RU2410369C1 - Method of producing chloroform - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: method of producing chloroform involves thermal chlorination of methane, subsequent condensation of the obtained mixture of chloromethanes, returning uncondensed components for chlorination, extraction of the desired product and methylene chloride from the condensate through distillation and returning the extracted methylene chloride for chlorination, further chlorination of methane together with methylene chloride and uncondensed components. Condensation of chloromethanes takes place in fractional condensation conditions with complete condensation of chloroform and tetrachloromethane and partial condensation of methylene chloride, where an uncondensed gas stream containing vapour of methylene chloride, methyl chloride and unreacted methane is returned for thermal chlorination, and the condensed part of methylene chloride is extracted from the condensate of chloromethanes through distillation. Methylene chloride extracted from the condensate is used to prepare reflux liquid during fractional condensation of chloromethanes. Fractional condensation of chloromethanes is carried out at pressure 0.2-0.4 MPa and temperature of exhaust uncondensed gases of 0-30C. ^ EFFECT: easy implementation of the process of producing chloroform and, as a result, reduction of power consumption. ^ 4 cl, 2 tbl, 2 dwg

Description

The invention relates to chemical technology, and in particular to a method for producing chloroform used as an intermediate in the industry of basic organic synthesis, in particular fluoroplastic, solvent, extractant.

In the domestic industry, chloroform is an accompanying product in the production of methylene chloride, which is obtained by thermal chlorination of natural gas at a temperature of 480-520 ° C (Industrial organochlorine products. Handbook edited by L. Oshina, M., Chemistry, 1978, p.26 -35). The disadvantages of this method include the use of bulky apparatus for chlorination, the temperature regime is ensured by strict adherence to the ratio of methane-chlorine and methyl chloride recycled in the system. In addition, the methane chlorination process is characterized by the predominant yield of methylene chloride relative to chloroform. For 1 ton of methylene chloride, 0.4-0.5 tons of chloroform and 0.1 tons of bottoms are obtained, containing mainly. ozone-depleting carbon tetrachloride (F.F. Muganlinsky, Yu.A. Treger, M. M. Lyushin “Chemistry and technology of organohalogen compounds”, M., “Chemistry”, 1991, p.67).

Given the reduced demand for methylene chloride, increased demand for chloroform, and the very limited sale of carbon tetrachloride, the process of producing chloroform in two stages has been proposed: the first stage is the chlorination of natural gas, and the second stage is the liquid phase chlorination of methyl chloride and / or methylene chloride. Dochlorination is recommended to be carried out with a chemical initiator or in the conditions of photoinitiation of the reaction (V.N. Rozanov, Yu.A. Treger. "Chemistry and Business", No. 2-3 (66-67), 2005, p. 78). This method allows to increase the yield of chloroform, but requires complex hardware design process.

Closest to the claimed combination of essential features is a method of producing chloroform, including thermal chlorination of methane to obtain a mixture of chloromethanes, removal of methyl chloride from a mixture of chloromethanes and liquid-phase chlorination of a mixture of chloromethanes freed from methyl chloride during photochemical initiation followed by rectification (US Pat. RU No. 2165917, С07С 19/04, С07С 17/10, publ. 04/27/2001).

The known method for producing chloroform is complicated in technical design, requires a two-stage process design, including a site for high-temperature methane chlorination to produce a mixture of chloromethanes, a unit for extracting methyl chloride products from a mixture of chlorination, as well as a unit for liquid-phase photochlorination of a mixture of chloromethanes. The photochlorination process is very sensitive to the presence of inhibitors of the chlorination reaction, primarily to the presence of oxygen. This factor imposes increased demands on the quality of chlorine used. Conventional electrolysis chlorine is not suitable for photochlorination; special purification of electrolysis chlorine from oxygen is required by condensation of chlorine and its subsequent evaporation. Such chlorine preparation is associated with significant energy costs.

The technical task of the present invention is to simplify the hardware design of the process and reduce energy costs.

The stated technical problem is solved in that in a method for producing chloroform, including thermal chlorination of methane, subsequent condensation of chloromethanes and isolation of the target product from them by rectification, return of non-condensable components to chlorination, separation and return to chlorination of methylene chloride, additional chlorination of methylene chloride, according to the invention, additional chlorination of methylene chloride is carried out thermally together with methane and non-condensable components.

The condensation of chloromethanes is carried out in the fractional condensation mode with the complete condensation of chloroform and carbon tetrachloride and partial condensation of methylene chloride, with a non-condensable gas stream containing methylene chloride, methyl chloride and unreacted methane vapors being returned to thermal chlorination, and a fraction of the condensed fraction is recovered from the condensed methylene chloride by condensation.

Methylene chloride extracted from the condensate is used to create reflux during fractional condensation of chloromethanes.

Fractional condensation of chloromethanes is carried out at a pressure of 0.2-0.4 MPa and a temperature of off-gas non-condensable gases 0-30 ° C.

The proposed method is tested in a pilot plant.

The installation includes a gas-phase chlorination reactor for natural gas - methane, a column for capturing hydrogen chloride from chlorinated products, a liquid ring compressor for compressing neutral chlorinated products, and a fractional condensation column for chloromethanes with a non-condensable gas recycle line for chlorination.

The chlorination process is carried out continuously. The chlorination reactor is equipped with a gas jet injection mixer. The injection ratio is 4.8. The temperature of the gas mixture at the outlet of the reactor is 430-450 ° C. The residence time of the gas mixture in the reaction zone is 8-10 s per cold gas.

During the study, the influence of the concentration of reagents at the inlet to the reactor (at the entrance to the nozzle), as well as the concentration of reagents entering the reaction zone, on the selectivity of the process, which is estimated by the yield of carbon tetrachloride per 1 ton of chloroform, was determined. Reagent concentrations at the inlet to the reaction zone were calculated based on the values of the concentrations of the reagents at the inlet to the reactor (at the inlet to the reactor nozzle) and at the outlet of the reaction zone, taking into account the injection coefficient.

The research results are presented in table 1, 2 and figure 1, 2.

As follows from the data presented in the tables and drawings, with an increase in the concentration of methylene chloride at the inlet to the nozzle of the reactor and an increase in the ratio of methylene chloride / chloroform at the entrance to the reaction zone, the selectivity of the process increases, and the formation of carbon tetrachloride per 1 ton of chloroform decreases.

In accordance with the proposed method, the creation of a site for obtaining oxygen-free chlorine, which leads to a reduction in energy consumption, is excluded in comparison with the prototype. In addition, the stage of photochemical chlorination of methylene chloride and subsequent purification of the products of chlorination of methylene chloride from acidic impurities is excluded, which together leads to a simplification of the method.

Table 1 The effect of the concentration of reagents entering the reaction zone on the rate of formation of chloroform and carbon tetrachloride in a gas-jet reactor with internal circulation of reaction gases Experience number The concentration of reagents at the entrance to the reaction zone,% vol. The ratio of CH ₂ Cl ₂ / CHCl ₃ Yield CCl ₄ (kg) per 1 t CHCl ₃ CH ₄ CH ₃ Cl CH ₂ Cl ₂ CHCl ₃ Cl ₂ one 2 3 four 5 6 7 8 one 67.66 8.08 3.99 1,54 3.23 2.59 244 2 59.37 12.16 5.95 3.36 3.21 1.77 223 5 62.17 8.61 8.38 1.65 3.29 5.08 205 6 57.09 9.36 11.92 2.70 3.21 4.41 146 7 56.65 9.66 12.24 2.70 3.17 4,53 146 8 55.39 10.89 12.36 2.67 3.18 4.63 129 9 53.70 10.62 13.78 2.92 3.23 4.72 141 10 54.79 10.33 13.03 2.89 3.35 4,51 149 eleven 57.45 8.79 11.97 2,56 3.29 4.68 156 12 58.67 9.13 10.65 2,52 3.25 4.23 152 13 57.71 9.38 11.40 2.42 3.27 4.71 165 fourteen 62.05 9.64 10.09 1.83 2.81 5.51 146 fifteen 54,99 10.04 15.83 2.68 2.81 5.91 140 16 66.60 8.68 6.36 1.78 2.85 3.57 149 17 54.86 7.98 16.28 2.84 3.09 5.73 115 eighteen 60.04 9.57 13.87 2,35 2.42 5.90 108 19 61.87 10.91 10.75 2,30 2.43 4.67 89 twenty 61.09 10.46 12.55 1.94 2,39 6.47 112 21 62.12 9.56 12.19 2.04 2.42 5.98 101 22 59.24 9.15 16.90 2,36 2.11 7.16 88 23 59.54 9.60 16.76 1.75 2.12 9.58 one hundred 24 60.69 9.73 15.38 1.91 2.11 8.05 82 25 62.73 8.98 15,57 1.79 1.87 8.70 79 26 61.37 9.83 16.02 1.81 1.88 8.85 88 27 64.25 9.23 13.73 1.73 1.87 7.94 64

table 2 The effect of the concentration of reagents at the inlet to the reactor (inlet to the nozzle) on the yield of carbon tetrachloride during methane thermochlorination (the numbering of experiments in Table 2 corresponds to the numbering of Table 1) Experience number The concentration of reagents at the entrance to the nozzle,% vol. Yield CCl ₄ (kg) per 1 t CHCl ₃ CH ₄ CH ₃ Cl CH ₂ Cl ₂ Cl ₂ one 2 3 four 5 6 eleven 58.59 7.69 14.81 18.88 156 12 60.75 6.64 13.87 18.70 152 13 60.72 6.64 13.84 18.77 165 fourteen 61.38 7.88 14.56 16.16 146 fifteen 61.16 7.38 15.28 16.14 140 16 72,20 7.85 3.64 16.39 149 17 57.70 6.43 18.05 17.74 115 eighteen 64.45 7.01 14.61 13.88 108 19 61.92 9.14 14.96 13.95 89 twenty 61.23 9.56 15.41 13.75 112 21 63.36 8.13 14.57 13.88 101 22 61.70 7.68 18.43 12.11 88 23 62.34 7.83 17.60 12.18 one hundred 24 62.02 8.24 17.60 12.11 82 25 64.18 7.57 17.47 10.74 79 26 63.80 7.29 18.07 10.78 88 27 62.96 7.97 18.2 10.75 64

Claims (4)

1. A method of producing chloroform, including thermal chlorination of methane, subsequent condensation of chloromethanes and isolation of the target product from them by rectification, return of non-condensable components to chlorination, separation and return to chlorination of methylene chloride, additional chlorination of methylene chloride, characterized in that the additional chlorination of methylene chloride is carried out thermally together with methane and non-condensable components. 2. The method according to claim 1, characterized in that the condensation of chloromethanes is carried out in fractional condensation mode with complete condensation of chloroform and carbon tetrachloride and partial condensation of methylene chloride, the non-condensing gas stream containing methylene chloride, methyl chloride and unreacted methane vapors being returned to thermal chlorination, and the condensed part of methylene chloride is extracted from the condensate of chloromethanes by rectification. 3. The method according to claim 1 or 2, characterized in that the methylene chloride extracted from the condensate is used to create reflux during fractional condensation of chloromethanes. 4. The method according to claim 3, characterized in that the fractional condensation of chloromethanes is carried out at a pressure of 0.2-0.4 MPa and a temperature of exhaust non-condensing gases of 0-30 ° C.

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