JP2002155021A - Polymerization inhibitor composition for vinyl monomer and method for producing high-purity (meth)acrylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent polymerization inhibitor composition having special effects on prevention of polymerization of (meth)acrylic acid readily polymerizable with heat and to provide an efficient method for producing high- purity (meth)acrylic acid comprising purifying the (meth)acrylic acid using the polymerization inhibitor composition. SOLUTION: A composition consisting essentially of hydroquinone, hydroquinone monomethyl ether and phenothiazine is used as the polymerization inhibitor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a polymerization inhibitor composition for vinyl monomers, in particular, polymerization for acrylic acid and methacrylic acid (both are hereinafter referred to as "(meth) acrylic acid"). The present invention relates to a method for producing high-purity (meth) acrylic acid using the polymerization inhibitor composition, and belongs to a chemical product production technique.

[0002]

2. Description of the Related Art (Meth) acrylic acid is obtained by oxidizing propylene, isobutylene, or the like with molecular oxygen in the presence of an oxidation catalyst and steam. At this time, acetic acid, formic acid, Propionic acid, acetaldehyde, formaldehyde, carbon dioxide, carbon monoxide and the like are produced simultaneously.

When such a reaction product and a mixed gas containing unreacted propylene and acrolein are cooled and absorbed in water, an aqueous solution containing (meth) acrylic acid, acetic acid, formic acid, propionic acid, aldehydes and the like is obtained. (Coarse (meta)
Acrylic acid).

Accordingly, in the production of (meth) acrylic acid, a step of finally separating (meth) acrylic acid from the above-mentioned aqueous solution of crude (meth) acrylic acid and a step of purifying it are necessary. There has been a demand for highly pure (meth) acrylic acid, which has a very small amount of such impurities present in (meth) acrylic acid, and how to efficiently perform a distillation operation in a separation or purification step. Has become a very important requirement.

[0005] On the other hand, (meth) acrylic acid is a compound which is easily polymerized by light or heat. Therefore, in order to prevent polymerization during its production, transportation or storage, various polymerization inhibitors are used alone or in combination of several kinds. It has been used as an additive.

For example, diphenylamine, p-phenylenediamine, phenothiazine, hydroquinone, methylene blue, phenyl-β-naphthylamine, resorcinol and the like have been known and widely used as polymerization inhibitors for vinyl compounds. But also.

It is also known to use these polymerization inhibitors in combination, for example, as described in JP-A-5-19.
Japanese Patent No. 4614 discloses that a combination of N, N'-dinitrosophenylenediamine and phenothiazine, hydroquinone or hydroquinone monomethyl ether is effective in suppressing the polymerization of acrylic acid and its ester. No. 3099 discloses that a combination of a p-phenylenediamine compound and a phenol compound or phenothiazine effectively prevented the polymerization of (meth) acrylic acid.

In order to industrially produce (meth) acrylic acid and obtain the above-mentioned high-purity (meth) acrylic acid, distillation in the separation and purification steps, that is, water, acetic acid existing as impurities, And a distillation step for purifying by removing aldehydes, for example, a (meth) acrylic acid rectification column, a dehydration distillation column performed after adding an azeotropic solvent with water to a (meth) acrylic acid aqueous solution, or (meth) From a solution of (meth) acrylic acid extracted with a solvent from an aqueous solution of acrylic acid (meth)
Operates under very severe conditions in the separation tower of acrylic acid and solvent, the separation tower of low boiling components such as (meth) acrylic acid and acetic acid, and the stripper of aldehydes such as acrolein and methacrolein as low boiling components In order to be an industrial production method, it is required to be efficient.

However, using the above-mentioned known polymerization inhibitors and the polymerization inhibitors obtained by combining them, under severe conditions, that is, at a high temperature for a long period of distillation operation, the polymerization of (meth) acrylic acid can be carried out. It is difficult to prevent the polymerization, and the only way to prevent polymerization is to use a large amount of a polymerization inhibitor. However, in practice, excessive polymerization inhibitors could not be used, and long-term continuous operation of the distillation column was practically impossible.

For this reason, in a distillation column or the like, a polymer in the form of popcorn or a viscous polymer is generated in a few months, and the tower is clogged by this generation. It is necessary to remove the coalescence, and it is difficult to perform the operation efficiently, and a solution is strongly demanded.

[0011]

SUMMARY OF THE INVENTION The present inventors have investigated the properties of many known polymerization inhibitors and studied the combinations thereof. As a result, three types of polymerization inhibitors, hydroquinone, hydroquinone monomethyl ether and phenothiazine, were obtained. When the polymerization inhibitors are used in combination, particularly when used in a certain ratio, they exhibit an effect surpassing the case of using each alone or in combination of two types, and have found that the above-mentioned problems can be solved, and have completed the present invention. .

That is, the present invention provides an excellent polymerization inhibitor composition for vinyl monomers, particularly a polymerization inhibitor composition having an excellent effect in preventing polymerization of (meth) acrylic acid which is easily polymerized by heat. In addition, it effectively inhibits the prevention of polymerization of (meth) acrylic acid in the distillation step when producing purified (meth) acrylic acid,
It is intended to provide a method for producing high-purity (meth) acrylic acid that enables efficient production, and more specifically, to produce high-purity (meth) acrylic acid that can be continuously operated for one year or more. It does not provide a method.

[0013]

In order to achieve the above-mentioned object, a polymerization inhibitor composition for a vinyl monomer according to the present invention is characterized by comprising hydroquinone, hydroquinone monomethyl ether and phenothiazine as main components. It is.

The invention according to claim 2 comprises hydroquinone, hydroquinone monomethyl ether and phenothiazine as main components, and the combined ratio thereof is 40 to 80% by mass:
1 to 30% by mass: 10 to 50% by mass of the polymerization inhibitor composition for vinyl monomers.

[0015] The third aspect of the present invention is the first or second aspect.
The vinyl monomer according to the invention is acrylic acid or an ester thereof, or methacrylic acid or an ester thereof, which is a polymerization inhibitor composition for a vinyl monomer.

The invention described in claim 4 is the first or second invention.
The present invention provides a method for producing high-purity acrylic acid or methacrylic acid, comprising purifying by distillation in the presence of the polymerization inhibitor composition for a vinyl monomer according to the invention described in 1 above.

Hereinafter, the polymerization inhibitor composition for vinyl monomers of the present invention and the method for producing high-purity (meth) acrylic acid will be described in detail.

In the present invention, the main components of the polymerization inhibitor composition for vinyl monomers are three kinds of compounds of hydroquinone, hydroquinone monomethyl ether and phenothiazine.

All of these compounds are known as polymerization inhibitors and are commercially available. In the present invention, commercially available products can be used.

From the results of tests in the laboratory and the results in the production equipment, the synergistic effects are remarkably recognized from 40 to 80% by mass of hydroquinone, 1 to 30% by mass of hydroquinone monomethyl ether, It is preferred that the phenothiazine is in a ratio of 10 to 50% by mass. If the amount of hydroquinone monomethyl ether used is less than 1% by mass, the effect of preventing polymerization tends to be insufficient, while if it exceeds 30% by mass, there is no significant difference in the effect of preventing polymerization. Since hydroquinone monomethyl ether has a relatively low boiling point as described later, it is also diffused into the gas phase during the distillation operation of the vinyl monomer, and the vaporized monomer is cooled and condensed on the inner wall of the distillation column. It effectively prevents the polymerization that occurs at the time.

More preferably, the ratio of hydroquinone is 50 to 70% by mass, hydroquinone monomethyl ether is 5 to 15% by mass, and phenothiazine is 20 to 4% by mass.
It is preferably 0% by mass, and the combined ratio of hydroquinone and phenothiazine is preferably 1: 1 to 6: 1 (mass ratio).

The amount of the polymerization inhibitor composition for a vinyl monomer used in these inventions greatly varies depending on the type of the vinyl monomer for which polymerization is to be prevented, its environmental conditions, and the like. For example, as long as the polymerization of a vinyl monomer used for storage and storage is simply prevented, it may be present in the vinyl monomer in an amount of from 5 to 100 ppm. As long as the polymerization is prevented during distillation in the apparatus, it is usually preferable to use the vinyl monomer in an amount of 400 to 2000 ppm.

Specific examples of the vinyl monomer to which the polymerization inhibitor composition for a vinyl monomer in these inventions is applied include (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (Meth) acrylate, cyclohexyl (meth) acrylate, 2-
Alkyl (meth) acrylates such as ethylhexyl (meth) acrylate and stearyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-
Hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, (meth) acrylamide, (meth) acrylonitrile, vinylpyrrolidone, styrene, α-methylstyrene and Vinyl toluene and the like. Among these, it is preferable to apply to (meth) acrylic acid and (meth) acrylic acid ester, for which it is desired to apply a polymerization inhibitor having a high radical polymerizability and a high polymerization inhibitory effect, and more preferably. This is an application to (meth) acrylic acid.

The proper use amount of the polymerization inhibitor composition for vinyl monomers in each industrial production apparatus must be determined experimentally in consideration of the scale of the apparatus, operating conditions of the apparatus, and the like. For example, when producing (meth) acrylic acid,
When the extraction solvent is removed by a distillation column, or when acetic acid produced as a by-product is removed by the distillation column, the appropriate amount in the treatment liquid in the distillation column is 400 to 1500 ppm.

In the present invention, there is no particular limitation on the method of using the polymerization inhibitor composition for vinyl monomers.
It may be added in the same manner as a conventionally known polymerization inhibitor, and may be added as a solution such as a process intermediate liquid, an organic solvent or a product.

In a distillation column where the vinyl monomer is heated and partially vaporized, and it is difficult to apply a polymerization inhibitor such as molecular oxygen, the vinyl monomer in another process may be used. In comparison, the monomer is liable to undergo polymerization, so that the method of adding the polymerization inhibitor composition of the present invention to such a distillation column is particularly preferable. There is no particular limitation on the timing of addition, and the three components can be used individually or simultaneously, for example, in the form of a single solution.

The main object of the present invention is to prevent polymerization during the distillation in the vinyl monomer production apparatus by directly dissolving the liquid supplied to the distillation column using a pipe or a storage tank. The objective can be achieved by removing a part of the distillate, adding and dissolving the distillate, and returning the distillate to the distillation column.

It is preferable that these polymerization inhibitor compositions for vinyl monomers are added directly to a distillation column in which polymerization is particularly liable to occur, and the polymerization inhibitor compositions for vinyl monomers in a solution state are preferably added. Is preferably added to the top or middle stage of the distillation column.

When these polymerization inhibitor compositions for vinyl monomers are added to a feed solution or a reflux solution as an organic solvent solution, methyl ethyl ketone, toluene or the like is used as a solvent to be used. It is preferable to use a solvent which is already present in the feed liquid or the reflux liquid and has been used as an azeotropic or extraction solvent so as not to cause the problem.

Further, a bottom liquid such as the above-mentioned distillation column, in particular,
Since the polymerization inhibitor composition for vinyl monomers is accumulated in the bottom liquid of the distillation tower (rectification tower) that finally obtains high-purity (meth) acrylic acid, the bottom liquid itself is used. It is preferable to use a polymerization inhibitor composition solution for a vinyl monomer by adding it to a crude (meth) acrylic acid storage tank, a pipe, a distillation tower, or the like. It is a recycling of the polymerization inhibitor composition for use and resource saving.

As described above, these bottom liquids are also preferably added from the top of the distillation column which is easily polymerized, preferably to the middle stage.
The polymerization in the distillation column can be prevented.

The polymerization inhibitor composition for a vinyl monomer of the present invention can be prepared by using a conventionally known polymerization inhibitor such as diphenylamine, dialkyl (or phenyl) dithiocarbamic acid copper salt (alkyl group: methyl, ethyl, propyl, butyl) , Tetraalkyl (or phenyl) thiuram disulfide (alkyl group: methyl, ethyl, propyl, butyl), methylene blue, and the like.

Further, the polymerization inhibitor composition for vinyl monomers of the present invention is preferably used in combination with molecular oxygen which has been confirmed to have a polymerization preventing effect. Regarding the supply method of this molecular oxygen, when it is supplied to the vinyl monomer-containing process liquid in a gaseous state from the bottom of a distillation column or a stripper or a reboiler by air bubbling or the like, the whole of the process can be easily spread.

It is desirable that the molecular oxygen be supplied in an amount of about 0.1 to 5% by volume based on the amount of vaporized vapor of the vinyl monomer.

[0035]

The three components constituting the polymerization inhibitor composition for vinyl monomers of the present invention, that is, hydroquinone, hydroquinone monomethyl ether and phenothiazine are all known compounds having a polymerization inhibitory effect,
It is assumed that each has the following characteristics.

It is effective in the presence of oxygen in the liquid phase of hydroquinone . Hydroquinone monomethyl ether has a relatively low boiling point and diffuses into the gas phase during the distillation operation, so it is effective in preventing polymerization due to condensation of vinyl monomers on the inner wall of the distillation column. It works in the absence of oxygen in the phenothiazine liquid phase. In other words, it is effective for a degassed vinyl monomer or a vinyl monomer in a portion that easily becomes anoxic.

However, the effect of the present invention, particularly the synergistic effect of the combination of the above three components, cannot be determined from the above characteristics at all. As a result, the polymerization of the vinyl monomer, particularly (meth) acrylic acid, can be prevented, and the polymerization can be effectively prevented even in a distillation column maintained at a high temperature.

[0038]

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

Example 1 A flask having an air blowing tube was charged with 50 ml of a test solution obtained by adding 200 ppm in total of the compounds shown in Table 1 (mass ratio) to acrylic acid from which a polymerization inhibitor had been removed by distillation. And heated to 120 ° C. in an oil bath. During heating, add 1
00 ml / min was blown. Table 1 shows the polymerization start time of each test solution visually measured under these conditions. still,
Abbreviations Hq in the table indicate hydroquinone, Mq indicates hydroquinone monomethyl ether, and PZ indicates phenothiazine.

[0040]

[Table 1]

Example 2 In an apparatus for producing acrylic acid by oxidizing propylene, a rectification column for acrylic acid, a separation column for acrylic acid and an extraction solvent, a separation column for acrylic acid and a low-boiling component such as acetic acid, etc. In order to prevent the polymerization of acrylic acid in the column (1), a methyl isobutyl ketone solution of a polymerization inhibitor comprising 60% by mass of hydroquinone, 10% by mass of hydroquinone monomethyl ether and 30% by mass of phenothiazine was prepared.

The prepared polymerization inhibitor solution was added from the top of each column so that the concentration in the reflux liquid became 650 ppm in principle, and the operation was continued while maintaining the concentration. However, since the low-boiling separation column is a column in which polymerization is particularly likely to occur, the bottom liquid of the column (during normal operation, the polymerization inhibitor concentration is 3000
is concentrated to the upper part of the middle stage where the polymerization is particularly likely to occur, and the concentration in the reflux liquid from the middle stage to the bottom is 770 ppm.

The concentration of the polymerization inhibitor in the acrylic acid before rectification, which is the final step, is 350 ppm. To adjust the concentration, the bottom liquid of the acrylic acid recovery step (the concentration of the polymerization inhibitor was reduced to about 1%). (Concentrated) and the concentration was adjusted to 550 ppm.

When the operation was continued under the above conditions, no abnormalities were observed in each tower for one year until the operation was stopped due to periodic repair, and the operation could be performed smoothly.

[0045]

According to the three-component polymerization inhibitor composition for a vinyl monomer of the present invention, the polymerization inhibitory effect of (meth) acrylic acid is remarkably higher than that of a single component of each component. Since polymerization can be prevented even under conditions in which (meth) acrylic acid is extremely liable to be polymerized, polymerization in the distillation step can be effectively prevented in the production of (meth) acrylic acid, and the production of (meth) acrylic acid can be prevented. Enables long-term continuous operation of the device.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Noriyuki Masuda 17-23, Showa-cho, Minato-ku, Nagoya-shi Toagosei Co., Ltd.In the Nagoya Plant (72) Inventor Soichi Nomura 17-23, Showa-cho, Minato-ku, Nagoya-shi Toagosei Co., Ltd. F-term in Nagoya factory of formula company (reference) 4H006 AA02 AD11 AD41 BS10

Claims (4)

[Claims] 1. A polymerization inhibitor composition for a vinyl monomer, comprising hydroquinone, hydroquinone monomethyl ether and phenothiazine as main components. 2. The combined ratio of the hydroquinone, hydroquinone monomethyl ether and phenothiazine is 40 to 80% by mass: 1 to 30% by mass: 10 to 50% by mass.
The polymerization inhibitor composition for a vinyl monomer according to claim 1, wherein 3. The polymerization inhibitor composition for a vinyl monomer according to claim 1, wherein the vinyl monomer is acrylic acid or an ester thereof, or methacrylic acid or an ester thereof. 4. A method for producing high-purity acrylic acid or methacrylic acid, comprising purifying by distillation in the presence of the polymerization inhibitor composition for vinyl monomers according to claim 1 or 2.