Complete Oxidation Of Methane On Different Metals Supported On Ceria

In recent years,with the continuous development of science and technology,the living standards have been improved.However,global environment is getting worse.Exhaust emission,one of the most serious pollution to the earth,has been identified as the criminal of haze which can be seen and global warming which can’t be seen.40%of methane released into the atmosphere comes from natural sources,while 60%of methane comes from anthropogenic sources.The content of methane in atmosphere reached 260%of the pre-industrial level.Methane,one of the greenhouse gases,is far more harmful than carbon dioxide.Thus,methane released into the atmosphere should be completely oxidized and converted into carbon dioxide,it would make a big contribution to mitigating the greenhouse effect.In the process of complete oxidation of methane,molecular oxygen can be activated by cerium oxide（CeO₂）,and metal atoms or ions can activate C-H bonds in hydrocarbons effectively.MOx/CeO₂nanocomposite is expected to combine the two advantages to achieve complete oxidation of methane at low temperature.This study introduces a catalyst with the support of CeO₂ and 4 different oxides as the catalytic phase which prepared by the deposition precipitation method.The followings are the specific research work.（1）Preparation of nanorods of cerium oxideFor cerium oxide support,mixing 0.4 mol/L Ce（NO₃）₃ solution and6 mol/L NaOH solution,the CeO₂ nanorods can be synthesis successfully by hydrothermal synthesis method under the condition of 120℃.（2）Effects of different synthetic method on complete oxidation of methanePreparing the catalyst by different synthetic methods including one-step without water,one-step with water,impregnation,deposition-precipitation,evaluating the effects of different synthetic method on complete oxidation of methane,the result reveals that catalyst prepared by deposition precipitation shows the best catalytic performance.（3）Comparison of catalytic properties of different catalysts in complete oxidation of methaneThe comparison of the catalytic performance from the catalysts supported same metal with different load percent and the catalysts supported different metal with same load percent shows that 5.0 wt%PdOx/CeO₂ was the best catalyst among all the samples.For 5.0 wt%PdOx/CeO₂ catalyst,with the reaction temperature of 250℃for starting reaction,with the reaction temperature of 4295℃for methane conversion to 50%,with the reaction temperature of 400℃for complete oxidation of methane.In the Stability test,the catalyst can still maintain good catalytic activity after 96h reaction under the reaction temperature of 400℃.In the exploratory experiment,palladium was supported on Y molecular sieve and ZSM-5 for cerium,the mixed catalyst also showed the good catalytic performance.（4）The relationship between the catalytic performance and the constitution of catalystStudying the potential synergistic effect between metal and CeO₂nanorods by analyzing the results from the H₂-TPR characterization.The palladium oxide can be reduced more easily by hydrogen comparing to other metal oxides which means PdOx/CeO₂ catalyst could provide excited oxygen during the oxidation of methane under lower reaction temperature.