Investigation Of NO+CO Reaction Activity Over Au-Ce/AlTiO_x Catalyst

As one of the major air pollutants, NOx is the main cause of photochemical smog and acid rain, which threatens ecological environment and human health. Therefore, control and reduction of NOx become global problem to be solved. Currently the most researches on NOx elimination is NH3 selective catalytic reduction (NH3-SCR) method, which is also widely applied now. However, the research on NOx reduction by CO is relatively less. Gold was not considered to be applied to synthesize catalysts as a bulk noble metal in the past because it had been thought unreactive for chemistry properties. Since the discovery in the 1980s that finely supported nanoparticles of gold could act as catalysts for many reactions at low temperature, heterogeneous catalysis by gold catalysts started attracting much attention. In this article, we use Al2O3/TiO2 prepared by a triblock copolymer soft templated method as the support, gold was then loaded on the above mentioned AlTi oxides support by the deposition-precipitation method. The resulting sample was doped with Ce by using an impregnation method, the high dispersed nano-gold catalyst was finally obtained. The catalysts were characterized to analyze their formation and structure, and we also discussed the influence of reaction between supports and loadings to catalytic activity. The main research work and results are as follows:(1) To explore the impact of the type of supports on catalytic activity, we compared three common supports in this paper. BET measurement showed that the surface area of Al2O3/TiO2 is 349 m2/g while pore volume is 0.589 cm3/g, which is the biggest among the three types of supports and possesses the best pore structure. The following test exhibited that the catalyst supported on Al2O3/TiO2 showed the best activity for NO+CO reaction at low temperature. It was also confirmed that the catalyst which was synthesized by adding Au first showed better activity.(2) It was found that the catalyst which only loaded by gold showed low activity, the highest conversion is just 8.2%. Therefore, the rare earth metal Ce was considered to be induced in the catalyst as promoter. The addition of Ce increased the activity dramatically, the interaction between the active component and supports makes the different activity over catalysts with different Au/Ce molar ratio loaded on the same support. By further comparing the activity over catalysts with different Au/Ce ratio, it was discovered that the best Au/Ce ratio is 1:0.5. NO conversion achieved 100% at 300 ? and N2 selectivity is very high with this ratio.(3) The characterization of catalysts showed that addition of Ce promoted gold dispersion, made the active component distributed on the surface of the support more uniformly. When Au/Ce ratio is 1:0.5, interaction between active components and the support accelerated electron transfer and enhanced redox property of the catalyst, which made catalysts display the best catalytic performance with this ratio.