1、Designation: D7796 17 An American National StandardStandard Test Method forAnalysis of Ethyl tert-Butyl Ether (ETBE) by GasChromatography1This standard is issued under the fixed designation D7796; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、 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. Scope*1.1 This test method covers the determination of the purityof ethyl tert-butyl ether (ETBE) by
3、gas chromatography. It alsoprovides a procedure to measure impurities in ETBE such asC4to C12olefins, methyl, isopropyl and tert-butyl alcohols,methyl sec-butyl and methyl tert-amyl ethers, acetone, andmethyl ethyl ketone.1.2 This test method is not applicable to the determinationof ETBE in gasoline
4、.1.3 Water cannot be determined by this test method andshall be measured by a procedure such as Test Method D6304and the result used to normalize the chromatographic values.1.4 Most of the impurities in ETBE are resolved by the testmethod, however, some co-elution is encountered.1.5 This test method
5、 is inappropriate for impurities that boilat temperatures higher than 180 C or for impurities that causepoor or no response in a flame ionization detector, such aswater.1.6 The values stated in SI units of measurement arepreferred and used throughout the standard. Alternate units, incommon usage, ar
6、e also provided to improve clarity and aid theuser of this test method.1.7 This standard 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, health, and environmental practices
7、and deter-mine the applicability of regulatory limitations prior to use.1.8 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Reco
8、m-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D3700 Practice for Obtaining LPG Samples Using a Float-ing Piston CylinderD4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4307 Practice for
9、Preparation of Liquid Blends for Use asAnalytical StandardsD4626 Practice for Calculation of Gas ChromatographicResponse FactorsD6304 Test Method for Determination of Water in Petro-leum Products, Lubricating Oils, and Additives by Cou-lometric Karl Fischer TitrationD7618 Specification for Ethyl Ter
10、tiary-Butyl Ether (ETBE)for Blending with Aviation Spark-Ignition Engine FuelE355 Practice for Gas Chromatography Terms and Relation-shipsE594 Practice for Testing Flame Ionization Detectors Usedin Gas or Supercritical Fluid Chromatography3. Terminology3.1 DefinitionsThis test method makes reference
11、 to manycommon gas chromatographic procedures, terms, and relation-ships. Detailed definitions of these can be found in PracticesE355 and E594.3.2 Definitions of Terms Specific to This Standard:3.2.1 C4to C12olefins, ncommon olefin impurities inETBE including unreacted feedstock and dimers or trimer
12、s offeed such as trimethylpentene or pentamethylheptene.4. Summary of Test Method4.1 A representative aliquot of the ETBE product sample isintroduced into a gas chromatograph equipped with a methylsilicon bonded phase fused silica open tubular column. Heliumcarrier gas transports the vaporized aliqu
13、ot through the columnwhere the components are separated by the chromatographicprocess. Components are sensed by a flame ionization detectoras they elute from the column.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the dir
14、ect responsibility ofSubcommittee D02.04.0L on Gas Chromatography Methods.Current edition approved Oct. 1, 2017. Published November 2017. Originallyapproved in 2012. Last previous edition approved in 2012 as D7796 12. DOI:10.1520/D7796-17.2For referenced ASTM standards, visit the ASTM website, www.a
15、stm.org, orcontact ASTM Customer Service at serviceastm.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with i
16、nternationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.14.2 The detector signal is processed by an e
17、lectronic dataacquisition system or integrating computer. Each eluting com-ponent is identified by comparing its retention time to thoseestablished by analyzing standards under identical conditions.4.3 The concentration of each component in mass percent isdetermined by normalization of the peak area
18、s after each peakarea has been corrected by a detector response multiplicationfactor and the water content of the sample. The detectorresponse factors are determined by analyzing prepared stan-dards with the concentrations similar to those encountered inthe sample.5. Significance and Use5.1 The pres
19、ence of impurities in ETBE product can have adeleterious effect upon the value of ETBE as a fuel additive.Oxygenate and olefin contents are of primary concern. This testmethod provides a knowledge of the composition of ETBEproduct. This is useful in the evaluation of process operationscontrol, in th
20、e valuation of the product, and for regulatorypurposes.6. Interferences6.1 Cyclopentane and 2,3-dimethylbutane have been ob-served to co-elute with MTBE. However, these are not com-monly found impurities in MTBE, and MTBE is typicallypresent at very low concentrations in ETBE.7. Apparatus7.1 Gas Chr
21、omatographInstrumentation capable of oper-ating at the conditions listed in Table 1. A heated flashvaporizing injector designed to provide a linear sample splitinjection (that is, 200:1) is required for proper sample intro-duction. Carrier gas controls shall be of adequate precision toprovide reprod
22、ucible column flows and split ratios in order tomaintain analytical integrity. Pressure control devices andgages shall be designed to attain the linear velocity required inthe column used (for example, if a 150 m column is used, apressure of approximately 550 kPa (80 psig) is required). Ahydrogen fl
23、ame ionization detector with associated gas controlsand electronics, designed for optimum response with opentubular columns, is required.7.2 Sample IntroductionManual or automatic liquid sy-ringe sample injection to the splitting injector is employed.Devices capable of 0.1 L to 0.5 L injections are
24、suitable. Itshould be noted that inadequate splitter design, or poorinjection technique, or both, can result in poor resolution.Overloading of the column can also cause loss of resolution forsome components and, since overloaded peaks are skewed,variation in retention times. Watch for any skewed pea
25、ks thatindicate overloading during column evaluation. Observe thecomponent size and where possible, avoid conditions leadingto this problem during the analyses.7.3 Open Tubular Column3This test method utilizes afused silica open tubular column with non-polar methyl sili-cone bonded (cross-linked) ph
26、ase internal coating such as oneof the following:Column length 50 m 100 m 150 mFilm thickness 0.5 m 0.5 m 1.0 mInternal diameter 0.20 mm 0.25 mm 0.25 mmOther columns with equal or greater resolving power may beused. A minimum resolution between trans-2-pentene andtert-butanol, and between cis-2-pent
27、ene and tert-butanol of 1.3is required. The 150 m column is expected to decrease thelikelihood of co-elution of impurities.7.4 Electronic Data Acquisition SystemAny data acquisi-tion and integration device used for quantification of theseanalyses shall meet or exceed these minimum requirements:7.4.1
28、 Capacity for at least 50 peaks per analysis,7.4.2 Normalized area percent calculations with responsefactors,7.4.3 Identification of individual components based on re-tention time,7.4.4 Noise and spike rejection capability,7.4.5 Sampling rate for fast (tA.12. Calibration and Standardization12.1 Iden
29、tify component peaks from a sample analysis bymatching their retention time with the retention time ofreference compounds analyzed under identical conditions.Relative retention times for common contaminants in ETBEproducts are listed in Table 2. Analyze mixtures containingthese compounds to verify t
30、heir retention times. Mixtures usedfor determining retention times may be blended from purecompounds or purchased. Retention times of other suspectedcontaminants may be established by analyzing mixtures con-taining these materials under identical conditions. A typicalchromatogram of an ETBE product
31、sample, analyzed on the100 meter column that was used to acquire the repeatabilitydata reported below, is shown in Fig. 1. The peaks are indexedto Table 2.12.2 Typical mass relative response factors are found inTable 2. These response factors shall be verified by analyzinga prepared standard with co
32、ncentrations similar to thoseencountered in an ETBE product sample and comparing themeasured results with the prepared composition. If the mea-sured composition does not agree with the preparedcomposition, the response factors should be experimentallydetermined in accordance with Practice D4626 by m
33、easuringthe response factors of certified blends that have been pur-chased or blends prepared in accordance with Practice D4307.13. Procedure13.1 Set the instrument operating variables to the valuesspecified in Table 1 or to a temperature determined to besuitable by the evaluation in Section 11.13.2
34、 When the gas chromatograph has been inoperative formore than 24 h, raise the column temperature to the maximumtemperature used in the method and hold for 20 min to removecontaminants from the column. Lower the temperature to theinitial method temperature.13.3 Set the recorder or integration device,
35、 or both, foraccurate presentation of the data. Set instrumental sensitivitysuch that any component of at least 0.02 % mass will bedetected, integrated, and reported.13.4 Inject 0.1 L to 0.5 L of sample into the injection portand start the analysis. Sample size shall follow guidelinesdiscussed in 7.
36、2. Obtain a chromatogram and peak integrationreport.14. Calculation14.1 Identify each peak by matching retention times withknown reference standards or sample components as discussedin 12.1. If a computing integrator is used, examine the report toensure that peaks are properly identified and integra
37、ted. It isvery important that all oxygenate peaks be separated fromhydrocarbon peaks and correctly identified since oxygenateshave very different response factors than hydrocarbons andnormalization is used for quantification.14.2 Obtain the integrated areas of each impurity peak.Multiply each area b
38、y its appropriate response factor asdetermined in 12.2 to obtain peak areas corrected for responsedifferences. Use a response factor of 1.00 for unknownimpurities.14.3 Obtain the concentration of water in the sample asdetermined by Test Method D6304, or equivalent.14.4 Calculate the mass % of each i
39、mpurity using Eq 3:mass % impurity = (corrected peak area/total corrected peak area)3(100 2 mass % water) (3)14.5 Calculate the ETBE purity using Eq 4:ETBE purity, mass % 5 1002 (sum of all impurities from above + water content)(4)14.6 Report the results to two decimal places.15. Precision and Bias4
40、15.1 PrecisionThe precision of any individual measure-ment resulting from the application of this test method isexpected to be dependent upon several factors, including4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D02-1871. Co
41、ntactASTM CustomerService at serviceastm.org.TABLE 2 Relative Retention Times and Response Factors forETBE Impurities, 100 m ColumnNo. ComponentRelativeRetention Time(ETBE = 1)RelativeResponse(Hexane = 1)1 Dimethyl ether 0.577 3.532 Methanol 0.588 2.593 Isobutylene 0.600 1.234 Butane 0.606 1.015 tra
42、ns-2-Butene 0.612 1.176 cis-2-Butene 0.622 1.267 Ethanol 0.630 2.168 Acetone 0.664 2.059 iso-Pentane 0.670 1.0210 2-Propanol 0.675 1.9511 1-Pentene 0.68712 2-Methyl-1-butene 0.69513 Diethyl ether 0699 1.7914 n-Pentane 0.702 1.0115 trans-2-Pentene 0.712 1.1216 tert-Butanol 0.717 1.3417 cis-2-Pentene
43、0.725 1.1418 2-Methyl-2-butene 0.73319 Cyclopentene 0.76520 Methyl tert-butyl ether 0.824 1.4821 2,3-Dimethyl butane 0.83122 2-Methylpentane 0.839 1.0023 2-Butanone (methyl ethyl ketone) 0.855 1.5924 3-Mthylpentane 0.880 0.9225 n-Hexane 0.931 1.0027 Ethyl tert-butyl ether 1.0028 tert-Amyl methyl eth
44、er 1.19 1.3329 Butyl ethyl ether 1.25 1.4230 2,2,4-Trimethyl pentane (iso-octane)1.26 0.9731 2,4,4-Trimethyl-1-pentene 1.34 1.0632 2,4,4-Trimethyl-2-pentene 1.40 0.9333 Toluene 1.51 0.9634 2,3,4-Trimethyl-2-pentene 1.59 1.00D7796 174NOTE 1Numbers correspond to components in Table 2.FIG. 1 Typical Ch
45、romatogram of an ETBE Sample Analyzed on a 100 Meter ColumnD7796 175volatility of the component, its concentration, and the degree towhich it is resolved from other closely eluting components.Since it is not practical to determine the precision for measure-ment of every component separated by this m
46、ethod, Table 3lists repeatability and reproducibility for selected representa-tive components. With respect to reproducibility, only twocomponents met the statistical criteria of at least 30 degrees offreedom and details for the other components and precisionstudy are available elsewhere.415.1.1 Rep
47、eatabilityThe difference between successivetest results obtained by the same operator with the sameapparatus under constant operating conditions on identical testmaterials would, in the long run, in the normal and correctoperation of the method, exceed the values calculated from theequations listed
48、in Table 3 only in one case in 20.15.1.2 ReproducibilityThe difference between two singleand independent test results obtained by different operatorsworking in different laboratories on identical test materialswould, in the long run, in the normal and correct operation ofthe test method, exceed the
49、values calculated from the equa-tions listed in Table 3 only in one case in 20.16. Keywords16.1 ETBE; ethyl tert-butyl ether; open tubular column gaschromatographyD7796 176SUMMARY OF CHANGESSubcommittee D02.04 has identified the location of selected changes to this standard since the last issue(D7796 12) that may impact the use of this standard. (Approved Oct. 1, 2017.)(1) Revised subsection 15.1; added new subsections 15.1.1 and15.1.2.(2) Revised Table 3.ASTM International takes no position respecting the validity of any patent rights asserted in connection
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