超临界流体CO

1、超临界流体CO2 SupercriticalCO2fractionationofbio-oilproducedfromwheathemlockbiomassSatyanarayanNaik,VaibhavV.Goud,PrasantK.Rout,AjayK.Dalai*CatalysisandChemicalEngineeringLaboratories,DepartmentofChemicalEngineering,UniversityofSaskatchewan,Saskatoon,SK,CanadaS7N5A9articleinfoabstractThebiomassi.e.wheath

2、emlockusedinthisstudywasrstcharacterizedforitscomposition.Thephys-icalandchemicalcharacterizationofbiomasswasestimatedusingproximateanalysis,caloricvalue,crystallinity,devolatilizationbehaviour,ultimateanalysis,ICP-MSofash,FT-IR,XRD,CHNS,andHPLCanalysis.Forcommercialpurposethesamebiomasswasusedforco

3、nversiontobio-oilbyfastpyrolysisprocess.Therefore,inordertoinvestigateitscomposition,thebio-oilwasalsocharacterizedusingprox-imateanalysis,caloricvalue,whereasthechemicalcompositionofthebio-oilwasestimatedusingCHNS,1HNMR,GC-FIDandGC/MS.Thebio-oilobtainedfromwheathemlockbiomasswassuppliedbyAdvancedBi

4、oreneryCo.andaftertheanalysis,itscompositionhasbeendetermined.Itcontainsamixtureofhydrocarbons,pyranoids,furanoids,benzenoidsandfattyacids/alcoholswith45%ofwater,whichformsazeotropewithorganicpolarcompounds.ThesupercriticalCO2(SC-CO2)isanadvancedmethodforselectiveextractionofvaluablechemicalsfrombio

5、-oilwithoutsolventresidue.Theorganicfractionofthebio-oilwasisolatedbySC-CO2.ItwasobservedthatSC-CO2fractionscollectedat10and25MPapressurewereenrichedwithfuranoids,pyranoidsandbezenoids.Similarlythebio-oilwasalsofractionatedbyconventionalcolumnchromatographicmethodandtheyieldsandchemicalcompo-sitions

6、werecomparedwithfractionatedbio-oilobtainedusingSC-CO2.2010PublishedbyElsevierLtd.Articlehistory:Received9May2009Receivedinrevisedform8April2010Accepted8April2010Availableonline20May2010Keywords:WheathemlockbiomassBio-oilSupercriticalCO2ColumnchromatographyAnalysis1.IntroductionAlternativeandrenewab

7、leenergyresourceshaverecentlybe-comeahighpriorityformanycountriesandwillplayalargeroleinthechemicalindustryinthenearfuture.Theserenewableen-ergyresourceshavebecomepopularizedduetotheirlowenviron-mentalrisksandpollutionandarefavorablealternativestofossilfuelsandtheirderivatives.Biomasscanbeconsidered

8、asapromis-ingrenewableenergysourceandisnearlycarbonneutralandcon-sideredforvariousliquidfuelsandchemicals(Kumar,2009).Inadditiontotheirsustainability,theyare,ingeneral,moreevenlydistributedoverearthssurfacethanfossilfuelsoruraniumandmaybeexploitedusinglesscapital-intensivetechnologies.Henceitincreas

9、esthescopefordiversicationanddecentralizationofen-ergysuppliesandtheachievementofenergyself-sufciencyatalocal,regional,andnationallevel(Jones,1989).Cellulosicbiomassrepresentsarenewableandlargelyuntappedsourceofrawfeed-stockforconversionintoliquidfuels,thermochemicalproductsandotherenergy-relatedend

10、products(Sandersonetal.,1996).Theworldwideavailabilityofbiomassisestimatedtobe220billionoven-dryton(odt)peryearor4500EJ(1018J)(Anon,2004).Itisworldslargestandmostsustainableenergyresource.Onecanreducethefossilfuelconsumptionbyincreasingthe*Correspondingauthor.Tel.:fax:E-mai

11、laddress:ajay.dalaimail.usask.ca(A.K.Dalai).0960-8524/$-seefrontmatter2010PublishedbyElsevierLtd.doi:10.1016/j.biortech.2010.04.024capacityofenergyproducedfrombiomass.Theadvantagesofthisprocessaretoreducethegreenhousegasescomparedtofossilfuelsandalsosolvethedifcultiesofthedependenceofimportedfossilf

12、uelsformanycountries(Anon,2004).Biomassreferstoplantderivedorganicmatterthatisavailableonarenewablebasis.Itconsistsofcellulose,hemicelluloseandlig-nin.Lignocellulosicbiomassareoneofthepromisingrenewablefeedstocksforproductionofbio-fuelsandchemicalsduetopetro-leumoilshortage,uctuatingpriceofthecrudeo

13、ilandenviron-mentalproblems.Theuseofrenewableresourcesforfuel,suchasbio-oilderivedfromlignocellulosicbiomasshasgreatpotentialtoreplacepetroleumfuel.TheselectedbiomassessuchaswheatstrawandhemlockwoodareabundantinCanadaandmaybeusedasfeedstockforproduc-tionofbio-oil.IntheprairieprovincesofCanada,Saskat

14、chewanproduces7.6millionstonofwheatannuallybasedontheaveragetakenovertheproductionofthepast10years(InformationofSas-katchewan,2008).InCanadaaverageannualwoodcuthasbeenestimatedat167.5millionm3creatingover60milliontonnesofresidues(Anon,2004;Mohanetal.,2006).Hemlock(Tsugacanad-ensis)isoneofthewoodbiom

15、assinCanada.ItisalsocommonlycalledCanadaHemlockandHemlockSpruceisnativetoAsiaandWesternAmerica(Cowles,2009).ItmostlyoccursinUSAandsouthernborderofCanadafromsouthernOntariotoCapeBretonIsland,NovaScotia.Hemlockoccursasadominantorcodominantinconiferousandmixed-hardwoodforests.Hemlockwoodisof7606S.Naike

16、tal./BioresourceTechnology101(2010)76057613lowvaluebecauseofbrittlenessandabundantknots.Itisgenerallyusedforpulp,lightframing,sheathing,roong,subooringandboxes.Afundamentalcharacterizationofbiomassasafeedstockisre-quiredforbio-fuelandchemicalproduction,whichexhibitverydifferentpropertieswithrespectt

17、otraditionalfossilfuelsandtheirderivatives(Biaginietal.,2006).Inparticular,lingo-cellulosicmaterialsaremorereactiveandhaveahighervolatilitythancoals.However,allbiomassdiffersgreatlyinvolatilematterconcentra-tion,whereeventhesametypeofbiomasscanshowchangeincompositionbasedontheclimaticconditionsandse

18、asonalvaria-tion.Furthermore,characterizationofbiomassisimperativeasthechemicalcompositionofbiomassaffectstheconversionprocessesdifferently.Forexample,highnitrogenandashconcentrationreduceshydrocarbonyieldduringthermochemicalconversion(Sandersonetal.,1996),whereasligninconcentration,oneofthethreebas

19、iccomponentsoflingo-cellulosicmaterial(cellulose,hemicelluloseandlignin)doesnothavedetrimentaleffectonthermochemicalproductyield.Biomassfeedstockcompositiondeterminesthetheoreticalyieldfromabiochemicalconversion,andcantherebyhaveasignicantimpactonconver-sionprocesseconomics.Asapartofourongoingprojec

20、twehavestudiedthecharacterizationofsomeCanadianbiomasssampleswhichareabundantlyavailable(Naiketal.,2010).Pyrolysisisathermochemicalprocessapplyinghighheattolignocellulosicmaterialsintheabsenceofairorinreducedairthatconvertsorganicmaterialsintousablefuels(Demirbas,2007).Thebio-oilwhichisadarkaqueousp

21、olarliquid,isproducedusingashpyrolysis(Mohanetal.,2006).Itisusedasasubstituteforfueloilinboilerandengineapplicationsandalsohasthepoten-tialforblendingwithpetroleum.Bio-oilwhichiscomposedofal-most300chemicalssuchaspyranoids,furanoids,benzenoidsandfattyacids/alcoholscanbedirectlyusedasfuelorpyrolysedt

22、opro-ducehydrogen/syngas.However,inordertomakethewholepro-cessofproducingandusingbio-oilmoreefcientandeconomical,someofthevaluablechemicalscanbeextractedfrombio-oilandtherestofthebio-oilcanbeusedasbio-fuel.Thusafterremovalofpyranoids,furanoidsandbenzenoids,thequalityofthebio-oilisimprovedwithhigherp

23、ercentageoffattyacids/alcohols,whichissuitableforfuelapplication.Thesechemicalscanbeextractedusingafractionationorsolventextractionprocess.However,re-portsonuseofsupercriticaluids(SCF)suchassupercriticalcar-bondioxide(SC-CO2)fortheextractionofchemicalsfrombio-oilarescarce.Thistechnologyhasadvantageo

24、vertraditionaltechnol-ogybyeliminatingtheuseofpollutingorganicsolvents.TheSC-CO2extractioniscommonlyusedforextractionofnaturalmateri-alsbecauseofthenon-toxic,non-ammablecharacteristicsofCO2anditsavailabilityinhighpuritywithlowcost.Since,CO2haslowcriticaltemperature(31.1C)andlowcriticalpressure(73.8b

25、ar),itcanbetreatedasanidealsolventforextractionofnaturalprod-ucts.Itoffersattractiveextractioncharacteristics,owingtoitsfavorablediffusivity,viscosity,surfacetensionandotherphysicalproperties.Itsdiffusivityisoneortwoordersofmagnitudehigherthanthoseofotherliquids,whichfacilitatesrapidmasstransferandf

26、astercompletionofextractionincomparedtoliquidsolvents(Mukhopadhyay,2000).ReverchonandDeMarco(2006)havere-viewedthenumerousworkcarriedoutontheapplicationofSC-CO2infoodprocessing,pharmaceuticalsandneutraceuticals.Re-centlyourworkonextractionofaxseedwithSC-CO2hasshownimprovementinyieldalongwithsuperior

27、qualityincomparedtotheconventionalsolventextractionprocess(Pradhanetal.,2010).EsquivelandBernardo-Gil(1993)concludedthatSCFextractionexploresthesolventpowerofuidsattemperaturesandpressureshigherthanitscriticalvalue.Guo(1995)studiedtheseparationofethanolfromaqueoussolutionbyusingliquidCO2.Duetoitslow

28、latentheatofvaporisation,lowenergyinputisrequiredfortheextractionsystem.Further,theenergyrequiredforSC-CO2treatmentisoftenlessthantheenergyassociatedwithdistillationofconventionalorganicsolvents.However,thecapitalcostsarehigherandtotalenergyconsumptiondependsonthepressureusedandonthesolute-to-solven

29、tratios.ThesolventcapacityofSC-CO2isdensitydependentanditisthesharpvariabil-ityofdensitywithpressureandtemperature(Bijhmetal.,1989;Mukhopadhyay,2000).TheSC-CO2fractionationofbio-oilisanad-vancedprocesstoproducemoisturefreeextractandisanattrac-tivealternativetoextractthevaluablecompoundsfrombio-oil.S

30、C-CO2canbetreatedasanidealsolventforextractionofnaturalproducts.Itoffersattractiveextractioncharacteristicsduetoitsfavorablediffusivity,viscosity,surfacetensionandotherphysicalproperties.ItsdensityandsolventpropertiesincreasewithincreasingCO2pressure.Theadvantageofthisprocessisthatdif-ferenttypesofc

31、ompoundscanbeselectivelyextracted/separatedatparticularCO2pressure.Forexample,atlowpressureeasilyextractablecompounds(lowmolecularweight)arerecoveredincomparedtohighmolecularweightcompounds.Anotheradvan-tageofSC-CO2,thewaterisverysoluble(2.5molfraction),there-foreitisanattractivealternativeforsepara

32、tionofwaterfrombio-oilbyusingthisadvancedprocess.Tothebestofourknowledge,thereisnoreportavailableintheliteratureonseparationoforgan-iccomponentsfrombio-oilusingSC-CO2.Therefore,inthisstudyattempthasbeenmadetocharacterizethewheathemlockbio-massanditsbio-oilandfurthermorefractionatethebio-oilusingSC-C

33、O2togetvalueaddedchemicals,whichwascomparedwiththatobtainedusingconventionalcolumnchromatographicprocess.2.Methods2.1.CharacterizationofbiomassWheathemlockbiomassanditsbio-oilweresuppliedbyAd-vancedBiorenery,Ottawa,Canada.Thesolventssuchaspentane,carbontetrachloride(CCl4),benzene,chloroform(CHCl3),d

34、iethylether(Et2O)usedintheexperimentswerereagentgrade(SigmaAldrich)anddistilledinlaboratorybeforeuse.Theanalysisofbio-mass,bio-oil,andsupercriticalcarbondioxidefractionedfractionwerecarriedoutbyfollowingstandardNRELandASTMmethods.Theexperimentalresultsobtainedaretheaverageofatleastthreesetsofdatapre

35、sented.2.1.1.ProximateanalysisofbiomassAlltheexperimentresultswereaverageofthreerunsanddataarepresentedwithrelativestandarddeviation.Themoisturecon-tentofthebiomasswasdeterminedusingtheproceduregiveninASTMD3173-87(2003).Pulverizedsample(1.0g)wasusedandovendriedfor1hat130C.Theashcontentwasdeterminedi

36、nlaboratorymufefurnace(Holpack,USA)asperASTM3174-04(2004).Thebiomasssample(1.0g)wastakenincrucibleandplacedinmufefurnacewhichwasmaintainedat57510Cfor4h.ThevolatilematterinthebiomasssamplewasdeterminedbytheproceduregiveninASTMD3175-07(2007).Inthatcase,1.0gbiomasssamplewastakeninacrucibleandplacedinmu

37、fefurnacewhichwasmaintainedat95010Cfor7min.Thenthecruciblewasremovedfromthefurnaceandplacedinthedesicca-tor.Theamountofvolatilematterofthebiomasswasdeterminedbytakingthedifferenceinweight.2.1.2.PhysicalpropertiesofthebiomassThecaloricvaluewasdeterminedinastaticbombcalorimeter,asealedParr1108,followi

38、ngtheproceduredescribedbyHubbardS.Naiketal./BioresourceTechnology101(2010)760576137607etal.(1956).Thedetailedexperimentalconditionsaregiveninourearlierpublication(Naiketal.,2010).TheXRDanalysisofthebiomasswasperformedusingRigakudiffractometer(Rigaku,Tokyo,Japan)usingCuKaradiationat40kVand130mAinthes

39、canningangleof045atascanningspeedof0.05min1.TheXRDanalysisofcelluloseandligninwascarriedoutforcomparativepurpose.Thepurelaboratorygradecottonwastakenforcelluloseanalysis.Ligninwasderivedfrompinewoodinourlaboratoryandwasusedforthermo-gravi-metricanalysis.Theprocedurewasgiveninanearlierpublication(Nai

40、ketal.,2010).Thermo-gravimetric(TG)analysesofthebiomass,celluloseandligninwereperformedbyusingPerkinElmer,PyrisDiamondTG/DTAinstrumentinordertodeterminethedevolatilizationcharac-teristicsofthebiomasssampleswithtemperature.Thesample(0.5mg)wassubjectedtoatemperatureprogram25835C(10C/min)withpurgegas(A

41、rgon)owof10mL/min.Thelossofweightandrateofweightlosswithtemperaturewererecorded.2.2.ChemicalanalysisofbiomassThechemicalanalysisofbiomasswasstudiedbyICP-MS,CHNS,FT-IRandHPLC.TheanalysisofsomecommonelementspresentintheashwasdeterminedbyICP-MSandcommonorganicelementsi.e.C,H,NandSwereanalysedinPerkinEl

42、merElementarCHNSanalyzer.TheFT-IRspectraofbiomasswereobtainedbyKBrpel-letingmethodusingPerkinElmer,FT-IRspectrumGXintheIRrangeof5004000cm.DeterminationofsugarsinbiomassThebiomasswasacidhydrolyzedforconversionofhemicellu-loseandcellulosetowatersolublesugarsusingthestandardNRELmethod(2005).Then

43、afterwatersolublesugarswereanalysedbyHewlettPackardHPLCequippedwithanRIdetector.TheanalysiswasperformedbyanAminexHPX87Pcolumn(BioRad,Hercules,CA)equippedwithade-ashingguardcartridge(BioRad).DegassedHPLCgradewaterwasusedasthemobilephaseat0.6mL/minatcolumntemperatureof80C.Theinjectionvolumeusedwas20lL

44、witharuntimeof20min.Mixedsugarstandardsviz.cello-biose,glucose,xylose,galactose,mannoseandarabinosewereusedforqualitativeanalysis.Theweightpercentagesofthesesugarsinthesamplesweredeterminedbycomparingwithrespectivestan-dards.Theacidinsolublepartofthebiomasswastreatedaslignin.2.3.SupercriticalCO2(SC-

45、CO2)fractionsofbio-oilThebio-oilusedinthisstudywasproducedfromwheathem-lockbiomassbyfastpyrolysisprocessforcommercialpurposebyAdvancedBiorenery,Ottawa.Thebio-oilwasfractionatedusingSC-CO2unitsuppliedbyTharTechnologies.Thebio-oil(50g)wasmixedwithclean2mmglassbeadsandthenafterplacedintheextractortohal

46、fofitsvolume.TheSC-CO2extractionwascar-riedoutat40CwithCO2owrateof40g/min.Threefractionswerecollectedatthreedifferentpressuresi.e.10,25and30MPa,respectively,withtheextractiontimeof2hineachexperimentkeepingalltheotherconditionsidentical.Initially,extractionpro-cesswasstartedat10MPapressureandwasconti

47、nuedfor2h.Therstfractionwascollectedat10MPapressure,thenafterthepres-surewasraisedto25MPaandextractionwascontinuedforan-other2hkeepingallotherconditionsidentical.Aftercollectingthesecondfraction,theremainingmaterialwithglassbeadswasagaintreatedinthesamewayat30MPatocollectthethirdbio-oilfraction.Itwa

48、sobservedthatthebio-oilusedforthestudywasblackishincolour,whereasSC-CO2fractionsderivedfromthebio-oilwerereddishincolour.2.3.1.PhysicalpropertiesThemoisturecontentofbio-oilandSC-CO2fractionsderivedfrombio-oilwasdeterminedbyKarlFischertitrator,whereasashcontentandcaloricvaluesweredeterminedbymethodsd

49、e-scribedabove.TheKarlFischertitrationwascarriedoutbyMettlerToledoTitratorDL32,ProvidedbyMettlerToledo,USA.Sample(0.1g)wasinjectedintothetitrationcell(Anolyte)connectedtoabalancetomeasuretheamountofsampleinjected.AnolytewasprovidedbyMerck.Sampleswithwatercontentmorethan5wt%weredi-lutedwithmethanolbe

50、foretheinjection.Iodineproducedbyio-dideavailableintheAnolytereactswithwater.Assoonasallthewaterreacted,thefreeiodinewasdetectedintheAnolyteandtheKarlFischertitrationwasterminatedbytheequipment(Scholz,1984).2.3.2.ChemicalpropertiesThechemicalpropertiesofthebio-oilandSC-CO2fractionsweredeterminedbyCH

51、NS,FT-IR,1HNMR,GC-FIDandGC/MS.1HNMRwasrecordedonDPX-500Brukermachineat500MHzat25C.Forthestudy,0.2gofbio-oilwasdissolvedinCD3ODand0.2gofSC-CO2fractionsweredissolvedinCDCl3forspectralanalysis.GCanalysiswascarriedoutonaVarianCP-3800GasChromatographequippedwithaameionizationdetector(FID)anda30m0.25mmWCO

52、Tcolumncoatedwith0.25lmlmthickness(DB-5).Heliumwasusedasthecarriergasataowrateof1.2mL/minatacolumnpressureof22kPa.Eachsample(0.2lL)wasinjectedintotheinjectionportoftheGCusingasplitratioof50:1.Compoundseparationwasachievedfollowingalineartem-peratureprogramof50250C(5C/min),250C(20min).Per-centagecomp

53、ositionwascalculatedusingpeaknormalizationmethod.EachsamplewasanalysedtwiceinGC;thusatotalfourGCanalysiswereperformedforextractsfromeachoftheprocess.TheGC/MSanalysiswascarriedoutonaVarianSaturn2200GC/MSttedwiththesamecolumnandtemperatureprogrammedasabove.Peakidenticationwascarriedoutbycomparisonofth

54、emassspectrawithmassspectraavailableonNIST-1andNIST-IIlibraries.Thecompoundidenticationwasnallycon-rmedbycomparisonoftheirrelativeretentionindices(RRI)withliteraturevalues(Yupingetal.,2008;Vichietal.,2007).TheRRIofthepeakswascalculatedbystandardsamplemixtureofnormalsaturatedhydrocarbonsC-7toC-22andw

55、asinjectedintotheGCcolumnunderthesameconditionsofsampleanalysis(Routetal.,2007).2.4.Bio-oilfractionationusingcolumnchromatographyDuringthisstudycrudebio-oil(30g)wasextractedwith50%CHCl3inEt2O.Fortheextractionpurpose50mLmixtureofsolvent(i.e.CHCl3andEt2O)wastakeneachtimeandtheprocesswasre-peatedthreet

56、imestoensurethatmaximumextractshavebeenrecovered.Thereafterthesolventsolublematerialwasconcen-tratedinrotaryevaporatorundervacuoandCHCl3Et2Oextractedbio-oilwasusedforcolumnchromatography.TheCHCl3Et2Oextractedbio-oilwasfractionatedinaglasscol-umn(80cm2cm)using60gof100200meshcolumnchro-matographicsili

57、cagel.Firstthecolumnwaseluatedwith500mLpentanetoobtainthepentanesolublefraction.Afterthepentanefractionationthesamecolumnwaseluatedwith500mLofCCl4,benzene,Et2OandCHCl3followedbyoneafteranotherandattheendthecolumnwaswashedwithmethanol.Allthecollectedfractionswereconcentratedinrotaryevaporatorundervac

58、uoandstoredatrefrigeratedconditionpriortotheanalysis.Thefrac-tionswereanalysedbyGC-FIDandGC/MS.7608S.Naiketal./BioresourceTechnology101(2010)76057613.tnetnocrettamelitalovdnahsa,eru.tSsidomnafoN,eHcn,Cerfeof.fiendcnoimetraoerrfeffididdsenteahocltuoctlmaonicrfndnoeebtk.aadrlteacuttcocdleantecSex1dOde

59、tffnoooalbn%N:adabcTn3.Resultsanddiscussion3.1.BiomassTheproximateanalysis,ultimateanalysis,caloricvalueandpHofthebiomassarepresentedinTable1.ItcanbeobservedthatlowamountsofN(0.05%)andS(0.01%)arepresentinthebiomass.Theelementalanalysisoftheashshowsthatfollowingelementsarepresentintheashsample(inppm)i.e.Mg(16,465),Al(2707),Ca(57,059),P(7374),Cr(73),Mn(2651),Fe(9123),Co(63),C