Quinoline insolubles process

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.

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. 

Petroleum-based pitches are typically made from the same slurry or decant oils used to make isotropic pitches. The earliest processes for making mesophase pitches are similar to that described by McHenry (1977). They used a long heat soak (typically about 30 h at 400°C) under an inert atmosphere, while a gas sparge was used to take away volatile compounds. Such pitches might typically have a molecular weight of about 1000 Dalton, and melt at about 300°C. They would also be characterized by high quinoline insolubles. 

The liquid phase carbonization process can be categorized on the basis of the starting material alkane hydrocarbon, alkene hydrocarbon, aromatic hydrocarbon, and PAH. Consequently, the primary material for MCMBs typically contains a large amount of PAHs from coal pitch and heavy oil. Components in primary materials, such as pyridine insolubles (Pis), quinoline insolubles (QIs), and other additives, and reaction conditions affect the growth, formation, and structure of MCMBs. 

The Great Lakes Carbon process uses coal-tar pitch as the precursor pitch. In this process, the quinoline insolubles are removed by extraction with light creosote oil. The low boiling constituents are then removed by stripping in vacuum. The residue, when heat soaked between 250 and 350 " C for 20 h, produces mesophase which can be spun into fibres at 287 °C. ... 

Coal-Tar Pitch Coke. Coal-tar pitch is used to produce needle coke primarily in Japan. Processes for producing needle coke from pitch have also been developed in Germany (4). The key to producing needle coke from coal tar or coal-tar pitch is the removal of the high concentrations of infusible sohds, or material insoluble in quinoline (QI), which are present in the original tar. The QI inhibits the growth of mesophase and results in an isotropic, high CTE coke from coal-tar pitch. After removal of the QI, very anisotropic and low CTE cokes are obtained from coal-tar-based materials. 

It is my contention that the optical and physical properties and the optical structure produced during the destructive distillation or thermal decomposition of vitrinite is closely related to mode of carbonization and, in the case of pitch, is intimately related to the method of pitch preparation. For instance, a pitch may be produced from a high or low temperature tar, from a primary cooler tar, or from a flushing liquor tar. In addition, it may be air blown, thermally or chemically treated, straight distilled, or cut back, just to mention a few. Under similar carbonization conditions almost any one of these pitches will produce a coke which has certain characteristics that are related to the parent pitch. Even pitches similarly processed from the tar can differ in the content of quinoline- and benzene-insoluble material and P-resin, and can contain more than one distinct liquid phase. None of these points of difference has been discussed by Dr. Taylor or even recognized in the preparation. To interpret the structure of pitch coke divorced from a knowledge of the pitch source and/or carbonization conditions can lead to erroneous conclusions. These are pertinent data omitted by the authors. 

The formation of the mesophase by this route has the disadvantage of requiring rather long processing times. An alternative route is the solvent route [18]. Isotropic aromatic pitches contain a separable fraction which, when heated at 230-400°C, develops an optically anisotropic liquid crystal phase in <10 minutes. This mesophase has been called a neomesophase since it is highly soluble in solvents such as pyridine or quinoline, while the mesophase derived by the thermal route is insoluble. The separable fraction of isotropic pitch is insoluble in solvents like benzene, toluene, or mixtures of toluene and heptane. Thus, it can be separated by solvent extraction from isotropic or heat soaked pitches (Figure 5, b and b ). 

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