US2820745A - Process for electrowinning titanium or its congeners - Google Patents

Description

United States Patent O Foord von Bichowsky, Wilmington, Del.

Application January 12, 1953 Serial No. 330,917

4 Claims. (Cl. 204-14) No Drawing.

This invention relates to a new and improved process for the obtaining of titanium and/or its congeners by electrolytic means.

Attempts to electrowin the metals of the fourth group of the periodic table of the elements and specifically to recover pure, titanium, zirconium or hafnium from aqueous solutions or from melts containing their com pounds have resulted either in the deposition of very thin films or in the formation of a metal so dispersed within the melt that its recovery therefrom was very difficult.

Work also has been done toward plating out the metals: of the fourth group from non-aqueous solutions of their halogen compounds. In those experiments the metals were used mainly in the form of their quadrivalent salts, for example, the readily available titanium or zirconium tetrachlorides, but because of the great chemical activity of such compounds the organic solvents employed, which were mostly of an alcohol or glycol type, probably reversibly reacted with those salts in accordance with the following typical equation:

and so, perhaps because of the linkage of titanium to oxygen in the resulting titanium ethylate, an oxygen free titanium could not be recovered from an alcoholic solution of that compound.

In order to overcome any such harmful chemical activity, of the tetrahalides of the metals of the fourth group of the periodic table of the elements, it occurred to me to study the use of certain double halogen or addition compounds of the above cited group of elements and as a result of that study and its extensions I made the discovery that the metals of the fourth group of the periodic table; when in solution, as their double halogen salts, in substantially non-aqueous solvents and while under oxi-- dizing conditions, could be recovered therefrom in a commercially pure form when the conditions were so a-d-- justed that the discharge potentials of the cations in the: solvent were appreciably different.

The present invention thus covers the electrowinning; of titanium and its congeners by the employment of a. non-aqueous electrolyte, liquid at usual temperatures, which contains halogen salts of the metals of the fourth group, for example, titanium tetrachloride, associated with halogen salts of other metals and under oxidizing conditions.

The double halogen compounds of the fourth group of metals, in which the metal apparently has the coordination number 6 since it actuates 4 main valences and 2v minor valences, are represented by the salts, for example, of hexachlorotitanic acid.

That acid and its potassium and ammonium salts, as: well as the sodium salt of the corresponding zirconium. compound, are described in the literature and their prepa-- ration, for example, by salting out with hydrochloric acid. or by reaction of the constituents, with and without pres-- sure, is well known. I have also prepared those titanium: compounds by reacting either hydrogen chloride or am,-

' valence state down to that of the metal.

Patented Jan. 21, 1958 ice monium chloride or potassium chloride, in an essentially non-aqueous solvent (i. e. one that contains no more H O than is present in the commercial product) with titanium tetrachloride, either in concentrated form or diluted with, for example, carbon tetrachloride, in the cold. By that same general procedure I have interacted other metallic salts, in approximately the stoichiometrical amounts, with titanium tetrachloride or zirconium tetrachloride. Of the other metallic salts with which I have experimented I will mention here only the chlorides of iron, copper, nickel, mercury, lithium, cadmium and lead but by following the above outlined technique the complexes of the metals of the fourth group of the periodic table may be formed either alone or intermixed with one another or with the salts of other elements in various I proportions and at various concentrations.

As usable solvents, for such metallo-complexes or addition compounds of hexavalent titanium or its congeners and in which an electrolysis may be carried out under oxidizing conditions, I mention here the ternary compounds: ethylene glycol, propylene glycol, glycerine, methanol, butanol, ethanol, propanol, ethyl ether, glycollic acid and/or other essentially anhydrous liquids fluid at room temperature which will conduct the electric current under the conditions of this invention.

In the process of the present invention the metal of the fourth group of the periodic system, when present as a complex of hexavalent titanium, or its congeners, with a chloride of another metal and while in a substantially anhydrous solvent, appears to go directly from its high In order to maintain that state of high valence an oxidizing agent, i. e. one that increases the positive valence of an element, is employed.

In theory any oxidizing agent; either gaseous, liquid or solid or combinations thereof, might be used to ac-- complish the above aim. In practice, however, it is found that not all oxidizing agents are equally advantageous because in certain cases some may be too active and others too sluggish. Of the oxidizing agents tested in connection with this invention and in most cases with good results there may be mentioned gaseous or atmospheric oxygen or chlorine which latter may be generated in situ or added to the electrolyte. Of the solid oxidants, ammonium persulfate, calcium hypochlorite, the normally insoluble higher oxides of lead or manganese or in special cases such compounds of copper or of iron as contain available oxygen may be cited. Barium peroxide also may be used but in that event the electrolyte should contain some free acid such as gaseous HCl or even HNO in order to keep the pH of the solution on the acid side. of the liquid oxidants one may use strong hydrogen peroxide or a concentrated solution of sodium hypochlorite or even nitric acid provided that they do not react in a deleterious manner with the electrolyte.

In carrying out an electrolysis of a halogen complex of a metal of the fourth group, while in a solution in one or more of the useful solvents in substantially nonaqueous state, a simple cell may be used. There also may be employed a cell which has partitions or diaphragms and in which the electrolyte either is stationary or is circulated within the separate compartments or else the application of circulation may be utilized in a cell of the :simple type.

The cathode in the chosen cell may be of mercury, lead, copper, cadmium, titanium or zirconium or hafnium or of any satisfactory material or alloy, and it may be fixed or rotatable. For most purposes I prefer to use titanium or zirconium as a cathode and while, for example, mercury has a high hydrogen overvoltage it also has a tendency to form insoluble compounds such as mercurous chloride which can contaminate the deposit 3' andsin,iadd-itiommercury.doesrnot appear to wet titanium nor.amalgamatestherewithn.. a

The anode may be of either a permanent or soluble type. Of the former I mention graphite and of the latter either; impure.- or; scraprtitaniumarmeta ga ld l. elsesa Loon-metallic: substance, sue as ;the H titaniurn;;nitride iass; mention U 1,783,684,;maynbe:employed H non-aqueous; solventszitamay 51365: des 1, t ca theelectmlys-is-at a temperaturesabpve-ithat oimomznr vidcd, that the. solvent is nor-appreciably h rmei e e Having nomnin generahnoutlinedpthe zm thqd p h inventionjI ill; illustrate it, by, a specific e amp e To 189 1 g. of; very ypures'IiClgl .(lgmoll'i n lwhi bGflILCQOlEdLIlfiEII'lY to freezing:,,(ca;:25? ;C:),1ther W added one mole of" driedi'anhydrous; (311C1 (134; g.)-a1rd the mixture; is, further LIOOlCdgsgY/hilfi; stirring untiiz brownz-mush of ,CuCl ;TiCl 1 solidifies 1 or; freezes when u onthere; is added thereto litersofl commereiallygann; hydrous methanol,,precooledtozbelow C.;. The bIOWEza O sediment; or mass of 4 the addition; complex gr dually di$- solves, as it thaws and whenall is in solutionzthe resulting; greenish liquid, is divided; intojtwo' portions; To the part to be used as the 1catholytegthere;is;adde l; abjout A of ammoniumPersulfate; and .the gentlyistirredsuspfin n is electrolyzedusing a compartmented ycell.; The, treated remainder: of the: greenish liquidis p1a 3d in the anodercompartmcnti; When using the. vabovevarrangeme 7 and with a graphite anodegandga sheet; of, titanium; 3 511 15 cathode p-the resulting titanium metal, is deposited thereon, at arcurrent: density ,of about:ISQamps/ftigas-a more; or less-spongy mass:

By means ofyarious changes in the currentdensity and through the use of,other-oxidizingmeans or.solvents;t;hetitanium-may, be obtained in differentparticle. :shapes and ,sizes.' In most cases it is desirable tor recoveri l e metalr-witha 4 minimum of occluded electrolyte. as; ,zthate facilitates its washing and working up.

In, like; manner zirconium or hafnium ;maysbe; electrowon'; from ;a solution of their double,- salts:-in,glyco1-;0r 40 #52-232, ,Electrodeposition,of Systems, December- 1952."

' 'in alcohol by using, for example, calcium hypochloi-iteas an Qxidizin r genta Now having described my invention what I claim is:

1. Process for the electrolytic production of titanium which comprises passing an electrolyzing current from an anode through an anhydrous anolyte which consists essentially of a solution of rCluCl TicL complex dissolved in an organic solvent selected from the, group consisting r of etliylenegglycol,- propylene glycol, .g ycerine, methanol; 7

ethanol, propanoheethylilethenrandsglycollic acid, to a cathode ou hesc h ly e.cnn i tinesssent a ly of a solution of said complex and sufiicierit ammonium pcrsulfate to tmaintaimthetitaniumrin the ;;tetrayalentr rstate in one of said solvents; a

2. The process oi claim h wherein the selected organic solvent is methanol. V

3. Process for the electrolytic production of titanium which comprises passing an electrolyzing current from an-anode i lir ush;-. .1;v a hyd o s. anolyte which-(consist Nlreois A-ras PATENTS.

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Claims (1)

1. PROCESS FOR THE ELECTROLYTIC PRODUCTION OF TITANIUM WHICH COMPRISES PASSING AN ELECTROLYZING CURRENT FROM AN ANODE THROUGH AN ANHYDROUS ANOLYTE WHICH CONSISTS ESSENTIALLY OF A SOLUTION OF CUCL2.TICL4 COMPLEX DISSOLVED IN AN ORGANIC SOLVENT SELECTED FROM THE GROUP CONSISTING OF ETHYLENE GLYCOL, PROPYLENE GLYCOL, GLYCERINE, METHANOL, ETHANOL, PROPANOL, ETHYL ETHER AND GLYCOLLIC ACID, TO A CATHODE THROUGH A CATHOLYTE CONSISTING ESSENTIALLY OF A SOLUTION OF SAID COMPLEX AND SUFFICIENT AMMONIUM PERSULFATE TO MAINTAIN THE TITANIUM IN THE TETRAVALENT STATE IN ONE OF SAID SOLVENTS.