Activity Of Cu-ZSM-5 Catalyst And Modification Effect Of Rare Earth Elements For NO Decomposition

In the dissertation, the advance of all sorts of method in the field of eliminating the NOx emission and application status in industry is reviewed comprehensively, and the current progress situation of studies on NO decomposition reaction system is emphasized. Because of high activity of Cu-ZSM-5 catalyst for NO decomposition and instability for contamination of O2 and H2O vapor, activity of Cu-ZSM-5 catalyst and modification effect of rare earth elements for NO decomposition is studied.In this dissertation Cu-ZSM-5, Ce-ZSM-5 and Cu-Ce-ZSM-5 catalyst is prepared by the means of successive ion exchange and adjusting the acidity of exchanging solution, and their activity for NO decomposition is tested in flow reaction system. The influence of preparation condition to activity of various catalysts is studied. Combined with characterization result of XRD and inductively coupled plasma emission spectrometry (ICP) for chemical composition and bulk structure of various catalysts, the change discipline of activity of various catalysts is discussed. The conclusion of studies is listed as follows:The acid site on surface of H-ZSM-5 zeolite matrix has a certain activity for NO decomposition. To Cu-ZSM-5. temperature range active for NO decomposition reaction is between 450'C and 65l)''C.with the best activity temperature point in 550 'C.The initial activity of Cu-ZSM-5 is very high, but the activity decreases with the elongation of reaction time very rapidly. The activity of Cu-ZSM-5 decreases with the increment of space velocity. The activity of Cu-ZSM-5 zeolite increases with the increment of exchange extent of Cu. and the activity of over-exchanged Cu-ZSM-5 zeolite is best for the NO decomposition reaction. Calcination pretreatment can enhance the activity of Cu-ZSM-5 zeolite in the high temperature zone. And lowering the concentration of Cu (Ac) 2 exchanging solution will enhance the activity of as-synthesized Cu-ZSM-5 zeolite. The Cu-ZSM-5 catalyst prepared by the method of adjusting the acidity of exchanging solution has a higher Cu loading amount. So has a higher activity for NO decomposition reaction. After the introduction of Cu into the H-ZSM-5 zeolite by ion exchange method, there isn't obvious CuOx crystal formed. Cerium itself is inactive to the NO decomposition reaction, but if cerium is added as a promoter into the Cu-ZSM-5 zeolite, the temperature range of Cu-ZSM-5 zeolite active for the NO decomposition reaction will change, and the stability of Cu-ZSM-5 zeolite will be improved. The activity of Cu-Ce-ZSM-5 zeolitedecreases with the increment of space velocity. Ceium will improve the activity and stability of Cu-ZSM-5 zeolite only at the condition of Cu-ZSM-5 zeolite is over-exchanged. However, if the Cu content is comparatively low, the addition of cerium can't improve the activity of Cu-ZSM-5 catalyst.Based on the research conclusion of the dissertation, we think it is very important to study systematically the modification effect of rare earth elements to the activity of Cu-ZSM-5 zeolite for NO decomposition reaction further, and combining with dynamics experiments and modern characterization means, find out the interaction mechanism of rare earth elements with active center in Cu-ZSM-5 zeolite, for preparation of catalyst with more excellent properties and realization of the industrialization of NO decomposition reaction.