Athabasca asphaltenes

Yang, X. Hamza, H., and Czarnecki, J., Investigation of Subfractions of Athabasca Asphaltenes and Their Role in Emulsion Stability. Energy Fuels, 2004. 18 pp. 770-777. 

Vapor pressure osmometry in pyridine at 65, 75, and 85°C and extrapolated to room temperature. Data are for Athabasca asphaltenes. 

Figure 18. Distribution by carbon number of the monocyclic sulfides in the pyrolysis oil of Athabasca asphaltene as determined by SIR-GC/MS. Peaks labelled 15 correspond to compounds having 15 carbon atoms. Each fragmentogram is normalized to the most abundant peak. The relative intensities of the m/z = 87, 101 and 115 fragmentograms are 9.1 3.1 1.0, respectively. (Reproduced with permission from Ref. 26. Copyright 1988, Alberta Oil Sands Technology and Research Authority.)...

Such a sulfur-type polymer might also be expected to lose much of the sulfur by treatment with Raney nickel (36). However, these particular (Athabasca) asphaltenes are difficult to desulfurize with Raney nickel (26) as compared with a variety of aromatic/aliphatic thioether polymers of the... 

In the context of polyhydroxy aromatic nuclei existing in Athabasca asphaltenes, it is of interest to note that pyrolysis at 800°C results in the formation of resorcinols (24) implying that such functions may indeed exist in the asphaltenes. 

Structure-Related Properties of Athabasca Asphaltenes and Resins as Indicated by Chromatographic Separation... 

Figure 2. Separation of Athabasca asphaltenes on ion exchangers A - adds (separated on A-27) B - bases (separated on A-15) vertical dashed line represents the end of solvent system described in (3)...

Table II. Separation of Athabasca Asphaltenes on Anion Exchange...

McKay s solvent sequence completely eluted the Wilmington asphaltenes but did not elute all the Athabasca asphaltene samples and had to be extended by additional solvent mixtures to obtain good sample recoveries (cf. Figure 2). For large scale preparative separations of asphaltenes, the asphaltenes were dissolved in benzene and eluted with the same solvent, omitting the cyclohexane step. This accelerated the operation, but at the same time, as expected, the percentage of the neutral fraction now increased from 20%-21% to approximately 28%-30%, in reasonable agreement with the bulk results from the cyclohexane experiments (see Table III). Table III also shows the additional solvent systems used. 

Table III. Preparative Scale Separation of Athabasca Asphaltenes on Ion Exchangers IRA-904 and A-15...

Table IV. Analyses and Element Ratios of Athabasca Asphaltene Fractions from Ion Exchangers...

Figure 3. FT-IR spectra of Athabasca asphaltene acids fractionated on A-27 ...

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)... 

For the sake of completeness a series of Athabasca asphaltene-derived bases was chromatographed using the same column system and solvent sequence for elution and compared with the bases from the resin fraction of the same bitumen. These results are shown in Figure 8. First, the highest MW fraction of the asphaltenes was the tetrahydrofuran/i-propylamine fraction (6500 by VPO). This is one of the fractions that could not be eluted from the column by benzene/methanol/i-propylamine. Apparently, tetrahydrofuran/ t-propylamine is hardly a more polar solution than benzene/methanol/ i-propylamine. In cation exchanger chromatography, the decisive component... 

Figure 8. Comparison of gel permeation chromatograms of basic fractions (A-15) of (a) Athabasca asphaltenes and (b) resins Bz - benzene MeOH = methanol iPrN - iso-propylamine nC5 - n-pentane PhMe and PS (15,000) - VR of toluene and Vo, respectively...

Figure 9. GPC of acidic fractions of Athabasca asphaltenes 50 pi, 0.05 % solution column, p-Styragel 1000 solvent, CH2Cl2...

Figure 11. GPC profiles of acid and base fractions from Athabasca asphaltenes (0.05% solution)...

Figure 14. Time study of changes in GPC profiles of the acidic Bz/MeOH fraction of Athabasca asphaltenes...

The GPC size data also were used to monitor the effect of various processes on the asphaltene molecular size distributions. Only the asphaltenes were studied in these experiments since they are the hardest to process, and they cause the most diffusion and coking problems. One of the processes studied was visbreaking, that is, noncatalytic thermal processing. Previous workers had examined the thermal decomposition of an Athabasca asphaltene... 

Lewis Acids Assisted Degradation of Athabasca Asphaltene... 

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