氣體吸附理論及應(yīng)用概論

多孔物質(zhì)氣體吸附理論及應(yīng)用概論內(nèi)容簡(jiǎn)介公司介紹物理吸附和化學(xué)吸附的基本理論和方法各種吸附儀的特點(diǎn)和選擇原則?2003,QuantachromeInstruments顆粒特性分析測(cè)定儀器英國(guó)馬爾文公司激光衍射粒度分析儀0.02~3500微米500/1000Hz掃描速率激光動(dòng)態(tài)光散射分析儀1~5000納米/ZETA電位干粉/噴霧粒度分析儀在線粒度分析儀高濃度超聲粒度分析儀絕對(duì)分子量分布測(cè)定儀100~1e12Daltons美國(guó)康塔公司全自動(dòng)比表面及孔隙度分析儀

(分析站數(shù)可選1/2/3/6)>0.0005m2/g3.5~5000埃壓汞儀3.6納米~426微米孔徑化學(xué)吸附儀(TPR/TPD)流動(dòng)法快速比表面測(cè)定儀全自動(dòng)真密度計(jì)自動(dòng)堆密度分析儀?2003,QuantachromeInstruments粉體比表面和孔隙度分析_________經(jīng)典文獻(xiàn)來自QUANTACHROME?2003,QuantachromeInstruments粉體比表面和孔隙度分析_________經(jīng)典文獻(xiàn)來自QUANTACHROME2004年出版發(fā)行?2003,QuantachromeInstrumentsQUANTACHROME-1968

年由紐約長(zhǎng)島大學(xué)化學(xué)家Dr.S.Lowell教授建立-著名的當(dāng)代顆粒技術(shù)開創(chuàng)者，革新了比表面和孔隙度測(cè)量技術(shù)并設(shè)計(jì)了相應(yīng)的儀器

-康塔(Quantachrome)的儀器不僅受到科學(xué)界的青睞,而且已經(jīng)向全世界的工業(yè)實(shí)驗(yàn)室發(fā)展。

-被公認(rèn)是對(duì)樣品權(quán)威分析的優(yōu)秀供應(yīng)商,它可為實(shí)驗(yàn)室提供全套裝備及完美的粉體分析技術(shù),及最佳的性能價(jià)格比。

-康塔(Quantachrome)公司——開發(fā)粉體及多孔材料特性儀器的世界領(lǐng)導(dǎo)者,向中國(guó)用戶提供全面服務(wù)。?2003,QuantachromeInstrumentsFounded1968byDr.S.Lowell,

ProfessorofPhysicalChemistry,

LongIslandUniversity,NewYorkFirstproduct:QuantasorbSurfaceAreaAnalyzerbasedofdynamicflowmethod.Competitor:In1968Micromeritics(founded1963)wasproducingmanuallyoperatedvacuumvolumetricinstrumentwhichproduceddataveryslowly(manyhours).Quantasorbreducedsurfaceareaanalysistimetoaslittleas30minutesenablingmeasurementtobemoreeffectivelyusedinqualityandprocesscontrollabs.HistoryofInnovativeDevelopmentsforcharacterizationofpowdersandporoussolids1972Monosorb–firstdynamicflow,singlepointsurfaceareaanalyzerwithdirectsurfaceareadisplay1972Stereopycnometer–firstcommerciallyavailablegasexpansionpycnometer1978AutoscanMercuryPorosimeter–firstintroductionofcontinuousscanning/pressurization1982Autosorb-6–firstsix-port,highthroughputgassorptionanalyzersimultaneousandindependentanalysisofsixsamples1990NOVASeries–firsthighspeedsurfaceareaanalyzersthatcouldperformmeasurementswithoutheliumvoidvolumedetermination2001NLDFTforzeoliteandmicroporoussilica–firstfulllibraryofadvancedmicroporemodelsbasedonstatisticalmechanicsforadvancedmicroporesizemeasurements2003Hydrosorb–first,highspeed,vacuumvolumetricwatersorptionanalyzer–reducedanalysistimesfromdaystohours!2004Quadrasorb,firstbenchtop,economicallypricedmulti-stationgassorptionanalyzerwithindependentstations.?2003,QuantachromeInstrumentsQuantachrome’sHeadquarters,

BoyntonBeach,Florida,USAQuantachromeCorporationisdedicatedtoprovidingthehighestqualityparticlecharacterizationinstrumentationwhilemaintainingresponsivecustomerserviceandsupport.Quantachrome’sMissionQuantachromePeopleDr.MartinThomas,Director,AppliedTechnologyhasmorethan20yearsprofessionalexperienceinthefieldofparticlecharacterization,13withQuantachrome.HegainedhisPhDfromtheUniversityofBirmingham’sSchoolofChemistry(UK)ashedidhisMastersdegreeinAnalyticalChemistry.HisindustrialexperiencepriortojoiningQuantachromeInstrumentsin1991wasatCooksonGroup’scentralresearchlabandICI’sCatalysisResearchCenter(nowJohnsonMattheyCatalysts).DrThomashashadpublished7peer-reviewedpapersandoneUSpatent,plusanumberofotherarticlesandposters.Heisajointauthorofanewbook(CharacterizationofPorousSolidsandPowders)tobepublishedAugust2004.DrThomasisactiveonanumberofASTMcommitteesandlecturesoccasionallyfortheCenterforProfessionalAdvancement.KeyContactsforInternationalDistributorSupport:?2003,QuantachromeInstrumentsQuantachromePeopleDr.MatthiasThommes,Director,AppliedScience:DoctoralThesisinPhysicalChemistryatRuhr-UniversityBochum(1989-1991)andTechnicalUniversityBerlin,Germany(1992/93).Morethan30publications(andinvitedreview-articles)inref.journalssuchasJournalofPhysicalChemistryB,Langmuir,JournalofChemicalPhysics,AppliedSurfaceScience,Carbon,StudiesinSurfaceScienceandCatalysiset..

Since2001,morethan33presentations(atleast28oralpresentations)andinvitedseminarsatinternationalconferences,symposiaanduniversitiesallovertheworldProfessionalAffiliations:InternationalAdsorptionSocietyAmericanInstituteofChemicalEngineersAmercianChemicalSocietyAmericanSocietyforTestingandMaterials(ASTM)MemberoftheUS-delegationtoworkintheISO(InternationalStandardOrganization)Committee?2003,QuantachromeInstrumentsQuantachromePeopleMr.JeffDixon,InternationalSalesManagerOver10yearsprofessionalexperienceinparticle/porousmaterialscharacterization.JoinedQuantachromeinOctober2003after8+yearswithPMI(alsoinporousmaterialscharacterization)Involvedinthedesignandengineeringofnewporousmaterialscharacterizationtechnologies/instrumentsincludinggasflowtechniques,diffusionpermeametry,watervaporsorption,waterintrusionporosimetry,membranecharacterization.AtQuantachrome:responsibleforInternationalsalesnetwork,applicationsupport,newproductdesignandengineering.ProfessionalAffiliations:ASTMEDANA,TAPPI,INDA(papers,nonwovens).?2003,QuantachromeInstrumentsQuantachromePeopleDr.JacekJagiello,Manager,ApplicationSupportandTraining.Adsorptionspecialistwithspecialinterestinunderstandingandcharacterizationofactivatedcarbons.DoctoratefromM.Curie-SklodowskaUniversity,Lublin,Poland(1994.PostdoctoralresearchassociateatCNRS,Mulhouse,Francefrom1998to1990.PostdoctoralresearchassociateatSyracuseUniversity,NewYorkfrom1990-1996.From1996-2000intheCarbonResearchGroupofWestvacoCorporation(Charleston,SouthCarolina)Authorandco-authorofmorethan80scientificpublicationswithnumerousinternationalpresentationsandfourUSpatents.?2003,QuantachromeInstrumentsQuantachromePeopleMarkContessa,ServiceManagerMarkbeganhiscareerwitha4yeartermintheUSNavywherehegainedexperienceinelectronics.Markworkedfor10yearsforamajorUSdefensecontractor.JoinedQuantachromeover12yearsago,andhasheldthepositionofServiceManager.Markisresponsibleforallareasofservice,andmanagesateamoffieldserviceengineers.Markhastraveledextensively,including2tripstoChina.?2003,QuantachromeInstrumentsQuantachrome

Firsts

Quantachromehasseveralachievementswhichare:a)DevelopmentoftheMonosorb?,thefirstsingle-point,dynamicflowB.E.T.surfaceareainstrumentb)Developmentofa“continuousscanporosimetry”, utilizedinthePoremaster?poresizeanalyzersc)Developmentofthefirst“commerciallyviable”gaspycnometersd)DevelopmentoftheAutosorb-6?,thefirstmulti-station surfaceareaandporesizeanalyzerwiththeability toconductsimultaneousandindependent measurements?2003,QuantachromeInstrumentsDevelopmentofthefirst“commerciallyviable”gas-expansionpycnometers!AQuantachrome?First!DevelopmentoftheMonosorb?,thefirstsingle-point,dynamic-flowBETinstrumentwithdirectsurfaceareareadout!AQuantachrome?First!Developmentofthepatentedcontinuous-scanningmercuryporosimetersutilizedintheQuantachromePoreMaster?poresizeanalyzers!AQuantachrome?First!DevelopmentoftheAutosorb?-6,thefirstmulti-stationsurfaceareaandporesizeanalyzerwiththeabilitytoconductindependentandsimultaneousmeasurements!AQuantachrome?First!NOVAe系列全自動(dòng)比表面及孔隙度分析儀時(shí)尚流線型外觀設(shè)計(jì)操作空間加大歧管死體積減小1.7ml杜瓦工作時(shí)間延至30小時(shí)/次4個(gè)脫氣站和4個(gè)分析站，可同時(shí)進(jìn)行8個(gè)樣品的處理和分析符合美國(guó)FDA21CFRPart11標(biāo)準(zhǔn)?2003,QuantachromeInstrumentsQUADRASORBSI全自動(dòng)4站比表面和孔隙度分析儀?2003,QuantachromeInstrumentsAutosorb-1MP微孔型高端比表面和孔隙度分析儀具有五個(gè)壓力傳感器和一個(gè)液位傳感器極限真空達(dá)10-10mmHgBET比表面微孔,介孔和大孔的孔徑分布微孔體積和面積氪吸附測(cè)超低比表面CO2andH2吸附研究蒸汽吸附?2003,QuantachromeInstrumentsRifflersRotaryMicroRiffler?InstrumentsforRepresentativeSamplingSpinningrifflersforaccuraterepresentativesamplingofpowdersandgranularmaterial.Operatorselectablefeedrateandcollectorrotationspeed.Maximumcapacity:RotaryMicroRiffler/120ccSievingRiffler/2500ccSievingRiffler?多孔材料的物理吸附理論分析背景知識(shí)吸附理論孔隙度測(cè)量評(píng)注及結(jié)論?2003,QuantachromeInstruments多孔材料的應(yīng)用?2003,QuantachromeInstruments孔隙度?2003,QuantachromeInstruments

什么是表面積?

SurfaceArea–whatisit?“表面是固體與周圍環(huán)境,特別是液體和氣體相互影響的部分;表面的大小即表面積.”“SurfaceAreaisthemeansthroughwhichasolidinteractswithitssurroundings,especiallyliquidsandgases.”表面積可以通過顆粒分割(減小粒度)和生成孔隙而增加.Surfaceareaiscreatedbydivisionofparticles(sizereduction)andthegenerationofporosity.表面積可以通過燒結(jié),熔融和生長(zhǎng)而減小.Surfaceareaisdestroyedbysintering(exceedingTg),meltingandOstwaldripening.?2003,QuantachromeInstruments為什么表面積如此重要?

SurfaceArea–Importance?請(qǐng)記住:表面積是固體與周圍環(huán)境,特別是液體和氣體相互作用的手段和途徑.Rememberthatsurfaceareaisthemeansthroughwhichasolidinteractswithitssurroundings.

考慮下列三種作用:Considerthefollowingthreeinteractions:固體-固體:自動(dòng)粘結(jié),流動(dòng)性(流沙),壓塑性Solid-Solid:autohesiveness(cohesiveness)egflow,compactibilityetc.固體-液體:浸潤(rùn),非浸潤(rùn),吸附能力等Solid-Liquid:wetting,non-wetting,adsorptioncapacityetc.固體-氣體:吸附,催化等Solidgas:adsorption,catalysis,etc.?2003,QuantachromeInstruments孔的類型交聯(lián)孔(開孔)閉孔盲孔(開孔)通孔(開孔)?2003,QuantachromeInstruments孔形的分類筒形孔筒形孔錐形孔裂隙孔球形孔(墨水瓶孔)?2003,QuantachromeInstruments孔徑的分類

(IUPACStandard)

?2003,QuantachromeInstruments表面積測(cè)定方法

Suitablemethodsofdetermination氣體吸附法是測(cè)量所有的表面,包括不規(guī)則的表面和開孔內(nèi)部的面積.

Gasadsorptionallowsprobingofentiresurfaceincludingirregularitiesandporeinteriors.吸附量是溫度,壓力和親和力或作用能的函數(shù).

Theamountadsorbedisafunctionoftemperature,pressureandthestrengthofattractionorinteractionpotential.

物理吸附一般是弱的可逆吸附.固體必須被冷卻,并且確定一種方法從可能的單分子覆蓋中計(jì)算表面積.

Physisorptionisgenerallyweakandreversible.Thesolidmustbecooledandamethodusedtoestimatethemonolayercoveragefromwhichsurfaceareacanbecalculated.?2003,QuantachromeInstruments孔隙度測(cè)定方法

----氣體吸附法僅測(cè)量開孔有效范圍:0.4-50nm容易操作成熟技術(shù)?2003,QuantachromeInstruments孔隙度測(cè)定方法

----壓汞法類似于氣體吸附僅測(cè)量開孔有效范圍:>3.6nm容易操作成熟技術(shù)?2003,QuantachromeInstruments孔隙度測(cè)定方法

----透射電鏡提供有關(guān)孔交聯(lián)信息如果材料含有有序孔,則可正確反映孔徑幾乎不用于孔分析?2003,QuantachromeInstruments孔隙度測(cè)定方法

----掃描電鏡孔徑:>5nm幾乎不用于孔分析?2003,QuantachromeInstruments孔隙度測(cè)定方法

----小角X-射線掃描法任何孔徑用于開孔+閉孔的孔分析?2003,QuantachromeInstruments孔隙度測(cè)定方法

----小角中子散射法(SAN)任何孔徑用于開孔+閉孔的孔分析價(jià)格昂貴?2003,QuantachromeInstruments

吸附原理

?2003,QuantachromeInstruments固體材料對(duì)氣體的吸附現(xiàn)象1、化學(xué)吸附--是氣體分子與材料表面的化學(xué)鍵合過程只發(fā)生單層吸附選擇性吸附(特定氣體主要H2,CO,O2對(duì)體系中各組分的特定吸附)2、物理吸附--是由范得華力引起的氣體分子在固體表面及孔隙中的冷凝過程可發(fā)生單層吸附,多層吸附非選擇性吸附氣體分子在固體表面的吸附機(jī)理極為復(fù)雜，其中包含化學(xué)吸附和物理吸附?2003,QuantachromeInstruments物理吸附和化學(xué)吸附的比較?CopyrightQuantachromeCorporation2000.Allrightsreserved.氣體吸附過程靜態(tài)描述吸附物吸附物多層飽和吸附隨機(jī)性非飽和吸附單層飽和吸附可計(jì)算比表面積可計(jì)算總孔容積?2003,QuantachromeInstruments氣體吸附通過固體表面上氣體吸附量多少來計(jì)算粉體或多孔固體的比表面積比表面積的測(cè)量包括能夠到達(dá)表面的全部氣體，無論外部還是內(nèi)部。?CopyrightQuantachromeCorporation2000.Allrightsreserved.氣體吸附一般而言，在范德華力作用下，固體吸附氣體是弱鍵作用。為了使足夠氣體吸附到固體表面，測(cè)量時(shí)固體必須冷卻，通常冷卻到吸附氣體的沸點(diǎn)。通常氮?dú)庾鳛楸晃轿?，因此固體被冷卻到液氮溫度(77.35K)?CopyrightQuantachromeCorporation2000.Allrightsreserved.氣體吸附過程4)?CopyrightQuantachromeCorporation2000.Allrightsreserved.吸附等溫線在密封容器中，某種材料在特定溫度下對(duì)氣體的吸附量與吸附平衡后的壓力有其特殊的對(duì)應(yīng)關(guān)系III0P/P01.0IV0P/P01.0V0P/P01.0II0P/P01.0IIIVVVV0P/P01.0V?2003,QuantachromeInstrumentsVeryLowpressurebehavior(microporefilling)?2003,QuantachromeInstrumentsLowpressurebehavior(monolayer)The“knee”?2003,QuantachromeInstrumentsMediumpressurebehavior(multilayer)?2003,QuantachromeInstrumentsHighpressurebehavior(capillarycondensation)?2003,QuantachromeInstrumentsSchematicillustrationofthesorption,porecondensationandhysteresisbehaviorofafluidinasinglecylindricalmesopore?2003,QuantachromeInstruments具有微孔的氮吸附等溫線?2003,QuantachromeInstruments由國(guó)際純粹與應(yīng)用化學(xué)聯(lián)合會(huì)（IUPAC）提出的物理吸附等溫線分類?2003,QuantachromeInstrumentsI型等溫線的特點(diǎn)在低相對(duì)壓力區(qū)域，氣體吸附量有一個(gè)快速增長(zhǎng)。這歸因于微孔填充。隨后的水平或近水平平臺(tái)表明，微孔已經(jīng)充滿，沒有或幾乎沒有進(jìn)一步的吸附發(fā)生。達(dá)到飽和壓力時(shí)，可能出現(xiàn)吸附質(zhì)凝聚。外表面相對(duì)較小的微孔固體，如活性炭、分子篩沸石和某些多孔氧化物，表現(xiàn)出這種等溫線。?2003,QuantachromeInstrumentsII型和III等溫線的特點(diǎn)II型等溫線一般由非孔或大孔固體產(chǎn)生。B點(diǎn)通常被作為單層吸附容量結(jié)束的標(biāo)志。III型等溫線以向相對(duì)壓力軸凸出為特征。這種等溫線在非孔或大孔固體上發(fā)生弱的氣－固相互作用時(shí)出現(xiàn)，而且不常見。?2003,QuantachromeInstrumentsIV型等溫線的特點(diǎn)IV型等溫線由介孔固體產(chǎn)生。典型特征是等溫線的吸附曲線與脫附曲線不一致，可以觀察到遲滯回線。在p/p0值較高的區(qū)域可觀察到一個(gè)平臺(tái)，有時(shí)以等溫線的最終轉(zhuǎn)而向上結(jié)束(不閉合)。?2003,QuantachromeInstrumentsV和VI型等溫線的特點(diǎn)V型等溫線的特征是向相對(duì)壓力軸凸起。V型等溫線來源于微孔和介孔固體上的弱氣－固相互作用，而且相對(duì)不常見。VI型等溫線以其吸附過程的臺(tái)階狀特性而著稱。這些臺(tái)階來源于均勻非孔表面的依次多層吸附。這種等溫線的完整形式，不能由液氮溫度下的氮?dú)馕絹慝@得。?2003,QuantachromeInstruments遲滯回線類型?2003,QuantachromeInstruments遲滯回線類型

按照IUPAC

13.2節(jié)中的約定，劃分出了4種特征類型H1型遲滯回線可在孔徑分布相對(duì)較窄的介孔材料，和尺寸較均勻的球形顆粒聚集體中觀察到。?2003,QuantachromeInstruments遲滯回線類型

按照IUPAC

13.2節(jié)中的約定，劃分出了4種特征類型H2型遲滯回線由有些固體，如某些二氧化硅凝膠給出。其中孔徑分布和孔形狀可能不好確定，比如，孔徑分布比H1型回線更寬。?2003,QuantachromeInstruments遲滯回線類型

按照IUPAC

13.2節(jié)中的約定，劃分出了4種特征類型H3型遲滯回線由片狀顆粒材料，如粘土，或由裂隙孔材料給出，在較高相對(duì)壓力區(qū)域沒有表現(xiàn)出任何吸附限制。?2003,QuantachromeInstruments遲滯回線類型

按照IUPAC

13.2節(jié)中的約定，劃分出了4種特征類型H4型遲滯回線出現(xiàn)在含有狹窄的裂隙孔的固體中，如活性炭中見到，在較高相對(duì)壓力區(qū)域也沒有表現(xiàn)出吸附限制。?2003,QuantachromeInstruments遲滯環(huán)與孔形的關(guān)系?2003,QuantachromeInstruments氣體吸附

可見,氣體吸附量隨著壓力的升高而增加，但不是線性的。如何測(cè)量? 如果氣體充分的覆蓋在固體表面(單層)的體積是已知的，就能夠精確地計(jì)算出比表面積。?CopyrightQuantachromeCorporation2000.Allrightsreserved.氣體吸附分析儀分析方法:在等溫條件下，通過測(cè)定不同壓力下材料對(duì)氣體的吸附量,獲得等溫吸附線，應(yīng)用適當(dāng)?shù)臄?shù)學(xué)模型推算材料的比表面積,多孔材料的孔容積及孔徑分布，多組分或載體催化劑的活性組分分散度表面積及孔徑分布測(cè)量可采用多種不同方法，氣體吸附法作為一種應(yīng)用性最廣、測(cè)量精度最高的方法被普遍接受?2003,QuantachromeInstruments測(cè)量方法流動(dòng)法把30%氮?dú)?被吸附物)和70%氦氣(載體)的混合氣體不斷在樣品上進(jìn)行流動(dòng)。當(dāng)樣品冷卻到液氮溫度時(shí)，氮?dú)獗晃剑獠槐晃?。吸附過程持續(xù)，直到氮?dú)馕搅窟_(dá)到30%濃度。這時(shí)，吸附量接近于單層表面覆蓋的體積。?CopyrightQuantachromeCorporation2000.Allrightsreserved.流動(dòng)法Flow通過用非吸附的氦氣稀釋氮?dú)?吸附質(zhì))獲得P/Po

.

RequiredP/Poisachievedbydilutingnitrogen(adsorbate)withhelium(non-adsorbing).

樣品被冷卻至液氮溫度而引起吸附.

Thesampleiscooledwithliquidnitrogen,tocauseadsorption.吸附(及隨后的脫附)過程是由熱導(dǎo)檢測(cè)器監(jiān)測(cè)的.Theadsorption(andsubsequentdesorption)processismonitoredusingathermalconductivitydetector.

?2003,QuantachromeInstruments動(dòng)態(tài)流動(dòng)法DynamicFlow 信號(hào)校正是通過將已知體積的純氮?dú)庾⑷氲綒饬髦羞M(jìn)行的.Thesignaliscalibratedagainstaknownvolumeofpurenitrogeninjectedintothegasstream.

該方法極其快速,特別適用于單點(diǎn)BET法對(duì)生產(chǎn)過程的監(jiān)控.Themethodisextremelyrapidandideallysuitedtomanufacturingprocessesusingthesinglepointmethod.

可用氪吸附作超低比表面.Verydiluteconcentrationofkryptonatliquidnitrogentemperatureisusedforextremelylowsurfaceareas.?2003,QuantachromeInstruments(經(jīng)典的)真空-體積測(cè)定法

(Classical)Vacuum-Volumetric需要在降低的溫度下,由樣品吸附吸附質(zhì)作為純吸附作用的函數(shù).

Requiresthatadsorbatebeadsorbedbythesample,atsomereducedtemperature,asafunctionofpressureofpureadsorptiveP/Po值(相對(duì)壓力)是通過制造局部真空做到的.P/Povaluesareachievedbycreatingconditionsofpartialvacuum.

在吸附過程中由高精度壓力傳感器監(jiān)測(cè)壓力的改變.

Highprecisionandaccuratepressuretransducersmonitorpressurechangesduetotheadsorptionprocess.?2003,QuantachromeInstruments測(cè)量方法真空法樣品池抽真空測(cè)量空體積(樣品池空間)A)用氦氣測(cè)量B) 存儲(chǔ)器里存有的校對(duì)值.樣品冷卻到液氮溫度，然后氮?dú)庾⑷氲揭阎獏⒖俭w積(歧管)的樣品池。由于氮?dú)庾⑷肟阵w積而膨脹，導(dǎo)致壓力下降，而氮?dú)獬錆M空體積時(shí)的壓力下降是能夠計(jì)算的。因此通過壓力的下降來計(jì)算氣體吸附量。?CopyrightQuantachromeCorporation2000.Allrightsreserved.真空法-氣體體積測(cè)量關(guān)鍵樣品的前處理(足夠的真空脫氣去除微孔中的雜質(zhì))通過制造局部真空條件測(cè)量P/Po值.通過高精準(zhǔn)度的壓力傳感器監(jiān)測(cè)氣體吸附過程中的壓力變化(微孔測(cè)量需多個(gè)壓力傳感器同時(shí)監(jiān)測(cè)Po,樣品管壓力和歧管壓力).微孔測(cè)量須盡量降低死體積(控制樣品管在液氮中的深度.?2003,QuantachromeInstruments樣品準(zhǔn)備----必須讓吸附質(zhì)”看到”表面

SamplepreparationTheadsorbatehasto“see”therealsurface.

隨時(shí)發(fā)生的微量潮氣吸附并不影響單分子層能力,但會(huì)影響吸附的強(qiáng)度,所以與在一個(gè)清潔表面上比較,單分子層的形成壓力會(huì)發(fā)生改變.

Whilstalittlepre-adsorbedmoisturewouldn'taffectthemonolayercapacity,itwouldaffectthestrengthwithwhichitisadsorbed,sothemonolayerwouldbeformedatadifferentpressurethanonacleansurface.孔道因毛細(xì)作用極易被潮氣阻塞.

Porescanbeeasilyblockedbymoisture.Waterundergoescapillarycondensationathumiditieswellbelowbulksaturationintheconfinesofthepore(justasnitrogendoesaswewillseelater).微孔能完全被填滿,不再是阻塞!

Microporescanbecompletelyfilled,notjustblocked!我們始終提供的是單位干重的表面積.

Wealwaysquotesurfaceareaperunitofdrymass.?2003,QuantachromeInstruments表面脫氣OutgassingofSurface在適宜的加熱溫度下,樣品通過真空的應(yīng)用或干燥惰性氣體的流動(dòng)除去吸附污染物的過程,主要是水汽.Sampleiscleanedofadsorbedcontaminants,mainlymoisture,bytheapplicationofvacuumorflowofdryinertgasandpreferablysomeheat.加熱到多高溫度?Howmuchheat??2003,QuantachromeInstruments表面脫氣OutgassingofSurface如何選擇樣品的脫氣溫度?

Whatisthepropertemperatureforsamplepreparation?在不改變樣品表面特性的前提下,應(yīng)選擇足夠高的溫度以快速除去表面吸附物質(zhì).Shouldbehighenoughtopromoterapidremovalofsurfaceadsorbedspecieswithoutchangingthesurfacetexture.不能高于固體的熔點(diǎn)或玻璃的相變點(diǎn),Tg

.Obviouslynothighenoughtomeltthesolid,norhotenoughtoexceedtheglasstransitionpoint,Tg.EstimateTgasmeltingpt0.7inkelvin(allowsafetymargin).建議不要超過熔點(diǎn)溫度的一半.Ornomorethanmeltingpoint0.5(kelvin)–Tammanntemperature.

舉例:硬脂酸鎂:40°C(for2hours)

Example:MagnesiumStearatemonograph:40°C(for2hours)?2003,QuantachromeInstruments真空脫氣還是流動(dòng)脫氣?

Vacuumorflow流動(dòng)脫氣對(duì)于除去表面大量弱結(jié)合的吸附水是非常好的,但對(duì)孔中吸附的水,只有經(jīng)長(zhǎng)時(shí)間吹掃使之?dāng)U散至表面,才能被帶出.

Aflowisgoodatremovinglargequantitiesofweaklybonded“wet”waterbydisplacementofthevaporfromexternalsurfaces.Howeverinthedepthsofapore,watermustdiffuseout…andindoingsomustbattlepastamuchhigherconcentrationofpurgegas.Onlywhenitisoutoftheporewillitbephysicallysweptaway.?2003,QuantachromeInstruments真空脫氣還是流動(dòng)脫氣?

Vacuumorflow真空脫氣對(duì)于除去表面大量弱結(jié)合的吸附水是不好的,因?yàn)樗畷?huì)在泵中擴(kuò)散.但對(duì)孔中吸附的水,不需要經(jīng)很長(zhǎng)時(shí)間就能擴(kuò)散至表面,繼而被帶出.

Vacuumisnotsogoodatremovinglargequantitiesofweaklybonded“wet”watersinceonceithasleftthesampleitmustdiffusetowardsthepump.(A“randomwalk”willmaketheactualdistanceneededtotravelMUCHfurtherthanitlookstous!Itwillspendmuchofitstimewanderingbacktowardsthesample!).Howeverinthedepthsofapore,watermustdiffuseout…andindoingsodoesnothavetobattlepastmuch-certainlynotanypurgegas.?2003,QuantachromeInstruments如何防止粉末樣品揚(yáng)析?PowderThimblesCellSealN/ECellkit?2003,QuantachromeInstruments吸附劑被吸附物吸附描述?CopyrightQuantachromeCorporation2000.Allrightsreserved.IrvingLangmuir(1881-1957)GraduatedasametallurgicalengineerfromtheSchoolofMinesatColumbiaUniversityin19031903-1906M.A.andPh.D.in1906fromG?ttingen.1906-1909InstructorinChemistryatStevensInstituteofTechnology,Hoboken,NewJersey.1909–1950GeneralElectricCompanyatSchenectadywhereheeventuallybecameAssociateDirector1913-Inventedthegasfilled,coiledtungstenfilamentincandescentlamp.1919to1921,hisinterestturnedtoanexaminationofatomictheory,andhepublishedhis"concentrictheoryofatomicstructure".Initheproposedthatallatomstrytocompleteanouterelectronshellofeightelectrons/alp/plasma/history.html1927Coinedtheuseoftheterm"plasma"foranionizedgas.1935-1937WithKatherineBlodgettstudiedthinfilms.1948-1953WithVincentSchaeferdiscoveredthattheintroductionofdryiceandiodideintoasufficientlymoistcloudoflowtemperaturecouldinduceprecipitation.1932TheNobelPrizeinChemistry"forhisdiscoveriesandinvestigationsinsurfacechemistry"?2003,QuantachromeInstrumentsConfiningadsorptiontoamonolayer,theLangmuirequationcanbewritten

whereVisthevolumeofgasadsorbedatpressureP,Vm

isthemonolayercapacity(i.e.θ=1)expressedasthevolumeofgasatSTPandKisaconstantforanygivengas-solidpair.Rearrangingintheformofastraightline(y=ab+x)gives

Langmuirianbehavior?2003,QuantachromeInstruments吸附劑被吸附物朗格繆爾理論?CopyrightQuantachromeCorporation2000.Allrightsreserved.吸附劑BET理論?CopyrightQuantachromeCorporation2000.Allrightsreserved.比表面積測(cè)定原理--BET法對(duì)于上述五種等溫線有許多種解釋，其中最成功的是BRUMAUER-EMMETT-TELLER三人在1938年提出的多分子層吸附理論由該理論得到的方程式稱為BET公式

P1C-1PV（P0-P）=VmC+VmC*P0在P/P0為0.05-0.35范圍內(nèi)可得一直線,通過斜率和截距可求得Vm(單層飽和吸附量)比表面積=VmN0/22400WN0為阿佛加得羅常數(shù),為一個(gè)吸附分子截面積?2003,QuantachromeInstruments比表面積計(jì)算B.E.T.方法1 = 1 C-1 P---------------- ---------------+--------------------V[(Po/P)–1] VmC VmCPowhere:V=吸附氣體體積Vm=單層吸附時(shí)需要的氣體體積C=B.E.T.常數(shù)P/Po=被吸附氣體的相對(duì)壓力方程式的等式為

Y=aX+b,plotYvX?CopyrightQuantachromeCorporation2000.Allrightsreserved.比表面積計(jì)算B.E.T.圖表斜率(s)=C-1VmC截距(i)=1 VmCVm=1 s+iStotal=VmN Axs

22,414P/Po1w[(Po/P)-1]0-10-20-3?CopyrightQuantachromeCorporation2000.Allrightsreserved.Where,N=Avogadro’snumber

Axs=cross-sectionalareaofadsorbatemoleculeBET公式:只能用于類型II,IV常數(shù)“C”與吸附能量有關(guān)C∝（E吸附-E蒸發(fā)）/RT必須為正值低值為弱吸附，低表面的固體“C”值范圍C=2-50,有機(jī)物,高分子與金屬C=50-200,氧化物,氧化硅C=>200活性碳,分子篩?2003,QuantachromeInstruments含有微孔樣品的BET計(jì)算活性炭樣品舉例:BET計(jì)算范圍為0.05-0.1(P/P0)多數(shù)符合Langmiur方程務(wù)必使C值大于0保持回歸系數(shù)優(yōu)于0.9999?2003,QuantachromeInstruments單點(diǎn)與多點(diǎn)的比較相對(duì)誤差?CopyrightQuantachromeCorporation2000.Allrightsreserved.?2003,QuantachromeInstruments在MONOSORB中對(duì)單點(diǎn)BET的校正?2003,QuantachromeInstruments不同孔徑的多孔材料吸附等溫線比較

NitrogenSorptionat77KintoMesoporousTiO26nm10nm30nm100nmH.Kueppers,B.Hirthe,M.Thommes,G.I.T,3(2001)110?2003,QuantachromeInstruments常用的比表面和孔徑分析吸附質(zhì)

CommonlyusedAdsorptivesforSurface-andPoresizeAnalysis氮?dú)猓篴t77.35K(liquidnitrogentemperature,T/Tc=0.61)比表面分析,微孔,介孔和大孔的孔徑分析最常用，易得高純度，價(jià)廉，液氮也易得氣固作用較強(qiáng)，公認(rèn)的分子截面積氬氣：at77.35K(T–Tr=-6.5K;Tr:

bulktriplepointtemperature;T/Tc=0.50)at87.27K(liquidargontemperature,T/Tc=0.57)比表面分析,微孔,介孔和大孔的孔徑分析最理想，無特別作用，可測(cè)微孔及中孔可在較高的相對(duì)壓力下（10-5-10-3)獲得微孔數(shù)據(jù)（0.3–1nm）擴(kuò)散快（液氬溫度高，87.3K)，平衡快，實(shí)驗(yàn)時(shí)間短也可用液氮，但不能用于大于12nm的孔，因?yàn)?7.3K比氬的三相點(diǎn)還低6.5K，所以在較大孔內(nèi)不能凝聚氪氣：at77.35K(T–Tr=-38.5K)

測(cè)量超低比表面at87.27K(T–Tr=-28.5K)poresizeanalysisofthinmicro/mesoporousfilms(M.Thommesetal,2004)用于非孔或大孔材料，因?yàn)殡礆獾腜o(=2.6t)很小在P/Po=0.05與0.25之間（NOVA不能用）CO2

:

at195K(T/Tc=0.63)at273K(T/Tc=0.89)poresizeanalysisofmicroporesofwidths<1.5nm(particularlyformicroporouscarbons)?2003,QuantachromeInstruments氮?dú)庠?7.4K的吸附：40小時(shí)?2003,QuantachromeInstrumentsCO2在273K的吸附：2.75小時(shí)?2003,QuantachromeInstruments孔分布分析?2003,QuantachromeInstruments孔結(jié)構(gòu)的測(cè)定氣體吸附法測(cè)定孔徑的經(jīng)典方法是以毛細(xì)管凝聚理論為基礎(chǔ)的KELVIN公式(最簡(jiǎn)化的孔模型):P平面P孔液體在細(xì)管中形成彎月面,在細(xì)管中凝聚時(shí)所需壓力較小,P孔<P平面,因此增壓時(shí)氣體先在小孔中凝結(jié),然后才是大孔.?2003,QuantachromeInstrumentsKelvin方程式Pore孔分布-根據(jù)樣品選擇不同的模型理論?CopyrightQuantachromeCorporation2000.Allrightsreserved.孔分布計(jì)算方法?2003,QuantachromeInstrumentsBJH(Barrett-Joyner-Halenda)法

只能用于中孔(>5nm),柱狀模型在壁上有多重吸附,類似液體,須假定液體密度用吸附與脫附等溫線,層層計(jì)算法當(dāng)<10nm時(shí)低估孔徑,<5nm20%誤差MesoporesPn-1rn-1Pnrn?2003,QuantachromeInstrumentsNitrogenadsorption/desorptionat77.35Konadisorderedaluminacatalyst

andporesizedistributioncurves

(TSE現(xiàn)象-張力強(qiáng)度效應(yīng))BJH-PSD無序介孔脫附的”突躍”與吸附劑無關(guān),而與吸附質(zhì)有關(guān)?2003,QuantachromeInstrumentsBJH孔徑分布:在脫附曲線上的假峰40PoreDiameter(angstrom)dV/dlogDArtifact?2003,QuantachromeInstruments最完全的數(shù)據(jù)處理方法與模型

比表面：BET,Langmuir(微孔),DR,BJH,DH

中孔分布：BJH,DH

微孔分布：DA(DR理論的擴(kuò)展),HK,SF

微孔/中孔分布：MP,DFT

微孔體積：t-方法，DR(含平均孔寬,分子篩和活性碳等微孔表征）分形維數(shù)：FHH,NK

總孔體積，平均孔徑?2003,QuantachromeInstrumentsComparisonsGasSorptionCalculationMethods

P/Porange Mechanism Calculationmodel1x10-7to0.02 microporefilling DFT,GCMC,HK,SF,DA,DR0.01to0.1 sub-monolayerformation DR0.05to0.3 monolayercomplete BET,Langmuir>0.1 multilayerformation t-plot(de-Boer,FHH),>0.35 capillarycondensation BJH,DH 0.1

to0.5capillaryfilling DFT,BJH inM41S-typematerials?2003,QuantachromeInstruments孔徑數(shù)據(jù)孔徑與孔體積可從吸附或脫附數(shù)據(jù)求得孔的總體積(V)從吸附總的氣體體積轉(zhuǎn)化成液體體積而得平均孔徑從簡(jiǎn)單的柱狀求得A

是BET表面積?2003,QuantachromeInstruments用t-圖法估算微孔對(duì)每一類材料,用標(biāo)準(zhǔn)的非孔樣品得到參考的t-曲線t-曲線由P/Po對(duì)t(=Vliq/S)作圖得到從等溫線與t-曲線中取同P/Po的點(diǎn)作圖可得到微孔體積,外表面積(非BET法)如不用參考t-曲線,而用總表面積未知的等溫線,則有a-圖法?2003,QuantachromeInstruments只有中孔的t-圖Slope=V/t=AZerointercept?2003,QuantachromeInstruments有微孔的t-圖Intercept=microporevolume?2003,QuantachromeInstruments有”膝”的t-圖SlopeA-slopeB=areacontributionbymicroporessizeCACB?2003,QuantachromeInstrumentsAspectsofRecentAdvancesintheCharacterizationofPowdersandPorousSolidsbyGasAdsorption

氣體吸附法表征粉末及多孔物質(zhì)的最新進(jìn)展QuantachromeINSTRUMENTS

JeffreyYang(楊正紅,康塔儀器公司首席代表)andMatthiasThommes(QuantachromeInstruments)?2003,QuantachromeInstruments氣體吸附法進(jìn)行孔徑分析

PoreSizeAnalysisbyGasAdsorption宏觀的熱力學(xué)方法(Macroscopic,thermodynamicmethods)Micropores(<2mn):e.g.,Dubinin-RadushkevitchormoreadvancedmethodssuchasHorvath-Kawazoe (HK)andSaito-Foley(SF),t-method,alpha-smethodMeso/Macropores(2-100nm):e.g.,KelvinequationbasedmethodssuchasBJH(Barrett,Joyner,Halenda)現(xiàn)代微觀方法-基于在分子水平上描述被吸附分子狀態(tài)的統(tǒng)計(jì)力學(xué):

(Modern,microscopicmethods,basedonstatisticalmechanics家describeconfigurationofadsorbedmoleculesonamolecularlevel)e.g.,DensityFunctionalTheory(DFT),MolecularSimulation

thesemethodsareapplicableforporesizeanalysisofboththemicro-andmesoporesizerange

用統(tǒng)一方法在整個(gè)孔分布范圍內(nèi)準(zhǔn)確地進(jìn)行孔徑分析Anaccurateporesizeanalysisoverthecompleteporesizerangecanbeperformedbyasinglemethod.?2003,QuantachromeInstruments在87K的氬吸附

ArgonAdsorptionat87.27K由于氬與孔壁的吸引作用較弱(缺少四極矩),它可以比氮在相對(duì)高得多的壓力下填充0.4-0.8nm的微孔(至少高1.5個(gè)數(shù)量級(jí)).

Due