KR20160057928A

KR20160057928A - Process for continuous recovering (meth)acrylic acid and apparatus for the process

Info

Publication number: KR20160057928A
Application number: KR1020140159168A
Authority: KR
Inventors: 민윤재; 백세원; 송종훈; 유설희
Original assignee: 주식회사 엘지화학
Priority date: 2014-11-14
Filing date: 2014-11-14
Publication date: 2016-05-24
Also published as: WO2016076559A1

Abstract

The present invention relates to a continuous recovery method of (meth)acrylic acid and an apparatus used to the recovery method. According to the present invention, the continuous recovery method of (meth)acrylic acid enables stable management and energy reduction of the process and, particularly, reduces the load of an extraction process on a (meth)acrylic acid aqueous solution while reducing the amount of feed treated at the extraction process and reduction of the amount of solvent used for extraction. The continuous recovery method of (meth)acrylic acid comprises: an absorption process; a phase separation process; an extraction process; and a distillation process.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for continuously recovering (meth) acrylic acid,

The present invention relates to a continuous recovery method and apparatus for (meth) acrylic acid.

(Meth) acrylic acid is generally produced by a method of subjecting a compound such as propane, propylene, or (meth) acrolein to a gas phase oxidation reaction in the presence of a catalyst. For example, in the presence of an appropriate catalyst in the reactor, propane, propylene, etc. are converted to (meth) acrylic acid via (meth) acrolein by a gas phase oxidation reaction and (meth) acrylic acid, unreacted propane or propylene Methane A reaction product mixture gas comprising acrolein, inert gas, carbon dioxide, water vapor, and various organic by-products (acetic acid, low boiling point byproduct, high boiling point byproduct, etc.) by the reaction is obtained. The (meth) acrylic acid-containing mixed gas is recovered as an aqueous (meth) acrylic acid solution in contact with an absorption solvent such as process water in a (meth) acrylic acid absorption tower. The (meth) acrylic acid aqueous solution is usually distilled and purified to obtain (meth) acrylic acid.

In order to improve the recovery efficiency of such (meth) acrylic acid, various methods for controlling process conditions or process sequences have been proposed. As a method for separating water and acetic acid from a (meth) acrylic acid aqueous solution obtained from the (meth) acrylic acid absorption tower, a method of azeotropically distilling a distillation column using a hydrophobic solvent is known. As another method, there is known a method in which a (meth) acrylic acid aqueous solution is supplied to an extraction column to obtain a (meth) acrylic acid extract and a residual liquid having a reduced water content, and the extract is distilled to obtain (meth) acrylic acid.

However, according to such a known process, not only the loss rate of (meth) acrylic acid is high in the extraction process and the distillation process, but also flooding occurs due to high processing load of the extraction process, or the temperature profile inside the distillation column becomes unstable There is a problem that the stability of operation is poor.

The present invention is to provide a continuous recovery method of (meth) acrylic acid which improves the efficiency of the extraction process for aqueous (meth) acrylic acid solution and enables stable operation of the process and energy saving.

The present invention also provides an apparatus usable for the continuous recovery method of (meth) acrylic acid.

According to the present invention,

An absorption step of obtaining a (meth) acrylic acid aqueous solution by contacting a mixed gas containing (meth) acrylic acid, an organic by-product and water vapor produced by the synthesis reaction of (meth) acrylic acid with water in a (meth) acrylic acid absorption tower;

A phase separation step of separating the (meth) acrylic acid aqueous solution obtained through the absorption step and the (meth) acrylic acid extract solution obtained through the extraction step described later from the decanter to obtain an organic phase and an aqueous phase;

An extraction step of contacting the aqueous phase obtained by the phase separation step with an extraction solvent in an extraction column to obtain an (meth) acrylic acid extract and an additional residue; And

A distillation step of distilling a feed containing the organic phase obtained through the phase separation step to obtain (meth) acrylic acid

(Meth) acrylic acid.

Further, according to the present invention,

(Meth) acrylic acid, organic by-products, and water vapor produced by the synthesis reaction of (meth) acrylic acid, and a (meth) acrylic acid aqueous solution obtained by contacting the mixed gas with water (Meth) acrylic acid absorption tower (100) equipped with an aqueous solution outlet port;

(Meth) acrylic acid aqueous solution, which is connected through the aqueous solution outlet of the absorption tower 100 and the aqueous solution transfer line 115, through the aqueous (meth) acrylic acid aqueous solution inlet connected to the aqueous solution outlet of the extraction column 200, A decanter 150 having an organic phase outlet through which an organic phase obtained by phase separation of an extracting liquid inlet, an incoming (meth) acrylic acid aqueous solution and an extracting liquid is discharged, and a water outlet for discharging the water phase obtained by the phase separation;

An extract outlet for discharging the (meth) acrylic acid extract solution obtained by contacting the inflow water with the extraction solvent, and an additional outlet for discharging the (meth) acrylic acid extract solution through the water inlet connected to the water outlet of the decanter 150 through the water transfer line 152, (Meth) acrylic acid extraction column 200 equipped with an additional residual liquid outlet; And

(Meth) acrylic acid outlet through which the (meth) acrylic acid obtained by the distillation of the feed containing the introduced organic phase and the organic phase inlet connected to the organic phase outlet of the decanter 150 through the organic phase transfer line 153, (300)

(Meth) acrylic acid.

Hereinafter, the continuous recovery method and recovery apparatus of (meth) acrylic acid according to embodiments of the present invention will be described.

Prior to that, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. And, the singular forms used herein include plural forms unless the phrases expressly have the opposite meaning. Also, as used herein, the term " comprises " embodies specific features, regions, integers, steps, operations, elements or components, and does not exclude the presence of other specified features, regions, integers, steps, operations, elements, It does not.

And, unless expressly stated throughout the present specification, some terms are defined in the following sense.

The term '(meth) acrylic acid' may be used to mean acrylic acid, methacrylic acid or a mixture thereof.

The term '(meth) acrylic acid-containing mixed gas' refers to a mixed gas that can be generated when (meth) acrylic acid is synthesized by a gas phase oxidation reaction. (Meth) acrolein in the presence of a catalyst in the presence of a catalyst in the presence of at least one compound selected from the group consisting of propane, propylene, butane, isobutylene, and (meth) acrolein, Acrylic acid-containing mixed gas can be obtained. At this time, the (meth) acrylic acid-containing mixed gas may contain (meth) acrylic acid, an unreacted raw material compound, (meth) acrolein, inert gas, carbon monoxide, carbon dioxide, water vapor, Heavies, etc.), and the like. Here, the term "light ends" or "high boiling point byproducts" refers to a kind of by-product that can be produced in the production and recovery of a desired (meth) acrylic acid, Small or large compounds are collectively referred to. The non-water-soluble suspended matter formed by the organic by-products is referred to as 'scum'.

The '(meth) acrylic acid aqueous solution' is an aqueous solution containing (meth) acrylic acid, and can be obtained, for example, by bringing the above-mentioned (meth) acrylic acid-containing mixed gas into contact with an absorption solvent containing water.

The term "feed" in the extraction process refers to a liquid mixture containing the solute to be extracted. The term "feed" refers to a solute having solubility in an extraction solvent and other components having no solubility inert material. Here, when the extraction solvent is added to the feed, the solute is dissolved in the extraction solvent from the feed by the mass transfer phenomenon. Accordingly, the extraction solvent in which a large amount of solute is dissolved forms an extract solution, and the feed which has lost a considerable amount of solute forms a raffinate solution.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

On the other hand, in the known (meth) acrylic acid recovery method including the absorption process, the extraction process, and the distillation process for the (meth) acrylic acid-containing mixed gas, the throughput of the extraction process is increased in order to increase the recovery of (meth) , The probability of occurrence of flooding at the upper portion of the extraction column increases. To prevent this, a method of increasing the capacity of the extraction column or changing the internal stirring means of the extraction column (for example, a plate free area of a reciprocating plate column or a blade of a Scheibel column) may be applied. However, it is very expensive to increase the capacity of the extraction column or to change the stirring means. Accordingly, the present inventors conducted a study on a method of improving the treatment efficiency of the extraction process without changing the existing extraction column design in the (meth) acrylic acid recovery method including the absorption process, the extraction process and the distillation process Respectively.

In accordance with the present invention, there is provided a process for producing a water-in-oil type emulsion, comprising: (a) a step of separating an aqueous (meth) acrylic acid solution obtained in an absorption step and a (meth) acrylic acid extract obtained in an extraction step into a decanter, There is provided a method for supplying an aqueous phase to an extraction process and supplying the organic phase to a distillation process. This method can reduce the concentration of (meth) acrylic acid by phase separation in the decanter before supplying the aqueous (meth) acrylic acid solution to the extraction step, thereby reducing the load of the extraction step. That is, unlike the general recovery method in which the (meth) acrylic acid aqueous solution obtained in the absorption step is supplied to the extraction step and the extracted solution is supplied to the distillation step, the (meth) acrylic acid recovery method provided by the present invention, A stream obtained by mixing an acrylic acid aqueous solution and its extract solution is allowed to stand in a decanter to induce phase separation and then the recovered water phase is fed to the extraction step and the remaining organic phase is fed to the distillation step. Accordingly, in the extraction step, the flooding phenomenon can be suppressed even under vigorous agitation conditions in the liquid-liquid extraction, and the feed treatment can be performed in a larger amount per unit time than in the similar-scale extraction column. In addition, this method enables the extraction efficiency to be maintained stably even when the solvent / feed ratio is reduced during the operation of the extraction process, thereby enabling the use of the extraction solvent to be reduced. And this method enables energy savings in the distillation process following the extraction process.

I. ( Mat ) Continuous recovery method of acrylic acid

According to one embodiment of the invention,

(Meth) acrylic acid.

Further, according to an embodiment of the invention,

A phase separation step of separating a part of the (meth) acrylic acid aqueous solution obtained through the above absorption process and the (meth) acrylic acid extract solution obtained through the above extraction step in a decanter to obtain an organic phase and an aqueous phase;

(Meth) acrylic acid obtained by distilling a feed containing the remainder of the aqueous (meth) acrylic acid solution obtained through the absorption process and the organic phase obtained through the phase separation step

(Meth) acrylic acid.

Hereinafter, with reference to FIGS. 1 and 2, each process that can be included in the embodiment of the present invention will be described in detail.

(Absorption process)

The absorption step is a step for obtaining an aqueous solution of (meth) acrylic acid, which can be carried out by a method of bringing the (meth) acrylic acid-containing mixed gas obtained through the synthesis reaction of (meth) acrylic acid into contact with an absorption solvent containing water.

As a non-limiting example, the synthesis reaction of (meth) acrylic acid is carried out by a method of subjecting at least one compound selected from the group consisting of propane, propylene, butane, isobutylene, and (meth) acrolein to an oxidation reaction under a gas phase catalyst . At this time, the gas-phase oxidation reaction can be carried out under a gas-phase oxidation reactor and reaction conditions of a conventional structure. The catalyst in the gas-phase oxidation reaction may also be a conventional one, for example, catalysts disclosed in Korean Patent Nos. 0349602 and 037818 may be used. The (meth) acrylic acid-containing mixed gas produced by the gas-phase oxidation reaction may contain, in addition to (meth) acrylic acid as the objective product, unreacted starting compounds, intermediate (meth) acrolein, inert gas, carbon dioxide, water vapor, , Low boiling point byproducts, high boiling point byproducts, etc.).

1, the (meth) acrylic acid aqueous solution is obtained by supplying a (meth) acrylic acid-containing mixed gas 1 to a (meth) acrylic acid absorption tower 100 and bringing the mixture into contact with an absorption solvent containing water Can be.

Here, the type of the (meth) acrylic acid absorption tower 100 can be determined in consideration of the contact efficiency between the mixed gas (1) and the absorbing solvent. As a non-limiting example, the (meth) acrylic acid absorber 100 may be an absorber of packed column type or a multistage tray type. The absorption column type absorption tower may have a filler such as a rashing ring, a pall ring, a saddle, a gauze, and a structured packing.

In consideration of the efficiency of the absorption process, the mixed gas 1 may be supplied to the lower portion of the absorption tower 100, and the absorption solvent containing water may be supplied to the upper portion of the absorption tower 100.

The absorbing solvent may include water such as tap water, deionized water, and the like, and may include circulating process water introduced from another process (for example, an aquarium that is recycled from the extraction process and / or the distillation process). The absorption solvent may contain a small amount of organic by-products (e.g., acetic acid) introduced from another process. However, considering the absorption efficiency of the (meth) acrylic acid, it is preferable that the absorption solvent (particularly, the circulating process water) supplied to the absorption tower 100 contains 15% by weight or less of organic byproducts.

Considering the condensation conditions of (meth) acrylic acid and the water content depending on the saturated water vapor pressure, etc., the (meth) acrylic acid absorption tower 100 has an internal pressure of 1 to 1.5 bar or 1 to 1.3 bar, Lt; RTI ID = 0.0 > 80 C < / RTI >

On the other hand, in the absorption step, a (meth) acrylic acid aqueous solution is discharged to the lower part of the (meth) acrylic acid absorption tower 100, and noncondensing gas in which (meth) acrylic acid is deaerated is discharged to the upper part. At this time, it may be advantageous in terms of efficiency of the whole process that the (meth) acrylic acid aqueous solution contains 40 wt% or more, or 40 to 90 wt%, or 50 to 90 wt% of (meth) acrylic acid.

The resulting (meth) acrylic acid aqueous solution is supplied to the decanter 150 through the aqueous solution transfer line 115 as shown in FIG. Alternatively, the obtained (meth) acrylic acid aqueous solution may be divided into a decanter 150 and a distillation column 300 through aqueous solution transfer lines 115 and 130 as shown in FIG. 1 and 2, the (meth) acrylic acid aqueous solution obtained in the (meth) acrylic acid absorption tower 100 is not directly supplied to the extraction column 200 but is supplied to the decanter 150, Is supplied to the extraction column 200 in a state where the concentration of (meth) acrylic acid is lowered. The (meth) acrylic acid extract obtained from the extraction column 200 is not directly supplied to the distillation column 300 but is supplied to the distillation column 300 through the decanter 150 and the phase separated organic phase. Here, the flow in the decanter 150 and the extraction column 200 will be separately described.

2, the ratio of feeding the (meth) acrylic acid aqueous solution divided into the decanter 150 and the distillation column 300 is determined by taking into account the improvement of the capacity, the processing performance, and the energy efficiency of each column Can be determined. According to an embodiment of the present invention, 5 to 70% by weight, or 10 to 60% by weight, or 10 to 50% by weight of the (meth) acrylic acid aqueous solution is supplied to the decanter 150, Can be advantageous in minimizing the loss of (meth) acrylic acid and reducing the overall energy consumption.

On the other hand, at least a part of the non-condensable gas discharged to the upper part of the (meth) acrylic acid absorption tower 100 may be supplied to a process of recovering organic by-products (especially acetic acid) contained in the non-condensable gas, And can be discarded. That is, according to one embodiment of the present invention, a process of contacting the non-condensable gas with an absorption solvent and recovering acetic acid contained in the non-condensable gas may be performed. The process of contacting the non-condensable gas with the absorption solvent can be performed in the acetic acid absorption tower (50). As a non-limiting example, an absorption solvent (process water) for absorbing acetic acid may be supplied to the upper portion of the acetic acid absorption tower 50, and an aqueous solution containing acetic acid may be discharged to the lower portion of the acetic acid absorption tower 50 . The acetic acid-containing aqueous solution may be supplied to the upper part of the (meth) acrylic acid absorption tower 100 and used as an absorption solvent. In addition, the non-condensable gas in which the acetic acid is deaerated can be circulated and reused in the synthesis reaction process of (meth) acrylic acid. At this time, for the effective absorption of acetic acid, the acetic acid absorption tower 50 can be operated at an internal pressure of 1 to 1.5 bar or 1 to 1.3 bar and an internal temperature of 50 to 100 ° C or 50 to 80 ° C. In addition, specific operating conditions of the acetic acid absorption tower (50) may be as disclosed in Korean Patent Publication No. 2009-0041355.

(Phase separation process)

On the other hand, the (meth) acrylic acid aqueous solution obtained through the above absorption process and the (meth) acrylic acid extract obtained through the extraction process described below are phase separated in the decanter 150 to perform the phase separation process for obtaining the organic phase and the water phase.

1, an aqueous (meth) acrylic acid solution is supplied to the decanter 150 from the absorption tower 100 through the aqueous solution transfer line 115, and at the same time, the extract liquid transfer line 215 from the extraction column 200 (Meth) acrylic acid extract solution is supplied. Here, the decanter 150 is a device for separating a liquid phase that does not mix with each other by gravity or centrifugal force, and a relatively light phase (for example, an organic phase) is applied to the upper portion of the decanter 350, , Water) is recovered to the lower portion of the decanter 350. [ Here, the organic phase includes an extraction solvent used in the extraction process and (meth) acrylic acid dissolved therein, and the water phase includes an absorption solvent used in the absorption process and (meth) acrylic acid dissolved therein. The organic phase, which is a relatively light phase, is then obtained through the top outlet of the decanter 150 and the aquifer, which is a relatively heavy phase, is obtained through the bottom outlet of the decanter 150. The organic phase is supplied to the distillation column 300 through the organic phase transfer line 153 to separate the solvent and the aqueous phase is supplied to the extraction column 200 through the water phase transfer line 152, .

At this time, the water phase supplied to the extraction column 200 has a (meth) acrylic acid concentration which is significantly lower than that of the (meth) acrylic acid aqueous solution obtained through the absorption process. That is, at least 40%, preferably 40 to 95%, or 40 to 90%, or 50 to 90%, of the (meth) acrylic acid contained in the (meth) acrylic acid aqueous solution supplied to the decanter 150, 90%, or 60-85% of (meth) acrylic acid can be recovered through the organic phase. Therefore, the water phase obtained through the phase separation in the decanter 150 can exhibit a (meth) acrylic acid concentration of a level that is lowered.

By way of non-limiting example, when a (meth) acrylic acid aqueous solution having a concentration of (meth) acrylic acid of about 65% by weight is obtained through the absorption process, at least 40% of the (meth) acrylic acid contained in the aqueous (meth) And may be recovered into the organic phase through phase separation in the adsorption tower 150. The water phase obtained through the phase separation in the decanter 150 may represent a (meth) acrylic acid concentration (for example, a (meth) acrylic acid concentration of about 39% by weight or less) lowered. As described above, the aqueous solution of the (meth) acrylic acid and the extract of the high concentration are phase-separated from the decanter 150, and the aqueous phase having lower (meth) acrylic acid concentration is introduced into the extraction column 200, have. Further, the load of the distillation step can be reduced by feeding the organic phase containing the (meth) acrylic acid at a high concentration obtained through the phase separation to the distillation column 300.

(Extraction process)

On the other hand, the aqueous phase obtained by the phase separation step is contacted with an extraction solvent in an extraction column to carry out an extraction process of obtaining an (meth) acrylic acid extract and an additional residue thereof.

(Meth) acrylic acid aqueous solution obtained in the absorption step is supplied to the extraction step and the extracted solution is supplied to the distillation step, the stream obtained by mixing the aqueous solution of the (meth) acrylic acid and the extract thereof Is allowed to stand in the decanter 150 to induce phase separation, the recovered water phase is supplied to the extraction process, and the remaining organic phase is fed to the distillation process. As a result, a water phase having a lower (meth) acrylic acid concentration is supplied to the extraction process, so that the load of the extraction process can be effectively lowered. That is, in the extraction step, the flooding phenomenon can be suppressed even under vigorous agitation conditions in the liquid-liquid extraction, and the feed throughput that can be processed under a similar-scale extraction column can be increased. Furthermore, this method enables the extraction efficiency to be kept stable even when the solvent / feed ratio is reduced during the operation of the extraction process, thereby reducing the amount of extraction solvent used. In addition, this effect makes it possible to reduce the energy in the distillation step subsequent to the extraction step.

According to an embodiment of the present invention, the aqueous phase fed from the decanter 150 to the extraction column 200 through the water transfer line 152 is contacted with the extraction solvent, and an aqueous solution containing a considerable amount of (meth) acrylic acid dissolved in the extraction solvent (extract solution) and a raffinate solution that lost a significant amount of (meth) acrylic acid. At this time, the extract which is a relatively light phase is obtained through the upper outlet of the extraction column 200, and the additional residue, which is a relatively heavy phase, is obtained through the lower outlet of the extraction column. The residual balance exists in a state in which a certain amount of the residual amount remains in the lower dead zone of the extraction column before being discharged from the extraction column 200, and a part of the residual amount is discharged to the lower outlet of the extraction column.

In the extraction step, the residual balance may be supplied to the decanter 350 through the additional balance transfer line 235 and phase-separated into the water phase and the organic phase together with the upper discharge liquid of the distillation column 300. However, scum may be included in the residual balance. Therefore, it is preferable to filter the residual residue to remove the scum, and then supply the filtrate to the decanter 350 from the viewpoint of ensuring operational stability. Optionally, the balance can also be circulated to the absorption process and used as an absorbing agent for (meth) acrylic acid.

On the other hand, the extraction solvent supplied to the extraction column 200 may have solubility and hydrophobicity with respect to (meth) acrylic acid. However, in view of the physical properties of the azeotropic solvent required in the distillation column 300, which is a subsequent process, it is preferable that the extraction solvent has a boiling point lower than that of (meth) acrylic acid. For example, the extraction solvent may be a hydrophobic solvent having a boiling point of 120 占 폚 or lower, or 10 to 120 占 폚, or 50 to 120 占 폚.

Specifically, the extraction solvent is selected from the group consisting of benzene, toluene, xylene, n-heptane, cycloheptane, cycloheptene, 1- heptene, ethyl-benzene, methyl-cyclohexane, n-butyl acetate, isobutyl acetate, isobutyl acrylate, n-propyl acetate, isopropyl acetate, methyl isobutyl ketone, 2-methyl-1-heptene, 6-methyl- Methyl-1-heptene, 2-ethyl-1-hexene, ethylcyclopentane, 2-methyl-1-hexene, 2,3-dimethylpentane, 5-methyl-1-hexene, ), And isopropyl-butyl-ether (hereinafter referred to as " isopropyl " Can every day for.

The supply amount of the extraction solvent is set so that the extraction solvent weight ratio (solvent / feed ratio) to the aqueous solution fed to the extraction column 200 is 0.8: 1 to 0.8: 2, or 0.8: 1 to 0.8: 1 to 0.8: 1.5, or 0.8: 1 to 0.8: 1.3. That is, since the aqueous phase contains a relatively low concentration of (meth) acrylic acid, the extraction load can be lowered and the extraction efficiency can be maintained stably even when the solvent / feed ratio is reduced during the operation of the extraction process . In particular, since the concentration of (meth) acrylic acid is lowered by phase separation in a decanter before the aqueous (meth) acrylic acid solution is fed to the extraction step, the load of the extraction step can be reduced. For reference, in the extraction process not having a decanter, a weight ratio (extraction solvent: water weight ratio) of 1: 1 or more to the aqueous phase to be supplied to the extraction column must be maintained in order to ensure proper extraction efficiency. However, as in the embodiment of the present invention, in the extraction process including the decanter, excellent extraction efficiency can be obtained even when the extraction solvent is maintained at a weight ratio of 1: 1 or less (for example, 0.8: 1) to the aqueous phase fed into the extraction column have. In other words, it is possible to carry out extraction for larger amounts of feed using the same amount of extraction solvent. As described above, the amount of the extraction solvent used in the extraction process can be reduced, and the amount of the azeotropic solvent to be recovered in the subsequent distillation column 300 can be reduced and the energy consumption can be reduced.

However, when the weight ratio of the extraction solvent is more than 0.8: 2, the extraction efficiency may be improved. However, when an excessive amount of the extraction solvent is used, the loss of (meth) acrylic acid in the distillation column 300 may increase, The reflux flow of the azeotropic solvent may be excessively high.

According to an embodiment of the present invention, the temperature of the aqueous phase fed to the extraction column 200 is advantageously in the range of 10 to 70 ° C in terms of securing extraction efficiency.

As the extraction column 200 in the extraction step, a conventional extraction column according to a liquid-liquid contact method can be used without any particular limitation. By way of non-limiting example, the extraction column 200 may be a Karr type reciprocating plate column, a rotary-disk contactor, a Scheibel column, a Kuhni column, a spray extraction tower tower, a packed extraction tower, a pulsed packed column, and the like.

Through this extraction process, the (meth) acrylic acid extract liquid is discharged to the upper part of the extraction column 200, and the discharged extract liquid is supplied to the decanter 150 through the transfer line 215. That is, the (meth) acrylic acid extract solution obtained in the extraction column 200 is not supplied directly to the distillation column 300 but is supplied to the distillation column 300 through the decanter 150 as a phase separated organic phase. Then, the residual balance is discharged to the lower part of the extraction column 200, and the discharged residual balance is supplied to the decanter 350 through the transfer line 235.

At this time, the extract may contain an extraction solvent, water, and organic by-products in addition to the target compound (meth) acrylic acid. By way of non-limiting example, in a steady state where stable operation has been performed, the extract may contain 30-40 wt% of (meth) acrylic acid, 55-65 wt% of extraction solvent, 1-5 wt% of water, have. That is, most of the water contained in the (meth) acrylic acid aqueous solution (for example, 85% by weight or more of the water contained in the aqueous solution) through the extraction step can be recovered as an additional residual liquid.

The weight balance obtained from the extraction column 200 may be mostly water, and may contain (meth) acrylic acid which is not extracted. However, according to an embodiment of the present invention, the weight balance may contain a concentration of 15 wt% or less or 3 to 15 wt% of (meth) acrylic acid, and the weight of the (meth) acrylic acid The losses can be minimized.

(Distillation process)

On the other hand, a distillation step is performed in which the feed containing the organic phase obtained through the phase separation step is distilled to obtain (meth) acrylic acid.

1, the feed is an organic phase phase separated in decanter 150, and the organic phase is fed from decanter 150 to organic phase feed line 153 to distillation column 300.

And, in the embodiment as shown in FIG. 2, the feed may be a mixture of the remainder of the (meth) acrylic acid aqueous solution supplied from the above-described absorption process and the organic phase fed from the phase separation process described above. In this case, the feed may be fed together at the feed point of the distillation column 300 via the (meth) acrylic acid aqueous solution transfer line 130 and the organic phase transfer line 153.

The feed point to which the feed is fed is advantageously the middle portion of the distillation column 300 and is preferably 40 to 60% of the entire stage from the top of the distillation column 300, Or the like.

The feed supplied to the distillation column 300 is brought into contact with the azeotropic solvent introduced into the upper portion of the distillation column 300, and distillation is performed by evaporation and condensation while being heated to an appropriate temperature.

At this time, in order to efficiently separate the (meth) acrylic acid contained in the feed from the remaining components (for example, water, acetic acid, extraction solvent, etc.), the distillation is preferably performed in an azeotropic distillation method.

The solvent to be applied to the azeotropic distillation method is preferably a hydrophobic azeotropic solvent which can achieve an azeotropic ratio with water and acetic acid and does not have an azeotropic ratio with (meth) acrylic acid. The hydrophobic azeotropic solvent preferably has a boiling point lower than that of (meth) acrylic acid (for example, a boiling point of 120 ° C or less, or 10 to 120 ° C, or 50 to 120 ° C).

Specifically, the hydrophobic azeotropic solvent is selected from the group consisting of benzene, toluene, xylene, n-heptane, cycloheptane, cycloheptene, 1- ethyl-benzene, methyl-cyclohexane, n-butyl acetate, isobutyl acetate, isobutyl acrylate, isobutyl acrylate, n-propyl acetate, isopropyl acetate, methyl isobutyl ketone, 2-methyl-1-heptene, 6-methyl Methyl-1-heptene, 2-ethyl-1-hexene, ethylcyclohexyl, But are not limited to, ethylcyclopentane, 2-methyl-1-hexene, 2,3-dimethylpentane, 5-methyl- hexene and isopropyl-butyl-ether. For at least one can be every day.

In consideration of the production efficiency in accordance with the continuous process, the hydrophobic azeotropic solvent is preferably the same as the extraction solvent in the extraction process. When the same type of solvent is used in the extraction process and the distillation process, at least a portion of the solvent distilled in the distillation column 300 and recovered through the phase separation tank 350 is supplied to the (meth) acrylic acid extraction column 200 And can be reused as an extraction solvent.

Through the distillation process, the components other than the (meth) acrylic acid in the feed are discharged to the upper portion of the distillation column 300 together with the azeotropic solvent, and the (meth) acrylic acid is discharged to the lower portion of the distillation column 300.

At this time, the upper discharge liquid of the distillation column 300 may be supplied to the decanter 350 and reused after a predetermined treatment. As an example, the upper effluent of the distillation column 300 may be separated from the decanter 350 by an aqueous phase comprising an organic phase comprising an azeotropic solvent and water. Here, the separated organic phase may be supplied to the upper end of the distillation column 300 and used as an azeotropic solvent. And, if necessary, at least a portion of the organic phase may be fed to the extraction column 200 and used as an extraction solvent. At least a part of the water phase separated in the decanter 350 may be supplied to the (meth) acrylic acid absorption tower 100 and used as an absorption solvent, and a part thereof may be treated with waste water. The acetic acid may be partially contained in the aqueous phase, and the concentration of the acetic acid contained in the aqueous phase may vary depending on the kind of the azeotropic solvent and the reflux ratio. As a non-limiting example, the concentration of acetic acid in the aqueous phase may be from 1 to 50% by weight, or from 2 to 40% by weight, or from 3 to 30% by weight.

Meanwhile, the (meth) acrylic acid aqueous solution is passed through the (meth) acrylic acid absorption tower 100, the decanter 150, the extraction column 200 and the distillation column 300, May form a dimer or an oligomer. In order to minimize the polymerization of such (meth) acrylic acid, a conventional polymerization inhibitor may be added to the distillation column 300.

In addition, the lower effluent of the distillation column 300 may contain, in addition to (meth) acrylic acid, a high-boiling by-product such as a polymer of (meth) acrylic acid, a polymerization inhibitor, and the like. Accordingly, if necessary, a step of supplying the lower discharge liquid of the distillation column 300 to the high boiling point byproduct separation column 400 may be further performed to separate the high boiling point byproducts contained in the lower discharge liquid. The recovered crude (meth) acrylic acid (CAA) through the above process can be obtained as (meth) acrylic acid (HPAA) of higher purity through an additional crystallization process. At this time, the high boiling point byproduct separation process, the crystallization process, and the like can be performed under ordinary conditions, so the process conditions and the like are not specifically limited.

On the other hand, in such a (meth) acrylic acid recovery method, each of the above-described steps can be carried out organically and continuously. In addition to the above-described steps, processes that can be conventionally performed before, after, or simultaneously with each step can be further included and operated.

In the method for recovering (meth) acrylic acid according to the embodiment of the present invention, each of the above-described processes can be carried out organically and continuously. In addition to the above-described processes, processes that can be conventionally performed before or after each process can be further performed. For example, the aqueous (meth) acrylic acid solution obtained in the (meth) acrylic acid absorption tower 100 is supplied to a separate degassing tower before being supplied to the (meth) acrylic acid extraction column 200, thereby obtaining low boiling point byproducts (acrolein, propionaldehyde, Acetaldehyde, formaldehyde, isopropyl acetate, and the like) may be further performed.

II . ( Mat ) Continuous recovery of acrylic acid

Meanwhile, according to another embodiment of the present invention,

(Meth) acrylic acid.

The continuous recovery device of (meth) acrylic acid according to this embodiment can be operated according to the above-mentioned continuous recovery method of (meth) acrylic acid.

According to an embodiment of the present invention, the distillation column 300 is provided with an aqueous solution inlet connected to the aqueous solution outlet of the absorption tower 100 and the aqueous solution transfer line 130, an organic phase outlet of the decanter 150, (Meth) acrylic acid outlet through which the (meth) acrylic acid is obtained, which is obtained by distillation of an organic phase inlet connected through the inlet 153 and a mixture of the introduced aqueous solution and the organic phase; A part of the (meth) acrylic acid aqueous solution discharged from the absorption tower 100 is supplied to the decanter 150 and the rest of the aqueous (meth) acrylic acid solution is supplied to the distillation column 300.

Basically, the (meth) acrylic acid recovery apparatus includes a (meth) acrylic acid absorption tower 100, a (meth) acrylic acid extraction column 200 and a distillation column 300. Particularly, in the apparatus according to the embodiment of the present invention, the (meth) acrylic acid aqueous solution discharged from the absorption tower 100 and the (meth) acrylic acid extract liquid discharged from the extraction column 200 are supplied to the decanter 150. The organic phase recovered through the phase separation in the decanter 150 is supplied to the distillation column 300 through the transfer line 153 and the aqueous phase is supplied to the extraction column 200 through the transfer line 152. That is, in the (meth) acrylic acid recovery apparatus, the absorption tower 100 and the extraction column 200 are connected via a decanter 150. Likewise, the extraction column 200 and the distillation column 300 are connected via a decanter 150. 2, the absorber 100 and the distillation column 300 may be directly connected through the (meth) acrylic acid aqueous solution conveying line 130. As shown in FIG.

On the other hand, the (meth) acrylic acid absorption tower 100 may be a packed tower or a multistage tray tower for improving contact efficiency between the (meth) acrylic acid-containing mixed gas 1 and the absorbing solvent. Here, the filling column may have a filler such as a rashing ring, a pall ring, a saddle, a gauze, and a structured packing.

As the (meth) acrylic acid extraction column 200, a conventional extraction column according to a liquid-liquid contact method can be applied without particular limitation. By way of non-limiting example, the extraction column 200 may be a Karr type reciprocating plate column, a rotary-disk contactor, a Scheibel column, a Kuhni column, a spray extraction column column, a packed extraction column, a pulsed packed column, etc.

The distillation column 300 may be a pack column or a multi-stage column, preferably a sieve tray column, or a dual flow tray column, in which the filler is contained.

In addition, the acetic acid absorption tower 50, the decanters 150 and 350, the various transport lines, the high boiling point byproduct separation tower 400, and the like may have a conventional structure in the technical field of the present invention.

The continuous recovery method of (meth) acrylic acid according to the present invention makes it possible to operate the process more stably and to save energy, and in particular to reduce the load of the extraction process on the aqueous (meth) acrylic acid solution, This makes it possible to reduce the amount of extraction solvent used.

Figures 1 and 2 schematically show a method and apparatus for continuous recovery of (meth) acrylic acid according to embodiments of the present invention, respectively.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the following examples are intended to illustrate the present invention without limiting it thereto.

Example One

1, a reciprocating plate column equipped with a decanter 150 is prepared as an extracting column 200. The extraction column 200 has a total height of 50 m and a total height of 3 m. The inner diameter of the column corresponding to the first to sixth stages (that is, the upper six stages including the uppermost stage) is 45 mm, The inner diameter of the column corresponding to the 50th step was equal to 22 mm. Of the perforated plates placed on each end of the extraction column 200 and performing vertical repetitive movement, the free area ratio of the perforated plate placed in the first to sixth stages is about 50% The aperture ratios of the perforated plates placed in the 7th to 50th stages are about 28.3%, respectively.

Then, an acrylic acid aqueous solution (concentration of acrylic acid: about 64% by weight) was prepared as a feed, and toluene was prepared as an extraction solvent. The aqueous acrylic acid solution was supplied to the decanter 150 together with the extract of the extraction column 200 and phase separated. The aqueous phase separated in the decanter 150 (acrylic acid concentration: about 5% by weight) was supplied to the extraction column 200, and the remaining organic phase was supplied to the distillation column 300. At this time, the solvent / feed ratio in the extraction column 200 was maintained at about 1.3.

Then, the linear velocity of the continuous phase (organic phase) associated with the feed throughput of the extraction column 200 is increased to 0.4 cm / s, 0.5 cm / s, 0.6 cm / s, 0.8 cm / s, and 1.0 cm / ([Mass of acrylic acid contained in the extract] / [mass of acrylic acid contained in the feed] * 100) of acrylic acid was measured. At this time, the maximum extraction rate at each linear velocity was measured under the condition of the maximum mechanical repetition rate (rpm; that is, the maximum rpm immediately before the flooding phenomenon) of the porous plate, and the results are shown in Table 1 below.

Comparative Example One

A column having the same specifications as the reciprocating plate column used in Example 1 was prepared as an extraction column, except that the decanter 150 was not provided.

Then, an acrylic acid aqueous solution (concentration of acrylic acid: about 64% by weight) was prepared as a feed, and toluene was prepared as an extraction solvent. Acrylic acid aqueous solution and toluene were fed to the feed inlet of the extraction column (corresponding to the water inlet of Example 1) and the solvent inlet. Then, the extract obtained in the extraction column was supplied to the distillation column. At this time, the solvent / feed ratio in the extraction column was maintained at about 1.3.

The linear velocity of the continuous phase (organic phase) associated with the feed throughput of the extraction column was increased to 0.2 cm / s, 0.4 cm / s, 0.6 cm / s, 0.7 cm / s, and 0.8 cm / s, respectively The maximum extraction ratio of acrylic acid was measured in the same manner as in Example 1. The results are shown in Table 2 below.

Organic phase
Linear velocity (cm / s) Operable
Maximum rpm Within the remaining balance
Acrylic acid concentration (wt%) Acrylic acid
Extraction rate (%) Example
One 0.4 120 1.94 99.24 0.5 120 1.29 99.44 0.6 165 0.85 99.66 0.8 160 1.13 99.51 1.0 120 2.40 99.02

Organic phase
Linear velocity (cm / s) Operable
Maximum rpm Within the remaining balance
Acrylic acid concentration (wt%) Acrylic acid
Extraction rate (%) Comparative Example
One 0.2 165 1.31 99.39 0.4 150 1.21 99.46 0.6 135 1.40 99.36 0.7 100 2.75 98.69 0.8 90 3.89 98.12

Referring to Table 2, in Comparative Example 1, when the linear velocity of the organic phase in the extraction column was lowered to 0.4 cm / s, the extraction ratio of acrylic acid reached a maximum of 99.46%. However, in Comparative Example 1, when the linear velocity of the organic phase was increased to 0.8 cm / s, the maximum rpm of the perforated plate was decreased. That is, in the case of Comparative Example 1, as the feed throughput per unit time increased, flooding occurred at a relatively low rpm and the extraction rate of acrylic acid was also decreased.

On the other hand, referring to Table 1, in Example 1, the linear velocity of the organic phase was set to be higher than that of Comparative Example 1 by using an extraction column equipped with a decanter. Particularly, in the case where the linear velocity of the organic phase in Example 1 was 0.8 cm / s, compared with the case in which the linear velocity of the organic phase in Comparative Example 1 was 0.4 cm / s, the feed rate per unit time was twice as high, Stirring was possible, and the extraction ratio of acrylic acid was equal or higher. Further, when the linear velocity of the organic phase was 0.6 cm / s, it was confirmed that Example 1 was able to operate at a maximum of 165 rpm and exhibited a high acrylic acid extraction ratio as high as possible.

Example 2

Except that the Solvent / Feed ratio was adjusted to 1 or 1.3 in the extraction column 200 and the linear velocity of the continuous phase (organic phase) associated with the feed throughput of the extraction column 200 was fixed at 0.5 cm / s, 1, the maximum extraction ratio of acrylic acid was measured. The results are shown in Table 3 below.

Comparative Example 2

The same procedure as in Example 1 was performed except that the solvent / feed ratio in the extraction column was adjusted to 1 or 1.3 and the linear velocity of the continuous phase (organic phase) associated with the feed throughput of the extraction column was fixed at 0.5 cm / s The maximum extraction ratio of acrylic acid was measured. The results are shown in Table 4 below.

Organic phase
Line speed
(cm / s) Solvent /
Feed ratio Operable
Maximum rpm Within the remaining balance
Acrylic acid concentration
(wt%) Acrylic acid
Extraction rate
(%) Example
2 0.5 One 150 1.77 99.28 0.5 1.3 120 1.29 99.44

Organic phase
Line speed
(cm / s) Solvent /
Feed ratio Operable
Maximum rpm Within the remaining balance
Acrylic acid concentration
(wt%) Acrylic acid
Extraction rate
(%) Comparative Example
2 0.5 One 150 3.66 98.35 0.5 1.3 135 1.40 99.36

Referring to Table 4, in Comparative Example 2, when the solvent / feed ratio was lowered under the same linear velocity of the organic phase, the maximum rpm that could be operated rose, but the acrylic acid concentration in the residual liquid increased and the acrylic acid extraction rate dropped by 1% or more .

On the other hand, referring to Table 3, it can be seen that when the solvent / feed ratio is lowered in Example 2, the extraction rate of acrylic acid can be kept almost unchanged while it is possible to operate at an rpm equivalent to that of Comparative Example 2.

In other words, when it is desired to increase the feed capacity of the feed for the purpose of increasing the production amount of acrylic acid, by using an extraction column equipped with a decanter as in the above embodiments and controlling the flow thereof, It has been confirmed that flexibility can be improved. Further, according to the method of the above embodiments, it is possible to reduce the solvent / feed ratio, to reduce the amount of solvent used, and to reduce the energy consumption in the distillation process.

1: (meth) acrylic acid-containing mixed gas
50: Acetic acid absorption tower
100: (meth) acrylic acid absorption tower
115, 130: (meth) acrylic acid aqueous solution transfer line
150, 350: decanter
152: Decanter's water transfer line
153: decanter's organic phase transfer line
200: (meth) acrylic acid extraction column
215: Extract transfer line
235: Additional balance transfer line
300: distillation column
400: High boiling point byproduct separation tower
CAA: Crude (meth) acrylic acid
HPAA: High purity (meth) acrylic acid

Claims

An absorption step of obtaining a (meth) acrylic acid aqueous solution by contacting a mixed gas containing (meth) acrylic acid, an organic by-product and water vapor produced by the synthesis reaction of (meth) acrylic acid with water in a (meth) acrylic acid absorption tower;
A phase separation step of separating the (meth) acrylic acid aqueous solution obtained through the absorption step and the (meth) acrylic acid extract solution obtained through the extraction step described later from the decanter to obtain an organic phase and an aqueous phase;
An extraction step of contacting the aqueous phase obtained by the phase separation step with an extraction solvent in an extraction column to obtain an (meth) acrylic acid extract and an additional residue; And
A distillation step of distilling a feed containing the organic phase obtained through the phase separation step to obtain (meth) acrylic acid
(Meth) acrylic acid.

The method according to claim 1,
An absorption step of obtaining a (meth) acrylic acid aqueous solution by contacting a mixed gas containing (meth) acrylic acid, an organic by-product and water vapor produced by the synthesis reaction of (meth) acrylic acid with water in a (meth) acrylic acid absorption tower;
A phase separation step of separating a part of the (meth) acrylic acid aqueous solution obtained through the above absorption process and the (meth) acrylic acid extract solution obtained through the above extraction step in a decanter to obtain an organic phase and an aqueous phase;
An extraction step of contacting the aqueous phase obtained by the phase separation step with an extraction solvent in an extraction column to obtain an (meth) acrylic acid extract and an additional residue; And
(Meth) acrylic acid obtained by distilling a feed containing the remainder of the aqueous (meth) acrylic acid solution obtained through the absorption process and the organic phase obtained through the phase separation step
(Meth) acrylic acid.

The method according to claim 1,
The organic phase obtained by phase separation in the decanter is a continuous recovery method of (meth) acrylic acid containing at least 40% of (meth) acrylic acid in the (meth) acrylic acid and the (meth) acrylic acid contained in the .

(Meth) acrylic acid, organic by-products, and water vapor produced by the synthesis reaction of (meth) acrylic acid, and a (meth) acrylic acid aqueous solution obtained by contacting the mixed gas with water (Meth) acrylic acid absorption tower (100) equipped with an aqueous solution outlet port;
(Meth) acrylic acid aqueous solution, which is connected through the aqueous solution outlet of the absorption tower 100 and the aqueous solution transfer line 115, through the aqueous (meth) acrylic acid aqueous solution inlet connected to the aqueous solution outlet of the extraction column 200, A decanter 150 having an organic phase outlet through which an organic phase obtained by phase separation of an extracting liquid inlet, an incoming (meth) acrylic acid aqueous solution and an extracting liquid is discharged, and a water outlet for discharging the water phase obtained by the phase separation;
An extract outlet for discharging the (meth) acrylic acid extract solution obtained by contacting the inflow water with the extraction solvent, and an additional outlet for discharging the (meth) acrylic acid extract solution through the water inlet connected to the water outlet of the decanter 150 through the water transfer line 152, (Meth) acrylic acid extraction column 200 equipped with an additional residual liquid outlet; And
(Meth) acrylic acid outlet through which the (meth) acrylic acid obtained by the distillation of the feed containing the introduced organic phase and the organic phase inlet connected to the organic phase outlet of the decanter 150 through the organic phase transfer line 153, (300)
(Meth) acrylic acid.

5. The method of claim 4,
The distillation column 300 includes an aqueous solution inlet connected to the aqueous solution outlet of the absorber 100 through the aqueous solution transfer line 130, an organic phase inlet connected to the organic phase outlet of the decanter 150 through the organic phase transfer line 153, And a (meth) acrylic acid outlet through which (meth) acrylic acid is discharged, which is obtained by distillation of a mixture of the introduced aqueous solution and the organic phase;
(Meth) acrylic acid aqueous solution discharged from the absorption tower 100 is supplied to the decanter 150 and the remainder of the aqueous (meth) acrylic acid solution is supplied to the distillation column 300, Continuous recovery of acrylic acid.