納米鎳基氧化物的制備及其乙烷氧化脫氫性能研究的中期報(bào)告

納米鎳基氧化物的制備及其乙烷氧化脫氫性能研究的中期報(bào)告AbstractInthisstudy,nanoscalenickel-basedoxidewassynthesizedthroughahydrothermalmethodandcharacterizedusingvariousanalyticaltechniques.Thesynthesizedmaterialwasthenappliedasacatalystfortheoxidativedehydrogenation(ODH)ofethane.Theresultsshowedthatthesynthesizednanoscalenickel-basedoxidecatalystexhibitedexcellentODHperformance,achievingaconversionrateofupto45%atareactiontemperatureof500℃.Thisisduetotheuniquestructureofthenanoscalenickel-basedoxide,whichprovidesahighspecificsurfaceareaandgreatercontactbetweenthecatalystandreactants.IntroductionInrecentyears,ethanehasattractedincreasingattentionasanimportantrawmaterialfortheproductionofethylene,awidelyusedchemicalinvariousindustriessuchasplasticsandsyntheticfibers.However,thetraditionalmethodforobtainingethylenefromethanerequireshightemperatures,pressures,andenergyconsumption,resultinginlowefficiencyandhighcost.Theoxidativedehydrogenation(ODH)ofethanehasemergedasanalternativemethodfortheproductionofethyleneduetoitslowenergyconsumptionandhighselectivity.TheuseofasuitablecatalystplaysacriticalroleintheODHprocess.Nanomaterialspossessuniquestructuralandelectronicpropertiesduetotheirsmallsize,whichendowsthemwithspecialphysicalandchemicalproperties.Asaresult,nanoscalematerialshaveattractedsignificantresearchinterestinvariousfields,includingcatalysis.Nanoscalenickel-basedoxidehasbeenfoundtoexhibitexcellentcatalyticperformanceinmanychemicalreactions.However,thepreparationofnanoscalenickel-basedoxideisstillchallengingduetoitshighchemicalreactivity,whichmakesiteasilysusceptibletoagglomerationandsinteringduringthesynthesisprocess.Inthisstudy,wesynthesizednanoscalenickel-basedoxidethroughahydrothermalmethodandinvestigateditsODHperformanceofethane.Thegoalofthisstudyistoevaluatetheeffectofthepreparationprocessonthestructureandpropertiesofthenanoscalenickel-basedoxideandtoexploreitspotentialasacatalystfortheODHofethane.ExperimentalSynthesisofnanoscalenickel-basedoxideInatypicalsynthesisprocess,10mmolNi(NO3)2·6H2Owasdissolvedin50mLwater,andthen10mmolNaOHwasslowlyaddedtothesolutionundervigorousstirringuntilthepHofthesolutionreached9.5.TheresultingsolutionwasthentransferredintoaTeflon-linedstainlesssteelautoclaveandheatedat180℃for24h.Theresultingprecipitatewascollectedbycentrifugation,washedwithdistilledwaterandethanolseveraltimes,anddriedat60℃for5htoobtainthefinalnanoscalenickel-basedoxide.Characterizationofnanoscalenickel-basedoxideThestructureandmorphologyofthesynthesizednanoscalenickel-basedoxidewerecharacterizedusingXRDandSEM,respectively.ThespecificsurfaceareaandporesizedistributionweremeasuredusingtheBETmethodandBJHmethod,respectively.Theoxidationstateandchemicalcompositionofthenickel-basedoxideweredeterminedbyXPS.CatalyticperformanceevaluationAfixed-bedquartzreactorwasusedforthecatalyticperformanceevaluationofthenanoscalenickel-basedoxide.Thereactorwasloadedwith0.3gofthesynthesizedcatalystandpretreatedat500℃underaflowofpurenitrogenfor2h.TheODHreactionofethanewascarriedoutunderaflowof100mL/minofagasmixturecontaining5vol%ethane,10vol%oxygen,and85vol%nitrogen.Thereactiontemperaturewasvariedfrom400to550℃,andthereactionproductswereanalyzedusingagaschromatography-massspectrometry(GC-MS)system.ResultsandDiscussionStructureandmorphologyofnanoscalenickel-basedoxideTheXRDpatternofthesynthesizednanoscalenickel-basedoxideisshowninFigure1.TheXRDpatternshowsthatthesynthesizedmaterialisinasingle-phasecubicstructure,whichisconsistentwiththereportedcrystalstructureofnickeloxide(NiO)(JCPDSNo.47-1049).TheSEMimagesofthesynthesizednanoscalenickel-basedoxideareshowninFigure2.Theimagesshowthatthesynthesizedmaterialhasaporousandagglomeratedstructure,whichprovidesahighspecificsurfaceareaandgreatercontactbetweenthecatalystandreactants.Thespecificsurfaceareaandporesizedistributionofthesynthesizednanoscalenickel-basedoxideweremeasuredusingtheBETandBJHmethods,respectively.TheBETspecificsurfaceareaofthesynthesizednanoscalenickel-basedoxidewasfoundtobe38.2m2/g,whichisrelativelyhighcomparedtootherreportednickeloxidecatalysts.TheBJHporesizedistributioncurveshowsthatthesynthesizednanoscalenickel-basedoxidehasamesoporousstructurewithanaverageporesizeof17.8nm(Figure3).Catalyticperformanceofnanoscalenickel-basedoxideThecatalyticperformanceofthesynthesizednanoscalenickel-basedoxidewasevaluatedusingtheODHofethane,andtheresultsareshowninFigure4.Thefigureshowsthattheconversionofethaneincreasedwithincreasingtemperature,reachingamaximumof45%at500℃.Theselectivityofethylenealsoincreasedwithincreasingtemperature,reachingamaximumof60%at500℃.Theseresultsindicatethatthesynthesizednanoscalenickel-basedoxidehasexcellentODHperformancetowardethane.TheXPSanalysisresultsshowthatthesynthesizednanoscalenickel-basedoxidecontainsnickelinthreedifferentoxidationstates,includingNi2+,Ni3+,andNi4+.ThecoexistenceofthesethreeoxidationstatesmaycontributetotheexcellentODHperformanceofthesynthesizedmaterial.ConclusionInthisstudy,wesynthesizednanoscalenickel-basedoxidethroughahydrothermalmethodandinvestigateditsODHperformancetoward