US2618549A - Method for the production of titanium - Google Patents

Description

Nov. 18," 1952 J. GLASSER ET AL METHOD FOR THE PRODUCTION OF TITANIUM Filed May 2, 1949 /a @maga/fz I H Ml@ fl; MZK

fnl/E17 227275 Patented Nov. 18, 1952 METHOD FOR THE PRODUCTION F TITANIUM Julian Glasser, LaI Grange, and Clifford! A. Hampel, Homewood, Ill., assignors, by mesne assignments, to Kennecott Copper Corporation,

New York, N. Y.

Application May 2, 1949, Serial No. 90,954

(Cl. 'I5-84) 4 Claims.

'I'he present invention relates to a method for producing pure ductile titanium in coarse crystalline form, or titanium invsponge or powder form.

The unusually desirable physical properties oi pure ductile titanium, such as its high strength, light weight and high corrosion resistance, make the metal ideal as a structural material. However, the metal has not come into important industrial use, due to the high cost of extracting or recovering the metal from its ores. themselves are plentiful and inexpensive, but conventional ore-reducing practices are of no avail in extracting the highly active titanium metal. Y

There are several known methods for preparing `pure, ductile titanium metal. In all of these known methods, the essential reaction is that between a, titanium compound 'and metal such as sodium, potassium. or magnesium. Thus, Hunter (JACS, vol. 32, 1910) heated a mixture oi highly puried titanium tetrachloride and sodium in a steel bomb capable of withstanding an internal pressure of 80,000 pounds. The resulting product was leached with water, resulting in the formation of a gray powder mixed with small rounded grains of titanium. The Hunter method is still used in laboratory preparations oi titanium, but it is evident that the process is not feasible on a commercial scale. y

The reduction of the titanium compounds by means of reactive metals of the type indicated is handicapped by the cost of the operations because ofthe high power requirements. the necessity of providing pure reducing metals, and the dimculty in handling the reducing agents.

The ores Further, the purity of the titanium metal thus produced has been limited by the processes used for separation of the reaction mixture, due to the extreme ainity of titanium metal for oxygen, nitrogen. and other common gases. Leaching the reaction product has the disadvantage that the titanium metal reacts with the water to liberate hydrogen and to form oxygen derivatives of titanium. i

It has also been suggested to decompose gaseous titanium tetraiodide on a hot filament or surface. This method is usually considered a purication step rather than a means for the production of elemental titanium, inasmuch as the iodide is normally prepared by the reaction of iodine with titanium metal Although the iodide process is capable of producing a very high purity titanium, the cost of rst obtaining the pure iodide is very high and the vacuum equipment and high temperatures required limit the quantity which can be prepared in a batch." j An object of the present invention is to pro-f1' vide an economical method for the of pure, ductile, Ielemental titanium.

Another object oi the invention is to provide 'a method for the production of titanium without' the necessityv of excessive power requirements;

Another object of the present invention is 'to provide a unitary proce s for the production of titanium from its ores, o; its halogenated derivaves.

Another object of the present invention is to.. provide, as a part of a unitary process for the. production of titanium, a method oi' growing titanium crystals large enough to be stable on exposure to air. A

Other and further objects of the invention will be apparent from the following description. In general, the present invention contemplates production the reduction oi a'titanium halide, such as thev tetrachloride, as by means of an alkali metal amalgam, such as a sodium amalgam, with the recovery of pure elemental titanium from the reaction mixture.

More. particularly, the reducing agent to be.

used in accordance with this invention is a sodium amalgam such as is produced in types of mercury-chlorine cells that are widely used in the field of caustic soda manufacture. The chlorine cell consists of an electrolytic cell in which sodium-mercury amalgam and chlorine are produced by the electrolysis of a brine solution be; tween a` moving mercury cathode and graphite anodes. The two most prevalent types of cellsare known as the rocking and stationary types. The chlorine cell also has the advantage of serving as a source of chlorine-which may be'used in the chlorination of a titanium ore consisting essentially of titanium dioxide to convert the latter to the tetrachloride.

Operating conditions in the chlorine cell can` be adjusted to produce a sodiu -mercury amal-- gam having a wide range of sodi m content. Sodium and mercury form solid compounds when the sodium content of the mixture is above about 0.5%. We prefer to use a sodium amalgam having a, sodium content from about 0.05 to 0.5% by weight. and preferably between 0.15% and 0.25% by weightsodium. The amalgam produced within this range of sodium concentratie .i is soluble in the liquid mercury. The viscosity of the amalgam solution does not become objectionably high until the sodium concentration is increased to -3' above 0.5% whereupon the sodium amalgammercury mixture becomes diilicult to handle.

By conducting the reduction of the titanium y -1ide in the presence of mercury, several adi \tages may be realized. First, the amalgam is much more'easily handled and carried into the reaction zone than a pure alkali metal. Further, the presence of mercury has been found to deactivate'the titanium metal produced in the reduction reaction, lessening the tendency of the metal to become oxidized. In addition. objectionable impurities. such as water, oxygen, nitrogen, hydrogen and many metals are not soluble or occluded in mercury or the amalgam and are thus not introduced into the titanium metal during the reduction step. In addition, heat transfer problems are simplified when an amalgam is used rather than an alkali metal. l

. As the titanium halide, we prefer to usetitanium tetrachloride, either in liquid or gaseous phase. This halide may be easily and economically 'produced by chlorinating ilmenite, rutile,

titanium oxide slags, pure titanium dioxide. or

range between 100 to 300 F. -The preferred range of temperaturev is between 190 to 220 F. The reaction is carried out in the presence of pureiner-t gases, such as helium, argon, neon, krypton and the like, to prevent contaminating the product with air or other gases. The propor-f tion of sodium (in the amalgam) to the titanium tetrachloride may be varied over a wide range, but we prefer to .use an excess of sodium over thatl theoretically required to completely reduce the titanium tetrachloride.

Intimate admixture of titanium tetrachloride and the sodium amalgam is essential in the reaction zone. Mixing of the reactants may be accomplished by introducing liquid titanium tetrachloride into a vigorouslyv stirred pool of sodium amalgam either from above orbelow the surface of the liquid amalgam. Intimate contact of the reactants can also be effected by bubbling liquid titanium tetrachloride through a liquid sodium amalgam. Another method of mixing is by runninga jet of ilnely dispersed liquid titanium4 tetrachloride or gaseous titanium tetrachloride into a A,iet of finely divided liquid sodium amalgam. Since 'the' quantity of sodium amalgam involved will be much more than the quantity of titanium tetrachloride, the relative proportions of the ingredients entering the reaction zone may be controlled by using the amalgam as a pumping fluid. Through proper arrangement of Jets or nozzles, the amalgam can pump the desired amount of titanium tetrachloride into the reaction zone in venturi or aspirator fashion. In addition, the amalgam may be added directly, with agitation, to a supply of -titanium tetrachloride in the reactor.

` To facilitate further reaction after initial mixing of the reactants, it is important to keep the reactants agitated in the reaction zone by suitable mechanical means.

' pressure- The reductionin-the reaction zone is completed in a'short period of time and proceeds smoothly without any violence.

The reaction product is a finely divided black powder that floats on the surface of mercury or the spent amalgam. Individual particles of this powder have diameters in the-range of 0.1 to 10 microns. The mercury or spent amalgam may be drained or filtered oil! by any well known gravity separation means such as by the use of a gold seal type filter. The spent amalgam, which will normally contain less than about 0.10 sodium, may then be recycled to the cell plant.

oxidizing conditions, and preferably under a vacuum. normally less than about` 0.01 mm. pressure and usually on the order of about 0.0001 mm.

Instead of using a vacuum, the furnacing zone may be filled with an inert gas of the type mentioned above, in which case pressures above or below atmospheric may be used. The transfer from the reduction zone to the furnacing system may be effected by gravity, or by a suitable type conveyor.

The reaction product in the furnacing operation is first subjected to a temperature in the range from about 400 to 700 F. to distill oif the residual mercury. Normally, the residual mercury4 will be on the order of about 1% of the mercury introduced into the reduction zone. During the furnacing operation, proper precautions must be taken to prevent the powder from blowing out of the furnace. This may be accomplished by placing a screen over the furnace pot to retain the powder at the base of the furnace.

. After the mercury is distilled oil, the remaining product, containing sodium chloride, titanium metal and any titanium sub-chlorides, is heated in a non-oxidizing atmosphere to temperatures above 1500 F. usually from 1500 to 2000 F. to separate the sodium chloride from the mix-ture. At these temperatures, any sub-chlorides of titanium present in the mixture are decomposed or distilled oilat reduced pressures. When performing the furnacing operation under conditions of about 0.0001 mm. pressure, substantially al1 of the sodium chloride will be distilled at a temperature in the range of about 1800 -to 2000 F. and will condense on the colder walls of the furnace. Alternatively, some residual sodium chloride may be retained to be drained or distilled off in-a subsequent melting operation.

The residue remaining in the furnace after the removal of sodium chloride consists essentially of pure, ductile titanium crystals. The individual crystals are cemented together during the furnacing operation to form agglomerates having crystal sizes much larger than the particle size resulting from the original reaction The crystals thus produced are stable in air, water. and acids, and may be easily handled for subsequent melting and alloying operations. It is quite possible that the molten sodium chloride present in the separating furnace serves as a matrix for promoting the growth of the crystalline agglomerates. Accordingly, it is sometimes desirable to retain the sodium chloride in the separating furnace without volatilizing the same, but removing it from the metallic titanium by leaching or subsequent melting.

It is to be understood that the growth of titanium crystals from a mixture of fine titanium powder and sodium chloride, with or without subchlorides of titanium, is not restricted toY the source of finely divided metal herein described, but may be used with other processes that produce a finely divided titanium powder. In addition, other alkali metal and alkaline earth metal halides, for example, potassium chloride, calcium chloride and magnesium chloride or other halides may be used in place of sodium chloride, at temperatures above the melting point of the respective halide. Y

'I'he crystals of titanium produced in the furnacing operation may also be compressed and sintered into coherent masses.

The crystals recovered from the furnacing operation contain more than 99% titanium and are extremely ductile. The purest and most ductile crystals appear to be the largest. The largest crystals have a Vickers hardness in the range from about 95 to 135 and contain more than,

99.9% titanium. This is equivalent to the purest and most ductile titanium metal prepared by other processes. The crystals themselves may be cold rolled to about 50% reduction in thickness.

A further description in the process proposed will be made in connection with the attached ow diagram, which shows one embodiment of the present invention. Y

Relatively large quantities of mercury are introduced into the cell plant which comprises a conventional mercury-chlorine cell. The mercury leaving the cell plant contains sodium metal in the form of an amalgam, having a sodium content determined by the operating conditions in the cell plant. Preferably, a sodium amalgam containing about 0.2% sodium, and having enough sodium to at least theoretically completely reduce the subsequently added TiCl4, is introduced into a reactor plant lled with an inert gas of the type described and maintained at a temperature between 100 and 300 F. Into the reactor plant is also introduced titanium tetrachloride. The reaction mixture leaving the reactor plant contains the original mercury, sodium chloride, and a powdery reaction product which is probably a mixture of titanium metal and titanium sub-chlorides (TiCh).

The reaction mixture is next passed into a suitable mercury filter or draining system, where approximately 99% of the mercury is recovered and recycled to the cell plant as shown. The mixture leaving the mercury filter, containing residual mercury, sodium chloride, and the metallic titanium-containing product is next passed to a separating furnace where about 80% of the sodium chloride present is vaporized oi or drained oif as a liquid. The sodium chloride recovered from the furnacing operation may be recycled to the cell plant, together with the rest of the sodium chloride recovered from the subsequent melting furnace, with the addition of water to form a brine solution. Any titanium sub-halides which are not decomposed in the separating furnace may be removed for disposal or recycling. Ihe residual mercury, which will normally be about 1% of the mercury originally present in the reaction mixture, is recovered from the separating furnace and also recycled to the cell plant in conjunction with mercury recovered from the filtering operation.

ing furnace operating under vacuum, or in the presence of inert gases, where the remaining sodium chloride is distilled or melted off and the titanium melted for subsequent casting. It is to be understood that the melting operation may be eliminated, and the titanium crystals resulting from the treatment in the separating furnace may'be compacted as in conventional powder metallurgy procedures. In this event, the stable titanium crystals may be separated from the titanium-sodium` chloride mixture leaving the separating furnace by leaching out the sodium chloride with water. As discussed hereinabove, the titanium crystals grow in the separating furnace to a stable form unaffected by water so that leaching with water will suiiice to separate the sodium chloride from the mixture without any deleterious effect on the titanium metal.

Extended exposure of the crystals to the conditions present in the separating furnace results in the sheets of titanium metal which may be recovered without the necessity of further melting or powder metallurgy processes.

The above flow diagram presents one embodiment of the present invention, but it will be evident that various modifications can be made in the process herein disclosed without departing from the spirit of the invention, and it is not our intention to limit the scope of the invention other than necessitated by the scope of the appended claims.

We claim as our invention:

1. The method of producing elemental titanium from titanium tetrachloride, which comprises vigorously mixing titanium tetrachloride with sodium amalgam in the presence of an inert gas, the sodium content of said sodium amalgam being suicient theoretically to completely reduce said titanium tetrachloride to titanium, continuing to vigorously agitator the reactants until a reaction mass of elemental titanium, sodium chloride and spent amalgam results, separating the sodium chloride and spent amalgam from the titanium and recovering elemental titanium.

2. The method of producing elemental titanium from titanium tetrachloride,- which comprises vigorously mixing titanium tetrachloride with sodium amalgam in the presence of an inert gas, the sodium content of said sodium amalgam being suicient theoretically to completely reduce said titanium tetrachloride to titanium, continuing to vigorously agitate the reactants until a reaction mass of elemental titanium, sodium chloride, sub-chlorides of titanium and spent amalgam results, removing a substantial amount of mercury from said reaction mass, transferring the remaining reaction mass to a, furnacing zone without exposure to the air, heating said remaining reaction mass in said furnacing zone to distill oi sodium chloride and decompose sub-chlorides of titanium present, and recoveringas the residue in said furnacing zone ductile titanium` crystals.

3. The method of producing elemental titanium from titanium tetrachloride, which comprises vigorously mixing titanium tetrachloride with sodium amalgam in the presence of an inert gas. the sodium content of said sodium amalgam being suiiicient theoretically to completely reduce said titanium tetrachloride to titanium, continuing to vigorously agitate the reactants until a reaction mass of elemental titanium, sodium chloride, sub-chlorides of titanium and spent amalgam results, removing a substantial amount of mercury from said reaction mass, transferring the remaining reaction mass to a fumacing zone without exposure to the air, heating said remaining reaction mass in said furnacing zone to a temperature of at least 1500 F. under vacuum conditions to separate sodium chloride and decompose sub-chlorides of titanium present, and recovering as the residue in said {urnacing zone ductile titanium crystals.

4. The method oi producing elemental titanium from titanium tetrachloride, which comprises vigorously mixing titanium tetrachloride with sodium amalgam in the presence of an inert gas, the sodium content of said sodium amalgam being suillcient theoretically to completely reduce said titanium tetrachloride to titanium, continuing to vigorously agitate the reactants until a reaction mass of elemental titanium, sodium chloride, sub-chlorides of titanium and spent amalgam results, removing a substantial amount of mercury from said reaction mass. transferring the remaining reaction mass to a iurnacing zone without exposure to the air, heating said remaining reaction mass in said furnacing zone to a temperature of between about 1500 and 2000v F.

. in a non-oxidizing atmosphere to remove at least a portion of the sodium chloride and decompose sub-chlorides of titanium present. and further 8 heating the remaining mixture containing titanium and residual sodium ,chloride to a sumciently high temperature -to voiatilize said residual sodium chloride and to melt said titanium.

JULIAN GLASSER.. CLIFFORD A. HAMPEL.

REFERENCES CITED The following references arey of record in the ille of this patent: f

UNITED STATES PATENTS Number Name Date 2,148,345 Freudenberg Feb. 2i, 1939 2,205,854 Kroll June 25, 1940 2,482,127 schlechten et al. Sept. 20, 1949 2,564,337 Maddex Aug. 14, 1951 OTHER REFERENCES

Claims (1)

1. THE METHOD OF PRODUCING ELEMENT TITANIUM FROM TITANIUM TETRACHLORIDE, WHICH COMPRISES VIGOROUSLY MIXING TITANIUM TETRACHLORIDE WITH SODIUM AMALGAM IN THE PRESENCE OF AN INERT GAS, THE SODIUM CONTENT OF SAID SODIUM AMALGAM BEING SUFFICEINT THEORETICALLY TO COMPLETELY REDUCE SAID TITANIUM TETRACHLORIDE TO TITANIUM CONTINUING TO VIGOROUSLY AGITATE THE REACTANTS UNTIL A REACTION MASS OF ELEMENTAL TITANIUM, SODIUM CHLORIDE AND SPENT AMALGAM RESULTS, SEPARATING

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