Study On The Preparation Of Mn-doped Cu-SAPO-34 Catalysts And Their Denitration Performances At Low Temperature

Nitrogen oxides（NO_x）are one of major pollutants in atmosphere,which could result in serious environmental problems.So far,the NH₃-SCR technology is the prevailing technology to eliminate NO_x and the key of the technology is the performance of SCR catalysts.Recently,the small-pore zeolites with the chazabite framework structure,such as Cu-SAPO-34 and Cu-SSZ-13,have received extensive attention due to their good catalytic denitration（de-NO_x）activities and hydrothermal stability.However,the SCR activities of small-pore zeolites at low temperature are not satisfactory,which inhibits their application in mobile source.In this work,Mn was introduced as a prompter with high de-NOx activities at low temperature to Cu-SAPO-34 zeolite to obtain high efficient SCR catalysts..Firstly,the preparation conditions of Cu-SAPO-34 catalysts were optimized.The effect of TEPA as a co-template on the de-NO_x activities of Cu-SAPO-34 catalyst was studied.The results showed that the addition of TEPA facilitated the formation of more acid sites on the surface during the preparation process,which could adsorb more NH₃species to improve de-NOx activity.Next,four Cu-SAPO-34 catalyst samples with different ratios of Cu/Al were prepared.Among these catalyst samples,0.2Cu/Al+TEPA and 0.4Cu/Al+TEPA samples behaved relatively higher SCR activity,the NO_x conversion of which was more than 90%in the range of 300～400 ^oC.But the low-temperature SCR performance was dissatisfactory,the NO_x conversion at 160 ^oC was only 50%.On the basis of study above,Mn/Cu-SAPO-34 catalyst was prepared by means of one-pot hydrothermal synthesis.It was showed that Mn O₂ on Mn/Cu-SAPO-34 catalyst could catalyze NO→NO₂ reaction and initiate a“fast-SCR”process.Hence,Mn/Cu-SAPO-34 catalyst behaved excellent de-NO_x activity at low temperature.The activity evaluation results showed that the NO_x conversion of Mn/Cu-SAPO-34 catalyst at 160^oC increased to 80%,and the N₂ selectivity in the range of 100 ^oC to 300 ^oC was more than 95%.Moreover,Mn/Cu-SAPO-34 catalyst behaved excellent H₂O and SO₂resistance:the SCR performance of catalyst was almost unaffected by the addition of5%H₂O and 10 ppm SO₂ at the reaction temperatures of 180 ^oC or 260 ^oC.Above all,Mn/Cu-SAPO-34 catalyst is a promising NH₃-SCR catalyst for catalytic de-NOx application.