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1、Carbon40(2002)481±496StructuralorderingofcoalcharduringheattreatmentanditsimpactonreactivityBoFeng,SureshK.Bhatiaaa,*,JohnC.BarrybaDepartmentofChemicalEngineering,TheUniversityofQueensland,Brisbane,Queensland4072,AustraliabCentreforMicroscopyandMicroana
2、lysis,TheUniversityofQueensland,Brisbane,Queensland4072,AustraliaReceived2October2000;accepted10April2001AbstractTheeffectofheattreatmentonthestructureofanAustraliansemi-anthracitecharwasstudiedindetailinthe850±11508CtemperaturerangeusingXRD,HRTEM,andel
3、ectricalresistivitytechniques.Itwasfoundthatthecarboncrystallitesizeinthechardoesnotchangesigni®cantlyduringheattreatmentinthetemperaturerangestudied,forboththerawcoalanditsash-freederivativeobtainedbyacidtreatment.However,thefractionoftheorganizedcarbo
4、nintherawcoalchars,determinedbyXRD,increasedwithincreaseofheattreatmenttimeandtemperature,whilethatfortheash-freecoalcharsremainedalmostunchanged.Thissuggeststheoccurrenceofcatalyticorderingduringheattreatment,supportedbytheobservationthattheelectricalr
5、esistivityoftherawcoalcharsdecreasedwithheattreatment,whilethatoftheash-freecoalcharsdidnotvarysigni®cantly.Furthercon®rmatoryevidencewasprovidedbyhighresolutiontransmissionelectronmicrographsdepictingwell-organizedcarbonlayerssurroundingironparticles.I
6、tisalsofoundthatthefractionoforganizedcarbondoesnotreachunity,butattainsanapparentequilibriumvaluethatincreaseswithincreaseintemperature,providing21anapparentheatoforderingof71.7kJmolinthetemperaturerangestudied.Goodtemperature-independentcorrelationwas
7、foundbetweentheelectricalresistivityandtheorganizedcarbonfraction,indicatingthatelectricalresistivityisindeedstructuresensitive.Goodcorrelationwasalsofoundbetweentheelectricalresistivityandthereactivityofcoalchar.Alltheseresultsstronglysuggestthatthethe
8、rmaldeactivationistheresultofacrystallite-perfectingprocess,whichiseffectivelycatalyzedbytheinorganicmatterinthecoalchar.Basedonkineticinterpretationofthedataitisconcludedthattheprocessisdiffusioncontrolled,mostlikelyinvolvingtra
