Adsorptive fractionation

Furby (12) has developed a method for evaluating stocks in the lubricating oil range that results in a breakdown of components into asphaltenes, resins, wax, and dewaxed oil and provides a yield-viscosity index relationship for the dewaxed oil. The author has found such analyses very useful and inexpensive for evaluating a large number of potential lubricating oil stocks. Furby s method utilizes petroleum ether to precipitate asphaltenes, a fuller s earth-petroleum ether fractionation to isolate resins, methyl ethyl ketone-benzene dewaxing on the deasphalted-deresinified material to separate wax, and an adsorption fractionation to provide cuts from which the yield-viscosity index relationship for dewaxed, solvent-refined oil is obtained. 

Separation, Characterization and Analysis of the Distillate Fractions. Results from the analyses of the <200° C coal-liquid distillates (after removal of trace quantities of acids and bases) are summarized in Table IV. Results from the dual silica-gel/alu-mina-gel adsorption chromatography separations of the 200° to 325° C, 325° to 425° C, and 425° to 540° C coal-liquid distillates are summarized in Table V. Data for the acid and base extracts of the polyaromatic-polar adsorption fractions are also included in Table V. Summary data on analysis of the saturate fractions are listed in Table VI. Data in Table VI show a trend toward higher percentages of zero- and one-ring saturates in lower-rank coals. 

If a mixture contains more than two fractions the treatment can easily be generalized. For example, a trimodal mixture gives four linear isotherm sections ). The Increasing part of fig. 5.29 is replaced by two sections of different slope in the first the lowest molecular weight is displaced from the surface, in the second the middle fraction. For a continuous distribution of molecular weights a rounded isotherm is obtained the adsorption fractionation varies smoothly with the polymer dose. 

Figure 5.30. Adsorption fractionation of a polydisperse sample as calculated from the SF model (a) and as measured by gel permeation chromatography (b))). The calculations apply to a Schultz-Flory distribution with = 2.05 ), the experiments to the...

E. L. Morton and P. W. Murrill, Analysis of Liquid Phase Adsorption Fractionation in Fixed... 

Figure 7.15 Principle of adsorption fractionation sketch of flow paths in cascade and corresponding McCabe-Thiele operating diagram for (a) the more strongly adsorbed component and (b) the less strongly adsorbed component (source Ruthven and Ching 1989).

As an alternative to the continuous countercurrent model an equilibrium stage model of the adsorptive fractionation system exists (Chinget a/. 1985). In effect the concentration ratio cl/co for each column is represented by the well-known equation (Kremser 1930, Souders and Brown 1932) ... 

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