1、Designation: D 7347 07An American National StandardStandard Test Method forDetermination of Olefin Content in Denatured Ethanol bySupercritical Fluid Chromatography1This standard is issued under the fixed designation D 7347; the number immediately following the designation indicates the year oforigi
2、nal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the totalamount of
3、 olefins in denatured ethanol to be used as anoxygenate additive in blended spark ignition engine fuels. Themethod of determination is supercritical fluid chromatography(SFC). The application range is from 0.1 to 1.0 mass percenttotal olefins. Results are expressed in terms of mass percentolefins.1.
4、2 This test method can be used for the analysis ofdenatured ethanol that is intended to be used as an oxygenateadditive in commercial spark ignition engine fuels.1.3 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.4 This stan
5、dard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 A
6、STM Standards:2D 4052 Test Method for Density and Relative Density ofLiquids by Digital Density MeterD 5186 Test Method for Determination of the AromaticContent and PolynuclearAromatic Content of Diesel Fuelsand Aviation Turbine Fuels By Supercritical Fluid Chro-matographyD 6550 Test Method for Dete
7、rmination of Olefin Content ofGasolines by Supercritical-Fluid Chromatography3. Terminology3.1 Definitions:3.1.1 critical pressure, nthat pressure needed to condensea gas at the critical temperature.3.1.2 critical temperature, nhighest temperature at whicha gaseous fluid can be converted to a liquid
8、 by means ofcompression.3.1.3 supercritical fluid, nfluid maintained in a thermo-dynamic state above its critical temperature and critical pres-sure.3.1.4 supercritical fluid chromatography, nclass of chro-matography that employs supercritical fluids as mobile phases.4. Summary of Test Method4.1 A s
9、mall aliquot of the denatured alcohol sample isinjected onto a set of three analytical chromatographic columnsconnected in series. The sample is transported through thecolumns using supercritical carbon dioxide (CO2)asthemobile phase. The first column is packed with polyvinylalcohol (PVA). The secon
10、d column in the series is an analyticalcolumn packed with high surface area silica gel particles, andthe third column is packed with silica particles coated withstrong cation exchange material loaded with silver ions.4.2 Two six-port switching valves are used to direct thedifferent classes of compon
11、ents through the chromatographicsystem to the detector. In a forward flow mode, saturates,aromatics, and olefins pass onto the analytical silica gel columnwhile the alcohol is retained on the PVAcolumn. The saturates,aromatics, and olefins are maintained on the silica column,while the alcohol is bac
12、k-flushed to the detector. This step freesthe flow path of alcohol species allowing for the separation ofthe olefins from saturates and aromatics. The forward flowmode is resumed after the alcohol is eliminated and saturatesare carried to the detector, while the aromatics are retained onthe silica c
13、olumn and the olefinic species are trapped on thesilver-loaded column. The next step is to back-flush the olefinsfrom the silver-loaded column to the detector. Finally thearomatics are carried from the silica column to the detector ina forward flow mode, bypassing the silver-loaded column.1This test
14、 method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.04.0C on Liquid Chromatography.Current edition approved Aug. 1, 2007. Published September 2007.2For referenced ASTM standards, visit the ASTM website, www.a
15、stm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.3 A f
16、lame ionization detector (FID) is used for quantita-tion. Calibration is based on the area of the chromatographicsignal for olefins, relative to standard reference materials,which contain a known mass percent of total olefins ascorrected for density.5. Significance and Use5.1 Olefinic hydrocarbons t
17、hat may be present in denaturedethanol have been demonstrated to contribute to photochemicalreactions in the atmosphere, and this can result in the formationof smog in susceptible urban areas.5.2 The California Air Resources Board (CARB) has speci-fied a maximum allowable limit of total olefins in s
18、parkignition engine fuel. Denatured ethanol will be added at theterminals as an oxygenate additive and can contain olefinicspecies contributing to the total olefins present in spark ignitionengine fuel. An analytical method is therefore necessary todetermine total olefins in denatured ethanol intend
19、ed for sparkignition engine fuel use. The test method is intended to be usedby both regulators and producers.5.3 The present test method is automated, does not requireany sample preparation, and has a relatively short analysis timeof approximately 20 min.6. Apparatus6.1 Supercritical Fluid Chromatog
20、raph (SFC)Any SFCinstrumentation can be used that has the following character-istics and meets the performance requirements specified inSection 8.NOTE 1SFC instruments suitable for Test Method D 6550 are suitablefor this test method if equipped with a second column heater as describedin 6.1.5.1 and
21、columns as described in 6.1.4.6.1.1 PumpThe SFC pump shall be able to operate at therequired pressures (typically up to about 30 MPa) and delivera sufficiently stable flow to meet the requirements of retentiontime precision (better than 0.3%) and detection background(Section 8). The characteristics
22、of the pump largely determinethe optimum column diameters. Columns with an insidediameter of 1.0-mm ID require a pump flow capacity ofapproximately 50-L/min of liquid carbon dioxide, whereascolumns with an inside diameter of 4.6-mm require a pumpcapacity of at least 1-mL/min of liquid carbon dioxide
23、.6.1.2 DetectorsA flame-ionization detector (FID) is re-quired for quantitation. A flow restrictor shall be installedimmediately before the FID. The restrictor serves to maintainthe required pressure in the column, while allowing the pumpand detector to perform as specified in 8.2.6.1.3 Sample Inlet
24、 SystemA liquid-sample injection valveis required that is capable of introducing a sub-microlitervolume with a precision better than 0.5%. A 0.200 to 0.060-Linjection volume was found to be adequate in combination with1-mm diameter columns. The sample inlet system shall beinstalled and operated in a
25、 manner such that the chromato-graphic separation is not negatively affected.6.1.4 ColumnsThree columns of equal inside diameter arerequired:6.1.4.1 A high surface area silica column, capable of sepa-rating alkanes and olefins from aromatics as specified inSection 8. Typically, a 50-cm long, 1-mm in
26、ternal diameter, ora 25-cm, 4.6-mm internal diameter column is used. Thiscolumn is packed with particles having an average diameter of5-m or less, 600-nm (60-) pores, and a surface area of$350-m2/g.NOTE 2Columns suitable for Test Method D 5186 and D 6550 arealso suitable for this test method. Source
27、s and typical dimensions areshown in Table 1.6.1.4.2 A silver-loaded silica or cation exchange columncapable of separating olefins from alkanes. Typically, a 5-cmlong by 1-mm internal diameter column packed with particleshaving an average diameter of 5-m is used for the analysis.NOTE 3Silver-loaded
28、silica columns suitable for Test Method D 6550are also suitable for the present method. Sources and typical dimensionsare shown in Table 1.6.1.4.3 A polyvinylalcohol (PVA) column capable of sepa-rating alkanes, olefins, and aromatics from alcohol. Typically,a 5cm long by 1mm or 4.6mm internal diamet
29、er columnpacked with PVA particles is used for the analysis.NOTE 4PVA columns that have been used successfully are shown inTable 1.6.1.5 Column-Temperature ControlThe chromatographshall be capable of controlling column temperature to within0.5C or less.6.1.5.1 A secondary column heater mounted in th
30、e columnchamber can be used to heat the silver-loaded column inde-pendently of the silica and PVA columns. This supplementalheating is recommended for faster clearance of the olefins andsaturates from the silver-loaded column. The supplementalcolumn heater box is typically maintained at 150C.6.1.6 C
31、omputer or Electronic IntegratorMeans shall beprovided for the determination of accumulated peak areas. Thiscan be done by means of a computer or electronic integrator.The computer or integrator shall have the capability of correct-ing for baseline shifts during the run.6.1.7 Switching ValvesTwo six
32、-way switching valves areconfigured in accordance with the scheme shown in Figs. 1-4.Four different positions are shown in these figures and aredefined as follows:6.1.7.1 Position LC (Load Column)PVA column (forwardflush mode), silver column (forward flush mode), and silicacolumn (forward flush mode
33、) connected in series. The flowenters the PVAcolumn first, then the silica column second, andthe silver-loaded silica column third. This position is used to(1) inject the sample onto the columns and (2) retain theTABLE 1 Typical ColumnsColumn Type: PVA Silica Silver-loaded silicaVendor: Selerity,Wat
34、ersCorporationSelerity, Merck Selerity,Hypersil,PhenomenexPacking material: PVA High surfacearea silicaparticlesCation exchangeParticle size, m: 5 5 5Length, mm: 50 500, 250 50Internal diameter,mm:1, 4.6 1, 4.6 1, 4.6D7347072alcohol on the PVA column while allowing all other species topass onto the
35、silica column. After the alcohol is flushed fromthe system in Position BE (back-flush ethanol) this positionwill again be used to (1) elute the saturates, (2) load the olefinsonto the silver-loaded silica column, and (3) retain the aromat-ics on the silica column (see Fig. 1).6.1.7.2 Position BE (Ba
36、ck-Flush Ethanol)PVA column(back-flush mode). This position directs the flow from the PVAcolumn to the detector. The silica and silver-loaded silicacolumns are not in the flow path. The alcohol is eluted in thisposition (see Fig. 2).6.1.7.3 Position BO (Back-Flush Olefins)The silica col-umn is not i
37、n the flow path. The PVA(back-flush mode) and thesilver-loaded silica (back-flush mode) columns are connectedin series. The olefinic species are eluted in this position (seeFig. 3).6.1.7.4 Position EA (Elute Aromatics)PVA column (for-ward flush mode), silver column (forward flush mode), andsilica co
38、lumn (forward flush mode) connected in series. Theflow enters the PVA column first, then the silver-loaded silicacolumn second, and the silica column third. This positiondiffers from position LC in that the silica column is the lastcolumn in the series. The aromatics are eluted to the detector inthe
39、 forward flow mode (see Fig. 4).7. Reagents and Materials7.1 AirZero-grade (hydrocarbon-free) air is used as theFID oxidant. (WarningAir is usually supplied as a com-pressed gas under high pressure, and it supports combustion.)7.2 Calibration SolutionAn ethanolic mixture containingolefins of a known
40、 mass % of the type found in typicaldenatured alcohol. An example of this mixture would be99.50% ethanol, 99.995% purity and 0.50% olefin solutioncontaining 2-pentene, 1-hexene and cyclohexene.7.3 Carbon Dioxide (CO2)Supercritical fluid chromato-graphic grade, 99.995% minimum purity, supplied pressu
41、rizedin a cylinder with a dip tube for removal of liquid through aCGA 320 fitting. (WarningLiquid at high pressure. Releaseof pressure results in production of extremely cold, solid CO2and gas, which can dilute available atmospheric oxygen.)7.4 HydrogenHydrogen of high quality (hydrocarbonfree) is u
42、sed as the fuel for the FID. (WarningHydrogen isusually supplied under high pressure and is extremely flam-mable.)7.5 Loading-Time MixturesFour loading time mixturesare recommended to determine the switching times for this testmethod and to protect the silica column from exposure toethanol and the s
43、ilver-loaded column from contamination byaromatics and ethanol.7.5.1 Loading-Time Mixture AA mixture of 10 % alkanes(n-hexane and cyclohexane), 10 % aromatics (benzene, tolu-ene, and naphthalene), and 80 % ethanol can be used todetermine the loading time of saturates, olefins, and aromaticsonto the
44、silica column while protecting the silica and silver-loaded column from ethanol contamination.FIG. 1 Valve Position LCLoad Columns, Step 1 and 3FIG. 2 Valve Position BEBack-flush PVA, Step 2FIG. 3 Valve Position BOBack-flush silver-loaded column,Step 4FIG. 4 Valve Position EAHigh Resolution of Aroma
45、tics, Step 5D73470737.5.2 Loading-Time Mixture BA mixture of 10 % alkanes(n-hexane and cyclohexane), 7 % aromatics (benzene, toluene,and naphthalene), 3 % olefins (2-pentene, 1 hexene, andcyclohexene) and 80 % ethanol can be used to determine theloading time of saturates and olefins onto the silver-
46、loadedcolumn and protect it from aromatic contamination.7.5.3 Loading-Time Mixture CA mixture of 7 % alkanes(n-hexane and cyclohexane), 3 % olefins (2-pentene, 1 hexene,and cyclohexene), and 90 % ethanol can be used to establishthe elution time of the olefins from the silver-loaded column tothe dete
47、ctor in the back-flush mode.7.5.4 Loading-Time Mixture DA mixture of 10 % alkanes(n-hexane and cyclohexane) and 90 % ethanol can be used tocheck the absence of saturates on the silver-loaded columnduring the elution of olefins.7.5.5 Loading-Time Mixture EA mixture of 10 % aromat-ics (benzene, toluen
48、e, and naphthalene) and 90 % ethanol canbe used to check the absence of aromatic contamination on thesilver-loaded column.7.6 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committe
49、e onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.3Other grades can be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.7.7 Performance MixtureA mixture of alkanes (n-hexaneand cyclohexane), mono-aromatics (benzene and toluene), andpoly-nuclear aromatic (naphthalene) at no more that 10 % byweight and mono-olefins (2-pentene, hexene, and cyclohexene)at no more than 2 % by weight in chromat
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