简介:AseriesofCe-Fe-Zr-O(x)/MgO(xdenotesthemassfractionofCe-Fe-Zr-O,x=10%,15%,20%,25%,30%)complexoxideoxygencarriersforselectiveoxidationofmethanetosynthesisgaswerepreparedbytheco-precipitationmethod.ThecatalystswerecharacterizedbymeansofX-raydiffractionandH2-TPR.TheXRDmeasurementsshowedthatMgFeO4particleswereformedandFe2O3particleswelldispersedontheoxygencarriers.Thereactionsbetweenmethanedilutedbyargon(10%CH4)andoxygencarrierswereinvestigated.SuitablecontentofCeO2/Fe2O3/ZrO2mixedoxidescouldpromotethereactionbetweenmethaneandoxygencarriers.Therearemainlytwokindsofoxygenofcarriers:surfacelatticeoxygenwhichhadhigheractivitybutlowerselectivity,andbulklatticeoxygenwhichhadloweractivitybuthigherselectivity.Amongallthecatalysts,Ce-Fe-Zr-O(20%)/MgOexhibitedthebestcatalyticperformance.Theconversionofthemethanewasabove56%,andtheselectivityoftheH2andCOwerebothabove93%,theratioofH2/COwasstableandapproachedto2foralongtime.
简介:ThetransportpropertieswerestudiedforrareearthmanganeseoxideLa0.67Cao.33Mn1-xFexO3(x=0-O.3)systems.ItisfoundthatwithincreasingFe^3+-dopingcontentx,theresistanceincreasesandtheinsulator-metaltransitiontemperature(T1M)shiftstolowertemperature.Ifthedopingcontentissmall,thetransportpropertiesmanifestmetalliccharacteristicsinthetemperaturerangeofT<T1M,whiletheywillobeyathermalactivationmodelinthetemperaturerangeofT>T1M.SuchabehaviormaybeattributedtotheFe^3+-dopingandpossibleMnionsscatteringtoelectrons.TheFe^3+dopingmayleadtotheformationofFe^3+-O^2--Mn^4+channels,whichcouldterminatethedoubleexchangeMn^3+-O^2--Mn^4+channels.TheantiferromagneticclustersofFeionsmayinducetheMnionstoscettertotheelectrons.