Quinoline insolubles

The specification requirements for electrode binder pitch, eg, high C/H ratio, high coking value, and high P-resin content, effectively ruled out pitches from gasworks or low temperature tars. The cmde tar is distilled to a medium-soft pitch residue and then hardened by heating for several hours at 385—400°C. This treatment increases the toluene-insoluble content and produces only a slight increase in the quinoline-insoluble (Ql) material, the latter by the formation of mesophase. 

States or Australia. In some cases, pot stills, arranged in cascade, are still used. The more sophisticated plants employ one or more carbon steel or cast-iron vessels heated electrically and equipped with temperature controls for both the bulk Hquid and the vessel walls. Contact time is usually 6—10 h. However, modem pitches are vacuum-distilled, producing no secondary quinoline insolubles, to improve the rheological properties. 

Mesophase formation in coal-tar pitch is encouraged by a reduction of the natural quinoline-insoluble matter content, which resembles carbon black but is not optically anisotropic and is characterized by an atomic carbon hydrogen ratio of 4 1. In contrast, the atomic carbon hydrogen ratio of mesophase is about 2 1. 

The extraction yield Of the coal was determined from the concentration of residual solids in the digest and the yield of gas. The solids concentration of the digest was determined from the measurement of the solubility of the digest in quinoline. The addition of quinoline does not precipitate the dissolved coal in the digest and thus the yield of quinoline insolubles can be directly equated to the concentration of solids in the digest (12). 

Coal-tar pitches generally soften around 110°C, are about 70 wt% soluble in toluene and 12 wt% insoluble in quinoline. Excessive amounts of primary quinoline insolubles (QI) would contribute to increased carbon yield, but such a pitch may not wet coke well and could hinder the penetration of pitch mto the coke voids. 

Figure 8. Boundaries of mosaic units in semicoke as re vealed by quinoline-insoluble material X 189...

Figure 9. Ultrathin section of sphere. The irregularities around much of the margin are caused by quinoline insoluble particles. Where the edge of the sphere can be seen it is quite sharp. X 5508...

Philip L. Walker, Jr. Dr. Taylor has been describing results for the carbonization of a coal tar pitch which was very low in quinoline insolubles (QI). In this case the mosaic unit which he finds in the cokes is quite large. I am wondering if he has looked at pitches of a higher QI content and if the mosaic size in the cokes decreases with increasing QI content in the original pitch ... 

G. H. Taylor Yes. We have looked at pitches with varying amounts of quinoline insolubles and find that the mosaic size is limited by these insolubles. Within limits, the higher the QI content, the smaller the mosaic size. 

The optical texture of mesophase and resultant carbons is observed readily by means of a reflected polarized light microscope and may be classified according to the shape and size of the isochromatic units. Such a classification is useful to evaluate the properties of mesophase and carbons such as needle cokes. The mesophase has been defined as the intermediate state which shows optical anisotropy and is quinoline-insoluble at room temperature (5,51) (liquid crystal glass), although it is a viscous liquid crystal during the carbonization process (6). ... 

A number of important process parameters were investigated to find out their effect on pitch characteristics and yield of the toluene and quinoline insolubles. The pitches produced were characterized by solvent analysis, NMR, thermal, and elemental analysis. Insolubles in toluene, pyridine and quinoline were used because these fractions represent the fusable and infusable anisotropic liquid crystal fraction formed in the pitch. 

Aromatic pitches were produced by treating CCB-distillate at 400°C, 410°C, 420°C, 430°C, and 440°C. We found that process temperature is a very important parameter in determining the rate of toluene and pyridine insoluble formation. It was also found that a relatively high temperature (around 430°C) is required to produce a pitch with a high liquid crystal content. Table II gives the composition of pitches produced at 400-440°C. Figure 1 illustrates graphically, the effect of process temperature on the rate of toluene, pyridine, and quinoline insolubles formation. 

Figure 1. Effect of process temperature on the rate of toluene, pyridine, and quinoline insolubles formation.

Distillate fraction Number 4 (from Table I) was treated at 430°C for varying time (3, 4, and 5 hours). Increasing reaction time led to increasing pitch yield and the rate of toluene insolubles formation, but not quinoline insolubles. Table VI gives the yield and composition of pitches prepared from distillate fraction Number 4. 

In conclusion, the ash-free and asphaltene-free CCB distillate fractions provide a potential aromatic feedstock for producing highly aromatic and highly anisotropic pitches with a high toluene insolubles and low content of the high molecular weight and infusible quinoline insolubles. 

Figure 3. Effect of temperature on quinoline insolubles formation.

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