25th International Meeting on Organic Geochemistry IMOG 2011

P-084
The oil fraction composition of nonisothermic aquathermolysis
products of sulfur-rich native asphaltite in the 200−575°C
temperature range
Vladimir Antipenko
Institute of Petroleum Chemistry SB RAS, 4, Akademicheskiy Avenue, Tomsk, Russian Federation
(corresponding author:avr@ipc.tsc.ru)
Using a GC/MS method normal and isoprenoid
alkanes, steranes and pregnanes, hopanes and
cheilanthanes, mono-, bi-, tri- and tetracyclic aromatic
hydrocarbons, as well as bi-, tri and tetracyclic sulfurcontaining
aromatic compounds were identified in oil
fractions of the products of sulfur-rich native asphaltite
aquathermolysis carried out in a flow reactor at a
pressure of 15 MPa. The fractions were obtained at
the temperatures ranging from 200 to 575 °C. The
presence of alkenes (α-olefins) was typical only for
the products formed at temperature of 400−575 °С.
Aliphatic compounds were found to predominate
(50.34−89.90 %) in the oil fractions of
aquathermolysis products in the whole temperature
interval. The content of tetracyclic aromatic
hydrocarbons (0.08−0.94 % - total fluoranthene,
pyrene, chrysene and benzo[a]anthracene) and that
of tetracyclic sulfur-containing aromatic compounds
(0.05−0.87 % - total acenaphtho[1,2-c]thiophene and
three benzo[b]naphthothiophene isomers) were the
lowest.
Relative content of the compounds of different
types in oil fractions of the products obtained at
different temperatures varied in a polyextreme
manner. The highest total content of alkanes and αolefins
was observed at 575 °С (89.90 %). However
even at this temperature resin-asphaltene substances
generate a complete set of the compounds included
in the composition of oil fractions of the initial
asphaltite. Therefore excluding α-olefins these
compounds occur in resins and asphaltenes as
structural fragments.
The appearance of anthracene and 2methylanthracene
at high concentrations in the
products of aquathermolysis at 400−575 °С testifies
the presence of these compounds in resin and
asphaltene molecules as structural fragments.
Dihydroanthracene fragments of asphaltene and resin
molecules, which can undergo dehydrogenation
under the experiment conditions, can also be a
source of anthracene structures.
Phenylalkanes predominate among
monoalkylbenzenes in the oil fractions of the initial
asphaltite and in those of aquathermolysis products
obtained at the temperatures ranging from 200 to 450
°С, while at 475 °С and a higher temperature nalkylbenzenes
were found to predominate. It testifies
the presence of the latter in the molecules of resins
and asphaltenes as structural fragments.
For naphthalenes, phenanthrenes,
benzothiophenes and dibenzothiophenes a ratio of
high-molecular homologues to low-molecular ones
gradually increases to a certain limit and then it
noticeably decreases. The lowest values of these
ratios in dibenzothiophenes and phenanthrenes are
typical to the products obtained at the temperature
range of 475−575 °С. In case of benzothiophenes a
portion of high-molecular homologues (С5−С15)
noticeably decreases, while that of low-molecular
homologues (С2−С4) increases. It is conditioned by
the increased role of processes of alkyl chain
cracking.
In oil fractions of the initial asphaltite high- and
low-molecular steranes (steranes and pregnanes,
respectively) occur in comparable concentrations. At
increase in the temperature of products sampling a
portion of high-molecular homologues evidently
decreases and at 575 °С steranes are mainly
presented by low-molecular homologues – pregnanes
of С21 and С22 compositions.
A character of triterpane compositional changes
consists in a sharp increase of the relative content of
hopanes of С27 composition and in a noticeable
decrease of the relative content of homohopanes in
high-temperature products. It is important to notice
predominant generation of Tm isomer among hopanes
of C27 composition indicating a lower thermal maturity
of the ―bound‖ forms of hopanes as compared with
hopanes occurring in the oil fractions of the initial
asphaltite.
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