ASTM D5292-99(2004)e1
(Test Method)Standard Test Method for Aromatic Carbon Contents of Hydrocarbon Oils by High Resolution Nuclear Magnetic Resonance Spectroscopy
Standard Test Method for Aromatic Carbon Contents of Hydrocarbon Oils by High Resolution Nuclear Magnetic Resonance Spectroscopy
SIGNIFICANCE AND USE
Aromatic content is a key characteristic of hydrocarbon oils and can affect a variety of properties of the oil including its boiling range, viscosity, stability, and compatibility of the oil with polymers.
Existing methods for estimating aromatic contents use physical measurements, such as refractive index, density, and number average molecular weight (see Test Method D 3238) or infrared absorbance and often depend on the availability of suitable standards. These NMR procedures do not require standards of known aromatic hydrogen or aromatic carbon contents and are applicable to a wide range of hydrocarbon oils that are completely soluble in chloroform at ambient temperature.
The aromatic hydrogen and aromatic carbon contents determined by this test method can be used to evaluate changes in aromatic contents of hydrocarbon oils due to changes in processing conditions and to develop processing models in which the aromatic content of the hydrocarbon oil is a key processing indicator.
TABLE 1 Sample and Instrument Conditions for Continuous Wave (CW) Measurements of 1 H NMR Spectra Solvent Chloroform-d Sample concentrationUp to 50 % v/v for distillable oils Sample temperatureInstrument ambient Internal lockNone Sample spinning rateAs recommended by manufacturer, typically 20 Hz r-f Power levelAs recommended by instrument manufacturer Signal to noise levelA minimum of 5:1 for the maximum height of the smaller integrated absorption band Chemical shift referencePreferably tetramethylsilane (0.0 ppm) at no greater than 1 vol % concentration IntegrationIntegrate over the range − 0.5 to 5.0 ppm for the aliphatic band and 5.0 to 10.0 ppm for the aromatic band
SCOPE
1.1 This test method covers the determination of the aromatic hydrogen content (Procedures A and B) and aromatic carbon content (Procedure C) of hydrocarbon oils using high-resolution nuclear magnetic resonance (NMR) spectrometers. Applicable samples include kerosenes, gas oils, mineral oils, lubricating oils, coal liquids, and other distillates that are completely soluble in chloroform at ambient temperature. For pulse Fourier transform (FT) spectrometers, the detection limit is typically 0.1 mol % aromatic hydrogen atoms and 0.5 mol % aromatic carbon atoms. For continuous wave (CW) spectrometers, which are suitable for measuring aromatic hydrogen contents only, the detection limit is considerably higher and typically 0.5 mol % aromatic hydrogen atoms.
1.2 The reported units are mole percent aromatic hydrogen atoms and mole percent aromatic carbon atoms.
1.3 This test method is not applicable to samples containing more than 1 mass % olefinic or phenolic compounds.
1.4 This test method does not cover the determination of the percentage mass of aromatic compounds in oils since NMR signals from both saturated hydrocarbons and aliphatic substituents on aromatic ring compounds appear in the same chemical shift region. For the determination of mass or volume percent aromatics in hydrocarbon oils, chromatographic, or mass spectrometry methods can be used.
1.5 The values stated in SI units are to be regarded as the standard.
1.6 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in 7.2 and 7.4.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
´1
Designation:D5292–99 (Reapproved 2004)
Standard Test Method for
Aromatic Carbon Contents of Hydrocarbon Oils by High
Resolution Nuclear Magnetic Resonance Spectroscopy
This standard is issued under the fixed designation D5292; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
´ NOTE—Corrected formatting in 12.2.1 and 12.2.2 editorially in October 2008.
1. Scope 2. Referenced Documents
1.1 This test method covers the determination of the aro- 2.1 ASTM Standards:
matic hydrogen content (Procedures A and B) and aromatic D3238 Test Method for Calculation of Carbon Distribution
carbon content (Procedure C) of hydrocarbon oils using and Structural Group Analysis of Petroleum Oils by the
high-resolution nuclear magnetic resonance (NMR) spectrom- n-d-M Method
eters. Applicable samples include kerosenes, gas oils, mineral D3701 Test Method for Hydrogen Content of Aviation
oils, lubricating oils, coal liquids, and other distillates that are TurbineFuelsbyLowResolutionNuclearMagneticReso-
completely soluble in chloroform at ambient temperature. For nance Spectrometry
pulse Fourier transform (FT) spectrometers, the detection limit D4057 Practice for Manual Sampling of Petroleum and
istypically0.1mol%aromatichydrogenatomsand0.5mol% Petroleum Products
aromatic carbon atoms. For continuous wave (CW) spectrom- E386 Practice for Data Presentation Relating to High-
eters, which are suitable for measuring aromatic hydrogen ResolutionNuclearMagneticResonance(NMR)Spectros-
contents only, the detection limit is considerably higher and copy
typically 0.5 mol % aromatic hydrogen atoms. 2.2 Energy Institute Methods:
1.2 The reported units are mole percent aromatic hydrogen IP Proposed Method BD Aromatic Hydrogen and Aromatic
atoms and mole percent aromatic carbon atoms. CarbonContentsofHydrocarbonOilsbyHighResolution
1.3 Thistestmethodisnotapplicabletosamplescontaining Nuclear Magnetic Resonance Spectroscopy
more than 1 mass % olefinic or phenolic compounds.
3. Terminology
1.4 Thistestmethoddoesnotcoverthedeterminationofthe
3.1 Definitions of Terms Specific to This Standard:
percentage mass of aromatic compounds in oils since NMR
signals from both saturated hydrocarbons and aliphatic sub- 3.1.1 aromatic carbon content—mole percent aromatic car-
bon atoms or the percentage of aromatic carbon of the total
stituents on aromatic ring compounds appear in the same
chemicalshiftregion.Forthedeterminationofmassorvolume carbon:
percent aromatics in hydrocarbon oils, chromatographic, or
aromatic carbon content 5100
mass spectrometry methods can be used.
3 ~aromatic carbon atoms!/~total carbon atoms! (1)
1.5 The values stated in SI units are to be regarded as the
3.1.1.1 Discussion—For example, the aromatic carbon con-
standard.
tent of toluene is 100 3(6/7) or 85.7 mol % aromatic carbon
1.6 This standard does not purport to address all of the
atoms.
safety problems, if any, associated with its use. It is the
3.1.2 aromatic hydrogen content—mole percent aromatic
responsibility of the user of this standard to establish appro-
hydrogen atoms or the percentage of aromatic hydrogen of the
priate safety and health practices and determine the applica-
total hydrogen:
bility of regulatory limitations prior to use. Specific precau-
tionary statements are given in 7.2 and 7.4.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This test method is under the jurisdiction of ASTM Committee D02 on contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
PetroleumProductsandLubricantsandisthedirectresponsibilityofSubcommittee Standards volume information, refer to the standard’s Document Summary page on
D02.04.0F on Absorption Spectroscopic Methods. the ASTM website.
Current edition approved Nov. 1, 2004. Published November 2004. Originally Available from Energy Institute, 61 New Cavendish St., London, WIG 7AR,
approved in 1992. Last previous edition approved in 1999 as D5292–99. U.K.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
´1
D5292–99 (2004)
aromatic hydrogen content 5100
suitable standards. These NMR procedures do not require
3 ~aromatic hydrogen atoms!/~total hydrogen atoms! (2)
standards of known aromatic hydrogen or aromatic carbon
contentsandareapplicabletoawiderangeofhydrocarbonoils
3.1.2.1 Discussion—For example, the aromatic hydrogen
that are completely soluble in chloroform at ambient tempera-
content of toluene is 100 3(5/8) or 62.5 mol % aromatic
ture.
hydrogen atoms.
5.3 The aromatic hydrogen and aromatic carbon contents
3.2 Definitions of chemical shift (reported in parts per
determinedbythistestmethodcanbeusedtoevaluatechanges
million (ppm)), internal reference, spectral width, and other
in aromatic contents of hydrocarbon oils due to changes in
NMR terminology used in this test method can be found in
processing conditions and to develop processing models in
Practice E386.
which the aromatic content of the hydrocarbon oil is a key
3.3 Chloroform-d refers to chloroform solvent in which
processing indicator.
hydrogen is replaced by deuterium, the heavier isotope of
hydrogen. Chloroform-d is available from a variety of chemi-
cal and isotope suppliers.
TABLE 1 Sample and Instrument Conditions for Continuous
Wave (CW) Measurements of H NMR Spectra
4. Summary of Test Method
Solvent Chloroform-d
4.1 Hydrogen ( H) nuclear magnetic resonance (NMR) Sample concentration Up to 50 % v/v for distillable oils
Sample temperature Instrument ambient
spectra are obtained on solutions of the sample in
Internal lock None
chloroform-d, using a CW or pulse FT high-resolution NMR
Sample spinning rate As recommended by manufacturer, typically 20 Hz
spectrometer. Carbon ( C) NMR spectra are obtained on
r-f Power level As recommended by instrument manufacturer
Signal to noise level A minimum of 5:1 for the maximum height of the
solutions of the sample in chloroform-d using a pulse FT
smaller integrated absorption band
high-resolution NMR spectrometer. Tetramethylsilane is pre-
Chemical shift reference Preferably tetramethylsilane (0.0 ppm) at no
ferred as an internal reference in these solvents for assigning greater than 1 vol % concentration
Integration Integrate over the range − 0.5 to 5.0 ppm for the
the 0.0 parts per million (ppm) chemical shift position in
aliphatic band and 5.0 to 10.0 ppm for the aromatic
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both H and C NMR spectra.
band
4.2 The aromatic hydrogen content of the sample is mea-
sured by comparing the integral for the aromatic hydrogen
bandinthe HNMRspectrum(5.0to10.0ppmchemicalshift
6. Apparatus
region) with the sum of the integrals for both the aliphatic
hydrogen band (−0.5 to 5.0 ppm region) and the aromatic
6.1 High-Resolution Nuclear Magnetic Resonance
hydrogen band (5.0 to 10.0 ppm region).
Spectrometer—A high-resolution continuous wave (CW) or
4.3 The aromatic carbon content of the sample is measured
pulse Fourier transform (FT) NMR spectrometer capable of
by comparing the integral for the aromatic carbon band in
beingoperatedaccordingtotheconditionsinTable1andTable
the C spectrum (100 to 170 ppm chemical shift region) with
2andofproducingpeakshavingwidthslessthanthefrequency
thesumoftheintegralsforboththealiphaticcarbonband(−10
ranges of the majority of chemical shifts and coupling con-
to 70 ppm region) and the aromatic carbon band (100 to 170
stants for the measured nucleus.
ppm region).
6.1.1 H NMR spectra can be obtained using either CW or
4.4 The integral of the aromatic hydrogen band must be
pulse FT techniques but C measurements require signal
corrected for the NMR absorption line due to residual chloro-
averaging and, therefore, currently require the pulse FT tech-
form (7.25 ppm chemical shift) in the predominantly
nique. Low resolution NMR spectrometers and procedures are
chloroform-d solvent.
not discussed in this test method (see Test Method D3701 for
4.5 The integrals of the aliphatic hydrogen band and of the
an example of the use of low resolution NMR).
aliphatic carbon band must be corrected for the NMR absorp-
6.2 Tube Tubes—Usuallya5or10mm outside diameter
tion line due to the internal chemical shift reference tetrameth-
tube compatible with the configuration of the CW or pulse FT
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ylsilane (0.0 ppm chemical shift in both H and C spectra).
spectrometer.
5. Significance and Use
7. Reagents and Materials
5.1 Aromatic content is a key characteristic of hydrocarbon
7.1 Purity of Reagents—Reagent grade chemicals shall be
oilsandcanaffectavarietyofpropertiesoftheoilincludingits
used in all tests. Unless otherwise indicated, it is intended that
boiling range, viscosity, stability, and compatibility of the oil
all reagents shall conform to the specifications of the Commit-
with polymers.
tee onAnalytical Reagents of theAmerican Chemical Society,
5.2 Existing methods for estimating aromatic contents use
where such specifications are available. Other grades may be
physical measurements, such as refractive index, density, and
used, provided it is first ascertained that the reagent is of
numberaveragemolecularweight(seeTestMethodD3238)or
sufficiently high purity to permit its use.
infrared absorbance and often depend on the availability of
“Reagent Chemicals, American Chemical Society Specification.” American
Brandes, G., “The Structural Groups of Petroleum Fractions. I. Structural Chemical Society, Washington, D.C. For suggestions on the testing of reagents not
GroupAnalysisWiththeHelpofInfraredSpectroscopy,” Brennstoff-ChemieVol37, listed by the American Chemical Society, see “Analar Standards for Laboratory
1956, p. 263. U.K. Chemicals,” BDH Ltd., Poole, Dorset, and the “United States Pharmacopeia.”
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D5292–99 (2004)
TABLE 2 Sample and Instrument Conditions for Pulse Fourier
7.4 Chromium (III) 2,4-Pentanedionate, relaxation reagent
1 13
Transform Measurements of H and C NMR Spectra 13
for C NMR spectra, typically 97% grade.
Solvent:
H NMR Chloroform-d
8. Sampling
C NMR Chloroform-d
Sample concentration:
8.1 It is assumed that a representative sample acquired by a
H NMR Must be optimized for the instrument in use but
procedure of Practice D4057 or equivalent has been received
may be as high as 5 % v/v
C NMR Up to 50 % v/v for petroleum distillates and 30 %
inthelaboratory.Ifthetestisnottobeconductedimmediately
v/v for coal liquids
upon receipt of the sample, store in a cool place until needed.
Relaxation agent Chromium (III) 2,4-pentanedionate recommended
for C NMR solutions only. Where used, a 20 mM 8.2 A minimum of approximately 10 mL of sample is
solution (about 10 mg per mL)
required for this test method. This should allow duplicate
Sample temperature Instrument ambient
1 determinations, if desired.
Internal lock Deuterium (when chloroform-d is used for H
NMR)
8.3 All samples must be homogeneous prior to subsam-
Sample spinning rate As recommended by manufacturer, typically 20 Hz
pling. If any suspended particles present are attributable to
1 13
H Decoupling Only for C NMR. Broadband over the whole of
1 13
foreign matter such as rust, filter a portion of the sample to be
the H frequency range, gated on during C data
acquisition only with a decoupler rise time less
tested through a small plug of glass wool, contained in a clean
than2m/s
small funnel, into a clean and dry vial or NMR sample tube
Pulse flip angle Approximately 30°
containing chloroform-d.
Sequence delay time:
HNMR>10s
8.4 If the sample contains waxy materials, heat the sample
CNMR>3swith and> 60 s without relaxation
in the container to approximately 60°C and mix with a
agent
Memory size for Choose to give a minimum digitizing rate of 0.5
high-shear mixer prior to sampling. It may be necessary to
1 13
acquisition: Hz/point for H and 1.2 Hz/point for C NMR. If
transfer a portion of the sample to an NMR tube containing
necessary, increase memory size and zero fill
chloroform-d by means of a pipet which has been heated to
Spectral width:
H NMR At least 15 ppm in frequency and centered, as
approximately 60°C to maintain the homogeneity of the
close as possible, to the 5 ppm chemical shift
sample.
value
C NMR At least 250 ppm in frequency and centered, as 8.5 For a valid test result, samples must be completely
close as possible, to the 100 ppm chemical shift
solubleinchloroform-d.Checktoensurethatthefinalsolution
value
is homogeneous and free of undissolved particles.
Filter bandwidth Set to be equal to or greater than the spectral
width and as permitted by the instrument’s filter
hardware
9. Procedures
Exponential line Set at least equal to the digitizing rate
broadening
9.1 Three different procedures are described in this section
Signal to noise levels:
for determining the aromatic hydrogen content, (see 9.6)
H NMR A minimum of 20:1 for the maximum height of the
smaller integrated band ProceduresAand B (see 9.7), and the aromatic carbon content
C NMR A minimum of 60:1 for the maximum height of the
of hydrocarbon oils, Procedure C (see 9.8).
chloroform-d resonance appearing between 75 and
9.2 Theprocedureselectedbytheanalystwilldependonthe
80 ppm on the chemical shift scale
Chemical shift reference:
available NMR instrumentation and on whether an aromatic
H NMR Preferably tetramethylsilane (0.0 ppm) at no
hydrogen or aromatic carbon content is of greater value in
greater than 1 vol % concentration
evaluating the characteristics of the hydrocarbon oil.
C NMR Preferably tetramethylsilane (0.0 ppm) at no
greater than 1 vol % concentration. If this
9.3 Appendix X1 and Practice E386 should be used in
reference is not used, the central peak of
conjunction with the NMR spectrometer manufacturer’s in-
chloroform-d is set to 77.0 ppm
Integration:
structionsinordertoensureoptimumperformanceoftheNMR
H NMR Integrate over the range − 0.5 to 5.0 ppm for the
instrument in the application of these procedures.
aliphatic band and 5.0 to 10.0 ppm for the aromatic
9.4 If tetramethylsilane is used as an internal chemical shift
band
C NMR Integrate over the range − 10 to 70 ppm for the
standard,preparea1%v/vTMSinsolventsolutionbyadding
aliphatic band and 100 to 170 ppm for the aromatic
tetramethylsilane to chloroform-d solvent. Since TMS is very
band
volatile, this solution should be refrigerated or replaced if the
characteristic absorption due to TMS is no longer evident in
1 13
theHor C NMR spectrum.
9.5 If it is inconvenient to prepare the test solution directly
7.2 Chloroform-d—For
...
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