Study On Nano MgO Supported Pt Based Catalyst For Removal Of NO_X By H₂-SCR At Low Temperature

NO_x are one of the significant atmospheric pollutants which is greatly harmful to human health.Pt based catalyst was widely attracted because of its high performance at low temperature in the H₂-SCR reaction.In this paper,a series of Pt/MgO,Pt-xCr/MgO and Pt/xSiO₂-MgO catalysts were prepared,and the H₂-SCR performance of these catalysts was tested in a fixed-bed reactor by simulating the reaction conditions.XRD,BET,SEM,TEM,XPS,H₂-TPD,NH₃-TPD and other characterization methods were used to characterize the structure and surface properties of catalysts.The experiment results showed that,for the Pt/MgO catalyst,the H₂-SCR performance at lower calcination temperature was better than other temperatures although the specific surface area of it was not high.The position of maximal NO_x conversion of Pt/MgO catalyst was affected by the loading amount of Pt,the position of maximal NO_x conversion of Pt/MgO catalyst was shifted from 150 ? to 100 ? with the increase of Pt content.The activity of Pt/MgO catalyst was the highest when the[H₂]/[NO] = 4,[O2] = 2%,GHSV = 10000h^-1.For the Pt-xCr/MgO catalyst,the activity and operate temperature wind of catalyst was significantly affected by the addition amount of Cr,and the best amount was 20wt%.A Cr₂MgO₄ spinel phase was formed when Cr was introduced,and Cr3+ ions in the octahedral sites was replaced by Pt⁴⁺ ions,so that the catalyst showed wonderful electron transfer capability.The redox ability of the catalyst was also affected by the amount of Cr,Cr6+ ? Cr3+ reducing ability was decreased and Cr3+ ? Cr2+ reducing capability was increased with the increase of Cr.In addition,weaker acid strength and proper acid amount was beneficial for improving the H₂-SCR performance of Pt-xCr/MgO catalyst.For Pt/xSiO₂-MgO catalyst,the addition amount of SiO₂ has a great influence on the H₂-SCR performance of catalyst,and the maximal NO_x conversion reached 93%when the amount of SiO₂ was 20%.The magnesium silicate gel was formed when the SiO₂ was added to the Pt/MgO catalyst.The formed magnesium silicate gel was benificial to improving the reductive ability of Pt/xSiO₂-MgO catalysts.Furthermore,weaker acid strength and proper acid amount was beneficial for improving the H₂-SCR performance of Pt/xSiO₂-MgO catalyst.