Precipitation coal derived bases

Precipitation of Coal-Derived Bases from Toluene. A solution of coal-derived material in toluene was prepared by stirring 50 g of sample per liter of solvent at reflux temperature for 6-8 h. After cooling, suction filtration through a sintered glass funnel was used to remove the undissolved solids, which were dried in vacuo at 80° C and weighed the quantity of material dissolved was determined by difference. The filtrate was placed in a stoppered bottle and used as a stock solution for several precipitation experiments. Immediately before the use of the toluene solution, an accurately pipetted volume was evaporated to dryness in vacuo and the remaining solid was weighed to calculate the concentration. 

Table IV. Precipitation of Coal-Derived Bases with Phosphotungstic Acid...

In modern terms, asphaltene is conceptually defined as the normal-pentane-insoluble and benzene-soluble fraction whether it is derived from coal or from petroleum. The generalized concept has been extended to fractions derived from other carbonaceous sources, such as coal and oil shale (8,9). With this extension there has been much effort to define asphaltenes in terms of chemical structure and elemental analysis as well as by the carbonaceous source. It was demonstrated that the elemental compositions of asphaltene fractions precipitated by different solvents from various sources of petroleum vary considerably (see Table I). Figure 1 presents hypothetical structures for asphaltenes derived from oils produced in different regions of the world. Other investigators (10,11) based on a number of analytical methods, such as NMR, GPC, etc., have suggested the hypothetical structure shown in Figure 2. 

Fig. 17.14 Range of isotopic compositions of oxygen, carbon, and strontium of the clasts of black calcite and opaline silica from the Elephant Moraine. If the calcite precipitated from glacial meltwater at 0°C, then the water must have had a value between -47.3%o and -54.9%o (SMOW) in good agreement with the value of ice in the Elephant Moraine. The carbon in the black calcite is strongly depleted in which is characteristic of photosynthetic plants and of bituminous coal in the Beacon Supergroup. Fragments of coal occur in the Elephant Moraine which is composed of clasts derived from the base of the ice sheet. The strontium in the black calcite is strongly enriched in radiogenic Sr compared to seawater (SW) of Phanerozoic age...

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