Degradation asphaltene fractions

The open literature does not show any report on microbial conversion of metal prophyrins although degradation of asphaltenic fractions has been eluted. The technical... 

Rojas-Avelizapa, N. G. Cervantes-Gonzalez, E. Cruz-Camarillo, R., and Rojas-Avelizapa, L. I., Degradation of aromatic and asphaltenic fractions by Serratia liquefasciens and Bacillus sp. Bulletin of Environmental Contamination and Toxicology, 2002. 69(6) pp. 835-842. 

The soil contained hydrocarbon-degrading Pseudomonas, Rbodococci, Acinetobacter, Mycobacterium, and Arthrobacter. Only the isolated Mycobacterium was able to degrade the asphaltene fraction. 

When catalytic processes are employed, complex molecules (such as those that may be found in the original asphaltene fraction) or those that are formed during the process, are not sufficiently mobile. They are also too strongly adsorbed by the catalyst to be saturated by the hydrogenation component and, hence, continue to react and eventually degrade to coke. These deposits deactivate the catalyst sites and eventually interfere with the hydroprocess. 

Figure 2. Degradation products from asphaltene fractions separated by phos-...

Figure 4. Degradation products from asphaltene fractions separated by Triton-B acids I, acidic fraction from water-soluble salts acids II, acidic fraction from water-insoluble salts...

The pentane-soluble portion of asphaltene thermolyzed at 300° C has been found to contain a full complement of n-alkanes, acyclic isoprenoids, small ring saturated and small ring aromatic compounds, typical of unbiodegraded conventional crude oil (8). However, in all cases only a small fraction of the degraded asphaltene can be analyzed in this manner, and therefore the question of the size and homogeneity of the remaining hydrocarbon units remains unresolved. 

Yields of Preasphaltenes and Asphaltenes. Subbituminous coal is converted very rapidly to soluble products in tetralin at 427°C. Figure 1 shows the yields of THF-soluble but pentane-insoluble, benzene-soluble and pentane-soluble products vs. reaction time. These fractions correspond respectively to a mixture of preasphaltenes and asphaltenes, asphaltenes and oils. Of the 78% ultimate yield of THF-soluble products based on the dry coal containing 8.6% ash, 55-60% are formed within 5 to 10 min of reaction time. By 35 min of reaction time, conversion of coal to soluble products is essentially complete. In contrast to the extremely rapid process of conversion of the parent coal to preasphaltenes, the further degradation of preasphaltenes occurs only very gradually, the yield of asphaltenes increasing from 10 to only 25% over a 1-hr reaction time. 

The fractions obtained in these schemes are defined operationally or procedurally. The amount and type of asphaltenes in an asphalt are, for instance, defined by the solvent used for precipitating them. Fractional separation of asphalt does not provide well-defined chemical components. The materials separated should only be defined in terms of the particular test procedure (Fig. 15.5). However, these fractions are generated by thermal degradation or by oxidative degradation and are not considered to be naturally occurring constituents of asphalt. The test method for determining the toluene-insoluble constituents of tar and pitch (ASTM D-4072, ASTM D-4312) can be used to determine the amount of carbenes and carboids in asphalt. 

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