the Zr-modified LOC-supported Pd catalyst was confirmed by kinetic study. The optimum catalyst maintains high low-temperature activity and stability under various gas hourly space velocities, suggesting it has promising application in complete oxidation of low-concentration methane for different flow rates of ventilation air. [ABSTRACT FROM AUTHOR]