Preparation Of Low Temperature Cobalt-manganese Based And Twostage SCR Catalysts And The Study Of Their Denitration Performance

With the shortage of petroleum resources in China,people pay more attention to diesel vehicles because they are more economical and powerful.It is a very urgent task to reduce the NO_x emissions in diesel exhaust.Selective catalytic reduction technology?SCR?has the most promising for wide used in the field of diesel vehicle denitration.Due the wide temperature range of diesel exhaust,it is difficult for a catalyst to remove NO_x effectively,in this work,we prepared a series of LDHs precursor and Cu-SSZ-13 by co-precipitation method and hydrothermal method respectively,two kinds of materials are loaded on the surface of cordierite by coating and the honeycomb catalysts are obtained by calcination,then combined the two catalysts to obtain two-stage catalyst.The activity test of the two-stage catalysts were performed to select a SCR monolithic catalyst with good denitration performance.In this work,Ce_y/Co₁Mn_0.5Al_0.5O_x LDHs derived SCR catalysts with excellent low-temperature activity and good thermal stability were prepared by optimizing the metal ions in LDHs,the NO_x conversion of Ce_0.5/Co₁Mn_0.5Al_0.5O_x catalyst nearly 100% in 100-250 oC.Even the calcination temperature is 700 oC,it still maintained high activity.The coating rate reached 16.6 wt% when the catalyst amount was 3 g,the ratio of water: gel was 10: 4 and coated 3 times,the monolithic catalyst had the best low-temperature activity,the NO_x conversion reached 93.5% at 200 oC.Cu-SSZ-13 catalyst with good high temperature activity was synthesized by hydrothermal method,and post-treatment was used to control the Cu content.High-temperature activity of the catalyst increases with increasing ion exchange time,when the exchange time was 48 h,the NO_x conversion of the catalyst reaches 83.2% at 500 oC.By combining the two kind of monolithic catalysts,the optimal two-stage honeycomb catalyst showed the best activity in 100-500 oC,the results show that the combination of the high-temperature catalyst before the low-temperature catalyst has good performance.Ce_0.5/Co₁Mn_0.5Al_0.5O_x and Cu-SSZ-13 catalysts were characterized by XRD,BET,SEM,SO2/NH₃-TPD and H2-TPR to investigate the physical and chemical properties.Combining the two catalysts to make them work together,broaden their temperature window and provide technical support for China's diesel exhaust denitration,further promote the widespread application of diesel vehicles and sustainable development of social and economic.