地化论文.docx

地化论文.docx

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地化论文

CHINAUNIVERSITYOFPETROLEUM

Futureresearchonkerogen

Subject：

Geochemistry

Name：

ZhaoLong

NO：

2011211120

Outline

Futureresearchonkerogen2

1.Kerogenisolationandanalyticaltools3

2.Frombiomoleculestokerogen6

2.1.Biologicalstudies6

2.2.Diageneticstabilityofbiomolecules7

2.3.StudyofOMinsoilandrecentsediments8

3.Physicalprotection10

Futureresearchonkerogen

Awealthofinformationhasbeenaccumulatedsincethe1980sonkerogen.However,anumberofimportantpointsstillhavetobeelucidatedandsignificantadvancescanbeexpectedinthenearfuture,especiallyinrelationtoprogressinusingspecificanalyticaltools.Indeed,increasingpossibilitiesinmolecularanalysisandmicroscopyhavebeenresponsibleformostoftheadvancesinthepast.Degradativechemicaltechniquesandpyrolysiswerealsoofprimeinterestforthestudyofcomplexmacromolecularsystemssuchaskerogen.Theseadvancestookadvantagenotonlyofimprovementsinanalyticaltechniques,butalsooftheircoupling,allowingseparateanalysisofselectedindividualcompoundsincomplexmixtures.Besidestheforeseendevelopmentofnew,oftencoupled,analyticalmethods,discussedbelow,ageneraltrendcanbeobservedtowardsabsolutequantificationofgivenmolecularspecies,formerlystudiedusingqualitativetechniques.Quantificationenablesnotonlyuniversally-scaledparameterstobeobtained,butalsodeterminationoftherepresentativityofmolecularspeciesarisingfromthermalorchemicaldegradationofkerogen.

Kerogenstudywillremainanactiveandprolificfieldinthecomingyears.Itshouldbelargelypromotedusingmultidisciplinaryapproaches,includingbiologicalstudiesandOMstudiesofmodernenvironments,alongwiththedevelopmentofnewanalyticaltools,includingpin-pointanalysis.Inturn,theinformationobtainedonkerogencouldgivenewinsightsintothetraditionalgeochemicalapplications,butalsointootherfieldslikepalaeoenvironmentandpalaeoclimatereconstructionandtheglobalcarboncycle.

Thefollowingdiscussionisfocussedontopicscurrentlyinprogress.Ineachcase,startingfromthelatestavailablestudies,wetrytobringoutsometrendsforfutureresearch,intheshorttomediumterm.Afterabriefdiscussiononpossibleimprovementsinkerogenisolationmethodssuitableforverylowmaturitysamples,thefirstpartisdevotedtothepotentialofrecentdevelopmentsinanalyticaltechniquesforobtainingbetterknowledgeofthechemicalstructureofkerogenandofitsinteractionswithmineralsinsediments.Then,thepathwaysleadingfrombiomoleculestokerogenandrelatedchemicaltransformationsareconsideredasanotherpossibleareaforimportantdevelopments.

1.Kerogenisolationandanalyticaltools

Suitableconditionsforkerogenisolationfromancientsamplesarenowwellestablished.Moreover,maceralseparationfromisolatedkerogenshasbeenaccomplishedthroughthetechniqueofdensitygradientcentrifugation,therebyallowingbettercharacterizationofkerogencomponents.Incontrast,problemsarestillencounteredfor“protokerogen”isolationfromrecentsediments.ThisisduetothelabilityofalargepartoftheinsolubleOMinsuchsampleswhensubmittedtotheclassicalHF/HCltreatment.SimilarproblemsareencounteredforsoilOMbut,inthatcase,theycanbelargelyovercomebyusingdilutedHF.Anefficientmethodhasbeendevelopedforthedemineralizationofrecentsedimentsasdescribedinthekerogenisolationsection.Thismethodresultsinextensiveeliminationofminerals,whileOMlossesandalterationarelimited.Moreover,efficientremovalofparamagneticmetalsisachievedsothatthequalityofthesolidstateCP/MAS13CNMRspectraoftheisolatedmaterialsishighlyimproved.Furthergainsintheorganicenrichmentfactorobtainedwiththismethodcouldprobablyresultfromimprovementsinthesequenceofacidtreatmentsforreducingashcontent,andinusingdesaltingbyresinsforincreasingdissolvedOMrecovery.

Kerogenstudiesshouldrapidlybenefitnotonlyfromthedevelopmentofnewanalyticalmethods,butalsofromgreateruseofsomeoftheexistingtoolswhichhavesofarbeenrarelyemployedfortheanalysisoffossilmacromolecularOM.Thus,examinationofkerogenultrastructureusingSEMandTEMshouldbecomemoregeneral,incombinationwithgeochemicalanalyses,alongwithmicroscopicobservationscoupledtospectroscopicanalysiswithmicro-FTIRandelementalmapping.Otherpin–pointmethodsshouldalsobeuseful,suchasenergyfilteringTEMandelectronenergylossspectroscopy,asappliedbyFurukawa,2000toastudyofOM/claymineralinteractions.Furthermore,asshownby[Greenwoodetal.,1998],[Greenwoodetal.,2000] and [Arourietal.,1999],importantinformationonthecompositionofindividualorganicparticlescouldbeobtainedthroughkerogenexaminationwithlightmicroscopycoupledtolasermicropyrolysisGC–MS.TheuseofhighresolutionTEMshouldalsobedeveloped,especiallyforstudiesconcernedwiththeidentificationandcharacterizationofhighlyaromaticparticles,suchasblackcarbon（BC）particles,aswellaswithOM/mineralinteractions.

Pyrolyticmethodshavebeenusedextensivelyforkerogenstudies.However,relativelylowyieldsofliquideffluentsandrelativelylowweightlossesareobtained（exceptforlowmaturityTypeIkerogen）whenusingconventionalpyrolysis.Improvementandadditionalinformationoncomplexnaturalmacromolecularmaterialscanbeobtainedwithdoubleshotpyrolysis（Quénéaetal.,2006a）.Yieldimprovementcanalsobeachievedusingcatalytichydropyrolysisand,asmentionedabove,TMAHthermochemolysis.Importantadditionalinformationcanbeobtainedwiththelatterapproachusingothertetramethylammoniumsalts,withdifferentbasestrengths,likeacetate（TMAAc）orcarbonate（TMACO3;e.g.[Jolletal.,2004] and [Deportetal.,2006]）orbyusing13Clabelledreagentssuchas13CTMAH（Filleyetal.,2002b）.Catalytichydropyrolysis,i.e.pyrolysisunderhighH2pressurewithaMocatalyst,wasfirstdevelopedforcoalliquefactionandtoincreaseshaleoilproductionuponretorting（Snapeetal.,1994）.Thismethodhasbeenappliedsuccessfully,interalia,tothestudyofkerogencompositionandhasaffordedusefulinformationonaliphaticmoieties（[Loveetal.,1995] and [Loveetal.,1998]）andorganicsulfurspeciation（[Mitchelletal.,1994] and [Brownetal.,1997]）.However,alltheaboveimprovementshavebeenappliedsofaronlyinalimitednumberofcasesandfuturepyrolyticstudiesshouldlargelybenefitfromtheirmoregeneraluse.

Selectivechemicaldegradationhasalsobeenappliedextensivelytoderiveinformationonthechemicalstructureofkerogen（e.g.[Forsman,1963],[Vitorovićetal.,1984],[Michaelisetal.,1989],[RullkötterandMichaelis,1990],[Adametal.,1991],[Amblèsetal.,1996],[Blokkeretal.,2000] and [YoshiokaandIshiwatari,2005]）.Suchexperimentsusuallysufferfromlowyieldsofreleasedproductsbeingobtained.Kerogenconversiontoupto80 wt%ofsolublematerialhasbeenachievedthroughstepwisechemicaldegradationofsomeTypeII-Skerogenexamples（[Schaeffer-Reissetal.,1998] and [Höldetal.,1998]）,althoughsuchhighyieldsareonlyobtainedfromS-richsamplesowingtotherelativelyeasycleavageofsulfurlinkagesusingchemicaltreatment.Greatadvancesinthedevelopmentofnewreagentsand/ormoresuitableexperimentalconditionsarestillneededtoobtainsatisfactoryyieldsfromotherkerogentypesviachemicaldegradation.Inthisrespect,highdegradationyieldanddifferentiationbetweenesterandethermoietieshavebeenobtained,forexample,fortheMesseloilshalebyusinganalkalinehydrolysis/RuO4oxidation/alkalinehydrolysissequence（Dragojlovićetal.,2005）.

Developmentsinmassspectrometryshouldpromotedirectstructuralstudiesofkerogen.Temperature-resolved,in-sourcepyrolysismassspectrometrywasshowntobeapowerfultoolfortheexaminationofvarioustypesofmacromoleculesandformarinehighmolecularweight（HMW）OM（e.g.[Boon,1992] and [Boonetal.,1998]）.Ionizationmethodssuchasmatrix-assistedlaserdesorptionionization（MALDI）andelectrosprayionization（ESI）weredevelopedforstudiesonbiomacromoleculesandareefficientforproteinswithmolecularweight> 100,000 Da（McLaffertyetal.,1999）.SuchtechniquesarethereforehighlypromisingforthecharacterizationofkerogenandofHMWkerogenprecursorsanddegradationproducts.However,limitationininterpretationmayarisefromthegreatcomplexityofthesematerials.ESIcombinedwithquadrupoletime-of-flight（QqTOF）massspectrometryandwithFT（Fouriertransformedioncyclotronresonance（FT-ICR））massspectrometrywasusedforthecharacterizationofhumicsubstances（Kujawinskietal.,2002）andofpolarNSOcompoundsinvariousoils（[Hugheyetal.,2004] and [Kimetal.,2005]）.Highresolutionwasthusachieved,withresolvingpower> 80,000andmassaccuracy< 1 ppm,forcompoundswithm/zupto3000andexactmolecularformulaecouldbeobtained.

AdvancesinspectroscopicstudiescouldbeachievedthroughnewdevelopmentsinNMR.Asolidstate2Ddoublecrosspolarization,magicanglespinning,13C15NNMRstudyhasbeenreportedfor13C-and15N-enrichedhumicsubstancesandmicrobiallydegradedbiomass（[Zangetal.,2001] and [Knicker,2002]）.Highresolution,magicanglespinning13C1HNMRhasbeenusedforstructuralstudiesofcutan（Deshmukhetal.,2005）.XANESspectroscopyprovedtobeanefficienttoolforsulfurspeciationinkerogen（e.g.Riboulleauetal.,2000）.Studiesoncarbonaceousmaterialcharring（Turneretal.,1997）suggestthatoxygenK-edgeXANEScouldalsobeuse