简介：Copper（Ⅱ）oxideinvaryingratioswascombinedwitheitheranalumina-basedcement（Al300）,orCaOderivedfromlimestoneassupportmaterialinamechanicalpelletiser.Thisproductionmethodwasusedtoinvestigateitsinfluenceonpossiblemechanicalandchemicalimprovementsforoxygencarriersinchemicalloopingprocesses.Thesematerialsweretestedinalab-scalefluidisedbedwithCOorCH4asareducinggasat950°C.Asexpected,theoxygencarrierscontainingagreaterratioofsupportmaterialexhibitedanenhancedcrushingstrength.Oxygencarrierscomprisedofa1:3ratioofsupportmaterialtoactiveCuOexhibitedincreasedcrushingstrengthbyaminimumof280%comparedtopureCuOpellets.AlloxygencarriersexhibitedahighCOconversionyieldandwerefullyreduciblefromCuOtoCu.Fortheinitialredoxcycle,Al300-supportedoxygencarriersshowedthehighestfuelandoxygencarrierconversion.Thegeneraltrendobservedwasadeclineinconversionwithanincreasingnumberofredoxcycles.InthecaseofCaO-supportedoxygencarriers,allbutoneoftheoxygencarrierssufferedagglomeration.TheagglomerationwasmoresevereincarrierswithhigherratiosofCuO.OxygencarrierCu25Al75（75wt%aluminatecementand25wt%CuO）,whichdidnotsufferfromagglomeration,showedthehighestattritionwithalossofapproximately8%ofitsinitialmassover25redoxcycles.ThereducibilityoftheoxygencarrierswaslimitedwithCH4incomparisontoCO.CH4conversionwere15%-25%and50%forCu25Ca75（25wt%CuOand75wt%CaO）andCu25Al75,respectively.Cu25Ca75demonstratedimprovedconversion,whereasCu25Al75exhibitedatrendingdecreaseinconversionwithincreasingredoxcycles.

简介：Chemical-loopingcombustion(CLC)isanovelcombustiontechniquewithinherentCO2separation.Magnetite(Fe3O4)wasselectedastheoxygencarrier.Shenhuacoal(InnerMongolia,China),strawcokeandnaturalcokewereusedasfuelsforthisstudy.Influencesofoperationtemperatures,coaltoFe3O4massratios,anddifferentkindsoffuelsonthereductioncharacteristicsoftheoxygencarrierwereinvestigatedusinganatmospherethermogravimetricanalyzer(TGA).Scanningelectronmicroscopy(SEM)wasusedtoanalysethecharacteristicofthesolidresidues.Experimentalresultsshownthatthereactionbetweenthecoalandtheoxygencarrierbecomestrongatatemperatureofhigherthan800℃.Astheoperationtemperaturerises,thereductionconversionrateincreases.Atthetemperaturesof850oС,900℃,and950℃,thereductionconversionrateswere37.1%,46.5%,and54.1%respectively.However,SEMimagesshowthatatthetemperatureofhigherthan950℃,theironoxidesbecomemeltedandsintered.Thepossibleoperationtemperatureshouldbekeptaround900℃.WhenthemassratiosofcoaltoFe3O4were5/95,10/90,15/85,and20/80,thereductionconversionrateswere29.5%,40.8%,46.5%,and46.6%respectively.Withtheincreaseofcoal,theconversionrategoesup.Butthereexistanoptimalratioaround15/85.Comparisonsbasedondifferentkindsoffuelsshowthatthesolidfuelwithahighervolatileandamoredevelopedporestructureisconducivetothereductionreactivityoftheoxygencarrier.

简介：WhileFe-basedoxygencarriers(OC)areregardedtobepromisingforchemicalloopingcombustion(CLC),thedecreaseofCO2selectivityduringdeepreductionprocessandthesevereagglomerationofFe2O3oftenoccuraftermultipleredoxcyclesduetothelowoxygenmobility.Herein,Fe-substitutedBahexaaluminates(BaFexAl12–xO19,denotedasBFxA-H,x=1and2)preparedbyamodifiedtwo-stepmethodexhibitednotonlyhigheramountofconvertedoxygen(Ot)andCH4conversion(77%and81%vs.17%and75%)thanthosepreparedbythetraditionalco-precipitationmethod(BFxA-C,x=1and2)butalsohighCO2selectivityabove92%duringthenearlywholereductionfromFe3+toFe2+.Furthermore,theBFxA-Hexhibitedtheexcellentrecyclabilityduring50cycles.ThebetterperformancewasascribedtothemarkedlyenhancedoxygenmobilitywhichresultedfromdominantoccupancyofFecationsinAl(5)sites(Fe5:71%and70%vs.49%and41%)inmirrorplanesofhexaaluminateleadingtolargeramountoflatticeoxygencoordinatedwithFe5(O–Fe5)(0.45and0.85mmol/gvs.0.31and0.50mmol/g).TheimprovementofoxygenmobilityalsofavoredthepreservationofchemicalstateofFecationsinhexaaluminatestructureinthere-oxidationstep,resultingintheexcellentrecyclabilityofBFxA-H.

简介：Chemicalloopingdryreforming（CLDR）isaninnovativetechnologyforCO2utilizationusingthechemicalloopingprinciple.TheCLDRprocessconsistsofthreestages,i.e.CH4reduction,CO2reforming,andairoxidation.Spinelnickelferrite（NiFe2O4）waspreparedanditsmulti-cycleperformanceasanoxygencarrierforCLDRwasexperimentallyinvestigated.X-raydiffraction（XRD）andLaserRamanspectroscopyshowedthatapurespinelcrystallinephase（NiFe2O4）wasobtainedbyaparallelflowco-precipitatingmethod.NiFe2O4wasreducedintoFe-Nialloyandwustite（FexO）duringtheCH4reductionprocess.SubsequentoxidationofthereducedoxygencarrierwasperformedwithCO2asanoxidanttoformanintermediatestate:amixtureofspinelNi1-xFe2+xO4,Fe2+yO4andmetallicNi.AndCOwasgeneratedinparallelduringthisstage.Approximate185mLofCOwasgeneratedfor1gspinelNiFe2O4inasinglecycle.TheintermediateoxygencarrierwasfullyoxidizedintheairoxidationstagetoformamixtureofNi1+xFe2-xO4andFe2O3.Althoughtheoriginalstateofoxygencarrier（NiFe2O4）wasnotfullyregeneratedandagglomerationwasobserved,agoodrecyclabilitywasshownin10successiveredoxcycles.更多还原