JPS6015711B2 - Electrolysis method of alkaline chloride solution - Google Patents

Description

Detailed Description of the Invention The present invention uses a stabilized Raney nickel catalyst electrode for the cathode of a so-called sealed membrane electrolytic cell in which a diaphragm or ion exchange membrane is provided between the anode and the cathode. This invention relates to a method of performing electrolysis.

It is well known that a significant proportion of the hydrogen overvoltage in sealed membrane electrolysers of alkaline chloride solutions is caused by the material constituting the cathode.

In order to increase productivity in electrolysis, it is desirable to conduct electrolysis at a high current density, but as the overvoltage increases, the power efficiency deteriorates, so it is desirable to have a high current density with a low overvoltage.

To this end, selection of the cathode material is being explored to reduce the overvoltage in the electrode reaction rate-limiting process.
For example, as a cathode in a diaphragm electrolyzer, a wire mesh or a perforated plate made of mild steel is generally widely used because hydrogen is easily generated and it is inexpensive. is still high (e.g., 0.3 to 0.55 V at a liquid temperature of 20 to 3 volts and a current density of 1 to IM no. d)
There is a drawback.

For this purpose, methods have been considered to use hydrogen overvoltage metals, nickel, platinum, other precious metals, and their alloys as the cathode rather than mild steel, but none of these have been put into practical use for economic reasons. is the reality. A method has also been proposed in which the hydrogen overvoltage is reduced by coating the surface of a mild steel electrode with a sacrificial metal and removing a portion of the sacrificial metal to make the electrode surface microporous.

Although the cathode produced by this method can have a considerably lower hydrogen overvoltage than a mild steel cathode, a sufficiently satisfactory hydrogen overvoltage cannot be obtained. The present invention is intended to effectively and economically reduce the hydrogen overvoltage to a level much smaller than that of the mild steel cathode in a sealed membrane electrolytic cell, thereby preventing loss of power efficiency and improving the overall performance of the electrolytic reaction. It was developed by

The method of the present invention has an electrode potential of -0.8 to 11.3 volts based on a saturated calomel electrode (at a current density of 1 to 100 A/d force in a 7 volt, NaOH and Wt% aqueous solution). The gist of this study is to electrolyze an alkali chloride solution using a Raney nickel catalyst electrode as the cathode of a sealed membrane type electrolytic cell.

The manufacturing method of the Raney nickel catalyst, which is the source of the present invention, is Mma
This method was proposed by Mr. YBay (1927), and in the present invention, a particularly stabilized Raney nickel catalyst electrode is used as the cathode of a sealed membrane electrolyzer.

Here, the stabilized Raney nickel catalyst electrode is manufactured as follows.

An alloy of aluminum and nickel is made by conventional methods,
After pulverizing into desired particles, it is developed with an alkaline aqueous solution to obtain a Raney nickel catalyst.

After washing, the material is vacuum dried and partially oxidized for a long period of time under specific conditions to further stabilize the material. It is obtained by mixing the thus obtained Raney nickel catalyst powder and polytetrafluoroethylene powder in a desired ratio and compression molding the mixture together with the above mixed powder using a metal wire mesh as a reinforcing material at a high temperature. This catalyst electrode is -0.8 to -1.3 V (70°C, 3 t% NaOH aqueous solution, current density 1 to 100 A/d〆) based on a saturated calomel electrode.
indicates the potential of The present invention will be easily understood from the following description of the embodiments.

Example (1) Method A of manufacturing the cathode used Method of manufacturing a Raney nickel catalyst electrode subjected to stabilization treatment.

Alloy powder of 50% nickel and 5% aluminum (50
95M or less) in a mother MKOH aqueous solution at 8000
% of aluminum is extracted, then washed with water, dried in vacuum, and stabilized by partially oxidizing the catalyst surface at room temperature for about 1 week in a high-purity nitrogen atmosphere containing about 1 to 1 OL% of oxygen. did.

80 parts by weight of the Raney nickel catalyst powder thus obtained and 2 parts by weight of polytetrafluoroethylene powder were molded into a 1.5-sided piece using a 30-mesh European steel wire mesh as the central base material.
Pressed at 00qo and pressure of 100k9/m. When this material is cathodically polarized in a 70qo, 3% t% caustic soda aqueous solution, -0.8 to -1.3 volts (current density 1 to 100 A) based on a saturated calomel electrode (SCE) as a reference electrode.
/d). B. Manufacturing method of porous nickel plated electrode. After degreasing and cleaning the mild steel cathode and drying it, Ni
Suspended in a solution containing C13・SLO1 mol/so, Z last 121 mol/〆 and day 380330 Tanok,
pH4.0 Current density 0. About 60 at ship/d〆, temperature 40℃
Electroplating was carried out for minutes.

The plated electrode was then immersed in a 0.9M NaOH aqueous solution for approximately 2 hours, with 2 hours of the dilution time being approximately 90q
o and the remaining time at about room temperature to remove the sacrificial zinc. (0) Implementation method Using three substantially identical diaphragm salt electrolyzers, one tank was filled with a mild steel cathode, the other one was filled with a stabilized Raney nickel catalyst cathode, and the remaining The electrolytic cells were configured so that only the cathodes were different by placing a microporous nickel-plated cathode in one tank, and by adopting a circulating catholyte system, each tank shared the same catholyte.

The catholyte contained 140 ml of NaOH and 160 ml of NaCI, and the temperature of the catholyte was 80 qo.

Each anolyte was a saturated saline solution with a pH of 3.5, and each anode was constructed of titanium coated with ruthenium oxide.

The diaphragm was made by vacuum adsorbing asbestos fiber onto each cathode surface. (m) Results The potential of the cathode surface was measured using a Lugin capillary attached to a saturated calomel reference electrode placed in a separate container at various current densities shown in the table below, and the results are shown in the table below. Ta.

Table of Results As shown in the above results, the cathode potential of the stabilized Funey nickel catalyst is lower than that of the mild steel cathode and the microporous nickel plated cathode.

In addition, the stabilized Raney-nickel catalyst electrode has 30% of the ions dissolved in the catholyte produced as a result of electrolysis.
It is also clear that ions such as CI- do not have any adverse effects. Furthermore, since mild steel can be used as the base material, it can be economical. According to the method of the present invention,
As shown by the results of the above examples, it is possible to effectively and economically reduce the hydrogen overvoltage (=electrode potential - equilibrium potential).

In the above example, an example of corneal membrane electrolysis is shown, but almost the same results as in this example can be obtained even when the above-mentioned cathodes are incorporated as the cathode of an ion-exchange membrane salt electrolyzer. was gotten. According to the method of the present invention, hydrogen overvoltage can be significantly reduced, power efficiency loss can be prevented, and the overall benefits of alkaline chloride solution electrolysis can be brought about.

Claims (1)

[Claims] 1 Saturated calomel electrode (HgIHg_2Cl_2・KC
l) -0.8 to -1.3 volts (70°C, NaO
In H30wt% aqueous solution, current density 1-100A/dm^
2) A method for electrolyzing an alkaline chloride solution, characterized in that alkaline chloride electrolysis is carried out using a Raney nickel catalyst electrode having the electrode potential as the cathode of a sealed membrane electrolytic layer.