Method of producing chloroform from methylene chloride

FIELD: chemistry.

SUBSTANCE: hydrogen donor used is methylene chloride, quaternary ammonium salts used are compounds of general formula R3R'NCl or R2R'2NCI, where R=C1-C18 - alkyl, R' - C1-C18 -alkyl, chloroalkyl or benzyl in molar ratio salt: copper equal to 8-10:1, concentration of copper is 0.1-0.5 g/l. The process is carried out at 180-200°C with molar ratio of carbon tetrachloride and methylene chloride equal to 1.5-6:1. The catalyst can be added in 2-4 portions after 90-120 minutes each.

EFFECT: selective method of producing chloroform without using scarce hydrogen donors.

2 cl, 2 tbl, 17 ex

 

The invention relates to chlorinated organic synthesis, specifically a process for the production of chloroform from carbon tetrachloride (Chu) and methylene chloride (MX).

In accordance with the Programme of the United Nations environmental Chu together with a number of other organochlorine compounds classified as ozone depleting substances and its release as a commercial product now discontinued. However, Chu is formed in large quantities as a by-product in the manufacture of chlorine-methanes and tetrachloroethylene. In this regard, the creation of a simple and economical method for processing excess of Chu obtaining a useful product, such as chloroform, is of undoubted interest. Chloroform is a valuable intermediate in heavy organic synthesis, including in obtaining ozononerazrushayushchiy halocarbons, and is used as a solvent.

To date, methods have been developed to obtain the chloroform from Chu, based on the hydrogenation of Chu molecular hydrogen and its interaction with n-paraffins and other hydrocarbons.

Known methods for producing chloroform by hydrogenation of carbon tetrachloride by molecular hydrogen in the liquid phase at elevated temperature in the presence of catalysts based on platinum, with the addition of other metal is platinum on alumina (European patent No. 1201300, 2001; European patent No. 0460138, 1991). The disadvantages of this method is the complexity of the technology associated with the use of an expensive catalyst containing a platinum group metal, flammable and explosive hydrogen at high temperatures, low of 85% and less selectivity for the chloroform, as well as unproductive consumption contained in Chu chlorine. Not less than 25% last spent on getting contaminated with organic substances and not representing a commercial value abgasnorm of hydrogen chloride.

Known methods for producing chloroform from Chu without the use of molecular hydrogen. These include the way to obtain chloroform and chlorinated in the side chain of aromatic hydrocarbons according to the Patent of Russian Federation №2107544, 1995. The method involves the use of a source of hydrogen alkylaromatic hydrocarbons. In a number of patents (Patent RF №2107678, 1995; RF Patent 2261759, 2003; RF Patent 2242282, 2003, U.S. Patent No. 0203318, 2005, Patent RF №2322433, 2008) as the hydrogen donors are encouraged to use linear and branched alkanes. All the proposed methods along with the target product - chloroform formed chlorinated hydrocarbons. The high cost of hydrogen donors, as well as problems with the sale of by-products limit the scope of possible application of these technologies to produce pure chlorine is form. In addition, high content of tar and abgasnorm of chloride causes the need for additional purification, which greatly complicates the technology.

The closest to this is the method proposed in the patent of Russian Federation №2187489, 2002. Chloroform and chlorinated paraffin wax obtained by the reaction of CCl4with n-paraffins or mixtures thereof in the liquid phase at a temperature of 150-180°C. and the contact time between 1-8 hours, in the presence of a catalyst complex of chloride copper chloride Quaternary ammonium salts of the General formula R3R NCl (I) or R2R'2NCl (II), where R=C1-C18- alkyl, R' - C1-C18- alkyl or benzyl, or a salt of the formula R-CH(NR3')CH(NR3')-R"Cl2(III)where R ' is H or lower alkyl, and R, R' have the above values. The disadvantage of this method is the use as a donor of hydrogen deficient n-paraffins and consumption parts of chlorine to obtain chlorinated paraffin wax.

Object of the present invention is to provide a selective method of producing chloroform without use of scarce donor of hydrogen.

The problem is solved by the catalytic reaction between Chu and methylene chloride

CCl4+CH2Cl2→2CHCl3

using as catalysts compositions based on copper chloride and Quaternary ammonium promote the General formula R3 R NCl (I) or R2R'2NCl (II), where R=C1-C18- alkyl, R' - C1-C18- alkyl, chloroalkyl or benzyl. The technical result is achieved by the fact that in the proposed method, the chloroform is the only product of the interaction of Chu and methylene chloride. This reaction allows to simplify the technology at the expense of abandoning the use of paraffin as a donor of hydrogen, thereby solves the problem of their further utilization and purification of the target product of chlorinated paraffin wax. Methylene chloride is formed in the industrial production of chloroform by the chlorination of methane as a by-product together with Chu. The process can be adjusted so that the methylene chloride and Chu were formed in a ratio close to 1:1. This will be achieved in the overall process (chlorination of methane + reaction MX with Chu) output chloroform, close to quantitative.

The invention is illustrated by the following examples.

Example 1. The preparation of the catalytic composition.

For the preparation of the catalytic composition in a glass vessel placed in 180 ml of 96% ethanol and with vigorous stirring gradually sprinkled with a pre-measured amount of powdered reagents 1 g of anhydrous copper chloride (II) or 1.1 g of crystalline and 12 g of tetraethylammonium (TEACH). The mortar mix is at room temperature or with slight heating until complete dissolution of the solid components, however, he gets a yellow or light brown color. The prepared solution can be stored in a closed vessel with a glass stopper, at least for a long time.

Similarly receive the catalysts with the following ammonium salts:

triethylmethylammonium-chloride(TEBAH),

tetrabutylammonium chloride (TBAH),

monohydrate tetrabutylammonium chloride (M-TBAH),

katamin AB (50% aqueous alkyldimethylbenzylammonium),

tetraethylammonium (TEACH)

Tetramethylammonium. (TM)

triethyl(chloroethyl)ameriglide (HAHAAH)

When using other salts of ammonium their number is changed in proportion to the increase in molecular weight compared to the tea so that the molar ratio of salt:copper was 8-10:1.

Example 2.

Receiving chloroform

The calculated amount of Cho and MX stirred autoclave. Then with stirring, add a measured amount of catalyst. Loading standard experiment: 35 ml (47 g) CH2Cl3150 ml (240 g) CCl410 ml of the catalytic composition. The resulting solution was placed in an autoclave made of stainless steel and equipped with a magnetic stirrer and pressure gauge, and incubated for 2 hours at a temperature of 190°C. the Reaction mass after the reaction is a transparent yellow or is it brown solution. The reaction mass is dispersed by taking the fraction of unreacted MX, chloroform, Chu. The output of chloroform is 7 ml (10.5 g), which is 22% of the original HMM. Methylene chloride, Chu re-injected into the reaction in the subsequent experiments.

The use of the catalyst in amounts outside of the selected impractical: the reduction leads to a significant decrease of conversion of the reactants, and the increase does not give a measurable positive effect and only increases the consumption of the catalyst. Increasing the reaction time up to 3-4 hours does not increase product yield, and at 5 hours or more output chloroform is reduced and the solution becomes dark brown in color. In examples 3-9 process chloroform are similar. The results of the experiments presented in the table.

Table 1
The results of comparative tests of various catalysts
No.Copper concentration g/lThe molar ratio of salt: copperA compound of nitrogenExit HF, % filed MXnote
180°C190°C
30,110TABAH810the yellow sample
40,158TBH810yellow
50,210M-TBH6.58yellow
60,510Katamin AB1114samples of dark brown, highlighted HCl
70,129TEACH1622samples of transparent, yellowish, selection HCl not observed
80,258 TM13yellow
90,128HAHAAH1624yellow

To determine the optimum process conducted experiments in which it was implemented recycling the unreacted raw materials. This mode simulates an industrial continuous process with constant recycling of the reaction mass in the reactor. The results described in example 10, 11.

Example 10.

To the reaction mass removed after carrying out the synthesis of chloroform according to example 1 (183 ml) add 2.5 ml MX, 11 ml Chu and 10 ml of a solution of the catalytic composition. The process is conducted as in example 1. Separate 6.8 ml of chloroform. Operation repeat 2 more times. The total yield of the target product is 39 g (26.2 ml), which corresponds to 82% of theory calculated on spent MX.

Example 11.

The process is conducted as in example 10, but as the catalyst used HAHAAH. Receive 39.6 g of chloroform (83.2% of theory).

The best results are achieved with serial input catalyst 2-4 portions, allowing you to maintain a stable concentration in the reaction mass (preferred method) the Results of using this technique is presented in examples 12-14.

Examples 12-14.

In all experiments was used a solution of the catalytic complex containing, per 100 ml of alcohol, 1 g of copper chloride and 12 g TEACH, the temperature was 190°C. In the first boot was introduced 10 ml of a solution of catalyst complex per 250 ml of the reaction mixture, followed by 4 ml. Duration of incubation of the reaction mixture after each load was 1.5 hours.

Table 2
The outputs of chloroform at fractional loading of the catalyst, % filed MX
the molar ratio of Cho:MHThe output of chloroform after the next boot
No.1st2nd3rd4th
126:122313845
132.5:112182531
141.5:110162227

In this case, the recycling of the reaction mass, you can also receive an additional amount of the target product. For this periodic process is fairly 2-3 recycling operations. When carrying out the process in a continuous mode, this represents a significant decline reciclagem the reaction mass. This variant of the method illustrated in example 15.

Example 15.

The process is conducted as in example 12, but after separation of the chloroform, the reaction mass (220 ml) is returned to the reactor. Next, the process again lead as in example 12. The total yield of chloroform is 91.4% of theory.

Example 16

The process is conducted as in example 15, but after separation of the chloroform, the reaction mass is returned to the reactor, adding to the initial mixture of Chu and MX to the original volume. Next, the process again lead as in example 15. The total yield of chloroform is 84.6% of theory.

Temperature in the range of 185-205°C has little effect on the final yield of the product, but at a higher temperature, it is achieved faster. This pattern is illustrated in example 17.

Example 17.

The process is conducted as in example 15, the temperature is 200°C. the Output x is orapharma after the third load is 42%, after the 4th - 47%. During the first three downloads solution preserves the slightly yellow color, after the fourth gets a light brown color, while remaining transparent. The total yield of by-products of the reaction (hexachloroethane, tetrachloroethylene, and Hexachlorobutadiene) is less than 1%.

Thus, when using as the organic component of the catalyst tetraethylammonium or triethyl(chloroethyl)ameriglide optimal is the following process: temperature in the range of 190-200°C; molar ratio Cho:MX within 4-6; 3-4-fold loading of the catalyst solution of the above composition in an amount from 1/25 volume of the reaction mass.

While chloroform can be obtained with high yield (40%) and high selectivity (at least 95%, achieved 98%).

In General, when using a connection R3R NCl or R2R'2NCl, where R=C1-C18- alkyl, R' - C1-C18- alkyl, chloroalkyl or benzyl when the molar ratio of salt:copper 8-10:1, the copper concentration is 0.1-0.5 g/l, and the process is conducted at a temperature of 180-200°C at a molar ratio of carbon tetrachloride and methylene chloride 1,5 - 6:1. The catalyst add 2-4 portions through 90-120 min each.

1. The method of producing chloroform by reacting carbon tetrachloride with the donor water the ode in the presence of a complex of copper chloride with Quaternary ammonium salts at elevated temperature, characterized in that as a donor of hydrogen using methylene chloride as the Quaternary ammonium salts of the compounds of General formula R3R NCl or R2R'2NCl, where R=C1-C18- alkyl, R' - C1-C18- alkyl, chloroalkyl or benzyl when the molar ratio of salt: copper 8-10:1, the copper concentration is 0.1-0.5 g/l, and the process is conducted at a temperature of 180-200°C at a molar ratio of carbon tetrachloride and methylene chloride 1,5-6:1.

2. The method according to claim 1, characterized in that the catalyst add 2-4 portions through 90-120 min each.



 

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