Asahi Kasei Kogyo Kabushiki Kaisha

Doryokuro Kakunenryo Kaihatsu Jigyodan

Mitsuo Yoshida

Shinsaku Ogawa

Yoshinori Masuda

Hiroyuki Shiroki

Akio Kashiwada

Akira Nakamura

Maomi Seko

Hajime Munekuni

Atsuo Ono

Hiroyoshi Matsuoka

Hiroyoshi Matsucka

Keiichi Ohmure

The electrolysis of an aqueous alkali metal chloride solution in electrolytic cells of the type having anode compartments and cathode compartments separated by a cation-exchange membrane is performed with improved efficiency by positioning and maintaining the cathodes in intimate contact with one entire surface of the cation-exchange membranes and the porous anodes in as close as possible proximity to the other surface of the membranes.

Method for electrolysis of aqueous alkali metal chloride solution

A hydrogen-evolution electrode having a coating comprising at least one metal oxide selected from the group consisting of nickel oxide and cobalt oxide and at least one metal selected from the group consisting of nickel and cobalt has been found to exhibit extremely low hydrogen overvoltage and to have not only high catalytic activity but also high durability.

Hydrogen-evolution electrode

In cation exchange membranes having a multi-layer structure consisting of two or three layers or more each having different equivalent weight and/or different kind of ion exchange group used for the electrolysis of alkali metal chloride according to an ion exchange membrane process, a homogeneous cation exchange membrane which comprises that at least one outer layer having a lower water content of both outer layers of said membrane has a roughened surface so that the amount of hydrogen gas bubbles generated from the cathode and attached to the membrane surface is the least whereby the electrolysis voltage is the lowest and the process for the production thereof.

Homogeneous cation exchange membrane having a multi-layer structure

Nitrates, such as alkali metal nitrates and ammonium nitrate, are electrolytically reduced to the corresponding nitrites by a process wherein an aqueous solution containing a nitrate is supplied into a cathode chamber of an electrolytic cell including cathode and anode chambers separated by a cation exchange membrane and an electric current is applied to the electrolytic cell, while maintaining the pH of the aqueous solution at a value of at least about 4. This process can be advantageously applied not only to the manufacture of nitrites but, also, to the treatment of waste nitrates. In the treatment of waste ammonium nitrate, the ammonium nitrite so formed is conveniently further treated by subjecting the electrolytically reduced catholyte to thermal decomposition outside the electrolytic cell, and removing the so formed nitrogen and water from the reaction system.

Process for preparing nitrogen by ammonium nitrate decomposition

The use of a perforated plate anode in combination with a cation exchange membrane has been found to be extremely effective for rendering the current distribution in the cation exchange membrane uniform in practice of the ion exchange membrane process for the electrolysis of an aqueous solution of an alkali metal chloride. The uniform current distribution in the cation exchange membrane is, in turn, effective for preventing elevation of the electrolytic voltage and prolonging the life of the cation exchange membrane. Further, when the coating of the perforated plate anode on its front surface and the inner wall surfaces of the openings has a thickness larger than that of the coating on the back surface, the perforated plate anode has high durability and exhibits low electrolytic voltage for a long time as compared with the perforated plate anode having, on each surface, a uniform-thick coating.

Method for the electrolysis of an aqueous solution of an alkali metal

A homogeneous cation exchange membrane having at least one roughened surface, which is assembled in an electrolytic cell with the roughened surface facing toward the cathode side of the cell, is employed in the electrolysis of an alkali chloride in an electrolytic cell divided by a cation exchange membrane into an anode compartment and a cathode compartment to produce an alkali hydroxide. The electrolysis voltage can be considerably reduced at a high current efficiency to provide a great economical advantage.

Process for electrolysis of alkali chloride

Process for preparing nitrites

A method of producing an electrode by applying onto a core material a solution of at least one metal salt and subjecting the resultant core material to a heat treatment in a heating zone, characterized in that said heat treatment comprises continuously elevating the temperature of the resultant core material to a temperature of about 400.degree. to 700.degree. C. over a period of about 5 minutes to 2 hours, while blowing air into the heating zone to obtain a coated electrode. The coated electrode produced according to the method of the present invention is excellent in adherence of the coating to the core material and has long life due to low losses of the coating during use.

Method of producing an electrode

A sodium chloride feed solution containing an iron cyanide complex is subjected to purification to reduce the content of iron cyanide complex to not more than 0.5 ppm before it is fed as anolyte into an ion-exchange membrane electrolytic cell. The iron cyanide complex is preferably converted by oxidative decomposition to iron ions for removal. By use of such a purified sodium chloride as starting material, electrolysis of sodium chloride using an ion-exchange membrane can be performed for a long term at a constant electrolysis voltage.

Electrolysis of sodium chloride in an ion-exchange membrane cell

A solid solution of a noble metal oxide, titanium oxide and zirconium oxide, containing 1 to 50 mol % of titanium oxide and zirconium oxide as the total content, is coated on an anti-corrosive substrate, e.g. titanium metal to give an electrode which is excellent in low oxygen content in chlorine gas, low electrode consumption and low chlorine overvoltage when it is used as anode for electrolysis of an aqueous sodium chloride solution.

Growing community of inventors

Nobeoka, Japan

Mitsuo Yoshida