Kernforschungsanlage Julich Gesellschaft MIT Beschrankter Haftung

Kernforschungsanlage Julich

Bernd D Struck

Herbert Neumeister

Aristides Naoumidis

Dagmar Boltersdorf

Robert Junginger

Hartmut Luhleich

Jiri Divisek

Francisco J Dias

Heiko Barnert

Heinrich Schmitz

Arno Schirbach

Mieczyslaw Perec

Ursula Paffen Nee Siebert

Dieter Triefenbach

A cathode/membrane assembly for an electrolysis cell capable of producing hydrogen in a cathode compartment, utilizes as the cathode material on a proton-permeable solid-electrolite ion-exchange membrane, a layer of porous graphite in the form of carbonaceous fibers coated with tungsten carbide. The graphite felt can be impregnated with an aqueous solution of para-ammoniumtungstate or with an alcoholic solution of tungsten hexachloride and the tungsten compounds are then converted to the tungsten oxides. The tungsten oxide coated graphite felt is then subjected to carburization at a temperature of 620.degree. to 950.degree. C. in a carburizing atmosphere, preferably a flowing CO/CO.sub.2 mixture.

Cathode/membrane assembly and method of making same

A process is disclosed for the production of a tungsten carbide-activated electrode, particularly an electrode which is utilizable as a cathode, and which consists of an electrically-conductive substrate with an active surface layer of tungsten carbide. The tungsten carbide is adhesively bonded through chemical reaction to the surface of a substrate which is constituted of graphite or a graphite-like material. The graphite-like material is a graphite binder mixture, whose binder material components, other than the graphitic filler granules, are only carbonized, and may not be completely graphited.

Process for production of a tungsten carbide-activated electrode

An anode for electrolytic oxidation of sulfur dioxide is made by coating an lectrode of a graphite-like carbon material with a layer of cokable organic material such as sugar, phenolic resin, and asphalt pitch, heating the coated electrode body in an inert atmosphere to a temperature of between 400.degree. to 800.degree. C. and thereafter heating the coated electrode to a temperature in the range of 1400.degree. to 2000.degree. C., so that the material is first coked on the graphite to produce a porous flow-through electrode body which, thereafter, is heated to a higher temperature, followed by cooling.

Method of producing an electrode usable as a flow-through anode

The economy of production of hydrogen and sulfuric acid in a three chamber lectrolysis cell in which an electrolyte flows through the intermediate chamber (11) which is bounded by ion exchanger membranes (9,10) can be improved by the provision of a porus supporting framework or skeleton (12) of graphite or of ion exchanger material against which the separators with the electrodes (7, 8) on them, can be pressed. The overall internal resistance of the cell can thus be reduced and its mechanical behavior improved. Substantial through passage porosity is desired in the supporting structure, which may be of graphite, but porous aggregates of ion exchanger material with fixedly applied or welded on separators in the form of stacked layers or rolled mats, are preferred for the relative simplicity of their provision in practice.

Electrolysis cell with intermediate chamber for electrolyte flow

A reduction of the voltage across the electrolysis cell in which hydrogen is produced in the sulfuric acid hybrid closed cycle process by use of an electrolysis cell having an intermediate chamber between the anode and cathode chamber through which a separate electrolyte is caused to flow, is obtainable under operation with the electrolytes in both the cathode and the anode chambers having a concentration of sulfuric acid by weight of about 50% or more. It is found that the undesired formation of hydrogen sulfide and of sulfur remains at a tolerable small level if the catholyte is continuously renewed. A low specific resistance cation membrane is preferably used between the cathode and intermediate chambers, as well as between the anode and intermediate chambers.

Method for electrolytic production of hydrogen

The production of hydrogen by electrolysis in a cell, in which the anode electrolyte contains sulfur dioxide as well as sulfuric acid and an intermediate chamber separated from the anode and cathode chambers by cation-exchanger membranes is provided through which an electrolyte flows in order to prevent sulfur dioxide from reaching the cathode chamber is greatly improved by using as the anode side membrane a cation-exchanger in which a polyvinyl chloride skeleton is combined with a polymer of styrol and divinyl benzol to which sulfonic acid groups have been attached, such a membrane having a very low resistivity, thus reducing the necessary electrolysis voltage. Such a membrane also loses conductivity with increasing sulfuric acid concentration at a lower rate than membranes previously used in such an electrolysis process and permits a higher sulfuric acid concentration in the anode electrolyte. The improvement on the anode side makes possible the operation of the cathode at low sulfuric acid electrolyte concentration, below 20 or even 10% by weight. Through-flow electrodes of porous graphite encased except on the membrane side by impermeable graphite further improve the operation of the process, especially if they fill the electrolyte chamber right up to the membrane.

Electrolysis cell and method for electrolytic production of hydrogen

Particles of electrically conducting activated carbon of about 500 to 1,000 m.sup.2 /g specific surface added to an electrolyte provided by a solution of sulfur dioxide in water are found to provide a substantial reduction of the electrical energy requirement in the electrolysis of such an electrolyte for the production of hydrogen and sulfuric acid. A further reduction of energy consumption is obtained by additionally introducing iodine in the electrolyte in an amount not exceeding 1% by weight of the entire solution. Use of an anode in which the surface of a graphite base body is coated with a thin layer of activated carbon bonded to the graphite body by means of a binder, such as rubber, also reduces the electrical energy requirement for the electrolysis. To coat the surface of the electrode, carbon particles are first dispersed in a rubber solution and the suspension is then applied to the surface of the graphite body as a thin layer.

Process for the electrolysis of sulfur dioxide solutions

An electrolyte in an intermediate space between permeable partitions respectively separating the intermediate space from the anode space and the cathode space of an electrolytic cell is caused to be circulated through the intermediate space so as to remove materials migrating from one electrode space before they have an opportunity to migrate into the other electrode space. It is also of advantage for the electrolyte to contain material for reacting chemically with materials so migrating from an electrode space, in which case the slow velocity may be reduced or, for reduction of the electrical resistance, the spacing between the permeable walls may be reduced. This type of electrolytic cell is applied especially to the sulfuric acid hybrid process.

Process for conversion of materials in electrolytic solution

A method of recovering hydrogen and oxygen from water. Water and sulfur dide are supplied to, and hydrogen and sulfuric acid are removed from, a galvanic or electrolytic cell. Hydrogen ions are electrochemically liberated by anodic oxidation of the supplied sulfur dioxide accompanied by decomposition of the water and formation of sulfuric acid in the anolyte, and hydrogen gas is electrolytically generated at the cathode from the hydrogen ions. To evaporate water, electrolytic solution is removed from the anode chamber of the galvanic cell. The anode chamber is separated from the cathode chamber by means of a membrane. After the ensuing evaporation, the thus formed anhydride of the sulfuric acid is decomposed by being heated, and is accompanied by the formation of oxygen and sulfur dioxide gas. The sulfur dioxide is oxidized at a carbon and/or graphite anode in the presence of very small quantities, e.g. a minimum of 0.005% by weight, of hydriodic acid in the anolyte. The hydriodic acid which is found in that portion of the electrolyte which is removed from the anode chamber is evaporated together with the water. The evaporated water, together with the evaporated hydriodic acid, are again supplied to the anode chamber.

Growing community of inventors

Langerwehe, Germany

Bernd D Struck