SU296748A1 - METHOD OF OBTAINING POLYFLUORHOROMATIC COMPOUNDS - Google Patents

Description

The method relates to the preparation of polyfluoroaromatic compounds, which can be used as intermediates for the synthesis of various monomers, oils, heat carriers, surface active substances, dyes and medicinal preparations.

A known method for the preparation of polyfluoroaromatic compounds by the reductive dehalogenation of nolithoforhaloaromatic compounds with hydrogen at a temperature of 280 ° C in the presence of a catalyst, which is palladium supported on activated carbon.

The disadvantage of this method is the high cost of the catalyst (palladium refers to precious metals), as well as its high catalytic activity. This leads, along with the hydrogenolysis of the C – Cl bond, to the hydrogenolysis of the C – F bond to a large extent.

In order to reduce the cost of the catalyst and increase its selectivity, nickel or copper deposited on activated carbon are taken as catalyst and the process is carried out at a temperature of 360-400 ° C.

the mash contained 10 wt. about / metal. After drying the catalyst, 40 ml of it is loaded into a Pyrex glass tube with a diameter of 20 ml, the length of the catalyst bed is 17 cm. With a gradual increase in temperature to 400 ° C, nitrogen is flushed through the catalyst for 3–4 hours until nitrogen oxides are completely removed, reduced at the same temperature with hydrogen for 3 hours and used in the reaction. The original product is passed over the catalyst at a temperature of 360-400 ° C with a bulk velocity of 0.5-0.7 hours with a consumption of hydrogen of 6-8 l / h. The catalysts retain their activity for quite some time. Thus, when chloropentafluorobenzene was reduced on a 10o / o Ni catalyst on coal, after 10 hours of operation, the yield of pentafluorobenzene in terms of consumed chloropentafluorobenzene increased from 89% to 92%, and on the catalyst 10% Cp by coal, after 20 hours of operation, the output increased from 80% to 86% . Conversion of the initial product decreased, respectively, from 82 to 70% on the nickel catalyst and from 78 to 60 e / o on the copper catalyst.

Getting peitafluoro benzene a.

current of hydrogen. The hydrogen consumption is b-8 l / h, which exceeds the amount required for the reaction by 2-2.5 times.

The exhaust gas is passed through a water cooler, cooled with dry ice in acetone, traps, after which it enters waste-washing bottles containing 200 ml 4 n. KOH solution for heat, HC1 and HF. After 2 hours the reaction is complete. As a result, 43 ml of catalyst are obtained, the analysis of which by GLC showed the presence of non-fluorobenzene in it, which is 73% for the initial chloropentafluorobenzene.

Distillation of the obtained catalyzate with a fir-tree reflux condenser with a height of 20 cm is allocated a fraction with m. Bale. 84-86 ° С, the analysis of which by GLC shows the presence of 98.6% of the main vesicum in it, which has the same yield time with notorious pentafluorobenzene obtained by decomposition of pentafluorophenylhydrazine. Density

The refractive index and IR spectrum are identical to those described in the literature for pentafluorobenzene.

Example 2. W ml (82 g) of chloropentafluorobenzene is passed through a catalyst bed — 10% copper on coal in a stream of hydrogen at a temperature of 370 ° C with a bulk velocity of 0.6. As a result of the reaction, 41 ml of catalyzate containing 75% pentafluorobenzene was obtained.

Subject invention

The method of producing polyfluoro-aromatic compounds by reductive dehalogenation of polyfluorohalo-aromatic

5 compounds with hydrogen when heated in the presence of a catalyst — a metal deposited on activated carbon, characterized in that, in order to expand the range of catalysts and increase their selectivity, nickel or copper are taken as metal, and the process is carried out at a temperature of 360-400 ° C.