JPS623132B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for producing 2,3,4-trichloro-
An improved process for the production of 2,3-dichloro-1,3-butadiene by dehydrochlorination of 1-butene.

Since chlorinated hydrocarbons such as 2,3,4-trichloro-1-butene form a two-phase system with aqueous alkaline solutions, the dehydrochlorination reaction occurs very slowly even with vigorous stirring. This is because reactions can only occur at phase interfaces. Increased reaction rates can be achieved by transferring the compound to be dehydrochlorinated and the hydrogen chloride acceptor into a homogeneous phase. Methods of this kind are described in British patents no. 946014, no. 1048510 and no. 1084742, and in German patent application publication no.
No. 2204708, and U.S. Pat.
Described in No. 3622641. According to the second of these two US patents, for example, the dehydrochlorination reaction is carried out for this purpose in the presence of catalytic amounts of cyclic polyethers derived from dihydric phenols. Other known methods operate at elevated temperatures to increase the reaction rate. See, for example, German patent applications no. 1217947 and no. 2113858.

British Patent No. 951312 describes the use of amine-containing catalysts, while US Patent No. 3514496
- describes the use of catalysts containing copper salts in the production of dichlorobutadiene.

Unfortunately, all of the methods listed above have some serious drawbacks.

It is difficult to achieve complete conversion, separate dichlorobutadiene, and achieve high yields. The formation of polymeric precipitates considerably complicates monomer separation and reduces yields.
According to GB 1048510, known stabilizers are not able to completely suppress the spontaneous and undesired polymerization of dichlorobutadiene during its preparation.

Considerable progress has been made in catalytic dehydrochlorination reactions by the introduction of phase transfer catalysts, for example as described in German Patent No. 1618790 for the production of 2-chloro-1,3-butadiene from 3,4-dichlorobutatene. It was done. 2 promoted by ammonium, phosphonium or sulfonium salts
Reactions between substances in a phase system are generally ``phase transfer catalysts.''
It is called. Such a reaction was first described in the literature in 1965 (M. Makosza and B.
Serafinowa, Rosz. Chem. vol. 39, 1223, 1401,
pp. 1595, 1799, 1805 (1965)).

A comprehensive description of this new form of catalyst is given in the journal Angew.Chem., volume 86, pages 187 et seq. (1974).

Unfortunately, attempts to produce 2,3-dichloro-1,3-butadiene by the process described in German Patent No. 1,618,790 have not been successful. Significant amounts of polymer precipitate are formed during the reaction even in the presence of strong inhibitors such as phenothiazine.

The reason behind the formation of these large amounts of polymer precipitates is the great affinity of 2,3-dichloro-1,3-butadiene for polymerization. The polymerization rate of 2,3-dichloro1,3-butadiene is 2000 times faster than that of isoprene (see German Patent Application No. 2204708). The stabilization of this monomer against undesired spontaneous polymerization under the conditions prevailing during its preparation is therefore a difficult problem to solve.

According to the invention, the solution to this problem is based on the following discovery.

The dehydrochlorination of 2,3,4-trichloro-1-butene must be carried out over a range of temperatures without any significant fluctuations.

Therefore, 2 of the two reaction components (2,3,4-trichloro-1-butene/alkali metal hydroxide)
The phase system must be introduced first, followed by the addition of an aqueous solution of the phase transfer catalyst with careful control of the temperature; highly concentrated solutions of the catalyst must be avoided.

For each reaction mixture, there is an optimum amount of catalyst that is preferably used. It can be determined by simple tests and is dominated primarily by the catalyst itself used and, to a lesser extent, by other reaction components.

The presence of oxygen is advantageous in the production of 2,3-dichloro-1,3-butadiene. In addition, the polymerization of monomers dissolved in small amounts in the alkaline aqueous phase may be suitably inhibited by inhibitors soluble in that phase.

The present invention involves adding an aqueous solution of 0.1 to 50% by weight of a phase transfer catalyst to a mixture of 2,3,4-trichloro-1-butene and an alkali metal hydroxide;
Per 100 parts by weight of 4-trichloro-1-butene
The dehydrochlorination reaction is carried out at −10 to +60° C. using 0.05 to 10 parts by weight of catalyst, oxygen, and optionally the presence of a combination of inhibitors soluble primarily in the monomer phase and inhibitors soluble primarily in the aqueous phase. The present invention relates to a process for the production of 2,3-dichloro-1,3-butadiene by dehydrochlorination of 2,3,4-trichloro-1-butene with an aqueous solution of an alkali metal hydroxide in the presence of a phase transfer catalyst.

Known compounds suitable for use as catalysts are described, for example, in Angewante Chemie, Vol. 86, p. 187 et seq. (1974), in German Patent No. 1618790 and in German Patent Application No. 1909952. Among the sulfonium, phosphonium and ammonium compounds that can be used, phosphonium and ammonium compounds are preferred. The compounds in question are in particular peralkylated phosphonium and ammonium hydroxides or tributylhexadecyl ammonium bromide,
It is a halide with long chain alkyl substituents. The catalyst is carefully added to the reaction mixture in the form of an aqueous solution to avoid excessive local concentration of the catalyst. The solution used is 0.1-50% by weight, preferably 0.5
Contains ~10% catalyst by weight.

The amount of catalyst required for the dehydrochlorination reaction is governed to a large extent by the activity of the catalyst. For highly active catalysts, adding a small amount of 0.05 part by weight is sufficient, but for less active catalysts, 2, 3, 4-
Amounts of up to 10 parts by weight per 100 parts of trichloro-1-butene may be used.

Reaction parameters may be chosen such that the smallest possible amount of catalyst can be used, since phase separation generally occurs more easily the smaller the amount of catalyst used when the reaction is completed.

The emulsion formed by the catalyst can be broken upon completion of the reaction by addition of known emulsion-breaking substances, for example by addition of an electrolyte, by addition of an acid or by dilution.

The dehydrochlorination reaction can be carried out at a temperature of -10 to +60°C, preferably a temperature of -5 to +25°C.

The amount of water present in the reaction mixture during the process of the invention is not critical. The amount of water required to dissolve the alkali metal halide formed is considered a lower limit. The upper limit is determined by the dilution of the alkali metal hydroxide used. As the concentration of alkali metal hydroxide decreases, the reaction rate also decreases. Therefore, it is desirable not to fall below the limit of 3% by weight alkali metal hydroxide in the aqueous phase.
At the completion of the reaction, the aqueous phase is 2,3-dichloro-1,3
- Since after separation of the butadiene the solution contains on average about 0.05% by weight of monomer, it is advantageous to keep the amount of water used as low as possible in order to avoid reducing the yield.

A ratio of 120 to 200 parts by weight of water to 100 parts by weight of 2,3,4-trichloro-1-butene is preferred. The concentration of the alkali metal hydroxide solution used amounts to 3-50% by weight, preferably 10-30% by weight. 2・
The molar ratio of 3,4-tri-chloro-1-butene to alkali metal hydroxide will be from 1:1.05 to 1:1.5.

Sodium hydroxide is preferably used as the alkali hydroxide.

2,3-dichloro-1,3 produced during the reaction
- Butadiene is generally treated with a known polymerization inhibitor, such as phenothiazine and N-nitrosodiphenylamine, with a
It is stabilized against spontaneous polymerization by addition in an amount of 10000 ppm, preferably in an amount of 500 to 1000 ppm.

When separating the dichlorobutadiene, the phenothiazine remains in the monomer phase, and they are apparently not sufficiently stabilized against polymerization, so a small amount of monomer dissolved in the aqueous phase will absorb a significant amount of water and monomeric dichlorobutadiene. It tends to produce very flaky bulky polymer deposits that contain.

These flakes float in the aqueous and monomer phases and, if present in sufficient quantities, prevent the development of a line of separation between the two phases. Generally, overtesting does not work in practice because the monomer-containing flakes are sticky and block the pores of the filter in a short period of time.

In one embodiment of the method of the invention, therefore, in addition to the phenothiazine, a water-soluble polymerization inhibitor is used to prevent spontaneous polymerization of monomers dissolved in the aqueous phase. Examples of water-soluble polymerization inhibitors used for this purpose include 4-tert-butylpyrocatechol,
Known water-soluble inhibitors such as 2,6-di-tert-butyl-p-cresol or dialkylated hydroxylamines such as diethylhydroxylamine are included. The water-soluble inhibitor, preferably diethylhydroxylamine, is
It is used in an amount of 5000 ppm, preferably in an amount of 250 to 300 ppm (relative to 2,3,4-trichloro-1-butene).

In order to avoid the formation of polymeric precipitates, the process of the invention is carried out in the presence of oxygen, for example atmospheric oxygen. Dehydrochlorination reactions generally contain 99.9% of the starting compound
The above conversion was performed, and the resulting 2.3-
0.1% by weight in dichloro-1,3-butadiene
The following 2,3,4-trichloro-1-butenes exist. Depending on whether the process of the invention is carried out continuously or in batches, substantially complete conversion of the starting compounds can be achieved by appropriate selection of reaction and residence times. . The yield of 2,3-dichloro-1,3-butadiene is usually 98% or more of the theoretical yield, generally 98.5 to 99.5%.

2,3-dichloro-1,3-butadiene is separated by phase separation in a separate vessel. If the process is carried out continuously, dichlorobutadiene is preferably separated in horizontal separator bottles. In order to achieve rapid phase separation, it is particularly advantageous to pass the reaction mixture through a glass wool filter before separation.

In addition, other known separation techniques such as extraction and distillation can also be used.

2,3-Dichloro-1,3-butadiene can be used as an adhesive, especially in the production of polymers used for bonding rubber to metal. It can be used as a comonomer in the production of polychlorobrene with low crystallinity, which results in rubbers with excellent elasticity even at low temperatures.

The percentages given in the following examples are percentages by weight. The conversion rate of 2,3,4-trichloro-1-butene was determined by gas chromatography.

Comparative Example A (without phase transfer catalyst) Caustic soda in 500 g of 2,3,4-trichloro-1-butene (TCB) and 650 g of water in a cylindrical three-glass flask equipped with a stirrer and a dropping funnel. 162.5g of solution was added at 15°C with vigorous stirring. 0.5 g of phenothiazine and 0.5 g of diethylhydroxylamine were added to the resulting 2.3
-Added as a stabilizer for dichloro-1,3-butadiene (DCB). After 5 days, the TCB used
Only 53.3% by weight of the amount was replaced by DCB.

Comparative Example B (Process according to German Patent No. 1618790) 750 g of water, 13.75 g of caustic soda and 0.5 g of catalyst (bis-(2-hydroxypropyl)-benzylhexadecyl ammonium bromide) are added to the apparatus described in Example 1. Ta. After replacing the air present in the device with nitrogen, the internal temperature will decrease.
500 g of TCB was added dropwise while stirring vigorously for 1 hour to avoid raising the temperature to 10°C. Immediately after the start of the addition, bulky, flaky polymer precipitates formed in the reaction mixture. Internal temperature increased to 15°C. After 5 hours, 94.5% of the TCB used had reacted. After 9 hours, 0.1% of the TCB used was still unreacted. Then the reaction was stopped. The liquid contained many flakes which complicated phase separation to a considerable extent. The reaction mixture had to be filtered, which took several hours as the polymer precipitate continually clogged the filter. The precipitate was collected, squeezed dry, and then dried in a vacuum oven at 120° C. to constant weight. 12.4 g of solid polymer precipitate was weighed out, corresponding to a DCB yield of 3.2% of the theoretical yield. 278 g of monomer DCB were obtained, corresponding to a yield of 72.1% of the theoretical yield.

Comparative Example C (using phenothiazine in the process according to German Patent No. 1618790) 750 g of water, 137.5 g of caustic soda, catalyst (bis-
(2-Hydroxypropyl)-benzylhexadecyl ammonium bromide) and 0.5 g of phenothiazine were added into the apparatus described in Example 1. After replacing the air existing in the device with nitrogen, set the temperature to 1 to prevent the internal temperature from exceeding 10℃.
Drop 500g of TCB while stirring vigorously. Immediately after the start of the addition, a bulky, flaky polymeric precipitate formed in the reaction mixture. Internal temperature increased to 15°C. After 9 hours, 99.9% of the TCB used had reacted, so the reaction was stopped. The liquid contained many flakes that prevented phase separation. The reaction mixture was filtered, but this took several hours as the polymer precipitate continually clogged the filter. The precipitate containing a large amount of DCB was collected, squeezed and dried, and then dried in a vacuum dryer at 120° C. to constant weight. 11.7 g of solid polymer precipitate was obtained. It is 3.0% of the theoretical yield
Corresponds to DCB yield. The yield of monomeric DCB was lower than 90% of the theoretical yield.

Example 1 In a test device of the type described in the comparative example, 0.5 g of phenothiazine is contained in dissolved form.
500 g of TCB was added to a solution of 162.5 g of caustic soda and 1.0 g of diethylhydroxylamine.

After cooling to 10° C., 10 g of catalyst (tributylhexadecylphosphonium iodide) in the form of a 5% aqueous solution was added over 30 minutes with vigorous stirring. After the catalyst had been added, stirring was continued at 15°C. After 36 hours of reaction time, DCB was still
Contained 0.09% TCB. The reaction was stopped. Polymeric DCB did not accumulate during phase separation. 383.7g of DCB was separated, which is the theoretical yield.
Corresponding to a yield of 99.5%.

Example 2 As in Example 1, 500 g of TCB containing 0.5 g of phenothiazine and 0.2 g of N-nitrosodiphenylamine in dissolved form are added to a solution of 137.5 g of caustic soda and 0.5 g of diethylhydroxyamine in 1000 ml of water. Ta.

After cooling to 10 DEG C., 25 g of catalyst (bis-(2-hydroxypropyl)-methylhexadecyl ammonium iodide) in the form of a 1% aqueous solution were added over a period of 45 minutes. After the catalyst had been added, stirring was continued at 15°C. After a reaction time of 7 hours, the reaction was stopped. DCB contained less than 0.1% TCB. No DCB of the polymer accumulated during phase separation.
The slight haze of DCB could be removed by adding a small amount of anhydrous magnesium sulfate.
378.4g of DCB was isolated, which is 98.1% of the theoretical yield.
corresponds to a yield of

Example 3 As in Example 1, 500 g of TCB containing 0.5 g of phenothiazine in dissolved form were added to a solution of 137.5 g of caustic soda and 0.5 g of diethylhydroxylamine in 1000 ml of water.

After cooling to 10° C., 2.5 g of catalyst (bis-(2-hydroxyethyl)-oleylbenzylammonium chloride) in the form of a 0.5% aqueous solution was added dropwise over 45 minutes with vigorous stirring. Stir is 10
Continued for 13 hours at °C. The reaction has stopped. of polymer
DCB did not accumulate during phase separation. The slight haze of DCB could be removed by treating it with anhydrous magnesium sulfate.
377.9g of DCB was isolated, which is 98.0% of the theoretical yield.
corresponds to a yield of

Example 4 In the test apparatus described in Example 1, 500 g of TCB containing 0.5 g of phenothiazine in dissolved form
was added to 1000ml of water and 137.5g of caustic soda.
After cooling to 8° C., 19 g of a catalyst (tributylhexadecyl ammonium bromide) in the form of a 10% aqueous solution was added dropwise over 45 minutes with vigorous stirring.
After the catalyst had been added, stirring was continued at 15°C. After 20 hours reaction time, DCB is still TCB 0.06%
It contained. The reaction was stopped. Polymer flake DCB did not accumulate during phase separation.
DCB isolated 381.2g, which is 98.9g of the theoretical yield.
% yield.

Example 5 Caustic soda was prepared in a cylindrical 25-glass container equipped with an internal cooling coil and a propeller agitator.
1.925Kg was dissolved in 14.0Kg of water followed by TCB7.0 containing 7g of phenothiazine in dissolved form.
Kg was added. The mixture was cooled to 8°C and then stirred vigorously (the speed of the stirrer was approx.
10.5 g of catalyst (bis-(2-hydroxypropyl)-benzylhexadecyl ammonium bromide) in the form of a 1% aqueous solution were added dropwise over a period of 80 minutes (600 rpm). The temperature did not exceed 10°C. After the reaction subsided, stirring was continued at 14°C. After 7 hours, the residual TCB content was less than 0.1% and the reaction was stopped. 5.280 Kg of pure DCB and 180 ml of flaky intermediate layer containing DCB were obtained during the separation. The middle layer was subjected to steam distillation, yielding an additional 0.105 Kg of DCB. Thus, the yield was 99.8% of the theoretical yield.

Example 6 The procedure was the same as Example 5, except that an additional 10.5 g of diethylhydroxylamine was added to the alkaline aqueous solution. Upon completion of the reaction and after separation of the phases, the reaction mixture was passed through a glass wool filter. 5.340Kg of DCB was isolated, corresponding to a yield of 98.9% of the theoretical yield.

Claims (1)

[Claims] 1. An aqueous solution of 0.1 to 50% by weight of a phase transfer catalyst is 2.
In addition to the mixture of aqueous solution of 3,4-trichloro-1-butene and alkali metal hydroxide, 2,3,4
-0.05 per 100 parts by weight of trichloro-1-butene
A process for producing 2,3-dichloro-1,3-butadiene, characterized in that the reaction is carried out in the presence of oxygen at a temperature of -10 to +60°C using ~10 parts by weight of a catalyst. 2. The process according to claim 1, wherein the reaction is carried out in the presence of a combination of at least one inhibitor soluble primarily in the monomer phase and at least one inhibitor soluble primarily in the aqueous phase. 3. Process according to claim 1 or 2, in which phenothiazine and/or N-nitrodiphenylamine is used as inhibitor combination with diethylhydroxylamine. 4. The method according to any one of claims 1 to 3, wherein the reaction temperature is -5 to +25°C. 5 The molar ratio of alkali metal hydroxide:2,3,4-trichloro-1-butene is 1.05:1 to 1.5:1
The method according to any one of claims 1 to 4. 6. The method according to any one of claims 1 to 5, wherein 0.5 to 10% by weight of an aqueous catalyst solution is added. 7. The method according to any one of claims 1 to 6, wherein the alkali metal hydroxide is sodium hydroxide.