SU1759826A1 - Method of dechlorination of a mixture of polychlorinated diphenyls - Google Patents

Abstract

Summary of the Invention A mixture of polychlorinated biphenyls is completely dechlorinated with hydridesilanes of the general formula RnR 2SiHm, where R is Em, R is Pr, R is R - Ph; n is 0.1; m 1.2, in the presence of nickel chloride and sodium borohydride with a molar ratio of reagents equal to 1- (50-75) :( 7.5-8) :( 1-1.5, respectively). The reaction is carried out at 154-160 & ° C for 7-7.5 hours in an inert atmosphere. 1 tab.

Description

The invention relates to the field of organic chemistry, namely to the method of dechlorination of polychlorinated aromatics, which, as is well known, during storage and incineration form highly toxic substances — chlorinated dioxins and benzofurans.

The invention can be used in the chemical and electrical industries in connection with the need to detoxify chlorine substituted biphenyls.

A known method for dechlorination of fully chlorinated diphenyl- (PCB) with molten aluminum, resulting in iero forms aluminum carbide and aluminum chloride, aluminum carbide is further hydrolyzed with water to form aluminum oxide and methane. 58 mol of Apyumin for 3 mol of PCB is used in the reaction, it flows at 500 ° s The disadvantages of this method include the use of a very large amount of aluminum, high reaction temperature,

the irreversible consumption of aromatic compounds - the final product of this method is methane 1

Known methods for dechlorination of PCBs using dispersed alkali metals or their amalgams 2 The reaction is carried out in a large amount of solvent, for example, THF. The product of reduction is diphenyl. The main disadvantages of the methods are that alkali metals are used in very large quantities - up to 30 metal agomes per chlorine atom, as well as a large amount of organic solvents, which makes these methods explosive and low-tech.

The known method of dechlorination of PCBs (a mixture consisting of 4-7 chlorine-substituted diphenyls) with naphthalene with the addition of 50 mol.% Excess of metallic sodium 3. The reaction is carried out in THF, in an inert atmosphere at room temperature for 4 hours. The reaction results in diphenyl.

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The main disadvantages of the method are the use of large quantities of metallic sodium and an organic solvent, which makes the process explosive and low-tech.

The purpose of the invention is to simplify and increase the safety of the process.

This goal is achieved by the process of dechlorination of a mixture of PCB using hydridesilanes of the general formula RnR 2SlHm, where R is Et, R is Pr; R R -Rh; n 0.1; m 1,2, nickel chloride and sodium borohydride at the molar ratio of PCB: silane reagents: M С12: №ВН4 1: (50-75) :( 7.5-8) :( 1 -1.5} at 154- 160 ° C for 7-7.5 h in an inert atmosphere.

As a dechlorination object, a mixture of chlorinated biphenyls with the number of chlorine atoms in a molecule of 1-10 was studied. The average number of chlorine atoms in a mixture is 5. This mixture, under the technical name Sovol, is widely used as a transformer liquid.

The Sovol is dechlorinated in an inert atmosphere as follows: a mixture of silane, nickel chloride and sodium borohydride is boiled under reflux in an argon atmosphere for 10 minutes, then the sovol is added and the mixture is boiled for 7-7.5 After separation of the nickel, distilling off the excess silane and the resulting chlorosilane, biphenyl is obtained in quantitative yield.

The result of this process is the complete dechlorination of the PCB mixture to form diphenyl.

The results of the dechlorination of the PCB mixture are shown in the table.

Below are examples of specific embodiments of the invention.

Example 1. 9.0880 g (63.13 mmol) of ethyl dipropylsilane, 1.2280 g (9.47 mmol) of nickel chloride and 0.047 g (1.26 mmol) of sodium borohydride were placed in a single-neck flask with reflux condenser (and 154 ° C) 10 min in an argon atmosphere. Then, 0.4120 g (1.26 mmol) of sovol is added and the mixture is boiled (154 ° C) for 7 hours under argon atmosphere. Then nickel is separated, the excess silane is distilled off and the resulting chlorosilane. The output of diphenyl 0.2040 g (96%).

Example 2. As in Example 1, 7.9160 g (54.97 mmol) of ethyldipropylsilane, 0.7600 g (6.18 mmol) of nickel chloride, 0.0420 g (1.10 mmol) of sodium borohydride and 0.2392 are used. g (0.73 mmol) sovol. Boil t 7.5 h. Diphenyl yield 0.1080 g (97%)

Example 3. In Example 1, 4.5270 g (31.4550 mmol) of ethyldiprolylsilane, 0.6800 g (5.24 mmop) of nickel chloride,

0.0260 g (0.70 mmol) of sodium borohydride and 0.70 mmol of sovol. Diphenyl yield: 0.0882 g (83%).

Example 4, In example 1. use

9.0040 g (62.53 mmol) of ethyl dipropylsilane, 1.1354 g (8.75 mmol) of nickel chloride, 0.0468 g (1.25 mmol) of sodium borohydride and 0.4080 g (1.25 mmol) of sovol. The output of diphenyl 0.1513 g (79%).

Example 5: According to Example 1, 6.8686 g (47.70 mmol) of ethyl dipropylsilane, 0.9280 g (7.15 mmol) of nickel chloride, 0.0270 g (0.71 mmol) of sodium borohydride are used. and 0.311 g (0.95 mmol) of Vova Diphenyl

0.1237 g (84%).

Example 6. In Example 1, 10.9056 g (75.75 mmol) of ethyl dipropylsilane, 1.4836 g (11.36 mmol) of nickel chloride, 054546 g (1.51 mmol) of sodium borohydride and

0.4955 g (1.51 mmol) sovol. The mixture was boiled for 6 hours. The yield of diphenyl was 0.0291 g (82%).

Example 7. In a single-neck flask with reflux condenser, 8.4710 g (46.00 mmol) of diphenylsilane, 0.8949 g (6.90 mmol) of nickel chloride and

0.0340 g (0.90 mmol) of sodium borohydride and heated for 10 minutes at 154 ° C under argon atmosphere. Then, 0.3010 g (0.90 mmol) of sovol is added and the mixture is heated at 154 ° C for 7 hours under argon atmosphere. Received by

diphenyl is distilled off. The output of diphenyl 0.1367 g (97%).

The advantage of the proposed method is that the process of dechlorination of polychlorinated biphenyls is carried out in a safe environment using hydridesilanes, nickel chloride and sodium borohydride without a solvent, as in the known method, the dechlorination of polychlorinated biphenyls is carried out in an excess of metallic sodium and in an organic solvent explosive and non-technological process.

Claims (1)

Invention Formula A method for dechlorination of a mixture of polychlorinated biphenyls, characterized in that, in order to simplify the process safety, a mixture of polychlorinated biphenyls is treated with a force of the general formula RnR 2SiHm, where R is ethyl; R1 is propyl or R is R-phenyl; n 0 or 1; m 1 or 2, in the presence of nickel chloride and sodium bromide with a molar ratio of polychlorinated 5 diphenyls: silane; nickel chloride: sodium borohydride 1: 50-75: 7.5-8: 1-1.5 at 154-160 ° С for 7-7.5 h in an inert atmosphere. 517598266 The conditions and results of dechlorination of a mixture of polychlorinated biphenyls with an average number of chlorine atoms in a molecule equal to 5 (sovol)