JPH0669990B2 - Method for producing chloropicrin - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing chloropicrin. More specifically, it relates to an industrially advantageous method for producing chloropicrin, which comprises reacting picrate with hypochlorite in an aqueous solution at a pressure lower than atmospheric pressure, and further reacting while blowing steam. Is.

Chlorpicrin is useful as a fumigant, sterilizer and insecticide.

[Conventional technology]

Chlorpicrin is usually produced by chlorinating an aqueous solution of calcium picrate with an aqueous solution of calcium hypochlorite, but on the other hand, it is carried out under atmospheric pressure, and the separation of chloropicrin by steam distillation of the reaction solution is carried out at 100 ° C at atmospheric pressure. It is performed after the reaction is completed below.

[Problems to be solved by the invention]

In the conventional method, calcium chlorite and calcium hypochlorite are reacted under atmospheric pressure to produce chloropicrin, a side reaction occurs as the temperature rises, and decomposition of the raw material hypochlorite also occurs, The lower the reaction temperature, the higher the yield of chloropicrin because the yield of chloropicrin is low.

However, in this reaction, one of the reaction products, such as calcium carbonate, adheres to the side wall of the reaction vessel, making it difficult to cool from the outside and maintaining the reaction temperature at a low temperature, resulting in a high reaction temperature. Also, the reaction yield was not good.

Furthermore, in order to distill and separate chloropicrin from the suspension after the reaction by steam distillation under the atmospheric pressure, the suspension under the atmospheric pressure,
Although it was necessary to raise the temperature to the boiling point, a large amount of steam was required for that purpose.

Therefore, industrially, the reaction temperature is as isothermal as possible,
Moreover, there has been a strong demand for a production method in which the amount of steam used for distilling and separating the produced chloropicrin is small.

An object of the present invention is to provide an industrial manufacturing method which satisfies such conditions.

[Means for solving problems]

The present inventors have earnestly studied to solve the above problems. As a result, the picric acid salt and hypochlorous acid are reacted in an aqueous solution at a pressure lower than atmospheric pressure, and the reaction is performed while distilling chloropicrin by injecting steam during the reaction. The heat of reaction is removed and cooling is not performed from the outside of the reaction tank, the reaction temperature is lowered, the amount of water vapor used for distilling chloropicrin is reduced, and the distilling of chloropicrin is performed from the start of the reaction.
The present invention has been completed by finding a method capable of improving productivity.

That is, the present invention is characterized in that picrate and hypochlorite are reacted in an aqueous solution at a pressure lower than atmospheric pressure, and during the reaction, chloropicrin is distilled while blowing water vapor into the reaction solution. And a method for producing chloropicrin.

Hereinafter, the present invention will be described in detail.

The salts of picrate used in the present invention are preferably calcium, sodium and potassium. These are usually subjected to the reaction as an aqueous solution.

The concentration of the aqueous solution is 85% by weight or less for safety reasons.

Further, as salts of hypochlorite, calcium, sodium and potassium are preferable. Further, these are also usually subjected to the reaction as an aqueous solution, and the concentration of the aqueous solution may be any concentration, but it is preferably 5 to 10% by weight.

This reaction is an exothermic reaction, and in order to prevent the reaction temperature from rising due to the latent heat of vaporization of the distillate, it is preferable to gradually react the aqueous solution of picrate and the aqueous solution of hypochlorite while dropping them.

In addition, stoichiometrically, this reaction requires 11 mol of hypochlorite for 1 mol of picrate, but is not limited.

The reaction is carried out in an excess aqueous solution of hypochlorite from the viewpoint of improving the yield, and the concentration and amount of the excess aqueous solution of hypochlorite used may be arbitrary.

The reaction is carried out under reduced pressure below atmospheric pressure, preferably at a pressure of 150 mmHg or less. Under this pressure, the reaction liquid boils, water and chloropicrin in the reaction liquid evaporate, and the latent heat of evaporation prevents the temperature of the reaction liquid from rising.

Under this reduced pressure, the reaction temperature is defined by the vapor pressure in the composition of the reaction solution, and therefore the temperature is less than 70 ° C. in the present invention.

The steam blown into the reaction tank may be either saturated steam or heated steam.

It is carried out from the start of the reaction of injecting steam, and the distillation time of the produced chloropicrin is shorter than in the conventional case, and the productivity is improved.

The amount of steam to be blown may be an amount that compensates for the amount of latent heat of steam that accompanies the chloropicrin vapor that is produced and distilled off, and the amount of heat that is insufficient for the amount of latent heat for vaporizing the produced chloropicrin.

If the amount is larger than this, steam is wastefully lost, which is not economical.

On the other hand, if the amount is less than this, chloropicrin remains in the reaction suspension and the yield decreases.

The reaction time is preferably 30 minutes or more, and if the reaction time is short, unreacted picrate remains in the reaction solution and the yield decreases.

The reaction may be carried out batchwise or continuously using a tank reactor having a stirrer.

In the case of the continuous type, the reactor may have only one tank or two or more tanks, and the staying time is preferably 30 minutes or more.

[Action and effect]

The conventional chloropicrin production reaction is a reaction under normal pressure, and it is necessary to lower the reaction temperature in order to improve the yield and cooling is performed from the outside, but it is low temperature due to adhesion of by-products to the reactor wall. Was difficult to hold.

Further, in order to distill and separate the produced chloropicrin from the reaction solution by steam distillation, a distiller was provided separately from the reactor, and a large amount of steam was required to raise the boiling point to atmospheric pressure.

Therefore, the reaction time was long and the volumetric efficiency was poor.

In the method according to the present invention, the reaction temperature can be maintained at a low temperature without evaporating water and chloropicrin from the reaction solution by reducing the pressure to a pressure lower than the atmospheric pressure and without external cooling.

Further, it is possible to distill the chloropicrin produced by blowing steam directly into the reaction solution, there is no need to separately distill after transfer liquid to install a distiller, a small amount of water vapor for distilling the produced chloropicrin, And productivity is also good.

Thus, the method according to the present invention is an industrially extremely valuable invention because chloropicrin can be obtained in a high yield in a short time.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to Examples.

In addition,% shows weight%.

The first vessel of Example 1 0.03 m ^3, the second tank 0.03 m ^3, were placed stepwise as shown in Figure 1 a third tank of 0.06 m ^3. 0.02 m ³ of 8% calcium hypochlorite aqueous solution was previously laid in the first tank (1) of FIG.

While injecting ² kg / cm ² G of steam (10) at 2.0 kg / h into the first tank (1), 28% calcium picrate aqueous solution (9)
And 8% calcium hypochlorite aqueous solution (8) each 1
3.8 kg / H and 188.8 Kg / H were charged and stirred. 3 reaction tanks
It was kept at 65 mmHg abs.

The reaction temperature in the first tank (1) was 41 ° C., and the reaction liquid overflowed and flowed into the second tank (2). When the amount of the reaction liquid flowing into the second tank (2) reached a predetermined amount, 2 kg / cm ² G of steam (11) was blown at 2.2 kg / H while stirring and the temperature was adjusted to 41
Chloropicrin and water were distilled off at ℃.

When the amount of the reaction liquid flowing from the second tank (2) to the third tank (3) due to overflow reached a predetermined amount, 2 kg / cm ² G of steam (12) was blown at a rate of 2.2 kg / H and the temperature was changed while stirring. Four
Chloropicrin and water were distilled off at 1 ° C.

This operation was performed for 8 hours, the distillate gas from the first to third tanks was condensed in the condenser (5), and the condensate was stored in the receiver (7).

Chloropicrin in the condensate was 60 kg.

Picrate conversion rate is 99.9%, chloropicrin yield is 93.8
%Met.

Example 2 With the same apparatus as in Example 1, the pressure in the reaction vessel was set to 100 mmHg ab
s, 55.2 Kg of chloropicrin was obtained in the condensate by completely the same operation except that the temperature of the reaction liquid was 47 ° C.

Picrate conversion 99.7%, chloropicrin yield 98.3%
Met.

Comparative Example-1 0.15 m ³ of 8% calcium hypochlorite aqueous solution was previously laid in a 0.3 m ³ reaction tank having a cooling coil having a heat transfer area of 0.5 m ² inside.

A 28% calcium picrate aqueous solution and an 8% calcium hypochlorite aqueous solution were respectively charged into the 36.8 Kg / H and 503.5 Kg / H reaction tanks and stirred.

While cooling water is passed through the cooling coil in the reaction tank, 55
The reaction was carried out for 3 hours while maintaining the temperature at ℃.

Then, the liquid was transferred to a 0.3 m ³ distillation tank, and the temperature of the reaction liquid was raised to 100 ° C.

Blow 2Kg / cm ² G water vapor into the reaction solution at 37Kg / H for 3 hours,
Chloropicrin and water were distilled off and condensed in a condenser.

Chloropicrin in the condensate was 50.5 Kg.

The conversion of picrate was 99.7% and the yield was 79.0%.

EFFECTS OF THE INVENTION As can be seen from the results of Examples and Comparative Examples, it can be understood that the yield of chloropicrin is good and the amount of steam used can be small if the reaction is performed under reduced pressure at a low temperature and steam distillation is performed.

[Brief description of drawings]

FIG. 1 shows the steps in Examples 1 and 2, and the symbols in the figure have the following meanings. 1: First tank, 2: Second tank, 3: Third tank 4: Stirrer, 5: Condenser, 6: Decompression device 7: Receiver 8: Calcium hypochlorite aqueous solution 9: Calcium picrate aqueous solution 10, 11 , 12: Water vapor 13: Condensed water, chloropicrin 14: Reaction waste liquid

Claims (5)

[Claims] 1. A process for producing chloropicrin, which comprises reacting picrate with hypochlorite in an aqueous solution under a pressure lower than atmospheric pressure. 2. A picrate and a hypochlorite in an aqueous solution,
A method for producing chloropicrin, which comprises reacting under a pressure lower than atmospheric pressure to distill chloropicrin while blowing water vapor into the reaction solution. 3. The method according to claim 1 or 2, wherein the absolute pressure below atmospheric pressure is 150 mmHg or less. 4. The method according to claim 1 or 2, wherein the picrate is calcium picrate, sodium picrate, or potassium picrate. 5. The method according to claim 1 or 2, wherein the hypochlorite is calcium hypochlorite, sodium hypochlorite, or potassium hypochlorite.