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Composition of Fluorine Produced by Electrolysis

#3890


Study of Fluorine Composition from KF·2HF Electrolysis and Analysis Development for Concentration Determination of Fluorine Impurities by Multidimensional Gas Chromatography and Infrared Fourier Spectroscopy

Tech Area / Field

  • CHE-IND/Industrial Chemistry and Chemical Process Engineering/Chemistry

Status
3 Approved without Funding

Registration date
06.08.2008

Leading Institute
Siberian Chemical Combine, Russia, Tomsk reg., Seversk

Supporting institutes

  • Russian Scientific Center of Applied Chemistry, Russia, St Petersburg

Collaborators

  • University of Padova / Dipartamento di Chimi dell'Ingegneria, Italy, Padova\nAdvance Research Chemicals, Inc., USA, Catoosa\nCNRS / Institut de Chimie de la Matière Condensée de Bordeaux, France, Pessac

Project summary

At present production of elemental fluorine in numerous countries of the world community, namely England, France, Canada, the USA, Japan and Russia, is placed on a high industrial level and amounts to total capacity of 25,000 tons per year.

Establishment and development of an industrial technology for production of fluorine by electrolysis of hydrogen fluoride was associated basically with development of the fissile materials industry, in which fluorine is used for uranium hexafluoride production, during the second part of the 20th century. Using fluorine in this field did not require its exact composition. The majority of producers controlled in fluorine only the contents of hydrogen fluoride and some low-boiling impurities, basically nitrogen and oxygen. Moreover, fluorine composition data are needed to solve a number of tasks associated with reduction of negative effect of UF6 productions on the environment as well as with production of especially pure inorganic fluorides.

It is known, that during electrolysis of fluorine hydride using carbon anode the latter is fluorinated and tetrafluoromethane and, perhaps, other perfluoroalkanes are formed. Moreover, in fluorine there may present sulphur hexafluoride, which is formed during fluorination of sulphur-containing compounds going into an electrolysis unit as impurities in hydrogen fluoride. Sulphur hexafluoride, tetrafluoromethane and other perfluoroalkanes are reported to have high global warming potential. These compounds are chemically and thermally resistant substances, and during gas wastes neutralization in UF6 production they dissipate and accumulate in the atmosphere. According to preliminary assessment, volume concentration of tetrafluoromethane may amount to 1 vol.%. Thus, amounts of tetrafluoromethane dissipated in the atmosphere can be up to 500 tons per year.

At the same time it is known, that carbon anode fluorination rate can be minimized by selecting electrolysis modes and modifying the technology of electrodes production. To carry out these kinds of efforts to reduce fluorine hydrides emissions to the atmosphere it is required to study contents of impurities in fluorine as well as to develop methodologies for their quantity definition.

Apart from the mentioned above components, in fluorine there may be such high toxic compounds as carbonyldifluoride (fluorophosgene), carbon monoxide and others, to eliminate which special techniques are required.

Finally, knowledge of exact fluorine composition is needed to ensure quality of gaseous inorganic fluorides produced using fluorine and applied in semiconductors production industry.

Thus, development of an aggregate technology for fluorine analysis is a crucial scientific task of high ecological and commercial significance.

A group of experts, which was formed to realize the project, has wide experience in development and introduction of fluorine-using productions, including that of nitrogen trifluoride, tetrafluoromethane, octafluoropropane and others, as well as in development and introduction of certified analysis methodologies for inorganic fluorides, including nitrogen trifluoride and tungsten hexafluoride.


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