Perparation Of Macroporous LaMnO₃ Perovskite And Its Cataltytic Oxidation Of Methane And Toluene

At present,energy and environment are two major problems facing mankind today.As the hydrocarbon with the lowest carbon content and the highest hydrogen content,methane is an important path to promote energy production and build clean low carbon in China.As a by-product of industrial production,toluene has harmful effects on human body,skin and central nervous system.Inhalation of high concentration in a short time can lead to coma and convulsions.Catalytic combustion technology with low energy consumption and high purification efficiency is one of the effective ways to deal with both of them,and the design of suitable catalysts is an important issue in the process of catalytic combustion.Perovskite-type catalysts have attracted more and more attention due to their extensive resources and good thermal stability.In this paper,lanthanum-manganese perovskite catalyst was synthesized by colloidal crystal template method,and Pd was supported on perovskite carrier.The catalytic properties of the catalysts for methane combustion and toluene oxidation were studied by XRD,ICP,FT-IR,BET,SEM,TEM,XPS,H2-TPR,O2-TPD and evaluation of catalytic activity.Firstly,LaMnO3 perovskite was doped with Sr at site A to investigate the effect of Sr on various properties and catalytic performance of the catalyst.The results show that Sr does not destroy the original structure of perovskite,and the macroporous perovskite has a higher specific surface area.Among them,La0.6Sr0.4MnO3 catalyst has stronger redox capacity,structural stability and higher conversion of methane and toluene.Its T10,T50 and T90(Temperatures of T10,T50 and T90 at conversion rates of 10%,50%and 90%,respectively)for methane are 459?,671?,830?,and its T50,T90 for toluene are 243?,260?,respectively.The activation energy calculated based on methane combustion is 62.38KJ/mol.Therefore,La0.6Sr0.4MnO3 is selected for further study.Secondly,the B-site element Mn of La0.6Sr0.4MnO3 catalyst was replaced by the element Cu,and the effects of different contents on the properties and catalytic properties of the catalyst were investigated.The results show that the perovskite structure is not destroyed by adding Cu,and the Mn4+ content and oxygen vacancy of the catalyst are increased,and the catalytic activity is obviously improved.Among them,La0.6Sr0.4Mn0.775CU0.225O3 catalyst has the best activity performance.Its T10,T50 and T90 for methane combustion are 400?,610? and 760?,its T50 and T90 for toluene oxidation are 212? and 239?,respectively.Its activation energy is 59.93KJ/mol based on the calculation of methane combustion.Finally,La0.6Sr0.4Mn0.775Cu0.225O3 was used as the carrier to support precious metal Pd,and the effects of Pd loading on the physicochemical properties and catalytic performance of the catalyst were studied.The results show that the perovskite structure will not be destroyed after reduction and sintering,and the addition of Pd greatly improves the oxygen adsorption capacity and reduction performance of the catalyst.The strong interaction between Pd and perovskite improves the catalytic activity.Among them,1.31Pd/La0.6Sr0.4Mn0.77sCu0.225O3 has the best methane combustion activity.The T10 T50 and T90 of methane combustion are 372?,549? and 653?,respectively.The activation energy calculated based on methane combustion is 54.65KJ/mol.