US 2783196 A
Description (OCR text may contain errors)
Feb. 26 1957 B. B. RANEY METHOD 0F PRODUCING TITANIUM AND ZTRCONIUM.
Filed March 19, 1952 INVENTOR 401, ATTORNEY5 RIETI-10D FR PRODUCING TITANIUM AND ZIRCONIUM Ben B. Raney, Lintomlnd., assign'or to Chicago Deveiopment Corporation of Delaware, Riverdale, Md.
f Application March 19, 1952, serial No. 277,445
' 1 claim.'v (c1. 204-64) This invention relates to the production of the metals, titanium and zirconium. It has for its object the production of such' metals.'substantially'free from oxygen.
In my copending applica-tions, Serial No'. 230,336, filed .luney '.7," 1951,' 'Serial No.'256,385, filed November 14, 1951 and Serial No. 152,175 liled March 27, 1950, I have disclosed methods which-'are' applicable to the production of titanium and zirconium, and this 'application may be considered a continuation in part of these applications, In my application, Ser. No. 152,175, filedl March 27, 1950, I have disclosed the reduction of titanium halides by nascent alkali or alkaline earth metals formed at the cathode in the electrolysis of halides of these metals. In my application, Serial No. 230,336, filed June 7, 1951., I have disclosed the chlorination of titanium containing oxygen at an anode in an electrolytic cell and the reduction of the chloride so formed, by a solution of alkali or alkaline earth metal in a halide of these metals, which is formed at the cathode in such a cell.` In'my copending application Serial No. 256,385, filed November 14, 1951, I have disclosed reduction of vmetal compounds in situ by a solution of alkali or alkaline earth. meta-l in a molten chloride of such metals. Y
4In the present application, I `disclose the formation of chlorides of titanium and zirconium by the anodic chlorination .of titaniferous or zirconiferous oxygen-containing metal according to the equation as illustrated for titanium:
i' ATiOy-f- (x-Jy ClafgyTiOz-l- (x*];y)TiCl2 This reaction takes place at the anode in a molten bath of alkali or alkaline earth metal chlorides.
The .present application discloses a separation of the TiOz or ZrOz formed, from the solution of TiClz or ZrClz in the molten chlorides. This separation is not disclosed in my copending applications.
Finally, the present application 'discloses a new combination of stepsv to produce pure metals from oxygencontaining material and apparatus for carrying out these steps.
IMy present invention consists in carrying out at least some of the following.. steps, illustrated for titanium:
f(l) The reduction of titaniferous oxygen-containing material to a metallicA alloy. v
(2) The chlorination ofthe titanium-oxygen combination at the anode in an electrolytic cell in the presence of a bath of ,molten metallic chlorides containing at least one alkali vor alkaline, earth chloride with an amount of chlorinating agent.l notV in excess of that necessary to form TiClz and TiOz from'the titanium-present whereby to form a solution of 'TiCla .in the-molten chloride bath.
'(3) Separating the solution of TiClz' in the molten chloride bath from the insoluble residue.
l(4) 'Reducing the TiClz in themolten chloride bath to metallic titanium at the cathode.
(5) Separating the titanium from the fused salts, and returning the fused salts to the second step.
Each'of these steps may bel carried out in various ways. The starting compound of titanium and oxygen may, for
2 example, be titanium metal scrap, containing oxygen. It is preferable that the raw material contain no chlorinatable material other than the titanium compound. Otherwise, provision must be made to remove such impurity in the third step of the process, in order to avoid contamination t of the titanium metal produced. The TiOz which is obtained as a residue from the chlorination step may be purified and reduced, for example, by heating with carbon. The chlorination step may be carried on by including the titanium-oxygen combination to be chlorinated in a conducting electrode which is made an anode in the fused chloride bath. This procedure provides a suitable excess of the titanium to be chlorinated. The molten chloride may be a single salt, such as LiCl, or it may be a mixture of alkali or alkaline earth metal chlorides. For the purposes of this description, magnesium is considered an alkaline earth metal. The separation of the fused chloride containing TiClz may be made, for example, by hot itration through a bed of broken solids, or by means ot a centrifuge. lf separation is accomplished by a bed of broken solids, at least part of such bed may be metallic titanium. This titanium will react with, and remove the metals which may have been chlorinated from the raw material, and which are more readily reduced than titanium. iron is an example of an impurity which may be removed in this way. The reduction of the TiClz by an alkali or alkaline earth metal is accomplished when anodic chlorination is used, by introducing a cathode into the fused salt containing TiClz, andV which has been separated from the insoluble residue. ln this procedure, it is of course necessary that the fused salt electrolytic bath be continuous from step 2 through step 4. The separation of the metallic titanium from the fused salt may be accomplished by filtering or centrifuging. The metalfree fused salt so recovered may be returned to step 2. The separated ltitanium may be freed from the last traces of salt by washing with water. In certain instances, the titanium metal may be recovered in massive, rather than particulate form, and its separation may Vtherefore be greatly simplified.
The temperature for carrying out my inventionV is not critical. t may be anywhere above the melting point of the salt bath, but below the temperature at Which Volatilization becomes objectionable. In general, I prefer salt mix-v tures which can be used in the range 60G-800 C.
In the above and further description of my process l herein, I sometimes discuss only titanium. My process is applicable to zirconium, using the identical steps.
In carrying out my process as described, I prevent contact of the fused salt with oxygen or water vapor. This may be done by maintaining the apparatus complete ly filled with salt, or by providing an inert atmosphere.
In one embodiment of my invention Va fused salt is fed into an anode compartment of an electrolytic cell and made to flow around the anode rapidly and through a filter into a compartment containing an inert conduct-ing cathode, for example iron or graphite, a solution of alkali or alkaline earth metal in the fused salt is formed at this cathode and is admixed with the fused salt flowing through the filter to produce the tinely divided metal dispersed these particles the iilter may be composed. of somewhat.
larger particles of the same metal which may be recovered for refuse by screening on a size basis or iron particles may beused and separated magnetically. The metal particles formed in the bath may be themselves used as a filter bed if the bath is allowed to settle somewhat to form such a bed. The filtrate cake formed in this way is not contaminated with other material. It may be conveniently separated and pressed under -50 tons/sq. in. at a temperature where the salt is molten to remove the salts and consolidate it into solid metal. This solid metal is ready to fabricate.
In the figure, I have illustrated an apparatus for carrying out my invention. It consists of a ceramic cell which is heated to a temperature necessary to melt the chlorides. The means for maintaining such temperature are not illustrated in the figure, but are conventional for maintaining molten salts in ceramic chambers as for the heat treatment of metal parts. Referring to the figure, the chamber A is separated from the remainder of the cell by a perforated partition. The chamber A is also connected by the large conduit, K, with chamber F which is likewise separated from the remainder of the cell by a perforated partition. The chamber F is provided with a pump I, so arranged as to circulate the fused salts into the chamber F from the remainder of the cell, and out through the conduit K, and thence into chamber A to be again drawn through the cell. The chamber B is provided with the anodes G. These anodes are made from the titaniferous oxygen-containing material, from which the metal is to be made. They may be made conducting by the addition of graphite. The fused salts are forced through the perforated partition from chamber A around the anodes G, in chamber B, and thence through a bed of filter material C. This filter material is held between two perforated partitions. It may be removed periodically through outlet J1 in the bottom of the cell. New filter material may be filled in at the top. The action of the pump I forces the fused salts through the filter C, and into the cathode chamber D. In the cathode chamber, there are several cathodes H, between which the filtered fused salts pass. After passing between the cathodes H, the fused salts contain reduced metal. This reduced metal is removed in filter E, which is retained between two perforated partitions. The material of filter E may be discharged through thc outlet I2, and new filter material supplied at the top. The metal is recovered from the filter material. The fused salts after removal :of the metal by filter E are returned 4to chamber F, from which they are re-circulated through the cell. The cell is provided with a tight fitting cover, not shown in the figure, and a neutral atmosphere is maintained in the cell, above the fused salts. r
The temperature for the practice of my invention depends on the anode material and the salts used. The temperature is preferably from 50l00 C. above the melting point of the salts and is limited as to high temperature only by excessive volatilization of the salt; with anodes composed essentially of the metals, temperatures as low as 450 C. may be used.
The current density at the anode should be at least l50 amperes/sq. ft. and `the voltage at least 2.0. In the interest :of economy, much higher current densities will be used land voltages up to 9.0 volts. The upper limit of current density will be determined by excessive heating and volatilization of the bath.
Having now described my invention in its general aspects, I will illustrate it by the following examples:
Example I filter between the cathode compartment and the pumpy compartment istitanium particles. In carrying out this example, the pump is operated at such a rate that precipitation of the. titanium particles takes place at the en trance `.of the cathode compartment. That is, reduction takes place by a solution of calcium in the fused chlorides. The material in the filters is periodically replaced by adding the filter bed material at the top, and withdrawing the material at the bottom. The metallic titanium from the second filter is freed from salt by washing with water.
Example II In Example II, I proceed exactly as in Example I, except that the rate of operationV of the pump is so regulated that less than all of the titanium chloride in solution in the salt is reduced to titanium metal during passage through the cathode compartment. Titanium metal is deposited on the cathode by reduction lof-a portion of the chloride. In order to insure this excess at the start of the operation, I add a small amount of chlorine at the anode. By careful regulation of the rate of flow of the electrolyte, a very slight excess of TiClzcan be maintained in the cathode compartment withI only very small and infrequent additions of chlorine at the anode. When the cell is operated with an excess of TiClz in the cathode compartment the titaniummetal is deposited on the cath-- odes, and may be removed with them. Adhering salt may be readily washed off.
Examplel III I proceed as in Example II and when thc relatively massive metal is formed on the cathodes I press it to the bottom of the chamber where it accumulates as a mass of metal intermixed with some fused salt. I remove this mass from the bath and press it at 25 tons/sq. in. at 750 C. The salts are forced out of the metal and a solid workable piece of metal obtained.
Example IV I proceed as in Example I except that I prepare the anode from a ti-tanium oxide containing less oxygen than TiOz, and metallic titanium. The proportions used are such that the resulting product is a solid solution of oxygen in metallic titanium. Such solid solutions are electrically conducting and may be used` as anodes without contamination of the melt with carbon. The limit or" these solid solutions'is about 13% oxygen. The titanium used may be scrap or some of the product of the process used as a circulating load. The metal and oxide are heated to SOO-1000" C. in Ithe absence of air to produce a sintered product for use as anode. The TiOz which is formed from the oxygen in the anode is'separated from the anolyte by filtration as in Example I.
What is claimed :is:
Process of producing substantially pure/titanium from crude titanium metal containing oxygen in solid solution, which comprises making the oxygen-containing titanium metal the anode in an electrolytic cell having communieating anode and cathode zones and means for preventing passage of particulate solids from one to the other of said zones, said cell being provided with a conducting cathode and with an electrolyte composed of at least one alkalinous metal chloride free from oxygen and with a protective inert atmosphere above said electrolyte, maintain- 'ing the cell contents at a temperature from 50 to 100 C. above the melting point of the alkalinous metal chloride, continuously moving electrolyte from the anode zone to the cathode zone and over said cathode, passing a unidirectional current between anode and cathode at a current density of at least amperes per square inch of anode surface and at an impressed voltage of from 2 to 9 volts, whereby to form in theelectrolyte, in said anode zone, a solution of titanium di-chloride and partcula-te titanium dioxide, adding chlorine adjacent the anode, separating solid residue comprising said particulate titanium dioxide from said solution, passing'the solution into the cathodeezone and oversaid cathode, the amount vol".ch1o- Winter Aug. 19, 1952 Reimert Nov. 4, 1952 Aagaard et al Dec. 16, 1952 Steinberg ,et a1 Apr. 26, 1955 FOREIGN PATENTS Great Britain Apr. 5, 1950 Switzerland Nov. 1, 1948 Great Britain 1-- May 6, 1943 OTHER REFERENCES Chapters in the Chemistry of the Less Familiar Elements, by Hopkins, Vol. 1, chap. 11, page 7, published 5 Tine added being such, and said solution being passed over 2,607,674 said cathode at such a rate, as to provide that the electro- 2,616,784 lyte after passing over the cathode contains a significant 2,622,005 content of titanium di-chloride, thereby depositing pure ti- 2,707,169 tanium metal on the cathode suciently adherent to the 5 latter that the deposit may be removed With the cathode, and removing associated electrolyte from such deposit. References Cited in the Ele of this patent 5 5 3,056 UNITED STATES PATENTS 1o 1,861,625 Driggs et al. .lune 7, 1932 2,205,854 Kroll June 25, 1940 2,413,411 Kroll Dec. 31, 1946 in 1939. 2,550,447 Blumenthal Apr. 24, 1951 2,564,337 Maddex Aug. 14, 1951 15 (19 Transactions of The Electrochemical Society, vol. 87
45), pages 551 thru 567, article by Kroll.