JPH10114700A - Purification of saturated aliphatic carboxylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the purification of a saturated aliphatic carboxylic acid using a simple process by hydrogenating a saturated aliphatic carboxylic acid containing unsaturated aliphatic carboxylic acid in the presence of a transition metal catalyst. SOLUTION: A saturated aliphatic carboxylic acid containing unsaturated aliphatic carboxylic acid is hydrogenated in the presence of a transition metal catalyst (preferably palladium or platinum supported on activated carbon, silica, etc.). The saturated aliphatic carboxylic acid is e.g. acetic acid by-produced from an acrylic acid production plant and containing acrylic acid as an impurity. In this case, the content of acrylic acid in acetic acid is preferably 0.05-5wt.%. The hydrogenation reaction is preferably carried out by using 2-10mol of hydrogen based on 1mol of the unsaturated aliphatic carboxylic acid at 30-100 deg.C under 5-50kg/cm<2> pressure. The amount of the catalyst is preferably 1-5wt.% based on the saturated aliphatic carboxylic acid when the saturated aliphatic carboxylic acid contains 1wt.% of unsaturated aliphatic carboxylic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for purifying a saturated aliphatic carboxylic acid. More specifically, the present invention relates to a method for purifying a saturated aliphatic carboxylic acid containing an unsaturated carboxylic acid as an impurity such as acetic acid containing acrylic acid.

[0002]

2. Description of the Related Art Among saturated aliphatic carboxylic acids, acetic acid, for example, is widely used as a raw material for producing acetylcellulose, vinyl acetate, acetic anhydride, acetates, etc., and acetoxylation of butadiene using a noble metal catalyst. It is also used as a raw material and a solvent in the production of 1,4-diacetoxybutene-2 by the reaction. Saturated aliphatic carboxylic acids containing unsaturated carboxylic acids as impurities, such as acetic acid containing a small amount of acrylic acid, are converted into acrylic acid by two-stage gas phase catalytic oxidation of propylene (JP-A-56-16184).
No. 1 publication).

If acetic acid containing acrylic acid, which has been conventionally discarded, can be used as a raw material or a solvent in the acetoxylation reaction of butadiene, resources can be effectively used. In this case, acrylic acid inhibits the reaction, There are problems such as a decrease in the activity of the noble metal catalyst, and there is also a risk that the reactor and the piping may be blocked due to polymerization during the reaction. In order to remove impurities such as acrylic acid contained in acetic acid, generally, purification is performed by distillation.

[0004]

However, since the boiling point difference between acetic acid and acrylic acid is small, a high-performance distillation facility is required to separate a small amount of acrylic acid contained in acetic acid by distillation. In addition, the energy cost required for distillation is enormous. Moreover, it is difficult to completely remove acrylic acid even by distillation. An object of the present invention is to provide a method for purifying a saturated fatty acid containing an unsaturated fatty acid as an impurity such as acetic acid by-produced from an acrylic acid production plant by simply treating it.

[0005]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems, and as a result, completed the present invention. That is, the present invention resides in a method for purifying a saturated aliphatic carboxylic acid, which comprises hydrogenating a saturated aliphatic carboxylic acid containing an unsaturated aliphatic carboxylic acid in the presence of a transition metal catalyst. Hereinafter, the present invention will be described in detail.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION

(Raw materials, etc.) The saturated aliphatic carboxylic acid used in the present invention and the unsaturated aliphatic carboxylic acid contained as impurities are not particularly limited, but in the case of acetic acid containing acrylic acid as an impurity, hydrogen is used. The content of acrylic acid in acetic acid to be subjected to the chemical treatment is 0.01 to 10% by weight, preferably 0.05 to 5% by weight. Note that the content of acrylic acid in acetic acid is preferably adjusted to the above range by distillation or the like before hydrogenation.

As the hydrogen, not only high-purity hydrogen such as electrolytic hydrogen, but also hydrogen diluted with an inert gas such as nitrogen or methane which does not adversely affect the reaction such as reformer hydrogen can be used. It preferably contains mole% hydrogen. It is also possible to recycle and reuse the gas once used in the reaction. The amount used is based on 1 mole of unsaturated aliphatic carboxylic acid.
Usually, it is 1 to 20 mol, preferably 2 to 10 mol.

The transition metal used as the catalytically active component is not particularly limited as long as it has an ability to hydrogenate an unsaturated carboxylic acid to a saturated carboxylic acid. Metal is preferred,
For example, nickel, cobalt, palladium, platinum and the like can be mentioned. Among them, palladium and platinum are more preferable.

The catalyst may be a metal formed or a metal supported on a carrier, but a metal supported on a carrier is preferred. The carrier is not particularly limited as long as it is usually used as a catalyst carrier.
Activated carbon, silica, silica-alumina, titania, zirconia are preferred. The amount of the catalyst used depends on the content of the unsaturated carboxylic acid. For example, it is usually 0.1 to 10% by weight, preferably 1 to 10% by weight, based on the saturated aliphatic carboxylic acid containing 1% by weight of the unsaturated aliphatic carboxylic acid. 1 to 5% by weight.

(Reaction method) The method of hydrogenation may be either a batch reaction or a flow-type reaction, and in the case of a flow-type reaction, either a fixed bed type or a suspension tank type may be used. However, a fixed bed flow type reaction is preferable in terms of operation.

In the case of a batch type reaction, for example, hydrogenation of acrylic acid in acetic acid to propionic acid is performed by charging a raw material and a catalyst in a reactor, pressurizing with hydrogen, and performing the reaction while stirring at a predetermined temperature. Can be.

In the case of a flow-type reaction, a reaction tube is filled with a catalyst, raw materials and hydrogen are continuously charged, and the reaction is carried out at a predetermined temperature to similarly convert acrylic acid in acetic acid to propionic acid. can do.

Although the reaction temperature is not particularly limited, it is usually 0.
-200 ° C is preferred, and 30-100 ° C is more preferred. If the reaction temperature is too high, the polymerization of the unsaturated carboxylic acid tends to occur rapidly, which is not preferable. On the other hand, if the reaction temperature is too low, the reaction rate is undesirably slow.

The reaction pressure may be any pressure above normal pressure.
-100 kg / cm ² (0.5-10 MPa) is preferable, and 5-50 kg / cm ² (0.5-5 MPa) is more preferable.

The reaction time is not particularly limited in the case of a batch reaction, but is usually 0.1 to 10 hours, preferably 0.5 to 10 hours.
~ 5 hours. In the case of a flow reaction, the liquid hourly space velocity of the raw material liquid is usually 0.1 to 20 hr ^-1 , preferably 0.5 to 20 hr ^-1 .
〜１０10 hr ⁻¹ .

In the case of a batch reaction, after completion of the reaction, the catalyst can be filtered off from the reaction solution by a conventional method to obtain, for example, the desired acetic acid-free acetic acid. This product can be used as is in harmless acetic acid containing small amounts of propionic acid for applications that do not interfere. The conversion of acrylic acid is usually almost 100%.

[0017]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist.

Example 1 49.5 g of acetic acid, 0.5 g of acrylic acid and 1% by weight were placed in a stainless steel shaking autoclave having an internal volume of 100 cc.
2.0 g of activated carbon catalyst carrying palladium was charged,
The reaction was carried out at a hydrogen pressure of 0.8 MPa and a reaction temperature of 50 ° C. for 1 hour. After the reaction was completed, the reaction solution and the catalyst were separated, and the reaction solution was analyzed by gas chromatography. As a result, acrylic acid was not detected.

Example 2 A reaction was carried out in the same manner as in Example 1 except that the catalyst used was a silica carrier supporting 1% by weight of palladium. After the reaction was completed, the reaction solution and the catalyst were separated, and the reaction solution was analyzed by gas chromatography. As a result, acrylic acid was not detected.

Example 3 A reaction was carried out in the same manner as in Example 1 except that an activated carbon catalyst supporting 1% by weight of platinum was used as a catalyst. After the reaction was completed, the reaction solution and the catalyst were separated, and the reaction solution was analyzed by gas chromatography. As a result, acrylic acid was not detected.

Example 4 A reaction was carried out in the same manner as in Example 1 except that acetic acid (acrylic acid content: 0.065%), which was recovered from an acrylic acid plant and distilled and purified, was used as the acetic acid, and the amount of the catalyst was changed to 1 g. . After the reaction was completed, the reaction solution and the catalyst were separated, and the reaction solution was analyzed by gas chromatography. As a result, acrylic acid was not detected.

Example-5 A stainless steel reaction tube having an inner diameter of 20 mm was charged with 9.0 g of an activated carbon carrier catalyst supporting 1% by weight of palladium.
The reaction was carried out at a reaction pressure of 2.5 MPa and a reaction temperature of 60 ° C. while continuously charging 20 g of acetic acid containing 99% of acrylic acid at a rate of 200 NL per hour. When the reaction solution was analyzed by gas chromatography, the concentration of acrylic acid in the reaction solution was 17 ppm.

Example-6 A reaction was carried out in the same manner as in Example 5 except that the flow rate of acetic acid was 160 g / h, the flow rate of hydrogen was 50 NL / h, the reaction pressure was 0.9 MPa, and the reaction temperature was 50 ° C. When the reaction solution was analyzed by gas chromatography, the concentration of acrylic acid in the reaction solution was 15 ppm.

Example -7 Catalyst 1 on silica carrier supporting 1% by weight of palladium
0.8 g, an acetic acid flow rate of 60 g / h, a hydrogen flow rate of 50 NL / h, a reaction pressure of 0.8 MPa, and a reaction temperature of 5
The reaction was carried out in the same manner as in Example 5 except that the temperature was changed to 0 ° C. When the reaction solution was analyzed by gas chromatography, the concentration of acrylic acid in the reaction solution was 20 ppm.

Example-8 21.8 g of activated carbon carrier catalyst loaded with 1% by weight of platinum
Acetic acid flow rate of 10 g / h and hydrogen flow rate of 50 / h
The reaction was carried out in the same manner as in Example 5 except that NL, the reaction pressure was 0.8 MPa, and the reaction temperature was 50 ° C. When the reaction solution was analyzed by gas chromatography, the concentration of acrylic acid in the reaction solution was 52 ppm.

[0026]

According to the present invention, the unsaturated aliphatic carboxylic acid contained in the saturated aliphatic carboxylic acid can be easily treated. For example, acetic acid containing acrylic acid can be industrially advantageously purified. can do.

Claims (6)

[Claims] 1. A method for purifying a saturated aliphatic carboxylic acid, comprising subjecting a saturated aliphatic carboxylic acid containing an unsaturated aliphatic carboxylic acid to hydrogenation in the presence of a transition metal catalyst. 2. The method according to claim 1, wherein the transition metal is at least one metal selected from Group VIII. 3. The method according to claim 1, wherein the transition metal catalyst is a catalyst in which a transition metal is supported on activated carbon, silica, silica-alumina, titania or zirconia. 4. The method according to claim 1, wherein the transition metal is palladium or platinum. 5. The method according to claim 1, wherein the saturated aliphatic carboxylic acid is acetic acid. 6. The method according to claim 1, wherein the unsaturated aliphatic carboxylic acid is acrylic acid.