Carbonization of coals into anisotropic cokes: 6. Formed cokes of high density and optical anisotropy from non-fusible and slightly fusible coals

A procedure for the preparation of solid formed coke of enough adhesion and anisotropic development for use in the blast furnace has been studied, using non-fusible and slightly fusible coals with petroleum cocarbonizing additives. The coke precursor was prepared through the copreheat-treatment of coal and a suitable additive in adequate quantity under stipulated conditions. The desired coke was produced by carbonization after forming with a press. The conditions for the copreheat-treatment have been carefully examined in terms of the temperature, time and heating devices. The behaviour of coals during copreheat-treatment and carbonization were discussed in terms of coal ranks, comparing this behaviour to the liquefaction reactivity and thermal stability of their liquefied product.     

Co-carbonization processes of a petroleum asphalt and coal-derived liquids: An approach to co-carbonization compatibility

Mixtures of three principal carbonizing materials (Kafji vacuum asphalt (KF-VR), solvent-refined coal (SRC) and solvent-treated coal (STC)) with five additives (three Ashland petroleum pitches (A240, A200 and A170), quinoline-soluble residue of steam-cracked crude oil (KP-QS) and coal-tar pitch (CTP-ASM)) were co-carbonized and development of optical texture in the resultant cokes was assessed to evaluate the compatibility of the mixtures. CTP-ASM showed the highest compatibility for KF-VR, but failed to modify STC. By contrast, A240 modified KF-VR and STC so that flow texture developed. FT-i.r. spectra of co-carbonization intermediates from STC had absorption bands between 1100–1300 cm^?1 attributable to phenoxyl groups. These were also present in co-carbonizations with CTP-ASM, but were only just apparent in co-carbonizations with A240. Measurement of naphthenic hydrogen, defined as R_nus, during co-carbonization, was consistent with deoxygenation via hydrogen transfer. Thus, the modifying activities of A240 and CTP are differentiated by the availability of transferrable hydrogen. Mechanisms of co-carbonization are discussed.     

Structure and carbonization properties of pitches produced catalytically from aromatic hydrocarbons with

Carbonization properties of pitches synthesized from some aromatic hydrocarbons by the aid of were studied under atmospheric 1.1 and 3.1 MPa pressures. The highest coke yields obtained under atmospheric pressure and 3.1 MPa were 64% and 85%, respectively, both of which were observed with anthracene pitch. Pyrene pitch exhibited a low coke yield of 37% under atmospheric pressure, but as high as 85% under 3.1 MPa.The pitches were revealed with ¹H-NMR and FD-MS to consist essentially of oligomers of starting aromatic rings such as dimers, trimers, and tetramers. The oligomers carried significant amounts of naphthenic hydrogens, which provide their low softening point and enable the development of an anisotropic flow texture when the pitch was carbonized. The carbonization scheme is discussed in relation to the coke yield.     

Catalytic graphitization of fibrous and particulate carbons

Catalytic graphitization of carbon fibers, carbon black and anisopropic mesophase spheres by chromia and chromium compounds was studied to examine the influences of the amount of catalyst, procedures of catalyst dispersion and heating on the extent of graphitization. Catalyst addition as a liquid solution provided better dispersion than mixing of powdered catalyst with the carbons by grinding, and permitted graphitization of intact carbon fibers. However, the catalytic action caused restructuring of the fibers and the carbon black. Sequential heat treatments at temperatures < 2000°C were more effective for graphitization than higher temperature treatments in which the catalyst sublimed. In all cases the amount of graphitization increased sharply with the amount of catalyst. The mechanism of catalytic graphitization is briefly discussed.     

High yield preparation of tubular carbon nanofibers over supported Co-Mo catalysts

In the search for high yield synthesis of carbon nanotubes (CNTs) at lower temperatures, Co-Mo catalysts on carbon black were investigated with ethylene and CO as carbon sources in catalytic gas-phase pyrolysis in comparison to that on TiO₂. The carbon black support was expected to be advantageous because of the feasibility of a CNT/carbon black composite possibly fabricated for several applications without removal of the support. Depending on the catalyst support, the catalytic activity toward CO and ethylene showed great differences. Co-Mo (9:1) catalysts on titania or carbon black provided a high carbon yield from CO and ethylene at the rather low temperatures of 450-530 °C.     

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

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.     

Carbonization properties of partially hydrogenated aromatic compounds—I: Carbonization of partially hydrogenated pyrene prepared by Birch reduction

The carbonization properties of pyrene hydrogenated by Birch reduction to a variable extent were studied at 600°C under atmospheric pressure, in order to examine the influence of partial hydrogenation on the carbonization reactivity. Pyrene, which did not yield any coke, produced coke with flow texture after partial hydrogenation. Carbon yield of partially hydrogenated pyrene sharply depended on the hydrogenation extent. The intermediate stage of the carbonization pursued by hot-stage microscopy followed the steps of nucleation, growth and coalescence of anisotropic sphere. Considerable fluidity was observed at the final stage of mesophase development prior to the complete solidification where the benzene insoluble content exceeded 90%. The carbonization mechanism was discussed from the view of the polymerization of hydrogenated pyrene in relation with its structure.     

Catalytic activity of pitch-based activated carbon fiber of large surface area heat-treated at high temperature and its regeneration for NO–NH3 reaction at ambient temperatures

The catalytic activity of a pitch-based activated carbon fiber (ACF) of very large surface area (OG-20A) was studied for NO–NH₃ reaction in a flow reactor at ambient temperatures. The ACF exhibited the highest activity in wet as well as dry gas among heat-treated ACFs so far examined by the present authors. The calcination at 1100°C was essential to exhibit the highest activity especially in wet gas. Although high humidity always retarded the reaction very markedly, its retardation was very much emphasized against NO of low concentration around 10 ppm. Sufficient amount of OG-20A-H1100 (3 g) allowed complete removal of 10–200 ppm NO by reduction and adsorption for initial 6 h even at least in wet gas at 25–30°C depending on NO concentration. The removal conversion decreased gradually for several hours following to the stationary one. The reactivity of adsorbed NO and NH₃ was examined in air to regenerate the period of complete NO removal over the ACF. The regeneration at 30°C was found optimum after the removal reaction at 25 or 30°C to provide the same period of complete removal by 3 h, leaking minimum amounts of adsorbed NO and NH₃. A higher reaction temperature of 35°C shortened the period of complete NO removal, and the successive regeneration at 30°C by 3 h failed in the complete NO removal in the second run. Oxygen appears necessary to regenerate the activity through enhancing the reaction of adsorbed NO and NH₃. NH₃ in the regeneration gas appears to inhibit the reaction of adsorbed species, increasing NH₃ leak.     

Mechanism of carbonization of a semianthracite

The carbonization of a semi-anthracite which produced a domain texture of large isochromatic units was studied to elucidate the mechanism for this type of anisotropic development. The observation of a series of its carbonization residues at several temperatures indicated that the anisotropic domains appeared simultaneously and no stepwise growth was observable. However, its co-carbonization with decacyclene or A240 pitch followed the typical mesophase mechanism to give a flow or coarse-mozaic texture which was quite similar to that observed in the coke produced from its quinoline extract. In contrast, the residue after quinoline extraction retained on carbonization the same basic anisotropy as the coal. The structure of the original coal and the coke was studied by topological observation before and after quinoline and gasification etching. The results suggest that during carbonization the preordered structure of the semi-anthracite is slightly rearranged, with the aid of the quinoline-soluble matter, to become more highly ordered giving a domain texture which corresponds to the isochromatic anisotropic regions of its basic anisotropy.