JP2003246764A - Method for producing (meth)acrylic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing (meth)acrylic acid by a gas phase catalytic oxidation having an azeotropic dehydration process which prevents production of polymers inside the azeotropic dehydration column and in which distillation can be carried out smoothly and economically. <P>SOLUTION: The method for producing (meth)acrylic acid comprises the steps of subjecting propane, propylene, isobutylene or t-butanol to the gas phase catalytic oxidation, bringing the resultant oxidation reaction mixture into contact with water to obtain an aqueous solution of (meth)acrylic acid, performing the azeotropic dehydration in the presence of an azeotropic agent, and separating a low boiling component and a high boiling component from the resultant crude acrylic acid. In the azeotropic dehydration process, a phenol inhibitor is supplied at a position of a raw material supply plate or above of the azeotropic dehydration column and a copper inhibitor is supplied at a position below the raw material supply plate. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing (meth) acrylic acid. More specifically, the present invention is a method for producing (meth) acrylic acid by a vapor phase catalytic oxidation method, which can prevent the formation of a polymer inside an azeotropic dehydration distillation column and perform distillation smoothly and economically. The present invention relates to a method for producing (meth) acrylic acid having an azeotropic dehydration distillation step.

[0002]

2. Description of the Related Art The production of (meth) acrylic acid by a vapor-phase catalytic oxidation method is usually carried out by a step of vapor-phase catalytic oxidation of propane, propylene, isobutylene or t-butanol, and then contacting the resulting oxidation reaction mixture with water. To obtain an aqueous solution of (meth) acrylic acid, a step of performing azeotropic dehydration distillation in the presence of an azeotropic agent, and a step of separating a light-boiling component and a high-boiling component from the obtained crude acrylic acid. Consists of. (Meta)
Since the aqueous solution of acrylic acid usually contains acetic acid and aldehydes as impurities, the polymerization of (meth) acrylic acid is extremely likely to occur. In particular, polymerization is extremely likely to occur in a vapor retaining part such as a vapor concentrating part and a condensing part in an azeotropic dehydration distillation apparatus.

As a method for preventing polymerization of a vinyl compound in an azeotropic dehydration distillation apparatus, a method of spraying a solution in which a polymerization inhibitor is dissolved in a vinyl compound from the top of a distillation column is disclosed (for example, a patent). References 1 and 2).
However, in such a method, the effect of inhibiting polymerization is insufficient, popcorn polymers and viscous polymers are generated during distillation, and long-term continuous operation of the (meth) acrylic acid production apparatus is impossible.

[0004]

[Patent Document 1] Japanese Examined Patent Publication No. 50-6449

[Patent Document 2] Japanese Unexamined Patent Publication No. 2-193944

[0005]

Therefore, an object of the present invention is a method for producing (meth) acrylic acid by a vapor phase catalytic oxidation method, which prevents the formation of a polymer inside an azeotropic dehydration distillation column, An object of the present invention is to provide a method for producing (meth) acrylic acid having an azeotropic dehydration distillation step that enables smooth and economical distillation.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the use of a combination of specific polymerization inhibitors
The knowledge that the above problems can be achieved was obtained, and the present invention was completed.

That is, the gist of the present invention is to provide a step of vapor-phase catalytic oxidation of propane, propylene, isobutylene, or t-butanol, and contact the resulting oxidation reaction mixture with water to obtain an aqueous solution of (meth) acrylic acid. Consisting of a process and a process of performing azeotropic dehydration distillation in the presence of an azeotropic agent (meta)
A method for producing acrylic acid, wherein, in the azeotropic dehydration distillation step, the phenol-based inhibitor is supplied from a position higher than the raw material supply stage of the azeotropic dehydration distillation column, and from a position lower than the raw material supply stage. A method for producing (meth) acrylic acid is characterized by supplying a copper-based inhibitor.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The method for producing (meth) acrylic acid of the present invention comprises propane,
A step of vapor-phase catalytic oxidation of propylene, isobutylene or t-butanol, a step of contacting the obtained oxidation reaction mixture with water to obtain an aqueous solution of (meth) acrylic acid, and azeotropic dehydration in the presence of an azeotropic agent. And the step of performing distillation.

The case where the present invention is applied in the process of producing acrylic acid by vapor-phase catalytic oxidation of propylene will be described below as an example.

First, propylene is vapor-phase catalytically oxidized to obtain acrylic acid. The gas-phase catalytic oxidation reaction is usually carried out using a fixed-bed multitubular reactor in the presence of a Mo-Bi-based composite oxide catalyst in the pre-stage reaction in which propylene is mainly oxidized to produce acrolein and the pre-stage reaction. Generated acrolein is Mo-
It comprises a post-reaction step in which acrylic acid is produced by oxidation in the presence of a V-based complex oxide catalyst.

Typical examples of industrialized methods for producing acrolein and acrylic acid include a one-pass method, an unreacted propylene recycling method and a combustion waste gas recycling method. In the present invention, the above three methods are included. Therefore, the reaction system is not limited.

Next, the oxidation reaction mixture obtained by the vapor phase catalytic oxidation reaction is brought into contact with water to obtain an aqueous solution of acrylic acid. The concentration of acrylic acid is usually 40% by weight or more.

Next, azeotropic dehydration distillation of an aqueous solution of acrylic acid is carried out in the presence of an azeotropic agent. In this azeotropic dehydration distillation, not only water but also acetic acid may be azeotropically separated at the same time. As the azeotropic agent, solvents such as ketones and aromatic hydrocarbons are usually used. The type of distillation column used in the azeotropic dehydration distillation step is not particularly limited,
Any of a perforated plate column, a bubble cap column, a packed column, and a distillation column of a type combining these (for example, a combination of a perforated plate column and a packed column) can be used, and preferably, a perforated plate column and a packed column. , A combined tower of a perforated plate tower and a packed tower.

The material of the distillation column is not particularly limited, but SUS304, SUS304 are used because acrylic acid is handled.
L, SUS316, SUS316L, SUS317, S
US317L, SUS329J1L, SUS329J2
Stainless steels such as L and nickel-based alloys such as Hastelloy and Inconel are preferable.

An overflow weir and a downcomer (crossflow tray) may be provided in the distillation column. Examples of the tray include a bubble cap tray, a perforated plate tray, a valve tray, a super flash tray, a Maxflux tray, and a dual tray. The number of trays used is usually 25 to 50 (theoretical tray number: 5 to 20).

When a packed tower is used, the packing to be packed in the tower is a columnar, cylindrical, saddle-shaped, cubic, or pyramidal-shaped packing that has been conventionally used, or a high-performance packing. Regular or irregular packings with a special shape can also be used. Further, two or more kinds of fillers may be used in combination.

As the above-mentioned regular packing, "Sulzer Pack" manufactured by Sulzer Brothers Co., Ltd., "Sumitomo Sulzer Packing" manufactured by Sumitomo Heavy Industries Co., Ltd., "Merapack" manufactured by Sumitomo Heavy Industries Co., Ltd. , Glitch Co., Ltd. “Gem Pack”, Monts Co., Ltd. “Monts Pack”, Tokyo Special Wire Mesh Co., Ltd. “Good Roll Packing”, NGK Insulators Co., Ltd. “Honeycomb Pack”, Nagaoka Co., Ltd. “ “Impulse packing” and the like are exemplified.

As the irregular packing, "Interlocks Saddle" manufactured by Norton Co., Ltd., Nittetsu Kakoki Co., Ltd.
Examples include "Terralet" manufactured by BASF, "Pole ring" manufactured by BASF Corporation, "Cascade Mini Ring" manufactured by Mass Transfer Co., Ltd., "Flexi Ring" manufactured by JGC Corporation, and the like.

In the present invention, the phenol-based inhibitor is supplied to the azeotropic dehydration distillation column at a stage higher than the raw material supply stage, and the copper-based inhibitor is supplied at a position lower than the raw material supply stage. In this way, by supplying different polymerization inhibitors depending on the stages in the distillation column, it is possible to achieve a sufficient polymerization inhibition effect with an economical usage amount.

Examples of the phenol-based inhibitor include hydroquinone, metoquinone (methoxyhydroquinone), cresol, phenol, t-butylcatechol and the like, with preference given to hydroquinone, methoquinone or a mixture thereof. These phenol-based inhibitors may be used alone or in combination of two or more.

The supply amount of the phenol-based inhibitor is usually 10 to 800 weight p with respect to the acrylic acid supplied to the distillation column.
pm, preferably 50 to 600 ppm by weight. If the amount supplied is too small, the effect of inhibiting polymerization will be insufficient. If the supply amount is too large, the effect of inhibiting polymerization will not be affected, but the inhibitor will be wasted and it is not economically preferable.

Examples of the copper-based inhibitor include copper acetate, copper carbonate, copper acrylate, copper dimethyldithiocarbamate, copper diethyldithiocarbamate, copper dipropyldithiocarbamate, copper dibutyldithiocarbamate, copper dipentyldithiocarbamate, copper dihexyldithiocarbamate. Examples include copper dithiocarbamate such as copper diisopropyldithiocarbamate, copper diisobutyldithiocarbamate, copper methylisopropyldithiocarbamate, copper piperidiyldithiocarbamate, copper morpholiniyldithiocarbamate, and copper diphenyldithiocarbamate, among which copper dibutyldithiocarbamate, It is preferable to use at least one of copper acetate, copper carbonate and copper acrylate. These copper-based inhibitors may be used alone or in combination of two or more.

The supply amount of the copper-based inhibitor is usually 1 to 100 ppm by weight, preferably 10 to 80 ppm by weight, based on the acrylic acid supplied to the distillation column. If the amount supplied is too small, the effect of inhibiting polymerization will be insufficient. If the addition amount is too large, not only the inhibitor is wasted, but also the bottom of the distillation column may be corroded.

In addition to the above-mentioned polymerization inhibitor, oxygen gas and other polymerization inhibitors generally used as a polymerization inhibitor may be used in combination, if necessary. Other polymerization inhibitors include phenothiazine and bis- (α-methylbenzyl).
Phenothiazine, 3,7-dioctylphenothiazine,
Phenothiazine compounds such as bis- (α, α'-dimethylbenzyl) phenothiazine; tert-butyl nitroxide, 2,2,6,6-tetramethyl-4-hydroxypiperidyl-1-oxyl, 2,2,6,6 -Tetramethylpiperidyl-1-oxyl, 2,2,6,6-tetramethylpiperidinooxyl, 4-hydroxy-2,2
6,6-tetramethylpiperidinooxyl, 4,4 ',
N-oxyl compounds such as 4 ″ -tris- (2,2,6,6-tetramethylpiperidinooxyl) phosphite; phenylenediamines such as p-phenylenediamine; nitroso compounds such as N-nitrosodiphenylamine; urea Etc., and thioureas such as thiourea, etc. When a phenol inhibitor is used in combination with another polymerization inhibitor (excluding copper inhibitors) as an inhibitor mixture The proportion of the phenol-based inhibitor (the total amount of two or more phenol-based inhibitors) is usually 30% by weight or more, preferably 60% by weight or more. When used as a mixture of inhibitors in combination with other polymerization inhibitors, copper-based inhibitors (if there are two or more copper-based inhibitors, the total amount)
Is usually 1% by weight or more, preferably 10% by weight or more.

Since the above-mentioned phenol-based inhibitor and copper-based inhibitor are liquid or solid at room temperature, they can be supplied to a predetermined stage as they are, but these inhibitors can be used as acrylic monomer only by using a small amount. Since polymerization can be sufficiently prevented, it is preferable to use a solvent as a solution or a slurry from the viewpoint of uniform supply and cost reduction. A phenol-based inhibitor may be supplied to the raw material supply stage of the azeotropic dehydration distillation column. In this case, the phenol-based inhibitor is preferably dissolved in the raw material before use.

Water or an organic solvent is used as the above solvent. Examples of the organic solvent include ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, carboxylic acids such as acetic acid, propionic acid, acrylic acid and methacrylic acid, aromatic hydrocarbons such as benzene, toluene and xylene, methyl acetate and butyl acetate. The ester may be mentioned, and these solvents may be used in combination of two or more kinds. Among them, water / toluene mixture, water / acrylic acid mixture, and crude acrylic acid containing acrylic acid dimer or trimer are preferable.

The distillation operation of the present invention can be applied to both continuous distillation and batch distillation. Distillation operation conditions are determined in consideration of the type and content of impurities contained in the acrylic monomer, and are not particularly limited.

The temperature at the bottom of the azeotropic dehydration distillation column is 100.
It is preferably at most ° C. Azeotropic dehydration distillation is usually
Since it is carried out under reduced pressure, the temperature of the bottom bottoms can be controlled by adjusting the degree of pressure reduction at the top of the column. The pressure at the top of the azeotropic dehydration distillation is usually 13.3 to 39.9 kPa (100 to
It is adjusted to 300 mmHg).

[0029]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples unless it exceeds the gist thereof. The unit ppm in the following examples and comparative examples is based on weight.

Example 1 Azeotropic distillation of an acrylic acid aqueous solution was carried out using a packed column equipped with a 1000 ml glass flask at the bottom of the column, a distillation tube at the top of the column, and a raw material supply pipe at the center. . The feedstock was prepared using crude acrylic acid obtained by the vapor phase catalytic oxidation reaction of propylene. The composition was 51.5% by weight of acrylic acid, 2.5% by weight of acetic acid, and 46.0% by weight of water.

To the above aqueous solution of acrylic acid, 200 ppm of hydroquinone and methoquinone, which are phenolic inhibitors, were added to acrylic acid. The above acrylic acid aqueous solution was supplied to the distillation column as a solution at a supply rate of 275 g / hr. Further, an acrylic acid solution of copper dibutyldithiocarbamate (corresponding to 60 ppm with respect to acrylic acid as a feed material) was supplied as a solution at a supply rate of 10 g / hr from the bottom of the packing to the first theoretical plate. Toluene was used as an azeotropic agent, and distillation was performed while circulating it as a reflux liquid. Further, air was supplied from the bottom of the column using a capillary tube at a rate of 5 ml / min. The operating conditions are shown in Table 1 below.

[0032]

[Table 1] Tower bottom temperature: 90 ℃ Tower top temperature: 50 ° C Tower top pressure: 23.94 kPa (180 Torr)

In a steady state, the liquid extracted from the column bottom was analyzed by gas chromatography. As a result, the composition was acrylic acid: 89.7% by weight, acetic acid: 3.7% by weight, water: 0. It was 0.3% by weight and toluene: 6.3% by weight. During continuous operation for 10 hours, generation of polymer was not observed in the tower or in the bottom liquid.

Examples 2 to 3 and Comparative Examples 1 to 3 Azeotropic dehydration distillation was carried out in the same manner as in Example 1 except that the kind of the inhibitor and the addition position were changed. The results are shown in Tables 2 and 3 below. The continuous distillation time for evaluation was set to 10 hours as in Example 1, but "stopped" in less than 10 hours.
In the comparative example described as, the pressure difference between the bottom and the top of the column was 1.33 kPa (10 Torr) or more because of clogging by the acrylic acid polymer generated in the column, and continuous distillation was impossible. It is a thing.

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

As described above, according to the present invention, in the azeotropic dehydration distillation step of the method for producing (meth) acrylic acid by the vapor phase catalytic oxidation method, the polymer in the azeotropic dehydration distillation column is polymerized. Since it is possible to prevent the generation of methane and perform distillation smoothly and economically, the industrial value of the present invention is high.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C07C 57/075 C07C 57/075 // C07B 61/00 300 C07B 61/00 300 (72) Inventor Nei Ogawa No. 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Chemical Co., Ltd. (72) Inventor Yoshiro Suzuki, Toho-cho, Yokkaichi, Mie 1-term, Mitsubishi Chemical Co., Ltd. F-term (reference) 4H006 AA02 AC46 AD12 AD41 BA12 BA13 BA14 BB31 BC13 BD21 BD80 BE30 BS10 4H039 CA22 CA29 CA62 CA65 CC10 CC30

Claims (4)

[Claims] 1. A step of vapor-phase catalytic oxidation of propane, propylene, isobutylene or t-butanol, a step of bringing the obtained oxidation reaction mixture into contact with water to obtain an aqueous solution of (meth) acrylic acid, and an azeotropic agent. A process for producing (meth) acrylic acid, which comprises a step of performing azeotropic dehydration distillation in the presence of a phenol-based compound from a position higher than a raw material supply stage of an azeotropic dehydration distillation column in the azeotropic dehydration distillation step. A method for producing (meth) acrylic acid, which comprises supplying the inhibitor and supplying the copper-based inhibitor from a position lower than the raw material supply stage. 2. An azeotropic dehydration distillation column comprising a perforated plate column, a packed column,
The manufacturing method according to claim 1, wherein the manufacturing method is one of a combined tower of a perforated plate tower and a packed tower. 3. The method according to claim 1, wherein the phenol-based inhibitor is hydroquinone, methoquinone or a mixture thereof. 4. The copper-based inhibitor is copper dithiocarbamate,
The manufacturing method according to claim 1, wherein the manufacturing method is at least one selected from the group consisting of copper acetate, copper carbonate, and copper acrylate.