Selective Catalytic Reduction Of NOx With Urea On Copper Catalysts Of Modifacated Corderite

The danger of motorcars' NOx output was more and more serious.Many scholars all over the world have been doing some research from early time,in order to improve the measures of exhaust purification.Selective Catalytic Reduction(SCR) process was most widely used.Now noble metals were not only easily poisoned but also facing the crisis of resource scarcity.Therefore,in recent years,studies with transition metals have attracted much attention.In this thesis,the cordierite honeycomb ceramics were modified by aluminum-sol appended C₆H₁₂2N₄ and Ba(ON₃)₂.The main factors which influence the specific surface area were optimized by orthogonal designed method and the surface area of carrier was 70 m²/g about 100 times lager than the former blank cordierite.The activity test indicated that the catalytic activity was improved under large air speed and low temperature.A sery of corderite supported CuO with different metal oxide was prepared by impregnation and their catalytic activity in selective catalytic reduction was systematically investigated by using the method of temperature progressing while urea was used as reductant.The catalytic reactions were conducted in fixed-bed fluxion reactor.The high active catalyst Cu-Mn-Ni-O/Al₂O₃/CC was filtrated in mixed metal oxide catalysts of the Cu series,and its optimized preparation technic indicated that the conversion rate of NOx approximately reached to 100%when the reaction temperature was 400℃in air speed 5000h^-1 and retained more than 78%when the reaction air speed was 5000 h^-1～20000 h^-1.The effect of the addition of Ce in Cu-Mn-Ni-O/Al₂O₃/CC was also researched.The results showed that catalyst activity is improved and active tempreture is debased,the conversion rate of NOx reached 54%at 150℃in air speed 5000 h^-1,and NOx was completely converted at 300℃in air speed 5000 h^-1.The range of air speed was enlarged to 5000 h^-1～20000 h^-1,and the conversion rate was improved by 16% when the reaction air speed was 40000h^-1.The catalytic samples were characterized by BET,SEM-EDS,TPR and XPS techniques.The research results showed that the larger BET surface area and pore diameter,the more homogeneous display of catalysts on the suface of support and the more the active center was.The Cu element was also found above 50%in the surface elements of the support.In the Selective Catalytic Reduction process,the effect of the addition of Mn,Ni,Ce was also researched.The results showed that this addition could make the reduction peak move to lower temperature,accelarate the velocity of reaction and improve the reductant activity of NOx.Metal element of oxide existed in the forms of Cu(â…¡),Mn(â…¡),Mn(â…¢),Ni(â…¡) and Ce(â…£) on the surface of catalyst,respectively.