Yukio Sakai

Chemistry of synthesis, structure, preparation and application of aromatic-derived mesophase pitch

Mesophase pitch has been synthesized from pure aromatic hydrocarbons (naphthalene, methylnaphthalene) aided by an HF–BF3 catalyst. These synthesized pitches have better performance for many applications — carbon fibers, binders, and anode materials for lithium ion batteries etc. — because the purity and high aromaticity leads to high orientation. This paper discusses the kinds of pitch, the micro- to macrostructure, some properties, reactivity, and many applications.

Preparation of mesophase pitch from aromatic hydrocarbons by the aid of HFBF3

Abstract Two procedures to prepare mesophase pitch from naphthalene using HF BF 3 , are described. The first procedure heats naphthalene at 80°C with HF BF 3 to give a naphthene rich pitch followed by either (a) heat treatment at 400–480°C under vacuum (0.1 kPa) or (b) Heat treatment at 2.1 MPa followed by vacuum treatment at 0.1 kPa. Approach (a) gives a spinnable mesophase pitch of S.P. 228°C of 98% anisotropy, 23 wt% yield, and approach (b) of 40–60 wt% yield. Stabilization in air was very slow especially with the pitch made by approach (b), taking 90–120 min or longer at 300°C. Programmed heating was effective to reduce the stabilization time. The second procedure heated naphthalene with HF BF 3 , under pressure at 260–300°C. The resultant pitches had 100% anisotropy and S.P. of 215–285°C with BS amounts of 52-12 wt% in yields of up to 60 wt%. Smoothly spun fibers were stabilized, 15–30 min at 270°C. Noncatalytic preparation produced mesophase pitch of high aromaticity: catalytic preparations maintained naphthenic hydrogen, the cause of stabilization reactivity. HF BF 3 could be removed from the pitch.

Mesophase pitches prepared from methylnaphthalene by the aid of HFBF3

Abstract Mesophase pitches were prepared from methylnaphthalenes using HF BF 3 as a catalyst to improve their spinning and stabilization properties in comparison with those from naphthalene. Methylnaphthalene-derived mesophase pitch carried a number of methyl groups in addition to naphthenic groups which were introduced by nondehydrogenative polymerization reaction of naphthalene rings. Many methyl groups in methylnaphthalene were left in the mesophase pitch to be very effective for lowering the softening point and improving the spinnability and stabilization reactivity, stabilization being achieved within 10 minutes at 270°C. It was found that the methyl group migrated between 1-and 2-positions on the naphthalene ring in the presence of super strong acid of HF BF 3 , giving the same structure and properties of mesophase pitches regardless of its positions in the starting materials. Effects of the methyl group on the reactivity and structural changes of the stabilization were discussed based on the infrared (IR) spectra.

Pitch-based carbon fiber of high compressive strength prepared from synthetic isotropic pitch containing mesophase spheres

Two pitches containing mesophase spheres were prepared from a synthetic isotropic naphthalene pitch at 360°C and 375°C so as to contain spheres of different diameters. Both pitches were smoothly spun into thin fibers, which were converted into carbon fibers through stabilization, carbonization and graphitization. The fiber from the pitch with finer spheres exhibited a higher compressive strength, which reflected smaller microdomains, smaller, and thinner fibrils, being different from both isotropic and anisotropic pitch fibers. The isotropic fraction of the pitch appears to give areas of smaller microdomains. The fiber exhibited intermediate values in graphitic parameters between those of isotropic and anisotropic pitch-based fibers.

Two Catalytic Technologies of Much Influence on Progress in Chemical Process Development in Japan

Abstract A tremendous number of new catalytic chemical processes have been established and commercialized in Japan in recent years [l, 21. Table 1 shows typical Japanese-made technologies and processes from 1957, about which time the petrochemical industry started in Japan. In those days almost all processes adopted were either fully licensed from foreign companies in Western Europe and the U.S. or completed in Japan as a practical technology using basic and original ones discovered by the foreign companies. In 18 years, from 1957 to 1974, when the Japanese petrochemical industry matured and rapidly magnified its scale, 22 new technologies and processes were accomplished in Japan; however, some of them are not intrinsically Japanese for the reason already mentioned—they derived from foreign companies—and some others were only the first in Japan but not the first in the world. The next 17 years (1975–1992), which included two oil embargoes and were regarded as the time the industry entered the age of a low...

Efficient preparation of meso-carbon microbeads from synthetic isotropic pitch derived from naphthalene

Abstract An efficient preparation of mesophase spheres was attempted from synthetic isotropic pitches of naphthalene oligomers. A large number of spheres of rather uniform diameter were obtained by the carbonization at 380 °C for 20 h. Volumetric and yields of spheres in the pitch were volumetrically measured under the optical microscope and extracted; a pyridine soluble fraction as high as 42 vol% and 15 wt%, respectively was reached. Such a difference in the yields suggests that the spheres prepared in the present study included a significant amount of the pyridine soluble fraction. The extracted sphere carried a number of pores, leaving rod-like units. Self-assembling units of pyridine insoluble fraction produced in the mesophase are suggested to be precipitated to form a spherical shape.

Preparation of mesocarbon microbeads by dispersing mesophase pitch in isotropic pitches

Abstract Mesocarbon microbeads of 1–10 μm were prepared through dispersing the synthetic mesophase pitches in synthetic isotropic pitches and successive solvent extraction. The suitable ratio of mesophase pitch/isotropic pitch, temperature and rapid agitation at dispersion were found to be key factors to obtain the high yields of tetrahydrofuran and pyridine insoluble microbeads which were 34 and 20 wt%, of the highest yield, respectively. In contrast, the combinations of coal tar derived mesophase pitch/synthetic pitch or synthetic mesophase pitch/petroleum A240 pitch failed to disperse spheres of mesophase pitch in the isotropic matrix, leaving bulk grains of mesophase pitch at the bottom of the matrix. The melt mesophase pitch of adequate viscosity is dispersed by the agitation into viscous droplets in the isotropic matrix, while the droplets stay afloat because of their similar specific gravities. The lighter component in the droplet of the mesophase pitch was extracted into the isotropic matrix while the mesophase pitch is melted, leaving spheres of smooth surface. Extraction by the solvent at a lower temperature than the softening point leaves mesocarbon microbeads isolated, removing the solvent soluble fraction.

The properties of Co-oligomerized mesophase pitch from methylnaphthalene and naphthalene catalyzed by HF/BF3

Abstract Co-oligomerized mesophase pitch from naphthalene and methylnaphthalene at mixing ratio of 7:3 by aid of HF/BF3 was studied in terms of its structure, flow behavior and stabilization reactivity as well as microstructure and mechanical properties of the resultant fiber. The molecular structure of co-oligomerized mesophase pitch was rather similar to that of naphthalene pitch because of major content and higher reactivity of naphthalene at the oligomerization, however, the pitch exhibited higher stacking height, preferred orientation and stabilization reactivity than the naphthalene pitch, which certainly reflect the methylnaphthalene units. The resultant fiber showed very high tensile strength and Youngs modulus, the former of which was much higher than those of naphthalene and methylnaphthalene pitches, while the latter was comparable to that of methylnaphthalene pitch. The high strength appeared to reflect no crack in the radial alignment of multi-bent domains in the transverse section, while the fiber from methylnaphthalene pitch carried a wide open wedge when both pitches were spun under similar conditions. Such structure of the present fiber may reflect the flow properties of the present pitch which are governed by the molecular stacking of the co-oligomerized mesogens in the liquid crystal state. The little pleats were also observed aligned irregularly on the surface of the present fiber after the graphitization, probably contributing to the high strength.

Epoxidation of ethylene over AgNaCl catalysts

Epoxidation of ethylene over sodium chloride-doped and granular sodium chloride-supported silver catalysts was performed at atmospheric pressure using conventional flow reactors. Although the stationary activity was somewhat low, each type of catalyst has shown high selectivity, 84–87%, under an ethylene-rich atmosphere. The selectivity was almost independent of reaction temperature, contact time, and catalyst composition. The total reaction rate rose exponentially with temperature until an apparent activation energy of 75.3 kJ mol−1 was obtained. Under oxygen-rich atmospheres, marked drops in activity were observed. In exposing the deactivated catalysts to a stream of hydrogen, carbon dioxide was desorbed. The strongly enhanced adsorption of carbon dioxide promoted the formation of silver chloride. Silver particles on the granular sodium chloride were homogeneously dispersed and ~200 nm in size. In addition, the crystallite size of silver was 43–50 nm, which was not altered after the reaction or even after heating at 673 K in oxygen gas. In a pulse reaction using an ethylene-rich gas mixture, acetaldehydes other than ethylene oxide were formed, and, as the catalyst surface had been oxidized by irreversible adsorption of oxygen, the formation of carbon dioxide was promoted and that of acetaldehyde decreased.

A novel silver catalyst prepared by using superheated-steam as a heating medium for ethylene oxide production

A high-performance catalyst for the production of ethylene oxide by vapor phase oxidation of ethylene was developed and commercialized. High performance was achieved by the usage of a high surface area carrier with controlled pore distribution and surface acid-base properties, by the adoption of mixed amines to dissolve heat-decomposable silver salt, by the addition of effective additives, and by the introduction of a uniquely developed heat-treatment technology using superheated-steam as the heating medium. The catalyst thus prepared showed high activities because of homogeneously and highly dispersed silver and additive elements within the carrier. As a result, the reaction temperature could be lowered, which led to the improvement of not only the selectivity but also the catalyst life. Heat treatment with superheated-steam proved to have many advantages in producing high-performance catalysts and it is commercially favorable because it needs only a very short processing time.