25th International Meeting on Organic Geochemistry IMOG 2011

P-358
Sulfur compounds in liquid products of the thermolysis of heavy
oil asphaltenes
Andrei Grinko, Anatoly Golovko, Raisa Min, Tatyana Sagachenko
Institute of Petroleum Chemistry Russian Academy Sciences Siberian Branch, Tomsk, Russian Federation
(corresponding author:)
Investigation of the structure and properties of
asphaltenes is of great importance for understanding
of their formation and geochemistry, as well as to
develop new ways of processing heavy crude oil,
natural bitumen and oil residues. Knowledge about
the composition of asphaltene molecules, the nature
(type) of structural fragments containing heteroatoms
is of particular importance, since they determine
thermal stability and reactivity of the asphaltene
molecules.
The purpose of this study is to investigate sulfurcontaining
fragments in the structure of the
asphaltene molecules.
Organic sulfur compounds, yielded by
thermolysis of asphaltenes occurring in heavy highsulfur
oil recovered from Usinsk oil field (Russia),
have been investigated.
The asphaltenes, isolated by 40-fold excess of nhexane,
were separated into 4 fractions (A1, A2, A3
and A4) by fractional precipitation with
chloroform:hexane mixtures 30:70, 30:75, 30:120 and
30:150, respectively. Molecular weights and contents
of heteroatoms (S, N and O) decreased from A1 to A4
fractions.
Thermolyses of the initial asphaltenes and their
fractions were carried out in a steel reactor 12 cm 3
during 1 hour at the preset temperatures: 160, 200,
250, 300, 450 and 650 °C. Temperatures correspond
to the maximum rates of fractions decomposition
recorded by a derivatograph. Thermolysis products
were separated into hydrocarbons (oil fraction) and
resins using a column liquid-adsorption
chromatography on silica gel. Oil fractions were
analyzed by gas chromatography-mass spectrometry
quadrupole system GCMS-QP5050 Shimadzu.
In the oil fraction of the products of the initial
asphaltene thermolysis carried out at 450 °C we
identified (in order of content decrease) unsubstituted
and alkyl-substituted (C1-C4) dibenzothiophenes,
phenanthro[4.5-bcd]thiophene, benzo[b]naphthothiophenes,
benzo[b]thiopheno[2.3.4.5-d.e.f] phenanthrene,
dinaphtho[2.3-b:2‘.3‘-d]thiophene,
perilo[1.12]thiophene, benzothieno[3.2-b]benzothiophene,
benzo[1.2-b:3.4-b']bis-benzothiophene and
4-phenyldibenzothiophene.
In the oil fraction of the thermolysis products up
to 300 °C sulfur compounds occurred in trace
quantities. Oil fraction of the thermolysis carried out at
300 °C contained mainly dibenzothiophene and its
alkyl substituted homologues. At the increase in the
temperature of the initial asphaltene thermolysis up to
650 °C we identified phenanthro [4,5-bcd]thiophene,
benzo[b]naphtho[1,2-d]thiophene, benzo[b]naphtho
[2,1-d]thiophene, benzo[b]naphtho[2,3-d]thiophene,
triphenyleno[1,12-bcd]thiophene, dinaphtho[2,3b:2‘,3‘-d]thiophene,
perilo[1,12-bcd]thiophene, benzothieno[3,2-b]benzothiophene,benzo[1,2-b:3,4-b']bisbenzothiophene
and 4-phenyldibenzothiophene in the
oil fraction. Dibenzothiophene was the main
component.
Oil fractions of the products of A1, A2 and A4
asphaltene fractions thermolysis carried out at 175 °C
and those of A3 fraction thermolysis at 210 ° C are
mainly represented by dibenzothiophene and alkyl
dibenzothiophene and phenanthro[4.5-bcd]
thiophene. At 455 °C thermolysis of asphaltene
fractions mainly yields benzothiophene and benzo[b]
naphthothiophene. Dibenzothiophene is a major
component generated by thermolysis at 650 °C
though a greater number of organic sulfur
compounds: phenanthro[4.5-bcd]thiophene,
benzo[b]naphthothiophene, benzo[b]thiopheno-
[2.3.4.5-d.e.f]phenanthrene, dinaphtho[2.3-b:2‘.3‘d]thiopheno,
perilo[1.12]thiophene, benzothieno[3.2b]benzothiophene,benzo[1.2-b:3.4-b']bisbenzothiophene
and 4-phenyldibenzothiophene are also
generated. Benzothiophene and its alkyl-substituted
homologues are found in trace quantities in the oil
fractions of the thermolyses (450, 455 and 650 °) of
the initial asphaltenes and their fractions.
It should be noted that the Usinsk oil contains
mainly benzo-, dibenzo- and naphthobenzothiophene
compounds and their homologues.
Thus, we have identified sulfur compounds which
occur as fragments in the structure of oil asphaltene
molecules. The asphaltenes contain all compounds
occurring in crude oil as structural fragments.
488