Eka Nobel Ab

Maria Norell

Jorgen Engstrom

Anders Dahl

Bjorn H Svedin

Ursula Soderberg

A process for the production of chlorine dioxide by reacting in a reaction vessel an alkali metal chlorate, mineral acid and a reducing agent in such proportions that chlorine dioxide is produced in a reaction medium which is maintained at a temperature of from about 50.degree. C. to about 100.degree. C. and at an acidity within a range of from about 2 to about 5N. The reaction medium is subjected to subatmospheric pressure sufficient for evaporating water, a mixture of chlorine dioxide, oxygen and water vapor being withdrawn from an evaporation zone in the reaction vessel, and alkali metal sulfate being precipitated in a crystallization zone in the reaction vessel. As the reducing agent hydrogen peroxide is used.

Process for the production of chlorine dioxide

The present invention relates to a process for production of chlorine dioxide by reacting in a reaction vessel an alkali metal chlorate, a mineral acid and methanol as a reducing agent in proportions to generate chlorine dioxide in a reaction medium maintained at a temperature from about 50.degree. C. to about 100.degree. C. and an acidity within the interval from a b out 2 to 4.8 N and subjected to a subatmospheric pressure sufficient to effect evaporation if water. A mixture of chlorine dioxide and water vapor is withdrawn from an evaporation region in the reaction vessel and an alkali metal salt of the mineral acid is precipitated in a crystallization region in the reaction vessel. The reaction is performed in the presence of a catalyst, which comprises a metal or a combination of two or more metals being selected from the group consisting of antimony, molybdenum, technetium, ruthenium, rhodium, palladium, rhenium, osmium, iridium, platina, or a combination of one or more of these with manganese or vanadium.

Process for production of chlorine dioxide

A process for production of chlorine dioxide by reacting in a reaction vessel an alkali metal chlorate, a mineral acid and methanol as a reducing agent in proportions to generate chlorine dioxide in a reaction medium maintained at a temperature from about 50.degree. C. to about 100.degree. C. and at an acidity within the interval from about 2 to about 11N and subjected to an subatmospheric pressure. Thereby water is evaporated and a mixture of chorine dioxide, water vapor and gaseous by-products is withdrawn from an evaporation region in the reaction vessel. The alkali metal sulphate is precipitated in a crystallization region in the reaction vessel. The content of formic acid in the reaction vessel is increased by addition of formic acid to a content of formic acid exceeding about 0.3M. The gaseous by-products are condensed to obtain formic acid and the content of formic acid in the reaction vessel is increased by recirculation of the condensate.

The present invention relates to a process for production of chlorine dioxide by reacting in a reaction vessel an alkali metal chlorate, sulfuric acid and methanol as a reducing agent. A reaction medium is maintained at a temperature from about 50.degree. C. to about 100.degree. C. and is subjected to a subatmospheric pressure sufficient to effect evaporation of water whereby a mixture of chlorine dioxide and water vapor is withdrawn from an evaporation region in the reaction vessel and alkali metal sulfate is precipitated in a crystallization region in the reaction vessel. Raw methanol purified by separation and adsorption is used as reducing agent. The raw methanol is purified by dilution with water whereby an unpolar phase is separated and and the remaining methanol-water phase is contacted by an adsorbing agent. The adsorbing agents used can be zeolites, active carbon or polymer adsorbing agents.

The present invention relates to a process for production of chlorine dioxide by reacting in a reaction vessel an alkali metal chlorate, sulfuric acid and a reducing agent, preferably methanol, in proportions to generate chlorine dioxide in a reaction medium maintained at a temperature from about 50.degree. C. to about 100.degree. C. and an acidity within the interval from 4.8 to 11 N and subjected to a subatmospheric pressure sufficient to effect evaporation of water. A mixture of chlorine dioxide and water vapour is withdrawn from an evaporation region in the reaction vessel and alkali metal sulfate is precipitated in a crystallization region in the reaction vessel. The alkali metal sulfate, which is an alkali metal sesquisulfate, from the crystallization region is heated to the formation of gaseous sulfur trioxide and a neutral alkali metal sulfate. The gaseous sulfur trioxide is absorbed in water to the formation of sulfuric acid. The sulfuric acid formed can be recirculated to the reaction vessel for chlorine dioxide production.

The present invention relates to a process for production of chlorine dioxide from an alkali metal chlorate, a mineral acid and a volatile reducing agent. The process is carried out in a vessel operated under subatmospheric pressure, whereby water is evaporized and withdrawn together with chlorine dioxide and the alkali metal salt of the mineral acid is crystallized within the reaction vessel and withdrawn therefrom. According to the invention the utility of the volatile reducing agent is enhanced by the addition of the agent to the region of crystallization in the reaction vessel.

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Sundsvall, Sweden

Maria Norell