JPS60130546A - Purification of 1,2-unsaturated carboxylic acid - Google Patents

Abstract

PURPOSE:To obtain the titled extremely high-purity compound efficiently, having no problems as a raw material for high polymer compounds, by treating the titled compound containing aldehydes as an impurity in the presence of a strongly acidic substance and a specific phenolic compound. CONSTITUTION:A 1,2-unsaturated carboxylic acid containing < about 2wt. aldehydes as an impurity, obtained by gaseous phase catalytic oxidation of a corresponding alkene and/or alkenal, from which most of by-products are removed by a well-known purification is treated in the presence of a strongly acidic substance (e.g., sulfuric acid, or sulfonated cation exchange resin) having <=3, preferably <=2pKa and a compound selected from resorcin, pyrogallol, and alpha-naphthol at 20-120 deg.C, preferably at 25-90 deg.C. After the treatment, the unreacted phenolic compound and reaction products of aldehydes are separated in the presence of a polymerization inhibitor, to give a high-purity 1,2-unsaturated carboxylic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for purifying 1,2-unsaturated carboxylic acids.

By using the method of the present invention, aldehydes contained as impurities in 1,2-unsaturated carboxylic acids can be efficiently and easily removed.

BACKGROUND OF THE INVENTION 1,2-unsaturated carboxylic acids such as acrylic acid and methacrylic acid have a wide range of uses as raw materials for the synthesis of polymer compounds.

In recent years, 1,2-unsaturated carboxylic acids such as 1,2-unsaturated carboxylic acids have been industrially produced by gas phase catalytic oxidation reactions of alkenes and/or alkenals. However, 1,2-unsaturated carboxylic acids such as acrylic acid and methacrylic acid obtained by this method contain aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, inbutyraldehyde, acrolein, methacrolein, furfural, and benzaldehyde, and acetone. It contains a wide variety of impurities, such as ketones such as, and acids such as formic acid, acetic acid, and propionic acid.

A considerable amount of these impurities can be separated and removed by repeating common purification operations such as distillation and extraction.

However, even in the process of purification operations such as distillation and extraction, for example, acrolein undergoes thermal change during the purification process of acrylic acid and new aldehydes such as acrolein dimer are formed, and new aldehydes such as furfural, Aldehydes such as benzaldehyde have a boiling point close to that of acrylic acid and are difficult to separate by distillation.
Aldehydes remain as impurities in unsaturated carboxylic acids.

On the other hand, when producing 1,2-unsaturated carboxylic acid esters industrially, the inexpensive 1,2-
A 1,2-unsaturated carboxylic acid ester is often obtained by performing an esterification reaction using a simple distilled unsaturated carboxylic acid as a raw material. Therefore, the above-mentioned impurities such as aldehydes cannot be avoided in this 1,2-unsaturated carboxylic acid ester.

” 1 containing aldehydes as impurities as mentioned above,
2-unsaturated carboxylic acid and /l or its ester,
When used as a raw material for synthesizing a polymer compound, there are many problems such as these impurities causing a polymerization inhibiting effect or an incompatibility effect during the polymerization reaction, and coloring of the obtained polymer.

Prior art 1.2-As a method for removing aldehydes contained as impurities in unsaturated carboxylic acids and/or their esters, there are distillation methods, adsorption using activated carbon and molecular sheets adsorbed with amine compounds (JP-A-Show). 56-189
34), a method of producing a sulfite adduct by addition reaction with sodium bisulfite, addition of amine compound C (see Japanese Patent Publication No. 31087/1987), and amino acids such as glycine (see Japanese Patent Publication No. 14/1983). There are known methods to do this.

However, in the distillation method, for example, as mentioned above in the purification process of acrylic acid, acrolein easily trimerizes during the distillation process to form acrolein dimer, and reacts with water to form β-hydroxypropionaldehyde. On the other hand, furfural and benzaldehyde have a smaller boiling point difference and specific volatility than acrylic acid, and a large number of distillation stages and reflux ratio are required to accurately separate these aldehydes. It is industrially disadvantageous to carry out rectification of polymerizable acid (IJ) under such severe conditions at high temperatures, as it requires special measures to prevent polymerization.

In addition, adsorption methods using activated carbon or the above-mentioned molecular sieves are complicated due to the regeneration operation of the adsorbent, and are not sufficient for removing trace components. The method of forming products has little effect in, for example, 1,2-unsaturated carboxylic acids.

Furthermore, the method of adding amines and amino acids may not be sufficient to remove impurity aldehydes, and amines generally have a polymerization promoting effect on 1,2-unsaturated carboxylic acids and their esters. Furthermore, depending on the amine species, for example, the anhydride of hydrazine is unstable and poses safety problems in terms of process operation and danger.

SUMMARY OF THE INVENTION The present invention improves the above problems and provides a method for almost completely removing aldehydes contained in 1,2-unsaturated carboxylic acids by extremely simple treatments and operations.
According to the method of the present invention, extremely high-purity 1,2-unsaturated carboxylic acid, which is free from problems caused by impurity aldehydes, can be obtained efficiently, economically, and in high yield as a raw material for the synthesis of polymer compounds. can.

That is, the present invention provides a method for purifying a 1,2-unsaturated carboxylic acid containing aldehydes as impurities, in which a strong acidic substance and one or more phenols selected from the group consisting of resorcinol, pyrogallol, and α-narratol are used. Presence of Compound 1. A method for purifying 1,2-unsaturated carboxylic acid is provided, which is characterized by subjecting 2-unsaturated carboxylic acid to a reaction treatment.

3. Detailed Description of the Invention The 1,2-unsaturated carboxylic acid containing aldehydes as an impurity used in the method of the present invention is a C3-6, preferably 03-4, 1,2-unsaturated carboxylic acid, For example, acrylic acid and methacrylic acid.

The above-mentioned 1,2-unsaturated carboxylic acids can be obtained by gas phase catalytic oxidation of the corresponding alkenes and/or alkenals (for example, JP-A-55-102536, JP-A-55-102536;
5-113730, 56-73014, 57-45
130 publications, etc.), and most of the by-products are generally removed by known purification methods, such as distillation and extraction. The 1,2-unsaturated carboxylic acid obtained by this known purification contains less than about 2%, usually less than 1%, of impurity aldehydes.

The method of the present invention is carried out by reacting a 1,2-unsaturated carboxylic acid containing aldehydes as the above-mentioned impurities. It is necessary to carry out the reaction in the presence of one or more phenolic compounds selected from the group consisting of naphthols.

Strong acidic substances used in the method of the present invention include sulfuric acid, hydrochloric acid,
Mineral acids such as nitric acid, organic acids such as para-toluenesulfonic acid (often abbreviated as PTSA), sulfonated cations in which sulfonic acid groups are introduced into styrene-divinylbenzene copolymers, crosslinked polystyrene, phenol-formaldehyde resins, etc. Strongly acidic substances such as ion exchange resins. These strongly acidic substances have a pKa of 3 or less, preferably 2 or less within the range of their acid strength (for pKa values, see Lange, "Handbook of Ch.
emistry ” McGraw-Hi! Book
Co, 5-12 to 5-47 (1967)].

There is no particular restriction on the proportion of these strongly acidic substances used in the reaction treatment, and generally speaking, the larger the amount, the greater the effect. On the other hand, generally 0.01 to 50
wt%, preferably 0.1 to 10 wt%. In addition, when using a solid strong acidic substance such as a sulfonated cation exchange resin in a fixed bed method, it is generally 0.1 to 24 times the processing capacity per hour, preferably 1 to 5 times the processing capacity per hour. It's double.

Furthermore, the phenolic compounds used in the present invention include resorcinol,
Pyrogallol and α-naphtho-, TI/N, can also be used as a mixture of one or more of them. The amount of these phenolic compounds added is 1.2-
Although it varies depending on the concentration of impurity aldehyde present in the unsaturated carboxylic acid and the desired degree of removal, it is generally equivalent to 10 times the mole of the total amount of impurity aldehyde, preferably 3 to 5 times the mole.

The unreacted phenol compound and the aldehyde reactant produced by the reaction with the phenol compound are removed by distillation in the presence of a polymerization inhibitor such as idroginone or hydroquinone monomethyl ether, which is usually used after reaction treatment if necessary. Easily reduced to 1-1 minutes.

The above-mentioned reaction treatment of 1,2-unsaturated carboxylic acids in the presence of a strong acidic substance and a phenolic compound can be carried out in either a batch or continuous manner, but the preferred reaction method is a strong acidic substance. An example of this method is a method in which a solid substance such as a sulfonated cation exchange resin is used and a flow reaction is carried out in a fixed bed.

The reaction treatment temperature is 20 to 120°C, preferably 25°C.
~90°C. The reaction pressure is not particularly limited, but a pressure that maintains a liquid phase is sufficient. Specifically, 1 to 50 a
tm, preferably 1 to 5 atm, are advantageously employed.

The reaction time varies depending on the type of strong acidic substance used, reaction temperature, reaction method, etc., but is usually 0.1
~24 hours, preferably 0.1 to 5 hours is employed.

Experimental Examples Examples 1 to 5 Acrylic acid obtained by separating and removing water from a crude acrylic acid aqueous solution obtained by gas-phase catalytic oxidation reaction of propylene (acrylic acid: 99.5%, furfural: 210 ppm)
, benzaldehyde tso ppm) 150 g
Take r in an Erlenmeyer flask, warm it to 90℃, and add the table below.
The strong acidic substances and phenolic compounds shown in 1 were added in moles 5 times each to the aldehydes (total amount of furfural and benzaldehyde) and reacted for 3 hours.The reaction products were analyzed by gas chromatography, and the concentrations of furfural and benzaldehyde were determined. was as per Table 1.

Table, -1 In the above table, 5K-102 is a sulfonated cation exchange resin manufactured by Mitsubishi Chemical Corporation, trade name Diaion [5K-102J
was previously ion-exchanged into H-type and then water was removed, and 7.5f of each was used.

*mark: para-toluenesulfonic acid: @+if-0,4w
It was used at t%.

** Mark: Commercial special grade reagent (97% product): Concentration 0025wt
It was used in

Comparative Examples 1 to 11 Examples 1 to 11 were used except that the phenol compound shown in Table 2 was used, and Diamond ion "5K-1oJ", which had been ion-exchanged to H type in advance as in Example 1, was used as a strong acidic substance. The reaction treatment was carried out in the same manner as in 5. The results are shown in Table 2.

As is clear from the results in Table 1, when resorcinol, pyrogallol, and α-f7 toll are used as phenolic compounds, the removal of aldehydes is extremely large compared to the various phenolic compounds shown in Table 2. it is obvious.

&-2 Example 6 Methacrylic acid obtained by separating and removing water from a crude methacrylic acid aqueous solution obtained by gas phase contact reaction of isobutylene (methacrylic acid: 99.7%, furfural: 250%)
ppm, benzaldehyde: 200ppm) 10
0 f was placed in an Erlenmeyer flask and heated to 90°C. To this, as a strong acidic substance, a sulfonated cation exchange resin manufactured by Mitsubishi Chemical Corporation (trade name) Diaion rsK-104J was ion-exchanged into H type in advance and then water was removed, 5 gr.
and resorcin were added in an amount of 5 times the mole of aldehydes (total amount of furfural and benzaldehyde), and the mixture was reacted with stirring for 3 hours.

Analysis of the reaction product by gas chromatography revealed traces of both furfural and benzaldehyde.

Example 7 Inner diameter approximately 0.931M, length approximately 50 cpn, internal volume approximately 3
About 3 Qm of the same catalyst as shown in Example 6 was packed in a four-glass back type glass tube, and acrylic acid (purity 99.6 w) containing furfural: 200 ppm, benzaldehyde: 190 ppm, and acrolein dimer: 15 ppm.
resorcinol was added in moles 7 times the total amount of these aldehydes, and a continuous flow reaction was carried out at 60° C. and a residence time of 30 minutes. When the treated solution after the reaction was analyzed by gas chromatography, traces of the above-mentioned aldehydes were found.

Example 8 A reaction was carried out in the same manner as in Example 7 except that α-naphthol was used as the phenol compound, the reaction temperature was 80° C., and the residence time was 2 hours. Analysis of the treated solution after the reaction by gas chromatography revealed traces of impurity aldehydes.

Four liters each of the reaction solutions obtained in Examples 7 and 8 were placed in four flasks and subjected to a conventional distillation operation. A 900-g reaction solution was distilled from the top of the column, and the distillate was analyzed by gas chromatography, and it was found that impurity aldehyde, unreacted phenol (resorcinol or α-naphthol), and these heavy reactants were All of them were traces. From this result, it is clear that extremely high purity acrylic acid can be easily obtained by this operation.

Example 9 Using methacrylic acid used in Example 6, pyrojfo-
A continuous flow reaction was carried out in the same manner as in Example 7, except that 6 times the mole of aldehydes (total amount of furfural and benzaldehyde) was added and the residence time was 1 hour.

When the treated solution after the reaction was analyzed by gas chromatography, traces of all of the above aldehydes were found.

Effects of the Invention As is clear from the above-mentioned Examples and Comparative Examples, according to the method of the present invention, one or more phenolic compounds selected from the group consisting of resorcinol, pyrogallol, and α-naphthol can be used in the presence of a strong acidic substance. , has highly active double bonds and carbonyl groups, hardly reacts with the 1,2-unsaturated carboxylic acids that exist in total, and exists extremely selectively as an impurity under mild conditions. Reacts with aldehydes. From this reaction product, extremely high purity 1,2-unsaturated carboxylic acid can be obtained easily and efficiently.

Patent applicant Mitsubishi Yuka Co., Ltd. Agent: Patent Attorney Hidetoshi Furukawa Agent: Patent Attorney Masahisa Nagatani

Claims (1)

[Claims] (+1 1,2- containing aldehydes as impurities
In a method for purifying an unsaturated carboxylic acid, the 1,2-unsaturated carboxylic acid is subjected to a reaction treatment in the presence of a strong acidic substance and one or more phenolic compounds selected from the group consisting of resorcinol, pyrogallol, and α-naphthol. A method for purifying a 1,2-unsaturated carboxylic acid, characterized by: