JPS6160055B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention involves the chlorination of allyl alcohol with chlorine in an aqueous hydrochloric acid solution to produce 2,3-dichloro-1-
In the method for producing propanol, especially 2,
The present invention relates to a method for obtaining 3-dichloro-1-propanol.

2,3 obtained by chlorinating allyl alcohol
-dichloro-1-propanol (hereinafter referred to as 2,
Abbreviated as 3DCP. ) is a compound useful as an intermediate in the production of epichlorohydrin, which is widely used as a solvent, epoxy resin raw material, synthetic rubber raw material, chlorinated rubber stabilizer, etc.

As a method for producing 2,3DCP by chlorinating allyl alcohol with simple chlorine, for example, there is a method using a saturated solution of hydrogen chloride of a low boiling point ether as a solvent (Japanese Patent Application Laid-open No. 1361/1983). According to this method, dichloropropanol is said to be obtained with a high yield of 94 to 98%, but the product is 1,3-dichloro-1-propanol (hereinafter abbreviated as 1,3DCP) 10 % and 90% of 2,3DCP, and distillation is essential to obtain 2,3DCP after the reaction.In addition to the loss of solvent during the reaction, there is also a loss of solvent and product during distillation. There is a drawback that it does.

Another method is to use a lower aliphatic alcohol saturated with hydrogen chloride as a solvent (Tokuko Sho
No. 48-18207). In this case, 1,3DCP is hardly produced and 2,3DCP is obtained in high yield (96.9% at -40℃, 93.8% at 0℃), but after the reaction The separation of 2,3DCP is carried out by distillation, and therefore there are the same problems of solvent and product loss as in the previous methods.

In order to avoid the above-mentioned disadvantages associated with the use of organic solvents, it is possible to conduct the reaction without a solvent or using an aqueous solvent, but for the former,
The yield is only about 20% (Tornoe, Ber.,
24 , 2670 (1891)). As an example of using an aqueous solvent, a method of chlorination in an aqueous hydrochloric acid solution has been proposed (Japanese Patent Publication No. 37-17206). According to this method, 1,3DCP is said to be substantially not produced as a by-product, but the yield of 2,3DCP is 50 to 70%. In addition, after the reaction, extraction with an organic solvent is performed to obtain 2,3DCP, and therefore there is a loss of dissolution of the solvent and product into the aqueous layer, resulting in the use of an organic solvent during the reaction. This method has the same drawbacks as the method described above, and there is also the problem that hydrochloric acid and alkali are consumed because hydrochloric acid is neutralized with alkali in order to increase the yield of 2,3DCP by extraction.

As a result of intensive study on chlorination in a system using this aqueous hydrochloric acid solution, the inventors found that the concentration of hydrogen chloride was
When the reaction is carried out in a 50-75% by weight aqueous solution, 2,
It was found that only 3DCP could be obtained with a high yield of over 90%. The present invention provides, in this chlorination method,
In particular, it relates to a method for obtaining generated 2 and 3DCPs.

As is well known, at normal temperature and pressure, the hydrogen chloride concentration in an aqueous hydrochloric acid solution is approximately 36% at maximum, and in the present invention, chlorination is carried out as necessary to maintain the hydrogen chloride concentration at 50 to 75% by weight. Although the reaction is carried out at low temperatures and/or under pressure, the 2,3DCP produced in the reaction is uniformly dissolved in the aqueous solution in the presence of highly concentrated hydrochloric acid and generally does not separate even after cooling. However, since 2,3DCP is originally poorly soluble in water, as the concentration of hydrochloric acid decreases, its original physical property of being poorly soluble in water gradually becomes apparent, and it separates into an upper aqueous phase and a lower 2,3DCP phase. It's coming.

In the present invention, this phase separation occurs in a 20% by weight aqueous hydrochloric acid solution in which the composition is an azeotropic composition of water and hydrogen chloride.
This is based on the discovery that it is sufficient to separate and recover 2,3DCP.

That is, the present invention recovers hydrogen chloride gas by heating a homogeneous solution of 2,3DCP obtained by chlorinating allyl alcohol under normal pressure or increased pressure in an aqueous solution with a hydrogen chloride concentration of 50 to 75% by weight. After this recovery is preferably carried out to near the azeotropic composition of hydrogen chloride and water, the lower 2,3DCP phase is obtained by cooling to 30°C or lower, preferably 25°C or lower to separate from the aqueous phase, The feature is that the upper aqueous phase (220% hydrochloric acid aqueous solution phase) is recycled and used as a new chlorination solvent.

According to the present invention, the heating during recovery of hydrogen chloride may be mild, and almost no decomposition of 2,3DCP is observed during this heating, and the separated and recovered oil layer contains about 80% by weight of 2,3DCP, and the chloride The hydrogen content is about 4% (20% by weight as a 20% aqueous hydrochloric acid solution).

For example, when the obtained 2,3DCP is used as a raw material for the synthesis of epichlorohydrin, it can be used as it is without any special purification, or after dilution with water and, if necessary, neutralization with lime etc. , it can be subjected to a saponification reaction with lime water. In this case, the hydrogen chloride contained in the oil layer is 4%
Therefore, only a small amount of lime is lost due to the neutralization of hydrogen chloride.

On the other hand, the upper layer of hydrochloric acid (approximately 20% by weight aqueous solution)
Contains approximately 20% by weight of 2,3DCP, which is recycled to the allyl alcohol chlorination process as a solvent, but at this time, the previously recovered hydrogen chloride gas is used to react with the hydrogen chloride gas necessary for the reaction. Hydrochloric acid concentration can also be maintained.

As described above, the present invention provides a method for producing 2,3DCP that improves the yield by more than 20% compared to the conventional chlorination reaction in an aqueous hydrochloric acid solution. By recovering the minimum amount of hydrogen chloride necessary, 2,3DCP can be separated in a state that can be used as is in the next process.On the other hand, the hydrochloric acid aqueous solution is chlorinated again after blowing hydrogen chloride to the required concentration of hydrochloric acid. This provides a process that can be used as a solvent for chemical reactions. In the method of the present invention, there is no problem of separation from the solvent or solvent loss caused by conventional organic solvent methods, and only a heat source is required to recover the excess hydrogen chloride that reaches the azeotropic composition.
There is no loss due to decomposition of products due to distillation separation.
It is extremely suitable for implementation on an industrial scale.

The method of the present invention will now be explained by way of examples.

Example 56.0 g of hydrogen chloride gas was blown into 50 g of water at 0° C. under normal pressure to dissolve 0.5 mole (29.0 g) of allyl alcohol. The reaction solution was externally cooled to maintain a temperature of 0°C, and 0.5 mole of chlorine was blown in over 40 minutes while stirring.After the reaction was completed, it was analyzed by liquid chromatography, and it was found that 2. 3DCP was produced with a yield of 94.0%.
Next, the reaction solution was returned to normal pressure and hydrogen chloride gas was removed, and the hydrogen chloride gas was recovered until the concentration of hydrochloric acid in the reaction solution reached 20% by weight as an aqueous solution. Then, the residual liquid was cooled to 10°C and left to stand. Separate the lower layer and 61.2
An oil layer of g was obtained. Analysis by liquid chromatography revealed that it contained 79% by weight of 2,3DCP.
Incidentally, when this was directly subjected to a saponification reaction with lime water using a conventional method, the result was 97.5% compared to the theoretical value.
Epichlorohydrin was obtained with a yield of %. On the other hand, the upper layer (65.8 g) contained 19% by weight of 2,3DCP. Hydrogen chloride gas was blown into this aqueous layer at 0°C and normal pressure until it was saturated, then 29.0 g of allyl alcohol was dissolved, and chlorine gas was added while maintaining the conditions at 0°C and normal pressure.
After injecting 0.5 mol and causing a reaction, analysis revealed that 94.0% 2,3DCP was produced based on the newly charged allyl alcohol.

Claims (1)

[Claims] 1 2,3-dichloro-1 obtained by chlorinating allyl alcohol in a 50-75% by weight aqueous hydrochloric acid solution
- Heat a homogeneous solution of propanol to recover hydrogen chloride gas, cool the residual liquid to below 30°C, separate the lower 2,3-dichloro-1-propanol phase, and separate the upper hydrochloric acid aqueous solution phase. 1. A method for producing 2,3-dichloro-1-propanol, which comprises recycling 2,3-dichloro-1-propanol to a chlorination step of allyl alcohol.