DOC

Inverse

By Kyle Ray,2014-11-07 23:55
10 views 0
Inverse

    Inverse

    200711

    November2007

    色谱

    ChineseJournalofChromatography

    Vo1.25N0.6

    871(875

    InverseGasChromatographicStudyoftheOxidationStabilityof

    LubricatingBaseOilsviaSolubilityParamleterCalculations

    MOUSTAFANagyEmamEISSAElhamAhmed

    (ByYPtianPetroleumResearchInstitute,NasrCity,Cairo,Byypt)

    Abstract:TheFlory-Hugginsinteractionparameter(2)andsolubilityparameter(2)anditshydrogenbond_

    ingsensingcomponent(h)weredeterminedusinginversegaschromatography(IGC).Theseparameterswere

    successfullyusedintheprobesofchemicalchangesthatoccurduringtheoxidationofnaphthenicandparaffinic

    baseoilsinaGCcolumn.Changesin,valuesreflectthedifferenttypesofintermolecularinteractions(dis-

    persive,polar,hydrogenbonding)ofthegivenlubricatingbaseoilduringoxidation.Theobtainedresults

    showedthathcomponentofsolubilityparameteristhemostimportantparameterforprobingtheoxidative-

    chemicalchangesduringtheoxidationofgivenlubricatingoils.

    Keywords:inversegaschromatography;lubricatingnaphthenicbaseoil;oxidation CLCnumber:0658Documentcode:AArticleIC:1000-8713(2007)06-0871-05Column:Articles

    Oneofthemostimportantpropertiesfor evaluatinglubricatingoilsisthethermooxidative

    stability.Lubricantsuppliersandusersrelyonac

    celeratedlaboratoryteststodeterminetheoxida

    tivestabilityoflubricants.Numeroustestshave beenconductedtounderstandthemechanismof lubricantoxidation.Inversegaschromatogra

    phy(IGC)isalsousedtofollowuptheoxidation process.DavisandPetersenL2Jhaveused"inter- actioncoefficient"forcharacterizingasphaltoxi

    dation.EvansandNewtonl'haveused"reten. tionindex"formonitoringtheoxidationof squalaneasmodelcompoundofnaturalrubber. SenandKumerL5havealsoused"retentionin

    dex"formonitoringtheoxidationstabilityofthe lubricantaloneandinthepresenceofantioxida

    nts.TheIGCmethodhastheadvantageofcontin

    ualmonitoringoftheoxidationprocessbyasin

    gleretentionparameter.

    Theaimofthepresentworkistocompare

    theoxidationstabilityofnaphthenicandparaffinic baseoilviaprobingchemicalchangesthatOccur duringlubricatingbaseoiloxidationbythecalcu

    lationoftheFlory-Hugginsandsolubilityparame?- ters.

    1Theory

    Tostudyoiloxidationofthinfilms,itismore convenienttoprobephysicochemicalchanges

    suchaspolarity,carbonylandhydroxylcontents, thattakeplacewiththeoxidationtime.Ithas

    beenshowninnumerousstudiesthatthepolarity changescanbeconvenientlymonitoredby IGC..InIGCmethod.theinvestigatedmate. rial(stationaryphase)isplacedintothechroma- tographiccolumn.Thevolatilecompounds(test solutes,areinjectedintothecolumnandtrans

    portedovertheexaminedmaterialbythecarrier gas.Eachtestsoluteinteractswithinvestigated materia1.Magnitudeofthisinteractionreflectsin thevalueofspecificretentionvolume(Vg)andis furtherpresentedastheFloryHugginsinteraction

    parameter(2).

    Thismethodhasbeenappliedforthecharac

    terizationofawiderangeofmaterials,e.g.poly

    mers[

    .

    surfactants_l2l

    ,

    pharmaceuticalpow.

    dersandotherpharmaceuticalproductsandpor- OUSsolids[.Therelationshipsbetweenchroma- tographicandthermodynamicparametersaregiv- eninthetermofxT,213]:

    =

    In(273.15Rl(pVgM.))pV(RT)?

    (BV)+In(Pi/p)(1VV)(1)

    where1denotesthesolute,2denotestheexam

    inedmaterial,Mlistherelativemolecularmassof thesolute(g/mo1),Tistheexperimentaltem

    perature,Pisthesaturatedvaporpressureofthe

    solute(Pa),B】】isthesecondvirialcoefficientof thesolute(cm/mo1),Visthemolarvolume (cm/mo1),Piisthedensity(g/cm)andRis thegasconstant(J/(mol?K)).

    Voelkeleta1.andGuilleteta1._l7]pro. Receiveddate:2007-O6-l5

    Correspondingauthor:MOUSTAFANagyEmam,E-mail:nemoustaf@yahoo.tom

?

    872?色谱第25

    posedthemethodforestimatingthesolubilitypa- rameter(ofsolventbythefollowingequation: /(RT)-X(.-2]/=282/(RT)'

    6.6i/(RT)(2)

    whereiisadonationofthegivensolute,6"isthe solubilityvalueofthesolutei,62isthesolubility valueofthestationaryphase.Ifthelefthandside ofequation(2)isplottedagainst28astraight

    linehavingaslopeof62/(RT)andaninterceptof

    /(RT)willbeobtained.Thesolubilitypa- rametercanbecalculatedfromtheslopeorthe interceptofthestraightline.

    Thecomponentsofthesolubilityparameters 62werecalculatedfromtheslopeofthestraight linefortherespectivegroupsofsolventsrepre

    sentingdifferentmolecularinteractions.These valueswerecalculatedbyusingthefollowingrela

    tionshipsll8:

6d=m(lkan.?RT/2(3)

    8.=(m.m..)'RT/2(4)

    6h=(m2m...)'RT/2(5)

    where6d,6.,and6harethedispersive,polarand hydrogenbondingcomponentsofthegivensolu

    bility,respectively.m.

    lk.

    isthevalueofthe

    slopefornalkanes;mlistheslopeforthearo

    matichydrocarbons,ketones,1nitropropane,

    acetonitrileand1,2-dichloroethane;m2isthe slopeforalcohols,1,2-dioxane,pyridineand chloroform.Asthelubricatingoiloxidationgen

    eratesoxygencontainingcompounds,6hsolubility componentisthemostsuitableparameterforpro

    bingthechemicalchangesduringtheoxidationof lubricatingoil.

    2Experimental

    2.1Theusedlubricatingbaseoils

    Thestudiedlubricatingbaseoilswerekindly providedbyMiserPetroleumCo.,Cairo,Egypt. TheirspecificationsaregiveninTable1. Theseoilswereoxidizedinchromatographic columnsat100?withanoxygenflowrateofl0

    mL/min.

    2.2Apparatusandprocedure

    APerkinElmerSigma3Bgaschromatograph equippedwithflameionizationdetector(FID) wasusedtoevaluatetheoxidizedoilsasstationa

    ITphasesinpackedcolumns.Asampleof2.5g

    ofeachoilwasdissolvedin40mLofpetroleum Table1Physicochemicalcharacteristicsof theexaminedbaseoils

    ether(b.r.6080?)andthoroughlymixed

    with25gofChromosorbP(80100meshsize),

    followedbytheevaporationofpetroleumether. Accordingly,10%coatedsupportwasobtained. Thiscoatedsupportwaspackedinto1/4x6.5 stainlesssteelcolumns.Thepackedcolumns wereconditionedovernightat140?atanitrogen

    flowrateof2OmL/minbeforeuse.

    Thefollowingcompoundswereusedasthe testsolutes:dispersivesolutes:C5C9nal

    kanes;polarsolutes:acrylonitrile,tolueneand cisdecaline,butylacetate,4methyl2pen~tanone

    andacetophenone;hydrogenbondingsolutes: phenol,cyclohexanol,nbutanol,propionicacid,

    pyridineandbenzylalcoho1.Thesetestsolutes

    wereinjectedindividuallyunderthefollowingGC conditions:oventemperature120?,injectorand

    detectortemperatures200and250?respective

    ly,nitrogenflowrate14mL/min,samplesize 1L.

    3Resultsanddiscussion

    Thisstudyisbasedonthevariationsof2 and6hparametersforasetofselectedtestsolutes toresponsethechemicalchangesthatoCcurdur- ingtheoxidationofthenaphthenicandparaffinic baseoils.Tables2and3givethe2valuescal

    culatedonexaminednaphthenicandparaffinic

baseoilsoxidizedfor010and06h,respec

    tively.TheX~,2valuesmaybeusedfortheestima- tionofthemutualmiscibilityoftheexamined baseoilandthegiventestsolute.Twospecies (oilandtestsolute)willbemiscibleifXT.20.

    6MOUSTAFANagyEmam,eta1.:InverseGasChromatographicStudyoftheOxidation StabilitvofLubricatingBaseOilsviaSolubilityParameterCalculations'6,j'

    For20,onemayexpectlimitedmutualsolu

    bilityofthetestsoluteandtheexaminedbaseoil. The2valuesdeterminedfortheoxidizedbase oilswiththeuseofdispersive,polarandhydro

    genbondingsolutesarealwaysnegative(2

    0)withafewexceptions(Tables2and3).This meansthattheexaminedoilsandtestsolutesare mutuallymiscible.

    Table22valuesat100?fornaphtheniclubricating

    oiloxidizedatdifferenttimes

    Table32valuesat100?forparaffiniclubricating

    oiloxidizedatdifferenttimes

    Fortheexaminednaphthenicbaseoil(Table 2),itcanbeobservedthatthelargestvariations oftheFloryHugginsinteractionparametersare foundforthehydrogenbondingtestsolutes. Thesehighvaluesreflecttheincreasingmiscibility oftestsoluteoxidizedoil.whichresultfromthe formationofoxygencontainingfunctionalgroups duringtheoxidationofbaseoilfor1l0h.The

2valuesaredirectlyproportionaltotheoxida

    tiontime.Thisgiveanindicationaboutthepoor oxidationstabilityofnaphthenicbaseoilasitcan

    notresistoxidationforonehour.Thegivenhy

    drogenbondingtestsolutescanbeorderedas phenol>cyclohexanol>propionicacid>nbu

    tanolpyridineaccordingtotheincreaseofthe 2

    valueatanoxidationtimeofl0h.According

    ly,phenolisconsideredasthemostsuitablehy

    drogenbonding--testsoluteamongtheusedsol-- utesthatrespondtothestartingofchemicalchan

    gesduringtheoxidationprocess,inotherwords, forthedeterminationofthelubricatingoilinduc

    tionperiod.

    Comparatively.forpolartestsol

    utes,2valuesslightlyincreasewiththelubrica

    tingbaseoiloxidation.whichreflectsalowerde

    greeofinteractionwiththeexaminedoxidizedlu

    bricatingoil.Itcanbenoticedthatthestrongest interactions(goodoxidizedlubricatingoilmisci

    bility)arefoundforcisdecaline.Thistestsolute

    exhibitsthehighestnegativevalueatalltimeof oxidations.Fornonpolartestsolutes,2values

    exhibitlessnegativevaluesduringoxidation. FromTable3,itcanbeobservedthatthe variationsofx~.2interactionparameterfornonpo

    lar,polarandhydrogenbondingsoluteswiththe oxidationtimehaveasimilartrendforthenaph

    thenicbaseoiloxidationwithsmalldegreeof

    changes,whichreflectsthemoreresistanceof theparaffinicbaseoiltooxidationcomparedwith thenaphthenicbaseoil.

    Muchmoreconvenientisthecomparisonof thevaluesofsolubilityparameter,62.Particular- ly,thehydrogenbondingprobingcomponentof solubilityparameter,6h.Thecalculatedvaluesof 62,5dand6hparametersfortheexaminedoxi

    dizedbaseoilsaregiveninTables4and5.Figs. 1and2representanexemplifiedplotforthese calculatedparametersofexaminedlubricatingoils accordingtoEq.(2).Fig.3representstherela tionshipbetweenthevaluesof6hparameterand oxidationtimefortheexaminedlubricatingoils.

?

    874?色谱第25

    0xidationofthenaphthenicbaseoilcausesa largeincreasein6hvaluesinthe1l0htime

    range,where6hvalueincreasesfrom0.7753to 1.3956(J/cm)after1hofoxidation,where

    as,oxidationoftheparaffinicbaseoilcausesin

    significantchangein6hvaluesuptothreehours, whichcanbetakenastheinductionperiodofthe oxidation.6hvalueincreasesfrom6.9779to 7.5982(J/cm)after3hofoxidation.Moreo

    ver,theincreasesin?6hafter5hofoxidationare

    9.2426and5.8925fJ/cm)fortheoxidized naphthenicbaseoilandparaffinicbaseoil,re

spectively.Sobesidesinductionperioddetermi

    nation,therateofrise6hVS.oxidationtimerela- tionshipcanbepresumedastherateofoiloxida- tion,whichisalsoimportantinthedetermination ofthecomparativeoveralloxidationofbothex

    aminedlubricatingoils.Asexpected,boththese factorsshowcomparativelyhigheroxidationsta

    bilityfortheexaminedparaffinicbaseoil.Fur- thermore,thepresenceofsulfurcompounds, whichactasanaturalinhibitor,mightalsohave contributionstowardsitsoxidationstability. Table4Changesinthevaluesofsolubilityparameter andtheircomponentswiththeoxidation

    ofnaphthenicbaseoil

    Table5Changesinthevaluesofsolubilityparameter andtheircomponentswiththeoxidation

    ofparafflnicbaseoil

    Also,itcanbeseenfromFig.3thatthe

    differenceinthe6hvaluesfortheoriginalexam

    inedoilscorrespondtotheconcentrationofhy- drogenbondingcomponentscontainingparaffinic O.25

    O.2O

    O.15

    O.1O

    O.O5

    18192O21222324

    2/(J/cm)"

    Fig.1DeterminationofthetotalsolubiHtyparameter oftheoxidizedparaffinicbaseoilafter2h

Report this document

For any questions or suggestions please email
cust-service@docsford.com