Supplementary Information
GROUP TYPE SEPARATION OF NITROGEN CONTAINING AROMATIC
COMPOUNDS IN COAL TAR PITCH ON A HAFNIUM MODIFIED SILICA HPLC
PHASE
Andreas Gole, Jan T. Andersson
Department of Inorganic and Analytical Chemistry, University of Muenster
Corrensstrasse 30, 48149 Muenster, Germany
E-mail: anderss@uni-muenster.de
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1. Separation of standard compounds on metal-modified silica
Figure S1. Separation of 3-octylindole on the Zr/SiO2- phase at 2 mL min-1. Step gradient:
0-80 min cyclohexane, 80-150 min cyclohexane/dichloromethane (60:40). The neutral PANH
octylindole does not elute in the first fraction even after an extended time with cyclohexane.
Figure S2. Separation of benzo[4,5]thieno[2,3-a]carbazole on the Zr/SiO2- phase at
2 mL min-1. Step gradient: 0-80 min cyclohexane, 80-150 min cyclohexane/dichloromethane
(60:40). The neutral PANH does not elute in the first fraction even after an extended time
with cyclohexane.
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Figure S3. HPLC-chromatogram for the separation of 1-naphthylamin and 4-methylquinoline
on the Zr/SiO2-phase (top) and the resulting GC-FID-chromatograms of the two fractions
collected between 40-60 min (middle) and 60-80 min (bottom), showing the complete
separation on this phase of an amino-PAH and a basic PANH. .
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2. Additional chromatograms for the separation of a coal tar pitch on Hf/SiO2-phase
Figure S4. GC-MS chromatograms of the non-nitrogen containing compounds (first fraction)
after separation of the coal tar pitch on the Hf/SiO2 phase. Extracted ions 128 (naphthalene),
178
(phenanthrene/anthracene),
(fluoranthene/pyrene),
216
192
(methylphenanthrenes/methylanthracenes),
(methylfluoranthenes/methylpyrenes)
and
202
228
(benzo[a]anthracene/chrysene).
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3. Analysis of nitriles in fossil fuel
Nitriles in fossil material have not been extensively investigated and there is a lack of
published methods. One method describes the reduction of nitriles with sodium borohydride
[S1] but it is time consuming and the method is not quantitative. Other publications deal with
an extraction of the characteristic mass fragment m/z 110 for alkyl nitriles in GC-MS
measurements [S2] but this leads to problems in complex mixtures, especially when aromatic
nitriles are analyzed. Nitriles have been suggested to be formed in a thermal reaction between
carboxylic acids and ammonium ions present in the rocks when a shale oil is distilled [S3].
The workup procedure for their analysis included passing the oil through two ion exchange
columns. Straight-chain C12-C15-nitriles were found in a Colorado shale oil after a very
complex workup [S2]. Hydrolysis of nitriles to the carboxylic acids followed by extraction
and esterification was used to reveal n-alkyl-, monoaromatic and two napthonitriles in a shale
oil [S4]. It is obvious that simpler work-up schemes are desirable.
Nitriles elude ionization with MS techniques like electrospray ionization and thus do not
interfere with isomeric neutral PANHs which can be detected in the negative mode due to
their weak acidity. Electron impact in GC is capable of ionizing nitriles but this is true for
neutral PANHs also and thus no selectivity is obtained. Added to this are the volatility
constraints in GC so that the heavier fractions of a fossil material cannot be analyzed. Figure
S5 shows examples of the isomerism of neutral PANHs and nitriles.
CN
CN
NH
2-methylbenzonitrile
m/z 117.05785
indole
m/z 117.05785
N
H
8-methyl-1-naphthonitrile
m/z 167.07350
carbazole
m/z 167.07350
Figure S5. Examples for isomeric forms of neutral nitrogen containing compounds.
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4. Preparation of CPO-27-Ni
5.3 g (21 mmol) of nickel(II) acetate was dissolved in 40 mL of demineralized water and
added to a solution containing 2.1 g (10.6 mmol) 2,5-dihydroxyterephthalic acid in 40 mL
tetrahydrofuran. The reaction was initiated with 1 mL of triethylamine and allowed to reflux
for 3 days. The product was filtered and washed with demineralized water and
tetrahydrofuran. The residual yellowish fine crystalline compounds were dried and slurried in
dichloromethane. After the small particles were decantated off, the residual particles were
packed in an HPLC column (120 x 4.6 mm).
5. Analysis of standard compounds on the CPO-27-Ni-phase
A chromatographic separation of standard compounds showed the efficiency of the CPO-27column
for
this
purpose
(Figure
S6).
We
used
2,3-dimethylindole,
carbazole,
2-naphthylacetonitrile and 9-anthracenecarbonitrile and analyzed the two obtained fractions
offline by GC-MS to identify in which fraction the injected standard compounds appeared.
The neutral PANHs were recovered in the first and the aromatic nitriles in the second fraction.
Figure S6. Chromatogramm of a standard mixture on the CPO-27-Ni. Step gradient: 0-25 min
cyclohexane/dichloromethane (60:40); 25-37.5 min tetrahydrofuran at 0.5 ml min-1.
Compounds: 1): 2,3-dimethylindole, carbazole; 2): 2-naphthylacetonitrile, 9-anthracene
carbonitrile.
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6. Analysis of a coal tar pitch on the CPO-27-Ni-phase
The second fraction of the separation of the coal tar pitch on the Hf/SiO2 phase was separated
on the MOF as indicated in Figure S7. The flow rates for the real world sample had to be
reduced from 0.5 to 0.3 mL min-1 to obtain the same pressure as in the standard measurements
(335 to 355 bar) since with increased use the finely crystalline MOF material led to an
increased back-pressure. The sample was eluted successively with the two solvent systems
and each fraction was collected and analyzed offline by GC-MS.
All identified neutral PANHs of the second Hf/SiO2 fraction were recovered in the first
fraction (Figure S8) of the MOF-separation. The aromatic nitriles are completely absent in
this fraction as expected and occur in the second fraction (Figure S9.S9). The most abundant
signals indicate naphthonitriles, methylnaphthonitriles and anthracenecarbonitriles. There are
still traces of neutral PANHs in this fraction but we assume that they can be eluted in the first
fraction if the amount of sample injected is decreased somewhat or the time for collecting the
first fraction is increased. Even with this slight overlap, the ratio of the two isomers
methylnaphthonitrile and carbazole has changed from 1:317 to 1:1.8, making this nitrile easily
analyzable.
Methylnaphthonitrile and anthracene/phenanthrenecarbonitrile were also detected in the
second fraction. This separation seems to be a reasonably simple chromatographic method for
the collection of aromatic nitriles from such a complex matrix as a coal tar pitch.
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Figure S7. Separation scheme for the isolation of nitriles.
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Figure S8. GC-MS-chromatograms of the neutral PANHs (first fraction) of the coal tar pitch
on CPO-27-Ni.
Figure S9. GC-MS chromatograms of the nitriles (second fraction) on CPO-27-Ni.
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REFERENCES:
[S1] T. Iida, E. Yoshii, E. Kitatsuji, Anal. Chem. 38 (1966) 1224.
[S2] H. Long, Q. Shi, N. Pan, Y. Zhang, D. Cui, K.H. Chung, S. Zhao, C. Xu, Energy Fuels
26 (2012) 3424.
[S3] E.J. Evans, B.D. Batts, N.W. Cant, J.W. Smith, Org. Geochem. 8 (1985) 367.
[S4] T.G. Harvey, T.W. Matheson, K.C. Pratt, J. Chromatogr. A 435 (1988) 193.
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