25th International Meeting on Organic Geochemistry IMOG 2011

P-235
Simulation of organic matter maturation in thermal waters by
model experiments
József Fekete 1 , Csanád Sajgó 1 , Áron Kramarics 2 , Zsuzsanna Eke 2 , Zoltán Kárpáti 1
1 Institute for Geochemical Research, Hungarian Academy of Sciences, Budapest, Hungary, 2 Eötvös Loránd
University, Joint Research and Training Laboratory on Separation Techniques, Budapest, Hungary
(corresponding author:feketej@geochem.hu)
Dissolved aromatic compounds in Hungarian thermal
waters were first reported and later described by
Kárpáti et al. [1, 2]. Among the identified compounds
were alkylbenzene, alkylthiophene, alkyl-indane and
heteroaromatic (pyrrole, furan) homologue series. The
appearance of dissolved organic compounds is bound
to a threshold temperature at ~70°C, and their
distribution is influenced by the water temperature.
Demethylation and aromatisation were observed with
increasing temperature. The origin of these
compounds is not known, precursor candidates are
lignites, humic substances, and bitumen.
Simulation experiments were carried out on different
materials: humic and fulvic acids (HA and FA); a HA
and FA mixture obtained from thermal water (HAFA),
bitumen obtained from lignite (BIT); a lignite sample
(C); and on organic matter precipitated on the filter of
an active geothermal well (P). The samples were
treated in a Parr reactor vessel in 3 g/L NaHCO3
distillated water for 24 or 72 hours on 220°C, 250°C,
300°C and 320°C under reductive conditions. Three
samples were treated under oxidative conditions too.
The compounds formed were identified by GC/MS. In
this paper we focus on volatile aromatic and
heteroaromatic compounds.
Under oxidative conditions the amount of benzene
increases and the amount of toluene and thiophene
decreases with increasing temperature. Other
alkylbenzenes are missing.
In the case of reductive sample treatment, with
increasing temperature the amounts of benzene,
toluene and thiophene increase in every sample. The
benzene/toluene ratio increases in FA, HAFA and P,
but decreases in HA, C and BIT (Fig. 1). Main
compounds are toluene and benzene. The amount of
thiophene increases, with the ratio of
thiophene/alkylbenzenes remaining constant up to
300°C, and decreasing at 320°C. C produces the
most thiophene.
The amount of heteroaromatics increases with
temperature, but the heteroaromatics/aromatics ratio
decreases. At higher temperatures the proportion of
heteroaromatic compounds containing N (pyrrole and
alkyl-pyrroles) decreases and S and O containing
ones (thiophene and furan homologues) become
dominant. The effects of duration and increasing
temperature are similar but not equal: demethylation
and aromatisation can be observed.
Fig. 1 Benzene and benzene/toluene distributions
This work was funded by the Hungarian Scientific
Research Fund (OTKA) through grant T 048829.
References
[1] Kárpáti, Z., Sajgó, Cs., Vető, I. Klopp, G. and
Horváth, I. 1995. Identification of various organics in
thermal waters in the Pannonian Basin. Preliminary
reports. Organic Geochemistry� Developments and
applications to energy, climate, environment and
human history. (eds. Grimalt J. O. and Dorronsoro
C.), A. I. G. O. A. Donostia-San Sebastian, 594-596.
[2] Kárpáti Z., Sajgó Cs., Vető I., Klopp G.,
Horváth I. 1999 Organic matter in thermal waters of
the Pannonian Basin - A preliminary report on
aromatic compounds. Organic Geochemistry 30(7):
701-712.
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