JP2010248104A - Process for producing 1,1,1,2,3-pentachloropropane - Google Patents

Abstract

In a method for producing 1,1,1,2,3-pentachloropropane in which 1,1,1,3-tetrachloropropane is dehydrochlorinated and subsequently chlorinated, it is a product of dehydrochlorination. Provided is a method for producing 1,1,1,2,3-pentachloropropane having a low cost and high purity without distilling trichloropropene.
The conversion rate when dehydrochlorinating 1,1,1,3-tetrachloropropane is 99.5% or less, and the conversion rate in chlorination of trichloropropene is 97% or less. A method for producing 1,1,2,3-pentachloropropane. By suppressing the conversion rate during dehydrochlorination, the generation of impurities in this process is reduced, and by suppressing the conversion rate during chlorination, 1,1,1,2,3-pentachloropropane By-product formation of 1,1,1,3,3-pentachloropropane, which is difficult to be separated, is suppressed.
[Selection figure] None

Description

The present invention relates to a process for producing halogenated alkanes. Specifically, 1,1,1,3-tetrachloropropane is dehydrochlorinated to produce trichloropropene, and the resulting trichloropropene is reacted with Cl ₂ to produce 1,1,1,2 , 3-pentachloropropane and a process for producing 1,1,1,2,3-pentachloropropane.

1,1,1,2,3-pentachloropropane is an important chlorine compound as an intermediate of various industrial products including an intermediate of an agricultural chemical raw material. As the manufacturing method, several types of manufacturing processes can be considered. For example, an addition reaction step of producing 1,1,1,3-tetrachloropropane using ethylene and carbon tetrachloride as raw materials, and the resulting 1,1,1,3-tetrachloropropane is dehydrochlorinated to trichloropropene ( A dehydrochlorination step, which is a mixture of 1,1,3-trichloropropene and 3,3,3-trichloropropene; the same applies unless otherwise specified), and the resulting trichloropropene is reacted with Cl ₂ to give 1,1 1,1,2,3-pentachloropropane has been proposed (see, for example, Patent Document 1).

In this method, if the conversion rate of 1,1,1,3-tetrachloropropane is excessively increased during the dehydrochlorination reaction, the generation of by-products becomes significant. Therefore, the conversion rate should be suppressed to about 80 to 90%. Is needed. The obtained trichloropropene is distilled to separate it from unreacted raw materials and by-products, and then reacted with Cl ₂ until the conversion rate becomes 100%.

Japanese Examined Patent Publication No. 2-47969

  However, since the above method uses distillation, it is an industrially extremely expensive method.

Therefore, the present inventors tried to react with Cl ₂ without distilling trichloropropene obtained by dehydrochlorination of 1,1,1,3-tetrachloropropane. However, it has been clarified that by-products (impurities) that are difficult to separate from the obtained 1,1,1,2,3-pentachloropropane are produced when the impurities are not separated by distillation.

  Therefore, the present invention provides a distillation method for trichloropropene, which is an intermediate, in a production method for obtaining 1,1,1,2,3-pentachloropropane via trichloropropene using 1,1,1,3-tetrachloropropane as a starting material. It is an object of the present invention to provide a method for obtaining high-purity 1,1,1,2,3-pentachloropropane without requiring a high-cost intermediate purification means.

  As a result of intensive investigations in view of the above problems, the present inventors have found that 1,1,1,3-pentachloropropane contains impurities that are difficult to separate and are contained in trichloropropene. It was found that tetrachloropropane, i.e., 1,1,1,3,3-pentachloropropane produced by reacting the unreacted starting material in the chlorination step.

  Therefore, the 1,1,1,3-tetrachloropropane contained in the trichloropropene is not removed by distillation or the like so that 1,1,1,3,3-pentachloropropane is not generated. Various methods for obtaining a high conversion rate while suppressing the formation of by-products during the dehydrochlorination of 3-tetrachloropropane were studied. As a result, by setting the reaction temperature of dehydrochlorination to 85 ° C. or higher (particularly preferably 90 ± 2 ° C.), which is even higher than the temperature of 40 to 80 ° C. described in Patent Document 1, high conversion rate and It was found that high selectivity is compatible (filed as Japanese Patent Application No. 2009-75794).

  However, even if the reaction temperature at the time of dehydrochlorination is set to a high temperature as described above, by-product formation becomes significant when the reaction is carried out until the conversion rate reaches 100%, resulting in a decrease in final yield. It has been found that it is industrially impractical to react up to a conversion rate of 100%.

  As a result of further investigations, it was found that by-product generation due to the reaction of 1,1,1,3-tetrachloropropane in the above chlorination step was after almost no trichloropropene was present in the reaction system. As a result of further study, the present invention was completed.

That is, the present invention relates to a dehydrochlorination step in which 1,1,1,3-tetrachloropropane is dehydrochlorinated with alkali to obtain trichloropropene, and the resulting trichloropropene is reacted with Cl ₂ to produce 1,1,1. 1,1,1,2,3-pentachloropropane having a chlorination step, 1,1,1,3-tetrachloropropane in (1) dehydrochlorination step (2) The reaction product trichloropropene was subjected to a chlorination step in a state containing unreacted 1,1,1,3-tetrachloropropane, and (3 ) A process for producing 1,1,1,2,3-pentachloropropane characterized in that the conversion rate of trichloropropene in the chlorination step is 97% or less.

In another invention, trichloropropene containing 1,1,1,3-tetrachloropropane as an impurity (provided that 1,1,3-trichloropropene and / or 3,3,3-trichloropropene) is Cl ₂ . A process for producing 1,1,1,2,3-pentachloropropane having a step of reacting and chlorinating, wherein the conversion rate of the trichloropropene in the chlorination step is 97% or less. This is a method for producing 1,1,1,2,3-pentachloropropane.

  According to the present invention, even if trichloropropene is subjected to a chlorination step without being separated from unreacted 1,1,1,3-tetrachloropropane, the target substance 1,1,1,2,3-penta is obtained. Production of 1,1,1,3,3-pentachloropropane (by-product) that hinders separation and purification of chloropropane can be suppressed.

  Therefore, it becomes easy to obtain high-purity 1,1,1,2,3-pentachloropropane at low cost.

In the present invention, 1,1,1,3-tetrachloropropane (CCl ₃ —CH ₂ —CH ₂ Cl) is used as a starting material. The method for obtaining / manufacturing the 1,1,1,3-tetrachloropropane is not particularly limited, but is generally synthesized by an addition reaction of carbon tetrachloride to ethylene. As typical reaction conditions, a metal complex catalyst comprising a phosphoric acid catalyst such as a phosphoric acid ester or a phosphorous acid ester and an iron catalyst is used, the reaction temperature is about 70 to 130 ° C., and the reaction pressure is 0.1 to Manufactured at 3 MPaG.

In the present invention, first, hydrogen chloride is eliminated from 1,1,1,3-tetrachloropropane with alkali to obtain a mixture of 1,1,3-trichloropropene and 3,3,3-trichloropropene. When the elimination reaction occurs at the 1st and 2nd positions, 1,1,3-trichloropropene is generated, and when it occurs at the 2nd and 3rd positions, 3,3,3-trichloropropene is generated. In any compound, 1,1,1,2,3-pentachloropropane is produced when chlorine (Cl ₂ ) is added in the chlorination step described later.

  The alkali (base) to be used is not particularly limited as long as hydrogen chloride can be eliminated from 1,1,1,3-tetrachloropropane, and a known alkali can be used. Generally, alkali metal, alkaline earth metal, ammonia, amine hydroxide or weak acid salt. More specifically, sodium hydroxide, potassium hydroxide, calcium hydroxide or the like is used. Further, alkali metal alkoxide such as sodium ethoxide may be used. Alkali metal and alkaline earth metal hydroxides are preferred because they are easily available, inexpensive, excellent in handleability, and industrially useful. Two or more alkalis may be used in combination as required. In the following description, a case where an alkali metal or alkaline earth metal hydroxide is used as an alkali will be described as a representative example unless otherwise specified.

  In general, these alkali metal and alkaline earth metal hydroxides are solid, so that they are usually used as an aqueous solution in order to improve the handleability and reactivity. The usage-amount of the said alkali is 0.95-1.5 equivalent with respect to 1,1,1,3-tetrachloropropane, Preferably it is 1.0-1.3 equivalent. The alkali concentration in the case of an aqueous solution is generally 2 to 50 wt% aqueous solution.

  By bringing the alkaline aqueous solution into contact with 1,1,1,3-tetrachloropropane, hydrogen chloride is desorbed from the 1,1,1,3-tetrachloropropane. Since 1,1,1,3-tetrachloropropane is a water-insoluble liquid, it does not have compatibility with an aqueous alkali solution and becomes a two-phase system. Therefore, a phase transfer catalyst is used to obtain a practical reaction rate.

  As the phase transfer catalyst, known compounds can be used without any particular limitation. For example, quaternary ammonium salts and quaternary phosphonium salts can be used. Further, in order to facilitate separation of the trichloropropene phase and the aqueous phase obtained after completion of the dehydrochlorination reaction, a surfactant having an HLB in the range of 6 or more and 11 or less may be used as the phase transfer catalyst. preferable.

  The surfactant HLB is manufactured by Davies from Proc. It is defined by the following calculation formula from the number of hydrophilic groups and lipophilic groups as shown in 2nd International congress of surface activity.

HLB = Σ (the number of hydrophilic groups) + Σ (the number of lipophilic groups) +7
As such a phase transfer catalyst, a quaternary ammonium salt represented by R ¹ R ² R ³ R ⁴ N ⁺ • Y ⁻ or a quaternary represented by R ¹ R ² R ³ R ⁴ P ⁺ • Y ⁻ is used. Cationic surfactants such as phosphonium salts can be preferably used.

In the quaternary ammonium salt or phosphonium salt represented by these formulas, R ¹ , R ² , R ³ and R ⁴ may be the same or different from each other. R is preferably a hydrocarbon group which is not substituted or substituted with a functional group which is inert under the reaction conditions. Particularly preferred is an unsubstituted saturated hydrocarbon group.

  Examples of quaternary ammonium ions include tetramethylammonium ion, tetraethylammonium ion, tetra-n-propylammonium ion, tetra-n-butylammonium ion, cetyltrimethylammonium ion, stearyltrimethylammonium ion, benzyltrimethylammonium ion, Examples include benzyltriethylammonium ion, benzyltributylammonium ion, cetylbenzyldimethylammonium ion, phenyltrimethylammonium ion, and phenyltriethylammonium ion.

Examples of the anion Y ⁻ include chlorine ion, fluorine ion, bromine ion, iodine ion, sulfate ion, hydrogen sulfate ion, nitrate ion, hydroxide ion, acetate ion, and the like. Particularly preferred are chlorine ion, bromine ion, iodine ion and hydroxide ion.

  The amount of the phase transfer catalyst used is not particularly limited and may be used within a known range. Generally, about 0.0001 to 0.05 parts by weight is used with respect to 1 part by weight of 1,1,1,3-tetrachloropropane. Two or more phase transfer catalysts may be used in combination as required.

In the phase transfer catalyst, a compound having a hydroxide ion (OH ⁻ ) as an anion can also act as an alkali. In this case, the amount of alkali used is an amount including the amount added as the phase transfer catalyst.

  A higher reaction temperature for dehydrochlorination in the present invention is preferable because the reaction rate increases and the required time is shortened. However, on the other hand, considering the volatilization, boiling, etc. of the alkaline aqueous solution to be used, it is preferable to set it to 100 ° C. or less. .

  Furthermore, according to the study by the present inventors, the selectivity after the point when the conversion of 1,1,1,3-tetrachloropropane exceeds 70% is relatively good by setting the reaction temperature to 85 ° C. or higher. become. Therefore, the reaction temperature after this point is more preferably 85 ° C. or higher. Considering the accuracy of industrial temperature control, etc., it is preferable to react at 90 ± 5 ° C., and it is particularly preferable to react at 90 ± 2 ° C. Of course, as described above, since it is more advantageous in terms of reaction rate to set the temperature higher than 70% before the conversion rate becomes 70%, the temperature range after the time when the conversion rate becomes 50% may be set. Preferably, it is after the time when the conversion rate becomes 30%.

  By setting the reaction temperature in the dehydrochlorination to 85 ° C. or higher, the selectivity can be kept high even if the conversion is increased. However, when the conversion rate exceeds 99.5%, a large amount of by-products are rapidly generated even when the reaction is carried out at such a temperature, and the selectivity is extremely reduced (note that this is the generated trichloropropene). Is presumed to be the main cause). Therefore, in the present invention, the conversion of 1,1,1,3-tetrachloropropane during the dehydrochlorination needs to be 99.5% or less.

  On the other hand, if the conversion is performed at the above temperature, if the conversion rate is 99.5% or less, the selectivity is not lowered so as to cause a serious problem. The conversion is preferably 90.0% or more, more preferably 95.0% or more, further preferably 98.0% or more, and particularly preferably 99.0% or more. In addition, the conversion rate and the production | generation state of a by-product accompanying progress of reaction can be grasped | ascertained easily by a gas chromatograph etc., for example.

  In general, the conversion can be easily controlled within the above range by controlling the reaction time. Since the reaction time varies depending on the reaction scale and the type and amount of the phase transfer catalyst, it cannot be determined unconditionally, but generally a conversion rate of 95% or more can be obtained in 30 minutes to 24 hours. The reaction may be stopped before it exceeds 99.5% by monitoring the conversion rate accompanying the reaction by the gas chromatograph or the like. The reaction can be easily stopped by stopping the heating and stirring described later.

  In the present invention, the method for contacting 1,1,1,3-tetrachloropropane and alkali for causing the dehydrochlorination reaction is not particularly limited, and a known method may be employed. For example, a method of adding an alkaline aqueous solution in which a phase transfer catalyst is gradually dissolved in 1,1,1,3-tetrachloropropane heated to a predetermined temperature, or 1,1,1,3-tetrachloropropane and an alkali All other components such as an aqueous solution and a phase transfer catalyst can be placed in a reaction vessel and then contacted by any method such as a method of raising the temperature. Since the operation is simple, it is preferable to employ the latter method.

  As is well known, in a reaction using a phase transfer catalyst, the contact area between the organic phase and the aqueous phase is increased by stirring the reaction system. Also in the present invention, it is preferable to vigorously stir during the reaction in order to cause the reaction between 1,1,1,3-tetrachloropropane and alkali quickly and to make the temperature of the entire reaction system uniform. In order to sufficiently stir the reaction system, it is preferable to devise a stirring blade, a baffle and the like. Further, stirring may be performed by shaking or ultrasonic vibration.

  After reaching the target conversion rate (99.5% or less), heating and stirring (or other means for expanding the contact area; the same applies hereinafter) to the reaction system are stopped. The trichloropropene phase and aqueous phase produced by stirring during the reaction are mixed together by forming an emulsion or the like, and therefore the trichloropropene phase is separated and recovered after the two phases are separated. As described above, when a surfactant having an HLB in the range of 6 or more and 11 or less is used as a phase transfer catalyst, separation of both phases becomes rapid.

  The recovered trichloropropene is preferably washed with pure water, ion-exchanged water or the like in order to remove water-soluble components such as alkali metal, alkaline earth metal and phase transfer catalyst used. In addition, even when water is not used in the dehydrochlorination reaction by using an alkali metal alkoxide or the like as an alkali, it is preferable to wash with water in order to remove the alkali metal or the like.

Furthermore, the recovered trichloropropene is in a state containing a relatively large amount of water by performing an operation such as using an alkali as an aqueous solution during the reaction or removing an alkali metal or the like by washing with water. Since this moisture may induce side reactions such as the formation of chlorohydrin during the chlorination reaction with Cl ₂ described below, it is preferable to dehydrate and remove (dry) it. Considering the cost due to the yield reduction due to the side reaction and the cost necessary for performing the drying, a drying level of about 500 ppmw or less is sufficient.

  As a drying method, a known drying method for chlorinated hydrocarbons can be applied, but a method using a desiccant is preferable because it can be dried very inexpensively and easily. As the desiccant to be used, a known desiccant usable for drying chlorinated hydrocarbons can be used. Specific examples include molecular sieve, silica gel, activated alumina, calcium chloride, sodium sulfate, magnesium sulfate, calcium sulfate and the like. It is done. Among these, molecular sieves are particularly preferable in terms of drying ability, ease of handling, cost (recyclability), and the like.

In the present invention, in order to obtain 1,1,1,2,3-pentachloropropane which is the target product, trichloropropene obtained as described above (1,1,3-trichloropropene and 3,3 as described above) Chlorinated with Cl _2, which is a mixture of 3,3-trichloropropene.

  As described above, since the conversion of 1,1,1,3-tetrachloropropane is 99.5% or less in the present invention, the recovered trichloropropene contains unreacted 1,1,1,3- A small amount of tetrachloropropane is mixed. In general, unreacted raw materials are removed by distillation or the like, and the subsequent process is performed. However, distillation requires a large amount of equipment and operation, and is a very expensive method industrially. In addition, there is no industrially realistic method at present that can separate 1,1,1,3-tetrachloropropane and trichloropropene by methods other than distillation.

  For these reasons, in the present invention, the reaction product trichloropropene is subjected to a chlorination step in a state containing unreacted 1,1,1,3-tetrachloropropane. In the present invention, it is not required that trichloropropene is not used for purification means, and it is preferable to perform washing and drying as described above. The embodiment includes a mode in which the 1,1,1,3-tetrachloropropane in the reaction cannot be completely removed and the chlorination step is performed in a state containing the 1,1,1,3-tetrachloropropane.

In the present invention, in the chlorination step, trichloropropane and Cl ₂ are reacted to obtain 1,1,1,2,3-pentachloropropane. As described above, the trichloropropene obtained by the dehydrochlorination step is a mixture of 1,1,3-trichloropropene and 3,3,3-trichloropropene. However, when trichloropropene is added with chlorine, This produces 1,1,2,3-pentachloropropane.

  In the present invention, unlike the prior art, the conversion rate of trichloropropene in this step needs to be 97% or less. When the reaction is allowed to proceed until the conversion rate is higher than this, 1,1,1,3-tetrachloropropane contained as an impurity is also chlorinated to produce 1,1,1,3,3-pentachloropropane. This 1,1,1,3,3-pentachloropropane has close physical properties such as boiling point to 1,1,1,2,3-pentachloropropane for the purpose of production in the present invention, and is extremely difficult to separate and purify. This is because it becomes.

  According to the study by the present inventors, the chlorination reaction of trichloropropene proceeds preferentially over the chlorination reaction of 1,1,1,3-tetrachloropropane, so when the conversion rate is 97% or less. If the chlorination is stopped, the progress of the side reaction to produce 1,1,1,3,3-pentachloropropane is suppressed, and as a result, 1,1,1,2,3-pentachloropropane is produced in a high yield. Purification can be facilitated.

The chlorination step is carried out using known conditions for producing a chlorinated compound by adding Cl ₂ to a carbon-carbon unsaturated bond, except that the conversion rate is 97% or less as described above. Good.

The addition reaction proceeds easily by contacting Cl ₂ with trichloropropene. In general, Cl ₂ is brought into contact by being introduced and fed into trichloropropene in the gaseous state. In order to easily adjust the reaction rate and the like, the Cl ₂ may be diluted with an inert gas such as nitrogen or argon. Trichloropropene may be used in an undiluted state, or may be diluted with a solvent that does not react with Cl ₂ (for example, carbon tetrachloride). Most preferably, gaseous Cl ₂ is introduced into and contacted with undiluted trichloropropene.

  The supply rate of chlorine gas is not particularly limited, but if the reactor has no heat removal equipment, the supply amount of chlorine is reduced when the temperature rises so that the reaction temperature does not exceed 80 ° C. It is a preferred embodiment to make adjustments. When the reaction temperature exceeds 80 ° C., 1,1,1,2,3-pentachloropropane impurities tend to increase.

As described above, the reaction temperature is preferably 80 ° C. or lower. On the other hand, the lower limit temperature is preferably not less than the liquefaction temperature of Cl ₂ and more preferably 0 ° C. or more.

  The reaction pressure is not particularly limited, but it is generally preferable to carry out the reaction at a normal pressure which is inexpensive and easy to operate.

As is well known, when a halogen such as Cl ₂ is added to a carbon-carbon unsaturated bond, it is added by a radical mechanism by irradiating with ultraviolet light or by an ion mechanism in a polar medium. There is a way. Usually, the reaction rate is faster when the addition reaction is carried out by the radical mechanism, whereas there are fewer by-products when the reaction is carried out by the ionic mechanism. Either mechanism may be employed in the present invention. Since trichloropropene as a raw material and 1,1,1,2,3-pentachloropropane as a product have asymmetric chlorine bonding positions, radical generation such as irradiation with ultraviolet light without using a polar solvent. If no means is used, the ion mechanism is the main reaction mechanism.

As Cl _{2 to be} used, chlorine generated by electrolysis from alkali metal chloride may be used containing oxygen or the like without being purified, or liquefied chlorine, and further oxygen is obtained by repeating liquefaction and vaporization. Reduced chlorine may be used.

The method for setting the conversion rate of trichloropropene to 97% or less is not particularly limited, but can be carried out by stopping the supply of Cl ₂ to trichloropropene when the desired conversion rate is reached. In addition, since the reaction rate decreases as the conversion rate of trichloropropene increases, an excess amount of Cl ₂ is supplied, and when the desired conversion rate is reached, Cl ₂ in the reaction system is removed from nitrogen gas or the like. A method of stopping the reaction by expelling with an active gas is also possible. This method is preferable in that the desired conversion can be achieved in a shorter time.

The conversion rate of trichloropropene can be easily grasped by a gas chromatograph or the like. Since addition of Cl ₂ to trichloropropene proceeds almost quantitatively, the conversion rate calculated from the supply amount of Cl ₂ substantially matches the actual conversion rate. Therefore, the conversion rate can be 97% or less without necessarily measuring the conversion rate directly.

  Considering the yield and the like, it is preferable that the conversion rate is high, and the chlorination is allowed to proceed until the conversion rate is preferably 90% or more, more preferably 95% or more.

  The 1,1,1,2,3-pentachloropropane thus obtained can be used as it is as a raw material for other reactions, or may be purified by distillation or the like.

  EXAMPLES Hereinafter, examples and comparative examples will be shown to specifically describe the present invention, but the present invention is not limited only to these examples.

Example 1
In the dehydrochlorination step, 250 g of 1,1,1,3-tetrachloropropane and 0.4 g of tetra-n-butylammonium bromide as a phase transfer catalyst were charged in a 500 ml flask equipped with a stirring blade, a thermometer and a condenser. After maintaining at 90 ° C., 66 g of caustic soda dissolved in 200 ml of pure water was added. Immediately after the addition, the reaction temperature dropped to 80 ° C., but after 5 minutes it became 90 ° C. again, and then the reaction was performed at 90 ° C. for 2 hours. Then, heating and stirring were stopped, and the organic phase and the aqueous phase were separated. The resulting organic phase was separated and washed with pure water, and the resulting crude trichloropropene was analyzed by gas chromatography. As a result, it was converted into 1,1,3-trichloropropene and 3,3,3-trichloropropene. The ratio was 95.0% in total, and the selectivity was 97.7%.

  In the chlorination step, 160 g of the above-obtained trichloropropene obtained above was dehydrated using 30 g of molecular sieve MS-4A, and then chlorinated without performing distillation purification or the like. Chlorination was performed for 2 hours using a 300 ml flask using a mercury lamp UM-102 manufactured by Ushio Electric Co., Ltd. under ultraviolet light irradiation at a reaction temperature of 25 ° C. for 2 hours. The reaction was stopped by stopping ultraviolet irradiation and stopping chlorine supply, and chlorine in the reaction solution was removed by nitrogen purge for 15 minutes. The obtained crude 1,1,1,2,3-pentachloropropane was analyzed by gas chromatography. As a result, the conversion to 1,1,1,2,3-pentachloropropane was 97.0%, and the selectivity was It was 93.0%. The amount of 1,1,1,3,3-pentachloropropane produced with respect to 1,1,1,2,3-pentachloropropane was 50 ppmw. The purity of this crude product at the stage was 84%.

  The crude 1,1,1,2,3-pentachloropropane thus obtained was subjected to reduced-pressure distillation using a distillation tower filled with an inner diameter of 20 mmφ and a Shibata glass packing of 500 mm inside to obtain 1,1,1,2, Fractions were obtained so that the purity of 3-pentachloropropane was 99.4%. The overall yield from 1,1,1,3-tetrachloropropane was 75%.

Example 2, Comparative Examples 1-3
The reaction was performed in the same manner as in Example 1 except that the reaction time of the dehydrochlorination step and the chlorination step was changed. The conversion, selectivity, and yield are shown in Table 1.

  As is clear from the above results, when chlorination is performed without removing 1,1,1,3-tetrachloropropane by distillation after the dehydrochlorination step, if the conversion rate in the chlorination step is too high, A large amount of 1,1,1,3,3-pentachloropropane is produced (Example vs. Comparative Example 2). Furthermore, this 1,1,1,3,3-pentachloropropane is difficult to remove, and even if the purity is the same at the stage of the crude product, the final yield is reduced (Comparative Example 1 vs. 1). Comparative Example 2).

  In order to reduce the amount of 1,1,1,3-tetrachloropropane, even if the conversion rate in the dehydrochlorination step is increased, the selectivity is extremely deteriorated in this step. It is clear that the total yield cannot be improved.

Claims (2)

1,1,1,3-tetrachloropropane is dehydrochlorinated with alkali to give trichloropropene, and the resulting trichloropropene is reacted with Cl ₂ to produce 1,1,1,2,3- In the method for producing 1,1,1,2,3-pentachloropropane having a chlorination step of pentachloropropane, (1) the conversion rate of 1,1,1,3-tetrachloropropane in the dehydrochlorination step is 99. 0.5% or less, (2) the reaction product trichloropropene is subjected to a chlorination step in a state containing unreacted 1,1,1,3-tetrachloropropane, and (3) in the chlorination step A process for producing 1,1,1,2,3-pentachloropropane, wherein the conversion rate of trichloropropene is 97% or less. Chlorination by reacting trichloropropene containing 1,1,1,3-tetrachloropropane as an impurity (but 1,1,3-trichloropropene and / or 3,3,3-trichloropropene) with Cl ₂ A process for producing 1,1,1,2,3-pentachloropropane, wherein the conversion rate of the trichloropropene in the chlorination step is 97% or less. , 2,3-pentachloropropane production method.