Electrolysis: processes – compositions used therein – and methods – Electrolytic synthesis – Preparing inorganic compound
Patent
1995-11-16
1997-12-30
Bell, Bruce F.
Electrolysis: processes, compositions used therein, and methods
Electrolytic synthesis
Preparing inorganic compound
205466, C25B 130
Patent
active
057025851
DESCRIPTION:
BRIEF SUMMARY
This is a national stage application of PCT/EP94/01028, filed on Apr. 1, 1994.
BACKGROUND OF THE INVENTION
This invention relates to a process of preparing an aqueous alkaline peroxide solution having an alkali/H.sub.2 O.sub.2 molar ratio of 0.5 to 2.5 in an electrochemical cell, which comprises a porous oxygen diffusion cathode, a cation exchange membrane, and an anode and in which a sulfuric acid-containing electrolyte is caused to flow through the anode chamber, an akali hydroxide-containing electrolyte is caused to flow through the cathode chamber, and alkali peroxide is formed in the alkali hydroxide-containing electrolyte by a reduction of oxygen at the cathode.
Peroxide solutions are increasing in importance as oxidizing and bleaching chemicals because the reaction product derived from the peroxide used as an oxidizing agent does not pollute the environment. For instance, alkaline aqueous hydroperoxide solutions are used to bleach woodpulp and paper. Hydrogen peroxide and sodium hydroxide solutions are used as starting materials for making the bleaching solution and are mixed to form sodium peroxide or sodium hydroperoxide in an aqueous solution. Because hydrogen peroxide is a relatively unstable compound and strict safety requirements must be met for its transportation, storage, and handling, it is much simpler and more desirable to prepare alkali peroxide solutions by electrochemical methods directly at the location at which they are to be used.
U.S. Pat. No. 4,693,794 describes an electrochemical process for the preparation of hydrogen peroxide in which carbon dioxide is removed from air and oxygen from the air is reduced to form hydrogen peroxide at a cathode which is contacted by a flow of an alkaline electrolyte. The electrochemical cell is divided by a membrane into an anode chamber and a cathode chamber.
U.S. Pat. No. 4,758,317 discloses a process for the preparation of hydrogen peroxide which is characterized in that oxygen is reduced to hydrogen peroxide at a cathode in the presence of an aqueous alkaline electrolyte in an electrochemical cell, which comprises a porous oxygen diffusion cathode and an anode and is divided by a membrane into a cathode chamber and an anode chamber.
U.S. Pat. No. 4,872,957 discloses a process of reacting a liquid with a gas in an electrochemical cell, which comprises a porous gas diffusion cathode, a microporous diaphragm, and an anode and in which an electrolyte is circulated.
U.S. Pat. No. 4,317,704 discloses for the operation of an electrochemical cell a process in which a gas-liquid mixture comprising an oxygen-containing gas and a catholyte is caused to flow through a cathode and part of the oxygen is reduced at the cathode.
U.S. Pat. No. 4,431,494 discloses the preparation of alkaline peroxide solutions by an electrochemical process which is characterized in that the aqueous alkaline electrolyte solution contains a complexing agent or a chelating agent in order to inhibit at least in part the catalytic influence of impurities on the decomposition of peroxide.
EP0 066 663 A1 discloses an electrochemical cell, which serves to prepare an alkaline peroxide solution and in which a solution which contains oxygen or air is caused to flow through a porous cathode so that oxygen is reduced. In that cell, the cathode chamber is separated from the anode chamber by a membrane.
U.S. Pat. No. 3,884,778 discloses a process for the preparation of hydrogen peroxide, aqueous alkali hydroxide solution, and aqueous sulfuric acid. This process is carried out in an electrochemical cell, which comprises three chambers and in which a sulfuric acid-containing aqueous solution is caused to flow between the anode and a semipermable anion-active membrane, water is caused to flow between a cathode and a semipermeable cation-active membrane, and an alkali sulfate solution is caused to flow through the intermediate chamber thus defined. In that process the application of an external voltage has the result that a persulfuric acid solution is formed at the anode and hydrogen and an a
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Hillrichs Eilhard
Kienberger Manfred
Sander Ulrich
Bell Bruce F.
Leader William T.
Metallgesellschaft Aktiengesellschaft
Striker Michael J.
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