RU2061668C1 - Process for cleaning dichloroethane of chloroprene - Google Patents

Abstract

FIELD: production of polymeric materials. SUBSTANCE: cleaning operation is carried out by treatment of the reaction mixture with agent which binds chloroprene with catalytic liquid complex AlCl₃•Al[(CH₂CH₂)_nCl]C₁₂, wherein n is 1-12. The latter is obtained by treatment of vat residues resulting form chloroethyl production with aluminium chloride in the form of solution thereof in dichloroethane. The cleaning operation is carried out at AlCl₃ concentration of 20-25 wt % in the complex under continuous stirring for 0.5-5.0 hours at 0-60 C to give liquid polychloroprene dissolved in organic solvents. EFFECT: more efficient purification process. 5 cl

Description

 The invention relates to the field of organic chemistry, and in particular to processes for the purification of dichloroethane from chloroprene, and can be used for polymerization of diene hydrocarbons in organic solvents.

 Currently, waste generated in the production of vinyl chloride by cracking dichloroethane (the so-called "light fraction"), consisting of 75-85% of the mass. dichloroethane, 10-20% of the mass. chloroprene and 2-5% by weight of various chlorinated hydrocarbons are sent for combustion, (1) due to the lack of a convenient way to separate them.

 The main disadvantages of the method of waste disposal: the destruction of valuable products, the expenditure of a large amount of sodium hydroxide on the binding of hydrogen chloride generated during the combustion of these wastes and other additional costs associated with burning.

 The known method (2) for the removal of chloroprene from 1,2-dichloroethane in the production of vinyl chloride by thermal cracking of 1,2-dichloroethane. The method proposes to remove chloroprene from dichloroethane obtained after thermal cracking of dichloroethane and separation of hydrogen chloride and vinyl chloride on a distillation column, treatment with chlorine, which is recommended after chlorination of chloroprene impurities with gaseous chlorine, additionally treated with gaseous ethylene in order to bind the dissolved unreacted chlorine, and then carry out chlorine, and then dichloroethane from chloroprene chlorination products.

 This method has a number of significant drawbacks: costly chloroprene is irretrievably lost, the use of chlorine and ethylene is required, the excess of dissolved chlorine must be removed, the problem of the use or destruction of chloroprene chlorination products again arises.

 The closest in technical essence to the proposed method is a method for the purification of dichloroethane from chloroprene (3), which consists in processing dichloroethane containing chloroprene and formed in the production of chlorvinyl by thermal cracking of dichloroethane, chlorine in 1-1.5-fold excess for interaction with chloroprene followed by the separation of chloroprene chlorination products in the distillation column and the return of dichloroethane in the production cycle.

 This method also has several disadvantages: the irrevocable loss of chloroprene requires the use of chlorine; a mixture of heavy chloroprene chlorination products is formed, which require the development of a method for their destruction in order to protect the environment.

 The aim of the proposed invention is the purification of dichloroethane from chloroprene and obtaining liquid polychloroprene soluble in organic solvents.

This goal is achieved in that the initial mixture of dichloroethane with chloroprene is treated with continuous stirring for 0.5-5.0 hours at a temperature of 0-60 ^o With a liquid catalytic complex of the formula A1Cl ₃ AI [(CH ₂ CH ₂ ) _n CI] Cl ₂
where p 1 12 obtained by treating VAT bottoms of the production of chloroethyl with aluminum chloride. After that, dichloroethane is distilled off at a temperature of up to 100 ^o C to obtain a cube of liquid polychloroprene soluble in organic solvents and the distilled dichloroethane is returned to the current rectification process.

 The catalytic complex is used in the form of its solution in DCE in the ratio of the catalytic complex: dichloroethane equal to 1-1: 4.3 wt.h. and take it in an amount of 3-6 mass. parts per 100 parts by weight chloroprene.

At the end of the processing process, the complex is destroyed by water in an amount of 15 moles of water per mole of aluminum chloride at a temperature of 20-50 ^o C.

 Advantages of the Invention

 It excludes the burning of a light fraction of the production of chlorovinyl by cracking dichloroethane with a complete return to the production cycle of dichloroethane and the production of liquid, which does not have an unpleasant odor (in toluene, ethyl acetate, dichloroethane, benzene, gasoline, xylene, etc.) of polychloroprene, which gives broad prerequisites for its use in various purposes. The formation of gas emissions into the environment when burning light fractions is excluded. Eliminates the consumption of caustic soda to bind the hydrogen chloride generated during the combustion of the light fraction, does not require the use of chlorine to clean dichloroethane from chloroprene. The above is confirmed by the examples below.

 Example 1. In a four-necked flat-bottomed reactor equipped with a thermometer and stirrer, placed in a water bath, after purging with nitrogen, 100 ml (116 g) of a light fraction of the composition were loaded: 1,2-dichloroethane 83% by weight. 1,1-dichloroethane - 1.6% of the mass. chloroprene 11.1% of the mass. The amount of impurities (chloromethyl, chloroethyl, methylene chloride, carbon tetrachloride, heavy impurities and unidentified) 4.3% of the mass.

The temperature in the reactor when the stirrer is brought up to 23 ^o C and load at the same time 2 g of a solution of the catalytic complex in dichloroethane containing 25% of the mass. aluminum chloride (0.5 g). The polymerization of chloroprene is carried out at a temperature of not more than 35 ^o C for 3 hours.

Then, with stirring, dichloroethane is distilled off until the temperature in the reactor reaches 100 ^° C and is further purged with nitrogen for 1 min. In the cube, liquid polychloroprene remains, containing traces of DCE and well soluble in all of the above solvents.

 The resulting distillation has a composition (% wt.): 1,2-DCE 96.25; 1,1-DCE 1.81; chloroprene 0.01; the amount of impurities is 1.93.

Amount of distillation 100.3 g, yield 1,2-DCE 99.64 Degree of purification from chloroprene 99.8%
Example 2. According to the conditions of example 1, but the temperature in the reactor during the cleaning process is maintained in the range of 0-10 ^o C for 6 hours.

 The resulting distillation has the composition: 1,2-DCE 96.1; 1,1-DCE 1,8; chloroprene - 0.05; the amount of impurities is 2.05.

Amount of distillation 100.1 g, yield 1,2-DCE 99.6% Degree of purification from chloroprene 99%
Example 3. According to the conditions of example 1, but the temperature in the reactor during the cleaning process is maintained in the range of 23-60 ^o C for 1.5 hours. The resulting distillation has the composition: 1,2-DCE 97.35; 1,1-DCE 1,6; chloroprene 0.01; the amount of impurities is 1.04.

 The amount of distillation is 100.2 g, the yield of 1,2-DCE is 99.7%. The degree of purification from chloroprene is 99.8%. Polychloroprene contains a significant amount of insoluble particles, and during the distillation of dichloroethane, the walls of the cube are covered with an insoluble precipitate, which is purified only by treatment with a hot alkali solution.

 Example 4. According to the conditions of example 1, but as the starting light fraction, 112 g of a fraction of the composition (% wt.) Are used: 1,2-DCE 69.53; 1,1-DCE 5.4; chloroprene 19.0; the amount of impurities is 6.07.

The resulting distillation has the composition: 1,2-DCE 89,0; 1,1-DCE 6.87; chloroprene 0.02; the amount of impurities 4.11. The amount of distillation 87.6 g, the yield of 1,2-DCE - 99.5%. The degree of purification from chloroprene 99.8%
Example 5. According to the conditions of example 1, but use a solution of the complex in dichloroethane containing 20% by weight of aluminum chloride. The amount of the solution of the complex is 2.5 g. The obtained distillate has the composition (% wt.) 1,2-DCE 96.3; l, l-DCE 1.52; chloroprene 0.02; the amount of impurities is 2.16. The amount of distillation - 101.1 g, the yield of 1,2-DCE 99.6%, the degree of purification from chloroprene 99.9 mass.

Example 6. According to the conditions of example 1, but a solution of the complex with AICI ₃ content _of 50% by mass is used, the complex is taken in an amount of 1 g. The obtained distillate has the composition (% of mass): 1,2-DCE 96.5; 1,1-DCE 1.9; chloroprene 0.01; the amount of impurities is 1.59. The amount of distillation 99.8 g, the yield of 1,2-DCE 99.6%, the degree of purification from chloroprene 99.9%
Liquid polychloroprene contains a significant amount of lumpy particles up to 1 mm in diameter, insoluble in solvents.

Example 7. According to the conditions of example 1, but the amount of the solution of the complex for purification of the light fraction from chloroprene is taken in an amount of 3 g (0.75 g AlCl ₃ ). The resulting distillation has a composition (% wt.): 1,2-DCE 96.34; 1,1-DCE 1.79; chloroprene 0.01; the amount of impurities of 1.85 g; yield of 1,2-DCE - 99.6% Degree of purification from chloroprene 99.8%
Example 8. Under the conditions of example 1, but the amount of the solution of the complex is taken 1.5 g. The obtained distillation has the composition (mass.): 1,2-DCE 95.82; 1,1-DCE - 1.65; chloroprene 0.04; the amount of impurities is 2.49. The amount of distillation 101.1 g, the yield of 1,2-DCE 99.4% The degree of purification from chloroprene 99.7%
Example 9. According to the conditions of example 1, but after completion of the percent polymerization, the complex is destroyed by water in an amount of 1 ml (15 moles per 1 mol of AlCl ₃ ). The resulting distillation has a composition (% wt.): 1,2-DCE 96.3; 1,1-DCE 1.81; chloroprene 0.01. Amount of distillation 100.3 g, yield 1,2-DCE 99.7% Degree of purification from chloroprene 99.9
Example 10 (for comparison). According to the conditions of Example 1, but instead of the complex, 0.5 g _of anhydrous AICI ₃ powder is used as a catalyst. The reaction proceeds with the release of hydrogen chloride in an amount of 1 mol per 1 mol of chloroprene and the resulting reaction mass is a suspension of a polymer insoluble in dichloroethane and is difficult to filter; upon distillation, the walls of the cube are covered with an insoluble precipitate, which removes only when treated with a hot alkali solution.

The change in the amount of distillate and its composition in the examples is a consequence of the receipt of various amounts of 1,2-DCE with a solution of a catalytic complex of different composition and quantity loaded onto the reaction. The above examples show that:
the content of chloroprene in the light fraction up to 19% of the mass. does not interfere with cleaning;
the dissolution of the complex in dichloroethane should be carried out in a ratio of DCE complex equal to 1: 1-3 mass. further dilution is impractical for reasons of increasing energy costs for distillation of DCE;
the complex should not be used without dissolving in a solvent due to the formation of an insoluble polymer;
the amount of complex for cleaning should not be used more than 0.5 g (in terms of the content of AICl ₃ ), because a further increase in the amount of loading does not give an additional effect, but it should not be reduced below 0.375 g, either. the degree of purification decreases markedly.

Claims (5)

1. The method of purification of dichloroethane from chloroprene by treating the reaction mass with a chloroprene binding agent, followed by distilling off the dichloroethane and returning it to a cycle, characterized in that a liquid catalytic complex of the formula is taken as a chloroprene binding agent
AlCl ₃ • Al [(CH ₂ CH ₂ ) _n Cl] Cl ₂ ,
where n 1-12,
obtained by treating bottoms of the production of chloroethyl with aluminum chloride in the form of its solution in dichloroethane, and the cleaning process is carried out at a concentration of aluminum chloride in the complex of 20 to 25 wt. with continuous stirring for 0.5 to 5.0 hours at 0 60 ^o C.  2. The method according to claim 1, characterized in that the process is carried out at a weight ratio of the catalytic complex: dichloroethane used as a solvent, equal to 1: 1 3.  3. The method according to PP. 1 and 2, characterized in that the catalytic complex is taken in an amount of 3 to 6 wt.h. per 100 parts by weight chloroprene. 4. The method according to PP. 1 to 3, characterized in that at the end of the cleaning process, the complex is destroyed by water in an amount of 15 mol of water per 1 mol of aluminum chloride at 20 50 ^o C.  5. The method according to PP. 1 to 4, characterized in that for cleaning take dichloroethane containing 1 to 19 wt. chloroprene.