The method of producing chloroform

 

(57) Abstract:

The invention relates to a method for chloroform liquid-phase chlorination of methylene chloride under photochemical initiation, followed by distillation and subjected to chlorination mixture of chlorine-methanes, obtained by thermal chlorination of methane after the removal of her chlormethyl at a molar ratio of methylene chloride to chlorine 4 - 2 : 1 at a temperature of 35 to 45C. a Mixture of chlorine-methanes contains 50 to 99% of methylene chloride, 45% chlorohydrocarbons C1and up to 2.5% of chlorohydrocarbons C2. The result is improved quality of the obtained chloroform. table 1.

The invention relates to a method for chloroform, used as an intermediate in the industries of organic synthesis, in particular PTFE, solvent and extractant.

In the domestic industry chloroform is a byproduct in the synthesis of methylene chloride, which is obtained by thermal chlorination of methane at a temperature of 480 to 520oC /Directory edited Osina L. A. "Industrial organochlorine products), Chemistry, 1978, S. 26-35/. The process is conducted in a three-dimensional reactors, the specified temperature is provided costi reactors chlorinators for heat removal does not allow you to adjust the ratio of the produced chlorine-methanes in a wide interval of values what makes the scheme is quite stringent in terms of directional changes in the composition of chlorine-methanes. Individual selection of components from harmacy carry out rectification. While chloroform before allocation is undergoing treatment with oleum to remove impurities which are not separated even in a highly efficient distillation (in particular 1,1 - and 1,2-dichlorethylene). This method allows you to get the chloroform high quality with the content of the basic substance is not less than 99.9 wt.%), but is characterized by the formation of significant quantities of acid waste in the form of sulfuric acid and chlorosulfonic acid.

On a number of known methods of obtaining chloroform or increase its output carried out deliberately with the introduction of new stages, is used as raw material is mostly a mixture of chlormethyl with methylene chloride.

So the method of gas-phase chlorination of a mixture of methyl chloride - methylene chloride chlorine (weight ratio mixture of chlorine 1:0,5 - 0,7) at a temperature of 400 - 500oC in a fluidized bed of contact, which simultaneously plays the role of inert heat carrier, because it is a continuous circulation of cooled outside the reactor. The selectivity (the ratio of the century what dostatkom process is the use of high temperatures, leading to side decomposition, condensation, which necessitates the use of additional purification techniques to obtain a high quality product.

At lower temperature (200 - 250oC) conduct the chlorination of the same mixture of chlorine-methanes, but at the same time increase the pressure up to 13 - 130 ATM (80 - 100 ATM). The selectivity of the process for forming the chloroform and carbon tetrachloride 10: 1. The process can be complicated in hardware design/ U.S. Patent N 4927981, class C 07 C 17/22, published. 22.05.90 g/.

Closest to the invention is a liquid-phase process chlorine-methanes, in particular chloroform and carbon tetrachloride/ French Patent N 2547297, class C 07 C 19/06, 17/10, 19/02, published. 11.12.84,/. The feedstock for the process is liquid chlorine and chloromethyl, chlorination conditions: pressure 10 - 25 bar temperature 60 - 90oC, initiation carried out by known methods chemical or photochemical.

The scheme of this process is quite flexible, since it uses a twin site of synthesis allowing to obtain a mixture of methylene chloride - chloroform, chloroform - carbon tetrachloride, but he complicated the security.

The present invention is directed to the development of an improved method of producing chloroform superior quality.

This is achieved by a mixture of chlorine-methanes, obtained by thermal chlorination of methane, after condensation and separation of chlormethyl or methylene chloride enriched "light" impurities, direct to the stage of liquid-phase photochemical chlorination, which is carried out at a temperature of 35 - 45oC and a molar ratio of chlorine - methylene chloride 1:4,0 - 2,0. The above conditions allow more controlled amount of chloroform, thereby chlorination of such impurities as 1,1 - and 1,2 - dichloroethylene, 1,1 - dichloroethane translated them in high-boiling components, which eliminates the need for additional purification of harmacy any reagents before its rectification to obtain chloroform superior quality.

The proposed method was verified in the laboratory as follows: in the column reactor equipped with a thermometer, reflux condenser and a bubbler in the bottom to feed chlorine, downloaded raw materials for chlorination. When the radiation source (the lamp On the function and time. After the operation was determined by the weight of the received harmacy, its composition (chromatographic method). According to the obtained results were evaluated by the efficiency of the process (the degree of conversion of methylene chloride, the selectivity). The invention is illustrated in the following specific example.

Example 1

Charged to the reactor 260 g harmacy composition in wt.%: the methylene chloride 50,48, chloroform 38,81, carbon tetrachloride 8,33, mixture of isomers dichlorethylene 0,235, 2,145 mixture of hydrocarbons of the series C2. When the source of light and a temperature of 25oC start the flow of chlorine. Due to the reaction heat, the temperature rises to 38 - 42oC and maintained at the expense of the return phlegmy from the back of the fridge. Chlorination lead 1 h when submitting chloride 30 g/h, which corresponds to a molar ratio of methylene chloride - chlorine of 3.65: 1. Get 275,6 g of the mixture composition wt. %: light impurities of 0.005, methylene chloride 36,7, chloroform 49,35, carbon tetrachloride 11.0 and "heavy" chlorohydrocarbons number of C22,945. Calculated according to the presented data, the degree of conversion of methylene chloride is 23% while the selectivity of the process 85%. An increase in the yield of chloroform is 35.5%.

Data on chlorination of horsesa different the tx2">

From the presented data it follows that the proposed method for the chlorination of mixtures of which the main component is methylene chloride, allows its chlorination with a given degree of conversion and depends on the number of submitted chlorine (in the table are expressed in molar ratio). The optimal process could be seen as the ratio of the methylene chloride - chloro 4 - 2:1, because the increase in the number of methylene chloride leads to performance degradation node chlorination, and increase the flow of chlorine to reduce the selectivity of the process due to the formation of significant quantities of carbon tetrachloride. The effect of temperature is illustrated by examples 3-3A and 7-7a table, from which it follows that the decrease of temperature leads to a decrease in the conversion of chlorine and up to 50oC reduces the selectivity of the process.

The way to obtain a chloroform liquid-phase chlorination of methylene chloride under photochemical initiation, followed by distillation, characterized in that the chlorination is subjected to a mixture of chlorine-methanes, obtained by thermal chlorination of methane after the removal of her chlormethyl containing 50 to 90% methylene chloride, 45% chlorohydrocarbons C1and up to 25% of chlorohydrocarbons C<

 

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SUBSTANCE: claimed method includes passing of gaseous reaction mixture containing at least one lower alkane and elementary chlorine through catalytic layer. Used catalyst represents geometrically structured system comprising microfiber with diameter of 5-20 mum. Catalyst has active centers having in IR-spectra of adsorbed ammonia absorption band with wave numbers in region of ν = 1410-1440 cm-1, and contains one platinum group metal as active component, and glass-fiber carrier. Carrier has in NMR29Si-specrum lines with chemical shifts of -100±3 ppm (Q3-line) and -110±3 ppm (Q4-line) in integral intensity ratio Q3/Q4 from 0.7 to 1.2; in IR-specrum it has absorption band of hydroxyls with wave number of ν = 3620-3650 cm-1 and half-width of 65-75 cm-1, and has density, measured by BET-method using argon thermal desorption, SAr = 0.5-30 m2/g, and specific surface, measured by alkali titration, SNa = 10-250 m2/g in ratio of SAr/SNa = 5-30.

EFFECT: method of increased yield.

3 cl, 4 ex

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