Electrolysis: processes – compositions used therein – and methods – Electrolytic synthesis – Involving fuel cell
Patent
1996-01-02
1998-06-16
Phasge, Arun S.
Electrolysis: processes, compositions used therein, and methods
Electrolytic synthesis
Involving fuel cell
205465, 205466, 205468, C25B 130
Patent
active
057664439
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 continuation of PCT EP94/01506 filed May 10, 1994.
BACKGROUND OF THE INVENTION
This invention relates to a process of preparing aqueous alkaline solutions of peroxide and/or percarbonate in an electrochemical cell, which comprises a porous oxygen diffusion cathode and an anode.
Peroxide solutions are increasing in importance as oxidizing and lead 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 wood pulp and paper. Hydrogen peroxide and sodium hydroxide solution are used as starting materials for making the bleaching solution are mixed to form sodium peroxide or sodium hydroperoxide in an aqueous solution. Bleaching agents may also consist of sodium percarbonate-containing solutions, which are prepared by a mixing of sodium carbonate-containing and hydrogen peroxide-containing solutions. 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 peroxide solutions by electrochemical methods directly at the location at which they are to be used.
E. Yeager (Industrial Electrochemistry, Plenum Press, 1982, page 31) has disclosed an electrochemical cell which is operated like a fuel cell to prepare a peroxide solution without an application of an external voltage. That cell comprises a hydrogen diffusion anode, a KOH electrolyte and an oxygen diffusion cathode, which is supplied with air. A disadvantage of that electrochemical cell resides in that the current density is low so that peroxide is produced at such a low rate that peroxide apparently cannot economically be made by that process.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an economical process of preparing an aqueous alkaline solution of peroxide and/or percarbonate in an electrochemical cell.
That object is accomplished in accordance with the invention in that the cell is operated at a low external cell voltage, an electrolyte which contains alkali hydroxide and/or alkali carbonate is passed in the cell through the chamber disposed between the oxygen diffusion cathode and the anode, alkali peroxide and/or alkali percarbonate is formed by a reduction of oxygen at the cathode, and the H.sub.2 O.sub.2 /alkali molar ratio is less than 4.
According to a preferred feature of the invention the cell is operated at the low external cell voltage of 0.5 to 2.0 V.
According to a further preferred feature of the process in accordance with the invention the alkali hydroxide solution contains 30 to 180 g/l alkali hydroxide or alkali carbonate and the product solution contains 1 to 100 g/l H.sub.2 O.sub.2.
According to a further preferred feature of the invention NaOH or KOH is used as an alkali hydroxide and Na.sub.2 CO.sub.3 or K.sub.2 CO.sub.3 is used as an alkali carbonate.
According to a further preferred feature of the invention the solution of alkali hydroxide contains 50 to 100 g/l alkali hydroxide or alkali carbonate and the product solution contains 10 to 70 g/l H.sub.2 O.sub.2.
According to a further preferred feature of the process in accordance with the invention a chelating agent or at least a salt of a chelating agent is added to the electrolyte solution.
According to a further feature of the invention the chelating agent consists of ethylenediaminetetraacetic acid (EDTA) and the alkali salts are used as salts of the chelating agent.
According to a further preferred feature of the invention the porous oxygen diffusion cathode consists of a carbon woven or nonwoven fabric coated with a mixture of polytetrafluororethylene and carbon black.
According to a further feature of the invention the oxygen diffusion cathode is supplied with air or oxygen-enriched air or oxygen.
According to a further preferred feature of the process in accordance with the invention a hydrogen diffusion anode is used as an ano
REFERENCES:
patent: 4693794 (1987-09-01), Chiang
patent: 4921587 (1990-05-01), Dong et al.
patent: 5074975 (1991-12-01), Oloman et al.
Otsuka et al. "One Step Synthesis of Hydrogen Peroxide Through Fuel Cell Reaction" (1990) pp. 319-322.
Industrial Electrochemistry, "Electrodes for Electrolysis and Power Generation" by Yeager Plenum Press 1982, p. 31.
Hillrichs Eilhard
Sander Ulrich
Metallgesellschaft Aktiengesellschaft
Phasge Arun S,.
Striker Michael J.
LandOfFree
Process of preparing solutions of alkali peroxide and percarbona does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process of preparing solutions of alkali peroxide and percarbona, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process of preparing solutions of alkali peroxide and percarbona will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1721021