There are many investigations on the synthesis of ketene by the thermal decomposition of acetone, but the usual studies based on reaction velocities are made mostly at relatively low temperature of below 550°c and no reference is available for these carried at 650-750°c of industrial advantage. It was necessary to carry experimental studies for finding necessary data for designing of an apparatus to be used in industrial scale. This experiment deals with the first report of this series on experiment with low temperature range. It was shown that the reaction at low temperature range was very complicated, low yield of ketene and entirely different from the reaction at high temperature range. Necessary thermodynamical consideration and the method of analysis was also descrided in this report.
The preceeding experiment showed an impossibility of determination of the velocity of thermal decomposition of acetone and ketene by the static method. Therefore, the thermal decomposition reaction of acetone with addition of a small amount of carbon disulfide was carried out by passing through two kinds of chromium nickel steel (25: 20) reaction tubes with internal diameters 25 mm. and 4 mm. It was discovered that the rate of reaciton of acetone was equal to rate of formation of methane, square of the rate of methane formation was equal to rate of formation of carbon monoxide, and the value obtained by substracting the rate of formation of carbon monoxide from the rate of formation of methane, and the rate of formation of ketene. respectively, was approximately equal. The result indicated that acetone was decomposed into ketene and methane without dehydrogenating reaction, and the ketene was further decomposed into carbon monoxide and other substances. An apparent thermal decomposition of acetone is the first order reaction. The total activation energy for thermal decomposition of acetone was 63 kcal/mole. The velocity constant of thermal decomposition of ketene was twice as much greater than that of acetone and it was assumed that the total activation energy the same as that of acetone, if it was assumed that the themal decompsition of ketene was the first order. There was mutual quantitative relation in the formed gases and the determination of either of methane or carbon monoxide in waste gas gives an information on the rate of reaction of acetone and the yield of ketene.
In order to clarify the effect of addition of carbon disulfide to acetone for the thermal decomposition of acetone into methane and ketene, and the thermal decomposition of ketene, thermal decomposition was carried out by the current method of heating at 650-750°c with addition of 0-0.5% carbon disulfide to acetone. Although acetone was completely decomposed into methane and ketene without dehydrogenation reaction even with no addition of disulfide but carbonization of ketene was accompanied in this case. The formation of ethylene and ethane was very small and that of hydrogen was high. In this case, the yield of ketene was much influenced by the temperature and the lower the temperature less was the yield. The carbonization decomposition of ketene could be suppressed by the addition of carbon disulfide, above 0.05 vol% of which was not depended on the amount of addition. By setting the general decomposition reaction of ketene is the first order reaction, the decomposition reaction constant of ketene without the presence of carbon disulfide was 2-4 times greater than the case of its addition and its activation energy became approximately to 1/2.
The thermal decomposition reaction of acetone by addition of a small amoumt of carbon disulfide and the order of reaction for thermal decomposition reaction of ketene thus formed have been investigated in detail. Also, the thermal decomposition reaction of acetone was carried out in the current of nitrogen in order to increase the yield of ketene. The result indicated that the rate of formation of ethylene, ethane, as well as ketene was increased than in the case of addition of no nitrogen and this indicated that the decomposition reaction of ketene was effected by the dilution with nitrogen. Further thermodynamical investigations on the thermal decomposition reaction of acetone and ketene have been made and it was confirmed that the thermal decomposition reaction of acetone was the first order reaction and the experimental results can be explained well by supposing the thermal decomposition reaction of ketene is 1.5th order.
Reaction of melamine and hydrochloride of aniline, o-, m-, and p-toluidine, p-chloroaniline, and p-aminobiphenyl, respectively, in the molar ratio of 1: 4 by fusion for 90 min s. at 250°c was able to synthesize comparatively pure tri-arylmelamines with over 90% of yield. In case of β-naphthylamine hydrochloride, this substance itself underwent thermal decomposition to give di-β-naphthylamine and the yield of tri-β-naphthylmelamine was low for this reason. Reaction of melamine hydrochloride and aniline, m-, and p-toluidine, and p-phenetidine in the molar ratio of 1: 6 for 5 hr s. at 280°c in S a sealed tube yielded 20-30% diarylmelamine as a main product but triarylisomelamines were not obtained.
Reaction of ammeline and aromatic amine hydrochloride by fusion yielded 72% N, N'-diphenylammeline, mp 370-1°c (d) (molar ratio 1: 4, 250°c, 15 min); 32% N, N'-di-o-toluylammeline, mp 360-1°c (d) (molar ratio 1: 4, 240°c, 2 hr); 64% N, N'-di-m-toluylammeline, mp 342-3°c (d) (molar ratio 1: 5, 245°c, 15 min); 88% N, N'-di-p-toluylammeline, mp 364-5°c (d) (molar ratio 1: 4, 250°c, 20 mm). This reaction has not been known. Since N, N'-diarylureas are obtainable as by-products, these are assumed to be derived from decomposition by opening of s-triazine ring. The chemical structures of the product of this reaction were confirmed from determination of mixed mp. with N, N'-diarylammeline obtained by hydrolysis of 2, 4-bisarylamino-6-chloro-s-triazines and N, N'-diarylurea obtained by arylation of urea.
Reaction of ammelide and aniline hydrochloride in the molar ratio of 1: 4 for 2 hr S. at 190°c yielded 73% N-phenylammelide, mp 313-4°c (d), from alkalisoluble portion, and its alkali-insoluble portion yielded 10% of N, N'-diphenylurea. The structure of N-phenylammelide was confirmed by the mixed fusion with the product obtained by hydrolysis of 2-anilino-4, 6-dichloro-s-triazine. Reaction for long period of time at high temperature did not give N-phenylammelide but gave N, N'-diphenylammeline from alkali-soluble portion, together the formation of large amount of N, N'-diphenylurea, with the indication that the triazine ring in ammelide type compound is easily decomposed by opening of its ring.
N, N'-Diphenylammeline and N-phenylammeline, respectively, was refluxed for 1 hr. with phosphorus oxychloride for substitution of hydroxyl group in these compounds with chlorine and to give 2, 4-dianilino-6-chloro-s-triazine and 2-anilino-4, 6-dichloro-s-triazine with 13% and 71% yield, respectively. Triethylamine was effective as the catalyst and their yields were increased to 27% and 84%, respectively. Three kinds of monochloro-s-triazine type reactive dyes were synthesized using 2-anilino-4, 6-dichloro-s-triazine as the raw material.