Takeshi Furuta

Optical mesophase texture and X-ray diffraction pattern of the early-stage carbonization of pitches

Abstract Low temperature carbonization of pitches was studied with polarized-light microscopic method, X-ray diffraction, solvent extraction and density measurements. The nucleation and growth of spherical bodies occur progressively with increase of residence time at a fixed temperature, until the spherical bodies eventually coalesce with each other. Fine irregular particles of insolubles in coal-tar pitch are observed in the region of boundary between spherules and matrix. They play an important role in the mesophase transformation. The typical changes of stacking height of lamellae, interlamellar spacing, weight loss, density and insolubility with residence time show nearly the same tendency at the various temperatures from 390° to 430°C. The time-temperature superposition has been successfully employed. In the master curve for coal-tar pitch reduced at 410°C, the reduced time scale extends from 10−2 to 102 hr. From the relation between the reducing factor of time translation and absolute temperature, the apparent activation energies can be estimated over the range of 35–45 kcal/mole. It seems probable that a model of the rearrangement of C—C bonding together with vaporization of low molecular substances is applicable for the growth of spherical bodies.

Electronic properties of heat treated coals

Abstract Studies of the dependence of the electronic resistivity, Hall constant, diamagnetic susceptibility and electron spin resonance in dependence on heat-treatment temperature were carried out for coal solids molded at room temperature without binder. Akabira weakly-caking coal (d.a.f. C= 83·4 percent) and Itmann strongly-coking coal (d.a.f. C = 90·2 percent) were used. Electronic properties and X-ray diagrams indicate that the Akabira coal carbon is a hard carbon (non-graphitizing carbon) and the Itmann coal carbon is a soft carbon (graphitizing carbon) respectively. The change in sign of the Hall constant is closely related with presence of a fraction showing a narrow component in the (002) diffraction line. It is suggested that changes in the Hall constant depend on changes in concentration of defects; defects are created in heat-treatment when graphitic carbon is formed as a result of breaking the cross-links due to high internal stresses.

Electron spin resonance of heattreated phenol-formaldehyde resins

Abstract Studies of the electron spin resonance in dependence on heattreatment temperature (HTT) were carried out for phenol-formaldehyde resin (PF), 3- methylphenol-formaldehyde resin (3MPF) and 3,5-dimethylphenol-formaldehyde resin (3, 5DMPF) prepared with aqueous solution of ammonia as catalyst. The peak-to-peak line width and the spin center concentration for these three kinds of resin carbons show a normal behaviour up to about 1000°C. The g-value for 3, 5DMPF is about equal to that of the free spin up to about 1400°C, above which it increases with HTT, whereas that for 3MPF and PF remains about equal to that of the free spin up to about 2600°C. The rate of change of peak-to-peak line width in the range from about 1400°C to about 2400°C increases in the order of PF, 3MPF and 3,5DMPF. This coincides with the order of the ease of graphitization, as shown by the studies of specific gravity, diamagnetic susceptibility, electrical resistance, and measurements of crystallite size L a and L c .

Mechanical and thermal properties of heat treated coals

Studies of the Brinell and Shore hardness, of the compressional and transverse mechanical strength, the dynamic Youngs modulus, the thermal expansion coefficient and of the thermal conductivity were carried out on coal carbon solids as a function of heat treatment temperature (HTT). The coal carbon compacts were made from Akabira weakly-caking coal (d.a.f. C = 83.4%) and from Itmann strongly-coking coal (d.a.f. C = 90.2%) powders by compressing them at room temperature without binder to 1000 and 2000 kg/cm2. The values of Brinell hardness, of the mechanical strength and of the dynamic Youngs modulus increase up to a maximum at HTT 1000–1200° and then decrease with increase of HTT, but the Shore hardness shows two maxima in the range from HTT 500° to HTT 3150°C. The mechanical strength of coal carbon solids is higher than the ordinary pitch-bonded carbon solids. It is believed that this is due to the rigid bonding of coal carbon particles which occurs in the carbonization process. The thermal expansion coefficient for Akabira-coal carbon solids at first decreases with the increase of HTT, shows a minimum at HTT about 1600°C and increases with HTT. The thermal conductivity for Akabira-coal carbon solids increases with increase in HTT. A good correlation between the thermal and the electrical conductivities has been found.

The effect of electric spark discharge on graphitization of carbon

Abstract The effect of electric spark discharge on graphitization of carbon was investigated using three different types of heat treated carbon such as petroleum coke, pitch-bonded petroleum coke, and Akabira coal carbon. Each cylindrical specimen of 6 mm dia. by 6 mm length was shocked by electric spark discharge between iron electrodes in an iron capsule. The capacity of condenser was 20,000 μF and the charging voltage was 680 V. The pulse duration of spark discharge recorded by synchroscope was 1–2 millisec. The change of the graphitization degree was investigated by determining the inter-layer spacing d and crystallite thickness Lc by X-ray diffraction. The interlayer spacing d of petroleum coke and pitch-bonded petroleum coke pre-heat-treated over the range from 1000° to 2800°C decreases to 3·56–3·57 A, and their crystallite thickness Lc increases to 400–1000 A as a result of the electric spark shock. It was found that the increase in degree of graphitization was more remarkable when the carbon is heat treated to lower temperature. X-ray diffraction profiles for Akabira coal carbon also showed an increase in degree of graphitization resulting from the electric spark shock

Carbon film from polyphenylene prepared by electrochemical polymerization

A carbon film was produced from polyphenylene (PP) film prepared by electrochemical polymerization of benzene to obtain a uniform and thin film. The PP film (∼10μm thick) was transformed into the carbon or graphite film without drastic changes of shape or size. The electrical conductivity of the film was remarkably enhanced by heat-treatment between 600 and 800° C, but further increase in the conductivity was not observed by treating at higher temperatures. This behaviour is considered to correlate with a poor degree of graphitization of the PP film. The carbonization and graphitization mechanisms of the film are discussed in connection with the structure of polyphenylene in the film.

Carbonization and Graphitization of Anthracene Polymers

Carbonization and graphitization behaviors of anthracene polymers were investigated to characterize the carbon products obtained. The polymers consisting of 3-4 anthracene units (Poly (9, 10-anthracene diylidene)) were synthesized by use of dehydration and polycondensation of polyphosphoric acids. The weight loss of the polymers occurs predominantly between 350-500°C and the yield of the products treated at 1000°C reaches 72-79%. It was found from the analyses of the evoluved gases and the FT-IR spectra that dehydrogenation at the terminal CH2 groups of the polymer and elimination of CO from quinone groups at the anthracene terminal take place at these temperature ranges. The carbonized product from anthrone polymer showed a fine mozaic texture although it melted at 290-300°C. This may be because the anthracene units are twisted with each other. Also, d002 spacing and La values obtained from X-ray diffraction profilesof the heat-treated polymer suggest that the graphitizability of the polymer is less enhanced even at high temperatures.

Properties of cokes from organic heavy components in coal liquid vaccum residues.

Organic heavy components from five kinds of coal liquid vacuum residues (CLVR) from the plant (0.1t/d) of NEDOL process were studied to obtain a basic information for their utilization to carbon materials. The textures of cokes from extracts of CLVR and crystallographic parameters of graphitized cokes were examined by means of a polarized-light microscope and X-ray diffractometer.Cokes from asphaltenes showed flow anisotropic textures and ones from preas-phaltenes showed mosaic textures, which increased in the anisotropic unit size of the texture with increasing rank of the raw coal. Graphitizability of asphaltenes was bet-ter than that of preasphaltenes. Graphitizability of preasphaltenes became better with higher rank of the raw coals.

Characterization of coal liquefaction residues.

Three kinds of coal liquefaction residues obtained from PDU were characterized and compared with the raw coals by proximate and ultimate analyses, solvent separation and thermo-balance equipped with a pyrolysis-gas analyser. Each residue contains 22-38% of ash and 0.69-0.86 atomic ratio H/C. When the residues were heated up to 1000°C in a stream of N2 gas, H2 gas was generated severely at about 400 and 800 for, residues S (raw coal: Wandoan (76%C)) and N (raw coal: Illinois No.6 (79%C)) and at 800 for residue K (raw coal: Morwell (65%C)).The amount of the H2 gas was 70-80% of total gas evolved. Tar contents estimated from the weight of generated gas (3-12%) and pyrolysis residue (char and ash, 17-51%) were 17, 23 and 51% for S, K and N samples, respectively. It is assumed that the difference of tar yields is due to the difference of the severity in liquefactions and of separation methods of residues rather than those of the raw coals used in the processes.

Production of Acetylene Using a New Plasma Gasifier (III)

A thermal plasma gasification of coal has an objective to obtain useful gases such as acetylene and hydrogen. Using a new 100kW plasma gasifier having three torches, quenching effect was studied. Additional hydrogen and heliumwere used as quenchants, and Akabira coal (bituminous coal) was used as a sample.The contact efficiency between coal and plasma flame was found to be fairly improved after some modifications of the reactor and the coal feeder.When methanewas used as a sample, hydrogen quench was not so effective.In the case of coal, the large amount of acetylene was decomposed in the absense of quenchants. Coke like materials were produced in the reaction zone, and reactedwith acetylene to make carbon and hydrogen in the cooling zone. Additional hydrogen quenched these materials, and prevented acetylene decomposition. Consequently, acetylene yields were considerably enhanced with hydrogen quench.The highest acetylene yield per 1kWh was 59g, which is about 1. 7 times as much as our previous results. The carbon conversion to acetylene was 14%, and the concentration of acetylene in the exit gases was 7.0% in the same operation. Thehighest carbon conversion to acetylene was 24%. In this operation, acetylene concentration was 8.8%, and acetylene yield per 1kWh was 55g.