25th International Meeting on Organic Geochemistry IMOG 2011

P-341
Simulation studies on the adsorption/occlusion phenomena
inside the macromolecular structures of asphaltenes
Jing Zhao 1,2 , Zewen Liao 1 , Patrice Creux 2 , Anna Chrostowska 3 , Alain Graciaa 2
1 State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of
Sciences, Guangzhou, China, 2 Laboratoire des Fluides Complexes, UMR 5150 TOTAL-CNRS-UPPA, Pau,
France, 3 Institut Pluridisciplinaire de Recherche sur l'Environnement et les Matériaux, UMR CNRS 5254,
UPPA, Pau, France (corresponding author:liaozw@gig.ac.cn)
Some microporous units were found inside the
macromolecular structures of asphaltenes, and some
other molecules can be occluded inside these
structural units. Mild oxidation treatment was applied
to release these occluded compounds and their
geochemical significance probed (Liao et al., 2006).
However, the adsorption/occlusion phenomena inside
asphaltenes are not commonly recognized by the
research colleagues and more efforts needed for
some further work in this field.
Then the asphaltenes, prepared from one low
matured crude oil from the Shengli Oilfield, North
China, was applied to simulate the occlusion
processes for the deuterated alkane n-C20D42 under
the conditions of high T, P. Three batches of
simulation experiments were performed under 240,
270 and 290 o C, respectively with the pressure at
20MPa inside the gold tubes for 72, 48 and 24 hours,
respectively. At the same time the control experiment
was carried out under ambient conditions. The
pyrolysates from the simulation experiments and the
mixtures from the control experiment were Soxhlet
extracted successively by n-hexane and acetone, and
then the occluded fractions were obtained according
to Zhao et al. (2010).
The experimental results indicate that
adsorption/occlusion extensively took place inside
asphaltenes. Fig.1 as exemplified from one simulation
experiment showed that the deuterated hydrocarbon
n-C20D42 was occluded inside the asphaltenes, while
n-C24D52 was used as the internal standard for
quantifying n-C20D42. Amounts of the occluded n-
C20D42 inside asphaltenes for different simulation
experimental compositions and the control experiment
were reported in Fig.2.
Adsorption/occlusion may occur through chemical
processes, e.g. polymerization or condensation of the
functional groups of the asphaltene molecules, and
then caves developed inside which some other
molecules are trapped. On the other hand,
adsorption/occlusion can take place through physical
processes possibly by the strong polar-polar
interactions such as H-bonding between asphaltene
molecules, and then inside the networks some other
compounds are trapped.
Fig.1. Chromatogram of the n-hexane eluents from
the oxidation products of pyrolysates from one
simulation experiment.
Fig.2. Histogram of the amounts of n-C20D42 (the
occluded fraction) from the pyrolysates from different
simulation experiments (based on the amount of initial
n-C20D42; CE for the result of control experiment).
References
Liao, Z., Geng, A., Graciaa, A., Creux, P.,
Chrostowska, A., Zhang, Y., 2006. Organic
Geochemistry 37, 291-303.
Zhao, J., Liao, Z., Zhang, L., Creux, P., Yang, C.,
Chrostowska, A., Zhang, H., Graciaa, A., 2010.
Applied Geochemistry 25, 1330-1338.
472