Hisaji Matsui

Carbyne : electrochemical preparation and nanotube formation

Carbyne-like or polyyne-containing carbon was prepared by the electrochemical reduction of PTFE. By heating and electron-beam irradiation in vacuum, carbon nanotubes were formed on the surface of the prepared carbon material. Only when the carbon contains the polyyne structure, were the carbon nanotubes found to be formed. From the view of the formation mechanism, the formation route through polyyne is strongly suggested.

Hydrocracking of polycyclic aromatic compounds using zeolite catalysts: Explanation of product distribution based on a computer aided molecular design study on the interaction of zeolite and substrates

Abstract Hydrocracking of phenanthrene was conducted in a batch autoclave system using ZSM-5 (5.5 A), mordenite (7 A) and Y-type zeolite (8 A) as catalysts. The number in brackets is the size of the pore of each zeolite. Close examination of product distribution derived from hydrocracking of phenanthrene indicated that it is strongly affected by the pore size of the zeolite used. Based on the computer aided molecular design studies of each zeolite, the way of aromatic compounds accessing towards the entrance of the pore of zeolite was visualized, herewith being able to explain the characteristic distribution of the products.

Nanostructural properties of pyrolytic carbon from polyacetylene thin film

Carbonization of polyacetylene thin films was carried out by means of pyrolysis at a temperature of 800°C in a vacuum. During the pyrolysis, inadiation of an electron beam was carried out for a specimen. Nanostructural properties of the pyrolytic carbon were investigated using mainly electron microscopy. Ribbon-shaped graphite crystals in nanometer size were obtained. Effects of the electron beam irradiation on the formation of carbon crystals will be discussed.

Structural properties of carbon materials from the electrochemical reduction of fluorinated naphthalene pitch

Abstract Synthesis of carbon materials from fluorinated naphthalene pitch has been carried out by means of electrochemical reduction. Structural and morphological properties of synthesized carbons were investigated using X-ray photoelectron spectrum (XPS), Raman scattering spectrum, X-ray diffraction measurements and scanning and transmission electron microscopy (SEM and TEM). Furthermore, a change in the structure of synthesized carbons with an electron beam irradiation was examined. The synthesized carbon has a disordered structure composed of fragments of the sp2 hexagonal network, and also has lots of micro-voids. A carbyne-like structure was found only a little with the reduction of fluorinated naphthalene pitch by Raman spectra. A lot of ribbon-like graphite nanocrystal was formed by irradiation of an electron beam at a high temperature to the defluorinated carbon. Bending of a long ribbon-like crystal of graphite was often observed. Formation mechanism of graphite nanocrystals was discussed.

Structure formation of nanoribbon graphite from carbyne-like carbons

Fluorinated carbons were reduced and defluorinated by means of electrochemical reduction . A Raman spectrum of these defluorinated carbon specimens showed that they have sp bonds. An electron beam was irradiated to these carbyne-like specimens at 800°C. This irradiation was carried out in a transmission electron microscope at accelerating voltage of 300KV. Carbyne-like carbons were almost amorphous. After the irradiation of electron beam at 800°C, small graphite crystals were observed in the form of a ribbon several nanometer in wide. The formation of the nanoribbon graphites will be discussed.

Characterization of pitches by an ultrasonic method: Change in the molecular aggregation state during air-blowing

The air blowing reaction has been used to modify the chemical structure and molecular aggregation of pitches for general-purpose carbon fiber on an industrial scale. The purpose in this study is to obtain fundamental ultrasonic data so that one can monitor in situ the change in chemical structure and molecular aggregation state in air blowing reaction. For this purpose, the effects of heat-treatment, oxygen (or air), and distillation (or low pressure) on the ultrasonic properties were separately examined. It was found that the ultrasonic measurements give the temperature dispersion curve characteristic to the structure, which was quite consistent to previous studies by ESR and NMR.

Coal Flash Hydropyrolysis. Catalytic Effect of Metals Loaded by Ion-Exchange Method on Pyrolysis and Char Gasification.

Effect of Ni and Fe ions, which were loaded to Loy Yang brown coal by ion-exchange method, on flash hydropyrolysis was investigated, using a bench-scale apparatus. The steam gasification reactivity of the chars prepared from flash hydropy-rolysis of the coals were also investigated using thermo-balance.The following results were obtained.1) It was confirmed that Ni and Fe significantly increased the overall carbon con-version in hydropyrolysis of coals. At the same time, they promoted the con-version of liquids and BTX to methane, so it is important for obtaining more li-quids and BTX to select a proper reaction condition.2) The steam gasification reactivity of the chars prepared from flash hydropyroly-sis of metal loaded coal were remarkbly higher than that of the chars prepared from the original coal.

Rapid Hydropyrolysis of Coal and Characterization of Derived Oil.

In order to characterize the oil derived from rapid hydropyrolysis of coal, Australian Loy Yang brown coal was pyrolyzed, using a bench-scale reactor of entrained flow type, at temperature of 700-950°C, hydrogen gas at 7MPa and residence time 6 to 7s. The products derived were hydrocarbon gases, CO, CO2, BTX, oil and char. The oil was distilled into 3 fractions (Fractions 1, 2 and 3 with the boiling points in the ranges of 400°C, respectively) and the composition of each fraction was analyzed. Fraction 2, a main component of the oil, thought to be compositional changeable intermediates generated during the process of the reaction, was further separated into saturates, aromatics and polars using HPLC, followed by analytical technique of FIMS and capillary gas chromatography, to study the composition of oil in detail.Reaction temperature in the range of 750-870°C, has a significant effect on both the yield and the composition of the oil. When the temperature is increased above 700°C, hydrocarbon gases and light oil, containing primary pyrolysis products, with short alkyl side-chains and many sorts of functional groups, remarkably increased in the yield, attributed to extensive thermal cracking of C-C bonds, etc., of polymeric units in coal, and the stabilization of light pyrolysis fragments by molecular hydrogen. This initial reaction almost ended at around 750°C Secondary reactions by hydrogenation became more pronounced, as temperature rose from 725 to 870°C. The yield of oil was influenced by the formation and decomposition rate of the oil, and the maximum yield was observed at around 750-800°C. The bonds of alkyl side-chains, hydroxyl group and N compounds, etc., were continuously broken up and a number of components contained in the oil decreased significantly. At 825°C, the content of unsubstituted aromatic compounds, such as naphthalene, phenanthrene, etc. in Fraction 2, exceeded 90%. At above 825°C, the decomposition of aromatic rings became the dominant reaction, causing sharp drop in the yield of oil and an increase in the yields of BTX and methane. Yield of BTX reached maximum at 870°C and then rapidly decreased with further rise in temperature, and at above 950°C, other aromatic compounds were not found.