25th International Meeting on Organic Geochemistry IMOG 2011

P-010
Acidic fraction analyses of Brazilian oils using petroleomics
Célio Fernando Figueiredo Angolini 1 , Eugenio Vaz dos Santos Neto 2 , Anita Jocelyne
Marsaioli 1
1 Chemistry Institute, University of Campinas - UNICAMP, Campinas, Brazil, 2 PETROBRAS R&D Center,
Cidade Universitária, Brazil (corresponding author:anita@iqm.unicamp.br)
Introduction
Recent advances in mass spectrometry allow a more
precise and rapid characterization of petroleum
constituents for the determination of the elemental
composition of heteroatoms containing species (N, S
and O). These components are important in studies
focusing solid deposition, floculation, catalyst
deactivation, refinary corrosion problems and storage
instability. This methodology has been named
petroleomics [ 1], however petroleomics parameters
have not been correlated to the organic geochemical
parameters yet. Considering this premise, we used
samples of naturally biodegraded petroleum which
were previously characterized in order to correlate the
O2 class compositional variation to the biodegradation
process.
Material and Methods
Representative samples of lacustrine oils with P&M
biodegradation levels from 1 to 7 [2] from the Campos
Basin were used in the study. Biodegradation
intensity increases in the following order: P1, P5, P3,
P2 and P4 samples. Acidic fraction of petroleum
samples were obtained by KOH modified silica gel
column chromatography (200 g of silica + 40g of
KOH), eluted with ether (neutral fraction) and
diethylether:formic acid 20% (acidic fraction). These
were typically dissolved at 0.5 mg mL -1 in toluene:
methanol (1:1 vol:vol) with 0.5 % of NH4OH for ESI
analysis by a ESI GC/MS LTQ XL Orbitrap (Thermo
Scientific).
Results and Discussion
The bulk distribution of some classes of compounds
in the acidic fractions of the oil samples are depicted
in Figure 1. Typically biodegradation occur by
depletion of the less complex, hydrogen-rich
compounds first shifting the maximum of the O2 class
to lower levels of DBE (P1 to P5). Analyzing the
carboxylic acid ratios, Table 1, of compounds with
DBE 4 (tricyclic terpanoic acids)/DBE 3, DBE 6
(hopanoic acids)/ DBE 3 and DBE 8 (naphthalenic
acids)/ DBE 3 (bicyclic acids, more abundant) it can
be observed a general increasing trend of these ratios
with the growing intensity of biodegradation. These
bulk parameters are consistent with the classical
rational that bicyclic terpanoic acids DBE 3 are more
abundant and usually present in a wide range of
biodegraded samples.
DBE
DBE
20
10
0
0 10 20 30 40 50 60 70
20
10
0.000
12.50
25.00
37.50
50.00
62.50
75.00
87.50
100.0
0.000
12.50
25.00
37.50
50.00
62.50
75.00
87.50
100.0
Carbon number
P1 - O 2
0
0 10 20 30 40 50 60 70
Carbon number
DBE
20
10
0.000
12.50
25.00
37.50
50.00
62.50
75.00
87.50
100.0
P3 - O 2
DBE
DBE
0
0 10 20 30 40 50 60 70
Figure 1 – Plots of DBE versus carbon number for O2 class
species from the negative-ion ESI LTQ XL Orbitrap of acid
fraction, using Origin® 8.
Table 1 – Ratios of compound class in oil samples.
DBE P1 P5 P3 P2 P4
4/3 0.97 0.99 0.82 0.7 0.92
6/3 0.63 0.50 0.49 0.39 0.57
8/3 0.44 0.38 0.28 0.21 0.31
Conclusion
Results confirm that the bulk analysis of the acidic
components can be readily assessed in crude oils or
in acidic fractions by petroleomics, providing a rapid
characterization of crude oils regarding their
biodegradation levels. Caution should be taken when
applied this approach for oils with P&M
biodegradation levels higher than 6.
References
[1] Marshall, A.G., Rodgers, R.P. (2008) PNAS, 105,
18090-18095.
[2] Peters & Moldowan (1993).The Biomarker Guide.
Acknowledgment
20
10
0.000
12.50
25.00
37.50
50.00
62.50
75.00
87.50
100.0
0
0 10 20 30 40 50 60 70
20
10
Carbon number
0.000
12.50
25.00
37.50
50.00
62.50
75.00
87.50
100.0
Carbon number
P5 - O 2
P2 - O 2
0
0 10 20 30 40 50 60 70
Carbon number
P4 - O 2
158