JP3234432B2 - Purification method of acrylamide aqueous solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying an aqueous acrylamide solution obtained by a hydration method of acrylonitrile. The purified acrylamide aqueous solution obtained by the method of the present invention is useful, for example, for producing a high-molecular-weight acrylamide polymer.

[0002]

2. Description of the Related Art Acrylamide is generally used as a metal copper catalyst,
For example, by reacting acrylonitrile with water in the presence of Raney copper or reduced copper, it can be easily obtained as an aqueous solution. Aqueous acrylamide solution obtained by the above reaction is generally unreacted acrylonitrile, impurities contained in raw material acrylonitrile,
It is usually obtained as a product containing reaction by-products, metal ions such as copper eluted from the catalyst, or if necessary, contamination of the device. Of these, unreacted acrylonitrile can be relatively easily separated by an operation such as distillation under reduced pressure.

The above-mentioned aqueous acrylamide solution is generally used when producing an acrylamide polymer having a relatively low molecular weight, for example, a molecular weight of about several hundred thousand, such as used in the field of paper strength enhancers. Is less likely to cause problems.

[0004] However, it is very difficult to obtain an acrylamide polymer having a molecular weight of several million to 10 million or more, for example, as used in the field of polymer flocculants. In other words, an aqueous solution of acrylamide containing impurities, reaction by-products, or metal ions, etc., is intended to obtain an acrylamide polymer suitable for the above-mentioned applications, if the desired molecular weight is not obtained. In addition, since the polymerization completion time is often fluctuated, the production of the acrylamide polymer is affected. Also, the obtained acrylamide polymer is
Poor solubility in water and poor coagulation ability are not obtained, and high quality products cannot be obtained.

[0005] These are caused by reducing substances such as 3,3-nitrilotrispropionamide by-produced during the catalytic hydration reaction of acrylonitrile, or peroxides formed by the reaction of acrylamide produced with oxygen in the air. Various impurities, such as oxidizing substances, are said to influence the polymerization reaction. Further, it is considered that the cause of the deterioration of the water solubility and the decrease of the aggregation ability is a cross-linkable substance such as diacrylimide by-produced during the reaction.

Therefore, it is necessary to remove these impurities in advance prior to polymerization. As a typical method conventionally known, for example, Japanese Patent Application Laid-Open No. 52-91819 discloses an aqueous solution of acrylamide containing a strong acid. There is disclosed a method of treating with a basic cation exchange resin and further treating with a weakly basic anion exchange resin.

[0007]

However, according to the study of the present inventors, the aqueous solution of acrylamide obtained by the above-mentioned hydration method of acrylonitrile is converted into a strongly acidic cation exchange resin and a weakly basic acryl exchange resin. In the method of treating with an anion exchange resin, it is still difficult to sufficiently remove impurities in the acrylamide aqueous solution.

An object of the present invention is to provide a method capable of purifying an aqueous acrylamide solution obtained by a contact hydration method of acrylonitrile to a higher degree than a conventionally known method.

[0009]

Means for Solving the Problems The present inventors have intensively studied and studied a method for removing impurities, reaction by-products, metal ions, and the like in an aqueous acrylamide solution obtained by a contact hydration method of acrylonitrile. As a result, it has been found that the above-mentioned problems can be solved by bringing the aqueous solution of acrylamide into contact with a chelate resin and an anion exchange resin after adding ammonia or organic amines, and further studied to complete the present invention. I came to.

That is, the present invention relates to a copper ion eluted during the reaction, which is obtained by a contact hydration method of acrylonitrile.
After adding ammonia and / or organic amines to an aqueous acrylamide solution containing 10 to 200 ppm of
This is a method for purifying an aqueous acrylamide solution, which is brought into contact with a chelate resin and an anion exchange resin.

According to the method of the present invention, impurities, reaction by-products, metal ions, and the like in an acrylamide aqueous solution can be highly removed. As a result, it becomes very easy to obtain a high molecular weight acrylamide polymer suitable for applications such as a polymer flocculant. Therefore, it is extremely advantageous also in the production of acrylamide polymers or their applications.

The acrylamide aqueous solution used in the method of the present invention is not particularly limited, and an aqueous solution prepared by a wide range of methods can be used. Usually, an aqueous acrylamide solution is synthesized by hydrating acrylonitrile in a liquid phase in the presence of a metallic copper catalyst such as Raney copper or reduced copper. The copper metal catalyst is usually used in a suspension state, and a flow-type or batch-type reaction type is adopted.In the case of producing an acrylamide aqueous solution on a commercial scale, a flow-type stirred tank type reactor is used. It is common to do.

Metallic copper as a catalyst may be one whose main component is copper. For example, a Raney copper catalyst obtained by developing a Raney copper alloy with an aqueous alkali solution, or a copper salt in an aqueous solution of formaldehyde, hydrazine, borohydride or the like. A reduced copper catalyst obtained by reduction with sodium chloride or the like can be used. These metallic copper catalysts generally avoid contact with oxygen or a gas containing oxygen during use as well as before use, in order to suppress the decrease in activity and the generation of by-products during use.

In the hydration reaction of acrylonitrile, the charge of acrylonitrile: water is 50:50 by weight in terms of suppressing side reactions and preventing the formation of a polymer.
Usually, it is in the range of 5 to 95. The reaction temperature can be usually from 30 to 200 ° C, more preferably from 50 to 150 ° C.
Range. Reaction time is usually in the range of 0.5-20 hours,
More preferably, it is in the range of 1 to 3 hours.

Although the concentration of the aqueous acrylamide solution obtained by the reaction naturally depends on the reaction conditions, it is usually 50% by weight.
It is as follows. After the reaction, the catalyst is separated by filtration or the like, and the unreacted acrylonitrile is removed by distillation of the reaction solution under reduced pressure.

In the purification method of the present invention, first, ammonia and / or organic amines are added to an aqueous acrylamide solution, but the organic amines are not particularly limited as long as they are soluble in water, and a wide range of organic amines is used. can do. For example, aliphatic primary amines such as methylamine, ethylamine, propylamine and butylamine; aliphatic secondary amines such as dimethylamine, diethylamine and dipropylamine; trimethylamine;
Aliphatic tertiary amines such as triethylamine and tripropylamine; aliphatic unsaturated amines such as allylamine, diallylamine and triallylamine; aliphatic polyamines such as ethylenediamine, dimethylethylenediamine, tetramethylethylenediamine, propylenediamine and diethylenetriamine; aniline And aromatic amines such as benzylamine; and heterocyclic amines such as imidazole, pyridine, bipyridyl and phenanthroline. These may be used alone or in combination of two or more, and may be used together with ammonia. Further, the used ammonia and / or
Alternatively, the organic amines may be used as they are or in an aqueous solution, and the concentration is not particularly limited.

In the method of the present invention, among the above-mentioned organic amines, ethylenediamine, propylenediamine, diethylenetriamine and the like having a remarkable chelating ability are used.
It is more preferable to use aliphatic polyamines having 2 to 4 carbon atoms.

Preferably, ammonia and / or organic amines are added so that the pH of the aqueous acrylamide solution is 9 to 13. Usually, an aqueous solution of acrylamide obtained by the hydration reaction of acrylonitrile contains about 10 to 200 ppm of copper ions eluted during the reaction, but the added ammonia and / or organic amines are partially distributed to the copper ions. It is thought that the position bond.
Therefore, the added ammonia and / or organic amines are preferably added in a range of 1 to 20 moles, more preferably 1 to 3 moles, based on the contained copper ions. If the amount added is less than 1 mole, the pH of the solution often exhibits 6 to 8, and the ability to decompose diacrylimide or the like in the solution is reduced. In addition, when the amount used exceeds 20 times the mole, the ability to decompose diacrylimide etc. increases, but in the contact with the chelate resin in the next step,
It is not preferable because a load such as adsorption and removal of the added ammonia and / or organic amines is extremely increased.

As a method of adding ammonia and / or organic amines to the aqueous acrylamide solution for treatment, there are flow-type and batch-type methods. It is preferable to use a stirring tank type.

The method of adding ammonia and / or organic amines to the aqueous acrylamide solution is not particularly limited.
For example, it may be added to the gas phase above the liquid, or may be added directly to the liquid. In this case, the ammonia may be either liquid ammonia or an aqueous ammonia solution, and the organic amines may be used as such or as an aqueous solution thereof, and the concentration is not limited.

In the method of the present invention, oxygen or air or the like is added during or after the addition of ammonia and / or organic amines in order to prevent polymerization of the acrylamide aqueous solution and sufficiently oxidize copper ions contained therein. It is highly preferred that oxygen-containing gas such as described above be continuously passed through the aqueous acrylamide solution. When using oxygen or air to perform oxidation, the amount required
It is usually 0.1 to 10 times the volume of the aqueous acrylamide solution to be treated.

When ammonia and / or organic amines are added to the aqueous acrylamide solution to carry out the treatment, the temperature is preferably not higher than 60 ° C. which does not deteriorate acrylamide, and is usually carried out with stirring. In addition, the treatment time is not particularly limited, but in an extremely long treatment, a part of acrylamide is hydrolyzed and becomes acrylic acid or the like. The range is 6 hours.

In the method of the present invention, in the above-mentioned treatment, despite the acrylamide aqueous solution being in an alkaline atmosphere, the remaining copper ions do not precipitate as copper hydroxide or the like, but are dissolved as water-soluble copper complex ions. This is very advantageous since the purification operation can be performed by continuously passing the solution through a chelate resin and an anion exchange resin to the next step and purifying it.

As the chelating resin used in the method of the present invention, any resin can be used as long as it can be exchanged with copper ions in the acrylamide aqueous solution treated as described above. For example, commercially available Diaion CR-10 (manufactured by Mitsubishi Chemical Corporation), Levatit TP
-207 (manufactured by Bayer AG) and Amberlite IRC-718 (manufactured by Tokyo Organic Chemical Co., Ltd.). In the method of the present invention, among these chelate resins, those obtained by introducing an iminodiacetic acid group into a copolymer of styrene and divinylbenzene can be more suitably used, and a very good effect can be expected. . And as counter ion Na
^Although it is not impossible with ⁺ ions or K ⁺ ions, H ⁺ ions are preferably used.

When a chelate resin is used as in the method of the present invention, the ability to capture copper ions and the like, particularly heavy metals, in an acrylamide aqueous solution is excellent, and it is compared with the case where a general cation exchange resin is used. However, since its exchange capacity is large, it is very advantageous when an acrylamide aqueous solution is purified on an industrial scale.

On the other hand, any anion exchange resin can be used as long as it can be ion-exchanged with an organic acid such as acrylic acid which is a reaction by-product. For example, Diaion PA 3 which is a strong basic anion exchange resin
04, PA 306, PA 404, PA 408 (Mitsubishi Chemical Corporation), Lewatit MP 500 (Bayer), and other weakly basic anion exchange resins such as Diaion WA3
0, the same WK20 (Mitsubishi Chemical Corporation), Levatit M
P62 (manufactured by Bayer AG) and the like are commercially available. When a strongly basic anion exchange resin is used in contact with these anion exchange resins, a part of acrylamide may be hydrolyzed to produce a small amount of acrylic acid as a by-product. Therefore, it is more preferable to use a weakly basic anion exchange resin as the anion exchange resin. As the counter ion, it is usually better to use OH ^- ion.

In the operation of purifying the aqueous acrylamide solution in the present invention, it is preferable that the aqueous acrylamide solution is brought into contact with the chelating resin and then with the anion exchange resin. The temperature of the aqueous acrylamide solution when it is brought into contact with them may be lower than the service temperature of the chelate resin and the anion exchange resin, and may be a temperature at which acrylamide does not deteriorate, and is usually preferably 60 ° C or lower.

The contacting operation between the chelating resin and the anion exchange resin in the method for purifying an aqueous acrylamide solution of the present invention is usually carried out by packing the resin into a column or the like and passing the aqueous acrylamide solution through the column. . In this case, it is preferable to adopt a down flow method in which the acrylamide aqueous solution is passed downward from above the packed tower. In addition, the flow velocity is the space velocity (hereinafter, referred to as the space velocity).
SV), usually in the range of ¹ to 50 hr ^-1 , more preferably in the range of 3 to 10 hr ^-1 .

As a method for regenerating the resin used for the purification of the acrylamide aqueous solution, a chelate resin is usually used in the form of 3
This is possible by contacting 塩 酸 10% by weight of hydrochloric acid with an amount of hydrochloric acid 1 to 10 times the total exchange capacity. On the other hand, in the case of a weak base anion exchange resin, it is possible to regenerate by contacting an aqueous solution of 2 to 8% by weight of sodium hydroxide in an amount of 1 to 6 times the total exchange capacity. In any case, the liquid passing rate during the regeneration operation is preferably set in the range of ¹ to 40 hr ^-1 by SV, so that a cation component such as an adsorbed copper ion and an anion component such as an organic acid can be recovered. . These treated ion exchange resins can be used repeatedly.

[0030]

EXAMPLES Hereinafter, the method for purifying an aqueous acrylamide solution of the present invention will be described in more detail with reference to examples. In the following, "%" and "ppm" are all by weight.

Production Example 1 Raney copper catalyst (trade name: CDT-60: manufactured by Kawaken Fine Chemical Co., Ltd.) was placed in a four-neck flask having an internal volume of 1 liter.
g of acrylonitrile, 250 g of acrylonitrile in which nitrogen gas was previously introduced and nitrogen gas was passed through to remove dissolved oxygen.
Then, 250 g of ion-exchanged water was added and reacted at 70 ° C. for 2 hours to produce 81 g of acrylamide. After the catalyst was separated from the reaction solution by filtration with a filter, the catalyst was distilled under reduced pressure and concentrated to obtain a crude acrylamide aqueous solution. The acrylamide concentration of this aqueous solution was 33%, the residual concentration of acrylonitrile was 0.01% or less, and the copper ion concentration was 70 ppm.

Production Example 2 In a four-necked flask having an inner volume of 1 liter, 15 reduced copper catalyst was added.
g of acrylonitrile, 250 g of acrylonitrile in which nitrogen gas was previously introduced and nitrogen gas was passed through to remove dissolved oxygen.
And 250 g of ion-exchanged water and react at 80 ° C. for 3
75 g of acrylamide was produced. After the catalyst was separated from the reaction solution by filtration with a filter, the catalyst was distilled under reduced pressure and concentrated to obtain a crude acrylamide aqueous solution. The acrylamide concentration of this aqueous solution is 31%, and the residual concentration of acrylonitrile is
The copper ion concentration was less than 0.01% and the copper ion concentration was 75 ppm.

Example 1 245 g of the crude acrylamide aqueous solution obtained in Production Example 1
Was placed in a 0.5-liter four-necked flask equipped with a stirrer, an oxygen gas inlet tube, and a thermometer, and ethylenediamine was added to the flask so that the concentration became 140 ppm. The mixture was agitated at 20 ° C. for 5 hours with aeration at / hr. The number of rotations of the stirrer was 300 rpm, and the solution in this case had a pH of 9 to 11 and exhibited a blue-violet color. Next, the above solution is passed through a column filled with an H-type chelate resin of Levatit TP-207 (trade name, manufactured by Bayer) at SV = 3 hr ^-1 to remove copper ions, ethylenediamine and other cationic components. Operation was performed. As a result, the copper ion concentration in the solution by the chelate titration method using EDTA was 0.05 ppm or less,
The concentration of ethylenediamine determined by gas chromatography was 1 ppm or less. Next, this solution was continuously passed through a column filled with an OH-type weakly basic anion exchange resin of Levatit MP-62 (trade name; manufactured by Bayer K.K.), and an anionic component such as acrylic acid was added. Was removed. The presence or absence of the polymer in the contact operation with the ion exchange resin was confirmed by mixing 45 ml of methanol with 5 ml of the above treated aqueous solution, but no formation of an acrylamide polymer was observed.

Polymerization evaluation test Using the acrylamide aqueous solution obtained by the above treatment,
A polymerization reaction was performed by the following method, and a test for evaluating the obtained polymer was performed. First, pure water was added to 240 g of the aqueous acrylamide solution obtained in Example 1 to adjust the total amount.
After 980 g, put it in a 2 liter reaction vessel equipped with a nitrogen inlet tube and a thermometer.
The solution was passed for 1 hour at a flow rate of 10 liter / min to remove dissolved oxygen in the solution. Next, 10 g of a 0.03% aqueous ammonium persulfate solution and 10 g of a 0.03% aqueous ferrous ammonium sulfate solution were added thereto.
g was added at about the same time. About 1.5 hours after these additions, the reaction temperature peaked at 90 ° C. After leaving for 1 hour from that point, the produced polymer was taken out. The obtained polymer was crushed by a meat chopper, dried at 85 ° C. for 2 hours, and further crushed by a crusher to obtain a powdery acrylamide polymer. This was sieved and 30 to 60 mesh was sampled and used as a test sample.

Evaluation method of acrylamide polymer: The obtained acrylamide polymer was subjected to a water solubility test,
The molecular weight measurement and the aggregation performance test were performed as follows. Water solubility test: 400 ml of pure water was put into a 500 ml beaker, and 0.4 g of the obtained polymer powder (weight of the pure polymer excluding water) was added thereto while stirring with a screw-type stirring blade at room temperature. After stirring at 400 rpm for 1.5 hours,
The mixture was filtered through a 150-mesh net, and the presence or absence of insoluble components was visually determined. In addition, the result of the determination was shown as follows. ············································· Large amount of insoluble matter; Was added to a concentration of 1N, and the viscosity was measured using an Ubbelohde viscometer, and the viscosity was calculated from the value. Coagulation ability; coagulation ability is sulfuric acid band in kraft pulp wastewater
400 ppm was added, and 1 ppm of polyacrylamide was added at pH 6, and the mixture was coagulated by a conventional method using a jar tester. The size of the floc generated at this time was determined and evaluated. In addition, the result of the determination was shown as follows.・ ・ ・: Flock diameter: 3 to 4 mm Δ: Flock diameter: 1 to 3 mm ×: Flock diameter: less than 1 mm The results are shown in Table 1.

Example 2 The procedure of Example 1 was repeated, except that 1.5 g of a 25% aqueous ammonia solution was added instead of ethylenediamine. The pH of the solution in this case is 10-12,
The solution exhibited a blue-violet color, and no formation of an acrylamide polymer was observed at all in the presence or absence of polymer formation in the solution after the contact treatment operation with the chelate resin and the anion exchange resin. A polymerization test similar to that of Example 1 was performed on the obtained acrylamide aqueous solution. Table 1 shows the results
Shown in

Example 3 The procedure of Example 1 was repeated except that ethylenediamine was added to a concentration of 70 ppm and 0.3 g of a 25% aqueous ammonia solution was added. In this case, the pH of the solution is 9 to 12, the solution exhibits a blue-purple color, and the formation of an acrylamide polymer does not occur at all even in the presence or absence of polymer formation in the solution after the contact treatment operation with the chelating resin and the anion exchange resin. I was not able to admit. A polymerization test similar to that of Example 1 was performed on the obtained acrylamide aqueous solution. Table 1 shows the results.

Example 4 The procedure of Example 1 was repeated, except that diethylenetriamine was added in place of ethylenediamine to a concentration of 140 ppm. The p of the solution in this case
H was 9 to 10, and the solution exhibited a bluish purple color. The formation of a polymer in the solution after the contact treatment operation with the chelate resin and the anion exchange resin did not show any formation of an acrylamide polymer at all. A polymerization test similar to that of Example 1 was performed on the obtained acrylamide aqueous solution. Table 1 shows the results.

Example 5 Using the crude acrylamide aqueous solution obtained in Production Example 2 above, the operation was carried out exactly in the same manner as described in Example 1, and the obtained acrylamide aqueous solution was subjected to the same polymerization test as in Example 1. Was performed. Table 1 shows the results.

Comparative Example 1 The procedure of Example 1 was repeated except that no ethylenediamine was added. A polymerization test was similarly performed on the obtained acrylamide aqueous solution. Table 1 shows the results.

Comparative Example 2 The crude acrylamide aqueous solution obtained in Production Example 2 was
As in Comparative Example 1, a purification treatment operation was performed by directly contacting the resin with a chelate resin and an anion exchange resin. A polymerization test was similarly performed on the obtained acrylamide aqueous solution. Table 1 shows the results.

[0042]

[Table 1]

[0043]

According to the method of the present invention, an aqueous solution of acrylamide obtained by the catalytic hydration of acrylonitrile is added with ammonia and / or organic amines and then brought into contact with a chelate resin and an anion exchange resin for purification treatment. It is clear that it can be purified to a higher degree than conventionally known methods. Also, when the acrylamide polymer is almost insoluble in water,
Moreover, a polymer having a molecular weight of about 11 to 12 million can be easily obtained.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Susumu Oyama 1900 Togo, Mobara City, Chiba Prefecture Inside Mitsui Toatsu Chemicals Co., Ltd. (72) Inventor Shigeo Watanabe 1900 Togo, Togo, Mobara City, Chiba Prefecture Mitsui Toatsu Chemicals Inc Examiner Takeshi Nimi (56) References JP-A-57-7452 (JP, A) JP-A-52-93712 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07C 231/24 C07C 233/09

Claims (4)

(57) [Claims] A copper ion eluted during a reaction obtained by a contact hydration method of acrylonitrile is 10 to 200 ppm.
A method for purifying an aqueous acrylamide solution, comprising adding ammonia and / or organic amines to an aqueous solution of acrylamide contained therein and then contacting the aqueous solution with a chelate resin and an anion exchange resin. 2. The method according to claim 1, wherein the ammonia and / or the organic amine is ammonia, an aliphatic primary amine, an aliphatic secondary amine, an aliphatic tertiary amine, an aliphatic polyamine, an aromatic amine, or a heterocyclic ring. The purification method according to claim 1, wherein the compound is at least one member selected from the group consisting of formula amines. 3. During or after addition of ammonia and / or organic amines to the aqueous acrylamide solution,
3. The purification method according to claim 1, wherein oxygen or an oxygen-containing gas is passed through the aqueous solution. 4. The purification method according to claim 1, wherein the chelate resin is obtained by introducing an iminodiacetic acid group into a copolymer of styrene and divinylbenzene.