Bitumen Conclusions

One interesting question posed by previous researchers (14,19) is why there was asphaltic bitumen deposited at the bottom of the well considering that no phase change or any substantial temperature or pressure changes had taken place. The conclusion was that the question... 

Asphaltenes are, by definition, a solubility class (8, 9, 10) that is precipitated from petroleums and bitumens by the addition of a minimum of forty volumes of the liquid hydrocarbon. In spite of this, there are still reports of asphaltenes being isolated from crude oil by much lower proportions of the precipitating medium (II), which leads to errors not only in the determination of the amount of asphaltenes in the crude oil but also in the determination of the compound type. For example, when insufficient proportions of the precipitating medium are used, resins (a fraction isolated at a later stage of the separation procedure by adsorbtion chromatography) also may appear within the asphaltene fraction by adsorbtion onto the asphaltenes from the supernatant liquid and can be released by reprecipitation in the correct manner (12). Thus, questionable isolation techniques throw serious doubt on any conclusions drawn from subsequent work done on the isolated material. 

A study of MW distribution for precipitated asphaltenes and the derivation of conclusions about bitumen or asphalt properties from it has severe limitations since this complex mixture exhibits a considerable overlap of GPC curves for all the fractions obtained in a conventional separation procedure. Similarly, the resins separated on clay and the eluted hydrocarbons exhibit overlap, as shown by Figures 5 and 6. Figure 5 demonstrates the GPC profiles of Athabasca asphaltenes (nC5) and resins (Attapulgus clay—total resin eluent)... 

To characterize the light oils more completely, NMR were obtained see Table IV). Using a combination of IR and NMR data, several conclusions can be made about the composition of bitumen and produced oils. Because IR spectra indicate that the bitumen has unde-... 

In conclusion, sterol biosynthesis in Bacteria is probably limited to a small number of taxa that either have an incomplete sterol biosynthetic pathway or lack the capacity to alkylate the side chain. Therefore, steranes ((66b)-(66e) and (69b) and (69c)) in bitumens and oils can be reliably attributed to the activity of eukaryotic organisms (contra Cavalier-Smith, 2002). Additionally, some steranes with a diagnostic alkylation pattern ((66d)-(66e), and (70)) have taxonomic value below domain level. 

The constant interest in elucidation of new possibilities to increase of the asphalt concrete pavements durability continues to persist for several decades. Such pavements are composites consisting of gravel, sand and the polymer-containing composite (bitumen) in rationally chosen ratios. According to modem notions, it is assumed that the durabihty of asphalt concrete pavements is determined by the appearance of numerous major tmnk cracks in the pavement. This conclusion is confirmed, in particular, in numerous reports (over 130), presented at a special conference devoted exclusively to the problem of cracking in pavements [2]. It was shown earlier and in reports of the conference that a certain increase in the durability of pavements can achieve by introducing into the bitumenous binder of elastomers (synthetic mbbers or cmshed technical mbber). However, very important question about a quantitative determination of the optimum size of elastomers particles introduced into the bitumen for providing of maximum durability of pavements, until recently, remained open. The theoretical solution of above problem is presented in the next section. 

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