Electrolysis: processes – compositions used therein – and methods – Electrolytic synthesis – Utilizing fused bath
Reexamination Certificate
1998-01-27
2001-05-22
Gorgos, Kathryn (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic synthesis
Utilizing fused bath
C205S409000, C205S370000, C205S351000
Reexamination Certificate
active
06235183
ABSTRACT:
The present invention relates to a novel process for preparing sodium and aluminum chloride electrochemically.
The invention furthermore relates to an electrolytic cell suitable for carrying out this process and to a process for cleaning this cell.
Sodium is an important inorganic basic product which is used, for example, for preparing sodium amide and sodium alkoxides. It is obtained industrially by the Downs process by electrolysis of molten sodium chloride. This process has a high energy consumption of over 10 kWh/kg of sodium (Büchner et al., Industrielle Anorganische Chemie [Industrial Inorganic Chemistry], 2nd Edition, Verlag Chemie, p. 228 ff). The process furthermore has the serious disadvantage that the electrolytic cells are destroyed by the solidification of the salt melt on turning them off.
Aluminum chloride is mainly employed as a catalyst, eg. in Friedel-Crafts reactions. Preparation is carried out to a great extent by direct chlorination of molten aluminum. (Büchner et al., Industrielle Anorganische Chemie, [Industrial Inorganic Chemistry], 2nd Edition, Verlag Chemie, p. 262). In this process, a substantial part of the energy which was used in the form of electric current for electrolytic preparation of chlorine and aluminum is liberated unused.
GB-A 2 056 757 describes a process for lowering the melting points of alkali metal tetrachloroaluminates by adding an alkali metal fluoride and the use of such mixtures as electrolyte.
DE-A 37 18 920 relates to the coupled electrochemical preparation of an alkali metal and an alkali metal halide compound such as sodium tetrachloroaluminate. The coupled product thus formed in addition to the alkali metal, however, is unattractive for production on the industrial scale. The formation of sodium tetrachloroaluminate from sodium chloride and aluminum chloride is automatically connected with the formation of aluminum chloride. According to the patent description, a concentration of aluminum chloride should be avoided in order to avoid damage to the separator between the anode and cathode compartments and a rise in the cell voltage.
It is an object of the present invention to provide a process which allows an energetically more favourable preparation of sodium than the Downs process. The coupled product obtained in the process should be a substance which can be employed on the industrial scale. Both process products should be obtained in such a high purity that further expensive purification steps are not necessary. A further aspect of the object consists in finding a process which allows the electrolysis process to be carried out repeatedly in the same electrolytic cell. Additionally, it was part of the object to find an electrolytic cell suitable for this process. Furthermore, a process for cleaning the electrolytic cell used for the reaction was to be found.
We have found that this object is achieved by a process for preparing sodium and aluminum chloride electrochemically, which comprises, in an electrolytic cell having aluminum as an anode and sodium as a cathode which are separated from one another by a sodium ion-conducting solid electrolyte, electrolyzing a fused electrolyte consisting essentially of sodium tetrachloroaluminate in the anode compartment, evaporating aluminum chloride formed in this process from the electrolytic cell and removing sodium from the cathode compartment.
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patent: 4203819 (1980-05-01), Cope
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Huber Gunther
Pforr Gerhard
Putter Hermann
Schlafer Dieter
Spiske Luise
BASF - Aktiengesellschaft
Gorgos Kathryn
Keil & Weinkauf
Maisano J.
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