US2921890A - Electrolytic method for the production of pure titanium - Google Patents

Description

B. B. RANEY 2,921,890 ELECTROLYTIC METHOD FOR THE PRODUCTION OF PURE TITANIUM Jan. 19, 1960 Filed March 27, 1950 IN VENTOR B?! b? fimqy ATTORNEY ELECTROLYTIC METHOD FOR THE PRODUC- TION OF PURE TITANIUM 'Ben B. Raney, Linton, Ind., assignor to Chicago Development Corporation, Riverdale, Md., a corporation of Delaware Application March 27, 1950, Serial No. 152,175

6 Claims. (Cl. 204-64) This invention relates to a process for the production of titanium from various titanium compounds and ores.

More particularly my invention is concerned with the production of titanium, wherein atomic or nascent sodium is utilized as a reducing agent to react with titanium compounds and ores of various types.

Many previous methods of producing this comparatively rare metal have usually involved relatively expensive procedures, and the known commercial processes in the past have necessitated the use of complex chemical apparatus, or the use of reagents, such as metallic sodium, which are inherently dangerous to the person and difficult to handle. Some previous processes for the production of the element titanium involve the principle of using a reducing agent to liberate the free metal from the ore, but in this invention such agent is continuously produced as a free element in its nascent state, such as sodium, obtained through the electrolysis of a salt such as sodium chloride. Previous known processes have also required that the. reduction phenomena take place in the presence of an inert gas such as argon or helium, further complicating the steps of production. My invention obviatessuch a requirement since the reduction takes place in the absence of any gaseous medium whatsoever, other than the gaseous medium formed from the reactants themselves.

It is, therefore, an object of this invention to provide a simple method for the reduction of a titanium compound or ore to procure the free metal titanium in a pure state. Another object is to obtain titanium by a continuous method. A further object is to devise a process wherein the use of an inert gas as a protective medium is eliminated. Other objects and advantages will be apparent as this invention is described in more detail.

Briefly summarizing the invention, it comprises initially fusing an alkalinous metal salt, such as the salts of sodium or calcium, in a suitable crucible. As used in this description of my invention, the term alkalinous metal defines an alkali metal or an alkaline earth metal. An inverted bell is then positioned in the fused bath and the bell is cleared of entrapped air by the admission of either oxygen or chlorine thereto. The bath is then electrolyzed through the use of suitable electrodes, one of which, the cathode, is located in the bell and the other in the bath but exteriorly of the bell. After electrolysis is commenced, the titanium compound from which the pure metal is to be obtained, such as TiCl is admitted to the bell, the latter being cleared of gaseous constituents by the interaction of either oxygen or chlorine with free nascent sodium. Reaction of the alkali metal, as'sodium, with the said titanium chloride results in a portion of the sodium being bonded to the chlorine atoms of the TiCL, within the bell, a portion of the free chlorine of the bath also proceeding to the other electrode, the anode. Free titanium, being heavier than the bath, drops to the bottom of the crucible where it can be removed in any suitable manner.

Almost any type of ore containing titanium, or any Patented Jan. 19, 1960 other compound containing that metal, may be treated by the process of this invention, the metal in each case being removed with facility. In particular, my process is applicable to the recovery of pure titanium from the several halogen compounds of that metal, such as: titanium dichloride, trichloride or tetrachloride; titanium trifluoride or tetra-fluoride; and titanium di-iodide or tetra-iodide.

The accompanying drawing illustrates more particularly one embodiment of this invention, which will now be referred to in more detail.

The crucible is represented at 1. It is surrounded by a heating element 2 of any suitable type, such as an electrical resistance unit, which is adapted to heat the salt to the fusing point prior to electrolysis. The crucible is provided at its bottom extremity with an opening 3 which may take the form of an elongated tube having a passageway permitting emission of the melted constituents of the bath. This end extension 3 is surrounded by a heating coil 4 and one or more cooling units 5. These permitopening or closing of the bottom of the crucible dependent upon whether the passageway is heated to permit the contents to become sufiiciently vis cons to permit them to flow out, or cooled to the point of solidification, thereby blocking the passageway.

Disposed above the crucible is a retort 6 which contains the ore 7, from which TiCL, is obtained by interaction with chlorine discharged from the receptacle. The ore referred to may be one or more ofany of the oxide ores of titanium such as ilmenite, pseudobrookite or titanite. Titanium dioxide, which naturally occurs as rutile, does not contain any iron or calcium constituents and is particularly useful in this process. The first two ores of those named contain an iron constituentwhich may be removed in this process through condensation, or may contain calcium, which may be similarly removed.

The retort is in communication with the fused bath of the crucible through a communicating tube or pipe 10-. I have shown a screen 16 mounted over the opening of said pipe 10, where it enters the retort, for retention of the ore therein. The pipe 10 is sufiiciently large at one end to surround one of the electrodes used for carrying on the electrolysis, in this instance, the anode 11. The other electrode 12, positioned in any suitable manner at the opposite side of the bath, extends through an inverted bell 15. When the mouth thereof is placed in the fused bath, the bell forms a completely air-tight chamber, all interconnections therewith being suitably sealed. This bell is preferably formed of some wellknown refractory material which cannot be attacked by either the relatively high temperatures employed or chemical reagents used in the process. I have. found that sillimanite or mullite are refractories highly desirable for this purpose. Generally the cathode, which, as stated,

extends through the bell, should be made of nickel, this metal being the least likely to be attacked by the corrosive action of reagents used in the process. Graphite is a preferable material from which to fabricate the anode.

The retort 6 communicates through a suitable line 20 with a condensing unit 21, which is provided With a drain 22 for removal of condensed materials removed from the ore such as the FeCl indicated at 23 in the drawing. The condenser 21 is, in turn, interconnected through pipe 25 with an additional condenser 30, also provided with an outlet 32, to condense to liquid form the titanium chloride, indicated at 35, obtained in the reaction chamber of the retort. The temperatures of each of the chambers 21 or 30 may be controlled by media Well-known in the art.

As briefly stated in the foregoing, the process commences with the fusion of the salt of an alkali metal or alkaline earth metal. Sodium chloride will here bereapproximately 800 C. Should an eutectic mixture of potassium chloride and sodium chloride beutilized, the temperature of fusion will bereduced toapproximately 700 C. The temperature of fusion of an alkaline earth metalhalide is considerably higher. For instance, calcium fluoride does not fuse until the temperature is raised to approximately 1370 C. In any event, such temperature is employed as will fuse the salt utilized. Oxygen or chlorine is then blown into the bell to replace all the entrapped air with either of thosetwo elements, This, of course, may be accomplished by hand, through the provision, of an additional inlet 18 to the bell or through the line 19, which is provided for the admission of titanium chloride in its liquid state. Electrolysis is then started by the application of a sufficient current to cause the disassociation of the sodium and chlorine to occur within a reasonably practicable period. At an amperage of 12 and at 6 volts, electrolysis will proceed'at a reasonable rate, at least when the process is carried out on a minor scale. As electrolysis proceeds, sodium, in its nascent state, is liberated, the sodium ion migrating to the cathode, as will be readily understood. The cathode being located in the bell, thesodium immediately reacts with the oxygen or chlorine admitted to the bell to form either sodium oxide or sodium chloride. By this chemical union, the gaseous medium within the bell is eliminated. A vacuum consequently results, drawing the reactants of. the bath up into the bell. With electrolysis proceeding further, and with further liberation of nascent sodium within the bell15, titanium chloride is introducedinto the bell through line 19. The titanium chloride compound may be introduced in gaseous form, but if a continuous operation is contemplated, titanium chloride will be condensed in the last condensing chamber 30, where it will be under a temperature of about 100 C.,

a temperature atwhich it remains a liquid.

With the introduction of, for example, titanium chloride, the latter reacts withfree sodium to form sodium chloride'and the free metal titanium. The following equation illustrates the simplicity of the reaction involved:

As the titanium is heavier than the other reactants within the crucible, it will drop to the bottom of. the container in 'small solid particles. The pure metal may be withdrawn, as stated, by the application of heat to the exterior of tube 3 to keep the fused salt in molten form. As .theprocess continues, drain 3 may be closed by the application of a cooling medium thereto which obviously will transform the salt bath to a solid form preventing further passage out of the crucible.

In purifying the material withdrawn from the crucible, which is composed of sodium chloride and titanium, it is lixiviated with pure water to obtain the titanium in a powder form, the salt, .of course, dissolving during this procedure. If needed, the titanium powder may be further purified by Washing it with diluted hydrochloric acid, followed by an additional distilled water wash.

Referring back tothe remaining steps of the process, it will be appreciated that during fusion and electrolysis of the bath, free chlorine molecules will appear at the anode or positive electrode. The latter, being located within the enclosure pipe 10, permits bubbling off of the chlorine gas through pipe 10 to the retort 6 containing the crude titanium oxide ore. A reducing gas is added to the free chlorine thru a Side connection 17 to pipe 10.

if the ore utilized is, for example, titanium oxide rutile, this free chlorine and reducing gas will react with the same to form a volatile or gaseous titanium chloride. The gases emitted from the retort 6 are passed to a first condensing step represented by chamber 21. If the ore used in the process is of a type containing an iron con- 4. stituent such as ilmenite, (FeTiO the chlorine will unite with the iron of that compound producing ferric chloride. The receptacle 21 is cooled to approximately 250 C. for receiving such ferric chloride and the latter will be condensed to liquid form at that temperature, and retained in the lower portion of the container. Such liquid constituent is withdrawn through the drain 22. At this temperature, titanium chloride is still in gaseous form and a further condensation is necessary. Accord- V ingly, it is passed from the receptacle21 to an additional condensing chamber 30 through line 25. The latter chamber is cooled to approximately 100 C.,and.at this temperature the. titanium chloride 'is condensed to its liquid form.

As indicated hereinbefore, the titanium chloride obtained in the last step .of the process just described, may

be returned to the line 19 for further reduction to pure titanium in the manner already described; This return of the initial titanium compound to the initial step of the process permits the operation to be continuous, although, of course, it may be necessary to add additional titanium ore or rutile to the retort if the initial charge thereof diminishes by its reduction with chlorine. Additional salt may be added to the fused bath as required.

I characterizethe foregoing as a continuous process. The free; metal obtained thereby is of relatively high purity, and the percentage of yield considerably over that of known previous methods. I i

The following examples of my invention are illustrative of results obtained by the practice of this method:

Example 1 was then filled with oxygen and electrolysis commenced.

The latter step was carried on at 12 amperes and 6 volts. After: approximately two minutes titanium tetrachloride was admittedjunder the bell in the manner described. The electrolysis was carried on over a period of nine hours, approximately 120 grams of titanium chloride being used during this time interval. In this example the rate of addition of titanium tetrachloride was about 1.0 gram per ampere hour of current. After completion of the electrolysis and removal of the fused bath containing the purified titanium, the metal was washed free of salt in the manner related Total yield was 18 grams of titanium metal in powder form.

Example 2 described, 21 grams of; pure titanium.metal in powder form were recovered.

Since this process involves the .use of simple and harmless salts, from which the alkali metal is recovered in'a rapid and efficient manner, the yields of recovery 'are 7 considered to be substantially high. At potentials considerably in excess of those referred to, it is apparent that the overall time element may be substantially reduced. In thecontinuous method, loss of. starting ma: terials is likewise reduced to a minimum. 7

Obviously this invention is not limited to the use of the specific titanium compounds mentioned as starting materials, but would include any basic ore containing titanium and bound to inorganic reagents which would undergo the same or similar type. of reduction reaction.

As many variations are possible within the scope of this invention, I do not intend the same to be limited .in any manner except as defined by the appended claims,

I claim:

1. Process for reducing a chloride of titanium to metallic titanium, comprising the steps of electrolytically producing nascent alkalinous metal in a fused electrolyte consisting essentially of at least one alkalinous metal chloride in an electrolytic cell by the passage of unidirectional direct current therethrough, adding at least one chloride of titanium to the alkalinous metal-containing fused electrolyte in a restricted area about the cathode of the cell, at a rate equivalent to about 1 gram of chlorine, as the chloride, per ampere hour of said current, and recovering particulate titanium from the electrolyte.

2. Process for reducing titanium tetrachloride substantially completely to metallic titanium, comprising the steps of electrolytically producing nascent alkalinous metal in a fused electrolyte consisting essentially of at least one alkalinous metal chloride in an electrolytic cell by the passage of unidirectional direct current therethrough, adding titanium tetrachloride to the alkalinous metal-containing fused electrolyte in a restricted area about the cathode of the cell, at a rate of about 1.4 grams of titanium tetrachloride per ampere hour of said current, and recovering particulate titanium from the electrolyte.

3. Process for reducing a chloride of titanium to metallic titanium, comprising the steps of electrolytically producing nascent alkalinous metal in a fused electrolyte consisting essentially of at least one alkalinous metal chloride in an electrolytic cell by the passage of unidirectional direct current therethrough, adding a chloride of titanium of the group consisting of titanium trichloride and titanium dichloride to the alkalinous metal-containing fused electrolyte in a restricted area about the cathode of the cell, and recovering particulate titanium from the electrolyte.

4. The process defined in claim 3, in which the chlo- 6 ride of titanium is added to the electrolyte at a rate equivalent to about 1 gram of chlorine, as the chloride, per ampere hour of said current.

5. A process for the production of titanium metal comprising (a) fusing an electrolyte mixture containing at least two salts of the group consisting of sodium, potassium and calcium chlorides, and then simultaneously (b) adding titanium tetrachloride to the electrolyte in a confined space from which the atmosphere is excluded and in which a cathode is included, and (c) electrolyzing the resultant mixture to liberate titanium in the electrolyte, and later (:1) recovering the titanium thus liberated.

6. A process for the production of titanium metal comprising (a) fusing at least one alkalinous metal chloride to provide a fused electrolyte, and then simultaneously (b) adding a titanium chloride to the electrolyte in a confined space from which the atmosphere is excluded and in which a cathode is included, and (c) electrolyzing the resulting mixture to liberate titanium in the electrolyte, and later (d) recovering the titanium thus liberated.

References Cited in the file of this patent UNITED STATES PATENTS 559,729 Lorenz May 5, 1896 1,839,756 Grebe et a1. Jan. 5, 1932 1,842,254 Driggs Jan. 19, 1932 2,205,854 Kroll June 25, 1940 2,302,604 Dolbear Nov. 17, 1942 2,393,330 'McNitt Jan. 22, 1946 2,586,134 Winter Feb. 19, 1952 FOREIGN PATENTS 263,301 Germany Aug. 5, 1913 13,759 Great Britain of 1904

Claims (1)

1. PROCESS FOR REDUCING A CHLORIDE OF TITANIUM TO METALLIC TITANIUM, COMPRISING THE STEPS OF ELECTROLYTICALLY PRODUCING NASCENT ALKALINOUS METAL IN A FUSED ELECTROLYTE CONSISTING ESSENTIALLY OF AT LEAST ONE ALKALINOUS METAL CHLORIDE IN AN ELECTROLYTIC CELL BY THE PASSAGE OF UNIDIRECTIONAL DIRECT CURRENT THERETHROUGH, ADDING AT LEAST ONE CHLORIDE OF TITANIUM TO THE ALKALINOUS METAL-CONTAINING FUSED ELECTROLYTE IN A RESTRICTED AREA ABOUT THE CATHODE OF THE CELL, AT A RATE EQUIVALENT TO ABOUT 1 GRAM OF

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