1、Designation: D2712 18D2712 18aStandard Test Method forDetermination of Hydrocarbon Impurities in High PurityPropylene by Gas Chromatography1This standard is issued under the fixed designation D2712; the number immediately following the designation indicates the year oforiginal adoption or, in the ca
2、se 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.NOTEPreviously balloted and approved material was included and the year date changed on January 19, 20
3、18.1. Scope*1.1 This test method is used for the determination of hydrocarbon impurities in propylene (propene) material of 97 % by massor greater purity (concentrates). These impurities are determined in the concentration range of 0.35 mgkg to 8575 mg/kg andincludes the following components: methan
4、e, ethane, ethylene, propane, acetylene, isobutane, propadiene, normal butane,trans-2-butene, butene-1, isobutylene, cis-2-butene, isopentane, methylacetylene, normal pentane, and 1,3-butadiene.NOTE 1Optionally, the analysis may include the determination of pentenes/hexanes and heavier components, s
5、ee 6.3.1.2 This test method does not determine non-hydrocarbon impurities, and additional tests may be necessary to fully characterizethe propylene sample. However, for the purposes of this test, the purity of propylene is determined as the difference between thetotal of the determined analytes and
6、100 % (by difference).1.3 When this test method is being used for the determination of trace level impurities in high-purity propylene, the use of thistest method for the analysis of propylene samples at lower purities is not recommended due to the potential for cross contaminationbetween samples.1.
7、4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.5 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address allof the safety concerns, if any, associated with its u
8、se. It is the responsibility of the user of this standard to establish appropriatesafety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accordance with internationally recognized principles
9、on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1265 Practice for Sampling Liquefied Pe
10、troleum (LP) Gases, Manual MethodD3700 Practice for Obtaining LPG Samples Using a Floating Piston CylinderF307 Practice for Sampling Pressurized Gas for Gas Analysis3. Terminology3.1 Definitions:3.1.1 liquefied petroleum gas (LPG)hydrocarbon gases that can be stored or handled in the liquid phase un
11、der moderateconditions of pressure and at ambient temperature; they consist essentially of C3 and C4 alkanes and alkenes, or mixtures of these,and contain generally less than 0.5 % by liquid volume of material of higher carbon number, and have a vapor pressure notexceeding 2000 kPa at 40 C.3.1.2 pro
12、pylene concentratematerial-containing propylene at or above concentrations of 97 % by mass.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.D0.03 on Propylene.Current edition appr
13、oved Jan. 19, 2018June 1, 2018. Published January 2018July 2018. Originally approved in 1968. Last previous edition approved in 20172018 as D2712 1718.1. DOI: 10.1520/D2712-18.10.1520/D2712-18A.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at se
14、rviceastm.org. For Annual Book of ASTM Standardsvolume information, 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
15、. Becauseit may not be technically possible to adequately depict all 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
16、 appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Summary of Test Method4.1 An LPG phase sample is analyzed as received via either gas or liquid sampling valves into a gas chromatograph. The gaschr
17、omatograph is provided with a liquid sampling valve and optionally with a 6-port gas sampling valve and/or a 6-port switchingvalve. If the user chooses to use a 6-port switching valve to provide an initial composite backflush of C5 olefins and C6+components, a small length of pre-column should be us
18、ed to provide separation of the components of interest, as listed in 1.1, andthe heavier components. This pre-column will separate the heaviest components from the remainder of the sample. A pre-columnwhich also retains water and oxygenated hydrocarbons is recommended. A flame ionization detector (F
19、ID) is used for componentdetection. However, other detectors may be used provided that they can provide the same sensitivity and selectivity for thecomponents of interest.4.2 The integrated detector signal (peak areas) is corrected for detector response by comparing sample peak areas for eachcompoun
20、d of interest relative to peak areas obtained for each compound of interest from a standard mixture of known componentconcentrations. This method of calibration shall be referred to hereafter as “external standard calibration.”5. Significance and Use5.1 High-purity propylene is required as a feedsto
21、ck for various manufacturing processes, and the presence of trace amountsof certain hydrocarbon impurities may have adverse effects on yield or catalyst life. This test method is suitable for use as abenchmark in setting commercial specifications, for use as an internal quality control tool, and for
22、 use in development or researchwork.6. Apparatus6.1 Gas Chromatograph (GC)Any gas chromatographic instrument that is capable of providing a linear temperatureprogrammed zone for the capillary column(s). The programming rate must be sufficiently repeatable to obtain a retention timerepeatability of 0
23、.05 min (3 s) throughout the scope of this analysis.6.2 DetectorAny detector providing a sensitivity of 0.5 mgkg or less for the compounds listed in 1.1 may be used. The useof a flame ionization detector (FID) is strongly recommended. However, other detectors may be used provided that they canprovid
24、e the same sensitivity and selectivity for the components of interest without interference from the propylene major peak ornon-hydrocarbon components, which might be present in the samples. As an example, the use of a mass spectroscopic detector(MSD), a discharge ionization detector (DID), or helium
25、 ionization detector (HID) might be possible so long as appropriate valvingis supplied and/or appropriate testing is performed to ensure that non-hydrocarbon components will not interfere. All calculationsin this test method are based on the use of a flame ionization detector (FID).6.3 Column(s)The
26、recommended analytical column is a 50 m by 0.53 mm I.D. KCl deactivatedAl2O3 PLOTcolumn. Relativeretention order is dependent upon the deactivation method of the column. Users are cautioned to specifically test the column usinga test mix to ensure that propadiene, methyl acetylene, and butadiene are
27、 not being adsorbed by the column. This condition canexist depending upon the degree of column deactivation. Other types of columns may be used so long as they provide sufficientseparation and no absorption of propadiene, methyl acetylene, or butadiene occurs.6.4 InletThe gas chromatograph must incl
28、ude a splitter inlet, which may be operated isothermally at user-settabletemperatures up to the maximum column temperature employed. Split flows in the range of 5:1 to 8:1 might be employed; a typicalvalue for the split ratio is 5:1 using a 0.2 L liquid sampling valve injection (to allow the lower d
29、etection limits described to beobtained). The splitter inlet is used in conjunction with gas or liquid sampling valves, as described below.6.4.1 The user may wish to incorporate the use of a 6-port switching valve and pre-column(s) to provide an initial C5 olefin/C6+composite backflush. Any pre-colu
30、mns which provide separation between the components of interest and the composite heaviercomponents may be used. A 10 m to 15 m section of 0.53 mm I.D. by 3 micro polydimethylpolysiloxane is recommended. Thelength of a pre-column will be dependent upon the film thickness, phase, and/or column activi
31、ty. This pre-column separates theheaviest components away from the remainder of the sample.6.5 Sample Introduction:6.5.1 Liquid SamplingLiquid samples shall be injected by means of a liquid sampling valve with an internal fixed sample loopwhich will provide the minimum detection limits as specified
32、in 1.1. A sample loop size of 0.2 L has been found to be sufficient.The liquid sample being introduced must be pressurized at least 1380 kPa above the vapor pressure of the sample at the valvetemperature at all times (use of a constant pressure source is suggested, if possible). It is important that
33、 this pressure be duplicatedto ensure repeatability. A shut-off valve or back-pressure regulator should be located at the waste exit of the liquid sampling valveso that sample pressure to the valve may be maintained.6.5.1.1 Figs. 1 and 2A frit type filter should be placed in the sample line in front
34、 of the liquid sampling valve so thatparticulates that might be present in samples will not score the valve rotor. A frit size of 2 m to 7 m is suggested. It is veryimportant that the filter has a low-pressure drop. A high-pressure drop across a filter will cause the sample to boil across the filter
35、,causing non-repeatable results. The liquid sample valve shall be mounted exterior to any heated compartment and shall be ableto operate at ambient temperature. The use of floating piston sample cylinders is encouraged to minimize or eliminate theD2712 18a2volatilization of lighter components into t
36、he headspace. The fixed sample volume injection should be repeatable such thatsuccessive runs agree within 2 % relative on each component area and all components are within the linearity of the detector. (2 %relative on each component is not achieved in the precision data set of this test method for
37、 ethylene 5 % and acetylene 3.5 %)6.5.2 Vapor Sampling (optional)A six-port gas sampling valve with 1.5875 mm (116 in.) fittings and a 200 L fixed samplingloop may be used to sample propene concentrates in the vapor phase. If a gas-sampling valve is used, the use of a 2 m to 7 mfilter is advised to
38、prevent scoring the valve rotor. The filter may be a frit or packed screen type. The gas-sampling valve must behoused in a thermostatically controlled compartment. Special care must be taken to vaporize liquid phase sample rather thansampling the headspace of the liquid. The sample valve should be r
39、epeatable such that successive runs agree within 2 % relativeon each component and all components are within the linearity of the detector.6.5.2.1 An in-line, heated vaporizing device, which is heat-traced to the gas-sampling valve, may be used. The device shouldconsist of a volume of tubing of appr
40、oximately 10 mL, which is encased in a heated block (the block should be a high-mass blockheated to approximately 80 C). The outlet of the tubing should be heat-traced and connected to the gas-sampling valve. Othertypes of commercially available vaporizers may be used.6.5.3 Series/Reversal Switching
41、 (optional)A six-port switching valve with 1.5875 mm (116 in.) fittings may be used incombination with the analytical column and pre-column. A typical arrangement of the valves is shown in Fig. 1 and Fig. 2, or inFig. 3 and Fig. 4 if the gas sampling valve is used. To avoid scoring the valve rotor,
42、it is suggested that the connections to theanalytical column and pre-column be made using 1.5875 mm tubing from the valves through zero-volume unions to the capillaries.Plumbing techniques must be used which avoid dead-volumes and cold spots. The timing of the valve switch must be empiricallydetermi
43、ned using a sample mixture, which contains 1,3-butadiene, n-pentane, and n-hexane. It will be necessary to maximize thearea counts of 1,3-butadiene and n-pentane while not allowing n-hexane to elute from the analytical column. The timing willdepend upon the length of pre-column that is used, the pha
44、se and film thickness of that column, and/or the activity of that column.6.6 Data AcquisitionAny integrator or computerized data acquisition system may be used for peak area integration and forgraphic presentation of the chromatogram.FIG. 1 Arrangement of ValvesFIG. 2 Arrangement of ValvesD2712 18a3
45、7. Reagents and Materials7.1 Calibration Standard MixtureA liquid sample containing levels of 2 mgkg to 20 mgkg of each of the trace components(all components except propane at 3000 mg/kg to 5000 mg/kg and propene balance) listed in Table 1 should be used as the externalstandard by which the instrum
46、ent will be calibrated. It is strongly recommended that the calibration standard mixture be containedin a floating piston cylinder and pressurized at least 1380 kPa above the vapor pressure of the mixture at all times (a constantFIG. 3 Arrangement of Valves (Gas Sampling Valve Included)FIG. 4 Arrang
47、ement of Valves (Gas Sampling Valve Included)TABLE 1 Typical Compounds and Retention Times for CommonHydrocarbon Impurities in PropyleneComponents Retention Time (minutes)C5=/C6+ composite backflush 2.2Methane 3.9Ethane 4.6Ethylene 5.4Propane 7.2Propylene 8.8Acetylene 10.8Isobutane 11.2Propadiene 11
48、.4Normal Butane 11.6Trans-2-Butene 13.9Butene-1 14.1Isobutylene 14.5Cis-2-Butene 14.9Isopentane 16.2Methylacetylene 16.4Normal Pentane 16.71,3-Butadiene 17.33-Methyl-1-Butene 18.3D2712 18a4pressure source is suggested). The calibration standard mixture should be gravimetrically prepared, supplied wi
49、th both gravimetricconcentrations and with the volumetrically converted concentrations, and certified.7.2 Helium, chromatography grade, gas having a purity of 99.99 % volume or better.7.3 Hydrogen, chromatography grade, gas certified as having less than 1 mgkg hydrocarbon impurities for FID fuel gas.7.4 Air, chromatography grade, gas certified as having less than 10 mgkg hydrocarbon impurities for FID fuel gas.7.5 Air, compressed, moisture and particulate free, used for pneumatic valve actuation.8. Sampling8.1 It is strongly recommended that sam
