Method for obtaining (meth)acrylic acid

FIELD: chemistry.

SUBSTANCE: invention concerns improved method for obtaining (meth)acrylic acid involving steam phase catalytic oxidation of propylene, propane or isobutylene for production of reaction mix, absorption of oxidised reaction product in water to obtain water solution containing (meth)acrylic acid, concentration of water solution in the presence of azeotropic agent and distillation of obtained (meth)acrylic acid in distillation column to obtaining purified (meth)acrylic acid. During operation of distillation column, including operation interruption and resumption, the column is washed with water, and afterwards azeotropic distillation is performed in the presence of azeotropic agent.

EFFECT: efficient and fast cleaning of distillation column with extraction of valuable substance.

5 cl, 5 dwg, 3 ex

 

The technical FIELD

The present invention relates to a method of purification of acrylic acid, methacrylic acid or their esters in the distillation. In particular, the present invention relates to a method of leaching during a suspend or resume operation of the distillation column, which is required at the time of the separation and purification by distillation of the crude acrylic acid, methacrylic acid or their esters obtained by vapor-phase catalytic oxidation of propylene, propane or isobutylene. Here and further in this document describing the present invention, acrylic acid and methacrylic acid in the General case can be called "(meth)acrylic acid". In addition, (meth)acrylic acid and its ester in the General case can be called "a derivative of (meth)acrylic acid".

The LEVEL of TECHNOLOGY

The distillation is a common method of extraction and purification of acrylic monomer, such as a derivative of (meth)acrylic acid. In recent years there has been developed a high-performance material nozzles, for example, for the purpose of improving the efficiency of separation in the distillation or subjected to increasing the processing amount, and in practice used in distillation columns in different processes. However, the derivative of the (meth)acrylic acid has a very high propensity for polymerization, and the formation of polymer in the distillation column was a serious problem in the distillation column commonly used type of plates, especially in highly Packed column.

As a way to prevent the formation of polymer derived (meth)acrylic acid has previously been known design improvement plates (for example, JP-A-2000-300903). In addition, they proposed a method of use of a specific inhibitor of polymerization (for example, JP-A-7-53449). However, it was difficult to withstand continuous operation for a long period of time, and required periodic inspection, cleaning, repair and the like, which require the suspension of the operation.

As this way of washing or repair of the proposed method, which includes flushing the basic solution such as sodium hydroxide solution or potassium hydroxide, followed by washing with a solvent (particularly preferably water) (for example, JP-A-2000-319223). In that case, if the derivative of (meth)acrylic acid is subjected to such processing, when using distillation columns, for security purposes, in conclusion, is usually carried out washing the inner space of the water in order to explore the distillation column during the pause function the project.

If at the time of resumption of operation after completion of the inspection, and the like in relation to the distillation column, rinsed with water as mentioned above, the water in the system will remain, then the time after a resume operation until the moment when the distillation column is stabilized in a stationary mode, will be increased, and will need to continue functioning in the transient mode of the processing mixture. It was found that the extension of this non-stationary regime is causing polymerization derived (meth)acrylic acid is polymerized substance.

Thus, the present invention is to provide a method for washing the distillation column for separation and purification of the crude derivative of (meth)acrylic acid. In particular, in the method of obtaining the derivative of (meth)acrylic acid is necessary to create an effective cleaning method of distillation columns for a short time and recovery of valuable substances in the use of the substance used in the method before and after distillation columns.

Description of the INVENTION

As a result of extensive research aimed at resolving the above problems, the inventors of the present invention have identified different facts, such the AK the following, that was the subject of the present invention:

(1) Blockage in the distillation column mainly produces acid polymer obtained by polymerization of a derivative of (meth)acrylic acid, and it will be easy to swell or dissolve under the action of alkaline water.

(2) To remove the alkaline component of effective water rinse.

(3) If water is present in the distillation column in large quantities, after resumption of the operation must undergo a long period of time before the operation will be carried out in the stationary operating mode.

(4) In the unstable period after the resumption of the functioning of the formation of polymer is significant.

(5) the formation of the polymer can be markedly suppressed in the removal of water from the distillation column.

(6) a Substance used in the method before or after distillation column, can be effectively used as a desiccant.

(7) If the alkaline component will remain, a derivative of (meth)acrylic acid may decompose.

That is the essence of the invention lies in the method of obtaining the derivative of (meth)acrylic acid, which comprises distilling derivative of (meth)acrylic acid in a distillation column to obtain a purified derivative (IU is)acrylic acid, characterized in that during the operation of distillation columns, including suspend and resume operation, the distillation column is washed with water and then conduct the flushing of the internal space with an organic solvent and/or azeotropic distillation in the presence of an organic solvent.

In addition, another entity of the present invention is the method of obtaining a (meth)acrylic acid, which comprises carrying out for propylene, propane or isobutylene vapor-phase catalytic oxidation to obtain the oxidized reaction mixture, the absorption of the oxidized reaction product in water to obtain an aqueous solution containing the (meth)acrylic acid, the concentration of the aqueous solution in the presence of an azeotropic agent and distillation of the obtained (meth)acrylic acid in a distillation column to obtain a purified (meth)acrylic acid, characterized in that during the operation of distillation columns, including suspend and resume operation, the distillation column is washed with water and after that carry out azeotropic distillation in the presence of an azeotropic agent.

In addition, another entity of the present invention is the method of obtaining a (meth)acrylic acid, which comprises carrying out for p is cut propane or isobutylene vapor-phase catalytic oxidation to obtain the oxidized reaction mixture, the absorption of the oxidized reaction product in water to obtain an aqueous solution containing the (meth)acrylic acid, the concentration of the aqueous solution in the presence of an azeotropic agent and distillation of the obtained (meth)acrylic acid in a distillation column to obtain a purified (meth)acrylic acid, characterized in that during the operation of distillation columns, including suspend and resume operation, the distillation column previously washed with water, then alkaline water and water and then conduct azeotropic distillation in the presence of an azeotropic agent.

BRIEF DESCRIPTION of DRAWINGS

Figure 1 is an example routing of a method of obtaining acrylic acid when used as educt propylene.

Figure 2 represents another example of the routing of a method of obtaining acrylic acid when used as educt propylene.

Figure 3 represents another example of the routing of a method of obtaining acrylic acid when used as educt propylene.

Figure 4 is an example of a technological ka is you method of producing acrylic ester.

Figure 5 is an example of distillation columns derived crude (meth)acrylic acid and related equipment.

Description legend

And: Column collection acrylic acid.

In: dehydration Column.

With Column separation of low-boiling component (column separation of acetic acid).

D: Column high boiling point component separation (column purification of acrylic acid).

E: the Reactor for the decomposition of the high-boiling component.

F: Distillation column, where in one column combined dehydration column b and column separation of low-boiling component (column separation of acetic acid) C.

G: desorption Column.

H: Column remove the high-boiling component.

To: Column extraction solvent.

L: the esterification Reactor.

M: a Column separation of acrylic acid.

N: a Reactor for the decomposition of the high-boiling component.

Q: Column extraction of alcohol.

P: Column alcohol extraction.

R: Column separation of low-boiling component.

S: Column purification of ester.

The BEST WAY of carrying out the INVENTION

The mixture to be processed by distillation in the present invention is acrylic acid, methacrylic acid or their esters, that is, derivatives of (meth)acrylic the acid. For example, can be mentioned acrylic acid, which is obtained in the vapor-phase catalytic oxidation of propylene in the presence of the composite oxide catalyst related to the type of Mo-Bi, obtaining acrolein, subsequent vapor-phase catalytic oxidation in the presence of the composite oxide catalyst related to the type of Mo-V. In this case, the method may be a two-step reaction, where prior to the oxidation reaction of propylene to obtain mainly acrolein and the subsequent oxidation reaction of acrolein to obtain, mainly acrylic acid is carried out in separate reactors, respectively, either one-step reaction where the catalyst prior to the reaction and the catalyst for subsequent reactions simultaneously placed in a reactor for carrying out reactions. In addition, the present invention can also be used in a method of producing acrylic acid which can be obtained in the vapor-phase oxidation of propane using a composite oxide catalyst related to the type of Mo-V-Te, or a composite oxide catalyst related to the type of Mo-V-Sb. In addition, there can be mentioned acrylic ester or methacrylic acid, which can be obtained at the stage of receipt of such ether when used as a source of washes the VA (meth)acrylic acid.

Acrylic ester, for example, may be a methyl acrylate, an acrylate, butyl acrylate, isobutylamine, tert-butyl acrylate, 2-ethyl hexyl acrylate, 2-hydroxyethylacrylate, 2-hydroxypropylmethacrylate or methoxyethylamine. As methacrylic acid, you can also mention this connection.

The reaction mixture of the above-mentioned vapor-phase catalytic oxidation absorb in water to obtain an aqueous solution containing the (meth)acrylic acid. This aqueous solution of the concentrate in the presence of an azeotropic agent such as alcohol, ketone or aromatic hydrocarbon, in the result, it is possible to obtain the crude (meth)acrylic acid. As the azeotropic agent is particularly preferred methyl ethyl ketone, methyl isobutyl ketone, benzene, toluene or isopropylacetate.

Such crude derivatives of (meth)acrylic acid include high-boiling impurities, such as dimer and trimer (meth)acrylic acid, esterified products of maleic anhydride, benzaldehyde, β-hydroxypropionic acid, esters β-hydroxypropionic acid, β-alkoxyamino acid and esters β-alkoxyamino acid. Content derived (meth)acrylic acid fed to a distillation column in the present invention is usually at least 2% (wt.), preferably, at least 5% (wt.), more preferably, at least 10% (wt.). Despite the low concentration of the derivative of (meth)acrylic acid such impurities and (or) mixed composition is formed along with water, often have an extremely high tendency to polymerization conditions of temperature and pressure existing in the column for processing by distillation. However, the phenomenon of polymerization, probably takes place at the initial stage of carrying out distillation. Accordingly, the range of use of the present invention is wide, and the present invention provides significant results even when processing technological solution containing a small amount of a derivative of (meth)acrylic acid.

That is, the distillation derivative of (meth)acrylic acid in the present invention is usually a stage (purification step) to obtain the derivative of (meth)acrylic acid of high purity, but it is not limited to this option, and it can also be applied at the stage of purification of the extract of a mixture containing derivative of (meth)acrylic acid component enriched derivative of (meth)acrylic acid.

Hereinafter the present invention will be described with reference to the drawings.

Figure 1 is an example of a technology is practical map method of producing acrylic acid using as starting substances propylene. The symbols and numbers on the figure represent the following :

And: Column collection acrylic acid.

In: dehydration Column.

With Column separation of low-boiling component (column separation of acetic acid).

D: Column high boiling point component separation (column purification of acrylic acid).

E: the Reactor for the decomposition of the high-boiling component.

From 1 to 3: supply Line from the wash solution or an inhibitor of polymerization.

4: Gas oxidation reactions containing acrylic acid.

5: Aqueous solution of acrylic acid.

11: Crude acrylic acid.

15: production Line of acrylic acid.

19: production Line of acrylic acid of high purity.

Gas containing acrylic acid obtained by vapor-phase catalytic oxidation of propylene and/or acrolein when using a gas containing molecular oxygen admitted through line 4 into a column of a collection of acrylic acid and injected into contact with water to obtain an aqueous solution of acrylic acid.

After that, an aqueous solution of acrylic acid is fed to the dehydration column C. In the dehydration column are filing azeotropic agent, the azeotropic mixture containing water and the azeotropic agent, the distillation is withdrawn from the top of the column and acrylic acid containing acetic acid, is obtained from the cube to the Onna. Azeotropic mixture containing water and the azeotropic agent, the distillation selected from the top of the dehydration column, let into storage tank 10, where it is separated into the organic phase formed mainly azeotropic agent, and the aqueous phase is formed mainly by water. The organic phase is sent for recycling in the dehydration column C. on the other hand, the aqueous phase is sent for recycling through line 7 in column collection acrylic acid and used as a water columns collection, which is injected into contact with the gas containing acrylic acid, thereby providing the opportunity for its effective use. Re-supply of water is produced through the line 8, as required by the case.

The crude acrylic acid selected from Cuba dehydration of the column through line 11, let the column, separating a low-boiling component column separation of acetic acid) to remove residual acetic acid. Here acetic acid is isolated and removed from the top of the column through line 12 and 13. Acetic acid in line 13 contains acrylic acid, and therefore, part or all of the amount can sometimes be returned to the process. On the other hand, acrylic acid, essentially not containing acetic acid, is obtained from the cube of the column through line 14. This acrylic acid is characterized by very in the high purity, and it can be used as such as a substance to obtain the ester of acrylic acid, and in some cases will get it as a product through line 15. Acrylic acid of high purity can be obtained as a result of its entry through the line 16 to the column separating the high-boiling component column purification of acrylic acid) D for isolation and removal through line 17 high-boiling substances and to get through the lines 18 and 19 of acrylic acid of high purity. High-boiling substances line 17 serves in the reactor for the decomposition of high boiling point component of E, resulting in part of the extract in the form of acrylic acid, and fed into the process via line 20. High-boiling substances are separated and removed through line 21.

Figure 2 represents another example routings method of producing acrylic acid.

In this way the dehydration column b and column separation of low-boiling component (column separation of acetic acid) figure 1 combined in one column, i.e. the distillation column F, resulting in flows of substances basically the same as in figure 1.

Figure 3 represents another example routings method of producing acrylic acid.

And: Column collection acrylic acid.

G: desorption Column.

D: Column compartments wysokosc pedego component (column purification of acrylic acid).

H: Column remove the high-boiling component.

To: Column extraction solvent.

From 1 to 3: supply Line from the wash solution or an inhibitor of polymerization.

4: Gas oxidation reactions containing acrylic acid.

5: a Solution containing acrylic acid.

11: Crude acrylic acid.

19: production Line of acrylic acid of high purity.

Gas containing acrylic acid obtained by vapor-phase catalytic oxidation of propylene and/or acrolein when using a gas containing molecular oxygen admitted through line 4 into a column of a collection of acrylic acid and injected into contact with the solvent to obtain a solution containing acrylic acid.

After that, the solution containing acrylic acid, is fed into the desorption column G. In the desorption column G through line 10 serves gas (gas line 6 released from the top of the column collection of acrylic acid And or gas after oxidation and removal of organic substances in the gas line 6), water and acetic acid in the distillation is withdrawn from the top of the column and acrylic acid containing solvent selected from Cuba columns. Water and acetic acid, selected by distillation from the top of the desorption column G, let the column, collecting the acrylic acid And water and acetic acid in conclusion released from the top is Ronny collection acrylic acid A. In order to obtain acrylic acid of high purity acrylic acid from the cube to the desorption column G is injected through the line 11 in column separating the high-boiling component column purification of acrylic acid) (D, resulting in a high-boiling components are separated and removed through line 14, and acrylic acid of high purity can be obtained through the line 19. Specifically, the high-boiling substances in line 14 are maleic anhydride, benzaldehyde, and the like, and they are served in the column remove the high-boiling component is N, then the data of the high-boiling substances released through line 21. The solvent of the cube of the column through line 17 is fed to the column extraction solvent K. From the top of the column the extracted solvent is returned through line 7 in column collection acrylic acid A. More high-boiling substances are separated and removed from the cube of the column through line 22.

Figure 4 is an example routing of a method of obtaining a complex ester of acrylic acid. The symbols and numbers on the figure represent the following :

L: the esterification Reactor.

M: a Column separation of acrylic acid.

N: a Reactor for the decomposition of the high-boiling component.

Q: Column extraction of alcohol.

P: Column alcohol extraction.

R: Column separation of low-boiling component.

S: Column clear and sophisticated air.

31: the supply Line of acrylic acid.

32: Line supply of alcohol.

33: a Mixture of the esterification reaction.

35: Acrylic acid, sent for recycling.

37: a production Line of high-boiling impurities.

39: production Line of the crude complex ester of acrylic acid.

41: the water supply Line.

42: Line extracted alcohol/water.

46: Line of product release in the form of an ester of acrylic acid.

In the esterification reactor L serves acrylic acid through line 31, the alcohol through line 32 sent for recycling acrylic acid through line 35 and sent to recycling the alcohol through line 48, respectively. In the esterification reactor L is placed a catalyst, such as a strongly acidic ion-exchange resin. A mixture of the esterification reaction, containing the obtained ester, unreacted acrylic acid, unreacted alcohol and water received through line 33 is selected and fed to the column separation of acrylic acid M From the column separation of acrylic acid M through the line 34 are selected cubic liquid essentially containing all of the amount of unreacted acrylic acid, and through line 35 served in the esterification reactor L as the fluid sent for recycling.

Part of the bottom liquid is fed through line 36 to the reactor for the decomposition of the high-boiling component N and valuable substance, the resulting degradation of the texts, sent to the process through line 40 for recycling. Point in the process where it is sent back for recycling varies depending on process conditions. High-boiling impurities such as oligomers, will be removed from the system through line 37. In addition, through the line 38 from the top of the column separation of acrylic acid M by distillation of selected received ester, unreacted alcohol and water received. Part of the distillate will be sent for recycling in the column separation of acrylic acid M as a reflux liquid, and the remainder will be fed through line 39 to column extraction Q.

Through the line 41 to supply water for the extraction of alcohol and water containing the extracted alcohol will be served in the column extraction of ethanol R through the line 42. The extracted alcohol sent for recycling through line 48 into the esterification reactor.

Through the line 43 of the crude ester of acrylic acid is fed to the column separation of low-boiling component R. low-boiling compounds containing ester of acrylic acid, taken through the line 44 and sent to the process for recycling. Point in the process where they are sent for recycling varies depending on process conditions. The crude ester of acrylic acid after removal of low-boiling substances will be fed through line 45 to column purification of the product, are is it an acrylic ester S. From the top of the column through line 46 receive ester of acrylic acid of high purity. From the cube of the column through line 47 will produce a liquid containing some high-boiling substances, and send it to a process for recycling. The location of the point at which carry out recycling varies depending on process conditions.

Figure 5 is an example of a distillation column for crude acrylic monomer and related equipment. Numbers on the figure represent the following :

51: Distillation column.

52: a Layer of material of the nozzle or plate distillation columns, or a combination of the material of the nozzle and plate distillation columns.

53: supply Line inhibition air.

54: a heat Exchanger for cooling the gas in the top of the column.

55: a heat Exchanger for cooling the exhaust gas.

56: Receiver phlegmy.

57: Allocator.

58: Boiler (heat exchanger for heating).

59: Reservoir for liquid containing leaching solution or a polymerization inhibitor.

60: supply Line acrylic monomer (raw).

61: supply Line from the wash solution or an inhibitor of polymerization.

62: Line release fluid from the top of the column.

63: Line release fluid from the cube column.

64: production Line of the exhaust gas.

Line 53 and line 61 b can the be installed in one or multiple locations on different parts of the distillation depending on the conditions in the distillation column.

Distillation column, that can be applied to the present invention includes all types of distilling, where derivatives of (meth)acrylic acid involved in the equilibrium vapor-liquid, and for any it entails carrying out an operation such as separation, preconcentration, extraction, purification and the like. For example, it correspond to the dehydration column B, column separation of low-boiling component (column separation of acetic acid) and the column separating the high-boiling component column purification of acrylic acid) D, shown in figure 1. Similarly it correspond to desorption column G column separating the high-boiling component column purification of acrylic acid) D, column remove the high-boiling component N and column extraction solvent, is shown in figure 3, and the column separation of acrylic acid M, Colonna alcohol extraction R, column separation of low-boiling component R and column purification of ester S, shown in figure 4, and the distillation column 51, shown in figure 5.

Distillation column, for example, can be the column / tube sheet plates, bubble column, Packed column, or a combination thereof (such as a combination of columns with / tube sheet plate and Packed columns, see figure 5), and any of them m which can be used in the present invention, regardless of the presence or absence of the overflow gate or peritonei tube. Concrete plates, for example, can be the cap plate, plate / tube sheet, bubble plates, plates with ultra-fast evaporation, plates with a maximum flow or double-flow plates.

As for the material of the nozzle, in addition to commonly used nozzle, for example, columnar, cylindrical, truck types, having a spherical, cubic or pyramidal shape, as a highly effective material nozzles in recent years became commercially available material nozzle having a special form and the form of which is correct or incorrect. The preferred possibility of using such material in the present invention. In the case of the material of the nozzle proper forms such commercial products, for example, can be a material of the nozzle of the correct form of a mesh type, such as Sulzer Packing (made by Sulzer Brothers Company, Sumitomo Sulzer Packing (manufactured by Sumitomo Heavy Industries, Ltd.) or Tecknopack (manufactured by Mitsui & Co., Ltd.), or MC Pack (manufactured by Mitsubishi Chemical Engineering Corporation), the material of the nozzle of the correct form sheet type, such as Mellapack (manufactured by Sumitomo Heavy Industries, Ltd.), Tecknopack (manufactured by Mitsui & Co., Ltd.), or MC Pack (manufactured by Mitsubishi Chemical Engineering Corporation), or the material of the nozzle of the correct form resh is tatoga type, such as Flexigrid (manufactured by Koch Company). As other materials of the nozzles can be mentioned, for example, GEMPAK (manufactured by Glitsch Company), Montz Pack (manufactured by Montz Company), Goodroll Packing (manufactured by Tokyo Tokushu Kanaami K. K.), Honeycomb Pack (manufactured by NGK Insulators, Ltd.), either Impulse Packing (manufactured by Nagaoka Corporation).

In addition, as a material of the nozzle of irregular shape, for example, we can mention the ring process, the ring of the Pall (manufactured by BASF), Cascade Miniring (manufactured by Mass Transfer Company), IMTP (manufactured by Norton Company), Intalox Saddle (manufactured by Norton Company), Tellerette (manufactured by Nittetsu Chemical Engineering Ltd.) or Flexiring (manufactured by JGC Corporation).

The characteristic of the present invention is that during the washing of the polymer formed deposits and accumulated in the distillation column after the operation of distillation columns to obtain the derivative of (meth)acrylic acid within a predefined period of time (1) after washing with water is conducted (2) flushing of the internal space downward flow of organic solvent and/or (3) azeotropic distillation in the presence of an organic solvent. Before (2) and/or (3) can be (4) leaching of alkaline water, and similar leaching alkaline in the th effective for dissolving the polymer. If you spend washing alkaline water, it is important then to further ensure (5) stage of leaching water. Next, a method will be described sequentially.

(1) water Rinse.

The primary use of water is the leaching derivative of (meth)acrylic acid remaining in the column. Water is fed into the receiver phlegmy distillation column through line phlegmy served at the top of the distillation column, or it can be fed through line phlegmy directly to a distillation column. Water flows down to Cuba, rinsing the inner space of the column. To ensure the ability to achieve sufficient contact of water with the polymer in the column, the wall of the column, the material of the nozzle in the column and the like, the water supplied from the top of the column and flowing down to the cube of the column may be made from the top of the column repeatedly. In the case of repeated filing preferably using water after separation and removal of solid content in the flowing water down, for example, with the use of a strainer of the pump. Together with the flow from the top of the column can be made and additional supply from the stage of presentation.

When installed in the upper part of the Packed column dispenser (dispenser of liquid or distributing fluid nozzle), it is preferable to use the method of supplying water through a dispenser.

The rinsing water can usually be carried out at a temperature in the range from 10 to 100°for 30-360 minutes. The amount of water supplied can also depend on the degree of blockage or plaque formation in the column, but it usually is in the range from approximately 0.5 to 5 m3/h at 1 m2the cross sectional area of the distillation column (if water is used repeatedly, the mean integral value).

In the washing solution thus extracted in Cuba columns, contains a valuable substance (such as acrylic acid or acrylic ester), which remained distillation column directly after a pause. Accordingly, the washing liquor at some point translate into the tank and stored therein, and upon resumption of the operation of distillation columns it will be sent for recycling in the proper position in the process (such as dehydration column In figure 1), whereas the composition of the leaching solution.

(2) Rinsing the inner space of the downward flux of organic solvent.

Rinse the inner space of the organic solvent is intended to replace the water remaining in the column. The organic solvent used for washing the interior space, nab is emer, can be derived (meth)acrylic acid, methanol, ethanol, butanol, benzene, toluene, methyl ethyl ketone, methyl isobutyl ketone, methyl-n-butylketone, isopropylacetate, diphenyl ether, biphenyl, or their mixture.

As the organic solvent of the present invention also can be used effectively not only the above-mentioned solvent of high purity, but also the substance related to the type of organic solvent containing various azeotropic agents obtained in the process either before or after distillation columns. For example, you can use the azeotropic agent, used for concentrating an aqueous solution containing the (meth)acrylic acid, the crude (meth)acrylic acid, obtained as a result of this concentration, derived purified (meth)acrylic acid (product), received prior to the suspension of the operation of the distillation column, or a product that does not meet specifications, extracted during suspension operation.

The water content of the used organic solvent is preferably at most 2% (wt.), more preferably, at most 1% (wt.). For example, a product that represents a derivative of (meth)acrylic acid, usually characterized by water content, the more the, equal to 0.2% (wt.), and, accordingly, this product can be used as such. Specifically, in the above-mentioned process maps it is preferably used for C and D in figure 1, and D on figure 2, and S in figure 3.

The way to replace the water in the flushing of the internal space has no particular restrictions. For example, it is preferable that the organic solvent would afford to the receiver phlegmy distillation column through line phlegmy would afford in the upper part of the distillation column. Organic solvent which flows down to Cuba, coming into contact with the wall of the column, the material nozzles, plates and the like to include in your composition, water can be extracted in the extraction system, but in order to carry out the removal of water sufficiently, it is preferable to send it for recycling to the top of a column or at the stage of presenting the material. If the water content of the organic solvent to be sent to recycling to exceed 2% (wt.), the dewatering effect will be greatly reduced, and such an organic solvent system selected. Rinse the inner space of the organic solvent is usually carried out at a temperature at most equal to 50°C, preferably in the range from 0 to 40°C.

The amount of organic the second solvent can usually be in the range from 0.5 to 5 m 3/h at 1 m2the cross sectional area of the distillation column. In the case where the removal of residual water from the structure of the internal space of the distillation column passes difficult, consumption, optional can be increased.

(3) Purification of azeotropic distillation in the presence of an organic solvent.

In the present invention, in order to remove the water present in the column after washing with water, perform cleaning azeotropic distillation in the presence of an organic solvent, which can be one of azeotropic distillation with water. This stage is designed to remove water, but in the case when the column remains a small amount of polymer, at the same time you can spend and its dissolution and destruction. Water distillation is withdrawn from the top, and the dissolved polymer and the like will take away from the cube.

Useful organic solvents include alcohols, such as methanol, ethanol and butyl alcohol, ketones such as methyl ethyl ketone, methyl-n-butylketone and methyl isobutyl ketone, aromatic hydrocarbons such as benzene, toluene and xylene, and the above-mentioned derivatives of (meth)acrylic acid. These organic solvents can be used in combination as a mixture.

Such an organic solvent serves on the stage of filing of the original solution DL the distillation or columns in the cube, and it will be processed under the conditions of distillation under the action of heat, the source of which is the boiler. In such conditions, use the following: temperature of top of the column is preferably in the range from 20 to 80°and the pressure of the top of the column is preferably in the range from 0.5 to 120 kPa. The water content of the organic solvent withstand preferably equal to at most 2% (wt.), more preferably, at most 1% (wt.), in the result, the efficiency will be excellent.

(4) Rinsing alkaline water.

In the present invention, the leaching of alkaline water is not a significant stage. However, because it can dissolve the acid polymer and to increase the washing effect. Accordingly, it is not necessary, you can include as the previous stage and/or the subsequent stage with respect to leaching by water. In that case, if you include the leaching of alkaline water, the distillation operation will resume after the stage of washing with water and the stage of dehydration, following behind her.

As alkaline water can be used an aqueous solution, for example, potassium hydroxide, sodium hydroxide or sodium carbonate. As for concentration, typically use a concentration in the range from 1 to 25% (wt.). In addition, you may use the use of an aqueous solution of ammonia, as for concentration, typically use a concentration in the range from 1 to 25% (wt.), preferably in the range from 1 to 10% (wt.). If the concentration is below the above range, the washing efficiency will have a tendency to deteriorate, and if it exceeds the above range, the heat of reaction with the acid component remaining in the column will tend to increase, which will result in the possible formation of a new polymer.

Alkaline water can be fed into the receiver phlegmy distillation column through line phlegmy feeding in the top of the distillation column, or through the line of phlegmy can be fed directly to a distillation column. Alkaline water flows down to the cube, causing swelling and dissolution of the polymer in the inner space. To ensure the ability to achieve sufficient contact of alkaline water with the polymer in the interior space, the wall of the column, the material of the nozzle in the column and the like, alkaline water supplied from the top and flowing down to the cube may be made from the top of the column repeatedly. In the case of repeated filing preferably using alkaline water after separation and removal of solid matter contained in the flowing down of alkaline water, for example, when using a mesh filter is Asosa. Together with the flow from the top of the column can be made and additional supply from the stage of raw material supply.

When installed in the upper part of the Packed column dispenser (dispenser of liquid or distributing fluid nozzle), it is preferable to use a method of supplying alkaline water through a dispenser.

Leaching alkaline water can usually be carried out at a temperature in the range from 10 to 100°for 30-360 minutes. The amount of alkaline water may also depend on the degree of blockage or plaque formation in the column, but usually it is preferably in the range from approximately 0.5 to 5 m3/h at 1 m2the cross sectional area of the distillation column (if alkaline water is used repeatedly, the mean integral value).

(5) water Rinse.

In the case when conducting the above-mentioned leaching alkaline water, additionally it is essential to conduct washing with water to remove residual alkali. Method of leaching water in this case is the same as (1) water rinse.

The water content remaining in the column as a result of washing the inner space of the downward flux of organic solvent or cleaning azeotropic distillation in the presence of the body of the ical solvent, usually equal to, at most, 1% (wt.), preferably at most 0.5 percent (wt.), more preferably essentially 0. Thus, upon resumption of the operation of distillation will quickly become possible to carry out the distillation in accordance with the technical specifications. If water remains, to achieve a state corresponding to the technical conditions will often be a long period of time, about 30 hours.

During the above-mentioned purification azeotropic distillation can be feed a small amount of polymerization inhibitor. Such a polymerization inhibitor (which can also be called an agent suppressing polymerization agent inhibiting polymerization agent of the termination of the polymerization or agent that reduces the rate of polymerization), for example, can be phenolic compounds such as hydroquinone, metochion (methoxyhydroquinone), pyragollole, catechin or resorcinol; N-oxylene connection, such as nitroxide tertiary butyl, 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl, 2,2,6,6-tetramethylpiperidine-1-oxyl, 2,2,6,6-tetramethylpiperidine, 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxy or 4,4',4"-Tris(2,2,6,6-tetramethylpiperidinyloxy)hospit; derived fenotiazina, such as phenothiazines, bis(α-methylbenzyl)phenothiazines, 3,7-dioctylphthalate or bis(α,α'dime is ylbenzyl)phenothiazines; the connection of copper, such as copper chloride (II), copper acetate, copper carbonate, copper acrylate, copper dimethyldithiocarbamate, copper diethyldithiocarbamate, dibutyldithiocarbamate copper or copper salicylate; a connection representing a salt of manganese, such as manganese acetate; phenylenediamine, such as p-phenylenediamine; a nitroso compound such as N-nitrosodiphenylamine; urea such as urea; or thiourea, such as thiourea. These compounds can be used individually or in combination as a mixture of two or more components selected from them.

After completion of the washing operation to resume the operation of distillation serves prescribed source solution to distillation containing the crude derivative of (meth)acrylic acid. This distillation can be done in a continuous distillation or periodic distillation. Operating conditions for distillation does not necessarily determine, taking into account the types or content of impurities contained in the crude derivative of (meth)acrylic acid, and the like, and a special limitation is imposed. Typically, the distillation is carried out at a temperature of the top of the column in the range from 20 to 80°at a temperature in the cube columns in the range from 60 to 120°and when the pressure of the top of the column in the range from about 0.5 to 120 kPa.

Hereinafter the present invention will be described more in detail with reference to examples. However, it should be understood that the present invention is not limited to such examples, if not going beyond it.

EXAMPLE 1

After exploring the inner space of the pillar separating the high-boiling component column purification of acrylic acid) D in the figure 1, the operation of which has been suspended for periodic inspection, conducted an operation to resume functioning. After the inspection of the internal space of the column separating the high-boiling component D internal space is washed with water to remove residue formed during the operation.

Column separation of high-boiling component consisted of a stainless steel (SUS316) distillation column, inner diameter of which was equal to 1100 mm and a height of 20000 mm, and which had 21 / tube sheet plate, and when using such columns were in the distillation of the crude acrylic acid. Before conducting the distillation in the column separating the high-boiling component through the top gave 1000 kg of product, which represents acrylic acid, containing 0.03% (wt.) water applied in the receiver phlegmy 56. Filed liquid flowed down to Cuba, and the liquid, with brunnow in Cuba, was released from a bottom part of the column. The water content of the produced acrylic acid was 3% (wt.).

Therefore, in the receiver phlegmy 56 again gave 1000 kg of the same product that represents acrylic acid, and held a similar operation cleaning and replacement. The water content of acrylic acid, released from the cube was 0.2% (wt.). Through the supply line of the original substance 60 at a flow rate of 1300 kg/h gave a mixture containing 98,5% (wt.) acrylic acid as a crude acrylic monomer, of 0.3% (wt.) maleic acid, and 0.2% (wt.) dimer of acrylic acid, of 0.02% (wt.) water and other high-boiling substances. In addition, from the reservoir 59 to the liquid containing the polymerization inhibitor, was applied fluid representing a solution of acrylic acid 8% (wt.) methanone and 1% (wt.) fenotiazina, at a cost of 34 kg/h and 31 kg/h, respectively. Brought heat from the heat source and the regulated pressure in the internal space and the like, and after about 5 hours of operation passed in stationary mode when the pressure of the top of the column of 2.8 kPa, and the pressure in the cube of 8.4 kPa, at a temperature of the top of the column 53°and at a temperature in the cube 78°C. From the top of the column was obtained acrylic acid of high purity with a water content of 0.02% (wt.) and purity at least equal the th 99,8% (wt.). As for operation, it was possible continuous operation for 1 year.

COMPARATIVE EXAMPLE 1

The distillation is resumed in the same manner as in example 1, except that the substitution in the internal space of acrylic acid as in example 1 was omitted. In the acrylic acid obtained from the top of the column in the result of the resumption of operation, the water content was 0.7% (wt.). The water content gradually decreased, and in order that the water content would be equal to 0.02% (wt.), required approximately 36 hours. As the distillation continued under the excessive water content, the pressure in the cube distillation column was gradually increased, and after one month the pressure in the cube was equal to 18 kPa, which is why the operation was interrupted. Examination of the internal space found a large quantity of polymer.

EXAMPLE 2

After exploring the inner space of the column separation of low-boiling component R in the figure 4, the operation of which has been suspended for periodic inspection, conducted an operation to resume functioning. After the inspection of the internal space of the column separation of low-boiling component R of the internal space was doused with water to removed the I residue, formed during the operation.

Column separation of low-boiling component R was a stainless steel (SUS304) distillation column shown in figure 5, the inner diameter of which was equal to 1100 mm, and height - 26000 mm, and which had 36 / tube sheet plates (twin plate)installed inside, and when using such columns were in the distillation of the crude acrylate.

Before conducting the distillation in the column separation of low-boiling component through the top gave 800 kg of product, representing an acrylate with a water content of 0.002% (wt.), submitted to the receiver phlegmy 56. Filed liquid flowed down to Cuba, and the liquid collected in the bottom part of her was released. The water content of the produced acrylate was 3.6% (wt.).

Therefore, in the receiver phlegmy 56 again gave 1000 kg of the same product, representing acrylate, and held a similar operation cleaning and replacement. The water content of the acrylate released from Cuba, was 0.11% (wt.). Such an operation was repeated again, and as a result, the water content of the acrylate released from the cube, constituted 0.004% (wt.). At the rate of 6000 kg/h were feeding a mixture containing 97,4% (wt.) ethyl acrylate as the crude acrylic monomer, a 1.8% (wt.) water, and 0.4% (wt. acrylic acid, of 0.4% (wt.) ethanol and 0.1% (wt.) ethyl acetate. In addition, from the reservoir 59 to the liquid containing the polymerization inhibitor, has filed a liquid, a solution in ethanol 5% (wt.) hydroquinone, at a flow rate of 60 kg/h Brought the heat from the heat source and the regulated pressure in the internal space and the like, and after about 7 hours of operation passed in stationary mode when the pressure of the top of the column 62,7 kPa, and the pressure in the cube 72,7 kPa, at a temperature of column 76°and at a temperature in the cube 89°S. Of Cuba received acrylate with a water content of 0.001% (wt.) and purity at least equal to 99.1% (wt.). During operation the pressure difference between the top of the column and cube columns (here and further in this document called pressure difference) remained stable during operation, and it was possible continuous operation for one year.

COMPARATIVE EXAMPLE 2

The distillation is resumed in the same manner as in example 2, except that the substitution in the internal space acrylate as in example 2, was omitted. Originally acrylate, obtained from the cube, contained 3,1% (wt.) water. The water content gradually decreased, and in order that the water content would be equal to 0.001% (wt.), required priblizitelen is 53 hours. The distillation is continued under the excessive water content, resulting from the resumption of operation, the pressure in the cube distillation column was gradually increased, and after one month the pressure in the cube was equal to 82 kPa, which is why the operation was interrupted. Examination of the internal space found a large quantity of polymer.

EXAMPLE 3

After exploring the inner space of the pillar of dehydration In the figure 1, the operation of which has been suspended for periodic inspection, conducted an operation to resume functioning. After the inspection of the interior space of the pillar of dehydration In the inner space washed with water to remove residue formed during the operation.

Column dehydration was a stainless steel (SUS316L) distillation column, inner diameter of which was equal to 4000 mm and a height of 25000 mm and which had a 30 / tube sheet plates, and when using such columns were in the distillation of the crude acrylic acid.

Before conducting the distillation in the receiver phlegmy at the rate of 5000 kg/h was applied toluene, which is then through the top was applied to the column separating the high-boiling component. Filed liquid flowed down to ku is and columns, and after confirmation of the presence in Cuba of the surface of the liquid brought the heat from the heat source. From the top of the column produced obtained by distillation of toluene and water. After about 5 hours in the distillation of water has been received. During this period of the cube, nothing was released.

Through the supply line of the source materials at the rate of 7500 kg/h gave a mixture containing 60% (wt.) acrylic acid as a crude acrylic monomer, a 0.4% (wt.) maleic acid, 4% (wt.) acetic acid, 35% (wt.) water and other high-boiling substances. In addition, from the reservoir for the liquid containing the polymerization inhibitor, at a flow rate of 6 kg/h was applied to the liquid, a solution of acrylic acid and 0.6% (wt.) copper acetate and 4% (wt.) hydroquinone, and at a flow rate of 500 kg/h was applied to the liquid, a solution in toluene, 2% (wt.) fenotiazina. At the same time the supply of toluene from the receiver phlegmy stopped, and toluene, obtained by distillation from the top of the column returned in the form of phlegmy, trying to achieve balance for maintaining the liquid level in the receiver phlegmy, while part of his system was selected.

Brought heat from the heat source and the regulated pressure in the internal space and the like, and after about 6 hours funkcionirovanie is passed in stationary mode when the pressure of the top of the column of 15.9 kPa, when the pressure in the cube 22,7 kPa, at a temperature of the top of the column 46°and at a temperature in the cube 82°S. Of Cuba received acrylic acid with a water content of 0.01% (wt.) and purity at least equal to 74% (wt.). As for operation, it was possible continuous operation for one year.

COMPARATIVE EXAMPLE 3

The distillation is resumed in the same manner as in example 3, except that the initial distillation using toluene as in example 3 was omitted. Upon resumption of the functioning of the acrylic acid derived from a cube, contained 2% (wt.) water. The water content gradually decreased, and in order that the water content would be equal to 0.01% (wt.), required approximately 62 hours.

INDUSTRIAL APPLICABILITY

When using the method of the present invention can be easily carried out washing, distillation columns for the separation or purification derivative of (meth)acrylic acid. In particular, in the method of obtaining the derivative of (meth)acrylic acid possible the extraction of valuable substances and effective flushing of the distillation column with the use of a substance used in the method before or after distillation columns. In addition, when resuming the operation of distillation after washing will quickly become possible achievements is their mode of functioning, the relevant specifications.

The full contents of the description of Japanese patent application No. 2002-257275, the priority of which is claimed in this application in its entirety is incorporated herein by reference.

1. A method of obtaining a (meth)acrylic acid, including for propylene, propane or isobutylene vapor-phase catalytic oxidation to obtain the oxidized reaction mixture, the absorption of the oxidized reaction product in water to obtain an aqueous solution containing the (meth)acrylic acid, the concentration of the aqueous solution in the presence of an azeotropic agent and distillation of the obtained (meth)acrylic acid in a distillation column to obtain a purified (meth)acrylic acid, characterized in that during the operation of distillation columns, including suspend and resume operation, the distillation column is washed with water and then conduct azeotropic distillation in the presence of an azeotropic agent.

2. The method according to claim 1, in which the water content of the organic solvent is at most equal to 2 wt.%.

3. The method according to claim 1, wherein the organic solvent is a derivative of (meth)acrylic acid, methanol, ethanol, butanol, benzene, toluene, methyl ethyl ketone, methyl isobutyl ketone, methyl-n-butylketone, isopropylacetate, diphenil the initial ether, the biphenyl or their mixture.

4. The method according to claim 1, wherein the azeotropic distillation is carried out at a temperature of the top of the column in the range from 20 to 80°and when the pressure of the top of the column in the range from 0.5 to 120 kPa.

5. The method according to claim 1, wherein the azeotropic distillation is carried out in the presence of a polymerization inhibitor.



 

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Cleaning method // 2237652
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