US4426263A — Method and electrocatalyst for making chlorine di…

Claim 1

Independent Claim 180 words

A process for the electrochemical generation of chlorine dioxide comprising the steps of: (1) providing an electrochemical cell including an electrocatalytic cathode including a platinum group metal oxide mixture selected from a group consisting of ruthenium-rhodium, ruthenium-palladium, rhodium-palladium, iridium-rhodium, iridium-platinum and ruthenium-rhodium-palladium, each constituent of the mixture being present in a mole ratio of not less than 0.01; (2) providing a chlorate containing feedstock selected from a group consisting of aqueous solutions of alkali metal chlorate compounds and alkaline earth metal chlorate compounds; (3) providing an aqueous strong acid containing feedstock the acid being selected from a group consisting of H 2 SO 4 and phosphoric; (4) combining the feedstocks, the combined feedstock including the chlorate containing compound in a concentration range of from between 1/10 molar and saturation; (5) electrolyzing the combined feedstocks by passing an electric current through the combined feedstocks between the cathode and an anode within the electrochemical cell; (6) maintaining the electrochemical cell at a temperature greater than 20° C.; and (7) stripping ClO 2 from the electrochemical cell and recovering the ClO 2 .

Claim 2

Dependent Claim 180 words

A process for the electrochemical generation of chlorine dioxide comprising the steps of: (1) providing an electrochemical cell including an electrocatalytic cathode including a platinum group metal oxide mixture selected from a group consisting of ruthenium-rhodium, ruthenium-palladium, rhodium-palladium, iridium-rhodium, iridium-platinum and ruthenium-rhodium-palladium, each constituent of the mixture being present in a mole ratio of not less than 0.01; (2) providing a chlorate containing feedstock selected from a group consisting of aqueous solutions of alkali metal chlorate compounds and alkaline earth metal chlorate compounds; (3) providing an aqueous strong acid containing feedstock the acid being selected from a group consisting of H 2 SO 4 and phosphoric; (4) combining the feedstocks, the combined feedstock including the chlorate containing compound in a concentration range of from between 1/10 molar and saturation; (5) electrolyzing the combined feedstocks by passing an electric current through the combined feedstocks between the cathode and an anode within the electrochemical cell; (6) maintaining the electrochemical cell at a temperature greater than 20° C.; and (7) stripping ClO 2 from the electrochemical cell and recovering the ClO 2 .

Claim 3

Dependent Claim 25 words

The process of claim 1 wherein the H 2 SO 4 concentration of the combined aqueous feedstock is between about 1/3 molar and 18 molar.

Claim 4

Dependent Claim 43 words

The process of claim 1 wherein the combined feedstock comprises sodium chlorate in a concentration range of between about 1/2 molar and about 7 molar and H 2 SO 4 in a range of concentration of between about 1/3 molar and 18 molar.

Claim 5

Dependent Claim 32 words

The process of claim 1, the cathode also including titanium dioxide and wherein the platinum group metal oxides are present in a mole ratio to each other of not less than 0.01.

Claim 6

Dependent Claim 27 words

The process of claim 1 wherein the combined feedstocks are electrolyzed in the electrochemical cell at a temperature of between about 40° C. and about 90° C.

Claim 7

Dependent Claim 124 words

An electrochemical process for generating chlorine dioxide in a reaction zone equipped with both an anodic electrode and a cathodic electrode comprising: (i) filling said cell between said electrodes with an aqueous feedstock containing a strong acid and a chlorate of alkali metal or alkaline earth metal; (ii) providing in contact with said cathodic electrode a catalyst comprising a mixture of platinum group metal oxides selected from the group consisting of ruthenium-rhodium, ruthenium-palladium, rhodium-palladium, iridium-rhodium, iridium-platinum and ruthenium-rhodium-palladium, each constituent of the mixture being present in a mole ratio of not less than 0.01; (iii) passing a current between the two electrodes thereby forming chlorine dioxide at said cathodic electrode and surrounding catalyst; and (iv) stripping and recovering chlorine dioxide from said reaction zone.

Claim 8

Dependent Claim 124 words

An electrochemical process for generating chlorine dioxide in a reaction zone equipped with both an anodic electrode and a cathodic electrode comprising: (i) filling said cell between said electrodes with an aqueous feedstock containing a strong acid and a chlorate of alkali metal or alkaline earth metal; (ii) providing in contact with said cathodic electrode a catalyst comprising a mixture of platinum group metal oxides selected from the group consisting of ruthenium-rhodium, ruthenium-palladium, rhodium-palladium, iridium-rhodium, iridium-platinum and ruthenium-rhodium-palladium, each constituent of the mixture being present in a mole ratio of not less than 0.01; (iii) passing a current between the two electrodes thereby forming chlorine dioxide at said cathodic electrode and surrounding catalyst; and (iv) stripping and recovering chlorine dioxide from said reaction zone.

Claim 9

Dependent Claim 13 words

The process of claim 6 wherein the acid is sulfuric or phosphoric acid.

Claim 10

Dependent Claim 44 words

The process of claim 6 wherein the chlorate is NaClO 3 and the feedstock contains NaClO 3 in a range of concentration of between 1/2 molar and 7 molar, and H 2 SO 4 in a concentration range between 1/3 molar and 18 molar.

Claim 11

Dependent Claim 19 words

The process of claim 6 wherein the combined feedstocks is at a temperature in excess of about 40° C.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1987-01-16	1987-07-18	1988-01-17	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1991-01-16	1991-07-18	1992-01-17	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1995-01-16	1995-07-18	1996-01-17	$7700.00	Window Closed / Lapsed

Method and electrocatalyst for making chlorine dioxide

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