Carbon dioxide capture using polyethylenimine-load

JOURNALOFENVIRONMENTALSCIENCESISSN1001-0742CN11-2629/X(1)124–132Carbondioxidecaptureusingpolyethylenimine-loadedmesoporouscarbonsJitongWang,HuichaoChen,HuanhuanZhou,XiaojunLiu,WenmingQiao,DonghuiLong∗,LichengLingStateKeyLaboratoryofChemicalEngineering,EastChinaUniversityofScienceandTechnology,Shanghai200237,China.E-mail:[e-mail]27March2012;revised28May2012;accepted31May2012AbstractAhighefficiencysorbentforCO2capturewasdevelopedbyloadingpolyethylenimine(PEI)onmesoporouscarbonswhichpossessedwell-developedmesoporousstructuresandlargeporevolume.ThephysicochemicalpropertiesofthesorbentwerecharacterizedbyN2adsorption/desorption,scanningelectronmicroscopy(SEM),thermalgravimetricanalysis(TG)andFouriertransforminfraredspectroscopy(FT-IR)techniquesfollowedbytestingforCO2capture.Factorsthataffectedthesorptioncapacityofthesorbentwerestudied.ThesorbentexhibitedextraordinarycapturecapacitywithCO2concentrationrangingfrom5%to80%.TheoptimalPEIloadingwasdeterminedtobe65wt.%withaCO2sorptioncapacityof4.82mmol-CO2/g-sorbentin15%CO2/N2at75°C,owingtolowmass-transferresistanceandahighutilizationratiooftheaminecompound(63%).MoisturehadapromotingeffectonthesorptionseparationofCO2.Inaddition,thedevelopedsorbentcouldberegeneratedeasilyat100°C,anditexhibitedexcellentregenerabilityandstability.TheseresultsindicatethatthisPEI-loadedmesoporouscarbonsorbentshouldhaveagoodpotentialforCO2captureinthefuture.Keywords:carbondioxidecapture;polyethylenimine;mesoporouscarbon;amineutilizationratioDOI:10.1016/S1001-0742(12)60011-4IntroductionTheincreaseofanthropogenicCO2emissions,mainlycausedbythecombustionoffossilfuels,hasraisedseriousconcernbecauseofitsgreenhouseeffect(Plazaetal.,2008),andagreatdealofefforthasbeendevotedinlimitingtheemissionsofCO2totheenvironment.Carbondioxidecaptureandstoragetechniqueshavebeenpro-posedbytheIntergovernmentalPanelonClimateChangeasasuitabletechnologyformitigatingclimatechangeinthemid-term(Metzetal.,2005).Todate,avarietyofseparationmethods,includingabsorption,adsorption,cryogenicdistillationandmembranetechnologyhavebeendevelopedforcapturingCO2fromfluegas(D’Alessandroetal.,2010;Inuietal.,1988;Piresetal.,2011).Thestate-of-the-artlarge-scalecaptureofCO2isbasedontheliquidamineabsorptiontechnique.However,thistechniquealsohasseveraldrawbackssuchashighenergyconsumption,solventevaporation,limitedcyclingcapacity,equipmentcorrosionorflowproblems(Knudsenetal.,2009).There-fore,solid-phasesorption,whichcanovercomethesedrawbacks,wouldbeagoodsubstitute.*Correspondingauthor.E-mail:[e-mail],mesoporousmaterialsfunctionalizedwithaminegroupshaveattractedconsiderableattentionduetotheirhighefficiencyandselectivityforCO2capturefromgasmixtures.Theuseofaminegroupsanchoredtoasolidsupportcanalsosignificantlyreducetheirtoxicandcorrosivepotential.Generally,amine-typeCO2capturingagentscanbeintroducedintoporoussupportsbytwomethods:graftingwithaminogroups(HarlickandSayari,2007;Hiyoshietal.,2005;Knowlesetal.,2005,2006;Sanzetal.,2009;Serna-Guerreroaetal.,2010)andimpregnationusingaliquidorganicpolymerlikepolyethyleneimine(PEI),tetraethylenepentamineordiethanolamineonmesoporousmaterials(Franchietal.,2005;Gargiuloetal.,2007;Lietal.,2008;Liuetal.,2010;Maetal.,2009;Satyapaletal.,2001;Sonetal.,2008;Wangetal.,2011;Yueetal.,2006).Inbothoftheseamine-supportedsystems,amine-functionalitiesaredis-persedinsidetheporesofamesoporoussupportmaterial,andtherebyproduceenhancedCO2captureperformancerelativetothatofthebulkamines.Polyethyleneimineisapolymerwithalargequantityofaminogroupsonmacromolecularchains,whichwasfirstusedinCO2capturebySatyapaletal.(2001)toNo.1Carbondioxidecaptureusingpolyethylenimine-loadedmesoporouscarbons125improveCO2removalinspaceaircraftapplications.Toenhancethesorptioncapacityofthispolymer,Songandco-workersdevelopeda“molecularbasket”system,usingamesoporoussilicasupportthatservedasabaskettoretainlargeamountsofPEI(Maetal.,2009).Thecharacteristicsoftheporoussupportintheseamine-impregnatedsorbentscanmakeveryimportantcontributionsinsorptionprocess,sincetheycanfacilitatemasstransporttotheframeworkpores,andthuscanpromoteefficienttransportofCO2tothecapturesites.Therefore,supportshavinglargeporevolumeandanopen,accessiblebackbonefortheimmobilizationofalargenumberofactivesorptionsitesforCO2captureshouldperformbetter.Mesoporouscarbons,havinghighsurfacearea,largeporevolumesandspecificsurfaceproperties,shouldbeagoodplatformfortheimpregnationoflargeamountsofamines.However,theapplicationofmesoporouscarbonsassupportforCO2capture,todate,isverylimited.Re-cently,ourresearchgroupdevelopedakindofmesoporouscarbonviaacombinationofhardtemplatingandsol-gelprocessing(Chenetal.,2011).Thesemesoporouscarbonspossessedawell-developedmesoporousstructurewithlargesurfacearea(800m2/g)andlargeporevolume(3cm3/g),makingthemquitewell-suitedasasupportinCO2capture.Hence,oneimportantgoalaswellasbigchallengeofthisworkistodevelopahighlyefficientmesoporouscarbon-basedCO2sorbentwhic