Coal solubility parameter

That is why logically to assume the possibility of specific interactions also during the swelling process, since the values of parameters of the coal solubility S2, which are determining accordingly to the Flory Renner s equation are differed. It depends on fact if the data for all solvents are taking into account in calculations or such calculations are performed with the exclusion of results for solvents able to be as acceptors of hydrogen bonds (amines, ketones). Different results have been obtained also under application of other methods for calculations, especially of the Van-Krevelen s method [14],... 

Table VI. x Parameters and Solubility Parameters of Extracts of Illinois No. 6 Coal...

Further evidence of the importance of the physical nature of the solvent is found in the work of Belssing and Ross (6) who correlated the coal conversion (pyridine solubles) with the Hildebrand solubility parameter, 6, which they defined as... 

Whether the vitrinite in coal is a micellar complex (Van Krevelen, 1993) or three-dimensional network (Given, 1984a) ranains to be proven, and whether solvent effectiveness can be explained entirely by solubility parameter (Van Krevelen, 1965), donor-acceptor number (SzeUga and Marzec, 1983), hydrogen bonding (Larsen et al., 1985), solvent synergism (lino et al., 1985), or other associative forces (Nishioka and Larsen, 1990) is stUl open to debate. 

The surface functionalities present within coal mean that the coals are more responsive to polar adsorbates than activated carbons without surface treatments. The liquefaction studies indicated that there exists heterogeneity of bonding within the macromolecular systems because not all of the coal could be liquefied relatively easily. Ultimately, all of the coals were solubilized when solvents of high-solubility parameters (dipole moment) were used. 

Before leaving the solubility parameter, I want to point out one use which, while not new, has perhaps not received as much attention as it deserves. I refer to the use of the solubility parameter for describing the solvent power of a dense gas, with particular reference to high-pressure gas extraction, certainly not a novel process but one which is receiving renewed attention in coal liquefaction and in food processing. 

Oele et al. (l2l) classified the solvents into five groM s with respect to their effect on coal. The three gro 5>s that are of interest in liquefaction practice are the specific solvents (e.g. pyridine), degrading solvents (e.g. anthracene), and reactive solvents (e.g. tetralin). Dryden (l22) suggested to Tise the square of the solubility parameter in correlating solvent effectiveness. The solubility parameter is a measure of the cohesive forces in a solution that has no excess entropy of mixing (l23). Silver and coworker, based on Kiebler s data (l ), found that solvents with a nonpolar solubility parameter of 9.5 (cal/c.c.) appeared to be most effective for coal dissolution (12 ). 

Authors concluded, that although the swelling degree is not directly connected with molecular characteristics of absorbed liquids, however determining factor is their parameter of solubility in spite of the fact that at detailed consideration of the dependencies Q =f(3) (or f(32)) there are a number of deviations (as same as in the work [5]) from the ideal curve for many solvents. It is necessary to notify that although it is hard to estimate the verisimilitude of determined in such a way molecular weights of structural links of a coal between the points of cross bonds, however, in a case of synthetic polymers in a same way determined masses of links visible don t agree with the values obtained in accordance with others methods. 

The swelling data in Table IV can be used to calculate x parameters for the extract and O-methylated extract using Equation 1. The results are shown in Table V. The x parameters for both extracts are observed to be positive and independent of pressure or concentration of benzene. The magnitude of the parameters are much larger than that determined for the O-octylated extract (0.65) which is consistent with their lower solubilities in liquid benzene. The X parameters are much larger than those determined by Larsen el al. for the pyridine-extracted Illinois No. 6 coal, which was near 0.3.(6) The reason for this are not clear. However, we note that benzene is a very poor solvent for these pyridine-extracts so large x parameters are expected. 

The extent to which these Flory interaction parameters apply to the pyridine-insoluble portion of the Illinois No. 6 coal is open to question. We cannot address this aspect fully here, but we have noted that the pyridine-soluble and -insoluble portions of the Illinois No. 6 coal studied here have similar carbon, hydrogen and oxygen contents. Maciel has observed that the aromaticities of the two portions of an Illinois No. 6 coal are similar as well.(12) Based on this alone, it seems that the pyridine-soluble portion is representative of the larger, crosslinked portion, at least for the Illinois No. 6 coal, but this aspect remains controversial,(12) so caution is warranted. 

Asphaltene content bears directly on the physical properties of the liquid product. Viscosity is of particular interest because of the importance of this parameter to operation of liquefaction plants and as a measure of the extent of liquefaction. The correlation between asphaltene content and the viscosity of the liquid has been a subject of a number of investigations (23-27). The logarithm of the viscosity ratio, In 7j/rj0 (where i and y0 are the viscosities of the solution and solvent, respectively) was found to be a linear function of concentration when asphaltene was redissolved in the pentane-soluble oil isolated from a coal-derived liquid (24). The slopes of these lines, termed the logarithmic viscosity numbers, are a measure of the contribution to the viscosity of a solution attributable to asphaltene. By comparison of logarithmic viscosity numbers of asphaltenes and their acidic and basic subfractions, it was determined that intermolecular association, which is especially strong between the acid and base subfractions, is responsible for a significant portion of the viscosity of these solutions. 

Asphaltenes are generally defined as those components in petroleum and coal liquids that under certain conditions are soluble in benzene but insoluble in aliphatic solvents, such as n-pentane, n-heptane, or cyclohexane. This definition obviously includes a broad variety of components, as insolubility in the above solvents can be caused by high molecular weight, high polarity, hydrogen bonding, acid-base complexing, or combinations of these parameters. 

Goldberg et al. have also measured the ESR parameters of liquefaction products of a high-volatile bituminous coal separated into oils, asphaltenes, a benzene-methanol soluble (BMS) fraction and benzene-methanol insoluble (BMI) fraction. The spin concentration N decreased in the sequence BMI > BMS > asphaltene > oil, whereas the g-value decreased in the opposite sequence, a result essentially in agreement with those of... 

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