The catalytic oxidation of toluene at low temperature over palladium nanoparticles supported on Alumina sphere catalysts : effects of Palladium precursors and preparation method

In this study, 1 wt.% Pd/Al2O3 sphere catalysts were prepared using the wet-impregnation (WI) and deposition-precipitation (DP) method using palladium chloride and tetraamminepalladium (II) nitrate as salt precursors. All catalysts were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier-transform infrared (FTIR) spectroscopy. The catalytic activity in toluene oxidation under gas-phase conditions was measured. The obtained results showed that metal dispersion and catalytic activity were strongly dependent on the salt precursor and method of catalyst preparation. The use of tetraamminepalladium (II) nitrate as the precursor presented smaller particle size, an enhanced dispersion and higher specific surface area. Moreover, the catalyst prepared with this precursor also showed higher catalytic activity than that prepared with palladium chloride. At 1 wt.% Pd loading, complete oxidation of toluene was achieved at 250°C. However, there was only approximately 80–90% efficient at the same temperature when the catalyst was prepared with palladium chloride as the precursor.