JPS5814820B2 - How to remove chromium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for efficiently removing chromium from an organic acid aqueous solution containing chromium.

Organic acid aqueous solutions are often handled industrially using stainless steel equipment.

For example, when recovering these organic acids from acetic acid, acrylic acid, or methacrylic acid aqueous solutions by extraction and distillation, as described in JP-A-50-32116 and JP-A-50-126603, organic acid-containing An example of this is when water and isobutylene are reacted to produce tertiary butyl alcohol.

At this time, depending on the operating conditions, metals such as iron, nickel, and chromium may be eluted due to corrosion of the stainless steel material.

In some cases, it may be necessary to remove these metals for process reasons, to prevent poisoning of the catalyst, or for other reasons.

For example, the above-mentioned JP-A-50-32116 and JP-A-50-1
In the method described in No. 26603, metal ions in a circulating organic acid aqueous solution are removed.

When it is necessary to remove metal ions, anyone would consider using a cation exchange resin to remove the metal by ion exchange.

The present inventors also attempted removal by ion exchange, but
Surprisingly, I encountered a problem in that iron and nickel could be removed, but chromium was hardly removed.

As a result of continuing intensive research to solve this problem, we discovered an unexpected fact and completed the present invention.

In other words, in the case of 100% organic acid, chromium is ion-exchanged relatively well, but in the case of organic acid aqueous solution, chromium is extremely difficult to ion-exchange, and the difficulty of ion-exchange of chromium is significantly influenced by temperature; the higher the temperature, the more ions This makes it easier to exchange.

This fact will be explained in the case of acetic acid.

(1) Relationship between acetic acid concentration and chromium removal Aqueous acetic acid solutions containing various concentrations of chromium acetate (containing 595 ppm of chromium) and acetic acid solutions were prepared and poured into a packed bed of 5 ml of strongly acidic ion exchange resin (IR-200). Table 1 shows the results when the liquid was passed at SV-2 at room temperature (27°C).

The theoretical amount of liquid that can be ion-exchanged is approximately It is 220ml.

From this result, in the case of an aqueous solution with an acetic acid concentration of 85% or less, chromium leaks immediately, and in the case of 100% acetic acid, ion exchange is possible up to 180 ml, which is close to the theoretical amount of 220 ml, and in the case of a 95% acetic acid aqueous solution, chromium leaks immediately. I understand something.

Thus, it is recognized that chromium is extremely difficult to ion-exchange in the case of an aqueous solution of 95% or less acetic acid.

(2) Relationship between temperature and chromium removal An 85% acetic acid aqueous solution containing chromium acetate (containing 595 ppm as chromium) was mixed with a strongly acidic cation exchange resin (IR
-200) Each salinity was passed through a 5 ml packed bed at SV=4.

Table 2 shows the measurement results of the amount of liquid passed until chromium begins to leak.

This result shows that the difficulty of chromium ion exchange is significantly affected by temperature, and the effect is particularly large at temperatures above 55°C.

In particular, when the temperature is 80°C, the exchange capacity of the ion exchange resin (approximately 220 ml in liquid volume) can be exchanged.

This fact was discovered for the first time by the present inventors, and makes it possible for the first time to remove chromium from an aqueous organic acid solution using an ion exchange resin.

In addition, when we investigated the removal of chromium (containing 500 ppIn) from an 85% aqueous solution of methacrylic acid using methacrylic acid as the organic acid, we found that
), 108 ppm of chromium leaks when 10 ml of aqueous solution passes through it, but at 55°C, 24 ppm leaks, 8
At 0°C, less than 2 ppm of chromium was not leaked.

As mentioned above, there are some differences in the temperature effect depending on the type of organic acid, but even in various organic acid aqueous solutions other than acetic acid such as acrylic acid, formic acid, and propionic acid, chromium is hardly ion-exchanged at room temperature, but at temperatures above 55°C. Especially 70℃～8
It was found that at temperatures above 0°C, the rate of chromium ion exchange becomes significantly faster and the amount of chromium ion exchanged also becomes larger, indicating a greater chromium removal effect.

As is clear from the above explanation, the present invention has an organic acid concentration of 9
This method is characterized in that chromium in an organic acid aqueous solution containing 5% or less is removed by treating it at a temperature of 55°C or higher using an ion exchange resin.

In the present invention, the effect of removing chromium is observed at a treatment temperature of 55°C or higher, but the effect becomes more pronounced as the temperature rises, and the effect is particularly large at 70°C or higher.

The organic acid aqueous solution of the present invention is intended for those with an organic acid concentration of 95% or less, and is particularly effective in removing chromium from organic acid aqueous solutions with a concentration of 85% or less.

This will be explained below using examples.

Examples 1-3 85% acetic acid aqueous solution containing chromium acetate (59% as chromium)
containing 5ppIII) with a strongly acidic cation exchange resin (I
R-200) 5ml. 55° C1 7 in the packed bed
The liquid was passed through SV-4 at a temperature of 0°C and 5800C.

Table 3 shows the amount of liquid that passed until chromium began to leak.

Comparative Examples 1 to 3 Experiments similar to Examples 1 to 3 were conducted at temperatures of 30°C, 40°C, and 5
Table 3 shows the results of experiments conducted at 0°C.

As is clear from the above Examples and Comparative Examples, chromium can be easily removed at a temperature of 55°C or higher.

Examples 4 to 7 Acetic acid concentration containing chromium acetate 10%, 50%, 70%, 9
80% 5% acetic acid aqueous solution (595 ppm as chromium)
IR-2 0 0 5 ml (7) S in packed bed at °C
Table 4 shows the results when the liquid was passed through V-2.

Comparative examples 4 to 7 Experiments similar to Examples 4-7 were conducted at a temperature of 27°C.

The results are shown in Table 4.

As is clear from the above Examples and Comparative Examples, the effects of the present invention are recognized even when comparing each acetic acid concentration.

Examples 8-11 Chromium salts of formic acid, propionic acid, acrylic acid and meccrylic acid were each dissolved in an 85% aqueous solution of the corresponding organic acid.

(Concentration as chromium: 95 ppm) This solution was poured into a 5 ml packed bed of IR-200 with SV-4.
The liquid was passed through the tube at a depth of 80°C.

The results are shown in Table 5.

Comparative examples 8 to 11 Experiments similar to Examples 8-11 were conducted at a temperature of 27°C.

The results are shown in Table 5.

From the above Examples and Comparative Examples, it can be seen that the effects of the present invention are remarkable even with organic acids other than acetic acid.

Claims (1)

[Claims] 1. A method for removing chromium, which comprises removing chromium from an organic acid aqueous solution containing chromium with an organic acid concentration of 95% or less by an ion exchange method using a cation exchange resin at a temperature of 55° C. or higher. . 2. The method according to claim 1, wherein the organic acid is one or more selected from formic acid, acetic acid, propionic acid, acrylic acid, and methacrylic acid. 3. The method according to claim 1, wherein the organic acid aqueous solution is an acetic acid aqueous solution containing 85% or less acetic acid. 4 Claim 1, where the temperature is 70°C or higher,
The method described in paragraph 2 or 3.