Proceedings
of the Tomsk Polytechnic Institute, awarded the Order of the October Revolution and the Order of the Red Banner of Labor
named after S. M. Kirov

Vol. 198　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　1974

ON THE METHODOLOGY FOR ANALYZING TECHNICAL PHENANTHRENE AND PREPARING IT FOR OZONATION

V. P. SHABROV, A. G. PECHENKIN, V. D. VOLKOVA

(Presented by the Scientific-Methodological Seminar of the Faculty of Chemical Technology)

In studying the process of ozonation of technical phenanthrene, it is necessary to know the phenanthrene content in the initial raw material in order to calculate the yield of reaction products; and, if the contents of anthracene and carbazole are also known, it is possible to calculate the duration of the ozonation process. Chromatographic and spectral methods for analyzing pure and technical phenanthrene have been described [1, 2].

The known chemical methods are based on the analytical procedure proposed by Khmelevskii and Levin, according to which phenanthrene is oxidized with iodic anhydride in glacial acetic acid, followed by conversion of the resulting phenanthrenequinone, by treatment with o-phenylenediamine, into phenanthrophenazine [3].

Noting the low accuracy of the results of analyses carried out by the Khmelevskii and Levin method (the error of the analytical results is 10–40% relative), a number of authors propose removing impurities by formaldehyde treatment of the sample under examination [4, 5].

Working by the Khmelevskii and Levin method, we established that oxidation of phenanthrene to phenanthrenequinone proceeds almost quantitatively even in the presence of impurities that usually accompany phenanthrene, if glacial acetic acid is replaced by an 80% aqueous solution of it. This increases the yield of phenanthrenequinone at the oxidation stage from 86.5% to 98–99% and at the same time makes it possible to reduce the oxidation time from 2.5 to 1.5 hours.

This improved method of analysis enabled us successfully to monitor the entire process of preparing technical phenanthrene for ozonation.

During ozonation of technical phenanthrene in methanol, the anthracene contained in the product is oxidized to anthraquinone and partially precipitates together with dimethoxy peroxide, where its content reaches 1.5%. Upon acid cleavage of the dimethoxy peroxide, all the anthraquinone is isolated together with diphenyl aldehyde. In this case, the anthraquinone can be eliminated either by purifying the diphenyl aldehyde or by removing anthracene from the technical phenanthrene subjected to ozonation.

It is usually recommended that anthracene be removed from technical phenanthrene by treating it with maleic anhydride, with prior sulfuric-acid washing [6, 7]. In studying the preparation of technical phenanthrene for ozonation, we showed that two

the final operations, i.e., sulfuric-acid washing and treatment with maleic anhydride, are most conveniently carried out in a single stage, but with the order of reagent charging changed; this ensures complete removal of all ozonizable impurities in technical phenanthrene.

Experimental Part

I. Procedure for Carrying Out the Analysis for Phenanthrene

A sample in an amount of 0.3–0.4 g is placed in a 500 ml round-bottom flask, 40 ml of a 75% aqueous solution of acetic acid is added, and 1.2 g of iodobenzene anhydride is introduced, after which the contents of the flask are kept at boiling with a reflux condenser for 1.5 hours. The mixture is then cooled to 35–40°C, 25 ml of a saturated sodium bisulfite solution is added, and it is thoroughly mixed. After a 5-minute standing period, 100 ml of water is added and the mixture is filtered through a paper filter with a thin layer of asbestos, using a further 100 ml of water to wash the flask and the filter. The filtrate is quantitatively transferred to a 500 ml flask and, after adding 0.8 g of orthophenylenediamine dihydrochloride, is boiled for 20–25 min, then cooled and filtered through a weighed glass filter No. 2–3; the flask and precipitate are washed with 50 ml of water, and then the filter is dried to constant weight at 120°C.

The phenanthrene content is calculated by the formula:

\[ \phi = 65 \frac{A}{B}, \]

where \(\phi\) is the percentage content of phenanthrene in the sample;
\(A\) is the weight of the precipitate on the filter, in g;
\(B\) is the weight of the test sample, in g;
65 is a calculated factor obtained from stoichiometry, taking into account a 98% yield of phenanthrophenazine.

Data on the composition and results of the analysis of artificial mixtures are presented in the table.

Table

II. Preparation of Technical Phenanthrene for Ozonation

The preparation of the raw material for ozonation, using a phenanthrene fraction containing 70–71% phenanthrene, 8.3% anthracene, and 8–10% carbazole, was carried out by us as follows:

To 1 kg of the molten phenanthrene fraction, 50 g of maleic anhydride was added and the mixture was kept at 130°C for 1 hour; the mass was then cooled to 90–95°C, and at this temperature 200 g of 90% sulfuric acid was gradually added, and the mixture was held with stirring for 40 min. After separation, the phenanthrene was separated from the sulf-

mass, washed with water, and then washed at 95°C with 250 ml of a 20% solution of NaOH (KOH) and subjected to simple distillation. To ensure a smooth rise in temperature during distillation, 5% by weight of xylene was first added to the phenanthrene, which eliminates the possibility of plug formation from crystallized product.

During distillation in the range 320–335°C, an 84% phenanthrene fraction was collected with a yield of 75% by weight; it contained 89% of the phenanthrene resources present in the initial raw material. Analysis of all the products obtained was carried out by the method described above. In the technical phenanthrene obtained, anthracene and carbazole are practically absent.

A single recrystallization of it from ethyl alcohol in a ratio of 1 : 4, or from methanol in a ratio of 1 : 10, gives 92% phenanthrene, which contains 66% of the phenanthrene resources in the fraction taken for purification.

The use in ozonation of 84% technical phenanthrene obtained by the method described above ensures the production of very pure dimethoxy peroxide.

Conclusions

1. A simplified procedure for the chemical method of analyzing technical phenanthrene has been proposed.

2. Conditions have been developed for the quantitative removal of ozonizable impurities from technical phenanthrene.

Literature

1. H. D. Sauerland. Brennstoff-Chem., 45, 2, 27, 1964.

2. V. I. Butakova, N. D. Rusyanova. Chemical Products of Coking of Coals of the Eastern USSR, issue 3, 309–314, 1965.

3. V. I. Khmelevskii, I. S. Levin. Organic Chemical Industry, 7, 4–5, 241, 1940.

4. L. Blom, W. J. Vranken. Analyt. Chem., 26, 2, 404, 1954.

5. V. M. Bednov, E. A. Sukhorukova, V. N. Novikov. Coke and Chemistry, No. 2, 39, 1964.

6. L. D. Gluzman. Coke and Chemistry, No. 2, 39, 1959.

7. V. M. Bednov, V. E. Privatov, M. V. Yushkova. Chemical Products of Coking of Coals of the Eastern USSR, issue 3, 119–126, 1965.