Chikao Yokokawa

Low temperature catalytic graphitization of hard carbon

Abstract Artificial resins producing non-graphitizing carbons such as divinyl benzene polymer and condensates of furfuryl alcohol or furfural, were heat treated at temperatures between 1400 and 2300°C with an addition of various kinds of metallic compounds. Using X-ray diffraction it was found that carbons thus obtained were highly graphitized. The catalytic graphitization starts at temperatures between 1400 and 1500°C and is accompanied by an appearance and disappearance of several unidentified diffraction peaks, which may originate from some kind of intermediate complexes of carbon and metals.

A kinetic study of catalytic graphitization of hard carbon

Abstract The course of catalytic graphitization of hard carbon was studied kinetically. Carbons produced at 800°C from divinyl benzene polymer, Amberlite IRC-50 and furfural-furan resins with added cupric oxide were heat treated at temperatures between 1450 and 1525°C for 30–180 min. Graphitization proceeded abruptly up to a certain degree ( d = 3.36~.37 A ) and the amount of highly graphitized material gradually increased according to the first order rate equation. Amberlite IRC-50 carbon was most easily graphitized, while divinyl benzene and furfural-furan carbons correspondingly increased in their resistance to graphitization. The energy of activation of the processes for Amberlite IRC-50 and divinyl benzene polymer was approximately 100 kcal per mole and that for furfural-furan resin somewhat higher. It was assumed that copper cleaved the cross-linking carbon-carbon bonds to accelerate graphitization.

A Physico-chemical Aspect of Coals

Review and digest of the preceeding literatures were made in order to demonstrate a physico-chemical aspect of coals.Appearent density, porosity and specific surface area were considered at a stand point of the way of constructing the coal matrix. True density, reflectance and hardness were regarded, in a connection with their ultimate composition, as functions reflecting the chemical structure of coal molecule. Thermo-plasticity were discussed with solvent-extraction experiments and with chemical constitution for a general understanding of the caking property of coal.Chemical reactions such as oxidation, pyrolysis, hydrogenolysis and depolymerization were outlined and specific behaviours of various coals of different ranks were discussed.

Chemical Structure and Properties of Heat Treated Coal in the Early State of Carbonization (XI)

Seventeen kinds of vitrains in different ranks were heated at 140°C for three hours in ethylene diamine, in pyridine and in cyclohexanone and the variation of ESR absorption spectra were examined. Spin concentration for individual coals de-creased considerably excepting the case of a brown coal, and the degree of the variation seemed to be closely connected with the rank of coals in the same way as that observed after immersing in solvents at room temperature (cf. This Journal 46, 903 (1967)). A part of the decrease in spin concentration was irreversible and still remained after wash-ing the treated coal with methanol and dilute hydrochloric acid, on the contrary of the fact that the variations caused by solvents at room temperature were almost entirely reversed by the washing. It is considered that the reversible decrease is due to the spin-spin interaction and that the irreversible decrease takes place as a result of the spin-spin coupling. Such a mechanism for the irreversible decrease as that a part of spin centres abstracts hydrogen atom from the solvent molecules and the. solvent radicals thus formed recombine with each other, seems to be ruled out because the irreversible decrease caused by the different solvents shows no noticeable difference, even though the radical trapping effect of these solvents is considered to be different considerably.It was suggested by an experimental result that the narrow component of the com-posite signals observed previously originates from the fusite immingled with the vitrains.

Chemical Structure and Properties of Heat Treated Coal in the Early State of Carbonization (IX)

Seventeen kinds of vitrains in different ranks were immersed in ethylene diamine at room temperature and variation of ESR absorption spectra was examined. Absorption intensity increases in the cases of brown coals and anthracite while it decreases in the cases of bituminous coals. Degree of the variation seemed to be in close connection with the rank of coals. It was also observed that in ethylene diamine the line width at half height and the peak-to-peak line width were smaller and that saturation took place more easily than in air or in vacuum. The variations of ESR spectra caused by ethylene diamine were reversible by wash with methanol. In ethylene diamine some kinds of bituminous coals showed a composite ESR signal and the variation of line shape was also reversible. Considering with the effects of the other solvents and reagents on ESR spectra, it is considered that the increase in intensity observed in the cases of brown coals originates from formation of semiquinone type anion radicals and that the variations for bituminos coals is explained with the assumptions that a part of localized spin centres forms a complex with ethylene diamine which has a radical masking effect and that the process is reversible.

Studies on the Oxidative Degradation of Coal (VIII)

大ノ浦炭 (C.81.5%) と中郷炭 (C.72.0%) を400-1, 000℃で熱分解し, 得られたコークスをlNHNO3の沸点で酸化した。酸化状況をさぎに明らかにした各種石炭の酸化状況と比較して熱分解過程における石炭あるいはコークスの化学構造の変化を論じた。400℃コークスはその酸化状況から判断すると石炭の化学構造上の特徴を保持しており, 熱分解が不十分な状況にあると考えられるが, 400℃までに熱分解する部分は, その組成から考えて, 石炭が希硝酸酸化で崩壊する際に小分子量物質となる部分 (前報で肪環族構造と考えられることを明らかにした) と同じであるといえる。500℃ コークスの酸化状況は石炭のそれと全く異質のものであるから, 500℃までの熱分解によつて上述のような構造部分は完全に崩壊するものと判断されるが, 熱分解における反応は酸化においてみられたほど選択性のよいものでなく, 石炭分子の芳香族構造部分の炭素集約的変化が併発するものである。600℃ コークスはきわめて酸化され難く, したがつて単位体の重縮合によつて反応性に乏しい炭素質になつたものと思われるが, 800℃ 以上の温度で処理したコークスは酸化されやすくなり, また, 生成するフミン酸の分子量が低下する。この際にみられるコークスの酸化性の向上ならびに酸化状況の変化は縮合芳香族環の成長に帰せられるものと判断された。

Catalytic Hydrogenation of Humic Acid in the Presence of Raney Ni, and Reduction of Humic Acid with Solution of Sodium in Liquid Ammonia

大ノ浦渥青炭を1N HNO3の沸点で5hrs酸化して得たフミン酸について,(1) Raney Ni存在下での水素化反応,(2) 液体アンモニア・ナトリウムを用いる還元反応を行 なった。(1) での生成物について化学分析, 赤外線吸収スペクトルの測定を行ない, 反応温度170℃ 以下では官能基において水素化反応が起こり, 250℃ 以上では人造石炭化過程に類似の反応が起こることを認めた。また反応過程の検討から, さきに示した大ノ浦フミ酸の示性式はほぼ妥当なものであると考えられた。(2) では反応生成物のOH基の増量を測定することによって大ノ浦フミン酸には分子量604につき0.9原子のエーテル型酸素が含まれていることを示した。