Effects of La2O3 contents on the Pd/Ce0.8Zr0.2O2-La2O3 catalysts for methanol decomposition

The catalytic behaviors of Pd (1.4 wt.%) catalysts supported on CeO2-ZrO2 promoted with La2O3 were investigated for methanol decomposition. The measurements of inductively coupled plasma emission spectroscopy (ICP), N2 adsorption-desorption (BET), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR) and oxygen storage capacity (OSC) were used to characterize the properties of catalysts. The catalysts′ activities were tested in a fixed bed continuous flow reactor operating under atmospheric pressure. The Pd/Ce0.sZr0.2O2-5 wt.%La2O3 catalyst exhibited the best activity. The reasons for this were twofold: (1)doping of La improved effectively textural properties of CeO2-ZrO2 oxygen storage materials, and (2) Pd/Ce0.8Zr0.2O2-5 wt.% La2O3 possessed super oxygen storage property and reducibility due to the existence of lattice defect oxygen or mobile oxygen, which helped to re-oxidize zerovalent Pd0 to a partly oxidized Pdδ+. By introducing 5 wt.%La2O3, the specific surface area of the sample increased, but declined if further increasing the content of La2O3 to 10 wt.%.