The Preparation Of Ce/Mn-based Composite Oxides And Catalytic Performance

This thesis mainly adopts the facile synthesis at room temperature,precipitation,hydrothermal method to control and synthetic the composite metal oxides(Mn-Co-Ni-Ox,Mn-Co-Ce-Ox,Mn-Ce-Ox).On this basis,a series of characterization methods were used to explore the influence of different conditions on the synthesis of materials and the changes of various properties,and the best catalytic performance was determined by the catalytic activity test.The main contents are as follows:1.Study on the preparation of Mn-Co-Ni-Ox and its catalytic properties by facile synthesis at room temperature.In this system,hydrate manganese,potassium permanganate,hexahydrate,nickel nitrate and polyethylene glycol were used,and the product was obtained by calcination.The best performance samples were obtained by using different proportions of manganese acetate and potassium permanganate,polyethylene glycol with different molecular weight,and the samples tested at different calcination temperatures.In catalytic test,NO and CO completely transformed at 225? and 135? respectively.With different proportion of Ni doping amount,XRD,BET,TEM,H2-TPR characterization testing.Catalytic performance in the sulfur resistance and stability test is good.After adding SO2,catalyst conversion rate remained at 42%.Catalyst still maintained the original conversion after six times in cycle test,showing a good application prospect.2.Synthesis of Mn-Co-Ce-Ox catalyst by precipitation method and NO catalytic performance.Mn-Co-Ce-Ox catalyst is prepared by co-precipitation method.The nitrate of cerium and cobalt,manganese nitrate are the raw material,adding sodium carbonate solution.After stirring for 1h,the mixture is filtered and washed three times with deionized water and anhydrous ethanol.The solid dried at 60? overnight and calcined,used to test for low temperature oxidation performance of NO and CO.Under the condition of 60000 h"1,NO and CO reached 100%conversion under 185?and 105? respectively,which reflects the excellent performance of Mn0.2Co0.3Ce0 5.XRD,BET,TEM,H2-TPR,XPS and Raman are used to explore the performance of catalysts.In the resistance test,the catalyst maintained a conversion rate of 67%and recovered 82%quickly after adding SO2 and H2O,showing excellent resistance.In addition,the catalyst remained highly activity during the 24h stability test.We put forward the redox mechanism of the Mn-Co-Ce-Ox(Mn3++ Co3+(?)Mn4++ Co2+,Mn3+ + Ce4+(?)Mn4+ Ce3+),and as more Mn4+ and Co2+,more conducive to the NO oxidation.3.Synthesis of Mn-Ce-Ox catalyst by hydrothermal method and its catalytic Performance.Adding Ce(NO)3,MnCl2 and PVP in ethylene glycol,reaction kept at 160? for 8h,product was washed and dried.Catalysts were calcined with different temperatures.The core-shell catalyst has good activity for NO oxidation in medium temperature.Mn0.2CeOx reached 69.09%conversion at 350?.Catalysts has good low temperature activity in soot oxidation tests,and it can reach the highest activity in 304 ?.The catalysts were tested by XRD,BET,TEM,H2-TPR,XPS and Raman respectively to explore the catalytic performance.We believe that the catalytic performance for soot is mainly caused by the catalyst for assist of NO.NO catalytic oxidation to form the NO2,with the generation of O-jointly promote the soot oxidation,thereby increasing the way of catalytic reaction and improving the reaction rate.