Published:Journal of Chromatographic Science,
ISSN 0021-9665 Volume
45, Number 10, November/December 2007, pp. 643-649
Towards Comprehensive Hydrocarbons Analysis of
Middle Distillates by LC–GC×GC
Frédérick Adam[1], Fabrice Bertoncini[1],
Didier Thiébaut[2], Sébastien Esnault[1], Didier
Espinat[1], and M.C. Hennion[2]
[1]Institut Français du Pétrole, Département
Physique et Analyse, BP3, 69390 Vernaison, France; and
[2]ESPCI,
Laboratoire Environnement et Chimie Analytique, 10 rue Vauquelin,
75235 Paris Cedex 05, France
The detailed characterization of middle distillates
is essential for a better understanding of reactions involved
in refining processes. Owing to a higher resolution power and
an enhanced sensitivity, but especially to a group-type ordering
in the chromatographic plane, comprehensive two-dimensional gas
chromatography (GC×GC) offers unsurpassed characterization
possibilities for petroleum samples. However, GC×GC fails
to totally discriminate naphthenes from unsaturates occurring
in hydrotreated diesel samples. This article aims at promoting
the implementation of LC–GC×GC for the quantitative
determination of hydrocarbon distribution in middle distillates,
including naphthenes. In this configuration, liquid chromatography
(LC) enables the separation of hydrocarbons into two fractions
(viz., saturated and unsaturated) before the subsequent analysis
of each fraction by GC×GC. In this paper, the choice of
GC×GC
conditions in order to achieve the separation and identification
of hydrocarbons by chemical class is discussed; under these conditions,
naphthenes are separated according to the number of saturated
rings. For the first time, the presence of di-, tri-, and tetra-naphthenes
resulting from the hydroconversion of aromatics can clearly be
evidenced. A quantitative procedure for the determination of
the distribution of hydrocarbons, including the distribution
of naphthenes according to the number of saturated rings, is
also proposed and discussed in detail. LC–GC×GC is
found to provide an unequalled degree of information that will
widely contribute to a better understanding of hydroconversion
processes.
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