Athabasca n-C 5 -asphaltene was fractionated into occluded maltene, low and high molar mass (LMA, HMA) asphaltene, and the latter fractions were subjected to Ni 2 B reduction to cleave the sulfide C-S bonds, basic hydrolysis to cleave the ester C-O bonds, and BBr 3 treatment to cleave the ether C-O bonds. Ni 2 B reduction of asphaltenes yielded 5-18% n-pentane solubles, which were separated into saturates, aromatics, and polars, and the saturates were analyzed for biomarkers. The residual asphaltene underwent 40% desulfurization and a greater than 4-fold drop in the MW of HMA but no change in the MW of LMA. The decrease in the MW is attributed to sulfide-bound core segments in the structure of the asphaltene:+ Ni 2 B f 4[core] + 3H 2 S. This is an important structural feature of Athabasca asphaltene and is responsible for its upgradability without excessive coke formation. The biomarkers of the asphaltene fractions were also characteristically different with regard to maturity status and composition. Both fractions yielded n-alkanes, cheilanthanes, regular steranes, hopanes, and gammacerane, and the LMA also contained dicyclic terpanes and C 21 -C 25 steranes. Noteworthy was the absence of diasteranes, which are the only steranes in the maltene. In terms of the 20S/(S + R) steranes and 22S/(S + R) hopanes parameters the maturity varies as maltene > LMA > HMA. This difference is a manifestation of the thermocatalytic nature of the maturation process and the protection of the macromolecular nature of the asphaltene against contact with external reagents. Ni 2 B reduction indicates that (1) the n-alkane products arise from n-alkyl substituted thiolane/thiane and thiophene and (2) C 27 -C 30 steranes are attached to the asphaltene by one S atom, and the C 21 -C 25 steranes and terpanes by two S atoms. Basic and BBr 3 hydrolyses of HMA showed that both ester and ether linkages of n-acids and n-alcohols are present and that the esters are of recent origin, whereas the ethers were derived from the original biotic source material of the bitumen.

Relying on experimental and theoretical data available from the literature, it is shown that the conclusions derived from measurements of fluorescence decay and depolarization kinetic times as reported in a series of papers over the past decade (Ralston, et al. and references therein) are egregiously wrong. To start with, the decay time measurements were done with inappropriate instrumentation which resulted in misleading results. Misinterpretation of the results led to the mistaken conclusion that bichromophoric type molecules are absent from petroleum asphaltene and therefore the architecture of the asphaltene molecule features a single condensed cyclic core spiked with some alkyl chains, in spite of irrefutable chemical evidence to the contrary. It was further concluded that if the asphaltene core is a single condensed ring, then the fluorescence depolarization with rotational correlation time method is applicable for the molecular weight determination of asphaltene. This is definitely not so, since, regardless of any other considerations, asphaltene is a mixture of a plethora of different, unknown components, with unknown concentrations along with innumerable different, unknown and some known chromophores portraying widely different absorption coefficients, fluorescence quantum yields, and kinetic decay times. Consequently, asphaltene fluorescence is a highly complex function of the above attributes and as such it is a totally unsuitable property for its molecular weight determination. The injection of an incorrect, single condensed ring core architecture for asphaltene has caused some confusion in asphaltene chemistry that has now hopefully been settled.

Covalent structural features and the biomarker content of an immature asphaltene originating from a saline lake deposit in China have been explored in ruthenium-ions-catalyzed oxidation. This process converts aromatic-attached aliphatic appendages to their carboxylic acid derivatives, the carboxylic group representing the site of attachment to the aromatic ring. The kinds of products were similar to those found from mature crude oil asphaltenes with slightly but significantly different distributions. The main structural features identified were, in decreasing order of importance, alkenyl bridges between aromatic carbons (including aromatic condensed cyclohexanes) followed by aromatic-attached n-alkyl, isoprenoid, and α-C1−C3 branched n-alkyl side chains. The major cyclic biomarkers detected were all attached to aromatic carbons by a single C−C bond and comprised gammacerane, C27−C35 hopanes, C27−C29 regular steranes, 4-methyl steranes, C20−C23 pregnanes, C20−C24 cheilanthanes, etc., each with a specific position in the molecule as the attachment site. Additional productsas found with other asphalteneswere benzene di- through hexacarboxylic acids, useful indicators of the mode of aromatic condensation in the asphaltene.

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The compound classes and biomarker compositions of immature Jinghan crude oil asphaltenes and their potential respective source rock kerogens have been investigated by chemolysis. The C-S-, C-O-, and C arom -C-bound appendages have been liberated by Ni 2 B reduction, BBr 3 hydrolysis, and ruthenium-ions-catalyzed oxidation. Measured were the saturate, aromatic, and polar (+ asphaltene) compound classes and the homologous series of hydrocarbon biomarkers: n-alkanes, regular isoprenoids, steranes, 4-methylsteranes, hopanes, gammacerane, their monocarboxylic acid derivatives, and R,ω-di-n-alkanoic acids. The nature and distribution of the biomarkers in shallower depths reveals a good correlation between the crude oil asphaltene and the kerogen, manifesting a crude oil-source rock relationship. In deeper strata, the correlation is less convincing but there is no indication of incompatibility. The biomarker composition confirms the immaturity of this deposit, and the huge (53%) yields of C-S plus C-O bond cleavage products from the high-sulfur asphaltene set this type of asphaltene aside from mature crude oil asphaltenes. Also, the biomarker composition points to a strongly reducing, lacustrine depositional environment for this deposit.