JPH0625196B2 - Method for producing epichlorohydrin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to 2,3-dichloro-1-propanol and / or
The present invention relates to a method for producing epichlorohydrin by dehydrochlorinating 1,3-dichloro-2-propanol using an alkali.

[Conventional technology]

Epichlorohydrin is a raw material for epoxy resin and synthetic rubber,
It is used in large quantities as a stabilizer for chlorinated rubber, glycidyl ethers, glycidyl esters, glycerin and its derivatives, amine adducts and other intermediates or starting materials.

Epichlorohydrin is a mixture of 2,3-dichloro-1-propanol and 1,3-dichloro-2-propanol conventionally obtained by the reaction of allyl chloride with chlorine water. 3
A low-concentration aqueous solution of about 5% by weight is mixed with an alkali suspension such as calcium hydroxide, and the mixture is supplied to a plate-type reaction distillation column, and stripped with steam while dehydrochlorinating. It is industrially manufactured by a method of extracting epichlorohydrin produced from. Since the dichloropropanol obtained by this method is obtained as an aqueous solution having a low concentration as described above, it is kept within the range of sufficient solubility in the liquid phase in the column, and no decrease in reaction rate is observed. On the other hand, a large amount of steam is required for stripping the product.

A method has been proposed in which a high concentration of dichloropropanol such as 10 to 50% by weight is used with respect to the total weight of the liquid fed to the reactive distillation column in order to improve the basic unit of water vapor (JP-A-60- 258172). However, it has been found that the use of such a high concentration of dichloropropanol reduces the apparent reaction rate as compared with the case of using the dilute solution as described above. That is, the dichloropropanol concentration in the feed liquid excluding the alkali content is 50 to 80.
High concentrations such as wt% have recently become available, but the solubility of dichloropropanol in water is 6
It is 20% or less at 0 ° C. and 30% or less at 80 ° C., which is further lowered by the salting out effect due to the salt formed during the reaction. The distribution ratio of dichloropropanol to the product epichlorohydrin and water is about 10: 1. Therefore, it is presumed that the concentration of dichloropropanol in the alkaline water becomes low and the apparent dehydrochlorination rate decreases.

As the reaction rate decreases, the amount of dichloropropanol in the overhead distillate increases. If the residence time in the column is increased, the conversion rate of dichloropropanol increases, but the selectivity of epichlorohydrin decreases due to consumption by the successive reaction. It is possible to separate the distilled dichloropropanol by distillation and recycle it, but if there is a large amount to recycle, the amount of processing in the distillation column will increase, both the equipment cost and energy cost will increase, and the loss amount will increase. It is not preferable because it causes harmful effects.

As a method for solving these problems, a method has been proposed in which a part of the alkali content is supplied above the supply position of dichloropropanol (JP-A-63-17874).
In this method, since the chances of the generated epichlorohydrin coming into contact with the alkali content again during the process of stripping by steam increase, stripping while preventing the ring-opening reaction of epichlorohydrin is effective from the standpoint of both design and stable operating conditions of the column. With great difficulty.

The present applicant has previously used, when supplying epichlorohydrin by supplying dichloropropanol and an alkaline aqueous solution or an alkaline suspension to a tray-type reactive distillation column, using a partial condenser, dichloropropanol of the overhead distillate was used. A method was proposed in which epichlorohydrin can be obtained in high yield with high conversion of dichloropropanol even when the concentration of dichloropropanol in the feed is high, by condensing the portion rich in methane and refluxing it in the distillation column ( Japanese Patent Application 1-28
1419). However, as described above, the apparent decrease in the reaction rate due to the high concentration of dichloropropanol is unavoidable, and it is not always easy to compensate for this by the operation control of only the dephlegmator.

[Problems to be Solved by the Invention]

An object of the present invention is to provide a method for increasing both the conversion rate of dichloropropanol and the selectivity of epichlorohydrin when a high concentration of dichloropropanol is supplied to a reactive distillation column together with an aqueous alkali solution or an alkaline suspension.

[Means and Actions for Solving the Problems]

The present inventors, when supplying dichloropropanol consisting of 2,3-dichloro-1-propanol and / or 1,3-dichloro-2-propanol to a reactive distillation column, an amount that does not reach the molar equivalent of the dichloropropanol. Of dichloropropanol in the mixture by pre-treating it at low temperature and at low temperature compensates for the apparent decrease in reaction rate that occurs when a high-concentration dichloropropanol solution is used, and the dichloropropanol content is high. The present invention has been completed by finding a method for obtaining epichlorohydrin in a high yield with a conversion rate.

That is, the present invention uses an aqueous alkaline solution or suspension containing 1 molar equivalent of 2,3-dichloro-1-propanol and / or 1,3-dichloro-2-propanol and 1 to 1.2 molar equivalents of an alkali content. When producing epichlorohydrin by a dehydrochlorination reaction, 0.05 to 0.4 molar equivalent of alkali content was previously added to the dichloropropanol.
After mixing at 40 ° C to partially dehydrochlorinate, 1.15 to 0.7
A method for producing epichlorohydrin, which comprises continuously supplying a molar equivalent of an alkali content to a reactive distillation column, dehydrochlorinating the rest, and stripping the produced epichlorohydrin with steam to extract it from the top of the column.

The dichloropropanol used in the present invention may be 2,3-dichloro-1-propanol as described above, or 1,3-dichloropropanol.
It may be dichloro-2-propanol or a mixture thereof.

The alkaline compound used in the dehydrochlorination reaction is an alkali metal or alkaline earth metal hydroxide, oxide, or salt with a weak acid, such as sodium hydroxide, calcium hydroxide, potassium hydroxide, sodium carbonate, or carbonate. Use potassium, calcium oxide, barium oxide, etc. as an aqueous solution or suspension. The amount used is 1.0 to 1.2 times the theoretical amount required for the dehydrochlorination reaction of dichloropropanol. The concentration of the alkaline aqueous solution or suspension used here is 3 to 1 because of the ease of handling and the solubility of dichloropropanol.
5% by weight is suitable.

Before supplying the dichloropropanol to the reactive distillation column, 0.05 mol of the predetermined amount of alkali content is added to 1 mol equivalent of the dichloropropanol.
A preliminary reaction is carried out by treating with an aqueous alkali solution or an alkaline suspension containing an alkali content of about 0.3 molar equivalent at 10 to 40 ° C to partially dehydrochlorinate.

As the dichloropropanol, the crude product derived from the previous step can be directly dehydrochlorinated by the method of the present invention without purification. Crude products often contain hydrogen chloride and thus require an alkali for neutralization. In this case, the total amount of the above-mentioned alkali content and the alkali content required for neutralization may be supplied in the preliminary reaction. Even when dichloropropanol containing hydrogen chloride is used as described above, the hydrogen chloride concentration can be substantially zero at the raw material feed port of the reactive distillation column by carrying out the preliminary reaction according to the present invention. It is effective in preventing the non-steady state of the neutralization reaction and dehydrochlorination reaction at 1, and preventing the corrosion of the tower due to the presence of acid.

The pre-reacted dichloropropanol is supplied to the reactive distillation column at a predetermined flow rate. The remaining alkali content used in the preliminary reaction may be mixed with the above-mentioned dichloropropanol immediately before the feed port to the column and fed from one feed port, but the conversion rate of dichloropropanol in the preliminary reaction should be strictly controlled. In order to control the composition of the mixture to be constant and to rapidly stabilize the reaction in the reactive distillation column to maintain a steady state, it is desirable to feed from another feed port provided in the same stage of the column. . Alternatively, the alkali component may be mixed with the condensate of the partial condenser and supplied. When the epichlorohydrin generated in the preliminary reaction is supplied to the column, it easily moves to the gas phase, and the concentration of dichloropropanol in the liquid phase becomes lower than that in the case where the preliminary reaction was not performed. The apparent decrease in reaction rate caused by this is suppressed.
Furthermore, by preliminarily increasing the conversion rate of dichloropropanol by the preliminary reaction, the residence time in the column can be shortened and the number of columns in the column can be reduced.
In combination with the fact that the alkali concentration in the tower can be lowered accordingly, the production of by-products can be reduced and the selectivity of epichlorohydrin can be increased. In addition, since the height of the tower can be reduced during industrial production, it is effective in reducing the plant cost including the frame and other incidental equipment. In order to obtain such an effect, the molar equivalent ratio of dichloropropanol and alkali and the temperature are important in the preliminary reaction. When the alkali content is less than 0.05 molar equivalent with respect to 1 molar equivalent of dichloropropanol, almost no improvement effect is obtained, and it is equivalent to the case where the reaction is performed by immediately supplying to the column without performing a preliminary reaction. Further, when the alkali content exceeds 0.3 molar equivalent, the conversion rate of dichloropropanol increases and the amount of by-products generated increases, whereby the selectivity of epichlorohydrin decreases and the loss of epichlorohydrin cannot be ignored, and the effect of the preliminary reaction is reduced. It is meaningless because it cannot be obtained. When the temperature of the preliminary reaction exceeds 40 ° C., consumption of the produced epichlorohydrin due to hydrolysis and consumption due to the addition reaction with the produced salt are promoted, and the selectivity of epichlorohydrin after the completion of the whole reaction is lowered. If the temperature of the preliminary reaction is less than 10 ° C, the reaction rate will decrease, and the solubility of dichloropropanol in alkaline water will decrease, making it difficult to complete the preliminary reaction within a practical time. In some cases, the feed composition to the column is unstable. This is not preferable because it causes adverse effects such as

Examples of the apparatus for the preliminary reaction used in the method of the present invention include a stirred tank reactor and a tubular reactor. In the latter case, a part of the reactor may be made annular so that the reaction mixture can be circulated, and the liquid can be circulated by a pump to enhance the mixing effect. A static mixer can be inserted in the circuit to further enhance the mixing effect. The preliminary reaction may be carried out continuously or batchwise.

The reactive distillation column used in the method of the present invention includes a packed column,
Examples include a perforated plate tower and a perforated plate tower with downcomers.
Perforated plate towers with downcomers are most suitable. For example, a reflux liquid feed port is provided at the top of the column, and 4 to 6 from the top.
A feed port for the raw material dichloropropanol and the alkali content is provided in the lower stage, and a steam injection nozzle is provided under the lowest stage.

When it is desired to obtain both the conversion of dichloropropanol and the selectivity for epichlorohydrin of 90% or more, the theoretical plate number is usually 13 to 17 when the preliminary reaction of the present invention is not carried out. 10 to 11 steps are sufficient.

〔Example〕

The method for producing epichlorohydrin of the present invention will be described more specifically with reference to the following examples. The composition% in the examples are in weight units, Is.

The reactive distillation column was constructed so that it could be easily disassembled and assembled for experiments. The tower body consists of two 15 mm deep perforated plates with downcomers (opening rate 13%) as one set, and an iron cylinder with an inner diameter of 100 mm with flanges on both ends as one unit. Increase or decrease the number of units according to the required number of stages. It is made possible, and the step interval after assembly is 150 mm. A feed port for the raw material and the alkali component was provided on the fifth stage from the top and a steam injection nozzle was provided on the lower side of the bottom stage. Overhead withdrawal is connected to the sleeve-type total condenser heat transfer surface area 0.3 m ² through a cannula type dephlegmator heat transfer area 0.3 m ^2. The condensate of the dephlegmator is connected to the same stage as the raw material feed port, and the condensate of all the decompressor is piped to enter the liquid separation tank. The upper layer (aqueous layer) of the liquid separation tank is piped so as to reflux to the uppermost stage of the tower, and the lower layer (oil layer) enters the distillate receiving tank. The liquid is extracted from the bottom of the tower by a liquid level controller while keeping the liquid level constant, and is piped so as to enter the can discharge liquid receiving tank. The outlet of all the compactors and the upper part of the separation tank were connected to a vacuum pump so that the operating pressure of the column could be changed.

Example 1 Pre-reaction: Suspension containing 5.9 kg water and 5% calcium hydroxide 18.
After preheating 3 kg of each to about 40 ° C in advance, charge it into a stirring tank made of iron with a jacket and having a capacity of 50, preliminarily react the mixture at 40 ° C for 25 minutes, and immediately cool it to a temperature not exceeding 10 ° C. I kept it. The preliminary reaction rate was 23%.

Reactive distillation: The liquid after the preliminary reaction is withdrawn from the bottom outlet of the stirring tank at 2.54 kg / hr while stirring, and is supplied to the reactive distillation column together with 4.86 kg / hr of the alkaline suspension having the same concentration as above. did. This reactive distillation column has 24 stages, 1.7 kg / hr of steam is blown from a steam blowing nozzle, and the top pressure of the tower is 500 m.
mHg, tower top temperature 86 ℃, tower bottom temperature 99 ℃, dephlegmator temperature 8
The tower was stabilized by operating at 2 ° C. for 8 hours. The reduction rate was 40% based on the overhead distillate. After stabilization of the column, the oil layer that had been condensed from the condensate of the total condensor was sampled and analyzed by gas chromatography, with a conversion of 2,3-dichloro-1-propanol of 98.0% and epichlorohydrin selectivity. 98.5%, 2,3-dichloro-1-in the oil layer
The content of propanol was 3.9%.

Example 2 Preliminary reaction: 2,3-dichloro-1-propanol 58.5%, 1,3-dichloro-2-propanol 4.4%, water 26.9%, hydrogen chloride 10.2
% Of the mixture and 31.0 kg of a suspension containing 10% of calcium hydroxide were preliminarily reacted for 60 minutes in the same manner as in Example 1. The preliminary reaction rate was 40%.

Reactive distillation: 4.86 kg / h of liquid which was preliminarily reacted in the same manner as in Example 1.
2.54 kg / hr of alkaline suspension having the same concentration as that of r was supplied to the same reactive distillation column as used in Example 1, and 1.7 kg / hr of steam was blown from a steam blowing nozzle while the top pressure of the tower was increased. The column was stabilized by operating at 500 mmHg, a column top temperature of 85 ° C., a column bottom temperature of 99 ° C., and a dephlegmator temperature of 80 ° C. for 8 hours. The reduction rate was 50% with respect to the overhead distillate. After stabilizing the tower,
When the product was analyzed in the same manner as in Example 1, 2,3-
Dichloro-1-propanol and 1,3-dichloro-2-
The conversion rate of propanol was 99.2% in total, the selectivity of epichlorohydrin was 98.3%, and 2,3-dichloro-
The contents of 1-propanol and 1,3-dichloro-2-propanol were 1.1% and 0.1%, respectively.

Comparative Example In Example 1, the preliminary reaction was not carried out, and 2,3-dichloro-1-propanol, water and a suspension of calcium hydroxide were directly supplied to the above reactive distillation column to carry out the same procedure as in Example 1. A hydrogen chloride reaction was performed. The conversion of 2,3-dichloro-1-propanol was 96.1%, the selectivity of epichlorohydrin was 97.5%, and the content of 2,3-dichloro-1-propanol in the oil layer was 4.3%.

From the above examples and comparative examples, it is clear that the conversion of dichloropropanol and the selectivity of epichlorohydrin in particular are improved by carrying out the preliminary reaction.

〔The invention's effect〕

By preliminarily reacting dichloropropanol with an excessively small amount of alkali component at a low temperature by the method of the present invention and then supplying it to the reactive distillation column, unnecessary side reactions can be minimized. As a result, the alkali content to be supplied to the tower can be reduced, the alkali concentration in the tower can be lowered as a whole, and the hydrolysis of epichlorohydrin can be reduced. All of these are effective in increasing the conversion of dichloropropanol and improving the selectivity of epichlorohydrin. The method of the present invention is effective as a method for compensating for the decrease in apparent reaction rate of 2,3-dichloro-1-propanol, especially when a high concentration of dichloropropanol is used. When a mixture of 2,3-dichloro-1-propanol and 1,3-dichloro-2-propanol is used, the latter reaction rate is higher, so that the latter is consumed first by performing a preliminary reaction, Since the content of the former becomes relatively large when it is supplied to the column, it is possible to select an operating condition optimal or close to that of the former in the column, which facilitates reaction control. Further, the number of stages of the column can be reduced by the amount of the progress of the reaction, and the amount of by-products can be reduced compared to the case where the whole amount is reacted in the column, so that the organic substance content in the bottom liquid can be reduced industrially. It is useful.

Front page continuation (72) Inventor Wataru Tanaka 5-4-24 Shinoharahonmachi, Nada-ku, Kobe-shi, Hyogo

Claims (1)

[Claims] 1. 1,2-Dichloro-1-propanol and / or
Alternatively, when epichlorohydrin is produced by a dehydrochlorination reaction using an alkaline aqueous solution or an alkaline suspension containing 1 molar equivalent of 1,3-dichloro-2-propanol and 1 to 1.2 molar equivalents of alkali, 1 to 0.05-0.4 molar equivalent of alkali content to dichloropropanol
After mixing at 0 to 40 ° C to partially dehydrochlorinate, 1.15 to
A method for producing epichlorohydrin, which comprises continuously supplying 0.7 molar equivalent of an alkali content to a reactive distillation column to dehydrochlorinate the rest, and stripping the produced epichlorohydrin with steam to extract from the top of the column.