JP2009023956A - Phosgenation method and phosgenation apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems wherein, when phosgenation is carried out on a large scale, the amount of unreacted phosgene gas discharged into exhaust gas to be disposed together with waste gas and the amount of catalysts used are unnegligibly large and that complete recovery and effective utilization thereof are required. <P>SOLUTION: The exhaust gas generated by phosgenation is introduced into an exhaust phosgene-trapping tank, in which reaction raw materials for the next batch have been charged, and phosgene gas in the exhaust gas is completely absorbed thereby permitting effective utilization while the catalyst, VM reagent, is subjected to recycle use at least four times. Thus, the phosgenation method is environmentally friendly and efficient. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing an acid chloride by phosgenating a carboxylic acid and an apparatus for performing the phosgenation.

The conventional methods known to produce saturated acid or unsaturated fatty acids or carboxylic acids such as aromatic or heterocyclic rings with phosgene gas to produce the corresponding acid chlorides are the carboxylic acid and solvent as the reaction raw materials. Alternatively, most of the methods include adding a catalyst in the absence of a solvent and blowing phosgene gas to neutralize exhaust gas containing excess phosgene gas. Neutralization of exhaust gas requires neutralization of by-produced hydrogen chloride gas and unreacted phosgene gas, and an alkali agent is used as a neutralizing agent (see, for example, Patent Document 1).
JP-A-6-319946 (FIG. 1)

  When NaOH is used as a neutralizing agent, 4 moles of NaOH is stoichiometrically required for 1 mole of phosgene, and a huge amount is required. When the phosgenation reaction takes a long time, a large amount of phosgene gas is discharged together with hydrogen chloride, and a large amount of alkali is required for the neutralization treatment.

  For example, when normal phosgenation is carried out, the amount of phosgene used is 1.05 to 1.10 times moles of the theoretical required amount of the raw material to be charged, but the reaction rate is increased when the phosgenation reaction rate is very low. Therefore, in order to increase the reaction temperature, a large reaction time and a large amount of phosgene are required. In addition, the reaction rate may be increased by increasing the amount of a catalyst added as a reaction catalyst for phosgenation, for example, dimethylformamide (referred to as DMF), but the reaction rate increases as the amount of the catalyst increases. Separation of the catalyst containing a large amount of phosgene has become complicated, and the resulting reaction solution has become colored, so a purification operation must be added.

  DMF added as a reaction catalyst for phosgenation becomes an active Vilsmeier reagent (referred to as VM) after the completion of the reaction, and is separated from the difference in solubility from the generated reaction solution. Is often discarded. For this reason, there has been a demand for an efficient method for recovering and using VM that is still active and active in recovery and recovery of phosgene gas in exhaust gas in the phosgenation reaction.

  Then, this invention makes it a subject to provide the phosgenation method and phosgenation apparatus which can eliminate the above-mentioned malfunction in view of said problem.

  In order to solve the above-mentioned problems, the phosgenation method according to the present invention comprises a phosgene for producing acid chloride by reacting a carboxylic acid and a catalyst charged in a reaction vessel with phosgene gas in the absence of a solvent or in the presence of a solvent. In the conversion method, the carboxylic acid and catalyst to be filled in the next reaction tank are charged in advance into the reaction exhaust gas collection equipment with a solvent or no solvent, and the phosgene gas in the exhaust gas discharged from the reaction tank is collected and reacted. It is characterized by being introduced into an exhaust gas collection facility.

  The exhaust gas discharged during the first phosgenation reaction is led to a reaction exhaust gas collection facility in which carboxylic acid, which is a raw material for the next reaction, is charged, and phosgene gas in the exhaust gas is absorbed. On the other hand, the phosgenation reaction liquid obtained in the first phosgenation reaction and the VM reagent produced from the catalyst are separated, the phosgenation reaction liquid is transferred to the next step, and the VM reagent contains the carboxylic acid as the next reaction raw material. In the state of being charged into the reaction exhaust gas collection facility that has been charged, it is transferred again to the reaction vessel, and the next phosgenation reaction is performed.

  For example, when phosgenating butyric acid, which is an example of saturated fatty acid, as carboxylic acid, butyric acid and DMF catalyst are charged to the reaction tank as the initial charge, and used as the raw material for the next reaction in the reaction exhaust gas collection facility that receives the reaction exhaust gas After butyric acid and DMF catalyst are charged, phosgenation is started in the reaction vessel. The catalyst used in the phosgenation reaction is converted into a VM reagent by phosgenation and becomes an active colored liquid.

  Since the produced active VM catalyst does not decrease the reaction activity even when it is recycled, it is recycled at least four times. If it is used four times, the reaction product is separated from the reaction product, then it is decomposed and neutralized for disposal, transferred to a separate wastewater treatment facility and processed. The phosgenation temperature is appropriately selected depending on the solvent used, the physical properties of the raw materials, the reaction rate, and the like, but it is generally better to carry out the reaction at 80 ° C. or lower. Since the phosgenation reaction is a gas-liquid contact reaction, a high reaction temperature is not preferable as a reaction condition. If possible, it is more appropriate to carry out at 50 ° C. or lower.

  The cooling water for the phosgenation tank is usually preferably 10 to 20 ° C. so that the cooling water is 50 ° C. or lower. The reaction exhaust gas collection facility is set to a temperature similar to or slightly lower than that of the reaction tank, and the raw carboxylic acid is showered and circulated so as to improve the gas-liquid contact effect. It is appropriate to cool the condenser attached to the reaction tank, the condenser suspended in the collection can and the condenser attached in a connected manner with brine. The cooling temperature of the VM tank for stocking the VM reagent separated and separated in the reaction tank is 15 to 20 ° C. If this temperature is low, the possibility that the VM precipitates as a crystal and solidifies increases, so a very low temperature is not preferable. Further, since the VM reagent is active and hygroscopic, it is necessary for the VM tank to maintain a condition that is shielded from moisture.

  The reaction tank is preferably made of glass-lined inner surface coated with glass (referred to as GL), and the attached exhaust gas separator is made of GL and separates the mist of butyric acid and butyric acid chloride accompanying the exhaust gas rising from the reaction tank. However, it is better not to fill the filler because filling it with a gas pressure resistance. The phosgenation tank condenser to be provided is preferably made of a material member that has a good cooling effect and excellent acid resistance. The reaction exhaust gas collecting equipment is preferably made of GL, and the vertically suspended condenser is filled with magnetic Raschig ring, and the effect of collecting phosgene is improved by gas-liquid contact.

  The exhaust phosgene condenser to be provided is preferably an acid-resistant material member filled with magnetic Raschig rings. The connected exhaust gas separator is preferably made of GL, and collects butyric acid and butyric chloride that are scattered with hydrogen chloride. The DMF charging tank charged into the reaction exhaust gas collection facility may be made of SUS material. The VM reagent whose activity has been reduced by recycling is separated, transferred to a VM storage tank, allowed to stand, decomposed, and transferred to a separate wastewater treatment facility for disposal.

  According to the present invention, the unreacted phosgene gas of the exhaust gas discharged by the phosphination reaction can be introduced into a reaction exhaust gas collection facility charged with carboxylic acid as the next reaction raw material, and the phosgene gas can be completely collected. In addition, since the catalyst VM is recycled at least four times, the amount of catalyst may be small.

  As the main equipment used in the present invention, a GL reaction tank with a stirrer (1), a blow-in pipe from a phosgene vaporizer (15), an exhaust gas separator (2), and a phosgenation tank condenser (3) are arranged around the reaction. It is installed. In addition, an exhaust phosgene collection can (4), an exhaust phosgene collection tower (7), an exhaust phosgene condenser (8) attached vertically to the exhaust phosgene collection can (4), Exhaust gas separator (9), DMF receiving tank (5) from storage tank for charging, butyric acid transfer pipe (6) from a separate butyric acid storage tank, circulation pump (13) for efficiently collecting exhaust gas phosgene during reaction ), A feed pump (12) to the phosgenation tank. In addition, it comprises a VM receiving tank (10) for stationary stocking of the separated VM, a VM decomposition tank (11) for decomposing the VM that has lost its activity, and a pump (14) for transferring the decomposition solution.

The GL reactor (1) with stirrer used is jacketed with a capacity of 5 to 15 m ³ . The rotation speed of stirring is preferably faster in order to improve the contact ratio with the phosgene gas. However, if it is too fast, the outgassing phenomenon occurs, so it may be appropriately determined in the range of 60 to 105 rpm. The vertical exhaust gas separator (2) of the phosgenation tank is for condensing butyric acid and products accompanying the exhaust gas and returning them to the reaction tank, and the capacity is preferably about 100 to 500 liters. Brine cooled to −8 to −10 ° C. in the jacket to solidify.

The exhaust gas transferred to the phosgenation condenser (3) is phosgene, hydrogen chloride gas, and carbon dioxide gas. Since it generates strong corrosiveness when it comes into contact with moisture, the material is carbait and the capacity is 4-8m ³ and the vertical type And cooled with -8 to -10 ° C brine. GL piping members are suitable for all piping connecting around the reaction tank. The waste phosgene collection can (4) is a jacketed GL can with a capacity of 5 to 15 m ³ . Normally, butyric acid, a catalyst and a solvent are circulated in the waste phosgene collection can, but it can of course be used without a solvent.

The waste phosgene collection tower suspended from the upper part of the waste phosgene collection can is filled with Raschig rings having a thickness of 1 to 2B. The material of the DMF receiving tank (5) may be SUS304 or SUS316, and the capacity may be about 100 to 300 liters. In the case of butyric acid, butyric acid is circulated and showered by the circulation pump (13) at a flow rate of 500 to 3000 liters / hour, and the exhaust gas discharged from the reaction tank is contacted and reacted. The most suitable material for the waste phosgene condenser (8) connected to the waste phosgene collection can is carpate having excellent acid resistance, and a capacity of 2 to 6 m ³ is sufficient. Further, the exhaust gas separator (9) to be connected may be 100 to 500 liters made of GL.

Both the exhaust phosgene condenser (8) and the exhaust gas separator (9) are cooled with brine at -8 to -10 ° C. A GL piping member is suitable for the connecting piping around the exhaust phosgene collection can. When the phosgenation reaction is completed, the VM reagent is separated, transferred to the VM receiving tank (10), and reused for the next reaction. The material of the VM receiving tank (10) may be SUS316, but a GL tank is suitable and the capacity may be about 100 to 400 liters. After completion of the reaction, the catalyst is separated by separating the VM reagent from the reaction solution by a valve that is sensed by a capacitance method or an electromagnetic conductivity method. The VM reagent, which cannot be used for separation and recycling, is transferred to a VM decomposition tank (11) having a capacity of 2 to 5 m ³ and slowly decomposed under stirring with cooling water of about 15 to 25 ° C. When the decomposition is completed, it is transferred to a drainage facility separately installed by a VM decomposition tank pump (14) and subjected to wastewater treatment.

  As the next reaction, the reaction solution after completion of phosgenation in the reaction tank (1) is transferred to the next step, and the contents of the waste phosgene collection can (4) are transferred to the reaction tank (1) by the feed pump (12). . For example, a transfer time of about 6500 liters / 35 minutes is required to transfer the reaction raw material added with butyric acid and DMF to the reaction tank (1). Phosgene gas is blown into the reaction tank (1) through a pipe (15) from a separately installed phosgene vaporizer.

  The exhaust gas discharged from the exhaust phosgene collection can through the exhaust phosgene condenser and exhausted through the exhaust gas separator is sucked in under a moderately reduced pressure during the reaction, and the sensor detects that the suction pressure of the exhaust gas piping system changes at the end of the reaction. A system is built into the computer to determine the end point of conversion.

  According to the method of the present invention in which reaction exhaust gas is introduced into an exhaust phosgene collection can and effective utilization of phosgene gas for the next reaction is performed, when the amount of liquid phosgene introduced into the vaporizer is phosgenated at 200 liters / hour, Since there is no phosgene collection can and it contributes to shortening the phosgenation reaction time by 2 hours or more as compared with the method of neutralizing exhaust gas as it is, it can be said that the method becomes more effective and effective when the scale is increased.

EXAMPLES Next, an Example is given and this invention is demonstrated still in detail.
Example 1

Butyric 6,200 liters with transfer pump from the material storage tank (specific gravity 0.960 / 20 ℃, 5952Kg, 67.55kmol ) and, DMF40 liters discharge phosgene collecting cans (specific gravity 0.9445 / 25 ℃, 37.8kg) of 8m ³ (GL can) was charged and transferred to an 8 m ³ phosgenation tank (GL tank) after pump circulation using a transfer pump over a time of 6200 liters / 34 minutes. Again, 6200 liters of butyric acid and 40 liters of catalyst DMF were charged into the waste phosgene collector, and circulation showering was started at a flow rate of 2000 liters / hour by a circulation pump.

  On the other hand, the phosgenation tank charged with the transferred butyric acid and DMF reaction raw materials was stirred and heated with steam to adjust the temperature of the reaction tank to 42.5 ± 1 ° C. Liquid phosgene was supplied at a rate of 190 liter / hour to a separately installed phosgene vaporizer, and vaporized phosgene gas was blown into the phosgenation tank for 25 hours. At the end of the reaction, the phosgene gas was stopped by capturing the change in the suction pressure of the exhaust gas system.

  During this time, the temperature of the reaction vessel was automatically controlled to maintain the reaction temperature with cooling water of 18 to 20 ° C. The gas separator and condenser around the reaction vessel and the waste phosgene collection can were cooled with brine at -8 to -10 ° C. The temperature of the exhaust phosgene collector can be steam-heated to 41 to 43 ° C. before the start of the reaction, and then the steam is stopped, balanced with the heat of reaction with the phosgene gas in the exhaust gas, and kept at the same temperature without cooling. did it. The amount of phosgene was checked by sampling in the return pipe to the exhaust phosgene collection can of the exhaust gas separator, but no phosgene was present. Since the phosgenation reaction was completed, the VM reagent and butyric acid chloride were separated using a capacitive separation interface detector installed at the outlet of the reaction vessel.

  The amount of VM separated was 60 liters. The produced 7010 liters of butyric chloride (specific gravity 1.023 / 20 ° C., 7171 Kg, 67.27 kmol) was transferred by a transfer pump for use in the next step. The butyric acid chloride production yield was 99,6 mol%.

6200 liters of raw material that absorbed exhaust gas phosgene in the waste phosgene collection can was transferred to the phosgenation tank, and 60 liters of the VM reagent in the VM receiving tank was transferred to the waste phosgene collection can to prepare for the next phosgenation reaction. Similarly the VM reagent can not be used as a reaction catalyst was reduced reaction activity after repeated 4 times the phosgenation reaction placed together with water in the 1.5 m ³ in VM decomposition tank of 3m ^3, the disassembled it takes 3 hours Then, after neutralizing, transferring to a separate drainage collecting tank, processing, and then transferring to a wastewater treatment facility.

  (Example 2)

In the same manner as in Example 1, 5030 liters (67.63 kmol) of propionic acid and 61 liters (1.16 mol%) of DMF were placed in an 8 m ³ phosgenation tank and stirred and maintained at 40 ± 1 ° C. 1680 liters (22.6 kmol) of propionic acid and 55 liters of DMF were charged into a waste phosgene collection can, and warmed gently while maintaining the temperature of 40 to 42 ° C. while circulating through a bomb. Liquid phosgene was supplied to the vaporizer at 190 liters / hour, and phosgene gas was blown in at a blowing speed of 66 Nm ³ / hour for 25 hours and 51 minutes to complete the reaction. The amount of phosgene introduced was 703.9 kg (71.10 kmol) and was 103.9 mol%.

  The amount of phosgene was analyzed by sampling in the return pipe to the exhaust phosgene collection can of the exhaust gas separator as in Example 1, but no phosgene was present. The recovery rate as hydrochloric acid was 106.4 mol% with respect to phosgene. The yield was 6092 kg of propionic acid chloride, and the solid yield was 97.7%.

  (Comparative example)

The reaction was carried out under the same reaction conditions as in Example 1 except that 6200 liters of butyric acid was placed in a reaction vessel equipped with a GL stirrer having a volume of 18 m ^{3 and} no waste phosgene collector was used. The phosgenation time required 28 hours, and compared with the exhaust gas treatment method using a waste phosgene collection can, the result of blowing in excess of 380 kg in terms of the amount of liquid phosgene used was obtained.

Compared with the reaction method using the waste phosgene collection can equipment, the 10% NaOH solution used for the detoxification equipment required 6.5 m ³ extra.

  In addition, this invention is not limited to an above-described form, You may add a various change in the range which does not deviate from the summary of this invention.

The figure which shows the structure of one embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reaction tank 2 Exhaust gas separator 3 Phosgenation tank condenser 4 Drain phosgene collection can 5 DMF receiving tank 6 Butyric acid transfer piping 7 Waste phosgene collection tower 8 Exhaust phosgene condenser 9 Exhaust gas separator 10 VM receiving tank 11 VM decomposition tank 12 Charge pump 13 Circulation pump 14 VM decomposition tank pump 15 Phosgene blow-in piping

Claims (5)

  In the phosgenation method for producing acid chloride by allowing phosgene gas to act on the carboxylic acid and catalyst filled in the reaction vessel in the absence of solvent or in the presence of a solvent, the carboxylic acid and catalyst to be filled in the next reaction vessel In a reaction exhaust gas collection facility in a solvent or without a solvent, phosgene gas in exhaust gas discharged from the reaction tank is collected, and introduced into the reaction exhaust gas collection facility .   The phosgenation method according to claim 1, wherein the carboxylic acid and the catalyst are circulated in the reaction exhaust gas collection equipment in the absence of a solvent or in the presence of a solvent to absorb and collect the phosgene gas in the exhaust gas. .   The phosgenation method according to claim 1 or 2, wherein the catalyst is recovered after completion of the phosgenation reaction in the reaction tank, and the recovered catalyst is recycled at least four times.   4. The phosgenation method according to claim 3, wherein the catalyst is separated and recovered using the difference in capacitance or the difference in electromagnetic conductivity when the catalyst is recovered.   In a phosgenation apparatus comprising a pipe for introducing phosgene gas into a reaction tank for storing a carboxylic acid and a catalyst filled in the reaction tank in the absence of a solvent or in the presence of a solvent, and phosgenating carboxylic acid in the reaction tank, A reaction exhaust gas collection facility for storing the carboxylic acid and catalyst to be filled in the next reaction tank in a solvent or without solvent is provided, and phosgene gas in the exhaust gas discharged from the reaction tank is collected to collect the reaction exhaust gas. A phosgenation apparatus provided with exhaust gas introduction means for introduction into a collection facility.

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