JP2001151725A - Apparatus for mixing aldehyde-disposing agent and method for purifying acrylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for mixing an aldehyde disposing agent, a method for using the apparatus and a method for purifying acrylic acid. SOLUTION: This apparatus for mixing an aldehyde-disposing agent comprises a tube section having an inflow port of an acrylic acid-containing liquid obtained by a catalytic gas phase oxidation reaction and an inlet for feeding the aldehyde-disposing agent, a mixing section for mixing the acrylic acid-containing liquid with the aldehyde-disposing agent communicated and connected with the tube section a holdup section for the obtained mixture solution installed to be communicating with the mixing section and a discharge port of the mixture solution installed to the mixing section. Aldehydes included in the acrylic acid-containing liquid are efficiently removed by adding the aldehyde-disposing agent at a specific position and in a specific flow rate and holding up the mixture solution, thus, the amount of the aldehyde-disposing agent is decreased and a polymerization caused by adding the disposing agent is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aldehyde treating agent mixing apparatus for mixing an aldehyde treating agent in an acrylic acid-containing liquid and retaining the aldehyde treating agent for a predetermined time, a method of using the apparatus, and a method of purifying acrylic acid.

[0002]

2. Description of the Related Art A method for producing acrylic acid by a catalytic gas phase oxidation reaction is known as an industrial production method. However, in the production process, aldehydes such as furfural and benzaldehyde, and acetone and the like are used. Ketones are by-produced.

[0003] However, it is difficult to remove impurities, particularly furfural, in acrylic acid obtained by the above-mentioned catalytic gas phase oxidation reaction by ordinary distillation. If such impurities are used as a raw material of an acrylic acid polymer without removing such impurities, During the polymerization reaction, problems such as a delay in the reaction, a decrease in the degree of polymerization, and coloring of the polymer occur.

[0004] In order to solve such a problem of coexistence of aldehyde, a method of adding a hydrazine compound during distillation of acrylic acid has been proposed. The hydrazine compound may form a complex with the aldehyde or be decomposed to reduce the content to the ppm level when mixed with the aldehyde-containing acrylic acid and distilled.

For example, Japanese Unexamined Patent Publication (Kokai) No. 61-218556 discloses that an acrylic acid aqueous solution obtained by cooling and condensing an acrylic acid-containing gas is used to remove light-boiling substances by a distillation or a stripping operation. Acrylic acid is sequentially processed from an aqueous acid solution in an extraction step, a solvent separation step, a light-boiling substance separation step, a heavy substance separation step, and a redistillation purification step, and in separation and purification, an aqueous acrylic acid solution supplied to the extraction step or An aqueous bisulfite solution is added to the extract containing the extraction solvent and acrylic acid obtained from the step, and the mixture is subjected to a mixing treatment.At least one of a solvent separation step, a light-boiling point separation step, a heavy substance separation step, and a redistillation purification step is performed. A method of adding and mixing a hydrazine compound to an acrylic acid-containing solution in one step is disclosed.

However, according to the method described in the publication,
After adding and mixing an aqueous solution of bisulfite to an acrylic acid-containing solution and the like, it is necessary to separate the two layers, and the operation is complicated.

[0007] Japanese Patent Application Laid-Open No. 7-228548 discloses that acrylic acid obtained by adding a hydrazine compound and copper dithiocarbamate to acrylic acid obtained by a gas phase catalytic oxidation reaction is distilled at 100 ° C. or lower. A method for purifying an acid is disclosed.

However, in the method described in this publication, the polymerization of acrylic acid during distillation can be prevented by the addition of copper dithiocarbamate. However, the addition of copper dithiocarbamate increases the concentration of copper dithiocarbamate in the bottom liquid during distillation, thereby preventing corrosion of the apparatus. May cause.

Japanese Patent Application Laid-Open No. Hei 7-330659 discloses that a specific amine compound (Group A) is added to crude acrylic acid at a temperature of 25 to 100 ° C. during distillation, and another amine compound (B) is added from the top of the column. Group A) and the Group A amine and B
The mixing molar ratio of the group A amine is 0.1 to 2.0 of the group A amine.
Discloses that the group B amine is 0.01 to 1.0.

However, according to the method described in this publication, 2
It is necessary to use different types of amines, and when adding a group A amine, it is necessary to add at a temperature of 40 ° C. or more in order to reduce the generation of solids. It must be adjusted according to the amount of group amine added.

Generally, in order to achieve a low aldehyde level by removing a mixed aldehyde from an acrylic acid-containing solution, it is necessary to contact the aldehyde treating agent at a high level for a long time. On the other hand, the addition of an excess of the aldehyde treating agent may cause polymerization of acrylic acid during distillation. The formation of such a polymer not only causes a decrease in heat transfer performance due to adhesion to the heat transfer surface of the distillation column reboiler, but also may cause a reduction in the performance of the distillation column and blockage in the distillation column. . Accordingly, there is a demand for a method for producing acrylic acid which efficiently decomposes and removes aldehyde contained in an acrylic acid-containing solution obtained by a catalytic gas phase oxidation reaction and does not cause polymerization.

[0012]

The present inventors have studied in detail the method of adding an aldehyde-treating agent to an acrylic acid-containing solution, and as a result, uniformly mixed the acrylic acid-containing solution containing the aldehyde-treating agent for a predetermined time. When the aldehyde treatment agent is retained, the aldehyde treatment agent can be mixed very efficiently, and the effect of the aldehyde treatment agent is excellent, whereby the addition amount of the aldehyde treatment agent itself can be reduced and the polymerization of acrylic acid can be suppressed. The present invention has been completed.

That is, the above-mentioned problems are as described in the following (1) to (1).
0).

(1) A tubular portion having an inlet for the acrylic acid-containing liquid obtained by the catalytic gas phase oxidation reaction and an inlet for supplying an aldehyde treating agent, and the acrylic acid connected to and connected to the tubular portion A mixing part of the content liquid and the aldehyde treating agent,
And an aldehyde treating agent mixing device having a stagnant portion of the obtained mixed liquid provided in communication with the mixing portion and a discharge port of the mixed liquid provided in the stagnant portion.

(2) The aldehyde treating agent mixing apparatus according to the above (1), wherein the mixing section is a non-stirring type mixer.

(3) The aldehyde treating agent mixture according to the above (1) or (2), wherein the staying portion further has at least a part of an internal structure for making the flow of the mixture uniform. apparatus.

(4) The apparatus for mixing an aldehyde treating agent according to the above (3), wherein the internal structure is a baffle plate.

(5) Any one of the above (1) to (5), wherein the distance from the inlet to the inlet of the mixing section is 0.1 to 5 times the inner diameter of the tubular section. 3. The aldehyde treating agent mixing device according to item 1.

(6) The aldehyde treating agent mixing apparatus according to the above (5), wherein the inlet is an aldehyde treating agent adding nozzle protruding from the tubular portion.

(7) The aldehyde treating agent mixing apparatus according to the above (6), wherein the tip of the nozzle is opened to the inlet side of the acrylic acid-containing liquid or to the mixing section side.

(8) The maximum of the cross-sectional area of the flow passage of the stagnation portion is
2 to 5 of the cross-sectional area of the inlet of the acrylic acid-containing liquid in the tubular portion
The aldehyde treating agent mixing apparatus according to any one of (1) to (5), wherein the mixing ratio is 00 times.

(9) An acrylic acid refining tower and the above (1)
An acrylic acid refining device comprising the aldehyde treatment agent mixing device according to any one of (1) to (8).

(10) In a method for continuously purifying acrylic acid by adding an aldehyde treating agent to an acrylic acid-containing solution obtained by a catalytic gas phase oxidation reaction, the aldehyde treating agent is added at a rate of the acrylic acid-containing solution. A method for purifying acrylic acid, characterized in that it is added in an amount of 0.05 to 5.0 times the amount thereof, and is retained for 3 minutes to 150 hours, followed by distillation.

[0024]

DETAILED DESCRIPTION OF THE INVENTION A first aspect of the present invention is a tubular portion having an inlet for an acrylic acid-containing liquid obtained by a catalytic gas phase oxidation reaction and an inlet for supplying an aldehyde treating agent, and communicating with the tubular portion. A mixing part of the acrylic acid-containing liquid and the aldehyde treating agent, which is connected to the mixing part, a retention part of the obtained liquid mixture provided in communication with the mixing part, and a liquid mixture provided in the retention part And an outlet for the aldehyde treating agent. When the aldehyde treating agent is added to the acrylic acid-containing liquid by the apparatus of the present invention, both are sufficiently mixed in the mixing section,
In addition, since the aldehyde treating agent can react with the staying portion for a predetermined time, the effect of the aldehyde treating agent is effectively exhibited. Thus, when the acrylic acid-containing liquid is purified by the purification tower, the adhesion of the polymer to the purification device, heat exchanger, various pipes, and the like can be prevented. Hereinafter, the present invention will be described in detail.

Generally, acrylic acid can be produced by a catalytic gas phase oxidation reaction using propylene as a raw material and propane and / or acrolein as a raw material. Therefore, although depending on the raw material components, in addition to acrylic acid as a target substance, acid impurities such as acetic acid and maleic acid and aldehydes such as formaldehyde, acrolein, furfural and benzaldehyde are produced as by-products, depending on the raw material components. Generally, in order to remove these by-products, an acrylic acid-containing gas is led to an acrylic acid collecting tower, and is brought into contact with an acrylic acid collecting liquid to prepare an acrylic acid-containing liquid. Then, the obtained acrylic acid-containing liquid is purified. Purify in a tower. The present invention particularly, by adding the aldehyde treating agent to the acrylic acid-containing liquid before reaching the purification tower, and distilling the acrylic acid-containing liquid after the effect of the aldehyde treating agent is sufficiently exhibited, the aldehyde treating agent An object of the present invention is to reduce the amount of addition and suppress the polymerization of acrylic acid by the aldehyde treating agent. Therefore, the aldehyde treating agent mixing apparatus of the present invention is preferably installed between the acrylic acid collecting tower and the acrylic acid distillation tower in the acrylic acid production process. In particular, after separating the acrylic acid collecting solvent, more preferably after separating the contained low boiling impurities and high boiling impurities,
It is preferable to arrange the acrylic acid immediately before distillation purification.

The acrylic acid-containing liquid of the present invention refers to a liquid containing acrylic acid at an arbitrary concentration irrespective of the kind of the raw material gas in the catalytic gas phase oxidation reaction, and producing acrylic acid by the catalytic gas phase oxidation reaction. In this case, a liquid containing acrylic acid discharged from the reactor and a product containing acid impurities, aldehydes, and the like produced as by-products, or light-boiling impurities and / or high-boiling impurities from the liquid by an arbitrary method at an arbitrary concentration Means the liquid reduced by Therefore, even when the gas is discharged from the catalytic gas phase oxidation reactor in a gaseous state, even if it is not collected by the collecting liquid, it is condensed by heat release or the like, and if it becomes a liquid, it is included in the acrylic acid-containing liquid of the present invention. It is. Therefore, if acrylic acid is contained, the type of solvent contained therein is not particularly limited.

However, in consideration of the actual process of producing acrylic acid by applying the present invention, the acrylic acid-containing liquid of the present invention may be an acrylic acid-collecting liquid in the process of producing acrylic acid by a catalytic gas phase oxidation reaction. It is preferably an acrylic acid-containing liquid obtained by contacting with an aqueous solution. Various conditions such as the type and amount of the raw material gas, the reactor, and the inert gas and the molecular oxygen used in the raw material gas used in the catalytic gas phase oxidation reaction may be any known conditions. Is also good. Also, as the acrylic acid collecting liquid, any known liquid having a composition can be used, and an acrylic acid-containing liquid obtained under any known conditions, such as conditions for a collecting tower, can also be used.

Hereinafter, an embodiment of the aldehyde treating agent mixing apparatus of the present invention will be described with reference to FIG.

First, in the mixing apparatus of the present invention, there is a tubular portion (30) having an inlet (10) for an acrylic acid-containing liquid and an inlet (20) for supplying an aldehyde treating agent. A mixing part (40) for mixing the acrylic acid-containing liquid and the aldehyde treating agent to be connected, a retention part (50) for the obtained mixed liquid provided in communication with the mixing part (40), And a discharge port (60) for the mixed liquid provided in the retaining section (50).

An inlet (2) for supplying an aldehyde treating agent
0), for example, as shown in FIG.
An example of the nozzle for adding an aldehyde treating agent protruding in 0) can be given, but a so-called injector type supply port as shown in FIG. 2 may be used. In any case, the aldehyde treating agent is added to the acrylic acid-containing solution. 2, 3, 4, 5, 6, 7, 8, and 13
Indicates the flow direction of the mixture of the aldehyde treatment agent and the acrylic acid-containing liquid.

When such a protruding nozzle is used, the injection port of the aldehyde treating agent protruding into the tubular portion (30) is preferably located at a radially central portion of the tubular portion (30). . The mixing apparatus of the present invention is an acrylic acid supply pipe connecting an acrylic acid high-boiling distillation column, which is one of the processing facilities for the acrylic acid production process, and a distillation purification tower for acrylic acid, which is a continuous processing facility, for example. It is preferable to arrange them partially, and such pipes are usually formed in a cylindrical shape. In addition, an acrylic acid-containing solution is caused to flow in the pipe by a pump pressure to secure a full liquid. Therefore, if the tip of the protruding nozzle is located at the center in the radial direction, the flow of the acrylic acid-containing liquid supplied into the pipe facilitates mixing with the aldehyde treating agent. Further, the tubular portion (30) is not limited to a circular cross section as in a cylindrical shape as long as it is tubular, and may be a tubular material having a polygonal hollow such as a triangle or a quadrangle. Since the pipe for supplying the acrylic acid-containing solution in the acrylic acid production step is often cylindrical, the connection is easy if the inlet of the acrylic acid-containing solution in the tubular portion is circular. Similarly, if the outlet of the mixed liquid provided in the retaining portion is also circular, connection is easy.

As described above, at the injection port, it is preferable that the tip of the projecting nozzle reaches the center of the tubular portion. If the acid-containing liquid does not reach, an adjusting mechanism may be provided by a known technique so that the opening of the supply pipe reaches the center of the flowing acrylic acid-containing liquid.

When the injection port forms a protruding nozzle, the opening (21) of the protruding nozzle is, as shown in FIG. 3 or FIG. It is preferable to open to the side or the mixing section side. Here, having an opening on the mixing section side means having an opening in a direction substantially parallel to the flow of the acrylic acid-containing liquid as shown in FIG. 3, and opening on the inlet side of the acrylic acid-containing liquid. Having a means that, as shown in FIG. 4, the flow of the aldehyde treatment liquid from the tip opening of the protruding nozzle goes substantially in antiparallel with the flow of the acrylic acid-containing liquid. This is because if the aldehyde treatment liquid coming out of the opening (21) is substantially parallel or substantially antiparallel, the aldehyde treatment agent flows toward the mixing section along the flow of the acrylic acid-containing liquid, so that the mixing effect is improved. . On the other hand, as shown in FIG. 5, when an opening is provided at the tip of the protruding nozzle beyond substantially the center of the cross section of the tubular portion (30) in which the liquid is filled, the tubular portion opposed to the nozzle penetrating portion is provided. The aldehyde-treating agent supply stock solution may flow out near the inner wall or in contact with the inner wall, and the mixing of the aldehyde-treating solution and the acrylic acid-containing solution may be insufficient. However, even in such a case, the supply speed of the aldehyde-treating agent supplied thereto and the cross-sectional area of the nozzle are adjusted with respect to the flowing speed of the flowing acrylic acid-containing liquid, so that the aldehyde-treating agent is provided near or on the inner wall of the tubular portion. If the supply liquid is adjusted so as not to come into contact, the two liquids are effectively mixed and can be used without any problem.

The number of openings (21) in one nozzle is not limited to one, but may be plural. Further, as shown in FIG. 6, the nozzle opening (21) may be inclined. That is, FIG. 6 shows a nozzle having an inclined opening opening toward the mixing section. Further, as shown in FIG. 7, the nozzle may have an opening not only at the tip of the nozzle but also at an intermediate portion reaching the tip of the nozzle. Further, as shown in FIG. 8, when the injection port has a nozzle for injecting the aldehyde treating agent from the outside, even when the tip of the nozzle does not protrude into the pipe of the acrylic acid-containing solution, the acrylic acid-containing solution flows. The cross-sectional area of the nozzle opening and the supply amount of the aldehyde processing agent per unit time are adjusted with respect to the flow velocity of the liquid so that the supply liquid of the aldehyde processing agent does not come into contact with or near the inner wall of the tubular portion (30). With such adjustment, the two liquids are effectively mixed and can be used without any problem.

The mixing apparatus of the present invention has a mixing section which communicates with the acrylic acid-containing liquid and the aldehyde processing agent in communication with the inlet of the aldehyde processing agent. The acrylic acid-containing solution enters from the inlet of the tubular part, and flows into the mixing part together with the supplied aldehyde treating agent. Therefore, the mixing portion needs to have a shape communicating with the tubular portion, but is not limited to a tubular shape.

The distance between the inlet of the aldehyde treating agent provided in the tubular portion and the inlet of the mixing portion is not limited, but is preferably 0.1 to 5.0 times, more preferably 0.2 to 5.0 times the inner diameter of the tubular portion. ~ 3.
It is preferably 0 times, particularly preferably 0.3 to 2.0 times the length. This is because it has been found that when the distance in this range is provided, the aldehyde treating agent is extremely efficiently mixed by the turbulence generated by the flow of the acrylic acid-containing liquid. In this regard, it is extremely difficult to reduce the ratio below 0.1 in terms of construction, while if it exceeds 5.0, mixing may be insufficient. In the specification of the present application, the tubular portion (3
If 0) is not cylindrical, the equivalent inner diameter given by the following equation is calculated as “inner diameter”. By applying the following formula,
Even when the tubular portion (30) is not cylindrical, the mixing portion can be easily connected to a preferable distance. Also, when an injector is used as an injection port for the aldehyde treating agent, a preferable distance from the position where the aldehyde treating agent is supplied to the acrylic acid-containing solution to the mixing section can be easily set. When the tubular portion does not have a uniform inner diameter or an equivalent inner diameter, the minimum distance or the equivalent inner diameter of the tubular portion (30) is used to set a preferable distance to the mixing section.

[0037]

(Equation 1)

The mixing section is preferably a non-stirring mixer connected to the tubular section. Here, the non-stirring type mixer refers to a mixer capable of mixing a plurality of fluids while the equipment itself is stationary by using the flow energy of the fluid, such as a static mixer, an injector, and the like as shown in FIG. Fluid mixer. Furthermore, it is not limited to a commercially available non-stirring type mixer, and a filler used in a distillation operation, a perforated plate, an arbitrary shape such as a sphere shown in FIG. You may use it. For example, in FIG. 10, a porous baffle is disposed at both ends, and a spherical internal structure is disposed between both perforated baffles. The non-stirring type mixer is preferable in that mixing can be performed extremely uniformly without the need for motive energy, and the amount of the aldehyde treating agent can be reduced. In the present invention, any known non-stirring type mixer can be used.

When the mixing section is a non-stirring type mixer,
The length of the mixer is 2 to 35 times the inner diameter of the mixer, more preferably 4 to 25 times, particularly preferably 6 to 2 times.
It is 0 times. In any of the turbulent flow and laminar flow generated when the acrylic acid-containing liquid is fed at a predetermined flow rate, if the above value is less than 2 times, the mixing of the aldehyde treating agent becomes insufficient, and on the other hand, 35 times. This is because there is no difference in the mixing effect even if it exceeds.

The mixing section includes a case where it is a non-stirring type mixer, and is not limited to a case where the mixing section is horizontally communicated with the tubular section as shown in FIG. 1 but is vertically arranged as shown in FIG. May be performed. Further, when the mixing section is arranged vertically, the mixed solution of the acrylic acid-containing solution and the aldehyde treating agent may flow from above the tubular section as shown in FIG. The solution may be flowed toward the water, regardless of the installation direction or the flow direction of the solution. Further, the mixing section is not limited to the case where the mixing section is installed in a horizontal direction or a vertical direction,
It may have a curved portion such as being obliquely arranged or curved or bent.

When the injection port for supplying the aldehyde-treating agent is the injector type shown in FIG. 2, the injector is an injection port and a mixing section for mixing the supplied aldehyde-treating agent with the acrylic acid-containing solution. The function of. For this reason, when an injector is used, the tubular portion, the mixing portion, and the retaining portion referred to in the present application do not always need to be clearly identified structurally, and the supply of the aldehyde treating agent and the mixing of both solutions, or Any location that has the function of staying may be used. Specifically, for example, in FIG.
A tubular body having an opening of an inlet for an acrylic acid-containing liquid or an aldehyde treating agent indicated by reference numeral 21 is a supply unit (3) of the present invention.
0), and the narrowest tubular portion following this is the mixing portion (4).
0), and the stagnation portion (5)
0) is provided.

In the mixing apparatus of the present invention, the retaining section is a section for retaining a mixed liquid of the acrylic acid-containing liquid and the aldehyde treating agent mixed in the mixing section for a predetermined time,
It is necessary to have at least one outlet for the mixture. Generally, the outlet is connected to a pipe leading to the acrylic acid purification tower.

In order to secure the residence time of the mixed liquid for a predetermined time, the maximum of the cross-sectional area of the flow passage of the residence part is 2 times the cross-sectional area of the inlet of the acrylic acid-containing liquid in the tubular part. ~ 5
00 times, more preferably 20 to 400 times, especially 50 to 400 times
Preferably it is 200 times. The aldehyde treatment effect is improved by ensuring a sufficient reaction time between the acrylic acid-containing solution and the aldehyde treatment agent. If the value is less than twice, the required residence time is secured to increase the length of the retention part. In addition, it is disadvantageous because the pressure loss in the stagnation portion increases. On the other hand, if it exceeds 500 times, the flow state in the staying portion is biased, and mixing and / or uniform staying cannot be sufficiently achieved.

Even if the flow rate is within the above range, if the flow state is deviated in the retaining section, a desired residence time may not be secured. Therefore, it is preferable to provide at least a part of an internal structure for ensuring a uniform flow of the mixture. Examples of such an internal structure include a plate-like object, a spherical object, a net-like object, and a band-like object. For example, the plate-like object includes a baffle plate. Further, the baffle plate may have one or more holes through which the mixed liquid can penetrate. In addition, you may install a static mixer or a packing used for a distillation operation as an internal structure.

Such an internal structure may be provided in any of the stagnant portions, but is preferably provided near the mixed liquid inlet of the stagnant portion in order to ensure a uniform residence time.
The stagnation section provided with such an internal structure is shown in FIGS.
Shown in

For example, as shown in FIG. 12a, a plurality of baffles are provided only in the vicinity of the inlet of the mixed liquid in the stagnation portion, and furthermore, in the vicinity of the outlet of the mixed liquid as shown in FIG. 12b. A plate may be provided. Further, as shown in FIG. 12C, a plurality of baffle plates may be evenly arranged on the entire staying portion. Alternatively, a perforated plate may be used as a baffle plate, and a perforated plate may be provided at each of the mixed liquid inlet and the outlet of the retaining portion as shown in FIG. 12D. In addition, a spherical object as shown in FIG. 10, a generally available irregular packing, and other generally available ordered packing such as a net-like material and a band-like material are shown in FIG.
As shown in FIG. 12E, a baffle plate may be provided in a part of the retaining portion, and further, as shown in FIG. It should be noted that, depending on the internal structure provided in the retaining section, the size of the entire retaining section may become large in order to secure a predetermined residence time, and it is preferable to dispose the internal structure only in a part.

Accordingly, the shape of the staying portion is not particularly limited as long as the above-mentioned volume can be secured, but is preferably cylindrical. As described above, it is easy to dispose the internal structure for making the flow of the mixed liquid uniform. In this case, the retaining portion may have an inner diameter different from that of the mixing portion as shown in FIG. 1, or may have a curved portion to meander as shown in FIG. The inner diameter may change on the way from the inlet to the outlet of the nozzle, or may be the same as the mixing section as shown in FIG.

The material of the mixing device of the present invention is not particularly limited, and the same steel material as the supply pipe for the acrylic acid-containing liquid can be preferably used. The material of the steel pipe is not particularly limited, and is preferably an austenitic steel pipe, an austenitic / ferritic steel pipe, or a ferritic steel pipe from the viewpoint of easy production of a welded steel pipe. According to these, they do not react with the acrylic acid-containing liquid, do not modify them, and do not corrode the steel material itself. When the internal structure is a non-stirring mixer, a commercially available mixer can be used. Furthermore, when using an internal structure other than the non-stirring type mixer, the material is also austenitic steel pipe, austenitic / ferritic steel pipe,
It is preferably a ferritic steel pipe. This is because it is easy to wash with various organic solvents, does not react with the acrylic acid-containing liquid, does not modify them, and does not corrode the steel material itself.

The second aspect of the present invention is an acrylic acid purifying apparatus having an acrylic acid purifying tower and the mixing apparatus of the present invention.
When the aldehyde treating agent mixing apparatus of the present invention is provided so as to be connected to a part of an acrylic acid-containing liquid supply pipe from an acrylic acid collecting tower to an acrylic acid purifying tower, the acrylic acid-containing liquid is purified in the acrylic acid purifying tower. In this case, the effect of the aldehyde treating agent is excellently exhibited, and the polymerization in the purification tower and the polymerization of the heat exchanger, the piping and the like can be prevented. In addition, as an acrylic acid refining tower, it is installed in any known refining tower such as a flash column, an irregularly packed tower, an ordered packed tower, a bubble bell tray tower, a valve tray tower, a sieve tray tower, and a sieve tray tower. be able to.

The aldehyde treating agent used in the present invention is:
There is no particular limitation on the compound used for the purpose of purifying acrylic acid by removing the aldehyde contained in the acrylic acid-containing liquid. It may be a case where it can be separated from acrylic acid by precipitation after bonding with an aldehyde to form a complex, or a case where the aldehyde is directly decomposed, regardless of the mechanism of action.

A third aspect of the present invention is a method for continuously purifying acrylic acid by adding an aldehyde treating agent to an acrylic acid-containing liquid obtained by a catalytic gas phase oxidation reaction. 0.05 to liquid speed
This is a method for purifying acrylic acid, wherein the distillation is carried out after addition in a range of 5.0 times and retention for 3 minutes to 150 hours.

The aldehyde contained in the aldehyde is not easily removed by simply adding the aldehyde-treating agent, because it is difficult to secure a predetermined time until the mixing of the treating agent and the onset of the action. The amount of the aldehyde-treating agent added to the acrylic acid-containing liquid can be adjusted according to the amount of the aldehyde contained therein. It is preferable to add 0.0 to 10.0 mol, more preferably 1.0 to 5.0 mol. In addition, when adding so as to have the above concentration, the speed of the aldehyde treating agent is 0.05 to 5.0 times, more preferably 0.1 to 3.0 times, the speed of the acrylic acid-containing solution.
By adding the compound in a range of 0.2 to 1.5 times, mixing of both can be easily performed. If it is less than 0.05, it is necessary to enlarge the supply port in order to add the optimal amount of the aldehyde treating agent to be added, and a backflow of the acrylic acid-containing liquid may occur. Alternatively, if the concentration of the aldehyde treating agent is increased, the mixing of the two solutions may be insufficient. On the other hand,
If it exceeds 5.0 times, the aldehyde treating agent may be added through the flow of the acrylic acid-containing liquid, and the mixing of the two may be insufficient.

The mixture of the acrylic acid-containing liquid and the aldehyde treating agent is allowed to stay for 3 minutes to 150 hours, more preferably 5 minutes to 10 hours, particularly 6 minutes to 4 hours. Here, the retention time is a value obtained by dividing the volume of the retention portion by the flow rate of the acrylic acid-containing liquid. If the time is shorter than 3 minutes, the effect of the aldehyde treating agent is not sufficient, and if the time is longer than 150 hours, it is necessary to enlarge the piping and the storage tank leading to the acrylic acid purification tower, which is disadvantageous. Further, in order to secure such a residence time, a part of a pipe through which the acrylic acid-containing liquid flows can be enlarged. This is because the retention time can be easily secured without providing a special retention section and without changing the pump pressure for pumping the acrylic acid-containing solution.

It is preferred that the aldehyde treating agent and the acrylic acid-containing liquid are uniformly mixed before the residence. By retaining the uniformly mixed solution for a predetermined time,
This is because the aldehyde treating agent can be expressed more effectively. Such mixing can be easily achieved by adding the aldehyde treating agent and then transferring the mixture to, for example, a non-stirring mixer.

The resulting mixture is then purified in an acrylic acid purification tower, and any known purification conditions can be applied for purification.

In the method for purifying acrylic acid of the present invention,
It is necessary that the supply of the aldehyde treating agent be from the acrylic acid collecting tower to the acrylic acid refining tower, but more preferably after the light-boiling distillation and after the high-boiling distillation, and Before transfer to an acid distillation purification column.

The aldehyde treating agent used in the present invention includes:
There is no particular limitation on the compound used for the purpose of purifying acrylic acid by removing the aldehyde contained in the acrylic acid-containing liquid. It may be a case where it can be separated from acrylic acid by precipitation after bonding with an aldehyde to form a complex, or a case where the aldehyde is directly decomposed, regardless of the mechanism of action.

The aldehyde treating agent used in the present invention is preferably a hydrazine compound such as hydrazine hydrate, phenylhydrazine, hydrazine sulfate or hydrazine hydrochloride. The aldehyde treating agent may be liquid or gaseous, but is preferably liquid because it can be easily added. Therefore, when the aldehyde treating agent is solid at room temperature, it is preferable to dissolve it in an appropriate solvent and use it as a solution. Such solvents include:
There is no particular limitation as long as the aldehyde treating agent can be dissolved. More preferably, the aldehyde treating agent is dissolved in a solvent contained in the acrylic acid-containing liquid to which the aldehyde treating agent is added.

The concentration of the compound in the aldehyde treating agent can be adjusted to the most preferable range depending on the concentration of the aldehyde contained in the acrylic acid-containing solution to be added, the rate of addition, and the like.

According to the present method, the contamination of the apparatus by the acrylic acid polymer and other solids is prevented, the amount of the expensive aldehyde treating agent used is minimized as compared with the known method, and the new disposal Material production is minimized.

[0061]

The present invention will now be described more specifically with reference to examples.

Example 1 Using the apparatus shown in FIG. 1, 99.9% by weight of acrylic acid and furfural 1 as an impurity
An acrylic acid-containing liquid containing 50 ppm and 50 ppm of acrolein was supplied to a supply line having an inner diameter of 25 mm at a flow rate of 1.7 m /
s. Here, an 80% aqueous solution of hydrazine hydrate was added at a flow rate of 0.1 at a rate of m / s so that the hydrazine hydrate was 2.0 mole times the total number of moles of furfural and acrolein. As shown in FIG. 7, the tip of the 80% aqueous solution of hydrazine hydrate has a hole having a diameter of 0.8 mm opened on the downstream side, and is disposed at the radial center of the acrylic acid-containing liquid pipe. The distance to the inlet of the non-stirring mixer was 30 mm. In addition, a Kenix type static mixer (non-stirring mixer) having the same inner diameter and a body length of 275 mm is provided as a mixing section downstream thereof, and a cylindrical retaining section having an inner diameter of 300 mm and a straight body length of 6000 mm is further provided downstream thereof. Was provided. As shown in FIG. 12, a perforated plate having a diameter of 300 mm and a porosity of 10% was provided at each of the inlet and the outlet of the staying portion.

The distillation apparatus was a flash column with a mist separator having an inner diameter of 2000 mm, supplied with an acrylic acid-containing liquid at a supply rate of 3.0 m ³ / h and hydroquinone monomethyl ether as a polymerization inhibitor at a rate of 1 kg / h, and a top pressure of 53 hPa abs. The operation was performed under the conditions of a tower top temperature of 65 ° C. and a distilled amount of purified acrylic acid of 2000 kg / h.

When the system was stably operated for 6 months, furfural and acrolein contained in the purified acrylic acid were each 1 ppm or less.

(Comparative Example 1) Under the same operating conditions as in Example 1, an 80% aqueous solution of hydrazine hydrate was supplied from an aldehyde treating agent supply port shown in FIG. And distilled.

As a result, from the beginning of operation, furfural in purified acrylic acid was 46 ppm, and acrolein was 9 ppm.
It became. After operating for 24 hours, hydrazine hydrate 8
When the addition amount of the 0% aqueous solution was increased by 10 mol times, furfural and acrolein in the purified acrylic acid became 1 ppm or less, respectively. However, on the 10th day after the change, the polymer adhered to the mist separator, and the operation became impossible. became.

(Comparative Example 2) Under the same operating conditions as in Example 1, an 80% aqueous solution of hydrazine hydrate was supplied from the aldehyde treating agent supply port shown in FIG. 7 and passed through a non-stirring mixer and a retaining section. Distilled.

As a result, from the beginning of operation, furfural in purified acrylic acid was 22 ppm and acrolein was 5 ppm.
Met. After operating for 24 hours, hydrazine hydrate 8
When the addition amount of the 0% aqueous solution was increased by 8 mol times, furfural and acrolein in the purified acrylic acid each became 1 ppm or less, but on the 14th day after the change, the polymer adhered to the mist separator and the operation became impossible. Was.

(Comparative Example 3) Under the same operating conditions as in Example 1, the tip of the supply nozzle for an 80% aqueous solution of hydrazine hydrate was set to 2.0 mm, and the mixture was distilled through a non-stirring mixer and a retaining section. .

As a result, from the beginning of operation, furfural in purified acrylic acid was 14 ppm, and acrolein was 3 ppm.
It became. After operating for 24 hours, hydrazine hydrate 8
When the addition amount of the 0% aqueous solution was increased by 6.5 times,
Furfural and acrolein in the purified acrylic acid were each 1 ppm or less, but three weeks after the change, the polymer adhered to the mist separator, and the operation became impossible.

(Comparative Example 4) Under the same operating conditions as in Example 1, the length of the stagnation portion after the non-stirring type mixer was set to 3000 mm, and distillation was performed.

As a result, from the beginning of operation, furfural in purified acrylic acid was 32 ppm and acrolein was 7 ppm.
It became. After operating for 24 hours, hydrazine hydrate 8
Although the addition amount of the 0% aqueous solution was increased by 10 times, furfural and acrolein in the purified acrylic acid could only be reduced to 8 ppm and 2 ppm, respectively. The supply amount was 2.25 m ³ / h and the distillate amount was 1
Assuming that the amount of the 80% aqueous hydrazine hydrate solution is 10 mol times, furfural and acrolein in the purified acrylic acid are 1 ppm each.
However, on the 10th day after the change, the polymer adhered to the mist separator, and the operation became impossible.

[0073]

According to the present invention, a non-stirring type mixer and a retaining section are provided in the middle of a pipe leading to an acrylic acid refining tower, an aldehyde treating agent is added at a specific position and at a specific flow rate, and the mixed liquid is supplied to a predetermined position. The aldehyde contained in the acrylic acid-containing liquid can be efficiently removed by allowing the aldehyde treatment liquid to stay for a long time, the amount of the aldehyde treatment agent to be added can be reduced, and the polymerization caused by the addition of the treatment agent can be prevented.

[Brief description of the drawings]

FIG. 1 is a view schematically showing an aldehyde treating agent mixing apparatus of the present invention having a mixing section connected to a tubular section and connected thereto, and a retaining section provided in communication with the mixing section.

FIG. 2 is a view schematically showing an aldehyde treating agent mixing apparatus of the present invention in which an injector is provided in a tubular portion and a mixing portion.

FIG. 3 is a view showing an example of the present invention in which the tip of the aldehyde treating agent addition nozzle is opened downstream.

FIG. 4 is a view showing an example of the present invention in which the tip of the aldehyde treating agent addition nozzle is opened on the upstream side.

FIG. 5 is a view showing an example in which the tip of the aldehyde treating agent addition nozzle penetrates beyond the tubular portion.

FIG. 6 is a view showing an example of the present invention in which the tip of the aldehyde treating agent addition nozzle is inclined and opened downstream.

FIG. 7 is a view showing an example of the present invention in which the aldehyde treating agent addition nozzle has an opening in the middle of the nozzle.

FIG. 8 is a view showing a state in which the tip of the nozzle does not protrude.

FIG. 9 is a diagram showing an example of a non-stirring mixer that can be used in the present invention.

FIG. 10: A perforated baffle plate is provided at both ends as a mixing section,
It is a figure which shows an example in which the internal structure of the sphere was installed between both perforated plates.

FIG. 11 is a view schematically showing an aldehyde-treating agent mixing apparatus of the present invention in which a mixing section is arranged substantially vertically.

FIG. 12 is a view schematically showing an aldehyde-treating agent mixing apparatus of the present invention in which a retaining portion has a meandering cylindrical shape.

FIGS. 13a to 13f are diagrams showing the forms of the aldehyde-treating agent mixing apparatus of the present invention in which the internal structure is disposed in the retaining section, respectively.

FIG. 14 is a view schematically showing an aldehyde-treating agent mixing apparatus of the present invention, in which a retaining section has a cylindrical shape having the same inner diameter as the mixing section.

[Explanation of Signs] 10 ... Inlet of acrylic acid-containing liquid 20 ... Injection port of aldehyde treatment agent 21 ... Nozzle opening 30 ... Tubular part 40 ... Mixing part 50 ... Retention Part 60: Acrylic acid-containing liquid outlet 70 ... Acrylic acid-containing liquid 80: Internal structure

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor: Sei Nakahara 992, Nishioki, Okihama-shi, Aboshi-ku, Himeji-shi, Hyogo Japan Inside Nippon Shokubai Co., Ltd. (72) Inventor Mamoru Takamura 992, Nishioki, Okihama-ji, Aboshi-ku, Himeji-shi, Hyogo F-term in Nippon Shokubai (reference) 4H006 AA02 AA04 AC12 AC46 AD11 AD30 BC50 BE27

Claims (10)

[Claims] 1. A tubular part having an inlet for an acrylic acid-containing liquid obtained by a catalytic gas phase oxidation reaction and an inlet for supplying an aldehyde treating agent, and the acrylic acid-containing liquid connected to and connected to the tubular part. An aldehyde treatment comprising: a mixing part of a liquid and the aldehyde treating agent; a retention part of the obtained mixture provided in communication with the mixing part; and a discharge port of the mixture provided in the retention part. Agent mixing equipment. 2. The aldehyde treating agent mixing apparatus according to claim 1, wherein said mixing section is a non-stirring type mixer. 3. The aldehyde-treating agent mixing apparatus according to claim 1, wherein the staying portion further has at least a part of an internal structure for making the flow of the mixture uniform. 4. The aldehyde treating agent mixing apparatus according to claim 3, wherein said internal structure is a baffle plate. 5. The aldehyde according to claim 1, wherein the distance from the inlet to the inlet of the mixing section is 0.1 to 5 times the inner diameter of the tubular section. Processing agent mixing device. 6. The aldehyde-treating agent mixing apparatus according to claim 5, wherein the inlet is an aldehyde-treating agent addition nozzle protruding from the tubular portion. 7. The aldehyde treating agent mixing apparatus according to claim 6, wherein the tip of the nozzle is opened to the inlet side of the acrylic acid-containing liquid or to the mixing section. 8. The method according to claim 1, wherein the maximum of the cross-sectional area of the flow path of the retaining portion is 2 to 500 times the cross-sectional area of the inlet of the acrylic acid-containing liquid in the tubular portion. The aldehyde treating agent mixing apparatus according to any one of the above. 9. An acrylic acid refining device comprising an acrylic acid refining tower and the aldehyde treating agent mixing device according to any one of claims 1 to 8. 10. A method for continuously purifying acrylic acid by adding an aldehyde treating agent to an acrylic acid-containing solution obtained by a catalytic gas phase oxidation reaction, wherein the aldehyde treating agent is added to the acrylic acid-containing solution at a rate of In the range of 0.05 to 5.0 times, and 3 minutes to 15 times.
A method for purifying acrylic acid, wherein distillation is carried out after having been retained for 0 hours.