JP2011116721A - Method for treating alkylene oxide and method for producing hydroxyalkyl (meth)acrylate using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alkylene oxide treatment method which can efficiently treat unreacted alkylene oxide remaining in producing a hydroxyalkyl (meth)acrylate by reacting (meth)acrylic acid with an alkylene oxide. <P>SOLUTION: First, a gas containing at least an alkylene oxide is allowed to be absorbed in an absorbent solution containing an alkylene glycol, next, the alkylene oxide absorbed in the absorbent solution is hydrated in the presence of a catalyst to form an alkylene glycol, and then the hydrate solution containing the alkylene glycol is recovered. When the alkylene oxide-containing solution is treated, the alkylene oxide in the alkylene oxide-containing solution is first vaporized. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for treating alkylene oxide and a method for producing hydroxyalkyl (meth) acrylate using the same.

  Conventionally, hydroxyalkyl (meth) acrylates are synthesized by reacting (meth) acrylic acid with alkylene oxide. In this reaction, in order to increase the reaction rate of (meth) acrylic acid as much as possible, in general, an excess amount of alkylene oxide over (meth) acrylic acid is supplied to the reactor. Accordingly, unreacted alkylene oxide remains in the reaction solution after the reaction is completed, and it is necessary to perform a treatment for separating the alkylene oxide from the reaction solution and discarding or reusing it.

  In Patent Document 1, unreacted alkylene oxide in a reaction liquid obtained by addition reaction of (meth) acrylic acid and alkylene oxide is vaporized and absorbed in (meth) acrylic acid, and then the absorption liquid is subjected to an addition reaction. Describes how to reuse it. Patent Document 2 describes a method in which unreacted alkylene oxide in a reaction solution is diffused and absorbed in water, and then the absorption solution is used for the production of alkylene glycol.

JP-A-10-330320 JP 2002-114740 A

  However, in the method of Patent Document 1, since the amount of (meth) acrylic acid used as the absorbent is limited by the molar ratio of the reaction, all unreacted alkylene oxide in the reaction solution is converted into (meth) acrylic acid. It was difficult to absorb. Therefore, the alkylene oxide that has not been absorbed must be separately absorbed in water and hydrated to form a dilute aqueous alkylene glycol solution, which is then treated with activated sludge. The method of Patent Document 2 cannot be carried out without an alkylene glycol production plant, and also absorbs unreacted alkylene oxide into water and hydrates it to form a dilute aqueous alkylene glycol solution. After that, it was necessary to treat activated sludge.

  The present invention provides an alkylene oxide treatment method capable of efficiently treating unreacted alkylene oxide remaining when a hydroxyalkyl (meth) acrylate is produced by reacting (meth) acrylic acid with alkylene oxide. With the goal. Moreover, an object of this invention is to provide the method of manufacturing a hydroxyalkyl (meth) acrylate, processing an unreacted alkylene oxide efficiently.

  The present invention includes (a) a step of absorbing a gas containing at least an alkylene oxide in an absorption solvent containing an alkylene glycol to obtain an absorption solution containing the alkylene oxide, and (b) an alkylene oxide contained in the absorption solution. Is hydrated in the presence of a catalyst to obtain a hydration liquid containing alkylene glycol hydrated with the alkylene oxide, and (c) a process for recovering the hydration liquid. It is.

  The present invention also provides a step of reacting (meth) acrylic acid and alkylene oxide to obtain hydroxyalkyl (meth) acrylate, and a step of treating unreacted alkylene oxide by the above method ( It is a manufacturing method of (meth) acrylate.

  According to the present invention, unreacted alkylene oxide remaining when a hydroxyalkyl (meth) acrylate is produced by reacting (meth) acrylic acid with an alkylene oxide can be efficiently treated. Moreover, according to this invention, a hydroxyalkyl (meth) acrylate can be manufactured, processing an unreacted alkylene oxide efficiently.

It is a schematic block diagram of the apparatus used for manufacture of the hydroxyalkyl (meth) acrylate using the processing method of the alkylene oxide which concerns on this invention. It is a schematic block diagram of the apparatus used for manufacture of the hydroxyalkyl (meth) acrylate using the processing method of the alkylene oxide which concerns on this invention.

  1 and 2 are schematic configuration diagrams of an apparatus used for production of hydroxyalkyl (meth) acrylate using the method for treating alkylene oxide according to the present invention.

  First, (meth) acrylic acid and alkylene oxide are reacted in the presence of a catalyst in the synthesis reactor 10 to obtain hydroxyalkyl (meth) acrylate. Although it does not specifically limit as alkylene oxide, Preferably it is C2-C6, More preferably, it is C2-C4 alkylene oxide, Especially preferably, ethylene oxide and propylene oxide are mentioned.

  In addition, the reaction of (meth) acrylic acid and alkylene oxide can utilize a well-known method, Usually, (meth) acrylic acid and alkylene oxide are addition-reacted in presence of a catalyst and a polymerization inhibitor. In this reaction, since it is difficult to separate the raw material (meth) acrylic acid and the product hydroxyalkyl (meth) acrylate, the reaction is usually carried out at a molar ratio of alkylene oxide to (meth) acrylic acid of 1 or more (meth). Consume as much acrylic acid as possible. Therefore, since an excess amount of alkylene oxide exists at the end of the reaction, it is separated from the reaction solution by operations such as diffusion, vacuum degassing and distillation.

  In the present invention, for example, the unreacted alkylene oxide remaining when the hydroxyalkyl (meth) acrylate is produced by reacting (meth) acrylic acid with alkylene oxide is represented by steps (a) to (c) shown below. Process. This treatment method can be carried out either continuously or batchwise depending on the reaction mode for obtaining the hydroxyalkyl (meth) acrylate. However, the process stability of the emission and absorption operations, and the viewpoint that the operation management is easy. From the above, it is preferable to carry out continuously.

[Step (a)]
In the step (a), a gas containing at least an alkylene oxide is absorbed in an absorption solvent containing an alkylene glycol. If the alkylene oxide to be treated is gaseous, step (a) can be carried out as it is. If the alkylene oxide to be treated is a liquid alkylene oxide-containing liquid, before the step (a), the alkylene oxide in the alkylene oxide-containing liquid is vaporized to obtain a gas containing at least the alkylene oxide (step (e )), And at least the gas containing alkylene oxide is preferably used in step (a). Furthermore, even if the alkylene oxide to be treated is in a gaseous state, a step of cleaning the gas containing the alkylene oxide to obtain an alkylene oxide-containing liquid (step (f)) is performed, and the alkylene oxide-containing liquid is subjected to the step ( It can also be used in e). Here, “cleaning the gas containing alkylene oxide” means that the alkylene oxide in the gas containing alkylene oxide is absorbed in the cleaning solvent by an absorption operation, and other non-condensable gases such as nitrogen and air are used. This means that part or all of the alkylene oxide is separated.

  For example, in FIG. 1, when (meth) acrylic acid and alkylene oxide are reacted in the synthesis reactor 10, exhaust gas containing unreacted alkylene oxide is generated. The exhaust gas is recovered via the vacuum generator 11, and the exhaust gas is introduced into the cleaning tower 20 through the exhaust gas introduction line 15. In FIG. 2, a reaction liquid containing unreacted alkylene oxide is introduced into the deaeration tower 13 through the reaction liquid supply line 12. A degassing gas is supplied to the degassing tower 13 from a degassing gas line 31 to obtain an exhaust gas containing alkylene oxide in the reaction solution. The crude product from which the alkylene oxide has been removed from the reaction solution is discharged from the crude product line 17. The exhaust gas is introduced into the cleaning tower 20 through the exhaust gas introduction line 15. A cleaning solvent is supplied to the cleaning tower 20 from a cleaning solvent supply line 21, and exhaust gas containing alkylene oxide can be cleaned. The cleaned exhaust gas is discharged from the exhaust gas discharge line 22 to the atmosphere.

  The cleaning solvent may be any liquid that can absorb the alkylene oxide contained in the exhaust gas. Specific examples of the cleaning solvent include water, (meth) acrylic acid, and hydroxyalkyl (meth) acrylate, but water is particularly preferable in consideration of environmental measures and safety. If a solvent other than water is used as the cleaning solvent, the cleaning solvent gas is discharged from the exhaust gas discharge line 22 at the top of the cleaning tower 20 to the atmosphere, and thus further countermeasures are required. When water is used as the cleaning solvent, it does not affect the environment even if it is discharged from the exhaust gas discharge line 22 to the atmosphere.

  The cleaning liquid that has absorbed the alkylene oxide contained in the exhaust gas is introduced into the diffusion tower 30 through the cleaning liquid line 25. The stripping gas is supplied to the stripping tower 30 from the stripping gas supply line 31, and the alkylene oxide can be vaporized. The cleaning liquid that has not been vaporized is discharged from the cleaning liquid discharge line 32. The discharged cleaning liquid may be discarded after being subjected to activated sludge treatment or the like, if necessary, or supplied to the cleaning tower 20 through the cleaning solvent supply line 21 and reused as the cleaning liquid.

  As the diffusion gas, any gas that can dissipate alkylene oxide contained in the cleaning liquid may be used. Specific examples of the stripped gas include an inert gas such as nitrogen, argon, and helium, an oxygen-containing gas such as air or air diluted with an inert gas, or water vapor. There is no problem even if a reboiler is provided at the bottom of the stripping tower 30 instead of using the steam as the stripping gas, and the tower bottom liquid is heated and evaporated by exchanging heat between the steam for heating and the bottom liquid of the stripping tower 30. .

  Note that an alkylene oxide-containing drain line 26 can be connected to the cleaning liquid line 25. By doing so, an alkylene oxide-containing liquid such as waste water discharged from a device that recovers the alkylene oxide released from the ejector waste water or tank containing unreacted alkylene oxide separated from the reaction liquid by the ejector or ejector, etc. The alkylene oxide can be introduced into the stripping tower 30, and the alkylene oxide can be vaporized in the same manner as described above.

  The vaporized alkylene oxide is introduced into the absorption tower 40 through the diffusion gas line 35. The absorption tower 40 is supplied with an absorption solvent from an absorption solvent supply line 41, and the alkylene oxide can be absorbed by the absorption solvent. The emitted gas that has not been absorbed may be released to the atmosphere, but it is preferable to supply it to the cleaning tower 20 through the emitted gas circulation line 42 and perform washing again.

  When the steps (e) and (f) are not performed, the exhaust gas recovered from the synthesis reactor 10 may be directly introduced into the absorption tower 40.

  As the absorbing solvent, a solvent containing alkylene glycol is used. Specific examples of the alkylene glycol include ethylene glycol and propylene glycol. The alkylene glycol contained in the absorbing solvent may be one type or two or more types. The absorbing solvent may be only alkylene glycol, but may be a mixed solvent of alkylene glycol and another absorbing solvent. Considering that the alkylene oxide is hydrated in a later step, it is preferable that an alkylene glycol corresponding to at least the alkylene oxide to be absorbed is contained. Here, the alkylene glycol corresponding to the alkylene oxide means an alkylene glycol formed by hydrating an alkylene oxide, such as ethylene glycol for ethylene oxide and propylene glycol for propylene oxide. The other absorbing solvent is not particularly limited as long as it can absorb the alkylene oxide, but water is particularly preferable in consideration of hydrating the alkylene oxide in the subsequent step. The proportion of alkylene glycol corresponding to the alkylene oxide to be absorbed in the absorbing solvent is preferably 15% by mass to 100% by mass.

  The absorbing solution in which the alkylene oxide has been absorbed is discharged from the absorbing solution line 45.

  Here, the apparatus used for the washing tower, the diffusion tower, the absorption tower, and the deaeration tower is not particularly limited, and generally used packed tower, bubble bell tower, perforated plate tower, and the like can be used. The operation pressure may be any of reduced pressure, normal pressure, and increased pressure, but is preferably -10 kPaG to 10 kPaG, more preferably -5 kPaG to 5 kPaG. The temperature of the cleaning solvent and the absorbing solvent is not particularly limited, but is 0 ° C. to 50 ° C., more preferably 10 ° C. to 45 ° C. from the viewpoint of efficiently absorbing the gas.

[Step (b)]
In step (b), the alkylene oxide contained in the absorbing solution is reacted with water in the presence of a catalyst to produce alkylene glycol. For example, in FIG. 1, the absorbing solution in which the alkylene oxide is absorbed is introduced into the hydration reactor 50 through the absorbing solution line 45. Water for hydrating the absorbed alkylene oxide may be newly supplied to the absorption liquid line 45 (not shown), or water supplied as an absorption solvent from the absorption solvent supply line may be used. Alkylene oxide contained in the absorbing solution becomes alkylene glycol mainly by hydration in the hydration reactor 50.

  The hydration reaction is carried out under known conditions, and usually sulfuric acid or a strongly acidic ion exchange resin can be used as a catalyst. The apparatus used in the hydration reactor varies depending on the catalyst used, and examples thereof include a tubular reactor, a tank reactor, and a packed tower reactor. The reaction temperature is 10 ° C. to 90 ° C., more preferably 20 ° C. to 70 ° C., in order to sufficiently perform the hydration reaction.

  The hydrating liquid thus obtained is discharged from the hydrating liquid line 55.

  This hydrating liquid is preferably reused as the absorbing solvent in step (a). For example, in FIG. 1, by switching the liquid distributor 60 so that the hydrating liquid line 55 and the hydrating liquid circulation line 61 communicate with each other, the hydrating liquid is supplied again to the absorption tower 40 through the absorbing solvent supply line 41. can do.

[Step (c)]
In step (c), the hydration liquid is recovered. For example, in FIG. 1, the hydrating liquid can be recovered from the hydrating liquid discharge line 65 by switching the liquid distributor 60 so that the hydrating liquid line 55 and the hydrating liquid discharge line 65 communicate with each other. .

  Since the recovered hydration liquid contains alkylene glycol at a high concentration, it can be burned (step (d)). The heat of combustion in the step (d) can be used as a heat source necessary for the process, or can be used as a fuel for a boiler that generates steam used in the process, and the load of activated sludge treatment can be greatly reduced. Even when the production plant is not provided, the alkylene oxide can be effectively utilized.

DESCRIPTION OF SYMBOLS 10 Synthetic reactor 11 Vacuum generator 12 Reaction liquid supply line 13 Deaeration tower 15 Exhaust gas introduction line 16 Deaeration gas line 17 Crude product line 20 Cleaning tower 21 Cleaning solvent supply line 22 Exhaust gas discharge line 25 Cleaning liquid line 26 Drain containing alkylene oxide Line 30 Stripping tower 31 Stripping gas supply line 32 Cleaning liquid discharge line 35 Stripping gas line 40 Absorption tower 41 Absorbing solvent supply line 42 Stripping gas circulation line 45 Absorption solution line 50 Hydration reactor 55 Hydration liquid line 60 Liquid distributor 61 Water Japanese liquid circulation line 65 Hydration liquid discharge line

Claims (7)

(A) absorbing at least an alkylene oxide-containing gas in an absorption solvent containing alkylene glycol to obtain an absorption solution containing the alkylene oxide;
(B) hydrating the alkylene oxide contained in the absorbing solution in the presence of a catalyst to obtain a hydrated liquid containing alkylene glycol hydrated with the alkylene oxide;
(C) A method for treating alkylene oxide, comprising a step of recovering the hydrating liquid.   The processing method of the alkylene oxide of Claim 1 which reuses the hydration liquid which passed through the said process (b) as an absorption solvent of the said process (a). (D) The processing method of the alkylene oxide of Claim 1 or 2 which further has the process of burning the hydration liquid collect | recovered at the said process (c). Prior to step (a),
(E) The method further comprises the step of vaporizing the alkylene oxide in the alkylene oxide-containing liquid to obtain a gas containing at least an alkylene oxide, and using the gas containing at least the alkylene oxide in the step (a). 4. The processing method of the alkylene oxide in any one of 3. Prior to step (e),
(F) The process of the alkylene oxide of Claim 4 which further has the process of wash | cleaning the gas containing an alkylene oxide and obtaining an alkylene oxide containing liquid, and using this alkylene oxide containing liquid in the said process (e). Method.   The alkylene oxide treatment method according to claim 5, wherein the gas containing at least the alkylene oxide is absorbed in water as a cleaning solvent as the cleaning operation in the first step (f). Reacting (meth) acrylic acid and alkylene oxide to obtain hydroxyalkyl (meth) acrylate;
The manufacturing method of the hydroxyalkyl (meth) acrylate which has a process of processing an unreacted alkylene oxide by the method in any one of Claims 1-6.

Images