JPS60193942A - Method for recovering carboxylic acids contained in organic solvents - Google Patents

Abstract

PURPOSE:To recover a carboxylic acid, easily and economically, in high yield, and to reutilize the acid as a resource, by collecting the carboxylic acid existing in an organic solvent using a specific polymeric compound as a collecting material, and desorbing the collected acid with a desorbent such as an alcohol, etc. CONSTITUTION:A 1-30C aliphatic, aromatic or alicyclic mono-, di- or tricarboxylic acid is collected by using a collecting material comprising a polymeric compound having porous or gel-type crosslinked structure, containing a weakly basic functional group such as pyridine nucleus, aliphatic tertiary amine, etc., e.g. a copolymer of a vinylpyridine compound and a monomer having plural ethylenic unsaturated groups such as divinylbenzene. The collected acid dissolved in an organic solvent such as aliphatic or aromatic hydrocarbon, a fatty acid ether, a carboxylic acid ester, etc. is recovered by using a desorption agent selected from alcohol, ketone, carboxylic acid ester, an alkaline aqueous solution and an aqueous solution of inorganic mineral acid.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering carboxylic acids contained in an organic solvent using a material whose main component is a polymer compound having a weakly basic functional group and a crosslinked structure. It is.

In recent years, with the development of industry, carboxylic acids have been used in a wide range of fields as raw materials for paints, plasticizers, agricultural chemicals, surfactants, dyes, medicines, etc. Therefore, there is a need for an economical and industrial collection and recovery method for separating or recovering various carboxylic acids. Particularly in chemical processes that use organic solvents, an inexpensive method for recovering carboxylic acids from organic solvents is an important issue in terms of resource conservation.

As a method for recovering carboxylic acids contained in an organic solvent, a method is known in which the carboxylic acids are brought into contact with a strong alkaline aqueous solution and extracted into an aqueous layer as an alkali carboxylic acid salt.

In this method, water or alkali may be mixed into the organic solvent after extraction of the carboxylic acid, or conversely, the organic solvent may be mixed into the aqueous layer, causing problems in wastewater treatment, so it is not a desirable method.

There is also a method of adsorption and recovery of carboxylic acids using an ion exchange resin. Although various reports have been made regarding this method, most of them relate to a method for recovering carboxylic acids from an aqueous solution. For example, JP-A-57-212136 describes the adsorption of carboxylic acids with an ion exchange resin having a pyridine skeleton structure, but only describes a method for recovering carboxylic acids from an aqueous solution containing carboxylic acids. In particular, there has been little research into the recovery of carboxylic acids in poorly water-soluble solvents with low polarity, or the recovery of organic carboxylic acids with a large number of carbon atoms. This lack is due to the fact that in the case of organic solvents, adsorption under a completely different atmosphere from that of aqueous media must be taken into account.

For example, hydrophobic bonds that function effectively in adsorption in aqueous media cannot be expected in organic solvents. In addition, the control operation of the ion exchange capacity, which determines the adsorptivity for ion exchange resins, differs in organic solvents.

The present inventors have completed the present invention as a result of intensive study on these points.

In the present invention, when recovering carboxylic acids contained in an organic solvent, the carboxylic acids are collected using a material whose main component is a polymer compound having a weakly basic functional group and a crosslinked structure, and then The present invention relates to a method for recovering carboxylic acids using a desorbent selected from the group consisting of alcohols, ketones, carboxylic acid esters, aqueous alkaline solutions, and aqueous inorganic mineral acid solutions.

The weakly basic functional group in the present invention refers to a pyridine nucleus and an aliphatic tertiary amino group.

However, low-molecular-weight compounds having weakly basic functional groups require special equipment for separation from organic solvents due to their solubility in organic solvents.

Additionally, there is a risk of secondary pollution occurring.

The present inventors have discovered the use of a polymer compound having a weakly basic functional group as a collection material in consideration of the above points. That is, such polymeric compounds can be produced by polymerizing monomers having both a weakly basic functional group and an ethylenically unsaturated group, or by introducing a compound having a weakly basic functional group into an appropriate polymeric compound. .

It is convenient to use vinyl monomers as monomers for this purpose. For example, the vinyl monomer is 2
-vinylpyridine, 4-vinylpyridine, 2-vinyl-
Vinylpyridines such as 5-ethylpyridine and 2-vinyl-6-methylpyridine, and the general formula % Formula % Also, R and R' represent a hydrogen atom or an alkyl group.

) Compounds shown, such as N,N-dimethylaminomethylstyrene, N,N-dimethylaminepropyl methacrylate, N,N-dimethylaminopropyl acrylate,
N,N-dimethylaminopropyl methacrylic acid amide,
Examples include N,N-dimethylaminopropylacrylic acid amide, and other examples include N,N-diaminoethylaminomethylstyrene and aminoethylaminoethylaminomethylstyrene.

Examples of homopolymers include poly(2-vinylpyridine), poly(4-vinylpyridine), poly(2-vinyl-6-methylpyridine), and poly(N,N-dimethylaminopropylmethacrylic amide). Examples of this low copolymer include the above monomer and styrene,
Examples include copolymers of vinyltoluene, acrylonitrile, acrylic esters, and methacrylic esters.

Through further research, the present inventors discovered that by imparting a crosslinked structure to a polymer compound having a weakly basic functional group by an appropriate method, the rate of capturing carboxylic acids can be increased and capture selectivity can be imparted. In addition to the above effects, it has been found that from an industrial point of view, there are advantages such as improved mechanical strength.

Therefore, for the reasons mentioned above, it is extremely important to use a polymer compound that retains a weakly basic functional group in the polymer skeleton and has a crosslinked structure as a material for collecting carboxylic acids.

The polymer compound used in the present invention may have either a gel type structure or a porous structure.

Known manufacturing methods can be used to manufacture the polymer compound of the present invention, such as ionic polymerization and radical polymerization.

Furthermore, as a method for imparting a crosslinked structure, techniques commonly used in polymer synthesis can be used. For example, there is a method of copolymerizing heptamers having multiple ethylenically unsaturated groups such as divinylbenzene, divinyl phthalate, and ethylene glycol diacrylate as a crosslinking agent during polymerization. Of course, ethyl contained in divinylbenzene etc. Even if vinylbenzene is present, it can be used satisfactorily as a crosslinking agent.

A polymer compound having a porous structure can be synthesized by using a precipitant. Any precipitant may be used as long as it dissolves the nitrate, does not dissolve the polymer, and does not participate in polymerization. Examples include l-butanol 1 and 2.
-4 carbon atoms such as butanol, 2-nitylhexanol
or saturated aliphatic hydrocarbons having 5 or more carbon atoms such as hebutane and isooctane; aromatic hydrocarbons such as benzene, toluene, and ethylbenzene; carboxylic acid esters having 6 or more carbon atoms; -404
31; and inert micelle-forming solubilizers that are soluble in monomers and insoluble in copolymers as shown in Japanese Patent Publication No. 47-40315. Preferably, such precipitants are used in an amount of 5 to 60% by weight based on the monomer.

The polymer compound thus obtained has a molecular weight of 1
10,000 or more, the degree of crosslinking is 1 per 1 to 20 molecules, and the appearance can range from powder to granules. Needless to say, it needs to be designed.

The polymer compound of the present invention can of course be used alone as a collection material, but if necessary, it can also be used with a suitable carrier.For example, synthetic resins such as vinyl chloride, synthetic fibers,
It can be used by being supported on a carrier such as activated carbon, silica gel activated alumina, or zeolite and molded into a suitable shape.

Examples of the organic solvent of the present invention include, but are not limited to, aliphatic hydrocarbons, aromatic hydrocarbons, aliphatic ethers, halogenated hydrocarbons, and carboxylic acid esters.

Next, the carboxylic acids that can be collected using the polymer compound of the present invention are explained below.

Namely, formic acid, acetic acid, propionic acid, valeric acid, caproic acid, caprylic acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, valmitic acid, stearic acid, nonadecylic acid, acrylic acid, methacrylic acid, crotic acid,
Monocarboxylic acids having 1 to 3 carbon atoms such as benzoic acid, toluic acid, and phenylacetic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, superric acid, azelaic acid, sebacic acid, maleic acid, Examples include dicarboxylic acids having 1 to 30 carbon atoms such as fumaric acid, phthalic acid, inphthalic acid and terephthalic acid, and tricarboxylic acids such as citric acid, aconitic acid and trimellitic acid. Other oxycarboxylic acids such as glycolic acid, tartaric acid, malic acid, lactic acid, hydroxycaproic acid, salicylic acid, and mandelic acid, and ketocarboxylic acids such as acetoacetic acid and levulinic acid are also effective.

The carboxylic acids collected in the polymer compound of the present invention include aliphatic alcohols such as methanol, ethanol, and propatool, aliphatic ketones such as acetone and methyl ethyl ketone, or methyl acetate, ethyl acetate, acetic ester, dimethylformamide, and N-methyl It has the characteristic that it can be very easily desorbed with solvents such as carboxylic acid amides such as pyrrolidone. Such a desorbent is appropriately selected depending on the carboxylic acids collected.

When using alcohol, ketone, etc. as a desorbent, any agent can be used as long as it dissolves the collected carboxylic acids, but it is preferable to use one that has a high solubility of the carboxylic acids, especially for desorbing carboxylic acids having 10 or more carbon atoms. In this case, it is preferable to use an organic solvent that dissolves carboxylic acids. In addition, when using an organic solvent as a desorbent, it is more effective to use a protic solvent such as methanol or ethanol from the viewpoint of weakening the bond between the carboxylic acid and the weakly basic functional group. Moreover, the desorbed carboxylic acids can be reused as resources.

Naturally, inorganic mineral acids such as hydrochloric acid and sulfuric acid, or alkaline aqueous solutions such as sodium hydroxide and potassium hydroxide can also be used for desorption.

In carrying out the present invention, the method for collecting carboxylic acids using the polymer compound of the present invention is a common method.

For example, fixed bed, moving bed, fluidized bed distribution system, or
Methods such as the batch method can be used.

By carrying out the present invention, carboxylic acids in an organic solvent can be adsorbed very efficiently, and the organic acids can be efficiently and easily recovered from the adsorbed resin, making the present invention extremely useful.

The present invention will be explained using examples as follows.

Example 1 A mixture consisting of 40 g of commercially available 4-vinylpyridine purified by vacuum distillation, 6 g of divinylbenzene, 54 g of styrene, and Ig of benzoyl peroxide was placed in a flask and kept at 50"0 for 3 days to reduce the solid weight. Obtained union.

This polymer was finely crushed, then thoroughly washed with 500 ml of methanol and kept at 65°C. After washing, the polymer was thoroughly washed with water and dried in a dryer for 6 hours to yield 90g (140ml
) was obtained.

Using 5g (approximately 7.7ml) of each of these polymers, Table 1
100 ml of a mixed solution of the organic compound and carboxylic acid shown in 1 was brought into contact with each other in a batch for 2 hours, and the polymer was filtered off, and the carboxylic acid concentration in the solution was analyzed. The results are shown in Table-1.

In addition, the filtered polymer was brought into contact with the desorbent 501 shown in Table 1 in a batch for 2 hours, and the concentration of carboxylic acid or sodium carboxylate in the desorption solution was analyzed and shown in Table 1. The desorption rate was obtained.

Implementation 4N-2 Weakly basic anion exchange resin rKE manufactured by Koei Chemical Industry Co., Ltd.
X2 l 2J l 3g (approx. 20m1) to 1cmφ
A benzene mixed solution containing 0.6% acetic acid was packed in a ×75c glass column at a rate of 20 ml/)Ir.
The solution was passed for 0 hours. When the concentration of acetic acid in the effluent after 10 hours was measured, it was found to be a 500 PP layer, and the amount of adsorption to the resin was 1.19 g.Next, the flow of liquid was stopped, and methanol as a desorbent was added at a rate of 20 μl/Hr. The solution was passed at a high speed for 3 hours. The amount of acetic acid in the obtained desorption solution was 1.9%, and the desorption rate was 85.
．． It was 8%. When the carboxylic acids shown in Table 2 were investigated in the same manner, the results shown in Table 2 were obtained.

Claims (1)

[Claims] 1. When recovering carboxylic acids contained in an organic solvent, a polymer compound having a weakly basic functional group and a crosslinked structure is used to collect the carboxylic acids, and then alcohol A method for recovering carboxylic acids using a desorbent selected from the group consisting of , ketones, carboxylic acid esters, aqueous alkaline solutions, and aqueous inorganic mineral acids. 2. The method according to claim 1, wherein the carboxylic acid is an aliphatic, aromatic, or alicyclic carboxylic acid having 10 or more carbon atoms. 3. The organic solvent is an aliphatic hydrocarbon, aromatic hydrocarbon, fatty acid ether, or halogenated hydrocarbon. The method according to claim 1, which is a carboxylic acid ester or a mixture thereof. 4. The method according to claim 1, wherein the carboxylic acids are monocarboxylic acids. 5. The method according to claim 1, wherein the carboxylic acid is a dicarboxylic acid. 8. The gong force method according to claim 1, wherein the carboxylic acids are tricarboxylic acids. ? The method according to claim 1, wherein the polymer compound is a compound having a porous structure. 8. Claim 1 in which the polymer compound has a gel structure
The method described in section. 8. The method according to claim 1, wherein the polymer compound is a copolymer of vinylpyridines and a monomer having a plurality of ethylenically unsaturated groups. 10. The method according to claim 9, wherein the septamer having a plurality of ethylenically unsaturated groups is divinylbenzene. 11. The method according to claim 1, wherein the polymer compound is supported on a carrier.