US1863661A - Manufacture of fluorine - Google Patents

Description

june 21, W32. H. KREKELER I MANUFACTURE OF FLUORINE Filed Dec. 4, 1930 Patented June 21, 1932 HEINZ KBEKELEB, OI BERLIN, GERMANY,

PATENT OFFICE ASSIGNOR TO I. G. FARBENINDUSTRIE AKTIENGESELLSCHAFT, OF FRANKIORT-ON-THE-MAIN, GERMANY MANUFACTURE OF FLUORINE Application filed December 4, 1930, Serial No. 500,035, and in Germany December 5, 1929. i

The present invention relates to improvements in apparatus for the manufacture of fluorine by electrolysis of alkali metal fluorides and to improvements in the process.

Various publications are avallable relating to the production of fluorine. Fluorine has hitherto been manufactured principally in accordance with the processes of Moissan and Argo, Mathers, Huniiston and Anderson. In all these processes the electrodes were inserted from above into the electrolyzing vessel and fluorspar was employed as jointing material for the fixation of the electrodes.

According to the present invention alkali metal fluorides, especially diand polyfluorides are subjected to electrolysis in appropriate apparatus which are manufactured from materials resisting the attack of hydrofluoric acid and fluorine as, for instance, copper or magnesium. The electrolyzer is divided into two partitions, an anode and a cathode chamber in such a manner that the electrolyte and the current is allowed to pass 2 from one chamber to the other, but the gases evolved, fluoride and hydrogen, are prevented from passing from one chamber to the other. This is accomplished by the employment of diaphragms or U-shaped electrolyzing vessels or by any other means. Each chamber is provided with a gas outlet and at least one chamber is also provided with an aperture allowing the introduction of anhydrous hydrofluoric acid. One electrode consists of carbon, graphite or coke at which electrode fluorine is evolved and the other of carbon, graphite, coke or of silver or another metal which is not attackedby hydrofluoric acid, at which electrode hydrogen is evolved.

The current supply line for the electrodes passes through the walls of the electrolyzing vessel, but must be insulated therefrom and must be fastened in the walls.

In accordance with the present invention the electrolyte itself in the solid form is employed as the jointing and insulating material for the fixation of the electrodes. The advantages resulting in contradistinetion to the hitherto known processes signify an important technical advance. The electrodes are introduced from below upwardly into the electrolyte or from above or from the sides by means of cups or similar acting devices.

The reaction is performed with the liquid electrolyte. It is necessary therefor to heat the solid electrolyte to the melting point. According to the kind of electrolyte used the heat required varies within wide limits in accordance with the melting points of the fluorides employed. The meltin point is the lower the more mols of hydroduoric acid are loosely bound to the monofluoride. The termpolyfluorides used in the claims is intended to include alkali-metal-difiuorides as well as alkali metal polyfluorides containing more than two mols of hydrofluoric acid bound to one mol of alkali metal fluoride.

The invention is illustrated by the following examples, without being limited thereto:

Ewample: (compare Fig. I

The limbs of a U-shaped electrolyzing vessel (1) have two attachment tubes underneath. Through these are inserted electrodes (3) of known material and design. For the purpose of jointing a plate or disc (6') of a metal, such as copper or magnesium may be employed, through which the electrodes penetrate. Instead of metal plates, plates of an insulating material such asasbestos slate can likewise be used. After the electrodes have been placed into the desired position both limbs (5) of the electrolyzing vessel are filled with thoroughly dried alkali metal difluoride and freed from the last remaining 85 traces of moisture by passing through a thoroughly dried current of hot air. When this is accomplished the alkali metal difluoride is melted by an appropriate heating appliance and after all the alkali metal difluoride present in the attachment tubes above the metal or insulating material plates or discs has become liquid it is caused to solidify and the metal plates or discs are removed in an appropriate manner while the plates or discs made from insulating materials need not be removed. In order to prevent moisture penetrating through the attachment tubes these are now dipped into a bath of liquid parafiin mo wax or similar material.

The electrolysis can now proceed. During the electrolysis hydrofluoric acid freed from water is added through the tube 4 in.

the same measure as fluorine and hydrogen are evolved from the electrolyte. In this way the composition of the electrolyte is mainprevented by attaching a cooler (2) to the i any stoppage by the melt separate tubes through which the evolved hydrogen and fluorine escapes. The hydrogen fluoride can only evaporate through these tubes. At this point the tubes are advantageously expanded like a steamdome in order to revent there. Here also a sort of reflux condenser is attached which prevents any evaporation of hydrogen fluoride. At the same tlme a greater partial pressure of hydrogen fluoride above the melt is obtained so that by this means also the evaporation of hydrogen fluoride is restrained. Instead of alkali metal difiuoride alkali metal polyfluoride, produced by the subsequent passing in of hydrogen fluoride into the alkali metal difluoride, can likewise be used for electrolysis.

It may likewise be of advantage in the case of complicated apparatus: to introduce the electrodes from above or from the sides (see Fig. II). In this arrangement also solidified electrolyte (5) that is to say solid alkali metal dior polyfluoride, is employed as the jointing material. Instead of a U-shaped electrolyzing vessel as described above an other appropriate electrolyzing vessel (13 may be employed as, for example, an electrolyzlng vessel of cylindrical or angular shape, containing diaphragms (9) which allow the passage of the electrolyte from the cathode to theanode chamber, but prevents the passage of ases from one chamber to the other.

11 this drawin cups (7 attached to the tubes by which t e current suppl for the electrodes penetrate the walls are lled with the solid electrolyte (5). Into the solid electrolyte dip caps (8) which are fastened to the current supply for the electrodes, whereby a close insulation is attained.

I claim:

1. Anelectrolyzin ap aratus for the N- duction of fluorine y e ectrolysis of a ali metal polyfluorides comprising a vessel being divided in an anode and a cathode chamber, said chambers being connected by means allowing the passage of the electrolyte and the current from one chamber to the other, but not allowing the gases evolved to pass from one chamber to the other, an electrode in each of the chambers, each electrode being provided with a current supply said current supply passing through the walls of the apparatus but being insulated from direct contact with the walls by a layer of solid electrolyte and bein fastened by the solid electrolyte in the wa of the apparatus, each chamber being provided with a gas outlet and at least one chamber being provided with an aperture allowing the introduction of hydrofluoric acid and a heating appliance allowing each chamber, current supplying means connected with said electrodes, the current supplyin means and the electrodes being insulated mm the vessel by means of a solid layer of electrolyte interposed between said vessel and said electrodes and current supply means, means for removing evolved as from the chambers and means for intro ucing parent materialto the vessel.

3. An apparatus for the production of fluorine by electrolysis comprising a vessel divided into an anode and a cathode chamber by means permitting the passage of the electrolyte from one chamber to another but not permitting the evolved gases to pass from one chamber to another, an electrode within each chamber, current supplying means connected with said electrodes, the current supmeans and the electrodes bein insulated roin the vessel by means of a solld layer of electrolyte interposed between said vessel and said electrodes and current supply means, each chamber being provided with a gas outlet and at least one chamber being provided with an aperture allowing the introduction of li uid parent material.

11 testimony whereof, I afiix my signature.

. HEINZ KREKELER.

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