JPS62138323A - New method for purifying caustic potash - Google Patents

Abstract

PURPOSE:To easily collect a KOH aq. soln. purified in high purity from an under phase by bringing glycol into contact with a high-concn. KOH aq. soln. and separating a complex incorporated with KOH and water and adding water to this complex to phase-separate the mixture. CONSTITUTION:Glycol especially preferably 1,6-hexanediol or hexylene glycol is brought into contact with 40-60wt% especially 45-57wt% high-concn. KOH aq. soln. This contact is performed at 15-70 deg.C and when m.p. of glycol is higher than room temp., it is performed at m.p. and above. Thereby a complex incorporated with glycol series complex wherein KOH and water are incorporated therein is deposited as crystal. Then after separating this complex by an ordinary solid-liquid separation operation, this complex is decomposed by adding water of proper amount thereto and, if necessary, heating it at about 40-100 deg.C. A purified KOH aq. soln. of an under phase is separated from glycol of an upper phase and recovered. As a result, high-purity KOH can be collected by a process of less energy consumption unnecessitating energy used is distillation or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for purifying caustic potash. More specifically, the present invention relates to a method for purifying caustic potash that utilizes a phenomenon in which glycol incorporates caustic potash and water to form a glycol-based caustic potash uptake complex.

For example, when using a caustic potassium aqueous solution obtained by electrolysis of potassium chloride, only caustic potassium is selectively taken in, and potassium chloride, iron, potassium carbonate, etc. are not taken in, so it can be used to purify caustic potassium.

(Prior Art) Caustic potash, which is important in the chemical industry, is generally produced by electrolysis of potassium chloride. There are two methods for this: the mercury method and the diaphragm method. In the mercury method, trace amounts of mercury in the wastewater system pose an environmental problem, but caustic potash requires high purity in fields such as reaction catalysts, so the mercury method is the mainstream because it is easy to obtain high-purity products. However, even the caustic potash used in the mercury method is not satisfactory in terms of purity. Conventionally, attempts have been made to use milk of lime or lower alcohols to precipitate and remove impurities, but these methods cannot be said to be sufficiently effective. Industrial ultra-high purification technology for caustic potash has not yet been established.

(Problems to be Solved by the Invention) As mentioned above, in the caustic potash industry, if high purity caustic potash could be easily produced, it would be extremely significant.

(Means and effects for solving the problem) The present inventor has conducted extensive research into industrial purification methods for caustic potash, which has been difficult to achieve purity using conventional techniques, and has particularly focused on the behavior of high concentrations of caustic potash and glycol. As a result of research, it was found that by adding an appropriate amount of water to a new glycol-based caustic potassium uptake complex, which is a crystal in which glycol incorporates caustic potassium and water, and optionally heating, the glycol and caustic potassium water bath liquid phase separate, and the lower phase It has been found that purified caustic potash can be easily obtained. The present invention has been made based on these findings.

That is, according to the present invention, simply by bringing glycol into contact with a highly concentrated caustic potassium aqueous solution, a glycol-based caustic potassium uptake complex in which glycol incorporates caustic potassium and water is generated. At this time, impurities in the caustic potassium aqueous solution are not incorporated into the complex, so purification is performed. As a result of research into substances that react with a highly concentrated caustic potassium aqueous solution and take in caustic potash, the present inventor found that certain glycols take in caustic potash. For example, 1
．． Examples include 2-furopylene gelicol, neopentyl glycol, 1,6-hexanediol, and hexylene glycol. Among these, particularly preferred are u, 1,6-hexanediol and hexylene glycol.

The degree of caustic potassium aqueous solution used in the present invention is 40 to 60% by weight, particularly preferably 45 to 57% by weight. As for the contact method of the glycol and the high concentration caustic potassium water bath, normal stirring is sufficient. The reaction temperature is not critical, 15-70
C may be used, but when the melting point of the glycol is higher than room temperature, the reaction is carried out above the melting point. The reaction time may be about 1 minute to several hours, and the pressure may be atmospheric pressure.

When the caustic potassium uptake reaction is carried out as described above, the glycol-based caustic potassium uptake complex of the present invention incorporating caustic potassium and water is precipitated as crystals. At this time, impurities such as common salt and potassium carbonate in the caustic potassium aqueous solution are not incorporated into the complex.

In this way, glycol is brought into contact with a highly concentrated aqueous solution of caustic potassium, and a glycol-based caustic potassium uptake complex that incorporates caustic potassium and water is produced.

The composition of the glycol-based caustic potassium uptake complex of the present invention obtained as described above can be expressed by the following formula.

Gri: l-ru (KOH)x・(HtO)y where,
x, yFi molar ratio is shown, which varies depending on the reaction conditions,
Generally, 0.5≦X≦10.1≦Y≦15.

According to the present invention, glycol is brought into contact with a highly concentrated caustic potassium aqueous solution, the generated glycol-based caustic potassium uptake complex is separated from the aqueous solution system, water is added to the separated complex, and the glycol and the caustic potassium water bath liquid are phase-separated, A method for purifying caustic potash is provided, which is characterized in that a purified aqueous caustic potash solution is obtained from the lower phase. The purpose of separating the complex from the aqueous solution system can be sufficiently achieved by conventional solid-liquid separation operations such as filtration and centrifugation.

The complex separated and obtained from an aqueous solution is easily decomposed by adding an appropriate amount of water. If the amount of water is insufficient, the complex is decomposed by heating to about 40 to 1,000 degrees Celsius, if necessary. The decomposed complex separates into two phases. Glycol is transferred to the upper phase, and purified aqueous caustic potassium solution is transferred to the lower phase.

The glycol in the upper phase is reused, and the purified aqueous caustic potassium solution is obtained from the lower phase. In the method of decomposing the complex by adding water, glycols lower than 1,6-hexanediol and hexylene glycol do not cause phase separation even when water is added, forming a homogeneous bath liquid, and separating them from caustic potash. I can't.

In the case of such lower glycols, it is desirable to remove the glycol by heat treatment under reduced pressure.

(Effects of the Invention) As described above, by producing the novel caustic soda uptake complex of the present invention, caustic potash can be selectively taken in from a caustic potash aqueous solution, and at this time, caustic potash can be purified. Furthermore, this complex can be easily decomposed by adding water, and highly pure caustic potash can be obtained through an energy-saving process that does not require energy such as distillation.

(Example) Example 1 54% KOH aqueous solution 1000ml in a 3t glass flask
Add S' and heat to about 50C. To this, 1,6-hexanediol 2002, which had been heated and melted in advance, was added while stirring. Three hours after the addition was completed, the entire reaction solution was centrifuged to collect the precipitated crystals. The amount obtained was 462). Table 1 shows the compositions of this crystal and P solution.

Furthermore, 55 f of water was added to the crystals and heated to about 8 DC to dissolve the crystals and cause phase separation. A KOH aqueous solution with a concentration of 50% was obtained by obtaining the lower phase in a separatory funnel.
42″IC was obtained. KC in the obtained 50% KOH aqueous solution
The content of Co22p-1K was 0.59% by weight.

Note that KCl is 95% in the initial 54% KOH aqueous solution.
It contained 1.5% by weight of K2Co.

Example 2 54% KOH aqueous solution taoo in a 3t glass flask
y was added thereto, and hexylene glycol 2002 was added thereto with stirring. Five hours after the completion of the addition, the entire reaction solution was centrifuged to obtain precipitated crystals 4251. Table 1 shows the compositions of this crystal and P solution. Furthermore, water 53S' was added to this crystal, heated to about 80C,
The crystals were dissolved and phase separation occurred. By obtaining the lower phase in a separatory funnel, m change 47% aqueous KOH solution 2772
I got it. This 47% KOI (KCl in aqueous solution is 26p
The weight range of p, K, and Co was 0.36. 5 used
The 4th grade KOH aqueous solution is the same as in Example 1.

Example 5 Example 2 except for using hexylene glycol 100fi
Crystal 2811 was obtained in the same manner as above. Table 1 shows the composition of this crystal and p-liquid. Furthermore, this crystal has 2 parts of water.
9? was added and heated to about 80C to dissolve the crystals and cause phase separation. By obtaining the lower phase in a separatory funnel,
A KOH aqueous solution 2072 with a concentration of 47% was obtained. This 47%
KCl in the KOH water bath solution is 28 ppl, K, Co,
was 0.41% by weight.

Example 4 50% KOH aqueous solution 1000ml in a 3t glass flask
f, and hexylene glycol 2001 was added thereto with stirring. Three hours after the completion of the addition, the entire reaction solution was centrifuged to obtain 396 tons of precipitated crystals. Table 1 shows the compositions of this crystal and P solution. Furthermore, water 451 was added to this crystal, heated to about 80C,
The crystals were dissolved and phase separation Wa was caused. By obtaining the lower phase in a separatory funnel, a 47% concentration KOH aqueous solution 241
? I got it. KCl in this 47% KOH aqueous solution is llp
pm, K, and Co were 0.22% by weight. In addition, in the initial 50% KOH water bath solution, KCl is 25-5K,
It contained 0.89 times of Co.

Claims (2)

[Claims] (1) Glycol is brought into contact with a highly concentrated caustic potassium aqueous solution to form a glycol-based caustic potassium uptake complex that incorporates caustic potassium and water, and then the above complex is separated from the aqueous solution system and water is added to the separated complex. A method for purifying caustic potash, which comprises phase-separating glycol and a caustic potash aqueous solution, and obtaining a purified caustic potash aqueous solution from the lower phase. (2) The method for purifying caustic potash according to claim 1, wherein the glycol is 1,6-hexanediol or hexylene glycol.