JPH08143521A - Purification method of acrylamide aqueous solution - Google Patents

Abstract

PURPOSE: To provide a purification method in which a trace amount of copper can be stably removed from aqueous acrylamide solution prepared by the catalytic hydration of acrylonitrile for a long period of time. CONSTITUTION: An aqueous solution of acrylamide prepared by catalytic hydration of acrylonitrile is treated with an amino-phosphoric acid type neutral or acidic ion-exchange resin. The aqueous solution is about 20-60% in concentration and the copper concentration is about 10-200ppm, thus can be suitably treated by the above-stated operations. The neutral to acidic ion-change resin has a styrene-divinylbenzene copolymer as a matrix and may be in the H-type or Na-type. The treatment is preferably carried out by the column elution technique and the space velocity(SV) is 0.1-20 H, preferably 1-10H.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decoppering method for purifying an aqueous acrylamide solution obtained by a catalytic hydration method of acrylonitrile.

[0002]

BACKGROUND OF THE INVENTION Acrylamide is an industrially useful monomer which is used for the production of acrylamide polymers used as paper strength enhancers, flocculants, etc. and also for various purposes. A method for producing acrylamide by catalytic hydration of acrylonitrile in the presence of a metallic copper catalyst is already well known. However, it is inevitable that a trace amount of copper is eluted in the acrylamide-containing reaction liquid obtained by using this copper-based catalyst. Therefore, when an attempt is made to produce a polymer using an acrylamide aqueous solution as a raw material, the copper dissolved therein inhibits the polymerization reaction, which causes a significant decrease in the commercial value of the acrylamide aqueous solution. Therefore, in order to use the acrylamide aqueous solution obtained from the acrylamide reaction solution as a polymer raw material, it is necessary to remove the dissolved copper. As a method for removing dissolved copper, a method of treating with a strongly acidic cation exchange resin or a method of treating with an iminodiacetic acid type weakly acidic ion exchange resin is adopted.

[0003]

However, since acrylamide is highly reactive, it is extremely difficult to industrially remove copper dissolved in an acrylamide aqueous solution without polymerizing acrylamide. For example, when a strongly acidic ion exchange resin is used, the free acid type (abbreviated as H type) has a large copper removing ability, but since the functional group is strongly acidic, highly reactive acrylamide does not polymerize. Unavoidable. When this is a sodium salt type (abbreviated as Na type), polymerization of acrylamide can be avoided, but copper adsorption ability is poor and sufficient removal performance cannot be obtained. When iminodiacetic acid type weakly acidic ion exchange resins are used, if they are H type, they are weakly acidic and dissociate weakly, resulting in weak copper adsorption ability. Further, if it is Na-type, the functional group is weakly acidic, which causes the disadvantage that Na ions are eluted into the acrylamide aqueous solution.

[0004]

That is, the present invention relates to a method for purifying an aqueous acrylamide solution, which comprises treating an aqueous acrylamide solution obtained by the catalytic hydration method of acrylonitrile with an aminophosphoric acid-type neutral acidic ion exchange resin. It is a thing. The present invention provides a method of removing copper from an aqueous acrylamide solution obtained by a catalytic hydration method of acrylonitrile using a medium acid ion exchange resin of aminophosphoric acid type. By using acidic ion exchange resin in the mold, not only is it possible to remove copper to an extremely low concentration due to its strong copper adsorption capacity, but also because of its moderate acidity, its polymerization even in highly reactive acrylamide. And hydrolysis does not occur, and moreover, from the ion exchange resin, N
It is possible to carry out a very advanced acrylamide purification in which there is no elution of a-ions and the like.

The present invention will be described in detail below. The acrylamide aqueous solution used in the present invention is obtained by a usual catalytic hydration method using acrylonitrile as a raw material. That is, acrylonitrile was charged with water into a pressure-resistant reactor in the presence of a metallic copper catalyst at a temperature of about 70 to 150 ° C.
React for about 3 hours. Since unreacted acrylonitrile remains in the obtained reaction solution, it is usually removed in advance.

The acrylamide concentration of the acrylamide aqueous solution treated in the present invention is not limited, but the acrylamide concentration in the acrylamide aqueous solution usually obtained by the catalytic hydration method is about 20 to 60%, and an acrylamide aqueous solution in this range is suitable. Can be processed. of course,
Even if it is out of this range, it is applicable.

The concentration of copper in the aqueous acrylamide solution treated in the present invention is not limited, but in the catalytic hydration method, the reaction solution usually contains about 10 to 200 ppm of copper, and such an aqueous acrylamide solution is suitable. Can be processed. Of course, it will be easily understood that the present invention can be suitably applied even if the copper concentration is higher or lower than the above.

The medium-acid ion exchange resin used in the present invention is an aminophosphate-type medium-acid ion exchange resin having a styrene-divinylbenzene copolymer as a matrix. For example, Levatit O
C1060 (made by Bayer), Duolite C467
It is commercially available under the names such as (made by Rohm and Haas Co.) and can be preferably used.

The medium acidic ion exchange resin used in the present invention may be H type or Na type. When it is used as a Na type, its adjustment method may be to contact an aqueous solution of caustic soda in excess equivalent to the ion exchange capacity of the resin. If the resin after copper adsorption is treated with a mineral acid, it can be used as H type, and if treated in the same manner with an aqueous solution of caustic soda, it becomes N type.
It can be used as a type again.

The treatment of the aqueous acrylamide solution in the present invention with an aminophosphoric acid type medium acidic ion exchange resin means, in short, to bring the aqueous solution into contact with the ion exchange resin.

In the treatment method of the present invention, the effect can be obtained even by contacting by a batch type suspension method, but a column flow method is usually preferable, and the ion exchange resin is packed in a column and the acrylamide is caused by an ascending or descending flow. A method of contacting an aqueous solution is adopted. There is no limit to the liquid passing speed at that time,
Usually, it is preferable that the SV (superficial velocity) is in the range of 0.1 or more and 20 (Hr ^-1 ) or less, and more preferably 1 or more and 10 or less. The passing temperature is preferably a temperature at which acrylamide does not deteriorate, that is, 60 ° C. or lower, more preferably a lower temperature, but higher than the temperature at which the acrylamide is saturated at that concentration.

[0012]

The present invention will be described in more detail with reference to the following examples. In the following, ppm or% is based on the weight of the aqueous acrylamide solution. [Example 1] Copper obtained by a contact hydration method of acrylonitrile in a glass column having an inner diameter of 15 mm filled with 50 ml of aminophosphate-type medium acidic ion exchange resin Levatit OC1060 (manufactured by Bayer) whose ionic form was adjusted to Na type A 40% acrylamide aqueous solution containing 24 ppm of ions was passed through 30 liters at an SV of 4 (Hr ⁻¹ ) at a downward flow of 30 ° C. The concentration of copper ions in the treatment liquid flowing out from the lower part of the column was 5 ppb or less. No acrylamide polymer was detected in the treatment liquid.

[Example 2] Aminophosphoric acid type medium acid ion exchange resin Levatit OC10 in which the ion type was adjusted to H type
Inner diameter 15 mm filled with 50 ml of 60 (manufactured by Bayer)
A 40% aqueous acrylamide solution containing 28 ppm of copper ions obtained by the catalytic hydration method of acrylonitrile in a glass column of SV of 8 (Hr ^-1 ), downflow, temperature of 30 ° C.
Then, 30 liters were passed. The concentration of copper ions in the treatment liquid flowing out from the lower part of the column was 5 ppb or less. No acrylamide polymer was detected in the treatment liquid.

[Comparative Example 1] Ion-exchange resin is a strongly acidic ion-exchange resin Levatit SP in which the ion type is adjusted to H type.
An aqueous acrylamide solution was treated in the same manner as in Example 1 except that the solution was 112 (manufactured by Bayer). When 2 liters of the aqueous acrylamide solution was treated, the acrylamide polymerized and the column was clogged, making the treatment impossible.

[Comparative Example 2] A strong acid ion exchange resin Levatit S in which the ion type was adjusted to Na type.
An aqueous acrylamide solution was treated in the same manner as in Example 1 except that P112 (manufactured by Bayer) was used. The copper ion concentration in the treatment liquid flowing out from the lower part of the column was 455 ppb.

[Comparative Example 3] An aqueous acrylamide solution was treated in the same manner as in Example 1 except that the ion exchange resin was the iminodiacetic acid type weakly acidic ion exchange resin Levatit TP207 (manufactured by Bayer) whose ion type was adjusted to H type. did. The concentration of copper ions in the processing liquid flowing out from the bottom of the column is 85 pp
It was b. Further, when the inside of the column was inspected after the test, a polymer of acrylamide was found.

[Comparative Example 4] An aqueous acrylamide solution was treated in the same manner as in Example 1 except that the ion exchange resin was the iminodiacetic acid type weakly acidic ion exchange resin Levatit TP207 (manufactured by Bayer) whose ionic type was adjusted to Na type. did. The concentration of copper ions in the processing liquid flowing out from the bottom of the column was 165.
It was ppb.

[0018]

INDUSTRIAL APPLICABILITY According to the present invention, a trace amount of copper can be stably removed from an aqueous acrylamide solution for a long period of time by the catalytic hydration reaction of acrylonitrile, which is extremely advantageous for the industrial production of acrylamide. To give.

Claims (1)

[Claims] 1. A method for purifying an aqueous acrylamide solution, which comprises treating an aqueous acrylamide solution obtained by a catalytic hydration method of acrylonitrile with an aminophosphate-type medium acidic ion exchange resin.