JP3692497B2 - Method for recovering dimethyl sulfoxide - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for recovering DMSO from a mixture of dimethyl sulfoxide (hereinafter referred to as DMSO) and monoethanolamine (hereinafter referred to as MEA).
[0002]
[Prior art]
Conventionally, DMSO has been widely used industrially as a reaction solvent for pharmaceutical and agrochemical intermediates, a special cleaning agent for electronic materials, and the like. In particular, a mixture of DMSO and MEA is one of excellent special release agents for electronic materials. DMSO is also used as a rinsing liquid in the rinsing process after peeling using the above-mentioned release agent. In recent years, the amount of these used has increased remarkably, and the used liquid generated there has been treated. The problem has been highlighted as a new issue. The mixture of DMSO and MEA used for such applications is completely separated from DMSO and MEA only by ordinary vacuum distillation, and it is difficult to recover only DMSO. There is also a method for separating DMSO and MEA by repeating the crystallization operation (JP-A-7-118223), but at present, the mixture of DMSO and MEA is usually discarded as industrial waste.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for efficiently and efficiently recovering DMSO from a mixture of DMSO and MEA that is currently used for electronic materials that are usually discarded as industrial waste. Specifically, the aprotic polar organic solvent is low toxic, and optionally mixed with water or mixed with an organic solvent such as MEA at an arbitrary ratio. A method for recovering DMSO at low cost and efficiently from a mixture containing DMSO, which is widely used industrially as a reaction solvent, synthetic reagents, electronic materials, and other stripping solutions, and can be reused especially for electronic materials An object of the present invention is to provide a method for recovering DMSO having such a high purity and low metal content.
[0004]
[Means for Solving the Problems]
The present invention aims to achieve the above object, and a method for recovering DMSO from a mixture containing DMSO and MEA, wherein the mixture is neutralized and distilled under reduced pressure. More specifically, in a method for separating and recovering DMSO from a mixture containing DMSO and MEA, wherein the DMSO content is higher than the MEA content, the mixture is treated with sulfuric acid and MEA at 0.8-1. Neutralize using 5 equivalents, MEA was fixed in the mixture in the form of sulfate, distilled under reduced pressure to distill the liquid mainly composed of DMSO, then cation exchange resin alone A DMSO and MEA mixture characterized by passing through a used ion exchange column, removing a trace amount of MEA in the liquid, performing rectification, and recovering DMSO having a pH of 7.0 Of DMSO from
[0005]
Then, according to the DMSO recovery method of the present invention, DMSO is recovered as having a high purity and a low metal content such that it can be recycled for processing electronic materials. That is, only DMSO can be recovered by distillation with high purity and low metal content.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a method for recovering DMSO from a mixture of DMSO and MEA. In the present invention, there are several preferable conditions as described below for recovering DMSO from the mixture, cost, etc. .
[0007]
The composition of the DMSO and MEA mixture in the present invention may be used when the DMSO content is higher than that of MEA, although the DMSO content may be the same as or lower than that of MEA. Specifically, the MEA content is, for example, 30% by weight or less, more preferably 10% by weight or less. Such mixtures include both water-containing and non-water-containing mixtures, and some of them contain a small amount of organic substances in addition to DMSO and MEA.
[0008]
A typical example of the mixture of DMSO and MEA in the present invention includes a used stripper after processing an electronic material, etc., but the mixture of the present invention is not limited to this, and may be a mixture used for other purposes. Good. The present invention can also be applied to a mixture that is not defined as a spent liquid, that is, a mixture of only DMSO and MEA.
[0009]
In this case, the composition of the liquid is not particularly limited, but is preferably the same as the MEA concentration in the used liquid, and the MEA is applied at 30% by weight or less, more preferably 10% by weight or less.
[0010]
In the DMSO recovery method of the present invention, MEA in the mixed solution as described above is neutralized and distilled. The neutralization, the non-volatile-free machine acids, for reasons such as that handlers of the can remaining after neutralization distillation is easy and need use sulfuric acid. The amount of sulfuric acid used is added at this time is 0.8 to 1.5 times equivalent of MEA present in the mixture, good Mashiku is suitably 1.0 to 1.5 equivalents. In this case, when the amount of sulfuric acid is less than 0.8 times equivalent, MEA is not sufficiently neutralized and distilled. Further, if 1.5 times more than equivalent weight, leading to cost-up.
[0011]
The neutralization here is a reaction represented by the following reaction formulas (1) and (2).
[0012]
HOCH ₂ CH ₂ NH ₂ + H ₂ SO ₄ → HOCH ₂ CH ₂ NH ₃ ⁺・ HSO ₄ ^~・ ・ ・ (1)
2HOCH ₂ CH ₂ NH ₂ + H ₂ SO ₄ → (HOCH ₂ CH ₂ NH ₃ ⁺ ) ₂・ SO ₄ ^{2 ~}・ ・ ・ （2）
In the neutralization distillation, the can temperature is usually 130 ° C. or lower, more preferably 110 ° C. or lower. The pressure in the can at this time is preferably 14.2 kPa or less and 6.7 kPa or less, respectively. An excessively high temperature or pressure is not preferable because the decomposition of DMSO is remarkably accelerated.
[0013]
In the present invention, a liquid mainly composed of DMSO obtained by neutralizing distilled in this manner, it removes the M EA is reliable, ion exchange treatment for reasons such as processing speed is relatively fast is Done . The ion exchange treatment is preferably performed by passing a liquid mainly composed of DMSO through the ion exchange column. At this time, as the ion exchange resin to be packed in the column, since MEA becomes a cation, a cation is used. It uses the exchange resin alone.
[0014]
The ion exchange may be either a fluidized bed type or a fixed bed type, but a fixed bed type is preferred. The treatment temperature is preferably room temperature.
[0015]
The amount of liquid flow is about 100 to 150 times the amount of wet resin, but this amount depends greatly on the exchange capacity of the resin and the MEA concentration in the liquid to be treated. It is important to analyze the MEA concentration in the liquid to be treated before the treatment.
[0016]
Further, in the present invention, it rectification of liquid after the ion exchange process. The operation conditions at this time are as follows. Specifically, for example, as described in JP-A-9-278743, the can temperature in rectification is usually 130 ° C. or lower, more preferably 110 ° C. or lower. The pressure in the can is preferably 14.2 kPa or less and 6.7 kPa or less, respectively. An excessively high temperature or pressure is not preferable because the decomposition of DMSO is remarkably accelerated.
[0017]
Further, in order to bring the DMSO purified by distillation and recovered to a level that can be used for processing electronic materials, it is preferable to use a corrosion-resistant material as the material of the equipment in contact with the liquid, particularly the vaporization section. When the corrosion-resistant material is used in this way, the metal content such as iron contained in the recovered DMSO can be kept down to 10 ppb or less.
[0018]
Furthermore, in order to prevent thermal decomposition of DMSO during distillation, it is important to keep the pH of the crude liquid mainly composed of DMSO used for distillation alkaline. A preferable pH is 8 or more, and a more preferable pH is selected within the range of pH 9-12.
[0019]
Examples of the substance used when the pH of the crude liquid is adjusted to alkaline include alkali metal and alkaline earth metal hydroxides or carbonates, and sodium hydroxide is particularly preferably used.
[0020]
The DMSO recovered in the present invention is suitably used as a reaction solvent and a synthetic reagent for intermediates for medical and agricultural chemicals as well as for electronic material processing.
[0021]
【Example】
Hereinafter, examples of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to these examples.
[0022]
FIG. 1 is a model diagram for explaining the outline of a recovery apparatus used in recovery of DMSO of the present invention.
[0023]
In FIG. 1, 4000 g of a mixed solution containing 92% DMSO, 4.5% MEA, and 3.5% water is supplied to the evaporator 1 through the pipe 7, and 176 g of 98% sulfuric acid is separately supplied from the pipe 6. It supplied to the evaporator 1 through the piping 7, neutralized in the evaporator 1, and maintained the internal pressure of the can at 4.0 kPa, and distilled until the can temperature reached 120 ° C. Next, the fraction obtained by introducing the distillate into the condenser 2 via the pipe 8 and condensing it with the condenser 2 was 3200 g, of which DMSO was 95.6%. This fraction is supplied from the pipe 9 to the ion exchange column 3, and after removing MEA remaining at ppm level in the fraction, it is supplied to the distillation column 4 through the pipe 10 and dehydrated and rectified at a can internal pressure of 4.0 kPa. Was done. As a result, 2840 g of DMSO was obtained. The recovered DMSO had a pH of 7.0, a Na content of 2 ppb, a Fe content of 1 ppb, and a small amount of metal impurities. The quality was similar to that of the synthesized DMSO and could be reused for processing electronic materials. At this time, the recovery rate of DMSO was 77%.
[0024]
【The invention's effect】
The mixture of DMSO and MEA is usually discarded after using electronic material processing. On the other hand, according to the present invention, DMSO can be easily and efficiently separated and recovered from a DMSO / MEA mixture that has been treated as waste, and reused effectively. For example, DMSO recovered by the present invention can be reused as it is as a stripping solution or cleaning agent for electronic materials, and can also be reused for various reaction solvents, dye solvents, fungicides, and the like. Therefore, it can contribute to resource saving and cost reduction.
[0025]
According to the present invention, the apparatus has a simple structure and the processing cost is low, which is economically advantageous.
[Brief description of the drawings]
FIG. 1 is a model diagram for explaining an outline of a recovery apparatus used in recovery of DMSO of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Evaporator 2 ... Capacitor 3 ... Ion exchange tower 4 ... Distillation tower 5-11 ... Piping

Claims (3)

A method of separating and recovering dimethyl sulfoxide from a mixture comprising dimethyl sulfoxide and monoethanolamine, after neutralization of the mixture by adding 0.8 to 1.5 equivalents of monoethanolamine sulfate, and distilled under reduced pressure, Furthermore, monoethanolamine remaining in a trace amount of dimethyl sulfoxide as a main component after distillation under reduced pressure is removed by ion exchange using a cation exchange resin alone, and then recovered by rectification. A method for recovering dimethyl sulfoxide, wherein the pH of the dimethyl sulfoxide obtained is 7.0 . 2. The method for recovering dimethyl sulfoxide according to claim 1, wherein monoethanolamine in the mixture is fixed in the form of a salt and distilled under reduced pressure. The method for recovering dimethyl sulfoxide according to claim 1 or 2 , wherein the recovered dimethyl sulfoxide is so pure that it can be recycled for processing electronic materials and has a low metal content.

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