1、Designation: D7171 16Standard Test Method forHydrogen Content of Middle Distillate Petroleum Productsby Low-Resolution Pulsed Nuclear Magnetic ResonanceSpectroscopy1This standard is issued under the fixed designation D7171; the number immediately following the designation indicates the year oforigin
2、al 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. Scope*1.1 This test method covers the determination of the hydro-gen conte
3、nt of middle distillate petroleum products using alow-resolution pulsed nuclear magnetic resonance (NMR)spectrometer. The boiling range of distillates covered by thetest method is 150 C to 390 C. While this test method may beapplicable to middle distillates outside this boiling range, insuch cases t
4、he precision statements may not apply. The testmethod is generally based on Test Methods D3701 and D4808,with a major difference being the use of a pulsed NMRspectrometer instead of a continuous wave NMR spectrometer.1.2 The values stated in SI units are to be regarded asstandard. No other units of
5、measurement are included in thisstandard.1.2.1 The preferred units are mass %.1.3 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 deter
6、mine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D3701 Test Method for Hydrogen Content of AviationTurbine Fuels by Low Resolution Nuclear MagneticResonance SpectrometryD4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4808
7、 Test Methods for Hydrogen Content of LightDistillates, Middle Distillates, Gas Oils, and Residua byLow-Resolution Nuclear Magnetic Resonance Spectros-copyD5291 Test Methods for Instrumental Determination ofCarbon, Hydrogen, and Nitrogen in Petroleum Productsand LubricantsD6299 Practice for Applying
8、 Statistical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System PerformanceD6708 Practice for Statistical Assessment and Improvementof Expected Agreement Between Two Test Methods thatPurport to Measure the Same Property of a Material2.2 Other Documents:MIL-DTL-
9、5624 Turbine Fuel, Aviation, Grades JP-4 andJP-53MIL-DTL-83133 Turbine Fuel, Aviation, Kerosene Type,JP-8 (NATO F-34), NATO F-35, and JP-8+100 (NATOF-37)MIL-DTL-16884 Fuel, Naval Distillate3. Terminology3.1 Definitions:3.1.1 calibration, nthe determination of the values of thesignificant parameters
10、by comparison with values indicated bya set of calibration standards.3.1.2 calibration curve (or calibration line), nthe graphi-cal or mathematical representation of a relationship betweenthe assigned (known) values of calibration standards and themeasured responses from the measurement system.3.1.3
11、 calibration standard, na standard having an as-signed (known) value (reference value) for use in calibrating ameasurement instrument or system.This standard is not used todetermine the accuracy of the measurement instrument orsystem (see check standard).3.1.4 check standard, na material having an a
12、ssigned(known) value (reference value) used to determine the accu-racy of the measurement instrument or system. This standard is1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.03
13、on Elemental Analysis.Current edition approved Oct. 1, 2016. Published October 2016. Originallyapproved in 2005. Last previous edition approved in 2016 as D7171 05 (2016).DOI: 10.1520/D7171-16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at se
14、rviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available online at the ASSIST Quick Search website http:/quicksearch.dla.mil.*A Summary of Changes section appears at the end of this standardCopyright ASTM Internati
15、onal, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1not used to calibrate the measurement instrument or system(see calibration standard).3.1.5 low resolution nuclear magnetic resonance (NMR)spectroscopy, na form of NMR spectroscopy using a simpleNMR analyzer tha
16、t employs a low magnetic field and conse-quentially low NMR frequency. An example is proton NMRbelow 60 MHz. Resolution is expressed as time at half heightof signal and is typically 1 millisecond (ms) or less.3.1.6 nuclear magnetic resonance (NMR) spectroscopy,nthat form of spectroscopy concerned wi
17、th radio-frequency-induced transitions between magnetic energy levels of atomicnuclei.3.1.7 radio frequency, nthe range of frequencies of elec-tromagnetic radiation between 3 kHz and 300 GHz.3.1.8 recycle delay, nNMR spectrometer parameter set-ting for the time delay that allows magnetization recove
18、ry.3.1.9 relaxation time constant (T1), na numerical valuewhich is a measure of magnetization relaxation time followingan excitation pulse of an NMR spectrometer.4. Summary of Test Method4.1 Atest specimen is analyzed in a pulsed NMR spectrom-eter calibrated with reference standard materials. The an
19、alyzerrecords in a nondestructive fashion the total NMR signal,which arises from the absolute amount of hydrogen atoms inthe reference standards and test sample. The absolute hydrogensignal intensity reported by the pulsed NMR instrument for thestandard and test specimens is normalized by the corres
20、pond-ing sample mass. The resulting signal-per-gram ratios are usedas a means of comparing theoretical hydrogen contents of thestandards with that of the sample. The result is expressed as thehydrogen content (on a mass % basis) of the sample.4.2 To ensure an accurate measure of the absolute hydroge
21、ncontent of the reference standards and sample, it is necessary toensure that the measured hydrogen signal intensity is alwaysdirectly proportional to the absolute hydrogen content of thestandards and sample.4.3 Undercounting of the reference standard with respect tothe sample is avoided by a number
22、 of strategies, includingaccurate filling into the linear response region of the samplecompartment so that the mass recorded for the sample repre-sents the true amount measured by NMR, and use of a recycledelay considerably greater than the longest relaxation timeconstant (T1) for the sample.5. Sign
23、ificance and Use5.1 Hydrogen content represents a fundamental quality of apetroleum distillate that has been correlated with many of theperformance characteristics of that product. Combustion prop-erties of gas turbine fuels are related primarily to hydrogencontent. As hydrogen content of these fuel
24、s decreases, sootdeposits, exhaust smoke, and thermal radiation increase. Sootdeposits and thermal radiation can increase to the point thatcombustor liner burnout will occur. Hydrogen content is aprocurement requirement of the following military fuels: JP-5specified in MIL-DTL-5624, JP-8 specified i
25、n MIL-DTL-83133, and Naval Distillate Fuel specified in MIL-DTL-16884.5.2 This test method provides a simple and precise alterna-tive to existing test methods (D3701, D4808, and D5291) fordetermining the hydrogen content of petroleum distillate prod-ucts.6. Apparatus6.1 Nuclear Magnetic Resonance Sp
26、ectrometer:6.1.1 This test method requires a low-resolution pulsedinstrument capable of measuring a nuclear magnetic resonancesignal due to hydrogen atoms in the sample in a linear fashionover the filling volume of interest. The instrument includes thefollowing:6.1.1.1 Permanent magnet to provide th
27、e necessary staticmagnetic field for the NMR test,6.1.1.2 Sample compartment containing a radio frequency(RF) coil for excitation and detection, and6.1.1.3 Electronic unit to control and monitor the resonancecondition involving magnet temperature control and field offsetcoils.6.1.2 The test method a
28、lso requires that the instrument havethe ability to equilibrate samples within the probe at a constanttemperature (that is, 35 C or 40 C).6.2 Conditioning BlockBlock of aluminum alloy drilledwith holes of sufficient size to accommodate the nominal18 mm diameter test cells to a depth of at least 42 m
29、m and witha centrally positioned well to house a temperature-sensingdevice, such as a thermometer or thermocouple.6.3 Conditioning ApparatusBath or other temperaturecontrol device (into which the conditioning block is inserted)for controlling block temperature to 35 C 6 0.2 C or 40 C6 0.2 C.6.4 Test
30、 CellGlass tube (with a flat or round bottom) withan outside diameter of 17.6 mm to 18.1 mm and an insidediameter of 15.2 mm to 16.4 mm.Any tube length that permitseasy insertion into and removal from the NMR sample cham-ber may be used.6.5 Polytetrafluorethylene (PTFE) PlugDevice made ofPTFE used t
31、o tightly fit and close the test cells. An example ofone type of PTFE plug design is shown in Fig. 1.6.6 Insertion RodStraight, rigid rod with a threaded end(to screw into the PTFE plug) for inserting and removing thePTFE plugs from the test cells. Any diameter and length rodthat facilitates easy pl
32、ug insertion and removal may be used.6.7 Analytical BalanceTop loading pan-type balance, ca-pable of weighing the test cells in an upright position to anaccuracy of 0.001 g or better.6.8 Volume Transferring DeviceCapable of accurately andrepeatedly delivering a fixed volume of material within 61%or
33、better, for use in preparing test specimens and standards foranalysis. A 10 mL capacity serological pipet with 0.1 mLmarked subdivisions has been found suitable to use.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is
34、intended thatall reagents conform to the specifications of the Committee onD7171 162Analytical Reagents of the American Chemical Society wheresuch specifications are available.4Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use
35、without lessening the accuracy ofthe determination.7.2 List of Available Calibration, Reference, or CheckStandards (see Table 1). (WarningIrritant. Combustible.Avoid breathing vapor. Avoid contact with eyes, skin, andclothing.) applies to all of the following:7.2.1 3-cyclohexanepropionic acid, 99 %
36、minimum purity.7.2.2 cyclohexyl acetate, 99 % minimum purity.7.2.3 diethyl malonate, 99 % minimum purity.7.2.4 dodecane, 99 % minimum purity.7.2.5 ethyl caprate, 99 % minimum purity.7.2.6 ethyl heptanoate, 99 % minimum purity.7.2.7 2-nonanone, 99 % minimum purity.7.2.8 octyl acetate, 99 % minimum pu
37、rity.7.2.9 pentadecane, 99 % minimum purity.7.2.10 2-phenylethyl acetate, 99 % minimum purity.7.3 Quality Control (QC) Samples, preferably are portionsof one or more petroleum distillate materials that are stable andrepresentative of the samples of interest. These QC samplescan be used to monitor th
38、e precision and stability of the testingprocess as described in Section 15.8. Hazards8.1 Wear appropriate personal protective equipment whenworking with the materials in Section 7.Transfer all reagents ina fume hood and immediately seal containers tightly. Avoidprolonged or repeated exposure to mate
39、rials.9. Sampling9.1 Take a homogeneous sample in accordance with Prac-tice D4057. Mix the sample prior to taking a representativealiquot as the test specimen.10. Preparation of Test Specimens and Standards10.1 Fig. 1 is an example of a PTFE plug. Dimensions maybe varied to best seal the chosen test
40、 cell. Drill and thread theplug hole to mate the insertion rod thread. All test cells andPTFE plugs used shall be well cleaned and dry. Weigh a cleanempty test cell and PTFE plug (W1) on an analytical balance tothe nearest 0.001 g. Use of a jig for supporting the test cell onthe balance pan is recom
41、mended for flat bottom test cells andrequired for round bottom test cells. For round bottom testcells, a paper clip dispenser (with hole in top) works well forthis function. Transfer a fixed volume (in accordance with thetolerances specified in 6.8) of a reference standard or testspecimen into the t
42、est cell to a fill height of nominally 32 mm(representing a nominal 6 mL volume). The choice of fillheight is not critical, but fill height shall be the same for allstandards and samples to ensure good results. Use the same testcell source (that is, manufacturer and part number) for allstandards and
43、 test specimens. This will ensure uniformity offluid height in the NMR sample compartment, an importantparameter in the test method. Take care to not introduce thefluid down the side of the test cell. Seal the reference standardcontainer immediately after the material transfer to minimizemoisture pi
44、ckup. Using the insertion rod with a PTFE plugattached, push the PTFE plug into the test cell until it is justabove the liquid surface (that is, nominal 1 cm), keeping thetube upright. Gently twisting the plug as it is inserted will aidthe escape of air from the test cell and normally ensure that th
45、elip of the plug is turned up around the entire circumference.Unscrew the insertion rod carefully without disturbing theplug. Weigh the filled, sealed test cell (W2) on the analyticalbalance to the nearest 0.001 g. Determine the sample massfrom the difference (W2 W1) of the two weighings.4Reagent Ch
46、emicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand Natio
47、nal Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.FIG. 1 Example of a PTFE Plug (not to scale)TABLE 1 Hydrogen Content of Reference StandardsCompound Mass % Hydrogendodecane 15.386pentadecane 15.1852-nonanone 12.756ethyl caprate 12.077octyl acetate 11.703ethyl heptanoate 11.466
48、3-cyclohexanepropionic acid 10.324cyclohexyl acetate 9.924diethyl malonate 7.5522-phenylethyl acetate 7.367D7171 16310.2 Repeat 10.1 for all standards and test specimens.11. Preparation of Apparatus11.1 Place the conditioning block in the conditioning appa-ratus. Select a testing temperature of 35 C
49、 or 40 C based onthe NMR instrument manufacturers recommendation for thesample type to be tested. Adjust the conditioning apparatussetting to the selected 35 C 6 0.2 C or 40 C 6 0.2 Creading on a calibrated thermocouple or thermometer placed ina test cell filled with a test fluid and placed in the conditioningblock/apparatus. Allow at least 30 min for temperature equi-librium after a setting adjustment. After adjustment, measurethe aluminum block temperature at the thermometer/thermocouple well in the block, and control the conditioningapparatus
