Anode for electrolysis and method of electrolytically synthesizing fluorine-containing substance using the anode for electrolysis

Abstract

The present invention provides an electrode for electrolysis, wherein the electrode comprises: a substrate comprising an electrically conductive material, wherein the surface of the substrate is made of glassy carbon; and an electrically conductive diamond film with which at least part of the substrate is coated.

Description

TECHNICAL FIELD[0001]The present invention relates to an anode material which, when used in applications such as electrolysis in an electrolytic bath containing hydrofluoric acid, does not produce the anode effect even upon application of a high-current-density voltage thereto and which is free from the serious sludge generation caused by electrode dissolution, can inhibit CF4 generation, and enables the electrolysis to continue stably without suffering electrode disintegration. The invention further relates to a method of electrolysis.BACKGROUND ART[0002]An electrolytic process in which a solution prepared by dissolving an inorganic or organic compound in anhydrous hydrofluoric acid (anhydrous HF) is used as an electrolytic bath to electrolytically synthesize an inorganic fluorine compound, organic fluorine compound, or fluorine gas is in practical industrial use.[0003]Since anhydrous HF has insufficient electrical conductivity, an alkali metal fluoride such as, e.g., potassium flu...

AI Technical Summary

Benefits of technology

[0031]The invention provides an electrode which comprises a substrate comprising an electrically conductive material, wherein the surface of the substrate is made of glassy carbon, and an electrically conductive diamond film with which at least part of the surface is coated, and which is for use in, e.g., the synthesis of an inorganic fluorine compound, organic fluorine compound, and fluorine gas through the electrolysis of an electrolytic bath containing HF. The invention further provides a method of electrolytically synthesizing fluorine or a fluorine-containing compound using the electrode.

[0032]The electrode and the synthesis method prevent the anode effect, electrode wear, and electrode disintegration from occurring even in an electrolytic bath having a high HF concentration, and render long-term continuous electrolysis possible. The productivity of inorganic fluorine compounds, organic fluorine compounds, and fluorine gas is improved.

Problems solved by technology

In all these electrolytic processes, materials usable as electrolyzers and electrode materials are limited because of the marked corrosiveness of HF.

In particular, the materials usable as anode materials are limited to nickel and carbon.

When nickel is used as an anode, wear of this anode is considerably accelerated.

However, carbon anodes often pose a problem that the phenomenon in which the electrode is passivated, i.e., the so-called anode effect, occurs to make it difficult to continue the electrolysis.

This oxidized graphite is chemically unstable and, hence, a substitution reaction with fluorine readily proceeds to generate fluorinated graphite.

Because of these measures, the rate of generating a target substance is limited and this inhibits the profitability of electrolytic synthesis from improvement.

On the other hand, HF intercalates into the carbon electrode to expand the electrode and this expansion often causes the electrode to crack or disintegrate.

However, no essential solution has been found because nickel itself is problematic as will be described later.

This technique therefore has limitations.

Nickel anodes are worn in an amount corresponding to 3-5% of the quantity of electricity applied, and the cost of replacing the worn nickel anodes is almost comparable to the power cost for the electrolysis.

In addition, nickel dissolves in the electrolytic bath to increase the viscosity of the electrolytic bath, makingitdifficulttocontrolthe temperature of the electrolytic bath.