RU2108317C1 - Method for production of hexachloro-p-xylene - Google Patents

Abstract

FIELD: technology of production of chloroorganic compounds, namely, production of hexachloro-p-xylene, being used as origin material for production of terephthalyl chloride which represents itself component of composition which accelerates polymerization by tire production and medicinal preparation in medicine and in veterinary. SUBSTANCE: chlorination is initiated by azo-bis-isobutyronitrile. Chlorination is carried out at 80-100 within 10 h in the medium of carbon tetrachloride or hexachloro-p-xylene in the presence of tributyl phosphate, dimethyl formamide or mixture thereof (their quantity being 0.4-0.8 mass %). EFFECT: improved efficiency of the method. 1 tbl

Description

 The invention relates to the technology of organochlorine compounds, and in particular to a method for producing hexachloroparaxylene, an initial product for the preparation of terephthalyl chloride, an integral part of a composition for accelerating polymerization in the tire industry and a medicinal product in medicine and veterinary medicine.

 Known methods for producing hescachloroparaxylene by chlorination of p-xylene under UV illumination using hexachloroparaxylene as a solvent (US Pat. No. 4029560, class B 01 J 1/10, 1977), or 5-20 wt.% Carbon tetrachloride (German application N 2614139, class C 07 C 25/14, 1979).

 The disadvantages of these methods of obtaining hexachloroparaxylene are high energy costs, as well as the need to use special light sources - mercury-quartz lamps, which significantly increase the fire and explosion hazard of the process.

From literature data it is known that to prevent the side process of chlorination of p-xylene into the nucleus, various compounds are used - inhibitors added to the reaction mass. Thus, methods are known for producing hexachloroparaxylene by photochemical initiation of chlorination of p-xylene to methyl groups at 50-150 ^° C in the presence of triaryl phosphates, pentaerythritol, polypropylene glycol, mannitol and mixtures thereof (US Pat. No. 2,979,448, C 07 C 25/14, 1961), in the presence of amides of the general formula RCDNR ¹ R ² , where R = H or lower alkyl (US Pat. No. 3836445, class B 01 J 1/10, 1974), as well as in the presence of triethylamine, diisopropylamine, N-methylpiperidine, piperidine, pyridine , pyrrolidine, morpholine, piperazine or ethanolamine (application Jap. 53-77022, class C 07 C 25/14), potassium thiocyanate, thiome Chevin and geksametilentatramina (Japanese Patent Application 57-3655, cl. C 07 C 21/14). These methods have all the same disadvantages related to the photochemically initiated chlorination of p-xylene.

 There is also a known method for producing hexachloroparaxylene by chlorination of p-xylene in the presence of chemical initiators: peroxides, hydroperoxides and azobisisobutyronitrile in carbon tetrachloride or without solvent (LCX, 1960, 30, N 9, p. 3019-3024). To prevent chlorination in the aromatic nucleus, in this method, an addition of urotopine in an amount of 0.1-0.2 wt.% Is used.

 The disadvantages of this method are the insufficiently high yield of hexachloroparaxylene (50-90%) and twice the estimated consumption of chlorine.

 The closest in technical essence is the method of producing hexachloroparaxylene by chlorination of p-xylene in the presence of hexamethylene diamine, urotropine, urea, diethanolamine, triethyl phosphate and other additives that inhibit secondary chlorination to the core (Petrochemistry, 1974, v. 14, No. 6, p. 885-890 ) The initiation of chlorination in this method is carried out using azobisisobutyronitrile (1-1.15% by weight of p-xylene), and 9.2-10.9 moles of chlorine are introduced into the reaction per 1 mol of p-xylene.

 The main disadvantage of this method is a significant excess of chlorine (37-82%) supplied to the reactor, and insufficiently high (less than 97.5%) purity of the resulting hexachloroparaxylene.

When creating the invention, the task was to reduce the consumption of chlorine used in the process, and to increase the yield and purity of hexachloroparaxylene. This is achieved by the fact that chlorination of p-xylene is carried out in an environment of carbon tetrachloride or hexachloroparaxylene with the addition of 0.4-0.8 wt.% Tributyl phosphate, dimethylformamide or their mixtures at 80-120 ^o C for 10 hours.

Chlorination of p-xylene in the presence of less than 0.4 wt.% Tributyl phosphate, dimethylformamide or mixtures thereof does not preclude the introduction of chlorine atoms into the nucleus, and the use of more than 0.8 wt.% The number of the above inhibitors is inappropriate. Lowering the temperature of the process below 80 ^o C leads to a significant increase in the duration of chlorination, and increasing the temperature above 120 ^o C causes an increase in the number of by-products of the reaction and is not economically feasible.

Example 1. In a three-necked tube reactor with a volume of 100 ml, equipped with a thermometer, a dropping funnel, a reflux condenser with a gas outlet pipe and a gas supply pipe with a porous bubbler, 26.54 g (0.25 mol) of p-xylene, 0.13 g (0 , 5% of the amount of p-xylene) tributyl phosphate, 0.02 g of azobisisobutyronitrile and 12 ml (19 g, 0.12 mol) of carbon tetrachloride. Through a mixture heated to 70-75 ^o C, a stream of dry chlorine is passed at an initial speed of 30 g / h. The temperature in the reactor spontaneously rises to 90 ^o C. In the first hour of chlorination, maintain a temperature of 80-90 ^o C, first cooling, and then heating the reaction mass. Chlorination is carried out for 10 hours, gradually (by 5 ^° C in 1 hour) raising the temperature to 110-120 ^° C. The last 3 hours of chlorination maintain the temperature of 110-120 ^° C. The initiator (azobisisobutyronitrile) is introduced into the reactor in portions every 40-60 minutes, and the last 2 hours of the process - every 30 minutes in the form of a 1.5% solution in carbon tetrachloride (0.2 g of azobisisobutyronitrile in 10 ml of CCl ₄ ).

 After 3 hours of chlorination, and until the end of the process, carbon tetrachloride is distilled off from the reaction mixture into a cooled trap.

 The chlorine feed rate is gradually reduced from 30 g / h. in the first hour of interaction up to 5 g / h. in the last two hours of the process. The total amount of chlorine fed to the reactor is 130 g (1.83 mol), i.e. 122% of theory. Chlorine slip is 23.6 g (0.33 mol).

Upon completion of chlorination, an inert gas current is passed through the reaction mass at 110-115 ^° C for 40 minutes to remove dissolved chlorine and hydrogen chloride. After that, the reaction mixture is cooled, the crystallized mass is crushed, dried in air at 20-30 ^° C for 20 hours. The yield of the crude product is 78.6 g, i.e., practically quantitative. According to gas-liquid chromatography (GLC), the crude contains 98.12% hexachloroparaxylene. The melting point of the product is 108-110 ^o C.

To remove impurities, the raw material is washed with 96% ethanol (60 ml) at 20-30 ^° C. After washing and drying, 75.4 g of product are obtained with mp. 110-111 ^o C. The yield of hexachloroparaxylene 96.4%, purity according to GLC - 99.34%.

Example 2. Chlorination is carried out according to the method of example 1, starting from 21.23 g (0.2 mol) of p-xylene, 0.13 g of tributyl phosphate and 15.64 g (0.05 mol) of hexachloroparaxylene. The initiator is added in portions every 40-60 minutes in the form of a solution in chloroform (0.26 g of azobisisobutyronitrile in 5 ml of chloroform). The amount of chlorine supplied is 100 g (1.41 mol), i.e. 117.5% of theory. Chlorine slip - 14.9 g (0.21 mol). After purging with an inert gas, crystallization, and drying, 78.7 g of a crude product are obtained with mp. 108-111 ^o C. The quantitative yield, the content of hexachloroparaxylene in the product according to GLC is 98.14%.

Example 3. Chlorination is carried out according to the method of example 1, starting from 0.25 mol of p-xylene, 0.1 g of dimethylformamide in 12 ml (19 g) of carbon tetrachloride. The initiator is added in portions every 30-60 minutes in the form of a solution of CCl ₄ (0.26 g of azobisisobutyronitrile in 11 ml of CCl ₄ ). 130 g (1.83 mol) of chlorine are fed, i.e. 122% of the calculated amount. Chlorine slip is 23.6 g (0.33 mol).

Get 78.9 g of the crude product with so pl. 108-111 ^o C. The quantitative yield. According to GLC, raw contains 98.7% hexachloroparaxylene. After washing with 50 ml of ethanol and drying, 75.66 g of product are obtained with mp. 110-111 ^o C containing, according to GLC 99.21% of hexachloroparaxylene. The yield of purified product is 96.7%.

Example 4. Chlorination is carried out according to the method of example 1, starting from 0.25 mol of p-xylene, 0.1 g (0.4% by weight of p-xylene) of dimethylformamide and 0.1 g of tributyl phosphate in 10 ml (15.8 g ) carbon tetrachloride. The initiator is added in portions every 30-60 minutes as a solution in CCl ₄ (0.26 g of azobisisobutyronitrile in 11 ml of CCl ₄ ). Chlorine consumption is 135 g (1.9 mol), that is 127% of the calculated. Chlorine slip 28 g (0.4 mol).

Obtain 79 g of the crude product with so pl. 110-111 ^o C. The quantitative yield. The product according to GLC contains 99.28% hexachloroparaxylene.

 A comparison of the proposed and known methods for producing hexachloroparaxylene is given in the table.

 As can be seen from the above examples and table data, the proposed method can reduce the excess of chlorine in comparison with the prototype by at least 10%, increase the yield of hexachloroparaxylene by 3%, and also increase the content of the main substance in the product by 0.6-1.8% .

Claims (1)

The method of producing hexachloroparaxylene by the interaction of chlorine with paraxylene in a solvent initiated by azobisisobutyronitrile in the presence of compounds inhibiting chlorination to the core, characterized in that the chlorination is carried out in a medium of carbon tetrachloride or hexachloroparaxylene in the presence of 0.4 to 0.8 wt.% Tributyl phosphate, dimethylformide mixtures thereof at 80 - 120 ^o C for 10 hours

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