Study Of Pt Catalyst For The Performance Of Catalytic Reduction Of NO

NOx(nitrogen oxides) contains a lot of chemical compounds such as NO, NO2, NO2 and so on. They cause the photochemical smog and acid rain and they give the environment the huge destruction. To dispose nitrogen oxides, Catalytic reduction technology is supposed to be one of the most efficient methods and NH3-SCR has been a mature technique. But NH3 is also a kind of dangerous gas, it is easy to cause the safety accident and have higher requirements on the equipment when in use and cannot be applied to the moving source. So the H2- SCR gradually came into the sight of people, and under the low temperature, precious metal catalysts showed good catalytic reduction performance.The Pt catalysts have simple preparation process and high repeatability, the method has its unique advantages:(1) The Pt precursor can be reduced fully in high pressure H2 environment.(2) Propylene carbonate(PC) is non-toxic and stable as dispersing and stable agent, it can maintain Pt nanoparticles solution stable for long time.(3) Making high dispersion of Pt nanoparticles before adsorpting to supports avoid the disadvantage of non-uniform stirring.(4) There is no chlorine in the whole process.We have confirmed that the assembled Pt catalysts had perfect catalytic performance in o-chloronitrobenzene hydrogenation and VOCs catalytic oxidation, so we resarch the Pt catalysts made by adsorption method for H2- SCR reaction and discussed the relationship between catalytic performance and structural properties of catalyst. The main research contents and results are as follows:1. Catalytic reduction performance of NO over Pt/TiO2 catalystsThe Pt/TiO2 catalyst prepared by adsorption method using PC as dispersant is studied about the performance of the catalytic reduction of NO. The results show that the Pt/TiO2 catalyst has the most perfect performance in the condition of 6 %O2 volume fraction, the seven of H2 / NO mole ratio, the 120000 ml·g-1·h-1 of airspeed. The NO conversion can be 80 % at 70 ℃ and the catalysts can keep ativity at 50-220 ℃. The other supports and active components can’t show high activity under same prepare condition.To explore the influence of the acid of supports to catalysts performance, we add additives such as K2SO4, KOH to change the surface acidity of the catalysts. It is proved that the acid sites on the supports can promote H2-SCR reaction than basic sites.2. Catalytic reduction performance of NO over Pt/SiO2 catalystsThe SiO2 is chosen as support because SiO2 has great surface area to distribute active components and the more acid sites benefit the reaction. So Pt/SiO2 catalyst prapared by adsorption method is used in H2-SCR reaction compared with impregnation method to conclude the advantage of this method. The results show that the Pt/SiO2 catalysts show high catalytic activity at low temperature. It can get 80 %NO conversion as low as 58 ℃. Various characterization results show that the different preparation methods will affect the Pt particle sizes on the catalyst surface and the chemical valence states, thus influence the performance of the catalyst. There are more Pt0 species on the Pt/SiO2 catalysts. It makes Pt nanoparticles Uniform and stable and disperse on supports surface as Pt0 using PC as dispersant. It is better to contact the reactants resulting to show better low temperature catalytic ability.