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Petroleum Analysis
10.7.1 InFrAred sPeCtrosCoPy
Conventional infrared spectroscopy yields information about the functional features of various
petroleum constituents. For example, infrared spectroscopy will aid in the identification of N–H
and O–H functions, the nature of polymethylene chains, the C–H out-of-place bending frequencies,
and the nature of any polynuclear aromatic systems.
With the recent progress of Fourier transform infrared (FTIR) spectroscopy, quantitative estimates of the various functional groups can also be made. This is particularly important for application to the higher molecular weight solid constituents of petroleum (i.e., the asphaltene fraction).
It is also possible to derive structural parameters from infrared spectroscopic data and these are
(1) saturated hydrogen to saturated carbon ratio; (2) paraffinic character; (3) naphthenic character;
(4) methyl group content; and (5) paraffin chain length.
In conjunction with proton magnetic resonance (PMR) (see next section), structural parameters
such as the fraction of paraffinic methyl groups to aromatic methyl groups can be obtained.
10.7.2 nuCleAr mAgnetIC resonAnCe
Nuclear magnetic resonance has frequently been employed for general studies and for the structural
studies of petroleum constituents (Hasan et al., 1989). In fact, PMR studies (along with infrared
spectroscopic studies) were, perhaps, the first studies of the modern era that allowed structural
inferences to be made about the polynuclear aromatic systems that occur in the high molecular
weight constituents of petroleum.
In general, the proton (hydrogen) types in petroleum fractions can be subdivided into five types
which subdivides the hydrogen distribution into (1) aromatic hydrogen, (2) substituted hydrogen
next to an aromatic ring, (3) naphthenic hydrogen, (4) methylene hydrogen, and (5) terminal methyl
hydrogen remote from an aromatic ring. Other ratios are also derived from which a series of structural parameters can be calculated.
However, it must be remembered that the structural details of the carbon backbone obtained from
proton spectra are derived by inference but it must be recognized that protons at peripheral positions
can be obscured by intermolecular interactions. This, of course, can cause errors in the ratios that
can have a substantial influence on the outcome of the calculations (Ebert et al., 1987).
It is in this regard that carbon-13 magnetic resonance (CMR) can play a useful role. Since carbon magnetic resonance deals with analyzing the carbon distribution types, the obvious structural
parameter to be determined is the aromaticity, f a . A direct determination from the various carbon
type environments is one of the better methods for the determination of aromaticity (Snape et al.,
1979). Thus, through a combination of proton and carbon magnetic resonance techniques, refinements can be made on the structural parameters and for the solid state high resolution CMR technique additional structural parameters can be obtained (Weinberg et al., 1981).
10.7.3 mAss sPeCtrometry
Mass spectrometry can play a key role in the identification of the constituents of feedstocks and
products. The principal advantages of mass spectrometric methods are (1) high reproducibility
of quantitative analyses, (2) the potential for obtaining detailed data on the individual components and/or carbon number homologues in complex mixtures, and (3) a minimal sample size
is required for analysis. The ability of mass spectrometry to identify individual components in
complex mixtures is unmatched by any modern analytical technique. Perhaps the exception is gas
chromatography.
However, there are disadvantages arising from the use of mass spectrometry and these are:
(1) the limitation of the method to organic materials that are volatile and stable at temperatures
Petroleum Analysis
10.7.1 InFrAred sPeCtrosCoPy
Conventional infrared spectroscopy yields information about the functional features of various
petroleum constituents. For example, infrared spectroscopy will aid in the identification of N–H
and O–H functions, the nature of polymethylene chains, the C–H out-of-place bending frequencies,
and the nature of any polynuclear aromatic systems.
With the recent progress of Fourier transform infrared (FTIR) spectroscopy, quantitative estimates of the various functional groups can also be made. This is particularly important for application to the higher molecular weight solid constituents of petroleum (i.e., the asphaltene fraction).
It is also possible to derive structural parameters from infrared spectroscopic data and these are
(1) saturated hydrogen to saturated carbon ratio; (2) paraffinic character; (3) naphthenic character;
(4) methyl group content; and (5) paraffin chain length.
In conjunction with proton magnetic resonance (PMR) (see next section), structural parameters
such as the fraction of paraffinic methyl groups to aromatic methyl groups can be obtained.
10.7.2 nuCleAr mAgnetIC resonAnCe
Nuclear magnetic resonance has frequently been employed for general studies and for the structural
studies of petroleum constituents (Hasan et al., 1989). In fact, PMR studies (along with infrared
spectroscopic studies) were, perhaps, the first studies of the modern era that allowed structural
inferences to be made about the polynuclear aromatic systems that occur in the high molecular
weight constituents of petroleum.
In general, the proton (hydrogen) types in petroleum fractions can be subdivided into five types
which subdivides the hydrogen distribution into (1) aromatic hydrogen, (2) substituted hydrogen
next to an aromatic ring, (3) naphthenic hydrogen, (4) methylene hydrogen, and (5) terminal methyl
hydrogen remote from an aromatic ring. Other ratios are also derived from which a series of structural parameters can be calculated.
However, it must be remembered that the structural details of the carbon backbone obtained from
proton spectra are derived by inference but it must be recognized that protons at peripheral positions
can be obscured by intermolecular interactions. This, of course, can cause errors in the ratios that
can have a substantial influence on the outcome of the calculations (Ebert et al., 1987).
It is in this regard that carbon-13 magnetic resonance (CMR) can play a useful role. Since carbon magnetic resonance deals with analyzing the carbon distribution types, the obvious structural
parameter to be determined is the aromaticity, f a . A direct determination from the various carbon
type environments is one of the better methods for the determination of aromaticity (Snape et al.,
1979). Thus, through a combination of proton and carbon magnetic resonance techniques, refinements can be made on the structural parameters and for the solid state high resolution CMR technique additional structural parameters can be obtained (Weinberg et al., 1981).
10.7.3 mAss sPeCtrometry
Mass spectrometry can play a key role in the identification of the constituents of feedstocks and
products. The principal advantages of mass spectrometric methods are (1) high reproducibility
of quantitative analyses, (2) the potential for obtaining detailed data on the individual components and/or carbon number homologues in complex mixtures, and (3) a minimal sample size
is required for analysis. The ability of mass spectrometry to identify individual components in
complex mixtures is unmatched by any modern analytical technique. Perhaps the exception is gas
chromatography.
However, there are disadvantages arising from the use of mass spectrometry and these are:
(1) the limitation of the method to organic materials that are volatile and stable at temperatures