The Design And Preparation Of Co-Mn Catalysts For Catalytic Combustion Of Benzene

In order to prepare catalysts with low cost,high activity and stability,cobalt-manganese catalysts were synthesized by co-precipitation method in the thesis.Their catalytic performance on benzene combustion was explored.CoxMny catalysts with different molar ratios of Co/Mn,Co2Mn1 catalysts calcinated at different temperature and Ce-doped Co2Mn1 catalysts were prepared.Monolithic catalysts were further studied,whose active component was Co2Mn1.The catalytic activititis and properties of the synthesized catalysts were characterized and analyzed.The reasons for catalytic activities of different catalysts on benzene combustion were analyzed.The significant contents of the study are as follows:?1?Firstly,CoxMny catalysts with different molar ratios of Co/Mn were prepared by co-precipitation method.Catalytic activities of benzene combustion over CoxMny catalysts were compared,so that Co2Mn1catalyst was finally screened.Then a series of Co2Mn1 catalysts were prepared with the same method and at different calcination temperature.The morphologies and crystal structure of Co2Mn1 catalysts were characterized by XRD,SEM,TEM and BET.The redox capacity of Co2Mn1 catalysts was investigated by H₂-TPR and O₂-TPD.The chemical composition of Co2Mn1 catalysts was analyzed by XPS and TG-DTA.The impact of space velocity and catalyst stability were studied,too.The results showed that a series of Co2Mn1 catalysts were typical spinel-type solid solutions and the Mn were highly dispersed in Co₃O₄.A series of Co2Mn1 catalysts were with high catalytic activities and stability.Moreover,the calcination temperature had a great influence on the catalytic performance of Co2Mn1 catalysts(GHSV=30,000 mL/?g·h?,C_benzene=1000 ppm).The Co2Mn1 catalyst calcined at 300?owned the best catalytic performance.T_10%and T_90%were149?and 191?,respectively.Besides,it showed high stability.Co2Mn1?T300?catalyst which showed high catalytic performance was to do with its spinle structure,flake morphology and redox capacity and so on.?2?In the next,Ce-doped Co2Mn1 catalysts with different contents of Ce?8.6 wt%⁵5.2 wt%?,which were prepared by the above method.The calcination temperature was 300?.A variety of characterization techniques were used to characterize the morphology and structure of Co-Ce-Mn catalysts.The redox properties of the catalysts were characterized by H₂-TPR.Comparing the catalytic performance of Co-Ce-Mn catalysts with different content of Ce,it was found that Ce-doping could improve the catalytic activities of Co2Mn1 catalysts.However,when the concentration of Ce was too high,the spinel structure of Co2Mn1 was destroyed,and the catalytic performance was decreased.Ce was contributed to O_latt mobility and the concentration of O_sur.?3?In order to be used in practical application,the cordierite was selected as a carrier to prepare a monolithic catalyst that Co2Mn1 was active ingredient.Pseudo boehmite was a binder and the content of active ingredient Co2Mn1 was 12.5 wt%of the fixed solid content?the total content of pseudo-boehmite and Co2Mn1?.pH value was controlled under the preparation of the slurry.In the study,the fixed solid content?the total content of pseudo-boehmite and Co2Mn1?was 40 wt%of the slurry.When the content of active ingredient Co2Mn1?T300?was 12.5 wt%,the thickness of monolithic catalyst active coating obtained was uniform and the loading was 25 wt%.Adhesion experiments showed that the monolithic catalyst was less than 3%detached after 3 hours of ethanol sonication,mainly due to the strong interaction between the active ingredient and the carrier.The monolithic catalyst showed high activity in the benzene combustion,and at 300?benzene was completed consumed at a space velocity of 120,000 mL/?g·h?.The concentration of benzene is 1000 ppm.The 36-hour stability test also showed that monolithic catalysts have high stability.