Tenneco Canada Inc.

Sterling Canada, Inc.

Rio Linda Chemical Company Inc.

Superior Plus Inc.

Edward J Bechberger

Maurice C Fredette

Marek Lipsztajn

Herbert C Scribner

Zbigniew Twardowski

John Y Mason

Gerald Cowley

Richard Swindells

Colin R McGregor

Chunmin Pu

Mario Luis Costa

Dick L Hilliard

Dorman N Matchim

A greater yield of chlorine dioxide from a chlorine dioxide generating process is obtained by providing acidic or acidity-generating components in the product chlorine dioxide solution to provide a chlorine dioxide solution having a pH below about 5.5.

Method of improving yield of chlorine dioxide generation processes

Sodium sesquisulfate produced in crystalline form in a high acidity highly efficient chlorine dioxide generating process is converted by metathesis to crystalline anhydrous neutral sodium sulfate and the acid recovered as a result is recycled to the chlorine dioxide generating step. The metathesis is effected by contacting the crystalline sodium sesquisulfate with aqueous sodium chlorate solution, aqueous sodium chloride solution, aqueous methanol or water alone. The metathesis is effected in such manner as to minimize the additional evaporative load imposed on the chlorine dioxide generating process by the metathesis medium.

Metathesis of acidic by-product of chlorine dioxide generating process

Chlorine dioxide, useful as a pulp mill chemical, is produced without producing sodium sulfate effluent for disposal, by effecting reduction of chloric acid in an aqueous reaction medium in a reaction zone at a total acid normality of up to about 7 normal in the substantial absence of sulfate ion and in the promence of a dead load of sodium chlorate added to and subsequently removed from the reaction medium. Chloric acid for the process is produced electrolytically from an aqueous solution of the deadload sodium chlorate and make-up quantities of sodium chlorate. The chloric acid reduction to produce chlorine dioxide may be effected using methanol or electrolytically.

Chlorine dioxide generation from chloric acid

Sodium sesquisulfate produced in crystalline form in a high acidity methanol-based highly efficient chlorine dioxide generating process is converted by metathesis to crystalline anhydrous neutral sodium sulfate and the acid recovered as a result is recycled to the chlorine dioxide generating step. The metathesis is effected by contacting the crystalline sodium sesquisulfate with aqueous sodium chlorate solution, aqueous sodium chloride solution, aqueous methanol or water alone. The metathesis is effected in such manner as to minimize the additional evaporative load imposed on the chlorine dioxide generating process by the metathesis medium.

Metathesis of acidic by-product of chlorine dioxide generating apparatus

A process for the rapid generation of chlorine dioxide under reduced pressure. A reaction column having a venturi therein and a reaction chamber in fluid communication with the nozzle of the venturi is provided. An aqueous chlorate solution and a gaseous stream of acid are introduced into the reaction chamber to react and form chlorine dioxide. A driving medium is introduced into the venturi, and the chlorine dioxide from the reaction chamber is mixed with the driving medium at the outlet of the venturi. The chlorine dioxide/driving medium mixture is passed through a reaction column. In an alternate embodiment, a chlorite solution is introduced into the reaction chamber together with the chlorate solution and the gaseous stream of acid. In a further embodiment, a chlorite solution is introduced into the reaction column after mixing of the driving medium with the chlorine dioxide.

Process for the generation of chlorine dioxide

The formation of sodium sulfate by-product in sulfuric acid-based chlorine dioxide generating processes is decreased and preferably eliminated entirely, by effecting electrochemical treatment of sodium ion-containing feed materials for the generator to remove sodium ions and to add hydrogen ions. Sodium hydroxide may be produced as a by-product. The process is generally applicable to the electrochemical treatment of alkali metal chlorates, alkali metal sulfates and mixtures thereof to produce acidified solutions useful in providing chlorate ion-containing feeds to such chlorine dioxide generating processes or for other purposes.

Electrochemical processing of aqueous solutions

Chlorine dioxide is formed by reduction of sodium chlorate in a sulphuric acid-containing reaction medium. Sulphuric acid is introduced to the reaction medium in air atomized form to promote rapid and efficient mixing of the sulphuric acid, thereby avoiding chlorine dioxide decomposition at hot spots resulting from inefficient mixing of acid with the reaction medium.

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Etobicoke, Canada

Edward J Bechberger