KR101659541B1 - Process for continuous recovering (meth)acrylic acid - Google Patents

Abstract

The present invention relates to a continuous recovery method of (meth) acrylic acid. The continuous recovery method of (meth) acrylic acid according to the present invention makes it possible to remove scum more effectively, thereby enabling operation of a stable continuous process.

Description

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

The present invention relates to a continuous recovery method of (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, and the like are converted into (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 containing 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 contacted with an absorption solvent in a (meth) acrylic acid absorption tower and recovered as an aqueous (meth) acrylic acid solution. Then, the decomposable gas in which the (meth) acrylic acid is deaerated is recycled to the synthesis reaction of (meth) acrylic acid, and some of it is incinerated and converted into harmless gas and discharged. The (meth) acrylic acid aqueous solution is extracted, 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. Alternatively, a method is known in which an aqueous (meth) acrylic acid solution is supplied to an extraction column to obtain an (meth) acrylic acid extract and a residual liquid having a reduced water content, and the extracted liquid is distilled to reduce energy consumption.

On the other hand, the (meth) acrylic acid aqueous solution obtained from the (meth) acrylic acid absorption tower contains various organic byproducts such as maleic acid, terephthalic acid, aldehyde and (meth) acrylic acid polymer in addition to (meth) acrylic acid. And, due to the characteristic of the process for the continuous recovery of (meth) acrylic acid, a scum is formed by the water-insoluble materials in the organic by-products. However, the scum not only contaminates the (meth) acrylic acid recovery apparatus, but also accumulates in the extraction tower in particular, and acts as a factor to lower the recovery efficiency of the (meth) acrylic acid.

The present invention is to provide a continuous recovery method of (meth) acrylic acid which enables a stable continuous process operation by more effectively removing scum generated in the continuous recovery process of (meth) acrylic acid.

According to the present invention, a (meth) acrylic acid aqueous solution is contacted with an extraction solvent in an extraction column to obtain an (meth) acrylic acid extract solution through an upper outlet of the extraction column, An extraction step of obtaining an additional balance; And a distillation step of distilling a feed containing the (meth) acrylic acid extract to obtain (meth) acrylic acid;

The flow rate is adjusted so as to increase the amount of the remaining balance through the lower outlet of the extraction tower,

There is provided a continuous recovery method of (meth) acrylic acid for removing scum contained in the residual balance by filtering the discharged residual balance.

The continuous recovery method of (meth) acrylic acid is a method in which a mixed gas containing (meth) acrylic acid, an organic by-product and water vapor produced by a synthesis reaction of (meth) acrylic acid is contacted with water to obtain an fair; (Meth) acrylic acid aqueous solution obtained through the absorption step is contacted with an extraction solvent in an extraction column to obtain an (meth) acrylic acid extract liquid through an upper outlet of the extraction tower, and the lower outlet An extracting step of obtaining an additional residual liquid through the extraction step; And a distillation step of distilling the (meth) acrylic acid extract obtained through the extraction step to obtain (meth) acrylic acid.

Also, the continuous recovery method of (meth) acrylic acid may include an absorption step of obtaining the (meth) acrylic acid aqueous solution; (Meth) acrylic acid aqueous solution obtained through the absorption process is contacted with an extraction solvent in an extraction column to obtain an (meth) acrylic acid extract solution through an upper outlet of the extraction column, and a lower pressure zone An extracting step of obtaining an additional residue through the lower outlet; And a distillation step of distilling a mixture containing at least a part of the (meth) acrylic acid aqueous solution obtained through the absorption process and the (meth) acrylic acid extract obtained through the extraction step to obtain (meth) acrylic acid .

Also, the continuous recovery method of (meth) acrylic acid is characterized in that the filtrate obtained by filtering the residual balance is phase-separated into an organic phase and an aqueous phase, and the organic phase is separated into the extraction step and the distillation step And supplying the water phase to the absorption process.

The continuous recovery method of (meth) acrylic acid according to the present invention more effectively removes scum generated in the continuous recovery of (meth) acrylic acid, thereby enabling stable continuous operation of the process.

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

Prior to this, unless expressly stated throughout the present specification, several terms are defined with the following meanings.

First, '(meth) acrylic acid' can be used to mean acrylic acid, methacrylic acid or a mixture thereof.

In addition, '(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. That is, according to one embodiment of the present invention, at least one compound selected from the group consisting of propane, propylene, butane, i-butylene, t-butylene and (meth) acrolein (Meth) acrylic acid-containing mixed gas. (Meth) acrylic acid, an unreacted raw material compound, (meth) acrolein, an inert gas, carbon monoxide, carbon dioxide, water vapor, and various organic byproducts (acetic acid, low boiling point byproduct, high boiling point byproduct, etc.) May be included. Herein, the water-soluble suspension formed by the organic by-products is referred to as 'scum'.

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

On the other hand, in liquid-liquid extraction using agitated columns such as Karr type columns and Scheibel type columns, a relatively light phase is supplied to the bottom of the extraction column , A relatively heavy phase is fed to the top of the extraction column. Then, the extraction is proceeded by the contact of the materials supplied to the extraction column, so that a light image and a heavy image of a new composition are obtained. The light phase of the new composition obtained through the extraction process is obtained through the upper outlet of the extraction column and the heavier phase of the new composition is obtained through the lower outlet of the extraction column. Generally, the heavy component of the new composition obtained through the above-mentioned extraction process is maintained at a predetermined level in the lower part of the extraction column before being discharged to the lower outlet of the extraction column, . At this time, the section of the extraction column in which the heavy image is stationary is referred to as a 'lower section' (or a 'fixed section'). For example, in the step of extracting (meth) acrylic acid contained in the aqueous (meth) acrylic acid solution using an extraction solvent, a relatively heavier (meth) acrylic acid aqueous solution is fed to the top of the extraction column, The extraction solvent is fed to the bottom of the extraction column. Then, the extraction proceeds by the contact with these to obtain an extract in which a large amount of (meth) acrylic acid is dissolved and an additional raffinate in which a considerable amount of (meth) acrylic acid is lost. At this time, the extract which is a relatively light phase is obtained through the upper outlet of the extraction column, and the additional residue, which is a relatively heavy phase, is obtained through the lower outlet of the extraction column. Here, the residual balance is maintained at a predetermined level in the lower section of the extraction column before being discharged to the lower outlet of the extraction column, and some of the remaining amount is discharged to the lower outlet of the extraction column. At this time, the section of the extraction column in which the residual balance is fixed is referred to as a 'lower section' (or 'additional section of the residual balance'). The weight balance may include an organic phase and an aqueous phase. Depending on the process conditions, the residual balance may be phase-separated from the organic phase and the water phase in the lower pressure section to form an interface have.

And, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit 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.

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 course of the synthesis of (meth) acrylic acid, various organic by-products are formed together with (meth) acrylic acid, and scum is formed by the water-repellent materials contained in the organic by-products. However, due to the characteristics of the continuous process, the scum may contaminate the interior of various devices, making it impossible to perform stable process operations, and also contributing to lowering the recovery efficiency of the (meth) acrylic acid.

In this connection, the inventors of the present invention have found that, in a continuous recovery method including an absorption process of a (meth) acrylic acid, an extraction process and a distillation process, a scum is removed by filtering a lower discharge And a method of using the water as an absorption water of the absorption process has been proposed.

However, according to the study results of the present inventors, it was confirmed that in the case of the previously proposed method, only a part of the scum contained in the residual balance can be removed, and the scum can be accumulated as the operation time elapses. That is, the scum is accumulated as a layer on the weight balance period (particularly, the interface between the organic phase and the water phase formed in the fixed section) under the extraction tower, and the thickness of the scum accumulated as the operation time is accumulated, And the direction of the water phase. However, the previously proposed method is to use the filtered filtrate as the absorption water of the (meth) acrylic acid absorption process, and only the water phase formed in the lower section of the extraction column is selectively collected and filtered. Accordingly, in the case of the previously proposed method, the scum in the portion of the scum accumulated on the interface can be removed, but the scum in the portion in contact with the organic phase can not be removed and remains. As a result, in the case of the previously proposed method, the scum accumulates as the operation time elapses, and the shutdown of the extraction tower eventually becomes inevitable.

Accordingly, the inventors of the present invention have found that, in the course of repeated studies to overcome such a problem, the inventors of the present invention have found that, in the extraction process, the amount of flow of the residual balance through the lower outlet of the extraction tower is larger than the & It is confirmed that the accumulation of scum can be fundamentally blocked by preventing the interface between the organic phase and the water phase from being formed at the bottom of the extraction tower. In addition, it has been confirmed that the scum contained in the residual liquid can be more effectively removed by filtering the residual liquid discharged to the lower part of the extraction tower, thereby enabling a more stable continuous process operation.

( Mat ) Continuous recovery method of acrylic acid

According to an embodiment of the present invention,

(Meth) acrylic acid aqueous solution is contacted with an extraction solvent in an extraction column to obtain an (meth) acrylic acid extract through an upper outlet of the extraction tower, and an additional residue is obtained through a lower outlet of the extraction column; And a distillation step of distilling a feed containing the (meth) acrylic acid extract to obtain (meth) acrylic acid;

The flow rate is adjusted so as to increase the amount of the remaining balance through the lower outlet of the extraction tower,

There is provided a continuous recovery method of (meth) acrylic acid for removing scum contained in the residual balance by filtering the discharged residual balance.

Basically, the continuous recovery method of (meth) acrylic acid includes an extraction step and a distillation step for an aqueous (meth) acrylic acid solution. Particularly, in the continuous recovery method of (meth) acrylic acid, the flow rate is adjusted so as to increase the discharge amount of the residual balance through the lower outlet of the extraction tower, The accumulation of scum can be fundamentally blocked. Further, in the continuous recovery method of the (meth) acrylic acid, the scum contained in the residual liquid can be more effectively removed by filtering the residual liquid discharged to the lower part of the extraction tower, It is possible.

The continuous recovery method of (meth) acrylic acid according to an embodiment is a method in which a mixed gas containing (meth) acrylic acid, an organic by-product and water vapor produced by the synthesis reaction of (meth) acrylic acid is contacted with water An absorption step of obtaining an aqueous (meth) acrylic acid solution; (Meth) acrylic acid aqueous solution obtained through the absorption process is contacted with an extraction solvent in an extraction tower to obtain an (meth) acrylic acid extract solution through an upper outlet of the extraction tower, and an additional residue An extraction step of obtaining; And a distillation step of distilling the (meth) acrylic acid extract obtained through the extraction step to obtain (meth) acrylic acid.

Further, a continuous recovery method of (meth) acrylic acid according to another embodiment includes an absorption step of obtaining the (meth) acrylic acid aqueous solution as shown in FIG. 2; (Meth) acrylic acid aqueous solution obtained through the absorption process is contacted with an extraction solvent in an extraction column to obtain an (meth) acrylic acid extract solution through an upper outlet of the extraction column, and the An extraction step of obtaining an additional balance; And a distillation step of distilling a mixture containing at least a part of the (meth) acrylic acid aqueous solution obtained through the absorption process and the (meth) acrylic acid extract obtained through the extraction step to obtain (meth) acrylic acid .

According to another embodiment of the present invention, there is provided a method for continuously recovering (meth) acrylic acid, comprising the steps of: separating the filtrate obtained through filtration of the residual residue into an organic phase and an aqueous phase, Process, and the water phase can be used as the water to be absorbed in the absorption process.

Hereinafter, with reference to FIGS. 1 and 2, each process that may be included in the method of the above embodiments will be described.

I. Absorption Process

First, a continuous recovery method of (meth) acrylic acid according to an embodiment includes a step of bringing a (meth) acrylic acid, an organic by-product, and a gas mixture produced by the synthesis reaction of (meth) An absorption process to obtain an aqueous acrylic acid solution may be included.

The absorption process is a step for obtaining an aqueous (meth) acrylic acid solution, which can be obtained according to a conventional method in the technical field of the present invention.

As a non-limiting example, the synthesis reaction of (meth) acrylic acid may be carried out by oxidation reaction of at least one compound selected from the group consisting of propane, propylene, butane, isobutylene, t-butylene and (meth) . ≪ / RTI >

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, and preferably the catalysts disclosed in Korea Patent No. 0349602 and No. 037818 can be used.

The (meth) acrylic acid-containing mixed gas produced by the gas-phase oxidation reaction may contain an unreacted starting compound, an intermediate (meth) acrolein, other inert gases, carbon dioxide, water vapor, and various organic by- , Low boiling point byproducts, high boiling point byproducts, etc.).

According to one embodiment, the (meth) acrylic acid-containing mixed gas (1) may be obtained in the form of a (meth) acrylic acid aqueous solution by being supplied to the (meth) acrylic acid absorption tower (100) and coming into contact with water as an absorption solvent.

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 absorption tower 100 may be a packed tower or a multistage tray tower. Here, the filling column may have a filler such as a rashing ring, a pall ring, a saddle, a gauze, and a structured packing.

Meanwhile, the mixed gas 1 may be supplied to the lower part of the absorption tower 100 in consideration of the absorption efficiency, and the absorption solvent may be supplied to the upper part of the absorption tower 100.

The absorbing solvent may be water such as tap water, deionized water, or the like, and may include a circulating process water introduced from another process. Accordingly, the absorbing solvent may contain trace amounts of organic by-products (e.g., acetic acid) introduced from other processes. According to one embodiment, the absorption solvent supplied to the absorber 100 may contain 3 to 15% by weight of organic byproducts. That is, in consideration of the absorption efficiency of (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.

The (meth) acrylic acid absorption tower 100 can be operated at an internal pressure of 1 to 1.5 bar or 1 to 1.3 bar in consideration of the condensation condition of (meth) acrylic acid and the moisture content condition depending on the saturated water vapor pressure, The internal temperature may be adjusted to 50 to 100 占 폚, or 50 to 80 占 폚.

On the other hand, through the absorption process, the (meth) acrylic acid aqueous solution is discharged to the lower part of the (meth) acrylic acid absorption tower 100, and the non-condensable gas deaerated by the (meth) acrylic acid is discharged to the upper part. In this case, the (meth) acrylic acid aqueous solution preferably contains (meth) acrylic acid in a concentration of 40% or more, or 40 to 90% by weight, or 50 to 90% It is advantageous.

The obtained (meth) acrylic acid aqueous solution can be supplied to the (meth) acrylic acid extraction tower 200 through the aqueous solution transfer line 102 as shown in FIG. 2, the (meth) acrylic acid aqueous solution may be divided into (meth) acrylic acid extraction tower 200 and distillation column 300 through aqueous solution transfer lines 102 and 103.

1, when the extraction step is introduced between the (meth) acrylic acid absorption step and the distillation step, most of the absorption solvent contained in the (meth) acrylic acid aqueous solution can be removed with a small energy in the extraction step, The processing load can be reduced. The extraction process will be described in detail with a separate table of contents.

On the other hand, when the extraction step is introduced between the (meth) acrylic acid absorption step and the distillation step and the aqueous (meth) acrylic acid solution is divided into the extraction step and the distillation step as shown in FIG. 2, The distillation process can be operated under more relaxed operating conditions and the overall energy efficiency can be improved. Acrylic acid extraction column 200 and the distillation column 300 may be divided into a (meth) acrylic acid extraction column 200 and a distillation column (not shown) 300, capacity, processing capability, energy efficiency increase effect of the entire process, and the like. According to one embodiment, 5 to 70 wt%, or 10 to 60 wt%, or 10 to 50 wt% of the (meth) acrylic acid aqueous solution is supplied to the (meth) acrylic acid extraction tower 200, It may be advantageous in terms of the expression of the above-mentioned effect to be supplied to the column 300.

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, a process of contacting the non-condensable gas with an absorption solvent and recovering the acetic acid contained in the non-condensable gas may be performed.

The step of contacting the non-condensable gas with the absorbing solvent may be performed in the acetic acid absorption tower 150. At this time, for effective acetic acid absorption, the acetic acid absorption tower 150 can be operated at a pressure of 1 to 1.5 bar, preferably 1 to 1.3 bar, and an internal temperature of 50 to 100 ° C, preferably 50 to 80 ° C Respectively. In addition, specific operating conditions of the acetic acid absorption tower 150 may be found in Korean Patent Publication No. 2009-0041355.

At this time, an absorption solvent (process water) for absorbing acetic acid is supplied to the upper part of the acetic acid absorption tower 150, and an aqueous solution containing acetic acid is discharged to the lower part of the acetic acid absorption tower 150. 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.

II . Extraction process

(Meth) acrylic acid aqueous solution is contacted with an extraction solvent in an extraction tower to obtain an (meth) acrylic acid extract solution through an upper outlet of the extraction tower, and the And an extraction process for obtaining an additional residue through the lower outlet of the extraction column.

According to one embodiment, the (meth) acrylic acid aqueous solution may be prepared through the above-described absorption process.

The extraction step may be performed under the (meth) acrylic acid absorption tower 200. Basically, in the extraction column 200, the (meth) acrylic acid aqueous solution is contacted with the extraction solvent to remove an amount of extract of (meth) acrylic acid dissolved and a residual amount of raffinate Respectively. Here, the extracted liquid is obtained through the upper outlet of the extraction tower 200, and the additional liquid is obtained through the lower outlet of the extraction tower 200.

Thus, in the extraction column 200, most of the water contained in the aqueous solution can be removed through a method of contacting (meth) acrylic acid aqueous solution with an extraction solvent (that is, a method of using less energy than distillation). Accordingly, the burden on the distillation process in the distillation column 300 as a subsequent process can be reduced, and the energy efficiency of the entire process can be improved. Further, the polymerization reaction of (meth) acrylic acid which may occur in the distillation process can be minimized, and thus, improved operation stability can be secured.

On the other hand, in the case of a general extraction process, a certain amount of residual solution is kept in the lower part of the extraction tower and phase-separated into an organic phase and an aqueous phase. The amount of the residual balance remaining in the bottom of the extraction tower and the amount of the residual organic residue remaining in the bottom of the extraction tower are maintained substantially equal to each other, The interface is maintained at a constant level. Scum is accumulated at the interface between the organic phase and the water phase due to the residual balance remaining at the bottom of the extraction tower. That is, the scum is accumulated on the interface between the organic phase and the water phase formed in the weight portion of the bottom of the extraction tower, and the thickness of the accumulated scum is increased from the interface to the direction of the organic phase and the water phase . However, since the scum not only pollutes various devices but also accumulates in the extraction tower and acts as a factor for lowering the recovery efficiency of (meth) acrylic acid, it is preferably removed for stable process operation.

With respect to the removal of the scum, a method of filtering the weight residue discharged to the lower part of the extraction tower 200, previously proposed by the present inventors, to remove the scum and use the filtrate as the absorption water in the absorption process The scum in the portion of the scum accumulated at the interface between the organic phase and the water phase can be removed but the scum in the portion in contact with the organic phase can not be removed and remains. As a result, in the case of the previously proposed method, the scum accumulates as the operation time elapses, and the shutdown of the extraction tower eventually becomes inevitable.

On the contrary, in the continuous recovery method of (meth) acrylic acid according to an embodiment of the present invention, in the extraction step, the interface between the organic phase and the water phase is not formed in the remaining weight portion of the lower part of the extraction tower 200, The accumulation of scum in the extraction tower 200 can be fundamentally blocked. That is, in the continuous recovery method of (meth) acrylic acid according to one embodiment, the flow rate is adjusted so that the discharge amount of the remaining balance through the lower outlet of the extraction tower 200 is larger than the generation amount of the additional residue by the extraction, So that the interface between the organic phase and the water phase is not formed inside the extraction tower 200.

In addition, the continuous recovery method of (meth) acrylic acid according to an embodiment of the present invention is a method of efficiently removing scum contained in the residual liquid by filtering the residual residual liquid discharged to the lower part of the extraction tower 200 This allows for a more stable continuous process operation.

According to one embodiment, the amount of the residual residue and the amount of the residual residue in the extraction process can be adjusted within a range such that the interface between the organic phase and the water phase is not formed in the residual balance period of the lower part of the extraction tower 200. That is, the organic phase due to the phase separation of the residual balance is formed relatively above the water phase in the weight residual value interval under the extraction tower 200. Therefore, it is preferable to adjust the lower discharge flow rate of the extraction tower 200 to such an extent that all of the water phase can be discharged in the estimated remaining balance period, or that the organic phase is partly discharged together with the water phase.

In addition, the amount of the extraction solvent contained in the residual weight discharged to the lower part of the extraction tower 200 is further introduced into the extraction tower 200, so that extraction (extraction) with respect to the aqueous (meth) acrylic acid solution The weight ratio of the solvent can be maintained at a certain level, and stable extraction efficiency can be maintained.

According to one embodiment, the filtering of the residual balance can be performed using a filter to such an extent that the scum obtained through the lower outlet of the extraction tower 200 can be sufficiently removed, Is not particularly limited. However, according to one embodiment, the filtering of the residual balance can be performed using a filter having pores with an average diameter of 50 mu m or less, or 0.1 to 30 mu m, or 0.5 to 20 mu m, or 0.5 to 10 mu m. That is, in order to sufficiently remove the scum, it is advantageous that the filter used for the filtering has pores having an average diameter of 50 μm or less. However, in consideration of the filtering efficiency and the process flow, it is advantageous that the filter has pores having an average diameter of 0.1 탆 or more.

The weight balance discharged to the lower part of the extraction tower 200 is mostly water but includes some organic phases. Therefore, the filter used for the filtering is preferably a material having resistance to extraction solvent and (meth) acrylic acid, , And non-limiting examples may be metal materials such as cotton, stainless steel (SUS) and the like.

In addition, the filtering system 250 used for filtering the residual balance may include at least one filter satisfying the above condition, and two or more filters having pores having different average diameters may be connected in series .

On the other hand, since the filtrate obtained through the filtering of the residual balance contains the organic phase and the water phase in a mixed state, the filtrate may be unsuitable for supplying water to the absorption water of the absorption process or for treating wastewater.

Therefore, according to one embodiment, the filtrate obtained through filtering the residual balance is separated into an organic phase and an aqueous phase in a separate phase separation tank, and then the organic phase is supplied to the extraction process and the distillation process, . The water phase obtained through the phase separation of the filtrate may be supplied to the absorption process and used as the absorption water. According to one embodiment, the filtrate obtained through filtration of the residual balance is supplied to the phase separation tank 350 of the distillation process, which will be described later, through the filtrate transfer line 235, Can be phase-separated.

On the other hand, the extraction solvent supplied to the extraction tower 200 may preferably have solubility and hydrophobicity with (meth) acrylic acid. In view of the kind of the solvent required in the subsequent distillation step and the physical properties thereof, it is preferable that the extraction solvent has a boiling point lower than that of the (meth) acrylic acid. For example, the extraction solvent may be advantageous in process operation because it is a hydrophobic solvent having a boiling point of 120 ° C or less, or 10 to 120 ° C, or 50 to 120 ° C.

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. For on the day can.

According to one embodiment, the weight ratio of the extraction solvent to the (meth) acrylic acid aqueous solution supplied to the extraction tower 200 is 1: 1 to 1: 2, or 1: 1.0 to 1: 1.8, 1: 1.5, or 1: 1.1 to 1: 1.3. That is, in order to secure sufficient extraction efficiency, it is advantageous that the weight ratio of the extraction solvent to the (meth) acrylic acid aqueous solution supplied to the extraction tower 200 is maintained at 1: 1 or more. If the weight ratio is more than 1: 2, the extraction efficiency may be improved. However, the loss of (meth) acrylic acid may be increased in the subsequent distillation column 300, and the reflux of the solvent Which is undesirable.

According to one embodiment, the temperature of the (meth) acrylic acid aqueous solution in the extraction step is advantageously in the range of 10 to 70 ° C in terms of improvement in extraction efficiency.

As the extraction tower 200, a conventional extraction tower 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 column tower, a packed extraction tower, a pulsed packed column, and the like.

Through the extraction process, the extract liquid is discharged to the upper part of the extraction tower 200, and the extracted liquid is supplied to the distillation column 300 through the transfer line 203. In addition, an additional residual liquid is discharged to the lower portion of the extraction tower 200.

At this time, the extract may contain an extraction solvent, water, and organic by-products in addition to the target compound (meth) acrylic acid. According to one embodiment, in a steady state where stable operation is performed, the extract contains 30-40 wt% of (meth) acrylic acid, 55-65 wt% of extraction solvent, 1-5 wt% of water, and residual organic byproducts . That is, most of the water (for example, 85 wt% or more) contained in the (meth) acrylic acid aqueous solution through the extraction step can be recovered as a residual liquid. As most of the water is recovered in the extraction tower 200, it is possible to reduce the distillation burden of the distillation column 300, thereby lowering the energy consumption and alleviating distillation conditions, thereby minimizing the polymerization reaction of (meth) acrylic acid It is possible to secure driving stability.

In addition, the residual balance obtained from the extraction tower 200 may contain some (meth) acrylic acid which has not been extracted. As a non-limiting example, the balance may contain (meth) acrylic acid in a concentration of 5 wt% or less, or 0.5 to 5 wt%, or 1 to 3 wt%. That is, according to the method of one embodiment, the concentration of (meth) acrylic acid contained in the residual liquid is as low as 5% by weight or less, and the loss of (meth) acrylic acid in the absorption column 100 and the extraction column 200 Can be minimized.

III . Distillation process

On the other hand, the continuous recovery method of (meth) acrylic acid according to an embodiment includes a distillation step of distilling a feed containing the (meth) acrylic acid extract to obtain (meth) acrylic acid.

According to one embodiment, the feed may be a (meth) acrylic acid extract. In this case, the feed may be fed to the distillation column 300 through the (meth) acrylic acid extract liquid transfer line 203, as shown in FIG.

Further, according to another embodiment, the feed may be a mixture of the (meth) acrylic acid aqueous solution and the (meth) acrylic acid extract. In this case, the feed may be fed to the distillation column 300 via the (meth) acrylic acid aqueous solution transfer line 103 and the (meth) acrylic acid extract liquid transfer line 203, as shown in FIG.

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.

Here, the solvent to be applied to the azeotropic distillation method may be an azeotropic ratio with water and acetic acid, and may be a hydrophobic solvent which does not coexist with (meth) acrylic acid. The hydrophobic azeotropic solvent may have 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 particular, when the extraction process is introduced as shown in FIGS. 1 and 2, it is preferable that the hydrophobic azeotropic solvent is the same as the extraction solvent in the extraction process, considering the production efficiency in accordance with the continuous process. When the same type of solvent is used in the extraction process and the distillation process, at least a part 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 tower 200 And can be reused as an extraction solvent.

Through such a distillation process, the components other than (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 recovered to the lower portion of the distillation column 300.

At this time, the upper effluent of the distillation column 300 may be supplied to the phase separation tank 350 and reused after a predetermined treatment. A relatively light liquid (for example, an organic phase) is supplied to the upper portion of the phase separating tank 350, and a relatively heavy liquid (for example, an organic phase) (For example, a water phase) may be recovered to the lower portion of the phase separation tank 350.

As an example, the upper effluent of the distillation column 300 may be separated into an organic phase containing an azeotropic solvent and an aqueous phase containing water in the phase separation tank 350. The filtrate obtained through filtration of the residual balance of the extraction step may be supplied to the phase separation tank 350 through the filtrate transfer line 253 and subjected to phase separation treatment together with the upper discharge liquid of the distillation column 300. Here, the separated organic phase may be supplied to the upper end of the distillation column 300 and used as an azeotropic solvent. If necessary, at least a part of the organic phase may be supplied to the (meth) acrylic acid extraction tower 200 and used as an extraction solvent. At least a part of the water phase separated in the phase separation tank 350 may be supplied to the (meth) acrylic acid absorption tower 100 and used as the absorption water, and a part thereof may be treated as wastewater.

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 contained in the aqueous phase may be 1 to 50 wt%, preferably 2 to 40 wt%, more preferably 3 to 30 wt%.

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

On the other hand, 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 crude (meth) acrylic acid (CAA) recovered 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.

In the method for recovering (meth) acrylic acid according to this embodiment, each of the above-described steps can be carried out organically and continuously. In addition to the steps described above, processes that can be performed conventionally before or after each step may be further included and performed.

( Mat ) Continuous recovery of acrylic acid

Meanwhile, according to another embodiment of the present invention, as shown in FIG. 1,

(Meth) acrylic acid absorption tower (100) for obtaining a (meth) acrylic acid aqueous solution by contacting water with a mixed gas containing (meth) acrylic acid, an organic by-product, and water vapor produced by a synthesis reaction of (meth) acrylic acid;

A (meth) acrylic acid extraction tower 200 for obtaining an extract solution containing (meth) acrylic acid by bringing the (meth) acrylic acid aqueous solution obtained from the absorption tower 100 into contact with an extraction solvent and a balance residue;

A filtering system 250 for filtering the residual balance discharged to the lower part of the extraction tower 200 to remove scum contained in the residual balance and supplying the filtrate to the phase separation tank 350; And

A distillation column 300 for distilling the (meth) acrylic acid extract obtained from the extraction tower 200 to obtain (meth) acrylic acid,

There is provided a continuous recovery apparatus for (meth) acrylic acid which is operated in accordance with the above-mentioned continuous recovery method of (meth) acrylic acid.

In this embodiment, the absorption tower 100 and the extraction column 200 are connected by a (meth) acrylic acid aqueous solution transfer line 102, and the extraction column 200 and the distillation column 300 (Meth) acrylic acid extract liquid transfer line 203. The filtration system 250 and the phase separator 350 are connected by a filtrate transfer line 253. At least a part of the organic phase separated in the phase separation tank 350 may be supplied to the distillation column 300 and the rest may be operated to be supplied to the extraction tower 200. Also, at least a portion of the water phase separated from the phase separation vessel 350 may be operated to be supplied to the absorption tower 100.

According to another embodiment of the present invention, as shown in FIG. 2, the (meth) acrylic acid absorption tower 100; A (meth) acrylic acid extraction tower 200 for obtaining an extract solution containing (meth) acrylic acid by contacting at least a part of the (meth) acrylic acid aqueous solution obtained from the absorption tower 100 with an extraction solvent; The filtering system (250); And a distillation column (distillation column) for obtaining (meth) acrylic acid by distilling a mixture containing at least a part of the (meth) acrylic acid aqueous solution obtained from the absorption tower 100 and the (meth) acrylic acid extract solution obtained from the extraction tower 200 (Meth) acrylic acid, which is operated in accordance with the above-mentioned continuous recovery method of (meth) acrylic acid.

In this embodiment, the absorber 100, the extractor column 200, and the absorber 100 and the distillation column 300 are separated by (meth) acrylic acid aqueous solution transfer lines 102 and 103, respectively And the extraction column 200 and the distillation column 300 are connected by a (meth) acrylic acid extract liquid transfer line 203. The filtration system 250 and the phase separator 350 are connected by a filtrate transfer line 253. At least a part of the organic phase separated in the phase separation tank 350 may be supplied to the distillation column 300 and the rest may be operated to be supplied to the extraction tower 200. Also, at least a portion of the water phase separated from the phase separation vessel 350 may be operated to be supplied to the absorption tower 100.

The filtration system 250 may have an average diameter of 50 mu m or less, or 0.1 to 30 mu m, or 0.5 to 20 mu m, or more preferably 20 mu m or less, in order to sufficiently remove the scum obtained through the lower outlet of the extraction tower 200. [ Or a filter having pores of 0.5 to 10 mu m is preferably provided. The filter provided in the filtering system 250 is preferably an extraction solvent and a material having resistance to (meth) acrylic acid. Non-limiting examples of the filter include a metal such as cotton, SUS (steel use stainless) It may be a material.

On the other hand, the (meth) acrylic acid absorption tower 100 may be a packed tower or a multistage tray tower for improving the contact efficiency between the (meth) acrylic acid-containing mixed gas 1 and water as an absorption 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 tower 200, a conventional extraction tower 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 tower, a packed extraction tower, a pulsed packed column, and the like.

In addition, the acetic acid absorption tower 150, the (meth) acrylic acid aqueous solution transfer line 102, the extract liquid transfer line 203, the phase separation tank 350, the high boiling point byproduct separation tower 400, And may have a conventional configuration in the field.

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.

Comparative Example

A Karr type extraction column having a total height of 52 meters and a total height of about 3 m was prepared. In the extraction column, the inner diameter of the column corresponding to the first to sixth stages (that is, the six stages at the upper end including the uppermost stage) is about 45 mm, and the inner diameter of the column corresponding to the remaining stages 7 to 50 is about 22 mm Respectively.

Among the porous plates placed on each end of the extraction column and performing repetitive upward and downward movement, the aperture ratio of the porous plate placed in the first to sixth stages is about 50%, and the porosity of the porous plates placed in the remaining seventh to The aperture ratio was adjusted to about 28.3%.

Acrylic acid aqueous solution (acrylic acid concentration: about 65.5% by weight, acetic acid concentration: about 2.25% by weight) was fed to the feed inlet of the extraction column, and toluene was supplied to the extraction solvent inlet of the extraction column. At this time, the weight ratio of the acrylic acid aqueous solution and toluene supplied to the extraction column was fixed to be about 1: 1.3.

A lower filter system having a cartridge type filter having pores having an average diameter of about 10 mu m is installed at the lower end of the extraction column from which the residual balance is discharged and is included in an additional balance discharged to the lower portion of the extraction column The scum was removed.

At this time, the amount of the acrylic acid aqueous solution was adjusted to 91.3 g / min, and the toluene amount was controlled to 115.8 g / min. In order to maintain a constant level of the interface between the organic phase and the water phase formed by the residual solution remaining at the lower part of the extraction column, the discharge flow rate of the residual solution was maintained at about 25.0 g / min, and the discharge flow rate of the extract solution was about 182.1 g / min.

The acrylic acid concentration in the residual balance was analyzed under the condition of the maximum mechanical reciprocating speed (rpm; that is, the maximum rpm immediately before the flooding phenomenon) of the porous plate so that the maximum extraction rate of acrylic acid in the extraction column could be realized.

As a result, in the initial stage of operation, the concentration of acrylic acid in the residual liquid was about 1.45 wt% and the concentration of toluene was 720 ppm. The flow rate of acrylic acid to the residual solution was calculated to be about 0.361 g / min.

However, scum accumulates at the interface between the organic phase and the water phase due to the phase separation of the residual balance at the bottom of the residual column under the extraction column, and the concentration of acrylic acid in the residual liquid is about 4.16% by weight and the concentration of toluene is about 6.58% by weight Respectively. This is because the amount of scum accumulated at the interface between the organic phase and the water phase increases (the thickness of the scum layer becomes thicker), and the organic phase and the water phase are simultaneously discharged into the lower portion of the extraction column in the state of being mixed in emulsion form.

Such an additional residual liquid not only has a high acrylic acid concentration but also can not be supplied as the absorption water of the acrylic acid absorption process due to a high toluene concentration even if the scum is removed through the lower filter system.

As the operation of the extraction column continued, the scum continued to accumulate on the organic phase side (i.e., the internal direction of the extraction column) at the interface between the organic phase and the water phase in the lower stationary section of the extraction column. The accumulation of scum caused contamination of the extraction column, and the extraction efficiency was gradually decreased. As a result, the operation of the extraction column was stopped.

Example

The amount of acrylic acid aqueous solution was adjusted to 91.2 g / min, the toluene amount was adjusted to 123.6 g / min, and the flow rate of the residual solution was adjusted to about 30.6 g / min, the extraction process was carried out in the same manner as in the comparative example. At this time, the discharge flow rate of the extract was 184.3 g / min.

The residual residue obtained through the lower outlet of the extraction column was removed from the scum via the lower filter system and the filtrate was supplied to the phase separation column and separated into organic phase and water phase. At this time, about 1.34 wt% of acrylic acid and about 750 ppm of toluene were contained in the aqueous phase separated from the filtrate. The organic phase separated from the filtrate contained about 0.1% by weight of acrylic acid. The total acrylic acid flow rate in the filtrate was calculated to be about 0.359 g / min.

These results indicate that the extraction efficiency of the extraction column according to the comparative example can be maintained at a level equivalent to the initial extraction efficiency. As a result, the concentration of acrylic acid contained in the residual solution did not increase even after the operation for 7 days or more, and the scum Stable operation without accumulation was possible. Further, when the differential pressure of the lower filter system reaches the limit pressure, the filter is replaced or washed and reused, thereby enabling more stable long-term operation of the extraction column.

1: (meth) acrylic acid-containing mixed gas 100: (meth) acrylic acid absorption tower
102: (meth) acrylic acid aqueous solution transfer line 150: Acetic acid absorption tower
200: (meth) acrylic acid extraction column 203: Extract transfer line
250: Filtration system 253: Filtrate transfer line
300: distillation column 350: phase separation column
400: High boiling point byproduct separation tower CAA: crude (meth) acrylic acid
HPAA: High purity (meth) acrylic acid

Claims (4)

(Meth) acrylic acid aqueous solution is brought into contact with an extraction solvent in an extraction tower to obtain an (meth) acrylic acid extract solution through an upper outlet of the extraction tower, and an additional residue is obtained through a lower outlet of the extraction column Extraction process; And a distillation step of distilling a feed containing the (meth) acrylic acid extract to obtain (meth) acrylic acid;
The amount of the additional residual liquid discharged through the lower outlet of the extraction tower is controlled so as to be larger than the amount of the additional residual liquid generated by the extraction,
And removing scum contained in the residual balance by filtering the discharged residual balance.
The method according to claim 1,
The (meth) acrylic acid aqueous solution
(Meth) acrylic acid, an organic by-product and water vapor produced by the synthesis reaction of (meth) acrylic acid with water.
(Meth) acrylic acid.
The method according to claim 1,
The (meth) acrylic acid aqueous solution
(Meth) acrylic acid, an organic by-product and water vapor produced by a synthesis reaction of (meth) acrylic acid with water, wherein the water-soluble polymer is at least a part of an aqueous solution obtained by an absorption process,
The feed of the distillation process
(Meth) acrylic acid extract solution, and another part of the obtained aqueous solution obtained by said absorption step in addition to said (meth) acrylic acid extract solution.
(Meth) acrylic acid.
The method according to claim 2 or 3,
The filtrate obtained through the filtering of the residual balance is phase-separated into an organic phase and an aqueous phase,
Wherein the organic phase is supplied to the extraction step and the distillation step, and the water phase is fed to the absorption step.

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