Method of purifying chloroform

FIELD: chemistry.

SUBSTANCE: invention relates to a method of purifying chloroform through its treatment with a mixture of gaseous sulphuric anhydride with air, obtained by passing air through oleum heated to temperature 30°C-60°C. Treatment is carried out at temperature 20°C-50°C for 2-7 hours and content of sulphuric anhydride in the gaseous mixture of 20-50 wt %.

EFFECT: obtaining high-quality chloroform, in which not only 1,1-dichloroethane is absent, but cis- and trans-dichloroethane as well, considerable reduction of waste water and gaseous emissions, reduction of raw material consumption.

1 cl, 1 ex, 3 tbl

 

The invention relates to a method of purification of chloroform and can be used in the chemical industry.

When thermal chlorination of methane along with chloroform receive chloromethyl, methylene chloride and carbon tetrachloride.

The limited capacity of the reactors chlorinators for heat removal does not allow you to adjust the ratio of the produced chlorine-methanes in a wide range of values and to achieve a significant increase in output of chloroform in comparison with methylene chloride.

Known methods for producing chloroform or increase its output purposefully implemented, the chlorination mixture of chlormethyl with methylene chloride (A.S. No. 1578119 the USSR, MKI SS 19/04, 17/10. Publ. 15.07.90. Bull. No. 26 - 8 S. Patent No. 4927981 USA, MCI SS 17/12. Publ. 22.05.90. Application No. 2547297 France, MKI SS 19/06, 17/10, 19/02, 19/04. Publ. 14.12.84).

However, these methods are complicated in hardware design and in their implementation along with the chloroform is obtained a significant amount of carbon tetrachloride (Chu).

Due to increased requirements to quality of chloroform have acquired special significance to the problem of cleaning it from impurities. The reason for the presence of the methylene chloride and chloroform various impurities that impair their quality, is the presence in the source methane its homologues, engaging with the conditions of obtaining chlorine-methanes in series-parallel re the work of chlorination, telomerization, oligomerization, hydrochlorination. All this leads to the formation of the complex range of products, polluting technical methylene chloride and chloroform. A significant portion of these impurities is a boiling chlorinated methane, ethane and ethylene, which due to the proximity of their properties to the properties of methylene chloride and chloroform accompany them on stage rectification. Passing the chloroform has the following composition, wt.%.

chloroform75-89
carbon tetrachloride7-22
methylene chloride0.05 to 15
TRANS-dichlorethyleneOTC 0,078
CIS-dichloroethyleneOTS-0,28
1,1-dichloroethanefrom 0.01 to 0.78
1,2-dichloroethane0.1
1,1,2-trichloroethylene1.5
highly atany2.5

Of these compounds, CIS-dichloroethylene and 1,1-dichloroethane boil at temperatures the meet is but 60 and 57.3°C and to separate them from chloroform, boiling at a temperature of 61°C, very problematic. It is known that purification from impurities boiling chloroalkanes possible through chlorination. The resulting high-boiling impurities can be separated by distillation (Izv. Tula GU / Aleska, Linganamakki, Eversave; TSU. - Tula, 2005. - (Ser. Chemistry, Vol.5). - S-319; U.S. Patent No. 4225520 (1980), Molecular halogenoalkane olefins / Gbeji, kinetics and. M.: Izd. Moscow state University, 1985. - 240 S.).

However, this method has not found its applications in industry, because it does not provide the necessary degree of purification from impurities. Complicates the technological process, increases energy consumption and leads to a decrease in the content of chloroform by chlorination him to methylene chloride and carbon tetrachloride.

Known introduced into production method obtaining chloroform in the mixture with methylene chloride and chloride stands by thermal chlorination of methane at a temperature of 480-550°C (Industrial organic products: a Handbook / edited Laatina. - M.: Chemistry, 1978. - 656 C.). On rectification of the chlorine-methanes received after purification systems, compression and condensation. The output from the cube to the rectification column, a mixture of chlorine-methanes is supplied as the supply of liquid in the second column, where the selection of methylene chloride as a distillate. Cube the I liquid of the column, containing mainly chloroform, and carbon tetrachloride ("associated" chloroform), oleum is directed to purification from impurities, where the removal of impurities by the esterification reaction with oleum. After oleum purification from impurities passing the chloroform is fed into the rectification column, where the distillate is allocated commodity chloroform.

The disadvantage of this method is the formation stage oleum purification of large quantities of spent sulphuric sulphuric acid (1 ton cube - 0,13 tons of sulphuric acid based on 100%). Due to the lack of sales spent sulphuric acid recently decided to neutralize its 10%sodium hydroxide solution and the discharge of wastewater containing up to 14% sodium sulfate in the slurry drains. Thus, 1 t distillation of methylene chloride is formed of 1.4 tonnes of sewage sludge and 1.56 t waste sodium hydroxide solution after the neutralization of the acid chloroform and gases.

The closest is the method of purification of chloroform gaseous sulfur trioxide. Sulphur dioxide is produced from 25%oleum by heating to 270°C (report Veselova EM and other Cleaning chloroform gaseous sulfur dioxide, Science in the XXI century: proceedings of the Republican scientific-practical conference on chemistry, dedicated to the 35-litochevskogo state Univ is reteta and chemical-pharmaceutical faculty Ed-in Chuvash. GOS. University, 2002, s).

The disadvantages of the method are the supply of sulfuric anhydride in the system at a sufficiently high temperature that ethnologica. In addition, it is not possible to clear from chloroform CIS-dichloroethylene and TRANS-dichlorethylene.

Technical result - receiving chloroform high quality, which not only 1,1-dichloroethane, and CIS - and TRANS-dichlorethylene, a significant reduction in wastewater and gas emissions, reduce consumption of raw materials is achieved in the method of purification of chloroform by treating it with a mixture of gaseous sulfur dioxide with air obtained by passing air through the oleum heated to a temperature of 30°C-60°C, and the processing is carried out at a temperature of 20°C-50°C for 2-7 hours and the content of sulfur dioxide in the gas mixture of 20-50% of the mass.

The most technologically advanced and simple in execution, in our opinion is a method of obtaining sulfur dioxide (SO3mixed with the air from the oleum. A mixture of the desired composition receive, passing the air through a column filled with oleum heated to a temperature of 30°C.-60°C. the Spent oleum is used in the enterprise to obtain the concentrated sulfuric acid used in the production processes of other industries, which makes the process economically viable.

The method is carried out the trail the way.

Example 1. The process is carried out in a column type reactor at a temperature of 20-50°C, varying the concentration of SO3dilution air amount and reaction time. A mixture of sulfuric anhydride with air to the desired composition of gain, passing the air through a column filled with oleum heated to a temperature of 30°C.-60°C.

The number of SO3determined by loss of weight of the reactor with oleum, and the volume of air measured at the output of the system. The composition assessed by indirect indicators, which developed method of determination of acidic impurities and chlorine ion in aqueous and non-aqueous environment. The number of chlorine-ion, defined in non-aqueous environment, consistent with prosulfocarb, chlorosulfonic acid and partially - phosgene, that is entered in response to chloroform, Chu. And the amount of chlorine that is defined in the aquatic environment after hydrolysis of acidic impurities, consistent with the overall amount of chlorinated hydrocarbons, which came in the reaction of sulfonation. In addition, determine the chromatographic composition of the reaction mass.

Data for the optimization process are presented in table 1. Reduction of the concentration of sulfuric anhydride in a mixture with air below 20% of the mass. leads to an increase in the content of impurities in chloroform and the need to increase the processing time. Increasing the concentration of sulfuric anhydride in the mixture with air is om above 50 wt%. does not improve the cleaning process and is not economically feasible. Optimal processing time 2-7 hours. Sulfonation artificial mixtures containing impurities 1,2 - and 1,2-dichlorethylene and dichlorethane, oleum and gaseous SO3presented in table 2. A comparative analysis of the esterification passing chloroform-oleum and gaseous sulfuric anhydride per 1 ton of passing chloroform are presented in table 3.

The data show that the proposed method allows you to clear the "incidental" chloroform from impurities prior to their complete absence (table 1), to obtain the chloroform of high quality (table 2), to increase the yield of chloroform, to exclude the consumption of oleum and education of spent sulphuric acid, to exclude the formation of a significant amount of wastewater (1.4 tons per 1 ton of passing chloroform), 2 times to reduce the consumption of alkali (table 3).

Table 3
A comparative analysis of the esterification passing chloroform-oleum and gaseous sulfuric anhydride per 1 ton of passing chloroform
IndexSubstantial oleum production us what the conditions Etherification with oleum in the laboratoryEtherification SO3in mixtures with air in the laboratory
1234
1. Consumption of oleum, t/t0,140,1-
2. Flow free SO3in relation to the original chloroform, %4,3 (0,0043 t/t)3,5 (0,0035 t/t)3,7 (0,0037 t/t)
3. The time of esterification, h548
4. Process temperature, °C43-544725
5. The output of chloroform in the acidic reaction mass relative to the original chloroform, %979898,5
6. The acidity of the reaction mass in terms of H2SO4, %3,5a 3.95-8
7. The temperature of the neutralization, °C503520
8. The output of chloroform crude in relation to the original passing the chloroform, %96,796,897,7
9. The consumption of caustic soda (100%) to neutralize acidic chloroform, t/t0,0220,040,08
10. The consumption of caustic soda (100%) to neutralize gases stage of decomposition of oleum, t/t0,0380,025-
11. The total consumption of caustic soda to neutralize the acidic chloroform and gases, t/t0,060,0650,08
12. The number of spent sulphuric acid, t/t0,190,11-
13. The consumption of caustic soda to neutralize sulfuric acid,t/t0,1550,09-
14. Total p is the gathering of caustic soda, t/t0,2150,1550,08

The method of purification of chloroform by treating it with gaseous sulfur trioxide obtained from oleum by heating, characterized in that a mixture of gaseous sulfur dioxide with air obtained by passing air through the oleum heated to a temperature of 30-60°C., and the treatment is carried out at a temperature of 20-50°C for 2-7 h and the content of sulfur dioxide in the gas mixture of 20-50 wt.%.



 

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