Kenjiro Takeshita

Carbonization of aromatic hydrocarbons—IV: Reaction path of carbonization catalyzed by alkali metals

Abstract The carbonization path of aromatic hydrocarbons catalyzed by alkali metals has been investigated to elucidate how aromatic hydrocarbons were converted into the isotropic coke, compared to the same reaction catalyzed by aluminum chloride which gave the anisotropic needle-like coke. Attempts were made to identify the intermediate products by means of elemental analyses, NMR, and mass spectroscopy, and the process was followed by the analysis of evolved gases. Effects of the catalyst migration at the intermediate step of carbonization on the properties of produced coke were also investigated to know when the destiny of the coke was determined. These results indicate that the isotropic nature of the coke obtained from the aromatic hydrocarbons with alkali metals is due to the extensive dehydrogenation of the intermediate at the early stage of carbonization at ca. 250°C. The dehydrogenation may raise the melting point of the carbonizing material. Other factors influencing the nature of the coke are considered to be unimportant in the present case.

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.

Solvolytic liquefaction of coals with a series of solvents

Abstract Solvolytic liquefaction of coals of different rank was studied with a variety of solvents at 370–390 °C under nitrogen in order to elucidate the role of solvent in coal liquefaction of this kind and to find a suitable solvent for the highest yields of liquefaction. The yield was found to depend strongly upon the nature of the coal as well as the solvent under these conditions. Pyrene and a SRC-BS pitch were excellent solvents for Miike coal, which was fusible with high fluidity at these temperatures. However, the former was less efficient for Itmann and Taiheiyō coals which were fusible at a higher temperature and non-fusible, respectively. The mechanism of solvolytic liquefaction is discussed, including nature of coal and solvent at reaction temperatures, in order to understand the properties required for high yields with non-fusible coals in solvolytic liquefaction. It is found that for liquefaction with a high yield if the coal is non-fusible, solvolytic reaction should take place between solvent and coal, so giving a liquid phase of low viscosity at the reaction temperature. The solvolytic reaction may be one of hydrogen transfer when SRC-BS is used as the solvent.

Selective synthesis of dimethylamine (DMA) from methanol and ammonia over zeolites

Abstract The selective production of dimethylamine (DMA) from methanol and ammonia was studied over some zeolites and metal oxides at a temperature range of 300 ~ 450 °C under ambient pressures. Proton or alkali-earth ion-exchanged zeolons were found to show considerable selectivity around 50% (product mole base) at 400 °C. The selectivity for the sum of DMA and monomethylamine (MMA) which can be recycled again for DMA production was over 85% at the conversion level of 90%, indicating effective suppression of trimethylamine (TMA) formation over the zeolite. The selectivity is discussed in terms of the type, strength, and steric environment of the acidic active sites. The activation of ammonia, desorption of DMA, and the shape selective discrimination of the pore structure for TMA can be factors for the selectivity.

Carbonization of aromatic hydrocarbons—III: Carbonization catalyzed by alkali metals☆

Carbonization of aromatic hydrocarbons catalyzed by alkali metals has been studied to determine what sort of cokes will be formed. Hydrocarbons studied in the present paper were in every case carbonized into isotropic carbons at high yields, regardless of the kind of alkali metals, starting materials, and the heating rate. The carbon obtained may be compared to the glassy carbon among various isotropic carbons in the sense of its crystallite size, surface area and specific gravity, but completely differed from the carbon obtained from the same source by the aid of AlCl3. Comparing these two carbonization processes promoted by different catalysts, the isotropic nature of carbons obtained by alkali metals is assumed to be due to the extensive dehydrogenation of the intermediate accelerated by the catalyst. Carbonization in solvents have been also studied to observe the effect of complete complex formation on the properties of the carbon.

Structure of anisotropic spheres obtained in the course of needle coke formation

Abstract Three kinds of spheres obtained from the heat-treated pitches which gave needle-like cokes were examined by means of an X-ray diffractometer (Diamonds method), an electron microscope and a magnetic balance to get their structural information. The precise chemical analyses were also obtained for spheres solubilized by the method of reductive alkylation. The planar condensed-ring compounds of relatively small size (6 ~ 15 A) were revealed to align with preferred orientation to form the anisotropic sphere by these instrumental analyses. The molecular weight measurement showed that the sphere contained the molecules of molecular weight distributed from 400 to 3000 or more, and that the average molecular weight remained constant through the stages of their appearance, growth and initial coalescence in spite of the enlargement of the anisotropic domains. These results indicated that the smaller molecules are anchored to the larger ones by the π-π van der Waals forces to form the insoluble sphere. It can be also assumed that the growth of the spheres is not attained by their coalescence but by incorporation of smaller molecules in the matrix into the sphere at an adequate rate to increase their diameter as large as possible for the formation of a needle-like coke. The structural model of the sphere component was tried to be described by the chemical terms based on the results.

Catalytic graphitization of non-graphitizable carbon by chromium and manganese oxides

Abstract Carbon prepared from the benzene-insoluble fraction of a solvent refined coal (non-fusible), an active carbon, a charcoal and PAN carbon fibres have been heat-treated with oxides of chromium, manganese, molybdenum and vanadium to investigate catalytic graphitization in the temperature range 1673–2773 K. Resultant materials were examined by X-ray diffraction, SEM and phase contrast high resolution electron microscopy. The chromia is an effective catalyst at 2273 K at concentration of chromium of 30%, no changes being observed at higher temperatures. With other oxides the extent of catalytic graphitization (using Lc) increased with HTT to 2773 K, values of C0 being less sensitive to HTT. Soak times are important, equilibration taking 2 hr at 2073 K (SRC-BI: Cr2O3) and 10 hr at 1673 K (SRC-BI; MnO2). Large concentrations of additives (up to 30% of metal) are required. The microscopy reveals the development of flaky graphite (SRC-BI) and the layered stacking arrangements of graphite planes in the SRC-BI graphites.

Comparative study of the chemical structure of the disk-like components in the quinoline insolubles

Abstract The structural features of the disk-like components in the anisotropic spheres from KP pitch were investigated by molecular weight measurement, NMR and IR spectroscopy, analyses of evolved gases during heat-treatment, and reactivities with phenol. A comparison was made with the corresponding properties of the Isotropic quinoline insoluble matter in the pitch. FT-IR spectra of KP spheres and KPQI indicate the presence of aliphatic C-H bonds, in addition to aromatic bonds in these materials. The ratios of aliphatic/aromatic hydrogen obtained by H-NMR, and evolved ethane analyses after the reductive ethylation, were larger in both cases than the value calculated by assuming that all hydrogens in the original material were aromatic, although it was rather difficult to identify the aliphatic hydrogen in further detail by these methods. By the reaction with phenol in the presence of PTS, one-half of KP sphere-EtBS was made insoluble in benzene. The average molecular weight of the soluble fraction obtained by this treatment was 840, which was nearly equal to that before treatment. The structural features of the disk-like components in the spheres are summarized as follows. 1. (1), The size of aromatic units is distributed over a wider range than the QI from original pitch. The smaller molecules (MW 400) as well as the larger ones (MW 3000) are the main components. 2. (2), The average molecular weight of the spheres is about one-half that of the QI. 3. (3), The major aliphatic hydrogens are located in side chains and the minor ones in methylene bridges. 4. (4), The differences in molecules are aggregated in a nematic regularity. The difference in properties of these two quinoline insolubles, as far as carbonization and graphitization are concerned, are attributable to their structural differences.

Carbonization of pitch: Compatibility of components in carbonization

Abstract The carbonization of four kinds of solvent-refined-coal (SRC) pitches was investigated in order to determine the properties required for the formation of needle coke. Although the pitches were free from Ql materials, two of them gave needle cokes, whereas the other two gave mosaic cokes. The BS fractions of all pitches formed needle cokes, and all Bl fractions were infusible and isotropic. A combination of suitable BS and Bl fractions gave a needle coke, whereas another mixture formed a mosaic coke, indicating that the BS and the Bl fractions can be compatible to yield a needle coke. Cocarbonization of the BS fractions from other pitch sources with the Bl from the SRC pitches was further studied to evaluate the compatibility, which has been discussed from the structural viewpoint. Trials to improve the properties were proposed, based on the structural information.

Carbonization of aromatic hydrocarbons—VI: Carbonization of heterocyclic compounds catalyzed by aluminum chloride

Abstract Carbonization properties of heterocyclic compounds were studied in the presence of aluminum chloride to observe the effects of carbonization reactivity difference due to the kinds of heteroatoms and the ring structures on the structural properties of the carbon. The amount of catalyst was shown to have a significant influence on the properties of cokes. Some of the heterocyclic compounds gave graphitizable needle cokes with a suitable amount of the catalyst, some gave graphitizable mosaic cokes and the others gave non-graphitizable isotropic cokes. The tendency to give a graphitizable needle coke decreased in the order of sulfur, nitrogen and oxygen as for the heteroatom, and did in fluorene, anthracene and phenanthrene types as for the ring structure. Such a tendency is compared with that observed in carbonization under high pressure. A large part of sulfur and nitrogen atoms was left in the coke after carbonization, and no correlation was observed between the remaining amount and the structure of the coke.