KR20170057703A - Preparation method of (meth)acrylic acid - Google Patents

Abstract

The present invention relates to a process for producing (meth) acrylic acid. In the process for producing (meth) acrylic acid, the reaction distillation apparatus is smoothly and quickly started up by adjusting the viscosity of the waste liquid supplied to the reactive distillation apparatus to a specific range and adjusting the conditions for applying heat to the waste liquid, Heat supply can be prevented and (meth) acrylic acid can be efficiently obtained from the Michael adduct without any problems caused by by-products such as maleic acid.

Description

TECHNICAL FIELD The present invention relates to a method for producing (meth) acrylic acid,

The present invention relates to a process for producing (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 Meth) acrolein, an inert gas, carbon dioxide, water vapor, and various organic by-products (acid, low boiling point byproduct, high boiling point byproduct, etc.) by the above reaction are 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.

Through this process, a high boiling point byproduct containing (meth) acrylic acid, a Michael adduct such as 2 to 5 monomers of (meth) acrylic acid, maleic acid, and other high boiling point impurities is obtained, which improves the yield of (meth) (Meth) acrylic acid is further recovered by decomposing the Michael adduct contained in the byproduct by-product.

However, since the maleic acid contained in the high-boiling point by-product is liable to precipitate, the viscosity of the (meth) acrylic acid solution is raised to lower the decomposition efficiency of the Michael adduct, and the (meth) acrylic acid and the copolymer Resulting in a problem of lowering the yield of acrylic acid.

The present invention relates to a process for producing (meth) acrylic acid from a methyl adduct, which can effectively start up an apparatus for obtaining (meth) acrylic acid from a waste solution containing a Michael adduct or the like, (Meth) acrylic acid.

According to an embodiment of the present invention, there is provided a process for producing (meth) acrylic acid by using a reactive distillation apparatus comprising a reaction column in which a decomposition reaction of a Michael adduct is carried out and a distillation column in which a decomposition product is distilled is connected and a heat exchanger A waste liquid having a viscosity between the lower liquid of the high boiling point material separating column and the waste oil discharged from the reactive distillation apparatus is discharged from the waste liquid discharged from at least one of the production process of the (meth) acrylic acid and the recovery process, ; And supplying heat such that the difference between the temperature of the waste liquid contained in the decomposition tank and the internal temperature of the heat exchanger is constant.

In the above production method, a waste liquid having a viscosity of 5 to 40 cP at 100 ° C can be supplied to the reactive distillation apparatus.

As the waste liquid to be fed to the reactive distillation apparatus, a mixture of the lower liquid of the high boiling point material separating column and the waste oil discharged from the reactive distillation apparatus may be used. Specifically, the lower liquid of the high boiling point material separating column and the waste oil discharged from the reactive distillation apparatus may be mixed in the reaction distillation apparatus in a volume ratio of 0.1: 1 to 5: 1.

In the step of supplying the heat, the heat may be supplied so that the difference (ΔT = | T1-T2 |) between the temperature (T1) of the waste liquid contained in the decomposition tank and the internal temperature (T2) of the heat exchanger is 2 to 20 ° C. Then, in the step of supplying the heat, the heat is supplied so that the change amount of the difference (ΔT = | T1-T2 |) between the temperature (T1) of the waste liquid contained in the decomposition tank and the internal temperature .

In the process for producing (meth) acrylic acid according to an embodiment of the present invention, the viscosity of the waste liquid supplied to the reactive distillation apparatus is adjusted to a specific range and the condition for applying heat to the waste liquid is controlled, (Meth) acrylic acid can be efficiently obtained from the Michael adduct without any problem caused by by-products such as maleic acid because excessive heat supply can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a reactive distillation apparatus capable of carrying out a process for producing (meth) acrylic acid according to an embodiment of the present invention. FIG.
2 is a diagram schematically showing a high boiling point material separation column.

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

According to an embodiment of the present invention, there is provided a process for producing (meth) acrylic acid by using a reactive distillation apparatus comprising a reaction column in which a decomposition reaction of a Michael adduct is carried out and a distillation column in which a decomposition product is distilled is connected and a heat exchanger A waste liquid having a viscosity between the lower liquid of the high boiling point material separating column and the waste oil discharged from the reactive distillation apparatus is discharged from the waste liquid discharged from at least one of the production process of the (meth) acrylic acid and the recovery process, ; And supplying heat such that the difference between the temperature of the waste liquid contained in the decomposition tank and the internal temperature of the heat exchanger is constant.

(Meth) acrylic acid can be produced by catalytic gas phase oxidation of propylene and / or acrolein, and then removing unreacted materials and by-products from the obtained reaction product. However, in the (meth) acrylic acid production process and / or the recovery process, a Michael adduct such as 2- to 5-mer or oligomer of acrylic acid is formed by heat to lower the yield of (meth) acrylic acid. Accordingly, a method for decomposing Michael adducts to recover (meth) acrylic acid has been introduced. However, the waste liquid discharged from the (meth) acrylic acid production process and / or the recovery process contains by-products such as maleic acid in addition to the Michael addition. Since the maleic acid is easily precipitated, the viscosity of the (meth) (Meth) acrylic acid as a decomposition product, thereby lowering the yield of (meth) acrylic acid.

However, the present inventors have found that by controlling the viscosity of a waste liquid to a specific range and controlling the condition of applying heat to the waste liquid and the like, it is possible to efficiently decompose the Michael adduct without interfering with by-products such as maleic acid and obtain (meth) And the present invention has been completed.

In the method for producing (meth) acrylic acid according to one embodiment, the (meth) acrylic acid can be recovered by efficiently decomposing the Michael adduct contained in the waste liquid by using the reactive distillation method. When the reactive distillation method is employed, a sufficient processing time for treating the waste liquid can be ensured. At the same time as the decomposition of the Michael adduct, the decomposed (meth) acrylic acid is recovered by distillation so that the equilibrium shifts in the direction of (meth) There is an advantage that decomposition is promoted. In addition, the process for producing (meth) acrylic acid of the embodiment may further comprise feeding the (meth) acrylic acid recovered at the top of the distillation column to a high boiling point material separating column, if necessary, The concentration of the Michael adduct, maleic acid and high boiling point impurities in the stream can be lowered.

In order to produce (meth) acrylic acid from a waste solution through a reactive distillation method, a reactive distillation apparatus including a reaction distillation column in which a decomposition reaction of Michael adduct and distillation of decomposition products occur simultaneously and a heat exchanger serving as a heat source thereof can be used.

At this time, a continuous type circulation type heat exchanger may be used as the heat exchanger so as to supply a sufficient amount of heat to the waste liquid and circulate the waste liquid in the reactive distillation apparatus. The reactive distillation column 300 and the heat exchanger 400 may be connected as shown in FIG. 1, but the device structure in which the process for producing (meth) acrylic acid of the present invention is performed is not limited thereto.

In the method for producing (meth) acrylic acid according to one embodiment, the waste liquid is supplied to the reactive distillation apparatus.

Especially, by adjusting the viscosity of the waste liquid to be supplied at this time to a specific range, the reactive distillation device can be smoothly and quickly started up to enable stable operation.

Specifically, the waste liquid is a waste liquid discharged from at least one of the production process of the (meth) acrylic acid and the recovery process, and is prepared so as to have a viscosity between the lower liquid of the high boiling point material separation column and the waste oil discharged from the reactive distillation apparatus .

The reaction product gas usually obtained by catalytic gas phase oxidation of propylene and / or acrolein includes by-products such as unreacted materials and high-boiling substances in addition to (meth) acrylic acid. Thus, after the reaction product gas is collected to obtain a (meth) acrylic acid-containing solution, by-products such as high boiling point materials are removed from the (meth) acrylic acid-containing solution through the high boiling point material separation column 100 as shown in FIG. 2, ) Acrylic acid can be obtained. Such crude (meth) acrylic acid may be recovered at the top of the high boiling point material separating column and subjected to further purification to provide high purity (meth) acrylic acid, while byproducts such as high boiling point materials . The lower solution of the high boiling point material separating column contains Michael adducts such as dimer, trimer, tetramer and dimer of (meth) acrylic acid, and acids such as maleic acid.

On the other hand, the waste oil discharged from the reactive distillation apparatus may be waste oil discharged through line 7 of FIG. 1 through the production method according to one embodiment of the present invention or may be waste oil discharged through other reactive distillation methods .

The waste liquid used in the process for producing (meth) acrylic acid according to this embodiment may have a viscosity between the lower liquid of the high boiling point material separating column and the waste oil discharged from the reactive distillation apparatus. Specifically, a waste liquid having a viscosity of 5 to 40 cP at 100 ° C may be supplied to the reactive distillation apparatus. Within this range, the reactive distillation apparatus can be smoothly and quickly started up to enable stable operation.

In order to make the waste liquid have a viscosity between the lower liquid of the high boiling point material separating column and the waste oil discharged from the reactive distillation apparatus, a mixture of the lower liquid of the high boiling point material separating column and the waste oil discharged from the reactive distillation apparatus Can be used. At this time, the lower liquid of the high boiling point material separating column and the waste oil discharged from the reactive distillation apparatus may be mixed and supplied in a volume ratio of 0.1: 1 to 5: 1. The composition of the waste liquid supplied to the reactive distillation apparatus affects the initial behavior of the reactive distillation column. By supplying the waste liquid having the composition as described above, the waste liquid can be circulated smoothly and quickly in the heat exchanger, The time required to reach the steady state is shortened.

More specifically, the mixture of the lower liquid of the high boiling point material separating column and the waste oil discharged from the reactive distillation apparatus contains 1 to 50% by weight or 3 to 40% by weight of acrylic acid based on the total weight, Adducts, maleic acid, other by-products, and the like.

Meanwhile, the process for producing (meth) acrylic acid according to one embodiment of the present invention supplies heat to a reaction distillation apparatus for decomposition of Michael adduct and distillation of decomposition products. In this case, the stability of the reactive distillation process can be improved by supplying heat such that the difference between the temperature of the waste liquid contained in the decomposition tank and the internal temperature of the heat exchanger is kept constant in the process for producing (meth) acrylic acid. (Meth) acrylic acid and a copolymer (meth) acrylic acid, which are degradation products, by decomposition of maleic acid contained in the waste liquid to increase the viscosity of the waste liquid, Resulting in a problem of lowering the yield of acrylic acid. In addition, the byproducts such as maleic acid caused contamination in the apparatus, thereby breaking the balance of heat supply during start-up of the apparatus, thereby further increasing pollution and deterioration in the apparatus.

However, when the waste liquid having a specific range of viscosity is supplied as described above and heat is supplied so that the difference between the temperature of the waste liquid contained in the decomposition tank and the internal temperature of the heat exchanger is constant, And the internal temperature of the decomposition tank can stably reach the decomposition temperature of the Michael adduct.

(? T = | T1 - T2 |) between the temperature (T1) of the waste liquid contained in the decomposition tank and the internal temperature (T2) of the heat exchanger is 2 to 20 ° C or 2 to 10 ° C Heat can be supplied. At this time, the temperature (T1) of the waste liquid contained in the decomposition tank may be the same as the internal temperature of the decomposition tank, and the internal temperature (T2) of the heat exchanger may mean the highest temperature in the heat exchanger. It is possible to effectively suppress the occurrence of contamination of the heat exchanger by controlling the range of DELTA T as described above and to suppress deterioration of properties such as viscosity increase of the waste liquid and to enable stable operation for a long time.

Further, in the step of supplying the heat, the difference (? T = | T1 - T2 |) between the temperature (T1) of the waste liquid contained in the decomposition tank and the internal temperature (T2) of the heat exchanger should be kept constant. Specifically, in the step of supplying the heat, heat can be supplied so that the change amount of DELTA T is 5 DEG C or less, 3 DEG C or less, or 1 DEG C or less. When the above DELTA T is kept constant, the change amount of DELTA T is 0 DEG C, so that the lower limit of the amount of change DELTA T may be 0 DEG C. [

In a typical reaction distillation apparatus, a heat source is supplied so that the temperature of the reaction liquid in the decomposition tank becomes a set value. However, in the production method of this embodiment, the reaction solution in the decomposition tank is concentrated by keeping a constant? T value at the start-up of the reactive distillation apparatus, and the amount of heat is supplied to the heat exchanger so that the temperature of the reaction solution gradually reaches the set value.

As described above, the reaction distillation apparatus is smoothly and quickly started up by adjusting the viscosity of the waste liquid supplied to the reactive distillation apparatus to a specific range and adjusting the conditions for applying heat to the waste liquid, etc., thereby preventing excessive heat supply (Meth) acrylic acid can be efficiently obtained from the Michael adduct without any problems due to by-products such as maleic acid.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG. However, this is provided as an example of the invention, and the scope of the invention is not limited thereto in any sense.

Comparative Example 1: Decomposition of Michael adduct and recovery of acrylic acid

1, a reaction distillation column 300 including a decomposition column and a distillation column, a natural circulation type heat exchanger 400, and a condenser 600 are connected as shown in FIG. 1, in order to recover the acrylic acid by decomposing the Michael adduct . In addition, a waste oil discharge pump 500 is installed in the lower part of the reactive distillation column 300 to continuously discharge the remaining waste oil from which acrylic acid is recovered from the waste liquid. The condenser 600 condenses the distillate discharged from the upper portion of the distillation column, and a portion of the distillate is fed to the distillation column as reflux and the remaining portion is obtained as acrylic acid and re-supplied to the high boiling point separating column.

In order to start up the reactive distillation column, waste oil obtained in a reactive distillation apparatus of another process was supplied as an initial reaction liquid to the decomposition tank. 2.1% by weight of acrylic acid, 24.7% by weight of acrylic acid dimer and 5.2% by weight of maleic acid were contained in the waste oil, and the viscosity at 100 ° C was 51 cP.

In Comparative Example 1, circulation in the heat exchanger and the decomposition tank was not smooth, and excessive heat was supplied to the heat exchanger to raise the internal temperature of the decomposition tank. At this time, a temperature difference of about 15 ° C or more occurred between the internal temperature of the decomposition tank and the internal temperature of the heat exchanger. In addition, some of the maleic acid and the polymerization inhibitor were spilled together with acrylic acid on the top of the reactive distillation column. It took a long time for the reactive distillation column to reach the steady state.

Comparative Example 2: Decomposition of Michael adduct and recovery of acrylic acid

Under the same conditions as in Comparative Example 1, the lower liquid of the high boiling point material separating column was supplied as an initial reaction liquid to the decomposition tank for starting up the reactive distillation column. The lower solution contained 44.4 wt% of acrylic acid, 28.4 wt% of acrylic acid dimer, and 6.1 wt% of maleic acid, and the viscosity at 100 ° C was 2 cP.

In Comparative Example 2, circulation of the lower liquid between the heat exchanger and the decomposition tank was smooth compared to Comparative Example 1. At this time, the difference between the internal temperature of the decomposition tank and the internal temperature of the heat exchanger was about 2 ° C.

However, in Comparative Example 2, the acrylic acid present in the lower liquid of the high boiling point material separation column was excessively distilled, resulting in a flooding state in which the operation of the distillation column was not smooth. Further, it was difficult to keep the height from the bottom of the decomposition tank to the surface of the waste liquid constant, and the operation mode had to be changed by a semi-batch method in which the waste liquid was not discharged from the decomposition tank until the height became a certain level. As a result, it took a long time to reach the steady state.

Example 1: Decomposition of Michael adduct and recovery of acrylic acid

In the same manner as in Comparative Example 1, in the decomposition tank for the start-up of the reactive distillation column, the waste liquid obtained in the reactive distillation apparatus of another process as the initial reaction liquid and the waste liquid mixed in the volume ratio of the lower solution 2: . The waste oil contained 2.1% by weight of acrylic acid, 24.7% by weight of acrylic acid dimer and 5.2% by weight of maleic acid. The viscosity at 100 ° C was 51 cP. The lower solution contained 44.4% by weight of acrylic acid, 28.4 wt% and maleic acid 6.1 wt%, and the viscosity at 100 DEG C was 2 cP.

Then, the amount of heat was gradually supplied to the heat exchanger so that the height from the bottom of the decomposition tank to the surface of the waste liquid was not reduced, and the difference between the internal temperature of the decomposition tank and the internal temperature of the heat exchanger was maintained at about 5 ± 1 ° C.

In Example 1, the height from the bottom of the decomposition tank to the surface of the waste liquid was not abruptly decreased, and the internal temperature of the decomposition tank stably reached the target temperature (decomposition temperature of Michael adduct) with the gradual concentration of the waste liquid. Thus, stable operation was possible and the time to reach the steady state was short.

Example 2: Decomposition of Michael adduct and recovery of acrylic acid

In the same manner as in Comparative Example 1, in the decomposition tank for the start-up of the reactive distillation column, the waste liquid obtained in the reactive distillation apparatus of another process as the initial reaction liquid and the waste liquid mixed in the volume ratio of the lower solution 1: . The waste oil contained 2.1% by weight of acrylic acid, 24.7% by weight of acrylic acid dimer and 5.2% by weight of maleic acid. The viscosity at 100 ° C was 51 cP. The lower solution contained 44.4% by weight of acrylic acid, 28.4 wt% and maleic acid 6.1 wt%, and the viscosity at 100 DEG C was 2 cP.

Then, the amount of heat was gradually supplied to the heat exchanger so that the height from the bottom of the decomposition tank to the surface of the waste liquid was not reduced, and the difference between the internal temperature of the decomposition tank and the internal temperature of the heat exchanger was maintained to be about 4 ± 1 ° C.

As in Example 1, in Example 2, the height from the bottom of the decomposition tank to the surface of the waste liquid was not abruptly decreased, and as the waste liquid was gradually concentrated, the internal temperature of the decomposition tank was steadily decreased to the target temperature ). Thus, stable operation was possible and the time to reach the steady state was short.

1 to 3 and 5 to 7: transfer line
100: High boiling point material separation tower
300: Reaction distillation tower
400: heat exchanger
500: waste oil discharge pump
600: condenser

Claims (6)

A process for producing (meth) acrylic acid using a reactive distillation apparatus comprising a reactive distillation column having a structure in which a decomposition reaction of a Michael adduct takes place and a distillation column where distillation of a decomposition product takes place, and a heat exchanger as a heat source thereof,
A waste liquid having a viscosity between the lower liquid of the high boiling point material separating column and the waste oil discharged from the reactive distillation apparatus is supplied to the reactive distillation apparatus as waste liquid discharged from at least one of the production process of the (meth) acrylic acid and the recovery process, step; And
And supplying heat such that the difference between the temperature of the waste liquid contained in the decomposition tank and the internal temperature of the heat exchanger is constant.
The process for producing (meth) acrylic acid according to claim 1, wherein a waste liquid having a viscosity of 5 to 40 cP is supplied to the reactive distillation apparatus at 100 占 폚.
The method for producing (meth) acrylic acid according to claim 1, wherein a mixture of the lower liquid of the high boiling point material separating column and the waste oil discharged from the reactive distillation apparatus is used as the waste liquid to be supplied to the reactive distillation apparatus.
The process according to claim 3, wherein the lower liquid of the high boiling point material separating column and the waste oil discharged from the reactive distillation apparatus are mixed and supplied to the reactive distillation apparatus at a volume ratio of 0.1: 1 to 5: 1, Gt;
The method as claimed in claim 1, wherein in the step of supplying the heat, the difference (? T = | T1 - T2 |) between the temperature (T1) of the waste liquid contained in the decomposition tank and the internal temperature (Meth) acrylic acid.
The method according to claim 1, wherein, in the step of supplying the heat, the amount of change (? T = | T1 - T2 |) between the temperature (T1) of the waste liquid contained in the decomposition tank and the internal temperature (Meth) acrylic acid.

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