Both, the toluene-insoluble (A1) and toluene-soluble (A2) asphaltene fractions, isolated using the PNP method, have been characterized by elemental analysis, molecular weight (VPO, SEC, and LDMS), and NMR (1H and 13C). The most prominent results of the analysis were the differences in hydrogen aromaticity f H, high content in both fractions of hydrogen bonded to aliphatic carbons joined to aromatics (f α), and differences in carbon aromaticity f C. Thus, low f H and high f α in A1 were consistent with a single, rigid, and flat core formed by fusion of polycyclic aromatic and naphthenic units (a single and large PANU), whereas for A2, high f H and high f αwere consistent with a more flexible structure where several smaller PANU are joined by aliphatic chains. Using a MM program, models for A1 and A2 were built and the solubility parameters calculated were found in keeping with solubility difference suggesting that the above structural differences account for the solubility difference. Similar molecular weight and heteroatom content found for these fractions suggest that these play a minor or insignificant role in solubility. A dispersion mechanism of A1 by A2, relevant to solubility of asphaltene in organic solvents, is proposed.

Oxidation of eight liquid cycloalkanes and two diesel fuels has been studied by using a low pressure high voltage oxygen plasma. Naphthenes were individually oxidized to alcohols and ketones, O( 3 P) being the active species in the plasma. Tertiary C-H bonds were the most reactive. At long treatment times the main products suffered successive oxidation to produce two oxygenated groups in the same molecule. cis-Decaline was four times more reactive than transdecaline. For this two isomers and bicyclohexyl the conversions were the lowest, the yield of the tertiary carbon being between 40 and 80% of the total. Methyl-, ethyl-, and n-propylcyclohexane gave similar results. The reactivity of the two tertiary carbons of iso-propylcyclohexane amounted to c.a. 80%. This compound was the most reactive. Due to steric effects of the alkyl group, tertbutylcyclohexane showed low reactivity. Addition of 4.7-7.0 wt % of oxygen to the diesel fuels has been achieved in one-step process with the plasma.

A sample of extra-heavy Hamaca crude oil, dissolved in carbon tetrachloride, was oxidated with ozone for a few minutes. The reaction mixture was washed with a concentrated solution of HCl, neutralized with sodium carbonate, and the products were extracted from the aqueous phase. The products were characterized by using gel permeation chromatography (GPC), elemental analysis, 1 H nuclear magnetic resonance (NMR), and Fourier transformed infrared (FTIR) techniques. The results of the analyses show that the products have lower molecular weights, lower aromatic character, and higher oxygen content than the original sample. They also indicated that these products were mainly carboxylic acids, aldehydes, and/or ketones, with a higher affinity for water than for carbon tetrachloride, the organic solvent that was used. Interfacial tension γ measurements (water-toluene) performed with these products showed a linear dependence with concentration, where γ dropped from 32 to about 7.7 dinas/cm at the apparent critical Micelle concentration (cmc) (2 g/L). Larger quantities of a commercial sample of nonylphenol ethoxylated were needed for an equivalent γ drop. In another experiment the above oxidated product was mixed with 107 ORDER REPRINTS 108ESCOBAR ET AL.Furrial asphaltene in toluene, and γ measurements were performed as above and compared with the values obtained for the same experiment using the ethoxylated surfactant. In this case, the γ values for the oxidated product were higher, suggesting a better adsorption on the asphaltene colloids. These preliminary results suggest that these oxidated products could be employed as general surfactants in the oil industry.