JPS642100B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an industrially advantageous method for producing 2,3-dichloropropionitrile.

2,3-dichloropropionitrile is an industrially useful compound, and is used, for example, as a raw material for polymeric compounds and as a raw material for amino acids, agricultural medicines, and the like.

2,3-dichloropropionitrile is usually produced by blowing chlorine gas into an acrylonitrile liquid phase in the presence of a catalyst and distilling and purifying the resulting reaction solution. As a catalyst, inorganic catalysts such as baking soda and sodium hydrogen phosphate,
Organic catalysts such as pyridine, quinoline, and dimethylformamide are known, and industrially, organic catalysts, especially pyridine, are known as advantageous catalysts.

A method for producing 2,3-dichloropropionitrile by a chlorination reaction of acrylonitrile in a liquid phase using pyridines as a catalyst is described by Angewante, Hemi-
(Angew, chem,) Vol. A60, p. 311 (1948), Zhur,
Obshch, Khim) vol. 28, p. 139 (1958) Journal of Organism, Chemistry (J,
orgChem, ) vol. 26, p. 2324 (1961).

However, in these conventionally known methods, unless a large amount of expensive pyridine is used, which is about 15 to 30% by weight based on acrylonitrile, rapid exothermic phenomena occur, and 2,3-dichloropropylene is not used. Since pionitrile could not be obtained, there were many problems from an industrial standpoint. That is, in the known method, since pyridine is present at a high concentration in the reaction solution after the reaction, if the reaction solution is heated as it is for distillation, the dehydrochlorination reaction of 2,3-dichloropropionitrile will occur. Therefore, it is usually necessary to remove pyridine by washing the reaction solution with water before distillation, and during washing, 2,3
- Dichloropropionitrile is also partially dissolved in the aqueous layer, resulting in a decrease in the yield of 2,3-dichloropropionitrile, and as a further problem, it becomes difficult to treat wastewater containing bad odor containing pyridine.

The present inventors found that even if a pyridine-based catalyst was used,
2, 3 which are industrially advantageous because they do not mix in the reaction solution and are easy to separate, so there is no need to wash the reaction solution with water before distillation.
-As a result of intensive research into the production method of dichloropropionitrile, we found that a solid containing a pyridine group or its quaternary salt has an activity equivalent to or greater than that obtained when the same amount of pyridine compound is used alone. By using a polymer compound like this as a catalyst,
The above problem was solved.

That is, the present invention provides a method for producing 2,3-dichloropropionitrile by a chlorination reaction of acrylonitrile, which is characterized in that acrylonitrile is chlorinated in the presence of solid polyvinylpyridines. This is a method for producing chlorpropionitrile.

The polyvinylpyridines used in this method are:
A polymer compound containing a pyridine group or a quaternary salt thereof, such as vinylpyridines such as 4-vinylpyridine and 2-vinylpyridine, 2-vinyl-6
- Homopolymers obtained by homopolymerization of alkylvinylpyridines such as methylpyridine and 2-vinyl-5-ethylpyridine, or copolymers and crosslinked polymers obtained by copolymerization with styrene, acrylonitrile, and divinylbenzene. It also includes those made by reacting the pyridine residues of these polymers with an alkylating agent to form quaternized ammonium salts.

These polymeric compounds such as vinyl pyridines used in the method of the present invention are commercially available and easily obtained, and when used in the method for producing 2,3-dichloropropionitrile, they have a high activity as a catalyst. Since it is insoluble in the reaction solution, it can be easily separated from the reaction solution. In this method, it is preferable to use the polyvinylpyridine solid catalyst described above in a molar ratio of 0.5 to 20% based on pyridine groups based on acrylonitrile. If it is less than 0.5%, the reaction rate is too low to be practical, but there is no need to use a large amount of polyvinylpyridine at a molar ratio of 20% or more. A single polymer of polyvinyl pyridines may be used, or a mixed catalyst selected from each polyvinyl pyridine may be used. In addition to polyvinyl pyridines, solid alkaline earth metal salts that do not dissolve in the reaction solution can also be used in a molar ratio of 0.5 to 10% based on acrylonitrile. Calcium carbonate is a particularly preferred cocatalyst and contributes to increased yield.

Since the polyvinyl pyridine used in this method is a solid catalyst, the catalyst is solidified in a packed bed, and the reaction solution is continuously passed through and circulated while blowing chlorine into acrylonitrile charged in a separate reactor. The reaction can be completed in the fixed bed.

In this method, the chlorination reaction can be made mild and the reaction can be easily controlled. It is also possible to complete the reaction in a suspended fluidized bed by blowing chlorine into a reactor containing acrylonitrile and polyvinylpyridine, and after the reaction is completed, the catalyst is separated from the reaction solution and reused.

The chlorination reaction apparatus for blowing chlorine into acrylonitrile used in the method of the present invention is preferably an acid-resistant reaction apparatus equipped with a stirrer, a thermometer, a chlorine injection pipe, a reflux condenser, and a cooling jacket or cooling coil.

The chlorination reaction temperature is preferably 10°C to 60°C, particularly 20°C to 50°C. If the reaction temperature is lower than 10°C, the reaction rate will be low, and even if chlorine is introduced, a large proportion will escape from the system without reacting. Furthermore, if the reaction temperature is higher than 60° C., undesirable phenomena such as an increase in the amount of by-products of tar-like substances tend to occur.

Since this reaction is an exothermic reaction, when the reaction is completed by circulating the chlorination reaction liquid through the fixed bed catalyst, it is easy to control the ratio by changing the amount of reaction liquid circulated through the fixed bed. When the reaction is completed in a fluidized bed, the rate is appropriately selected and controlled depending on the rate of chlorine introduction and the heat removal capacity of the reactor. The time required to complete the reaction depends on the reaction temperature, but is usually in the range of several hours to several tens of hours, and chlorine is introduced in an amount of about 1 to 1.5 times the mole of acrylonitrile. The end point of chlorine introduction due to completion of the reaction can be easily determined by the generation of exhaust gas (excess chlorine), lap analysis on a gas chromatograph, etc.

After the chlorination reaction is complete, remove trace amounts of unreacted chlorine by passing nitrogen, air, etc. into the reaction solution.
If polyvinylpyridine is separated from the reaction solution and distilled, highly pure 2,3-dichloropropionitrile can be obtained in high yield.

As described above, the use of polyvinylpyridines in the present method allows easier solid-liquid separation than the crude 2,3-dichloropropionitrile reaction solution obtained by liquid-phase chlorination reaction of acrylonitrile. There is no need to remove the catalyst by washing with water, unlike crude 2,3-dichloropropionitrile obtained using a large amount of pyridine as in the past, and there is no need to remove the catalyst using the same amount of pyridine. The desired product was obtained, and the effect of the method of the present invention is significant.

Examples are shown below.

Example 1 531 g of acrylonitrile and 20 g of calcium carbonate were placed in a reactor equipped with a cooling jacket and equipped with a reflux condenser and a stirrer, and chlorine was added while stirring.
The reaction solution blown at a rate of 98 g/Hr was continuously introduced into the upper part of the column packed with 200 g of poly-4-vinyl pyridine (Koei Kagaku Co., Ltd. product, No. KOEI-6500) into a separately provided packed tower. The reaction was completed over a period of 8 hours by circulating the liquid through the solution. The total amount of blown chlorine is 11 moles, and the liquid temperature in the reactor is 30
It was kept externally cooled to around ℃. After the chlorine injection was completed, the circulation of the reaction liquid to the packed column was stopped and the reaction liquid was collected in the reactor. Dechlorination was carried out for 2 hours by blowing nitrogen into the reactor. Calcium carbonate was removed to obtain 1150 g of reaction mass. As a result of analyzing the reaction mass,
The purity of 2,3-dichloropropionitrile was 98.1%. (Yield 98.0% vs. acrylonitrile) Example 2 Acrylonitrile was added to the chlorination reactor of Example 1.
531g, 54g of 4-vinylpyridine polymer crosslinked with divinylbenzene (0.5 mol in terms of pyridine group,
KOEI-6523, DVB/4VP=2%) was charged and chlorine gas was blown in at a rate of 98 g/Hr over 8 hours while stirring. The total amount of blown chlorine was 11 mol, and during the reaction, cooling was provided from the outside to maintain the internal temperature at 20°C. After the reaction was completed, unreacted chlorine was purged with nitrogen for 2 hours. The catalyst was removed to obtain 1230 g of reaction solution. Compositional analysis of the reaction solution revealed that it was 97.3% 2,3 dichloropropionitrile and 2.8% acrylonitrile. In addition, the reaction solution was distilled under reduced pressure at 63℃/12mmHg to obtain 1156g of 100% pure 2,3-dichloropropionitrile (yield 93.2% vs. acrylonitrile).
was gotten.

Comparative Example 1 Acrylonitrile was added to the chlorination reactor of Example 1.
531 g, pyridine 100 g, and calcium carbonate 50 g were charged, and chlorine was blown in at a rate of 98 g/Hr while stirring. The reaction was carried out by blowing chlorine over 8 hours. The total amount of blown chlorine was 11 moles, and the liquid temperature in the reactor was maintained at around 30°C by cooling from the outside. After the chlorine injection was completed, nitrogen was blown into the reactor to perform dechlorination for 2 hours, and then the calcium carbonate was removed.
A reaction mass of 1170 g was obtained. Analysis of the reaction mass revealed 96.0% 2,3-dichloropropionitrile, 0.6% unreacted acrylonitrile, and by-product α-
It contained 0.6% chloracrylonitrile.

The result of vacuum distillation of the obtained reaction mass was 40 to 60
First distillation 200g at ℃/20~10mmHg, 60~63℃/11mmHg
906g of main residue was obtained. As a result of analyzing the first distillate and main distillate, the first distillate was 2,3-dichloropropionitrile 40wt,
% (6.4 mol% to acrylonitrile) α-chloroacrylonitrile 60wt, % (15.0 mol% to acrylonitrile) Main distillate 2,3-dichloropropionitrile
98.0wt,% (71.6mol% vs. acrylonitrile)
It was hot.

In addition, α-chloroacrylonitrile is 2,3-
This substance is produced by dehydrochlorination of dichloropropionitrile, and the reason for its formation is thought to be that pyridine in the reaction mass acts as a catalyst for dehydrochlorination of 2,3-dichloropropionitrile during distillation. .

Claims (1)

[Claims] 1 2,3 by chlorination reaction of acrylonitrile
- A method for producing dichloropropionitrile, characterized by chlorinating acrylonitrile in the presence of solid polyvinylpyridines2,
Method for producing 3-dichloropropionitrile.