Solubility parameter pitch

Thus, one approach to understanding the chemistry of pyrolysis of pitch leading to mesophase is not to make a complete molecular analysis but to solvent fractionate the pitch using solvents of increasing solubility parameters (58). An early study of fractionation and NMR analysis of fractions is that of Smith et al. (61). 

The establishment of relationships between molecular sizes/shape, and structure of compounds in pitches and solubilities in solvents of known solubility parameters. 

Riggs showed the solubility of a pitch in a series of solvents with increasing solubility parameters followed a bell shaped curve, with maximum solubility occurring when the solubility parameter of the solute and solvent were equal( ). In general, non-polar solvents with total solubility parameters ranging from 8.0-9.5 were desirable for extracting mesophase forming fractions from pitches. In this... 

Both examples Illustrate that solvent blends can be used to extract mesophase forming fractions from the A-240. Figure 9 suggests several other solvents may form successful blends. Solvents normally inappropriate should be blended to shift the solubility parameters of the mixture closer to the edge of the enhanced solubility region where the blend can extract a pitch fraction capable of complete coalescence. Solvent blends can also be used to moderate solvent costs without impairing solvent effectiveness. 

Results for a low MW pitch fraction, the toluene soluble/heptane insoluble (TS/HI) fraction of A 240 pitch are shown in Figure 4. The solubility parameters of pitch and solvent are reasonably well matched, and as can be seen, there is zero slope to the extrapolation line. Results for A 240 pitch, which by comparison to the TS/m fraction has an overall lower MW, but also a high MW tail, is also shown in Figure 4. At the higher temperatures of 83 C 6 122 C, there is again zero slope, but the lower temperature of 47°C has a slight positive slope, and a higher intercept. (The plot of MW vs Cw is inverted from the earlier vs C plot.) The positive slope... 

Figure 1 SCHEMATIC REPRESENTATION OF THE DISTRIBUTION OF MOLECULAR TYPES IN A TYPICAL PETROLEUM PITCH (RANKED BY SOLUBILITY PARAMETER)...

An Exxon cat cracker bottom pitch was extracted with solvents of varying solubility parameter in order to evaluate the relationships which exist between extraction conditions and the characteristics of the extracted product. The precursor pitch possessed a carbon/ hydrogen ratio of 1.49 and a alculatedO, overall average solubility parameter of 10.48 reflux quinoline insolubles content of the pitch was 2.3% and the refluxing toluene insolubles were at a level of 20.3%. The pitch was not optically anisotropic. Upon heating in N2 to 530 C in a TGA, a coke yield of 37% was obtained. 

An examination of Table 1 reveals some interesting trends. As the solubility parameter of the extraction solvent increases, the mesophase content of the extracted fraction goes to >99%. Samples 3, 4, 5 and 6 are "neomesophases"0) in that upon melting, they instantly transform to a liquid crystalline state. Their quinoline insolubles contents were less than 1%. The extraction process breaks down the micelle and removes the non-mesomorphic species in the pitch which had inhibited the coalescence of the mesophase forming species. Sample 2, the heptane extracted fraction, did not exhibit neomesophase behavior. Extended heat treatment at 400+ C was required to convert this sample to a mesomorphic state. The heptane did not remove a sufficient amount of the non-mesophase formers. 

VARIATION IN COKE YIELD OF EXTRACTION CAT CRACKER BOTTOM PITCHES AS A FUNCTION OF THE SOLUBILITY PARAMETER OF THE EXTRACTION SOLVENT... 

VARIATION IN C/H VS THE SOLVENT SOLUBILITY PARAMETER FOR VARIOUS CAT CRACKER BOTTOM PITCH FRACTIONS... 

VARIATION IN GLASS TRANSITION TEMPERATURE FOR EXTRACTED CAT CRACKER BOTTOM PITCH FRACTIONS AS A FUNCTION OF THE EXTRACTION SOLVENT SOLUBILITY PARAMETER... 

VARIATION IN CARBON FIBER MODULUS AS A FUNCTION OF CARBONIZING TEMPERATURE. PRECURSOR WAS A CAT CRACKER BOTTOM PITCH EXTRACTED WITH A SOLVENT HAVING A SOLUBILITY PARAMETER OF 8. -... 

By solvent extracting the pitch with a solvent system having a solubility parameter of 8.63 a more or less ideal fraction for carbon fiber production is obtained. Extraction with solvent systems of different solubility parameter results in uniform changes in extracted product characteristics which can be tailored to other specific carbon product applications, such as carbon/carbon matrix materials, anodes, etc. 

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