1、Designation: D6748 02a (Reapproved 2012)Standard Test Method forDetermination of Potential Instability of Middle DistillateFuels Caused by the Presence of Phenalenes andPhenalenones (Rapid Method by PortableSpectrophotometer)1,2This standard is issued under the fixed designation D6748; the number im
2、mediately following the designation indicates the year oforiginal adoption or, in the 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. Scope1.1 Th
3、is test method covers a procedure3for the rapiddetermination of phenalenes and phenalenones in middledistillate fuels, including marine, automotive, heating, and gasturbine fuel such as those specified in Specifications D396,D975, D2069, and D2880. Phenalenes and phenalenones affectthe potential ins
4、tability of fuels, leading to fuel degradationproducts during storage, which may cause performance prob-lems.1.2 This test method is applicable to both dyed and undyedfuels at all points in the distribution chain from refinery toend-user. It is not applicable to fuels containing residual oil.The por
5、table apparatus allows the whole test to be conductedon site or in a laboratory and does not require the test sampleto be heated.1.3 This test method is suitable for testing samples with arelative absorbance of up to 5.00 absorbance units (AU).NOTE 1The precision of the test method has been establis
6、hed onrelative absorbance up to 1.00AU. For relative absorbance above 1.00AUthe precision may not apply.1.4 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
7、health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:4D396 Specification for Fuel OilsD975 Specification for Diesel Fuel OilsD2069 Specification for Marine Fuels (Withdrawn 2003)5D2880 Specification for Gas Turbine Fuel Oi
8、lsD4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD4306 Practice for Aviation Fuel Sample Containers forTests Affected by Trace ContaminationD4625 Test Method for Middle Distillate Fuel StorageStability at 4
9、3C (110F)D5854 Practice for Mixing and Handling of Liquid Samplesof Petroleum and Petroleum ProductsD6468 Test Method for High Temperature Stability ofMiddle Distillate FuelsE131 Terminology Relating to Molecular SpectroscopyE275 Practice for Describing and Measuring Performance ofUltraviolet and Vi
10、sible Spectrophotometers2.2 Other Standards:6Def Stan 05-50 Methods for Testing Fuels and Lubricantsand Associated Products, Part 40 Storage Stability ofDiesel FuelsDef Stan 914 Fuel, Naval, Distillate NATO Code: F76 JointService, Designation DIESO F763. Terminology3.1 Definitions:1This test method
11、is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.14 on Stability and Cleanliness of Liquid Fuels.Current edition approved Nov. 1, 2012. Published November 2012. Originallyapproved in 2002. Last previous edition ap
12、proved in 2007 as D674802a (2007).DOI: 10.1520/D6748-02AR12.2This test method is being jointly developed with the Institute of Petroleumwhere it is designated IP 463.3This process is covered by US Patent 5,378,632. Interested parties are invitedto submit information regarding the identification of a
13、n alternative(s) to thispatented item to ASTM International Headquarters. Your comments will receivecareful consideration at a meeting of the responsible technical committee, whichyou may attend.4For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at
14、serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.5The last approved version of this historical standard is referenced onwww.astm.org.6Available from United Kingdom Defence Standardization, Room 1138, Kenti-gern Hous
15、e, 65 Brown Street, Glasgow, G2 8EX. United Kingdom.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.1 For definitions of terms relating to absorption spec-troscopy see Terminology E131. Terms of particular signifi-cance are the fo
16、llowing:3.1.2 radiant energy, nenergy transmitted as electromag-netic waves.3.1.3 radiant power P, nthe rate at which energy istransported in a beam of radiant energy.3.2 Definitions of Terms Specific to This Standard:3.2.1 absorbance, A, nthe logarithm to the base 10 of thereciprocal of the transmi
17、ttance, T. In symbols:A 5 log101/T! 52log10T (1)where:T = transmittance as defined in 3.2.5.3.2.2 absorbance units (AU), nunits of relative absor-bance reported by the portable spectrophotometer.3.2.3 pathlength of test portion b, nthe distance in mm,measured in the direction of propagation of the b
18、eam of radiantenergy, between the surfaces of the portion on which theradiant energy is incident and the surface of the test portionfrom which it emerges.3.2.4 relative absorbance, nthe difference between theabsorbance (near infrared-visible band results) measured at thetwo wavelengths, and reported
19、 in AU.3.2.5 transmittance, T, nthe ratio of the radiant powertransmitted by the test portion in the test cuvette to the radiantpower transmitted by the Reagent 1 control in the cuvette.Expressed in the following equation.T 5 PT/PR1(2)where:PT= radiant power transmitted by the test portion, andPR1=
20、the radiant power transmitted by the Reagent 1control.4. Summary of Test Method4.1 A5 mLvolume of middle distillate fuel is mixed with anequal volume of an immiscible reagent solution. A secondreagent is then added, the new blend mixed and allowed tosettle for 30 min. for two phases to separate. The
21、 top reagentlayer (darker) is then placed in the portable spectrophotometerand the relative absorbance of near infrared and visible light, atfixed single wavelengths, is measured instantaneously andautomatically, and reported in AU.4.2 When mixed with the oil sample containing phenalenes,the oxidizi
22、ng Reagent 2 oxidizes the phenalenes to phenale-nones which are subsequently converted to colored indolylphe-nalene salts by the acidic Reagent 1. The spectrophotometermeasures the absorbance of light caused by the colored saltswhile eliminating the effect of the initial color of the fuel. Theabsorb
23、ance of light is a measure of the concentration of thecolored salts that are formed.5. Significance and Use5.1 Storage stability depends on complex interactions. Itvaries with feedstock type and source, and the processing used.The rate of degradation may not change uniformly withtemperature. Chemica
24、l reactions may lead to a change in colorfollowed by the formation of soluble gums and insolublesediments. Insoluble sediments may overload filters, and plugnozzles and injectors.5.2 This test method, which does not require the test sampleto be heated, uses a portable apparatus and allows tests to b
25、ecarried out on site or in the laboratory to give a result within 35min.5.3 The potential beneficial effects of stability additives infuels may not be recognized by this test method. Therefore, theactual storage stability of middle distillate fuels with stabilityadditives may not be correctly indica
26、ted by these test results.5.4 The unstable reactive compounds (phenalenes and phe-nalenones) detected by this test method may be present in fuelscontaining catalytically cracked or straight run materials andcan affect the potential instability of the fuel.5.5 If this test method is used by any party
27、 for a rapidassessment of stability, it is the responsibility of partiesconcerned to decide whether or not this procedure yieldsmeaningful results.5.6 Interpretation of results and correlation with other testmethods is given in Appendix X1.6. Apparatus76.1 Spectrophotometer, double beam, capable of
28、measuringabsorbance at one visible wavelength in the range 600-800 nmand one near infrared wavelength in the range 800-850 nm witha spectral bandwidth of 10 6 2 nm and an accuracy of 63nm(see Fig. 1). The display shall have a resolution of 0.01 of AU,and a repeatability of measurement of 60.02 AU fo
29、r ranges upto 1.00 AU. See Practice E275.NOTE 2The two wavelengths used are proprietary and are notadjustable.6.1.1 Zero Adjustment, a facility shall be incorporated toallow the absorbance measured at the two individual wave-lengths to be set to zero when using Reagent 1 as a control.6.1.2 Absorbanc
30、e Display, the relative absorbance, in AU,shall be the instantaneous difference between the absorbancemeasured at the two wavelengths. The peak wavelengthrepresents the absorption due to the colored indolylphenalenesalts which are formed, and the baseline wavelength is fornormalizing the result.6.2
31、Timer, capable of measuring 35 min to an accuracy of60.2 min.6.3 Dispenser, for Reagent 1 made of polyethylene,polypropylene, or glass and capable of dispensing 5 mL ofreagent with an accuracy of 60.5 mL.6.4 Syringe 1, for test portion, 5 mL, polyethylene,polypropylene, or glass, with an accuracy of
32、 60.25 mL.7The equipment, as listed in RR:D02-1522 was used to develop the precisionstatement. The apparatus described in Section 6 and the reagents listed in Section 7are both supplied by Stanhope-Seta, Chertsey, Surrey KT16 8AP, United Kingdom.To date, no other equipment has demonstrated throughAS
33、TM interlaboratory testingthe ability to meet the precision of this test. This is not an endorsement orcertification by ASTM International.D6748 02a (2012)26.5 Syringe 2, for Reagent 2, preset at 35 L, glass, with anaccuracy of 60.35 L.6.6 Test Tube with Stopper, nominally 15 mL, polyethylene,polypr
34、opylene, or glass.6.7 Pipette, 5 mL, polyethylene, polypropylene, or glass.6.8 Test Cuvette, 4.5 mL volume, optical methacrylate,disposable, with two opposite ribbed sides. Dimensions shallbe 45 mm high, 12.5 by 12.5 mm in width with a test portionpathlength 10 6 0.25 mm.7. Reagents and Materials7.1
35、 Reagent 1, proprietary, methanol solvent containing aLowry-Bronsted acid7(WarningAcidic, flammable, toxic,irritant).7.2 Reagent 2, proprietary solution containing potassiumpermanganate7an oxidizing agent (WarningOxidizingagent, toxic, irritant).7.3 Water, distilled or deionized, for flushing Syring
36、e 2 usedfor Reagent 2.8. Sampling8.1 Field SamplingTake field samples in accordance withPractices D4057, D4177, or other comparable sampling prac-tices. Record the sampling date. Sample bulk fuel above itscloud point and thoroughly mix prior to aliquot sampling. Forshipping field samples, use only e
37、poxy-lined steel cans thathave been cleaned according to Practice D4306.8.2 Store samples at normal room temperature (20 to 25C)or colder.8.3 Filter samples which contain free water or a water hazethrough a qualitative filter paper or a loose plug of cotton toremove such water.8.4 Laboratory Subsamp
38、lingSample fuel above its cloudpoint and thoroughly mix prior to aliquot sampling. At least 5mL of sample is required for each test. Follow Practices D4057and D5854. Use clean amber or clean borosilicate glasscontainers for laboratory handling. Shield fuel in clear bottlesfrom sunlight to prevent ph
39、otochemical reactions. Other labo-ratory containers may be used provided they are shown not toaffect the results of the test.8.5 Allow the test sample to reach the local ambienttemperature (10 to 30C) before commencing the test.9. Preparation and Calibration of Apparatus9.1 For portable use ensure t
40、hat the battery has beencharged.9.2 Zeroing the SpectrophotometerTurn on the portablespectrophotometer for at least 2 min. Fill a test cuvette withReagent 1, to within 5 mm of its top. Place the filled testcuvette into the spectrophotometer drawer. Zero both wave-lengths individually by separately p
41、ressing each select buttonand turning the corresponding zero button until 0.00 AU isdisplayed.9.2.1 Dispose of the cuvette and the aliquot of Reagent 1.Do not reuse the cuvette.NOTE 3The spectrophotometer is correctly calibrated if the twowavelength readings are 0.00 6 0.01 AU.9.3 VerificationA veri
42、fication fluid is under development.10. Procedure10.1 Pour 5 mL of Reagent 1 into a test tube and adda5mLaliquot of the test sample using Syringe 1. Stopper the test tubeand vigorously shake the test tube for 10 6 2s.10.2 Remove the stopper and add 35 L of Reagent 2 usingSyringe 2. Stopper the test
43、tube and vigorously shake the testtube for 10 6 2 s. Allow to settle for 30 to 35 min.10.3 Switch on the spectrophotometer at least 2 min beforethe end of the 30 min period.10.4 At the end of the 30 min period, use a pipette to drawthe darker reagent layer (at the top) from the test tube and totrans
44、fer that liquid to the test cuvette. Fill the cuvette to within5 mm of its top. (WarningHold the cuvette using the tworibbed sides to avoid affecting the optical path.)10.5 Place the cuvette (with the ribbed side towards thedrawer handle) in the spectrophotometer and close the drawer.10.6 Record the
45、 results from the digital display every 60 65 s until two readings agree within 0.02 AU and report thesecond of these reading as the measured relative absorbance.Record a negative result as zero.FIG. 1 SpectrophotometerD6748 02a (2012)311. Report11.1 Report the source, type, and identification of th
46、ematerial tested, plus the dates sampled and tested.11.2 Refer to this test method and report any deviation, byagreement or otherwise, from the procedure specified.11.3 Report the result of the test in absorbance units to thenearest 0.01 AU.12. Precision and Bias812.1 The precision of this test meth
47、od, as determined bystatistical analyses of interlaboratory results, is as follows:12.2 RepeatabilityThe difference between two test resultsobtained by the same operator with the same apparatus underconstant operating conditions, on identical test material would,in the long run, in the normal and co
48、rrect operation of the testmethod, exceed the following only in one case in twenty.r 5 0.0876 x10.2! AU (3)where:x = average of results being compared.12.3 ReproducibilityThe difference between two singleand independent results obtained by different operators work-ing in different laboratories on id
49、entical test material would, inthe long run, in the normal correct operation of the test method,exceed the following only in one case in twenty.R 5 0.1799 x10.2! AU (4)where:x = average of results being compared.12.4 BiasSince there is no accepted reference materialsuitable for determining the bias of the procedures in TestMethod D6748, bias cannot be determined.13. Keywords13.1 absorbance units; burner fuel; diesel fuel; infrared;infrared spectrophotometer; marine fuel; middle distillate fuel;potential instability; spectrometer; spectrophotometer;
