1、Designation: D2712 18Standard 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 case of rev
2、ision, 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, 2018.1. Sco
3、pe*1.1 This test method is used for the determination ofhydrocarbon impurities in propylene (propene) material of97 % by mass or greater purity (concentrates). These impuritiesare determined in the concentration range of 0.35 mg kg to8575 mg/kg and includes the following components: methane,ethane,
4、ethylene, propane, acetylene, isobutane, propadiene,normal butane, trans-2-butene, butene-1, isobutylene, cis-2-butene, isopentane, methylacetylene, normal pentane, and1,3-butadiene.NOTE 1Optionally, the analysis may include the determination ofpentenes/hexanes and heavier components, see 6.3.1.2 Th
5、is test method does not determine non-hydrocarbonimpurities, and additional tests may be necessary to fullycharacterize the propylene sample. However, for the purposesof this test, the purity of propylene is determined as thedifference between the total of the determined analytes and100 % (by differ
6、ence).1.3 When this test method is being used for the determina-tion of trace level impurities in high-purity propylene, the useof this test method for the analysis of propylene samples atlower purities is not recommended due to the potential forcross contamination between samples.1.4 The values sta
7、ted in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This standard may involve hazardous materials,operations, and equipment. This standard does not purport toaddress all of the safety concerns, if any, associated with itsuse. It is the respon
8、sibility of the user of this standard toestablish appropriate safety, health, and environmental prac-tices and determine the applicability of regulatory limitationsprior to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization
9、 established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1265 Practice for Sampling Liquefied Petroleum (LP)Gases
10、, Manual MethodD3700 Practice for Obtaining LPG Samples Using a Float-ing Piston CylinderF307 Practice for Sampling Pressurized Gas for Gas Analy-sis3. Terminology3.1 Definitions:3.1.1 liquefied petroleum gas (LPG)hydrocarbon gasesthat can be stored or handled in the liquid phase undermoderate condi
11、tions of pressure and at ambient temperature;they consist essentially of C3and C4alkanes and alkenes, ormixtures of these, and contain generally less than 0.5 % byliquid volume of material of higher carbon number, and have avapor pressure not exceeding 2000 kPa at 40 C.3.1.2 propylene concentratemat
12、erial-containing propyl-ene at or above concentrations of 97 % by mass.4. Summary of Test Method4.1 An LPG phase sample is analyzed as received via eithergas or liquid sampling valves into a gas chromatograph. Thegas chromatograph is provided with a liquid sampling valveand optionally with a 6-port
13、gas sampling valve and/or a 6-portswitching valve. If the user chooses to use a 6-port switchingvalve to provide an initial composite backflush of C5olefinsand C6+ components, a small length of pre-column should be1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products
14、, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.D0.03 on Propylene.Current edition approved Jan. 19, 2018. Published January 2018. Originallyapproved in 1968. Last previous edition approved in 2017 as D2712 171. DOI:10.1520/D2712-18.2For referenced ASTM standards,
15、visit the ASTM website, www.astm.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.*A Summary of Changes section appears at the end of this standardCopyright ASTM International
16、, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides a
17、nd Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1used to provide separation of the components of interest, aslisted in 1.1, and the heavier components. This pre-column willseparate the heaviest components from the remainder of thesample.Apre-colu
18、mn which also retains water and oxygenatedhydrocarbons is recommended. A flame ionization detector(FID) is used for component detection. However, other detec-tors may be used provided that they can provide the samesensitivity and selectivity for the components of interest.4.2 The integrated detector
19、 signal (peak areas) is correctedfor detector response by comparing sample peak areas for eachcompound of interest relative to peak areas obtained for eachcompound of interest from a standard mixture of knowncomponent concentrations. This method of calibration shall bereferred to hereafter as “exter
20、nal standard calibration.”5. Significance and Use5.1 High-purity propylene is required as a feedstock forvarious manufacturing processes, and the presence of traceamounts of certain hydrocarbon impurities may have adverseeffects on yield or catalyst life. This test method is suitable foruse as a ben
21、chmark in setting commercial specifications, foruse as an internal quality control tool, and for use in develop-ment or research work.6. Apparatus6.1 Gas Chromatograph (GC)Any gas chromatographicinstrument that is capable of providing a linear temperatureprogrammed zone for the capillary column(s).
22、The program-ming rate must be sufficiently repeatable to obtain a retentiontime repeatability of 0.05 min (3 s) throughout the scope of thisanalysis.6.2 DetectorAny detector providing a sensitivity of0.5 mg kg or less for the compounds listed in 1.1 may be used.The use of a flame ionization detector
23、 (FID) is stronglyrecommended. However, other detectors may be used providedthat they can provide the same sensitivity and selectivity for thecomponents of interest without interference from the propylenemajor peak or non-hydrocarbon components, which might bepresent in the samples. As an example, t
24、he use of a massspectroscopic detector (MSD), a discharge ionization detector(DID), or helium ionization detector (HID) might be possibleso long as appropriate valving is supplied and/or appropriatetesting is performed to ensure that non-hydrocarbon compo-nents will not interfere. All calculations i
25、n this test method arebased on the use of a flame ionization detector (FID).6.3 Column(s)The recommended analytical column is a50 m by 0.53 mm I.D. KCl deactivated Al2O3PLOT column.Relative retention order is dependent upon the deactivationmethod of the column. Users are cautioned to specifically te
26、stthe column using a test mix to ensure that propadiene, methylacetylene, and butadiene are not being adsorbed by the column.This condition can exist depending upon the degree of columndeactivation. Other types of columns may be used so long asthey provide sufficient separation and no absorption ofp
27、ropadiene, methyl acetylene, or butadiene occurs.6.4 InletThe gas chromatograph must include a splitterinlet, which may be operated isothermally at user-settabletemperatures up to the maximum column temperature em-ployed. Split flows in the range of 5:1 to 8:1 might beemployed; a typical value for t
28、he split ratio is 5:1 using a0.2 L liquid sampling valve injection (to allow the lowerdetection limits described to be obtained). The splitter inlet isused in conjunction with gas or liquid sampling valves, asdescribed below.6.4.1 The user may wish to incorporate the use of a 6-portswitching valve a
29、nd pre-column(s) to provide an initial C5olefin/C6+ composite backflush. Any pre-columns which pro-vide separation between the components of interest and thecomposite heavier components may be used. A 10 m to 15 msection of 0.53 mm I.D. by 3 micro polydimethylpolysiloxaneis recommended. The length o
30、f a pre-column will be dependentupon the film thickness, phase, and/or column activity. Thispre-column separates the heaviest components away from theremainder of the sample.6.5 Sample Introduction:6.5.1 Liquid SamplingLiquid samples shall be injected bymeans of a liquid sampling valve with an inter
31、nal fixed sampleloop which will provide the minimum detection limits asspecified in 1.1. A sample loop size of 0.2 L has been foundto be sufficient. The liquid sample being introduced must bepressurized at least 1380 kPa above the vapor pressure of thesample at the valve temperature at all times (us
32、e of a constantpressure source is suggested, if possible). It is important thatthis pressure be duplicated to ensure repeatability. A shut-offvalve or back-pressure regulator should be located at the wasteexit of the liquid sampling valve so that sample pressure to thevalve may be maintained.6.5.1.1
33、 Figs. 1 and 2A frit type filter should be placed inthe sample line in front of the liquid sampling valve so thatparticulates that might be present in samples will not score thevalve 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-pr
34、essure drop across a filter will cause the sample to boil acrossthe filter, causing non-repeatable results. The liquid samplevalve shall be mounted exterior to any heated compartment andshall be able to operate at ambient temperature. The use offloating piston sample cylinders is encouraged to minim
35、ize oreliminate the volatilization of lighter components into theheadspace. The fixed sample volume injection should berepeatable such that successive runs agree within 2 % relativeon each component area and all components are within thelinearity of the detector. (2 % relative on each component is n
36、otachieved in the precision data set of this test method forethylene 5 % and acetylene 3.5 %)6.5.2 Vapor Sampling (optional)A six-port gas samplingvalve with 1.5875 mm (116 in.) fittings and a 200 L fixedsampling loop may be used to sample propene concentrates inthe vapor phase. If a gas-sampling va
37、lve is used, the use of a2 m to 7 m filter is advised to prevent scoring the valve rotor.The filter may be a frit or packed screen type. The gas-sampling valve must be housed in a thermostatically controlledcompartment. Special care must be taken to vaporize liquidphase sample rather than sampling t
38、he headspace of the liquid.The sample valve should be repeatable such that successiveD2712 182runs agree within 2 % relative on each component and allcomponents 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
39、be used. The deviceshould consist of a volume of tubing of approximately 10 mL,which is encased in a heated block (the block should be ahigh-mass block heated to approximately 80 C). The outlet ofthe tubing should be heat-traced and connected to the gas-sampling valve. Other types of commercially av
40、ailable vapor-izers may be used.6.5.3 Series/Reversal Switching (optional)A six-portswitching valve with 1.5875 mm (116 in.) fittings may be usedin combination with the analytical column and pre-column. Atypical arrangement of the valves is shown in Fig. 1 and Fig. 2,or in Fig. 3 and Fig. 4 if the g
41、as sampling valve is used. Toavoid scoring the valve rotor, it is suggested that the connec-tions to the analytical column and pre-column be made using1.5875 mm tubing from the valves through zero-volume unionsto the capillaries. Plumbing techniques must be used whichavoid dead-volumes and cold spot
42、s. The timing of the valveswitch must be empirically determined using a sample mixture,which contains 1,3-butadiene, n-pentane, and n-hexane. It willbe necessary to maximize the area counts of 1,3-butadiene andn-pentane while not allowing n-hexane to elute from theanalytical column. The timing will
43、depend upon the length ofpre-column that is used, the phase and film thickness of thatcolumn, and/or the activity of that column.6.6 Data AcquisitionAny integrator or computerized dataacquisition system may be used for peak area integration andfor graphic presentation of the chromatogram.7. Reagents
44、 and Materials7.1 Calibration Standard MixtureA liquid sample con-taining levels of 2 mg kg to 20 mg kg of each of the tracecomponents (all components except propane at 3000 mg/kg to5000 mg/kg and propene balance) listed in Table 1 should beused as the external standard by which the instrument will
45、becalibrated. It is strongly recommended that the calibrationstandard mixture be contained in a floating piston cylinder andpressurized at least 1380 kPa above the vapor pressure of themixture at all times (a constant pressure source is suggested).The calibration standard mixture should be gravimetr
46、icallyprepared, supplied with both gravimetric concentrations andwith the volumetrically converted concentrations, and certified.7.2 Helium, chromatography grade, gas having a purity of99.99 % volume or better.7.3 Hydrogen, chromatography grade, gas certified as hav-ing less than 1 mg kg hydrocarbon
47、 impurities for FID fuel gas.FIG. 1 Arrangement of ValvesFIG. 2 Arrangement of ValvesD2712 1837.4 Air, chromatography grade, gas certified as having lessthan 10 mg kg hydrocarbon impurities for FID fuel gas.7.5 Air, compressed, moisture and particulate free, used forpneumatic valve actuation.8. Samp
48、ling8.1 It is strongly recommended that samples be collected infloating piston sample cylinders (see Practices D1265, D3700,and F307). Capture of samples in a floating piston cylinderreduces or eliminates the formation of headspace in the sample,maintaining the sample as a single phase (liquid), and
49、 helpingto ensure more accurate analysis data.8.2 If an open cylinder must be used for sampling, be sureto pressurize the cylinder with an inert gas to a pressure of atleast 1380 kPa above the vapor pressure of the sample atambient temperature.8.3 In either case above, the cylinders should be equippedwith a spring-loaded relief valve or a burst-disc that will openat pressures between 6900 kPa to 8300 kPa. These valves helpto prevent the dangerous escalation of pressure above the safeoperating limit of the cylinder should the sample expandhydrostatic
