Preferential Oxidation of Carbon Monoxide in Hydrogen Stream over Au/MgOx−TiO2 Catalysts

A series of Au/MgO x −TiO 2 with various Mg/Ti molar ratios was prepared to study its catalytic activity for preferential oxidation of carbon monoxide in hydrogen-rich stream (PROX). An incipient wetness impregnation method was used to prepare the MgO x −TiO 2 support, using aqueous solutions of Mg(NO 3 ) 2 on TiO 2 calcined at 300 °C. A deposition−precipitation (DP) method was utilized to prepare Au/MgO x −TiO 2, using HAuCl 4 as the starting material. Au/MgO x and Au/TiO 2 were also included for comparison. Investigation was carried out to study the effect of Mg/Ti molar ratio on the catalytic properties of gold supported catalysts. The catalysts were characterized by inductively couple plasma-mass spectrometry, X-ray diffraction, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy. TEM results revealed the presence of nanosized gold particles and narrow particle size distribution on all the catalysts. MgO x was deposited on the TiO 2 surface in the form of thin islands without definite shape. MgO x was mainly present as Mg(OH) 2 . Au particles were deposited on the surface of TiO 2 in intimate contact with MgO x . The gold particle size was around 2.5 nm and was smaller than the MgO x particles. Since the surface area of TiO 2 was small and the MgO x concentration was comparatively higher than Au concentration, Au should be in intimate contact with MgO x on the TiO 2 surface. However, the exact status depends upon the Mg/Ti ratio and pH value during DP process to deposit gold. Au/MgO x −TiO 2 with suitable amount of MgO x has higher CO conversion and higher selectivity of O 2 to CO oxidation in the PROX reaction than Au/MgO and Au/TiO 2 .