KR20180001547A - Process for recovering (meth)acrylic acid and apparatus for the process - Google Patents

Abstract

The present invention relates to a method and an apparatus for recovering (meth)acrylic acid. The above-mentioned recovering method can omit a step of separating a high boiling point byproduct and save energy to be applied to the (meth)acrylic acid recovery process, and can minimize the possibility that (meth)acrylic acid is polymerized in the (meth)acrylic acid recovery process. Therefore, the above-mentioned recovery method can recover (meth)acrylic acid at a high yield using a small amount of energy.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for recovering (meth)

The present invention relates to a method and an apparatus for efficiently recovering (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 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 recovered as an (meth) acrylic acid aqueous solution by contacting with an absorption solvent containing water in a (meth) acrylic acid absorption tower. 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.

On the other hand, various methods for improving the recovery efficiency of (meth) acrylic acid by adjusting process conditions or process order have been proposed. Typically, a method for separating water and acetic acid from a (meth) acrylic acid aqueous solution obtained from a (meth) acrylic acid absorption tower is known as a method of azeotropic distillation using a hydrophobic solvent in a distillation column.

Specifically, the azeotropic distillation method recovers water and acetic acid to the top of the distillation column, and recovers (meth) acrylic acid to the bottom of the distillation column. However, since the (meth) acrylic acid recovered from the lower portion of the distillation column is recovered in a mixed state with the high boiling point by-product, etc., the lower effluent of the distillation column must be distilled again to remove the high boiling point byproduct. The high boiling point byproduct separation process for removing the high boiling point byproduct from the bottom discharge liquid requires not only a large amount of energy but also causes the problem that (meth) acrylic acid is polymerized by exposure to high temperature in the above process.

The present invention provides a method and apparatus for recovering (meth) acrylic acid in high yield using less energy.

The present invention relates to a process for the production of a distillation column comprising distilling a feed comprising 10 to 90% by weight of (meth) acrylic acid, 10 to 90% by weight of solvent and the balance of impurities, (Meth) acrylic acid comprising a solvent of the (meth) acrylic acid and a distillation step of obtaining crude (meth) acrylic acid containing not more than 3% by weight of a dimer of (meth) acrylic acid.

As an example, the recovery method may further include an absorption step of obtaining a (meth) acrylic acid solution by bringing the (meth) acrylic acid-containing mixed gas into contact with an absorption solvent. The recovery method may further include an extraction step of contacting the (meth) acrylic acid solution with an extraction solvent to obtain an (meth) acrylic acid extract and an additional residue.

The crude (meth) acrylic acid can be discharged from the upper 50% to 100% of the entire stages of the distillation column.

At the side of the distillation column, crude (meth) acrylic acid in liquid or gaseous phase can be obtained. Further, at the side of the distillation column, (meth) acrylic acid corresponding to 30 to 90% by weight of the total (meth) acrylic acid contained in the feed can be recovered.

The recovery process may further include a high boiling point byproduct separation process to distill the bottom effluent obtained at the bottom of the distillation column to obtain crude (meth) acrylic acid at the top of the high boiling point byproduct separation column. Further, the recovery method may further include a crystallization step of recrystallizing the crude (meth) acrylic acid obtained in the above.

On the other hand, the present invention provides a (meth) acrylic acid recovery apparatus comprising a distillation column and a crystallizer. Specifically, the recovery device includes a distillation tower having a feed inlet and an upper, side and lower outlet; (Meth) acrylic acid inlet connected to the side outlet of the distillation tower through a crude (meth) acrylic acid transfer line and a (meth) acrylic acid outlet for discharging (meth) acrylic acid obtained by recrystallizing the introduced crude (meth) acrylic acid Lt; RTI ID = 0.0 > crystallizer. ≪ / RTI >

(Meth) acrylic acid absorption tower having a mixed gas inlet through which a (meth) acrylic acid-containing mixed gas is supplied and an aqueous solution outlet through which the (meth) acrylic acid solution obtained by contacting the mixed gas with an absorbing solvent is discharged, May be further included. In addition, the recovery device is provided with an aqueous solution inlet connected through an aqueous solution outlet of the absorption tower and an aqueous solution transfer line, an extract outlet for discharging the (meth) acrylic acid extract obtained by contact between the introduced (meth) acrylic acid solution and the extraction solvent, And a (meth) acrylic acid extraction tower equipped with an outlet for an additional residual liquid discharged after the balance is settled.

The (meth) acrylic acid recovery method according to one embodiment can omit the step of separating the high boiling point byproduct and save the energy to be applied to the (meth) acrylic acid recovery process. In the (meth) acrylic acid recovery process, It is possible to minimize the possibility of polymerization. Therefore, the above-mentioned recovery method can recover (meth) acrylic acid in a high yield using a small amount of energy.

1 is a view schematically showing a conventional (meth) acrylic acid recovery device.
2 is a view schematically showing a (meth) acrylic acid recovery apparatus according to an embodiment.

Hereinafter, a method for recovering (meth) acrylic acid and a recovery device according to a specific embodiment of the present invention will be described.

According to one embodiment of the invention, a feed comprising 10 to 90% by weight of (meth) acrylic acid, 10 to 90% by weight of solvent and the balance of impurities is distilled off, (Meth) acrylic acid comprising a distillation step of obtaining crude (meth) acrylic acid containing not more than 5% by weight of a solvent and not more than 3% by weight of a dimer of (meth) acrylic acid.

1, a (meth) acrylic acid solution is supplied to a distillation column 300, a (meth) acrylic acid solution supplied to a distillation column 300 is distilled, and water And acetic acid were recovered and a discharged liquid (stream 1 in FIG. 1) containing (meth) acrylic acid was recovered from the bottom of the distillation column 300. 1) is supplied to the high boiling point byproduct separation tower 400, and the high boiling point byproduct contained in the lower boiling point liquid is separated from the high boiling point byproduct separation tower 400, (Meth) acrylic acid could be recovered from the top of the reactor 400. The crude (meth) acrylic acid (stream 2 in FIG. 1) obtained at the upper part of the high boiling point byproduct separation column 400 was recrystallized in a crystallizer 500 to obtain pure (meth) acrylic acid stream. However, this conventional recovery method must include a step of separating the high-boiling by-product from the (meth) acrylic acid mixture, and thus requires a large amount of energy. During the process of separating the high boiling point byproduct, There is a problem that the yield of (meth) acrylic acid is lowered due to an increase in the amount of Michael adducts such as sieves, trimers and oligomers.

In order to solve such a problem, in one embodiment of the present invention, a distillation step for removing a solvent from a (meth) acrylic acid mixture dissolved in a solvent such as an absorption solvent or an extraction solvent is carried out at the side of the distillation tower 300 A distillation step to obtain crude (meth) acrylic acid was employed. By employing such a process, it is possible to omit the high-boiling point by-product separation process that was conventionally required after the distillation process, thereby increasing the yield of (meth) acrylic acid and saving a great deal of energy. In addition, even if a high boiling point byproduct separation process is used, the amount of the sample to be fed into the high boiling point byproduct separation process and the size of the high boiling point byproduct separation tower can be reduced, have.

The recovery process includes a distillation process for distilling the feed comprising (meth) acrylic acid and a solvent to obtain crude (meth) acrylic acid on the side of the distillation column. In the present specification, the term (meth) acrylic acid is used to mean acrylic acid, methacrylic acid, or a mixture thereof.

As the feed, a (meth) acrylic acid solution obtained by various methods known in the technical field of the present invention can be used.

For example, as the feed, a (meth) acrylic acid solution obtained by bringing a (meth) acrylic acid-containing mixed gas produced by the synthesis reaction of (meth) acrylic acid into contact with an absorption solvent may be used. Therefore, the recovery method may further include an absorption step of contacting the (meth) acrylic acid-containing mixed gas with an absorption solvent to obtain a feed.

The above-mentioned (meth) acrylic acid-containing mixed gas can be obtained by subjecting at least one compound (raw material compound) selected from the group consisting of propane, propylene, butane, isobutylene and (meth) acrolein to a gas phase oxidation reaction in the presence of a catalyst Can be obtained. These (meth) acrylic acid-containing mixed gases include (meth) acrylic acid, unreacted raw material compounds, (meth) acrolein, inert gas, carbon monoxide, carbon dioxide, water vapor and various organic byproducts (acetic acid, low boiling point byproduct, . 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 (meth) acrylic acid-containing mixed gas may be combined with an absorption solvent to provide a (meth) acrylic acid solution. As a non-limiting example, the (meth) acrylic acid solution may be obtained by supplying a (meth) acrylic acid-containing mixed gas to a (meth) acrylic acid absorption tower and bringing it into contact with an absorption solvent.

As the (meth) acrylic acid absorption tower, a packed tower or a multistage tray tower can be used for improving the contact efficiency between the (meth) acrylic acid-containing mixed gas and the absorption solvent. The filling column may be filled with a filler such as a rashing ring, a pall ring, a saddle, a gauze, or a structured packing.

The (meth) acrylic acid-containing mixed gas is supplied to the lower portion of the absorption tower, and the absorption solvent is supplied to the upper portion of the absorption tower to increase the absorption efficiency of the mixed gas. The absorbing solvent may include water such as tap water, distilled water or deionized water. In addition, the absorption solvent may include a circulating process water introduced from another process (for example, an aquarium recirculated from the top of the distillation column). Accordingly, the absorption solvent may contain a small amount of organic by-products introduced from other processes, such as acetic acid. However, considering the absorption efficiency of (meth) acrylic acid, the organic by-product content of the absorption solvent supplied to the absorption tower may be adjusted to 15 wt% or less.

The (meth) acrylic acid absorption tower has an internal pressure of 1 to 1.5 bar or 1 to 1.3 bar and an internal pressure of 50 to 100 ° C or 50 to 80 ° C, in consideration of condensation conditions of (meth) acrylic acid and water content in accordance with saturated water vapor pressure, Lt; / RTI > As a result, the (meth) acrylic acid solution is discharged to the lower part of the (meth) acrylic acid absorption tower, and the non-condensable gas in which the (meth) acrylic acid is deaerated is discharged to the upper part of the absorption tower.

The absorption process may be carried out by various methods such as a method of using a (meth) acrylic acid absorption tower as described above, and a method of injecting a (meth) acrylic acid-containing mixed gas into a container containing an absorption solvent.

If the recovery method employs an absorption process, the (meth) acrylic acid solution obtained in the absorption process may be fed to the distillation column 300 as a feed as shown in FIG. For example, the (meth) acrylic acid solution obtained in the lower part of the (meth) acrylic acid absorption tower may be supplied to the distillation column through a transfer line connecting the (meth) acrylic acid absorption tower and the distillation column.

On the other hand, in the absorption step, water is mainly used as an absorbing solvent for absorbing (meth) acrylic acid from the (meth) acrylic acid-containing mixed gas. Therefore, in order to improve the efficiency of the distillation process, which is a subsequent process, the above-mentioned recovery method includes an extraction process in which a (meth) acrylic acid solution is contacted with an extraction solvent to obtain an (meth) acrylic acid extract solution and a raffinate solution As shown in FIG.

In the extraction step, most of the water contained in the (meth) acrylic acid solution may be removed by supplying the (meth) acrylic acid solution to the extraction tower.

Specifically, the (meth) acrylic acid solution fed to the extraction column comes into contact with the extraction solvent of the extraction column and is discharged as an excess liquid in which a considerable amount of (meth) acrylic acid has been dissolved and an additional liquid which has lost a substantial amount of (meth) acrylic acid. At this time, the extract liquid, which is a relatively light phase, is obtained through the upper outlet of the extraction tower, and the additional balance, which is a relatively heavy phase, can be obtained through the lower outlet of the extraction tower.

As the extraction solvent, those having solubility and hydrophobicity with respect to (meth) acrylic acid can be used. In view of the kind of the solvent used in the subsequent distillation step and physical properties thereof, the solvent having a boiling point lower than that of the (meth) acrylic acid may be used. For example, the extraction solvent may be a hydrophobic solvent having a boiling point of 120 ° C or lower, or 10 ° C to 120 ° C or 50 ° C to 120 ° C. Specifically, the extraction solvent is selected from the group consisting of benzene, toluene, xylene, n-heptane, cycloheptane, cycloheptene, 1- heptene), ethylbenzene, methylcyclohexane, n-butyl acetate, isobutyl acetate, isobutyl acrylate, n-propyl acetate 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 And isopropyl-butyl-ether. A solvent may be used.

Thus, most of the water contained in the (meth) acrylic acid solution can be removed through a method of contacting the (meth) acrylic acid solution with the extraction solvent in the extraction tower. When the (meth) acrylic acid extract solution having a small water content is fed to the distillation column 300 through the extraction process as described above, the burden of the distillation process can be reduced and the energy efficiency of the entire process can be improved. Further, by reducing the processing burden of the distillation step and minimizing the polymerization reaction of (meth) acrylic acid which may occur upon distillation, it is possible to ensure a more efficient recovery of the (meth) acrylic acid.

In addition, the feed may include both the (meth) acrylic acid solution obtained in the absorption step and the (meth) acrylic acid extract obtained in the extraction step. In one example, at least a part of the (meth) acrylic acid solution obtained in the above absorption process may be supplied to the distillation process via an extraction process, and the remaining part may be directly supplied to the distillation process.

In the distillation step, a solution obtained by bringing the (meth) acrylic acid-containing mixed gas produced by the (meth) acrylic acid synthesis reaction into contact with an absorption solvent, or a solution obtained by dissolving the absorption solvent of the solution in an extraction solvent And the distilled solution is distilled to distill the solvent such as the absorption solvent and the extraction solvent. Accordingly, the distillation process can distill the feed containing a large amount of solvent to provide the crude (meth) acrylic acid from which most of the solvent has been removed. Specifically, the feed may be supplied through an absorption process or an extraction process, and may include 10 to 90% by weight, 20 to 80% by weight or 20 to 70% by weight of the solvent in the total components.

Also, for efficient distillation of the feed, the feed may comprise at least 10% by weight of (meth) acrylic acid in the total components. Specifically, the feed may comprise from 10 to 90% by weight, from 50 to 90% by weight or from 50 to 80% by weight of (meth) acrylic acid based on the total components. In addition to the (meth) acrylic acid and the solvent, the feed contains various organic by-products such as unreacted starting compounds, (meth) acrolein, low-boiling by-products produced in the synthesis reaction of (meth) acrylic acid, and high boiling point by-products and various impurities generated in the recovery process .

In the distillation step, the solvent such as water and the by-products are removed from the feed, and the distillation step is performed by removing 80 wt% or more, 90 wt% or more, 95 wt% or more, or 99 wt% or more of (meth) acrylic acid and 5 wt% Or crude (meth) acrylic acid containing up to 3% by weight of solvent. In particular, the (meth) acrylic acid recovery method according to an embodiment of the present invention is a method of recovering (meth) acrylic acid by discharging crude (meth) acrylic acid to the side of the distillation tower 300, (Meth) acrylic acid containing an acrylic acid dimer can be discharged. Thus, even if the step of separating the high boiling point byproduct is omitted, (meth) acrylic acid with high purity can be provided. The upper limit of the (meth) acrylic acid may be 100% by weight, and the solvent and the (meth) acrylic acid dimer may be added to the Methacrylic acid dimer may be 0 wt%. Further, the side portion of the distillation column 300 may mean a portion excluding the column top and the bottom.

As the distillation column, a pack column or a multi-stage column including a filler may be used. Specifically, a sieve tray column or a dual flow tray column may be used.

The feed may be fed to the center of the distillation column to effect efficient distillation. As an example, the feed may be fed to a stage located at a point corresponding to 40 to 60% of the total stage of the distillation column.

At this time, in order to efficiently separate (meth) acrylic acid contained in the feed from components such as water, acetic acid, or extraction solvent, the distillation may be performed in an azeotropic distillation method. The azeotropic solvent applied to the azeotropic distillation system may be azeotropic with water and acetic acid, and a hydrophobic azeotropic solvent which does not coexist with (meth) acrylic acid may be used. As such a hydrophobic azeotropic solvent, those having a boiling point lower than that of (meth) acrylic acid can be used. Specifically, as the hydrophobic azeotropic solvent, benzene, toluene, xylene, n-heptane, cycloheptane, cycloheptene, 1-heptene (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. The one or more solvents may be used.

The azeotropic solvent may be fed to the top of the distillation column. Therefore, the feed supplied to the distillation column 300 comes into contact with the azeotropic solvent introduced into the upper portion of the distillation column, and the distillation is carried out by evaporation and condensation while being heated to an appropriate temperature. Specifically, heat can be supplied to the distillation column through a reboiler at the bottom of the distillation column. More specifically, the temperature of the tower over the reboiler can be adjusted to about 45 ° C or less for efficient distillation of the feed.

In addition, the pressure of the column top can be adjusted to about 70 torr to 150 torr for efficient distillation of the feed.

Through such a distillation process, components with low boiling point in the feed can be discharged to the top of the distillation column 300 together with an azeotropic solvent. 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.

In one 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. Here, the separated organic phase may be supplied to the upper end of the distillation column 300 and used as an azeotropic solvent.

On the other hand, at least part of the (meth) acrylic acid contained in the feed may form a dimer or an oligomer while passing through the (meth) acrylic acid absorption tower, the extraction tower, or the distillation tower 300. In order to minimize such polymerization of (meth) acrylic acid, a conventional polymerization inhibitor may be added to the distillation column 300.

In the conventional recovery method, (meth) acrylic acid was discharged to the bottom of the distillation column to obtain a lower discharge liquid of a distillation column containing a high boiling point byproduct such as a polymer of (meth) acrylic acid and a polymerization inhibitor in addition to (meth) acrylic acid.

However, in the recovery method according to one embodiment of the present invention, crude (meth) acrylic acid is recovered from the side of the distillation column to obtain crude (meth) acrylic acid having a very low content of high boiling point byproducts and polymerization inhibitors. Further, crude (meth) acrylic acid obtained at the side of the distillation column has a high purity and is close to colorless, and a product of high purity can be provided through a crystallization process.

Specifically, the crude (meth) acrylic acid can be discharged at a stage located at a lower stage than the stage where the feed of the distillation column is fed. Since the stage in the distillation column means a discharge tube located on the tray, the top and top of the distillation column are different in position and can be distinguished on the bottom and top of the distillation column. More specifically, the crude (meth) acrylic acid can be discharged from the uppermost 50% to 100% of the entire stages of the distillation column. If a total of 30 distillation columns are used, the crude (meth) acrylic acid may be discharged at any one of the stages 15 to 30 of the distillation column.

At the side of the distillation tower, crude (meth) acrylic acid in liquid phase or gas phase can be recovered. The phase of crude (meth) acrylic acid obtained at the side of the distillation column may vary depending on the insertion position of the side discharge pipe. Specifically, a side discharge pipe may be inserted at a position capable of collecting the liquid on the tray for discharging crude (meth) acrylic acid, so that liquid crude (meth) acrylic acid can be forcibly discharged to the side of the tower. On the other hand, the side discharge pipe is positioned in the vapor phase rather than the liquid phase on the tray where the crude (meth) acrylic acid is discharged, so that the gaseous (meth) acrylic acid can be discharged to the top side via the condenser through the condenser. At this time, the condenser can be maintained at a pressure lower than the operation pressure of the distillation column in order to smoothly recover gaseous (meth) acrylic acid from the column side portion.

In Experimental Example 1 to be described later, it is confirmed that when the crude (meth) acrylic acid phase discharged from the side of the distillation column is in a gaseous state, the liquid phase contains fewer high-boiling by-products such as contrasting (meth) acrylic acid dimer. (Meth) acrylic acid in the gaseous phase, high-purity (meth) acrylic acid having a level equivalent to that of (meth) acrylic acid recovered through a high boiling point by-product distillation process Provided. Therefore, it is advantageous to recover gaseous (meth) acrylic acid in the vapor phase from the side of the distillation column in that it can provide high purity (meth) acrylic acid.

At the side of the distillation column, the content corresponding to 30 to 90% by weight of the total (meth) acrylic acid contained in the feed can be recovered. If less than 30% by weight of (meth) acrylic acid is recovered from the total (meth) acrylic acid contained in the feed at the side of the distillation column, the remaining amount of (meth) acrylic acid may be recovered from the bottom of the distillation column. Since the lower effluent of the distillation column contains high-boiling point by-products and polymerization inhibitor, it is only necessary to perform a high boiling point by-product separation process to provide crude (meth) acrylic acid having a purity enough to be supplied to the crystallization process. Therefore, if the content of matt (acrylic acid) recovered from the side of the distillation column is less than 30 wt%, a large amount of lower waste liquid may be supplied to the high-boiling by-product distillation process, resulting in energy loss. On the other hand, if (meth) acrylic acid exceeding 90 wt% of the total (meth) acrylic acid contained in the feed is recovered at the side of the distillation column, the high boiling point component accumulates in the bottom so that the viscosity of the bottom liquid becomes extremely high, So that it may be difficult to continuously operate the distillation column. Accordingly, at the side of the distillation column, the (meth) acrylic acid within the above-mentioned range is recovered and supplied to the crystallization process to obtain high purity (meth) acrylic acid, and the amount of the lower discharge liquid can be reduced to save a great deal of energy.

The content of (meth) acrylic acid obtained at the side of the distillation column can be adjusted by regulating the flow rate of the discharge pump or by adjusting the pressure of the condenser located together with the side discharge pipe.

At the lower part of the distillation column 300, high boiling point by-products such as polymers of (meth) acrylic acid and (meth) acrylic acid, polymerization inhibitors and the like may be discharged. Accordingly, the recovery method is characterized in that the lower effluent obtained in the lower part of the distillation column is distilled to further recover the (meth) acrylic acid in the lower effluent, thereby obtaining crude (meth) acrylic acid at the upper part of the high boiling point by- Point byproduct separation process.

Specifically, as shown in FIG. 2, the lower effluent obtained from the bottom of the distillation column may be supplied to the high boiling point byproduct separation tower 400 to separate the high boiling point byproducts contained in the lower effluent. Further, additional crude (meth) acrylic acid can be obtained on top of the high boiling point byproduct separation column 400. At this time, the high-boiling by-product separation process can be carried out under ordinary conditions, so the process conditions and the like are not specifically limited.

The crude (meth) acrylic acid recovered through the above process can be obtained as (meth) acrylic acid of higher purity through an additional crystallization process.

2, the crude (meth) acrylic acid (stream 2 in FIG. 2) obtained at the side of the distillation column 300 is supplied directly to the crystallizer 500 without passing through the high boiling point byproduct separation column 400 . However, since the lower effluent (stream 1 in FIG. 2) of the distillation column 300 contains a large amount of high-boiling by-products, it can be supplied to the crystallizer 500 via the high boiling point byproduct separation column 400. If the (meth) acrylic acid content in the lower effluent of the distillation column 300 is small, it can be directly introduced into the decomposition step of the acrylic acid dimer without going through the high boiling point byproduct separation column 400. Therefore, when crude (meth) acrylic acid is obtained from the side of the distillation column 300 as shown in FIG. 2, it is directly introduced into the decomposition step of the (meth) acrylic acid dimer without the step of separating the high boiling point byproduct, Can be recovered.

The crude (meth) acrylic acid fed to the crystallizer can be recrystallized to provide high purity (meth) acrylic acid. The crystallization process of crude (meth) acrylic acid can be carried out under ordinary conditions. By way of non-limiting example, crude (meth) acrylic acid may be dynamically crystallized to provide high purity (meth) acrylic acid. Specifically, in order to dynamically crystallize crude (meth) acrylic acid, liquid crude (meth) acrylic acid can be first flowed into the inner wall of the tube in the form of a falling film. The temperature of the tube can be controlled to be lower than the freezing point of (meth) acrylic acid to form crystals on the inner wall of the tube. The temperature of the tube can then be increased to near the freezing point of (meth) acrylic acid to sweate about 5 wt% of (meth) acrylic acid. Then, the high-purity (meth) acrylic acid can be obtained by removing the residual dissolving solution sweating from the tube and recovering crystals formed on the inner wall of the tube.

In the above (meth) acrylic acid recovery method, 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, after, or simultaneously with each process can be further included and operated.

According to another embodiment of the present invention, there is provided a distillation column comprising a feed inlet and an upper, side and lower outlet; (Meth) acrylic acid inlet connected to the side outlet of the distillation tower through a crude (meth) acrylic acid transfer line and a (meth) acrylic acid outlet for discharging (meth) acrylic acid obtained by recrystallizing the introduced crude (meth) acrylic acid (Meth) acrylic acid recovery apparatus comprising a crystallizer which is obtained by reacting a (meth) acrylic acid.

The distillation column 300 may be a packed column or a multi-column column having a filler therein, and may be a sieve tray column or a dual flow tray column.

In addition, the crystallizer 500 may include a pipe and a circulation pump. Specifically, the tube may be provided with a reservoir capable of storing a component to be recrystallized at a lower portion thereof. In addition, the surface of the tube is composed of a double jacket so that the temperature inside the tube can be controlled to be constant. Such a tube having a length of about 0.5 to 2 m can be used. In addition, the circulation pump can transfer the components contained in the reservoir to the upper portion of the tube, and allow the components to flow in the form of a falling film on the inner wall of the tube so that crystals can be formed on the inner wall of the tube. However, as the crystallizer, any crystallizer commonly used in the technical field of the present invention can be used.

(Meth) acrylic acid-containing mixed gas, and a (meth) acrylic acid-containing (meth) acrylic acid-containing solution having an aqueous solution outlet through which the (meth) acrylic acid solution obtained by contacting the mixed gas with an absorbing solvent is discharged. An absorber may additionally be included. The aqueous solution outlet of the absorption tower can be connected via the aqueous feed line to the feed inlet of the distillation column.

As the (meth) acrylic acid absorption tower, a packed tower or a multistage tray tower can be used for improving the contact efficiency between the (meth) acrylic acid-containing mixed gas and the absorption solvent. The filling column may be filled with a filler such as a rashing ring, a pall ring, a saddle, a gauze, or a structured packing.

In order to lower the processing load of the distillation column, the recovery apparatus is provided with an aqueous solution inlet connected to the aqueous solution outlet of the absorption tower through an aqueous solution transfer line, a (meth) acrylic acid extract obtained by contacting the introduced (meth) acrylic acid solution with the extraction solvent, And a (meth) acrylic acid extraction tower having an outlet for the extracted liquid to be discharged and an outlet for the additional residual liquid discharged after the residual balance is settled.

For example, the extraction outlet of the extraction column may be connected to the feed inlet of the distillation column via an extractive feed line. Accordingly, all the (meth) acrylic acid solution discharged from the absorption tower can be supplied to the distillation column through the extraction tower. In another example, the aqueous solution outlet of the absorption tower and the extraction outlet of the extraction column may be connected to the feed inlet of the distillation column through the same or different transfer lines. Accordingly, a part of the (meth) acrylic acid solution discharged from the absorption tower is supplied to the extraction tower, and the remainder of the (meth) acrylic acid solution can be supplied to the distillation tower and operated.

As the (meth) acrylic acid extraction column, 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 may be a Karr type reciprocating plate column, a rotary-disk contactor, a Scheibel column, a Kuhni column, a spray extraction column, A packed extraction column, a pulsed packed column, and the like.

In addition, the (meth) acrylic acid aqueous solution transfer line, the extract liquid transfer line, the phase separation tank 350, the high boiling point byproduct separation tower 400, and the like can be employed as the structures commonly used in the technical field of the present invention . In addition, the collection device may further include a configuration that is conventionally employed in the technical field of the present invention.

Best Mode for Carrying Out the Invention Hereinafter, the functions and effects of the present invention will be described in more detail through specific embodiments of the present invention. It should be understood, however, that the invention is not limited to the disclosed embodiments.

Experimental Example  1: distillation tower Side  And the Crude acrylic acid  compare

( Comparative Example  One)

A total of 30 stages of dual flow tray column distillation columns having an inner diameter of 70 mm were used as the distillation column 300 of the recovery apparatus shown in FIG. 1, and the top pressure was adjusted to 110 torr.

An acrylic acid solution containing 65.4% by weight of acrylic acid, 2.0% by weight of acetic acid, 31.8% by weight of water and 0.8% by weight of other components at a fourteenth stage located at the 14th position from the top of the distillation tower 300 was fed at a flow rate of about 35 g / Respectively. A portion of the toluene reflux stream separated in the phase separation tank 350 was supplied to the first stage, which is the uppermost stage of the distillation column, as an azeotropic solvent. The amount of toluene reflux stream fed was adjusted so that the reflux ratio (ratio of flow rate of reflux to effluent) was about 5.5. In addition, heat was supplied through a reboiler at the bottom of the distillation column 300 to adjust the temperature of the 16th stage to be at least about 80 ° C and the temperature of the 12th stage to not exceed about 65 ° C. After a stable operation for 10 hours, a distillate was obtained at a flow rate of about 85 g / min from the steady state to the top of the distillation column 300 and a flow rate of about 22 g / min to the bottom floor of the distillation column 300 To obtain an acrylic acid stream in which most of the water was removed (stream 1 in Fig. 1).

( Example  One)

A total of 30 dual flow tray columns having an inner diameter of 70 mm was used as the distillation column 300 of the recovery apparatus shown in FIG. 2, and the top pressure was adjusted to 110 torr.

An acrylic acid solution containing 65.4% by weight of acrylic acid, 2.0% by weight of acetic acid, 31.8% by weight of water and 0.8% by weight of other components at a fourteenth stage located at the 14th position from the top of the distillation tower 300 was fed at a flow rate of about 35 g / Respectively. A portion of the toluene reflux stream separated in the phase separation tank 350 was supplied to the first stage, which is the uppermost stage of the distillation column, as an azeotropic solvent. The amount of toluene reflux stream fed was adjusted so that the reflux ratio (ratio of reflux to reflux ratio) was about 5.7. In addition, heat was supplied through the reboiler at the bottom of the distillation column 300 to adjust the temperature of the 16th stage to be about 85 ° C or higher and the temperature of the 12th stage to not exceed about 65 ° C. After a stable operation for 10 hours, a distillate is obtained at a flow rate of about 85 g / min from the steady state to the top of the distillation column 300, and the distillate is fed to the bottom of the distillation column 300 at a high rate of about 11.5 g / (Stream 1 in FIG. 2) containing the by-products. Then, a crude acrylic acid stream (stream No. 2 in FIG. 2) in a liquid phase of about 11 g / min was obtained at the thirtieth position from the top of the distillation column 300 and contained in the crude acrylic acid obtained in the above- The content of acrylic acid was about 49 wt% of the total acrylic acid.

( Example  2)

Min. In the same manner as in Example 1 except that the flow rate of the sidestream drain pump was adjusted such that the content of acrylic acid obtained in Step 30 corresponds to about 84% by weight of the total acrylic acid, The distillate was obtained at a flow rate and a stream containing the high boiling point byproduct at a flow rate of about 4 g / min was obtained at the bottom of the distillation column 300 (stream 1 in FIG. 2) And a liquid crude acrylic acid stream (stream No. 2 in FIG. 2) was obtained at a flow rate of 18.5 g / min.

( Example  3)

A dual flow tray column having a total of 30 stages with an inner diameter of 70 mm was used as the distillation column 300 of the recovery apparatus as shown in FIG. 2, and a vapor phase was formed at the 30th stage located at the thirtieth position from the top of the distillation column 300, To obtain crude acrylic acid, a side discharge tube was placed in the vapor phase separated from the liquid phase on the tray. As the side discharge pipe, a side discharge pipe having a condenser for condensing and discharging gaseous acrylic acid was used. As described above, the side discharge pipe was inserted and the top pressure of the distillation column was adjusted to 110 torr.

An acrylic acid solution containing 65.4% by weight of acrylic acid, 2.0% by weight of acetic acid, 31.8% by weight of water and 0.8% by weight of other components at a fourteenth stage located at the 14th position from the top of the distillation tower 300 was fed at a flow rate of about 35 g / Respectively. A portion of the toluene reflux stream separated in the phase separation tank 350 was supplied to the first stage, which is the uppermost stage of the distillation column, as an azeotropic solvent. The amount of toluene reflux stream fed was adjusted so that the reflux ratio (ratio of reflux to reflux ratio) was about 5.7. In addition, heat was supplied through the reboiler at the lower end of the distillation column 300 to adjust the temperature of the 16th stage to be higher than about 80 ° C and the temperature of the 12th stage to not exceed about 70 ° C. After a stable operation for 10 hours, a distillate was obtained at a flow rate of about 85 g / min from the steady state to the top of the distillation column 300, and a high boiling point of about 10 g / min to the bottom of the distillation column 300 A stream containing byproducts (stream 1 in FIG. 2) was obtained. Then, a gaseous acrylic acid stream (stream 2 in FIG. 2) was obtained at a thirty-th stage from the top of the distillation column 300 at a flow rate of about 12 g / min. The content was about 55% by weight of the total acrylic acid.

( Example  4)

In the same manner as in Example 3, except that the discharge pressure of the condenser attached to the side discharger was adjusted so that the content of acrylic acid obtained in Step 30 corresponds to about 79% by weight of the total acrylic acid, (Stream 1 in FIG. 2) containing about 5 g / min of high boiling point byproduct at the lower part of the distillation column 300 was obtained at a flow rate of about 85 g / The crude acrylic acid stream in the vapor phase (stream 2 in FIG. 2) was obtained at a flow rate of about 18 g / min at the 30th stage.

Table 1 shows the composition, recovery and color of the acrylic acid mixture in which most of the water obtained in Comparative Example 1 is removed and the acrylic acid obtained in Examples 1 to 4.

Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Side Emission Rate ⁽¹⁾ - 49 wt% 84 wt% 55 wt% 79 wt% Side discharge phase ⁽²⁾ - Liquid phase Liquid phase weather weather Reboiler temperature 137.5 ℃ 137.8 ℃ 139.5 ° C 139.9 ° C 142.4 DEG C Acrylic acid recovery rate 98.6% 99.0% 98.6% 99.1% 99.0% Tower bottom
ingredient Top side component Bottom component Top side component Bottom component Top side component Bottom component Top side component Bottom component toluene 0 0 0 0 0 0.005 0 0.004 0 Acetic acid 0.066 0.135 0.069 0.086 0.044 0.137 0.082 0.129 0.067 Furfural 0.019 0.018 0.028 0.018 0.031 0.013 0.026 0.021 0.032 Benzaldehyde 0.026 0.016 0.038 0.016 0.046 0.009 0.036 0.019 0.047 DAA ⁽³⁾ 5.3 0.060 5.2 0.079 10.0 0.011 6.0 0.013 9.2 Hydroquinone 0.193 0.027 0.346 0.027 0.536 0 0.340 0 0.478 Propionic acid 0.026 0.027 0.026 0.027 0.023 0.027 0.026 0.027 0.025 water 0.024 0.012 0.035 0.019 0.039 0.017 0.028 0.024 0.046 Acrylic acid 92.8 99.3 91.8 99.8 83.9 99.8 92.0 99.8 87.6 APHA ⁽⁴⁾ > 500 360 368 3 3

(Component units of crude acrylic acid:% by weight)

(1) Side emission ratio: the weight ratio of acrylic acid discharged from the side of the distillation column to the total acrylic acid contained in the acrylic acid solution supplied to the distillation column.

(2) Side outlet phase: The phase of crude acrylic acid obtained from the side of the distillation column.

(3) DAA: It is a dimer of acrylic acid.

(4) APHA: The color measured by APHA and ASTM D1209 is colorless as the value is smaller, and yellow as the value is larger.

Referring to Table 1, it was confirmed that the crude acrylic acid obtained in the side portions of Examples 1 to 4 contains less acrylic acid dimer having a high boiling point as compared with Comparative Example 1, and the color according to APHA is nearly colorless. Further, in Examples 3 and 4, crude acrylic acid having less high boiling point acrylic acid dimer was obtained as compared with Examples 1 and 2, and crude acrylic acid having a color of about 3 according to APHA was obtained through a water distillation column .

Experimental Example 2: Recrystallization of crude acrylic acid obtained from the side and bottom of the distillation tower

( Comparative Example  2)

A crystallizer 500 having a glass tube and a circulation pump was prepared for recrystallizing the most of the water-removed acrylic acid stream (stream 1 in FIG. 1) obtained under the distillation tower 300 of Comparative Example 1. The glass tube had a reservoir at the bottom, a length of 1 m, and a surface of 1 inch ID, which was formed of a double jacket so that the temperature inside the tube could be controlled constantly. The circulation pump is configured to transfer the liquid in the reservoir to the upper portion of the glass tube, and to allow the liquid to flow in the form of a falling film on the inner wall surface of the glass tube.

The acrylic acid mixture (stream 1 in FIG. 1) obtained at the bottom of the distillation column 300 of Comparative Example 1 was directly fed to the reservoir of the crystallizer 500 prepared above. Then, the acrylic acid mixture supplied to the reservoir was caused to flow in the form of a drop film on the wall of the glass tube by a circulation pump, and the temperature of the double tube jacket was lowered below the freezing point of acrylic acid. As a result, about 70 to 85% by weight of acrylic acid crystallized on the inner wall of the glass tube. Thereafter, the circulation pump was stopped, and the temperature of the jacket was raised to the vicinity of the solidifying point of acrylic acid to sweat about 5 wt% of acrylic acid. After sweating, the residual solution was discharged by a pump. Then, the temperature of the double jacket of the glass tube was raised above the solidifying point of acrylic acid to melt the crystals formed on the inner wall of the glass tube, and the resultant was discharged by a pump. The above-mentioned dynamic crystallization process was repeated two more times using the molten acrylic acid as a feed for the next crystallization step. Thus, recrystallized acrylic acid was obtained through a total of three dynamic crystallization processes.

( Comparative Example  3)

The acrylic acid stream (stream 1 in FIG. 1) obtained at the bottom of the distillation column 300 of Comparative Example 1 was supplied to the high-boiling byproduct separation column 400 of the recovery apparatus shown in FIG. 1 at a flow rate of about 22 g / min. The temperature of the column top was adjusted to be about 60 ° C or higher through a reboiler at the bottom of the high boiling point byproduct separation column 400. After a stable operation for 10 hours, a crude acrylic acid stream (stream 2 of FIG. 1) was obtained at a flow rate of about 20 g / min to the top of the high boiling point byproduct separation column 400 in a steady state. The crude acrylic acid stream (stream 2 in FIG. 1) contained 0.16% by weight of acetic acid, 0.02% by weight of furfural, 0.003% by weight of benzaldehyde, 0.0097% by weight of acrylic acid dimer, 0.029% by weight of pyropionic acid, 0.08% By weight.

The crude acrylic acid stream (stream 2 in FIG. 1) was supplied to the crystallizer 500 and recrystallized under the same conditions as in Comparative Example 2 to obtain recrystallized acrylic acid (stream 3 in FIG. 1).

( Example  5)

A liquid crude acrylic acid stream (stream 2 in FIG. 2) obtained from the side of the distillation column 300 of Example 2 was directly fed to the crystallizer 500. Thereafter, recrystallization was carried out under the same conditions as in Comparative Example 2 to obtain recrystallized acrylic acid (stream 3 in FIG. 2).

( Example  6)

The gaseous acrylic acid stream (stream 2 in FIG. 2) obtained at the side of the distillation column 300 of Example 4 was directly fed to the crystallizer 500. Thereafter, recrystallization was carried out under the same conditions as in Comparative Example 2 to obtain recrystallized acrylic acid (stream 3 in FIG. 2).

The compositions of the impurities contained in the recrystallized acrylic acid obtained in Comparative Examples 2 to 3 and Examples 5 to 6 and the colors according to APHA of the recrystallized acrylic acid are shown in Table 2.

Comparative Example 2 Comparative Example 3 Example 5 Example 6 toluene 0 0 0 0 Acetic acid 198 320 208 282 Furfural 9 0 2 0 Benzaldehyde 9 0 0 0 DAA 761 11 157 47 Hydroquinone 110 0 0 0 Propionic acid 128 101 106 103 water 275 126 387 109 Maleic acid 310 2 24 6 APHA 135 3 7 3

(Content of impurities: ppm)

Referring to Table 2, it is confirmed that the acrylic acid flow obtained from the lower part of the water distillation column 300 as in Comparative Example 2 can not be used as a high purity product because the color according to APHA is 135 even though it is subjected to a crystallization process. On the other hand, as in Examples 5 and 6, the crude acrylic acid stream obtained from the side of the water distillation column 300 showed color 7 and 3 according to APHA after the crystallization process, and thus it was confirmed to be suitable for use as a high purity product. In particular, comparing Examples 5 and 6 with Comparative Example 3, it was found that the Examples provided acrylic acid having a purity as high as Comparative Example 3 through the high boiling point byproduct separation column without going through the high boiling point byproduct separation column . Accordingly, it was confirmed that the acrylic acid recovery method according to the embodiment can efficiently recover acrylic acid with high purity.

300: distillation tower
350: phase separation tank
400: High boiling point byproduct separation tower
500: crystallizer

Claims (7)

(Meth) acrylic acid, 10 to 33.8 wt.% Of solvent and the balance of impurities to distill off the bottom of the distillation column to produce 99.8 wt.% Or more of (meth) acrylic acid, 0.079 wt. ) A distillation step of obtaining a crude (meth) acrylic acid containing a dimer of acrylic acid and a residual solvent,
A 30-stage dual flow tray column is used as the distillation column,
Heat is supplied to the distillation column so that the temperature of the 16th stage becomes 80 ° C or higher and the temperature of the 12th stage does not exceed 70 ° C,
(Meth) acrylic acid corresponding to 55 to 84% by weight of the total (meth) acrylic acid contained in the feed at the side of the distillation column.
The method of claim 1, wherein the recovery method further comprises an absorption step of contacting the (meth) acrylic acid-containing mixed gas with an absorption solvent to obtain a (meth) acrylic acid solution before the distillation step.
The method according to claim 2, wherein the recovery method further comprises: (meth) acrylic acid solution additionally comprising an extraction step of contacting the (meth) acrylic acid solution with an extraction solvent between the absorption step and the distillation step to obtain a (meth) A method for recovering acrylic acid.
The method according to claim 1, wherein the crude (meth) acrylic acid is discharged from the uppermost 50% to 100% (lowest stage) of the entire stages of the distillation column.
The method according to claim 1, wherein the side of the distillation column is a liquid or gaseous (meth) acrylic acid.
The method of claim 1, wherein the recovery method further comprises distilling the bottom effluent obtained at the bottom of the distillation column to obtain a high boiling point byproduct separation process to obtain crude (meth) acrylic acid at the top of the high boiling point byproduct separation column Meth) acrylic acid.
The method for recovering (meth) acrylic acid according to claim 1 or 6, further comprising a crystallization step of recrystallizing the crude (meth) acrylic acid.

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