Ryohei Takahashi

Carbonization of pitches—IV: Carbonization of polycyclic aromatic hydrocarbons under the presence of aluminum chloride catalyst

Abstract Using aluminum chloride as a catalyst, polycyclic aromatic hydrocarbons were converted into carbons of two different structures, although at the early stage all carbonization processes proceeded via molten phase. The structures were examined with an optical microscope under crossed nicois. The first type of structure was a flow pattern with large oriented needle like domains observed for carbons obtained from naphthalene, chrysene, and anthracene, whereas the second one was a mosaic structure for carbon from pyrene. A significant subsequent graphitization at 2500°C (as expressed by Lc) took place for both types regardless of the different size of oriented domains. The orientation of domains depends on the rate of carbonization controlled by the holding temperature, time and quantity of the catalyst. Appropriate conditions of carbonization suppressing too fast generation of nuclei so as to permit the formation of ordered arrangement of condensed molecules were found to yield a needle-like coke also from pyrene, thus showing that the passing through a molten phase is not a sufficient condition for formation of a needle-like structure.

Modifying carbonization properties of pitches. 1. Conversion of benzene-insoluble matter of coal-tar pitch into graphitizable carbon

Abstract Reactivities of benzene-insoluble/quinoline-soluble matter (QS—BI) and quinoline insolubles (QI) of coal-tar pitch in reductive alkylation and hydrogenation with the aid of alkali metals were investigated, to obtain basic information on the possibility of changing their graphitizability and the orientation of their cokes. Alkylation increased the solubility in benzene of both components; however only the soluble fraction of QS—BI was fusible. In contrast, the soluble fractions produced by hydrogenation from both QS—BI and QI were fusible giving a flow-pattern structure and graphitizable carbon. Fusibility of pitches in the early stage of carbonization is discussed from the viewpoints of graphitization and orientation of cokes obtained by subsequent heat treatment.

Microscopic and chemical study of anisotropic mesophase possessing novel features

Abstract Anisotropic mesophase possessing novel features obtained from acenaphthylene was studied by optical and scanning electron microscopy. Variations in refluxing temperature affected the shapes of resultant anisotropic mesophase, suggesting that growth mechanisms were influenced. Polarized-light microscopy at high magnification revealed several structural types indicating that the single mesophase unit contains two domains with quite different lamellar molecular orientations. The novel mesophase, isolated by quinoline extraction, was also examined microscopically. It possessed shapes similar to those observed in dendritic growth of some graphitic substances. The quinoline-soluble fraction associated with this novel mesophase is assumed to be a dehydrogenated linear polymer of acenaphthylene, whereas the soluble matter associated with usual mesophase spheres is assumed to be decacyclene as previously reported. The mechanism of formation of this novel mesophase during refluxing is discussed in these terms.

Relation between the fluorescence intensity of vitrinites and the fluidity of coals

Abstract A quantitative correlation between fluorescence intensity (Ī 680 ) and fluidity (MF) of vitrinites of 16 coals is studied by postulating that both intensity and maximum fluidity of a vitrinite are the sum of two independent portions related to its coal rank, common to all coals (Ī 680 R and MF R ) and in particular to an individual coal (Ī 680 S and MF S ), respectively. The former portions of both properties were correlated to the coal rank by parabolic curves, with their maxima located at a coal reflectance of 1.0%. It should be noted that the amount of inert macerals was corrected to estimate the maximum fluidity of the vitrinite. The contribution of exinite macerais is included in MF R , which varies with coal rank in a manner similar to that of vitrinite. The latter portions of the vitrinite characteristic to the individual coal were correlated approximately with each other. The coals mined in Australia, USA and Canada, and Japan provided three linear correlations. The environmental conditions for peatification in the early stage of diagenesis, which are assumed to be similar to coals in those respective regions, may commonly influence the amount of bitumen, and hence Ī 680 S and MF S regardless of their coal rank.

Carbonization Behaviors of Slightly- and Non-caking Coals.

Morphological changes and caking properties during the carbonization of eight slightly-and non-caking coals (SNCC) were studied in their single and co-carbonization with a caking coal to evaluate them as a blending component. The coals were classified according to their petrographic analyses and coking properties into four categories (1) high rank (2) low rank (3) high inert content (4) weathered.The morphological examination revealed that vitrinites of their reflectance ranging 0.58 to 2.04% Ro except for weathered ones exhibited softening whatsoever in the carbonization. The fluidity of blended coal was estimated from the amouts of vitrinite of this range and inert, allowing the estimation of coke strength.It is noted that the carbonization above 200°c developed fissures in the most grains of non-fusible vitrinites in low ranking SNCC due to large amount of volatile matter, which reduced the strength of cokes obtained by the co-carbonization. Such vitrinites should be carefully distinguished from inerts of low volatile content at their blenging.

Some Problems on Coke-strength Standing on the Coal Petrology

Quantitative prediction method of coke-strength from coal petrographic analysis of row coals has been developed in many countries and is still being improved. One method developed by N. Schapiro of the U.S. Steel Corp.is really worthy and indeed in use for the routine works. In agreement to the N. Schapiros method, we have studied the same subject using all the kinds of imported and domestic coals, and made the expedient diagram for calculation of coke-strength. It is, however, not enough for the cokes produced from the low rank coals. We reinvestigate, therefore, “Gefuge” of the screened coke under the microscope, taking the quantitative-, and qualitative relationships between reactive and inert macerals into consideration, which are considered to play definite roles on cokestrength. The results obtained may throw a light on the the problem, whether prediction of coke-strength from coal petrographical analysis is available for all cokes produced from all sorts of coals.They are summarized as follows;1) Coke-strength is primarily affected by the quantitative and qualitative relationships be tween reactive and inert macerals. The character and distribution of crystallites in cell-walls of cokes, however, have an influence indirectly upon strength of cokes.2) Shrinking crack has a tendency that occurs more easily in amorphous or microcrystalline cell-wall than in well crystallized one. The crack is of macroscopic order and occurs independently from the sort of macerals.3) Evaluation of crack-genesis is not yet established, but coupling the value with the one from coalpetrographical analysis, the prediction of coke-strength may become more accurate and usefull for the routine cokemaking work.

Fundamental Research of Coking (II)

In the previous reports, the effects of ultrasonic wave in coking procedure and its adaptability for improvement on the natures of coke were commented in detail, but several problems, with which we met in the preceding experiments, have not yet been completely resolved.In order to make clearer the effects of ultrasonic wave in coking process and to explain the problems remained unaccounted for, a series of experiments are supplementarily carried out, using starch-paste and canada-balsam as the test materials.The frequency and the introducing way of ultrasonic wave applied in the present experiment are also different from these in the last ones.From the results obtained, we come to the presumption that the alternative layers of thick and thin wall in coke may take place simultaneousely, also that the ultrasonic wave may promote the orientation of graphite-crystallite as melted coal consolidates.In this way, the effects of the ultrasonic wave in carbonization of coal become more perspicuous, but since suitable selection of its frequency or power to be applied must be decided according to the nature of coal, further experiments using different kinds of coal are needed, untill more available results are obtained.