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In the conversion of heavy oil into valuable fuels by thermal processes, one of the main problems is the formation of soft coke-like substances that can cause equipment fouling and catalyst deactivation. Asphaltenes are present in large quantity in heavy crude oil and are known to be coke precursors. The objective of the present study was to obtain chemical structure information about the asphaltene molecules when they undergo a thermal treatment and to investigate the mechanism of coke formation. Asphaltenes were separated from two industrial thermal treated heavy crude oils and characterized by elemental analysis, NMR, FTIR, and FT-ICR MS. Analytical data were then compared with that obtained from asphaltene samples after thermal treatment at 400 °C. From complementary and comparative use of the different analytical techniques, we demonstrated that asphaltenes thermally treated at 400 °C tend to aromatize to form coke precursors. We found that the species rich in saturated rings and/or alkyl chains are less stable than the one containing aromatic rings; the main reaction in thermal treatment is the intramolecular cyclization/aromatization and not the cleavage of residual aliphatic chains. Moreover, asphaltene classes containing sulfur atoms present a lower stability than the other species.

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A strain of Aspergillus terreus was isolated from a polycyclic aromatic hydrocarbons (PAHs) polluted soil. The metabolism of pyrene and benzo(a)pyrene by this fungus was investigated in liquid submerged culture added of 50 and 25 ppm respectively of each compound. Depletion of pyrene and Benzo(a)pyrene was evident during the first stages of growth and was 60% and 27.5% respectively of the added amount after nine days of culture. Solvent extracts of the fermentation broth and mycelium were analysed for presence of metabolites by HPLC-MS technique. Under the present cultural conditions pyrene was mainly metabolised to pyrenylsulfate similarly to benzo(a)pyrene that led to benzo(a)pyrenylsulfate. The structure of 1-pyrenilsulfate was determined after purification of extracts and H-NMR analysis. The result show that the isolated A. terreus strain metabolises PAHs by reaction similar to those previously reported for non lignolinolytic fungi with a mechanism that suggests the hydroxylation by a cytochrome P-450 monooxygenase followed by conjugation with sulfate ion.

The aggregation in solution of the dinuclear palladium(I) complex [(Phen)2Pd2(μ-H)(μ-CO)]+BArF 4 - (1c) was investigated by PGSE NMR, UV−vis, and ESI- and FAB-mass techniques. PGSE measurements showed that only the cationic moiety of 1c (1c + ) is involved in the aggregation process, while the counteranion does not participate in it. By using compound [Pd(Phen)(Me)Cl] (2) as an external standard, it was found that, depending on the solution concentration, the volume ratio V 1c + /V 2 ranges from 7.2 to 40.2 in nitrobenzene-d 5 at 296 K. The V 1c + /V 2 value (ca. 5.5) extrapolated to infinite dilution indicates that, even at very low concentration values, at least two units of 1c + are associated to form a dimer. At the highest possible concentration (55.20 mM) a mean aggregate bearing about 20 1c + units is present in solution, having an average hydrodynamic radius of 11−12 Å. The dependence of the 1H NMR chemical shifts (for acetone-d 6 or nitrobenzene-d 5 solutions at 296 K) and UV−vis spectra (in THF or nitrobenzene at 296 K) on the concentration and of the UV−vis spectra on the temperature (from 323 to 153 K) indicates that two different aggregation processes are present, having well differentiated interaction energies. Although the latter were not quantitatively evaluated, the experimental results indicate that the interaction energy of the process occurring at low concentration (responsible for the dimer formation) is much larger than that relative to the formation of higher aggregates. As a confirmation, ESI- and FAB-mass results show the presence of peaks related to the fragmentation of the dimeric species containing four palladium atoms, indicating that such a dimer has remarkable stability.