ASTM D86 DISTILLATION OF LIGHT HYDROCARBON SAMPLES – …

• ASTMD86requiresatleasta100mlsamplewhichmaynotalwaysbeavailableandinadditionmanylaboratoriesareactivelytryingtoreducethequantityofhighlyflammablesamplestheyprocess,analyseandstoreinthelaboratory.

• ASTMD86islabourintensiverequiringconstantoperatormonitoringandcontrolofthedistillationratethroughouttocomplywiththemethod.

• Ithasarelativelylongcycletime,afulldistillationcycleaccordingtoASTMD86requirementstakes29to39minutes,butmanylaboratoriesandprocessesrequirefasterresponsetimes.

• Themanualhandling,transferandphysicaldistillationofhighlyflammablesamplesinanopenlaboratoryposesasignificantsafetyrisk.

Asaresult,manylaboratoriesandsuppliershavelookedatfasterandsaferalternativeroutestoobtaincomparabledatatoASTMD86.SimulatedDistillation(SIMDIS)ofPetroleumproductsbygaschromatographyhasbeenwidelyacceptedbytheindustry,but

SIMDISisnotsuitedforlightendhydrocarbonsamplessuchasgasolineandnaphtha.

InthisarticlewelookatanapproachbasedonnovelmodellingsoftwarewithdetailedhydrocarbonanalysisbyfastgaschromatographytopredictD86resultsoflightendhydrocarbonsamplesincludinggasolines,alkylates,isomerate,reformate,FCCandnaphtha.

The Fugacity-Film Model for Predicting D86 Distillation of Gasolines and NapthasThetheoreticalbasisforthetechnologydescribedinthisarticle

wasfirstpublishedbyWalterSpieksma(2)whoconcludedthat

“D86distillationofnaphthaandgasolinecanbepredictedfrom

gaschromatographicdetailedhydrocarbonanalysisbyvirtueofthe

fugacity-filmmodel.Thefugacity-filmmodelisbasedonFick’sLaw

andHenry’sLaw.TheStillPeaksDHAfugacity-filmmodelofD86

distillationcanpredictexperimentallydeterminedboilingpoint

rangeswithinseveraldegreesCelsius.”

Repeatability and ReproducibilityInaninter-laboratorycrosscheckfivegasolinesfromASTMweremeasuredinduplicateby10labsusingthe5.8minuteFastGCDHAmethodandtheresultsoftheStillpeakssoftwarecomparedtothestandardASTMD86methodandtheRepeatabilityoftheStillPeaksDHAtoD86calculatedD86cutpointswas1°C.

ThereproducibilityofStillpeaksDHAtoD86iscomparabletoD86.TheDHAtoD86softwarecontainsseveralinnovationsinboththeDetailedHydrocarbonAnalysisandintheD86distillationcalculation.ThesoftwaresolutioncanbeappliedtoanytemperatureprogrammedGCmethodonaPhenyl-MethylSiliconecoatedcapillarycolumnandwithacoupleofmouse

ASTM D86 DISTILLATION OF LIGHT HYDROCARBON SAMPLES – CAN IT BE REPLACED BY GAS CHROMATOGRAPHY TO DELIVER AN AUTOMATED, FASTER AND SAFER ANALYSIS? –

Distillation limits are included in petroleum product specifications in all aspects of the supply chain from the refinery to product specification and regulatory compliance. ASTM D86 (1) is the basic test method of determining the boiling range of a petroleum product by performing a simple batch distillation and has been in use for as long as the petroleum industry has existed. It is one of the oldest test methods under the jurisdiction of ASTM Committee D02. However, it does have some significant drawbacks for use in modern petroleum laboratories including:

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Time consuming and potentially Hazardous ASTM D86 analytical distillation involves batch evaporation and thermometer droplet mass exchange.

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clickstheapplicationcananalyserunsofASTMD6729,D6730,D6733orthe5.8minuteFast-DHAmethod.TheStillPeaksDHA-reportoptimallyconnectstotheD86-partoftheapplicationandautomaticallyconstructsD86cutpointsforgasolineandblendfeedsamples.ThissoftwarecurrentlyreadsintegrationreportdatafromAgilent’sOpenLabandScionCompass,andispotentiallyopenforotherGCplatforms,avoidinganyconstraintswithcurrentinstrumentsandsoftware.

Detailed Hydrocarbon Analysis by Gas ChromatographyTheadventofgaschromatography(GC)inthelate1950sandespeciallythesubsequentdevelopmentofhigh-resolutioncapillarycolumnsandflameionisationdetectorsrevolutionisedthedetailedanalysisofhydrocarbonsamples.Thisallowedindividualcomponentresolutionandquantificationinsamples,generatingareportofretentiontimesandarea%ofintegratedpeaks.ThissubsequentlydevelopedintoDetailedHydrocarbonAnalysis(DHA),whichconvertsaGCintegrationreport(retentiontimesandarea%)intoaDHA-reportincludingretentionindexandweight%ofthehydrocarboncompoundsinthesample.TheDetailedHydrocarbonAnalysismethodsvaryfrom2.5hoursuptothefast5.8minutemethod.

AstheDHA-reportistheinputforthefugacity-filmmodel,thequalityoftheDHA-reportseverelyimpactstheD86distillationcalculationandthereforeoptimisingthefast5.8minuteGC-methodforDetailedHydrocarbonAnalysiswillimproveresults.

TemperatureProgrammedGCKovatsindexdatacanbecalculatedfromstableIsothermalKovatsindexdatabasedonVaporLiquidEquilibria(VLE)andtheGiddingsPeakmovemodelandSpieksmaintegratedthisintothepackagetomodeltheGCanalysis(VirtualGC)intheStillPeaksDHA-software.

Virtual GC in Detailed Hydrocarbon Analysis ThisVirtualGCmodulecalculatesthen-ParaffintimesandgeneratesalistofTemperatureProgrammedGC(TPGC)Kovatsindicesforpeakidentification.VirtualGCisauniquecomputedmodelofadimethylsiliconecoatedcapillarygaschromatographiccolumnusingtypicalGC-configurationinputsettingsandaKovats

IsothermalindexDatabase(KID).TheconfigurationsettingsinVirtualGCshouldmatchtheactualGCconfigurationforoptimalDHA-resultsandthesubsequentD86distillationreport.

StillPeaks DHATheDHAsoftwarealsocontainspatternrecognition,toluenedeconvolution,aswitchbetweenconstantinletpressureandoutletflowandtheflexibilitytorunsamplesusinganypredefinedorcustomtemperatureprogrammedGCmethodwhichemploysPhenyl-MethylSiliconewallcoatedcapillarycolumns(containingupto75%phenylgroupsinthephase).

StillPeaksDetailedHydrocarbonAnalysisincombinationwith

VirtualGCmodellingemploysaunique3-steppeakidentificationprocess:

•Peaksbiggerthan2%areidentifiedfirst,

•Patternrecognitionwithdeconvolutionofco-elutingpeaksisthenperformed,

•RemainingpeaksareidentifiedbycomparingthemeasuredandcalculatedTemperatureProgrammedKovatsindexdata

AsthetemperatureprogrammedGCKovatsindexdataisbeingcalculated,theapplicationalsocalculatesthen-Alkanesbasedonthemodelledtemperatureprogram,bleedandmethanetimewhichallowspeakidentificationinsampleswhenmeasuredn-Alkanesarenotpresent.

StillPeaks D86 calculationTheD86-partofthesoftwarefeaturesAutomaticSampleTypeAssignment(ASTA)whichidentifiesthesampletypeandassignsthecorrectsettingsforD86cutpointscalculationbasedonthecompositionofthesample.Upto15SampleTypescanbemanagedincludingcommonproductssuchasAlkylate,Isomerate,Reformate,Light-,Medium-,HeavyNaphtha,Light-,Medium-,HeavyFCC,RBOB,SummerGasolineandWinterGasoline.Inaddition,upto3customoptionscanbemanuallyenteredsuchthattheD86settingsofyour‘typically’expectedcutpointscanbepredefined.

Inaddition,StillPeakshasaddedthevariables‘SampleTemperature’and‘HeaterTemperature’tomodelthephysicalASTMstandardD86methodinevenmoredetailandalsotheoptionstovarybarometricpressure,whichimpactsboilingpointsingeneral,andthepossibilitytoadjustthethermometerEonumberasdropletsizeshiftsthedewpointcurve.

Asaresult,monitoringD86resultaccuracyiseasierthaneverthroughone-to-onemonitoringwhenD86cutpointsareavailableorwiththeoptiontoset‘TypicalOffsetsperSample-Type’forone-to-manymonitoring.Italsoincludestheoptiontomonitoragainstinter-laboratorycrosscheckdatawithdeltaandz-scorespresented.

DHA GC Method Development, Validation and Additional Capabilities by Virtual GCTheStillPeaksVirtualGCsoftwarealsomakesitaloteasiertocomparetheperformanceofanytemperatureprogrammedGCmethodtherebysimplifyingmethoddevelopmentandvalidationofin-housemethods.Forexample,comparingthe5.8minuteFastDHAmethodwiththe3hourASTMD6730(3)withbetterseparation,resultsinonlyamarginallybettercalculatedD86cutpoints.FormostofGasolineanalysisthe5.8minuteFastDHAmethodprovidessufficientinputforthecalculationofacceptableD86cutpoints.ThesoftwarealsohasthecapabilitytoconfirmthatIsomerateandAlkylateblendfeedshavenonon-isomerco-elutionsevenonthe5.8minuteFast-DHAmethod

StillPeaks D86 Kovats Index plot versus Pure Liquid Boiling Point

StillPeaks DHA Peak Identification: Pattern recognition example for identifying C8-aromatics

StillPeaks Virtual GC method illustration for ASTM D 6729 of CH4 to 224TMP from Isothermal Kovats Index and Giddings PeakMove TPGC model

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Summary and ConclusionsThecombinationofthe5.8minuteFast-GCmethodandStillPeaksDetailedHydrocarbonAnalysiswiththeStillPeaksD86applicationhasshowntoreliablypredictD86cutpointsofgasolinesandlighthydrocarbonblendfeeds.

ThisapproachsignificantlyovercomesmanyofthedrawbacksoftheconventionalD86distillationmethod.Samplevolumescanbedramaticallyreducedfromhundredsofmillilitrestotensofmicrolitresresultinginsignificantsafetyimprovementsandriskreductionfromthehandling,processingandstorageofhighlyvolatilesamplesinthelaboratory.Thisalsomeansthemethodisapplicabletosituationswheresamplevolumesarelimitedsuch

asinhighthroughputcatalystscreening.ThefastDHAmethodreducessampleanalysistimebycircaafactorof5resultinginfasterresultturnaroundandhigherthroughput.Inadditiontheanalysiscanbeautomatedandruninbatches,removingtheneedforconstantoperatormonitoringandcontrolandallowinganalysestoberununattendedinthesilenthours.

TheStillPeaksDHAtoD86applicationemploysacombinationofuniquemodellingtechniquesandestablishedtheorytoconstructD86distillationcutpointsandphysicalpropertiesofgasolineandblendfeedsamples.TheapplicationscanbeemployedwithanyGCisfullysupported,quicktodownloadandeasytoinstall.

Future DevelopmentsTheuniqueapproachofmodellingGCperformancecombinedwiththeoreticalcorrelationstophysicalandperformancecharacteristicscouldhavemanyotherfutureapplicationsforarangeofsampletypesandthesearecurrentlyunderdevelopment.ThefatheroftheDHAtoD86application,WalterSpieksma,admitstobeinginterestedinallkindsofmoreenvironmentallyfriendlyfuelsandgasolinetypesbasedontheFischer-Tropschandothersimilarprocesses.IfyouwouldliketodiscusspossiblefutureapplicationsofthistypeofapproachpleasecontactStillPeaksdirectlybyemail(info@StillPeaks.com)orviatheirwebsiteStillPeaks.com(https://stillpeaks.com)

AcknowledgementsTheauthorwouldliketoacknowledgethevaluablecontributionsandinputfromWalterSpieksmaandMichaelNijdamofStillPeaksinthepreparationandwritingofthisarticle.

References1.ASTMD86–18:StandardTestMethodforDistillationofPetroleumProductsandLiquidFuelsatAtmosphericPressurehttps://www.astm.org/Standards/D86

2.PredictionofASTMMethodD86DistillationofGasolinesandNaphthasaccordingtotheFugacity-FilmmodelfromGasChromatographicDetailedHydocarbonAnalysis,WalterSpieksma,JournalofChromatographicScience,Vol.36,September1998http://chromsci.oxfordjournals.org/content/36/9/467.full.pdf

3.ASTMD6730-01(2016)StandardTestMethodforDeterminationofIndividualComponentsinSparkIgnitionEngineFuelsby100–MetreCapillary(withPrecolumn)High-ResolutionGasChromatographhttps://www.astm.org/Standards/D6730.htm

StillPeaks Distillation Curve and Cut Points calculated from Fast GC Detailed Hydrocarbon Analysis of Gasoline with Ethanol

Author Contact DetailsTom Lynch CSci, CChem FRSC, Independent Analytical Consultant, Cricket House, High St, Compton, Newbury, RG20 6NY • Email: tomlynch.lynch@btinternet.com