1、Designation: D7347 071D7347 15Standard Test Method forDetermination of Olefin Content in Denatured Ethanol bySupercritical Fluid Chromatography1This standard is issued under the fixed designation D7347; the number immediately following the designation indicates the year oforiginal adoption or, in th
2、e case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1 NOTEAdded research report footnote to Section 13 editorially in October 2008.1. Scope Scope*1.1
3、This test method covers the determination of the total amount of olefins in denatured ethanol to be used as an oxygenateadditive in blended spark ignition engine fuels. The method of determination is supercritical fluid chromatography (SFC). Theapplication range is from 0.1 mass percent to 1.0 mass
4、percent total olefins. Results are expressed in terms of mass percent olefins.1.2 This test method can be used for the analysis of denatured ethanol that is intended to be used as an oxygenate additive incommercial spark ignition engine fuels.1.3 The values stated in SI units are to be regarded as t
5、he standard. The values given in parentheses are for information only.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the
6、 applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D4052 Test Method for Density, Relative Density, and API Gravity of Liquids by Digital Density MeterD5186 Test Method for Determination of theAromatic Content and PolynuclearAromatic Content of Diesel Fue
7、ls andAviationTurbine Fuels By Supercritical Fluid ChromatographyD6550 Test Method for Determination of Olefin Content of Gasolines by Supercritical-Fluid Chromatography3. Terminology3.1 Definitions:3.1.1 critical pressure, nthat pressure needed to condense a gas at the critical temperature.3.1.2 cr
8、itical temperature, nhighest temperature at which a gaseous fluid can be converted to a liquid by means ofcompression.3.1.3 supercritical fluid, nfluid maintained in a thermodynamic state above its critical temperature and critical pressure.3.1.4 supercritical fluid chromatography, n class of chroma
9、tography that employs supercritical fluids as mobile phases.4. Summary of Test Method4.1 Asmall aliquot of the denatured alcohol sample is injected onto a set of three analytical chromatographic columns connectedin series. The sample is transported through the columns using supercritical carbon diox
10、ide (CO2) as the mobile phase. The firstcolumn is packed with polyvinyl alcohol (PVA). The second column in the series is an analytical column packed with high surfacearea silica gel particles, and the third column is packed with silica particles coated with strong cation exchange material loadedwit
11、h silver ions.1 This test method is under the jurisdiction ofASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of SubcommitteeD02.04.0C on Liquid Chromatography.Current edition approved Aug. 1, 2007Dec. 1, 2015. Published September 2007February 2
12、016. Originally approved in 2007. Last previous edition approved in 2007 asD7347 071. DOI: 10.1520/D7347-07E01.10.1520/D7347-15.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information
13、, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict a
14、ll changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,
15、100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.2 Two six-port switching valves are used to direct the different classes of components through the chromatographic systemto the detector. In a forward flow mode, saturates, aromatics, and olefins pass onto the anal
16、ytical silica gel column while the alcoholis retained on the PVA column. The saturates, aromatics, and olefins are maintained on the silica column, while the alcohol isback-flushed to the detector. This step frees the flow path of alcohol species allowing for the separation of the olefins from satur
17、atesand aromatics. The forward flow mode is resumed after the alcohol is eliminated and saturates are carried to the detector, whilethe aromatics are retained on the silica column and the olefinic species are trapped on the silver-loaded column. The next step isto back-flush the olefins from the sil
18、ver-loaded column to the detector. Finally the aromatics are carried from the silica column tothe detector in a forward flow mode, bypassing the silver-loaded column.4.3 A flame ionization detector (FID) is used for quantitation. Calibration is based on the area of the chromatographic signalfor olef
19、ins, relative to standard reference materials, which contain a known mass percent of total olefins as corrected for density.5. Significance and Use5.1 Olefinic hydrocarbons that may be present in denatured ethanol have been demonstrated to contribute to photochemicalreactions in the atmosphere, and
20、this can result in the formation of smog in susceptible urban areas.5.2 The California Air Resources Board (CARB) has specified a maximum allowable limit of total olefins in spark ignitionengine fuel. Denatured ethanol will be added at the terminals as an oxygenate additive and can contain olefinic
21、species contributingto the total olefins present in spark ignition engine fuel. An analytical method is therefore necessary to determine total olefins indenatured ethanol intended for spark ignition engine fuel use. The test method is intended to be used by both regulators andproducers.5.3 The prese
22、nt test method is automated, does not require any sample preparation, and has a relatively short analysis time ofapproximately 20 min.6. Apparatus6.1 Supercritical Fluid Chromatograph (SFC)Any SFC instrumentation can be used that has the following characteristics andmeets the performance requirement
23、s specified in Section 8.NOTE 1SFC instruments suitable for Test Method D6550 are suitable for this test method if equipped with a second column heater as described in6.1.5.1 and columns as described in 6.1.4.6.1.1 PumpThe SFC pump shall be able to operate at the required pressures (typically up to
24、about 30 MPa) 30 MPa) anddeliver a sufficiently stable flow to meet the requirements of retention time precision (better than 0.3%)0.3 %) and detectionbackground (Section 8). The characteristics of the pump largely determine the optimum column diameters. Columns with an insidediameter of 1.0-mm1.0 m
25、m ID require a pump flow capacity of approximately 50-L/min50 Lmin of liquid carbon dioxide,whereas columns with an inside diameter of 4.6-mm4.6 mm require a pump capacity of at least 1-mL/min1 mLmin of liquidcarbon dioxide.6.1.2 DetectorsA flame-ionization detector (FID) is required for quantitatio
26、n. A flow restrictor shall be installed immediatelybefore the FID. The restrictor serves to maintain the required pressure in the column, while allowing the pump and detector toperform as specified in 8.2.6.1.3 Sample Inlet SystemA liquid-sample injection valve is required that is capable of introdu
27、cing a sub-microliter volumewith a precision better than 0.5%.0.5 %. A 0.2000.200 L to 0.060-L0.060 L injection volume was found to be adequate incombination with 1-mm1 mm diameter columns. The sample inlet system shall be installed and operated in a manner such that thechromatographic separation is
28、 not negatively affected.6.1.4 ColumnsThree columns of equal inside diameter are required:6.1.4.1 A high surface area silica column, capable of separating alkanes and olefins from aromatics as specified in Section 8.Typically, a 50-cm50 cm long, 1-mm1 mm internal diameter, or a 25-cm, 4.6-mm25 cm, 4
29、.6 mm internal diameter column is used.This column is packed with particles having an average diameter of 5-m5 m or less, 600-nm (60-)600 nm (60 ) pores, anda surface area of 350-m350 m2/g.NOTE 2Columns suitable for Test Method D5186 and D6550 are also suitable for this test method. Sources and typi
30、cal dimensions are shown in Table1.6.1.4.2 Asilver-loaded silica or cation exchange column capable of separating olefins from alkanes. Typically, a 5-cm5 cm longby 1-mm1 mm internal diameter column packed with particles having an average diameter of 5-m5 m is used for the analysis.NOTE 3Silver-loade
31、d silica columns suitable for Test Method D6550 are also suitable for the present method. Sources and typical dimensions areshown in Table 1.6.1.4.3 Apolyvinylalcohol polyvinyl alcohol (PVA) column capable of separating alkanes, olefins, and aromatics from alcohol.Typically, a 5cm5 cm long by 1mm1 m
32、m or 4.6mm4.6 mm internal diameter column packed with PVAparticles is used for theanalysis.NOTE 4PVA columns that have been used successfully are shown in Table 1.D7347 1526.1.5 Column-Temperature ControlThe chromatograph shall be capable of controlling column temperature to within0.5C0.5 C or less.
33、6.1.5.1 Asecondary column heater mounted in the column chamber can be used to heat the silver-loaded column independentlyof the silica and PVA columns. This supplemental heating is recommended for faster clearance of the olefins and saturates fromthe silver-loaded column. The supplemental column hea
34、ter box is typically maintained at 150C.150 C.6.1.6 Computer or Electronic IntegratorMeans shall be provided for the determination of accumulated peak areas. This canbe done by means of a computer or electronic integrator. The computer or integrator shall have the capability of correcting forbaselin
35、e shifts during the run.6.1.7 Switching ValvesTwo six-way switching valves are configured in accordance with the scheme shown in Figs. 1-4. Fourdifferent positions are shown in these figures and are defined as follows:6.1.7.1 Position LC (Load Column)PVAcolumn (forward flush mode), silver column (fo
36、rward flush mode), and silica column(forward flush mode) connected in series. The flow enters the PVA column first, then the silica column second, and thesilver-loaded silica column third. This position is used to (1) inject the sample onto the columns and (2) retain the alcohol on thePVAcolumn whil
37、e allowing all other species to pass onto the silica column.After the alcohol is flushed from the system in PositionBE (back-flush ethanol) this position will again be used to (1) elute the saturates, (2) load the olefins onto the silver-loaded silicacolumn, and (3) retain the aromatics on the silic
38、a column (see Fig. 1).6.1.7.2 Position BE (Back-Flush Ethanol)PVAcolumn (back-flush mode).This position directs the flow from the PVAcolumnto the detector. The silica and silver-loaded silica columns are not in the flow path. The alcohol is eluted in this position (see Fig.2).6.1.7.3 Position BO (Ba
39、ck-Flush Olefins)The silica column is not in the flow path. The PVA (back-flush mode) and thesilver-loaded silica (back-flush mode) columns are connected in series. The olefinic species are eluted in this position (see Fig. 3).6.1.7.4 Position EA (Elute Aromatics)PVA column (forward flush mode), sil
40、ver column (forward flush mode), and silicacolumn (forward flush mode) connected in series. The flow enters the PVA column first, then the silver-loaded silica columnsecond, and the silica column third. This position differs from position LC in that the silica column is the last column in the series
41、.The aromatics are eluted to the detector in the forward flow mode (see Fig. 4).7. Reagents and Materials7.1 AirZero-grade (hydrocarbon-free) air is used as the FID oxidant. (WarningAir is usually supplied as a compressed gasunder high pressure, and it supports combustion. )7.2 Calibration SolutionA
42、n ethanolic mixture containing olefins of a known percent by mass % of the type found in typicaldenatured alcohol. An example of this mixture would be 99.50%99.50 % ethanol, 99.995%99.995 % purity and 0.50%0.50 %olefin solution containing 2-pentene, 1-hexene and cyclohexene.7.3 Carbon Dioxide (CO2)S
43、upercritical fluid chromatographic grade, 99.995%99.995 % minimum purity, supplied pressur-ized in a cylinder with a dip tube for removal of liquid through a CGA 320 fitting. (WarningLiquid at high pressure. Releaseof pressure results in production of extremely cold, solid CO2 and gas, which can dil
44、ute available atmospheric oxygen.)7.4 HydrogenHydrogen of high quality (hydrocarbon free) is used as the fuel for the FID. (Warning Hydrogen is usuallysupplied under high pressure and is extremely flammable. )7.5 Loading-Time MixturesFour loading time mixtures are recommended to determine the switch
45、ing times for this test methodand to protect the silica column from exposure to ethanol and the silver-loaded column from contamination by aromatics andethanol.7.5.1 Loading-Time Mixture AAmixture of 10 % alkanes (n-hexane and cyclohexane), 10 % aromatics (benzene, toluene, andnaphthalene), and 80 %
46、 ethanol can be used to determine the loading time of saturates, olefins, and aromatics onto the silica columnwhile protecting the silica and silver-loaded column from ethanol contamination.TABLE 1 Typical ColumnsColumn Type: PVA Silica Silver-loaded silicaVendor: Selerity,WatersCorporationSelerity,
47、 Merck Selerity,Hypersil,PhenomenexPacking material: PVA High surfacearea silicaparticlesCation exchangeParticle size, m: 5 5 5Length, mm: 50 500, 250 50Internaldiameter,mm:1, 4.6 1, 4.6 1, 4.6D7347 1537.5.2 Loading-Time Mixture BA mixture of 10 % alkanes (n-hexane and cyclohexane), 7 % aromatics (b
48、enzene, toluene, andnaphthalene), 3 % olefins (2-pentene, 1 hexene, and cyclohexene) and 80 % ethanol can be used to determine the loading time ofsaturates and olefins onto the silver-loaded column and protect it from aromatic contamination.7.5.3 Loading-Time Mixture CA mixture of 7 % alkanes (n-hex
49、ane and cyclohexane), 3 % olefins (2-pentene, 1 hexene,1-hexene, and cyclohexene), and 90 % ethanol can be used to establish the elution time of the olefins from the silver-loaded columnto the detector in the back-flush mode.7.5.4 Loading-Time Mixture DAmixture of 10 % alkanes (n-hexane and cyclohexane) and 90 % ethanol can be used to checkthe absence of saturates on the silver-loaded column during the elution of olefins.7.5.5 Loading-Time Mixture EAmixture of 10 % aromatics (benzene, toluene, and naphthalene) and 90 %
