Pd Based Catalyst For The Selective Catalytic Reduction Of No With H₂

NO_x is one of the serious air pollutants.The removal of NO_x has attracted more and more attention.Because of the low reaction temperature and environmental friendly,H2-SCR have attracted more and more attention for the removal of NO_x.In this work,we use two approaches to modify the catalyst of H2-SCR.On one hand,we use the different preparation methods to prepare the catalyst and test the performance.On the other hand,we dope Fe into Pd/Ti02 catalyst and test the performance of Pd/FexTiy.The structure of catalysts were characterized through BET?XRD?XPS?H2-TPR etc..And we explored the reaction mechanism of H2-SCR of NO_x by In Situ diffuse reflectance infrared Fourier transform spectroscopy(in-situ DRIFTS)studies.The catalyst prepared by the ethylene glycol reducing method showed high catalytic performance for H2-SCR of NO_x.Pd/Ti02(PEG)catalyst had a good catalytic performance both fresh and used in the range of 150-350 ?with GHSV of 60000 h-1.At the same time,the selectivity of catalyst is relatively high.Pd/Ti02(PEG)catalyst has a larger specific surface area and smaller particle size.And the Pd over Pd/Ti02(PEG)catalyst is present in the form of Pd0 completely.The content of surface adsorption oxygen was very high.The polyethylene glycol reduction method increased the active sites of Pd/Ti02 catalysts and improved the performance of H2-SCR.Pd/FexTiy catalyst showed higher activity and selectivity in a relatively wide reaction temperature window.Fe and Ti of Pd/Fe1Ti1 catalyst formed solid solution and the crystallinity of Pd/Fe1Ti1 catalyst has decreased obviously.Simultaneously,there is electron transfer between Ti and Fe,which enhanced the adsorption of surface oxygen.From theH2-TPR profile it can be seen that for Pd/Fe1Ti1 catalyst the reduction peak of iron was shifted to the lower temperature,indicating that it has a good redox property,which contributes to improving the catalytic performance for H2-SCR of NO_x.In situ DRIFTS studies demontrated that variable valence transition metal Fe enhanced the number of surface active sites of the catalyst from the thus leading to the high catalytic performance.