1、Designation: D7796 12 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. Scope1.1 This test method covers the determination of the purityof ethyl tert-butyl ether (ETBE) by g
3、as 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 180C 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, are
6、also provided to improve clarity and aid theuser of this test methods.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 and health practices and determine the
7、 applica-bility of regulatory limitations prior to use.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 Preparation of Liquid Blends for Use asA
8、nalytical 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 Tertiary-Butyl Ether (ETBE)for Blending wit
9、h 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 to manycommon gas chromatographic proce
10、dures, 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 trimers offeed such as trimethylpentene or pen
11、tamethylheptene.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 aliquot through the columnwhere the component
12、s are separated by the chromatographicprocess. Components are sensed by a flame ionization detectoras they elute from the column.4.2 The detector signal is processed by an electronic dataacquisition system or integrating computer. Each eluting com-ponent is identified by comparing its retention time
13、 to thoseestablished by analyzing standards under identical conditions.4.3 The concentration of each component in mass percent isdetermined by normalization of the peak areas after each peakarea has been corrected by a detector response multiplicationfactor and the water content of the sample. The d
14、etector1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.J0.02 on Aviation Gasoline.Current edition approved May 15, 2012. Published November 2012. DOI:10.1520/D779612.2For referenced ASTM standar
15、ds, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1response factors are determined by analyzing prepared stan-dards with the concentrations simi
16、lar to those encountered inthe sample.5. Significance and Use5.1 The presence 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 ETBEprod
17、uct. This is useful in the evaluation of process operationscontrol, in the 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 ty
18、picallypresent at very low concentrations in ETBE.7. Apparatus7.1 Gas ChromatographInstrumentation 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-duct
19、ion. Carrier gas controls shall be of adequate precision toprovide reproducible 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
20、, apressure of approximately 550 kPa (80 psig) is required). Ahydrogen flame 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 splitti
21、ng injector is employed.Devices capable of 0.1 to 0.5 L injections are 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
22、peaks are skewed,variation in retention times. Watch for any skewed peaks 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
23、tubular column with non-polar methyl sili-cone bonded (cross-linked) phase 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 res
24、olution between trans-2-pentene andtert-butanol, and between cis-2-pentene 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
25、 of theseanalyses shall meet or exceed these minimum requirements:7.4.1 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
26、Sampling rate for fast (tA.12. Calibration and Standardization12.1 Identify 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 li
27、sted in Table 2. Analyze mixtures containingthese compounds to verify their retention times. Mixtures usedfor determining retention times may be blended from pureD7796 123compounds or purchased. Retention times of other suspectedcontaminants may be established by analyzing mixtures con-taining these
28、 materials under identical conditions. A typicalchromatogram of an ETBE product 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.
29、These response factors shall be verified by analyzinga prepared standard with concentrations 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 f
30、actors should be experimentallydetermined in accordance with Practice D4626 by measuringthe 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 o
31、r to a temperature determined to besuitable by the evaluation in Section 11.13.2 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 temperatu
32、re to theinitial method temperature.13.3 Set the recorder or integration device, 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 to 0.5 L of sample into the injection
33、portand start the analysis. Sample size shall follow guidelinesdiscussed in 7.2. 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 us
34、ed, examine the report toensure that peaks are properly identified and integrated. 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 quantificati
35、on.14.2 Obtain the integrated areas of each impurity peak.Multiply each area by 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 asdete
36、rmined by Test Method D6304, or equivalent.14.4 Calculate the mass % of each impurity 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 co
37、ntent)(4)14.6 Report the results to two decimal places.15. Precision and Bias15.1 An estimate of the repeatability of this test method wasobtained by conducting twelve replicate tests on each of twosamples of ETBE in a single laboratory. Table 3 contains theresulting repeatability estimates for ETBE
38、 purity and for theimpurities listed in the detailed requirements for ETBE (Table1) of Specification D7618.15.2 An interlaboratory study program to determine theprecision and bias of this test method will be completed byMarch 2017.16. Keywords16.1 ETBE; ethyl tert-butyl ether; open tubular column ga
39、schromatographyTABLE 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 trans-2-Butene 0.612 1.176 cis-2-
40、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 0.725 1.1418 2-Methyl-2-butene
41、 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 ether 1.19 1.3329 Butyl ethyl eth
42、er 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 124NOTE 1Numbers correspond to components in Table 2.FIG. 1 Typical Chromatogram of an ETBE Sample A
43、nalyzed on a 100 Meter ColumnD7796 125ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the r
44、iskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of t
45、his standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmak
46、e your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained b
47、y contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).TABLE 3 Repeatability Estimate
48、s for Selected Impurities and ETBE PuritySample 1 Sample 2Average Std Dev r Average Std Dev rEthanol 0.16 0.0015 0.0043 0.08 0.0009 0.0025Methanol 0.01 0.0003 0.0010 0.01 0.0001 0.0003tert-Butyl alcohol 1.60 0.0097 0.0268 0.33 0.0032 0.0088Methyl tert-butyl ether 0.74 0.0040 0.0112 0.01 0.001 0.0002
49、C2C4 Oxygenates, excluding alcoholsAcetone 0.31 0.0020 0.0054 none detectedMethyl ethyl ketone 0.11 0.0008 0.0024 none detectedDimethyl ether none detected none detectedDiethyl ether 0.01 0.0015 0.0040 0.002 0.0001 0.0002C4C6 Hydrocarbonsiso-Butylene 0.04 0.0006 0.0016 0.03 0.0002 0.0005iso-Pentane 0.15 0.0006 0.0018 0.03 0.0003 0.0007Pentane 0.16 0.0011 0.0032 0.02 0.0002 0.00005Hexane 0.09 0.0005 0.0013 0.04 0.0003 0.0009C6C8 Hydrocarbons2,2,4-Trimethyl pentane 0.02 0.0035 0.0098 0.06 0.0007 0.00182,4,4-Trimethyl-1-pentene 0.28 0.0019 0.0053 1.89 0.0202 0.05592,
