RU2404953C1 - Method of producing chloroform from methylene chloride - Google Patents

Abstract

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

Description

The invention relates to industrial organochlorine synthesis, and specifically to methods for producing chloroform from carbon tetrachloride (CFC) and methylene chloride (MX).

In accordance with the United Nations Environment Program, CZH, together with a number of other organochlorine compounds, is classified as an ozone-depleting substance and its release as a commercial product is currently discontinued. However, CFCs are produced in significant quantities as a by-product in the production of chloromethanes and tetrachlorethylene. In this regard, the creation of a simple and economical method of processing excess CFCs to obtain a useful product, for example chloroform, is of undoubted interest. Chloroform is a valuable intermediate in large-capacity organic synthesis, including in the production of ozone-depleting chladones, and is used as a solvent.

To date, methods have been developed for the production of chloroform from ChCU, based on the hydrogenation of ChCU by molecular hydrogen or on its interaction with n-paraffins and other hydrocarbons.

Known methods for producing chloroform by hydrogenation of carbon tetrachloride with molecular hydrogen in the liquid phase at elevated temperatures in the presence of platinum-based catalysts with the addition of other platinum group metals on alumina (European patent No. 1201300, 2001; European patent No. 0460138, 1991). The disadvantages of the methods are the complexity of the technology associated with the use of an expensive catalyst containing a platinum group metal, fire and explosive hydrogen at high temperatures, low - 85% and less selectivity for chloroform, as well as the unproductive consumption of chlorine contained in CFCs. At least 25% of the latter is spent on obtaining contaminated with organic substances and not representing commercial value hydrogen gas hydrogen chloride.

Known methods for producing chloroform from CHC without the use of molecular hydrogen. These include a method for producing chloroform and aromatic hydrocarbons chlorinated in the side chain according to RF Patent No. 2107544, 1995. The method involves the use of alkyl aromatic hydrocarbons as a hydrogen source. In a number of patents (RF Patent No. 2107678, 1995; RF Patent 2261759, 2003; RF Patent 2242282, 2003, US Patent No. 2,0203318, 2005, RF Patent No. 2322433, 2008), linear and branched alkanes are proposed to be used as hydrogen donors. In all the proposed methods, along with the target product, chloroform, chlorinated hydrocarbons are formed. The high cost of hydrogen donors, as well as problems with the sale of by-products, limit the scope of possible applications of these technologies to produce pure chloroform. In addition, the high content of resinous substances and abhase hydrogen chloride necessitates additional purification, which dramatically complicates the technology.

Closest to the described is the method proposed in the patent of the Russian Federation No. 2187489, 2002. Chloroform and chloroparaffins are obtained by the reaction of CCl ₄ with n-paraffins or their mixtures in the liquid phase at a temperature of 150-180 ° C and a contact time of 1-8 hours, the presence of a catalyst - a complex of copper chloride with chlorides of quaternary ammonium salts of the general formula R ₃ R'NCl (I) or R ₂ R ' ₂ NCl (II), where R = C ₁ -C ₁₈ is alkyl, R' is C ₁ -C ₁₈ is alkyl or benzyl, or salts of the formula R-CH (NR ₃ ′) CH (NR ₃ ′) -R ″ Cl ₂ (III), where R ″ is H or lower alkyl, and R, R ′ have the indicated higher value. The disadvantage of this method is the use as a donor of hydrogen deficient n-paraffins and the consumption of part of the chlorine to produce chloroparaffins.

The objective of the invention is to provide a selective method for producing chloroform without the use of scarce hydrogen donors.

The problem is solved by a catalytic reaction between CFC and methylene chloride

CCl ₄ + CH ₂ Cl ₂ → 2CHCl ₃

using as catalysts compositions based on copper chloride and quaternary ammonium soda of the general formula R ₃ R'NCl (I) or R ₂ R ' ₂ NCl (II), where R = C ₁ -C ₁₈ is alkyl, R' is C ₁ -C ₁₈ is alkyl, chloralkyl or benzyl. The technical result is achieved by the fact that in the proposed method, chloroform is the only product of the interaction of CFC and methylene chloride. This reaction allows us to simplify the technology by eliminating the use of paraffins as a hydrogen donor, thereby solving the problem of their further utilization and purification of the target product from chloroparaffins. Methylene chloride is produced in the industrial production of chloroform by chlorination of methane as a by-product together with CFCs. The process can be adjusted so that methylene chloride and CFC are formed in a ratio close to 1: 1. This will allow achieving a close to quantitative yield of chloroform in the overall process (methane chlorination + reaction of MX with CFC).

The invention is illustrated by the following examples.

Example 1. Preparation of a catalytic composition.

To prepare the catalytic composition, 180 ml of 96% ethanol are placed in a glass vessel and, with vigorous stirring, a pre-measured amount of powdered reagents is gradually sprinkled with 1 g of anhydrous copper (II) chloride or 1.1 g of its crystalline hydrate and 12 g of tetraethylammonium chloride (TEAC). The solution is stirred at room temperature or slightly heated until the solid components are completely dissolved, while it becomes yellow or light brown. The prepared solution can be stored in a closed vessel with a ground stopper for at least a long time.

Similarly, get the catalysts with the following ammonium salts:

triethylbenzylammonium chloride (TEBAH),

tetrabutylammonium chloride (TBAC),

tetrabutylammonium chloride monohydrate (M-TBAC),

Catamine AB (50% aqueous alkyldimethylbenzylammonium chloride),

tetraethylammonium chloride (TEAC)

tetramethylammonium chloride. (TMAX)

triethyl (chloroethyl) ammonium chloride (TEHEAX)

When using other ammonium salts, their amount is changed in proportion to the increase in molecular weight in comparison with TEA, so that the molar ratio of salt: copper is 8-10: 1.

Example 2

Getting chloroform

The calculated quantities of CHC and MX are mixed in an autoclave. Then, a measured amount of catalyst is also added with stirring. Loading in a standard experiment: 35 ml (47 g) CH ₂ Cl ₃ , 150 ml (240 g) CCl ₄ , 10 ml of the catalyst composition. The resulting solution is 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 clear yellow or tan solution. The reaction mass is dispersed, taking fractions of unreacted MX, chloroform and CFC. The yield of chloroform is 7 ml (10.5 g), which is 22% of the initial CM. Methylene chloride and CHC are re-reacted in subsequent experiments.

The use of the catalyst in amounts outside the selected range is impractical: a decrease leads to a significant decrease in the conversion of reagents, and an increase does not give a measurable positive effect and only increases the consumption of catalyst. Increasing the reaction time to 3-4 hours does not increase the yield of the product, and at 5 or more hours the yield of chloroform decreases and the solution acquires a dark brown color. In examples 3-9, the process of producing chloroform is carried out similarly. The results of the experiments are presented in the table.

Table 1 The results of comparative tests of various catalysts No. Copper concentration g / l Salt: copper molar ratio Nitrogen compound HF yield,% of MX filed note 180 ° C 190 ° C 3 0.1 10 TEBAH 8 10 sample yellow four 0.15 8 TBAH 8 10 yellow 5 0.2 10 M-TBAH 6.5 8 yellow 6 0.5 10 Catamine AB eleven fourteen samples are dark brown, HCl is released 7 0.12 9 TEAC 16 22 samples are transparent, yellowish, no HCl 8 0.25 8 Tmax one 3 yellow 9 0.12 8 TEHEAH 16 24 yellow

To determine the optimal performance of the process, experiments were conducted in which the unreacted feed was recycled. This mode simulates an industrial continuous process with a constant recycle of the reaction mixture into the reactor. The results are described in example 10, 11.

Example 10

To the reaction mass, distilled after carrying out the synthesis of chloroform according to example 1 (183 ml), 2.5 ml of MX, 11 ml of CFC and 10 ml of a solution of the catalyst composition are added. The process is carried out as in example 1. 6.8 ml of chloroform are separated. The operation is repeated 2 more times. The total yield of the target product is 39 g (26.2 ml), which corresponds to 82% of theory based on the consumed MX.

Example 11

The process is conducted as in example 10, but TEHEAX is used as a catalyst. 39.6 g of chloroform are obtained (83.2% of theory).

The best results are achieved by sequentially introducing the catalyst in 2-4 portions, which allows it to maintain a stable concentration in the reaction mass (preferred method). The results of using this technique are presented in examples 12-14.

Examples 12-14.

In all experiments, a solution of the catalytic complex was used, containing, per 100 ml of alcohol, 1 g of copper chloride and 12 g of TEAC, the temperature was 190 ° C. In the first load, 10 ml of the solution of the catalytic complex was introduced per 250 ml of the reaction mixture, then 4 ml each. The duration of the aging of the reaction mass after each boot was 1.5 hours.

table 2 The outputs of chloroform during fractional loading of the catalyst,% of the filed MX molar ratio of CHC: MX Chloroform yield after next loading No. 1st 2nd 3rd 4th 12 6: 1 22 31 38 45 13 2.5: 1 12 eighteen 25 31 fourteen 1.5: 1 10 16 22 27

In this case, the recycling of the reaction mass also allows you to get additional quantities of the target product. For this, in a batch process, 2-3 recycling operations are sufficient. When the process is carried out in continuous mode, this means a significant reduction in the volume of the recycled reaction mass. This embodiment of the method is illustrated in Example 15.

Example 15

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

Example 16

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

A 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 reached faster. This pattern is illustrated by example 17.

Example 17

The process is carried out as in example 15, the temperature is 200 ° C. The yield of chloroform after the third load is 42%, after the 4th - 47%. In the first three downloads, the solution retains a slightly yellow color, after the fourth it acquires a light brown color, remaining transparent. The total yield of reaction by-products (hexachloroethane, tetrachlorethylene and hexachlorobutadiene) is less than 1%.

Thus, when using tetraethylammonium chloride or triethyl (chloroethyl) ammonium chloride as an organic component, the following process conditions are optimal: temperature in the range of 190-200 ° C; the molar ratio of CHC: MX in the range of 4-6; 3-4 times the loading of the catalytic solution of the above composition in the amount of 1/25 of the volume of the reaction mass.

In this case, chloroform can be obtained with a sufficiently high yield (40% or more) and high selectivity (not lower than 95%, 98% achieved).

In the General case, when using the compound R ₃ R'NCl or R ₂ R ' ₂ NCl, where R = C ₁ -C ₁₈ is alkyl, R' is C ₁ -C ₁₈ is alkyl, chloralkyl or benzyl at molar ratios of salt: copper 8-10: 1, the copper concentration is 0.1-0.5 g / l, and the process is carried out at a temperature of 180-200 ° C with a molar ratio of carbon tetrachloride and methylene chloride of 1.5 - 6: 1. The catalyst is added in 2-4 portions after 90-120 minutes each.

Claims (2)

1. A method of producing chloroform by reacting carbon tetrachloride with a hydrogen donor in the presence of a complex of copper chloride with quaternary ammonium salts at an elevated temperature, characterized in that methylene chloride is used as a hydrogen donor, as the quaternary ammonium salts of a compound of the general formula R ₃ R'NCl or R ₂ R ' ₂ NCl, where R = C ₁ -C ₁₈ is alkyl, R' is C ₁ -C ₁₈ is alkyl, chloralkyl or benzyl at molar salt: copper ratios of 8-10: 1, the copper concentration is 0.1 -0.5 g / l, and the process is carried out at a temperature of 180-200 ° C with molar co the ratio of carbon tetrachloride and methylene chloride 1.5-6: 1. 2. The method according to claim 1, characterized in that the catalyst is added in 2-4 portions after 90-120 minutes each.