US2618550A - Method for the production of titanium - Google Patents

Description

Nov; 18, 1952 c, HAMPEL ETAL 2,613,550

METHOD FOR THE PRODUCTION OF TITANIUM Filed Jan. 4, 1952 ci Na.Cl SOLUTION l &

MERCURY CATHODE csu.

l/Ja m AMALGAM is 4' AMALGAM CONCENTRATOR 4 REACTOR A REACTION PRODUCT 19 /23 sm-1n AMALGAM-A MERCURY REMOVAL v 25 27 26 NaCl SALT REMOVAL a T| CRYSTALS hyez-zfar 5 g g/k fink a, 4%

Patented Nov. 18, 1952 UNITED sr METHOD FOR THE PRODUCTION OF TITANIUM Application January 4, 1952, Serial No. 264,904

8 Claims. 1

The present invention is concerned with a method for producing titanium in ingot or coarse crystalline form, or titanium in sponge or powder form.

Metallic titanium has physical properties which suggest the applicability of this metal for a large number of varied uses. Pure, ductile titanium has high strength, light weight and high corrosion resistance, making titanium a very suitable metal for the manufacture of aircraft parts, and other structural uses where such properties are -desirable. Its high specific resistance to sea water corrosion makes the application of titanium for the manufacturing of piping, fittings and valves for maritime purposes very attractive.

Titanium metal has not come into important industrial use because of the high cost of recovering the metal from its ores. Titanium ores themselves are plentiful and inexpens ve, but because of the high degree of activity of titanium in finely subdivided form and the inherent stability of its more common compounds, conventional ore-reducing processes are incapable of producing titanium metal in a pure state.

Several methods have previously been suggested for the production of elemental titanium from its'compounds. One such method involves the reduction of a titanium compound, such as a titanium halide, by the action of a reducing agent such as molten magnesium.

Another process which is capable of producing elemental titanium involves the reduction of a titanium compound with metallic sodium under conditions of high temperatures and pressures.

Still another method suggested for producing relatively pure titanium is one involving the thermal decomposition of gaseous titanium tetraiodide on a heated surface.

Each of the above mentioned processes has inherent disadvantages which limit their usefulness in commercial scale operations. The reduction of titanium tetrachloride with molten magnesium is difficult to carry out because of the high temperatures required in maintaining the magnesium in a fluid state and the difficulty in agitating the reactants under these conditions.

The reduction of titanium halides with metallic sodium necessarily carries with it all of the problems incident to conducting reaction systems at elevated temperatures and pressures, primarily because the reaction of titanium halides with metallic sodium is extremely violent.

The thermal decomposition processhas the disadvantage that it requires a high'temperature in 2 the reduction zone and a high purity of the titanium tetraiodide to yield a suitable product. It is, in essence, a purification process and in most cases requires a source of impure titanium from which the titanium tetraiodide can be prepared.

The reduction of titanium compounds by means of reactive metals of the type mentioned is handicapped by the cost of the operation because of the high power requirements, the necessity of providing pure reducing metals in nonrecoverable excess, and the difiiculty in handling the reducing agents. Further, the continuity of production and the purity of the titanium metal produced have been limited by the processes used for separation of the reaction products, due to the extreme affinity of titanium metal in subdivided form for oxygen, nitrogen, and other common gases. Leaching the reaction product to remove the chloride salts of the reducing metal has the disadvantage that the titanium metal reacts with water to liberate hydrogen and to form oxygen derivatives of titanium.

An object of the present invention is to provide an economical method for the production of pure, ductile titanium metal.

Another object of the present invention is to provide a process for the production of elemental titanium from a titanium halide using a liquid-liquid or gas-liquid low temperature reaction system.

Another object of the present invention is to provide a method for the production of titanium from inexpensive materials at relatively low temperatures, thereby decreasing the over-all cost of recovering the metal.

Still another object of the present invention is to provide a process, which can be operated as a batch process, or in a continuous manner, the process being characterized by substantially complete consumption of both the titanium compound and the reducing agent involved in the reaction.

In our copending U. S. applications, Serial No. 90,954, filed May 2, 1949, and Serial No. 161,448, filed May 11, 1950, both entitled Method for the Production of Titanium, there are described processes for the recovery of metallic titanium from titanium compounds. The basic reaction involved is the reduction of a titanium halide with an alkali metal amalgam. The present application is a continuation-in-part of both the above identified applications.

As pointed out in the previous applications,

the advantages accruing from the use of an' 3 amalgam of an alkali metal as the reducing agent as compared to the use of the alkali metal itself are very distinct. Such amalgams give the reducing process a mobility not possible in processes involving the use of reducing metals by themselves, such as magnesium or sodium, as the presence of the alkali metal amalgam dilutes the vigor of the reduction while achieving rapid and essentially complete reduction. The temperature and pressure conditions for the reaction are far less stringent than those necessarily employed for the reduct on of titanium halides when using metallic reducing agents by themselves. Furthermore, the alkali metal in the form of an amalgam is much less costly than the free metal.

By carrying out the reaction in the medium of a liquid alkali metal amalgam, intimate contact between the titanium compound and the reducing agent is assured since agitation is made much more convenient. The temperatures involved in the reaction zone are quite low and reaction proceeds efliciently at temperatures up to and including the boiling point of the amalgam used.

Conducting the reduction of the titanium halide in the presence of mercury gives rise to several distinct advantages. First, the amalgam is much more easily handled and introduced into the reaction zone than would be the alkali metal by itself. Further, as explained in more detail later, after the amalgam has been partially stripped of its alkali metal content to a concentration below the optimum concentration for essentially complet reduction of titanium tetrachloride to elemental titanium, the spent amalgam can be recirculated to another stage of the process for refortiflcation or reconcentration, whereby very high consumption efiiciencies of the alkali metal are realized. In addition, objectionabl impurities such as water, oxygen, nitrogen, as well as many metals such as iron, do not become dissolved or occluded in the mercury or the amalgam, thus are not introduced into the titanium metal during the reduction step. Water can be removed easily from the amalgam by a simple drying step.

In addition, heat transfer problems are simplifled when an amalgam is used in preference to a metallic reducing agent. The heat of reaction is consumed in heating the amalgam to a higher temperature or is easily dissipated, a situation not experienced when metallic reducing agents, by themselves such as sodium or magnesium, are used as such.

The preferred titanium compounds which can b used in accordance with the aforementioned process are the titanium halides, particularly titanium tetrachloride. The latter halide can be easily and economically prepared by chlorinating ilmenite, rutile, titanium oxide slags, pure titanium dioxide, or similar compounds of titanium, in the presence of carbon and heat. The resulting titanium tetrachloride may be further purified by fractional distillation. Alternatively, titanium halides such as titanium dichloride, titanium trichloride, titanium tetrabromide,

titanium tetraiodide and the like may be emmetal content equivalent on anatomic basis to not over 2.5% of sodium in order that the reaction can be carried out in liquid-liquid phase at relatively low temperatures. This value of 2.5% of sodium corresponds to 18.3 atomic percent for any Of the alkali metals. Mercury and sodium form a series of intermetallic compounds having varying melting points. The melting point curve for the mercury-sodium system diops from the melting point of mercury, which is minus 39.9 C., to minus 48 C. for a eutectic containing 0.35 percent by weight of sodium, and rises sharply to a melting point of 158 C. for an amalgam containing 2.5 percent by weight of sodium, a percentage corresponding to the compound HgiNa. The curve further rises to a maximum of 358 C. for the melting point of a 5.4 per cent sodium amalgam, which represents the compound HgzNa. As the content of sodium is increased further, the melting point curve falls oil until it reaches a minimum of 21.5 C. at a sodium content of 39.5 percent by weight. In doing so, it passes through a series of peritectic points due to the formation of several mercurysodium compounds: HgaNaw, HINL, HgzNaa, HgzNas, and HgNaa. From the 39.5 percent by weight sodium content, the melting point curve rises gradually to a value of 975 C., the melting point of sodium.

While sodium amalgams of higher sodium content can be used for the eflective reduction of titanium tetrachloride to titanium metal, it is not necessary from a technical or economical point of view to use amalgams containing more than about 1.5 percent by weight of sodium. In particular, for the purpose of this invention, the use of sodium amalgams having sodium contents in the range from 0.5 to 1.5 percent by weight is preferred. The handling of the amalgam is facilitated by operating at these sodium concentrations in that special precautions to avoid solidiiication or freezing of the amalgam in lines and vessels are not so difficult to observe as is the case when higher sodium content amalgams are employed. In addition, the cost of preparing more concentrated amalgams does not Justify their use, since equivalent results can be obtained with the less concentrated amalgams.

In accordance with the present invention the reaction between titanium tetrachloride and an alkali metal amalgam is carried substantially to completion, that is, with a minimum amount of subhalides of titanium in the reaction mass at the end of the reaction. This is accomplished by so adjusting the quantities of the reactants that the amount of sodium amalgam present in the reaction zone provides in excess of four molar proportions of sodium for every molar proportion of titanium tetrachloride present, and furthermore, the alkali metal content in the amalgam is maintained at all times at a value of at least 3 atomic percent. In the case of sodium amalgams, this value represents a weight concentration of about 0.35 percent of sodium by weight of the amalgam, and for potassium amalgams, the corresponding value is about 0.6 percent by weight. It has been found that amalgains having a sodium content lower than about 0.35 percent by weight tend to reduce titanium tetrachloride initially and rapidly to solid titanium dichloride, which in turn is more slowly reduced to the metal. However, when the sodium content in the amalgam is maintained above 0.35 percent, by weight, and preferably between 0.5 and 1.5 percent, the tetrachloride is reduced to metal at a very rapid rate and the reaction goes to substantial completion.

Potassium amalgams are also suitable for use in the present process, but where potassium amalgams are employed, the potassium content is preferably in the range from 1.3 to 2.5 percent by weight.

The suitable sodium concentration range depends also upon whether the reduction is to be conducted in a batch or continuous fashion. In a batch process, sufllcient titanium tetrachloride is introduced into an amount of'sodium amalgam. the initial sodium concentration of which is in the range of 0.5 to 1.5 percent by weight, such that the reduction of the titanium tetrachloride to titanium metal can be carried to substantial completion without lowering the sodium content of the amalgam below about 0.35 percent.

In a continuous process the reaction products including titanium metal and sodium chloride, along with spent amalgam may be continuously removed from the reaction zone, while titanium tetrachloride and sodium amalgam are being fed into the reaction zone. If good agitation is maintained in the reaction zone, the withdrawn spent amalgam will have about the same sodium concentration as the average sodium content in the reactor. Thus, while fresh amalgam of a sodium content of 0.5 to 1.5 percent by weight is added, the withdrawn portion being withdrawn either continuously or periodically may have a lower concentration of sodium, which, however, should be maintained above about 0.35 percent by weight for good reduction efiiciency. In such a continuous process, the titanium tetrachloride and the fresh amalgam can be introduced into the reactor in such a manner that they are immediately and thoroughly mixed in order that the reaction may occur between the titanium tetrachloride and a sodium amalgam having a sodium content much higher than the average sodium content of the amalgam in the reactor.

The simplest method of preparing sodium amalgam for commercial scale operations is by the electrolysis of sodium chloride brine in a mercury cathode chlorine cell using graphite anodes. Such cells are widely used for the production of chlorine and sodium hydroxide, the latter being formed in a decomposer where water is caused to react with sodium amalgam circulated from the cell. For the operation of the present invention, the step of sodium hydroxide formation is eliminated and sodium amalgam is withdrawn directly from the cell while fresh mercury or dilute amalgam is returned to the cell. Use of this type of cell is especially advantageous since the chlorine which is coproduced with the sodium amalgam can be consumed in the chlorination of titanium ores or other titanium bearing materials for the preparation of titanium tetrachloride.

Mercury cathode chlorine cells can be operated to produce an amalgam containing as high as 0.5 percent by weight of sodium at good energy efliciencies. This amalgam can be converted into a more concentrated form either by adding the requisite amount of sodium metal to it, or by distilling mercury from the cell amalgam until the sodium content reaches the desired level, or by electrolyzing part of the cell amalgam in a secondary cell using a molten salt bath medium so that the sodium is deposited on a cathode from which it is removed for addition to the remaining cell amalgam while the mercury is returned to the primary mercury cathode chlorine cell.

It will be appreciated. of course, that the amal- I gam can also be prepared simply by mixing mercury and the solid alkali metal in proper-proportions.

On the drawing:

The accompanying sheet of drawings illustrates a fiow diagram of a plant designed for the production of metallic titanium using the mercury cathode cell as the source of the sodium amalgam. A further description of the present invention will be made in connection with this flow diagram.

As shown on the drawing:

Reference numeral l0 indicates generally a mercury cathode chlorine cell of the type previously described, including graphite anodes and a liquid mercury cathode. A sodium chloride solution, or brine, is introduced into the cell l0 through a line H, as indicated. The free chlorine liberated fromthe cell is directed as indicated by line l2 to another portion of the plant where it may be employed in the chlorination of titanium derivatives such as titanium oxides into titanium tetrachloride.

The sodium amalgam produced in the cell ill will ordinarily contain less sodium than the optimum value desired in the sodium amalgam used as the reducing agent in this process. For this reason, the relatively dilute sodium amalgam produced in the cell l0 may be passed as indicated by line I3 into an amalgam concentrator indicated generally at Id. In this stage, as previously discussed, the amalgam can be brought up to the proper sodium concentration by the addition of metallic sodium, or by distillation of some of the mercury contained in the dilute amalgam until the desired concentration is obtained.

After the amalgam has attained the desired sodium concentration in the amalgam concentrator M, the sodium amalgam, now ready to be used as the reducing agent, is pumped through a line l5 into a reactor l6. Titanium tetrachloride is introtuced into the reactor l6 through a line I 1.

It is essential for good reduction efliciency that an excess of sodium amalgam be present at all times in the reactor while the titanium tetrachloride is being added. In addition, the relative amounts of titanium tetrachloride and sodium amalgam fed into the reactor must bear an over all ratio of 4 or more moles of sodium in the amalgam to one mole of titanium tetrachloride introduced. Also, the titanium tetrachloride should be added to the amalgam and not vice versa. It is particularly important that the tetrachloride be added below the surface of the amalgam contained in the reactor I 6, as this minimizes the reaction which might otherwise occur between the titanium tetrachloride added and the finely divided titanium metal that has already been formed and that rises to the surface of the amalgam, along with the sodium chloride. That reaction is the following: 1

The above specified conditions insure high yields, and higher, of metallic titanium, and are adequately and easily met if the titanium tetrachloride is added to a reactor already filled to the desired level with a sodium amalgam containing 0.5 to 1.5 percent by weight sodium and if, in the operation of the process. the addition of further quantities of titanium tetrachloride and of sodium amalgam and the withdrawal of spent amalgam are all maintained in such balance that The titanium tetrachloride introduced into the reactor should be quickly and thoroughly dispersed into the sodium amalgam in the reactor, as by means of vigorous agitation of the amalam. This insures that the sodium content of the amalgam in the vicinity of the titanium tetrachloride feed inlet is not radically depleted and that replacement sodium is promptly brought to this point. An agitator is indicated in the attached drawings by the reference numeral [8.

The reaction between titanium tetrachloride and the liquid sodium amalgam may be carried out under widely varying temperature conditions, up to and including the boiling point of the amalgam used under the pressure prevailing in the reactor. However, at temperatures below about 100 C., the reduction rate and/or the efllciency of the reduction tends to decrease and deliberate cooling must be carried out to prevent the temperature from rising about that point. On the other hand, if the reaction is allowed to proceed without cooling, the heat of reaction will raise the temperature of the system to a point at which heat losses and feed preheating requirements equal to the heat of reaction, under a given set of operating conditions. If heat losses are reduced and the feeds adequately preheated externally of the reactor, the temperature may rise eventually to the boiling point of the amalgam. Such a result is not harmful to the reaction with respect to the reduction rate and efllciency.

If the reactor is operated at temperatures above the boiling point of titanium tetrachloride, 136

C., the latter is vaporized as it enters the reactor and reacts as a gas rather than as a liquid with the amalgam. The reduction of titanium tetrachloride to titanium metal proceeds eflectively whether the tetrachloride is in gaseous or in liquid phase. The boiling point of the titanium tetrachloride is, of course, raised if it is admitted against a static head of amalgam in the reactor or if a superatmospheric pressure is maintained in the reactor.

The reaction is conducted conveniently at atmospheric pressure, although subatmospheric or superatmospheric pressures can be employed. To prevent contamination of the titanium metal recovered, air or other reactive gases should be rigorously eliminated, and consequently the reactor IS should be filled with an atmosphere of inert gas such as argon or helium.

Under the aforementioned conditions, the reaction is very rapid and proceeds smoothly without violence to yield a bulky, finely divided mixture of powdered titanium and sodium chloride which tends to float on the surface of the atrialgam in the reactor. These reaction products can be removed intermittently or continuously by mechanical means from the surface of the amalgam, as by using a screw conveyor projecting into and over the surface of the amalgam in the reactor. The products carry a relatively large quantity of adherent residual amalgam, such that the mercury to titanium ratio in the reaction products is usually in the range of from about 25 to 100 to 1 by weight. This mercury is removed durin subsequent'processing by a combination of drainage and distillation.

Because the mercury admixed with the reaction products contains sodium and this sodium reacts with any incompletely reduced titanium chloride during the subsequent processing, the

initial reduction of the titanium tetrachloride to titanium metal need not be carried out to completion in the reactor. Thus, the term "good reduction efllciency is predicated upon the final completion of the reduction, during subsequent processing, by the sodium contained in the amalgam that adheres to the products removed from the reactor. For example, if the reaction products contain mercury and titanium in the ratio of 50 to 1, and themercury contains 0.35 percent sodium by weight, the initial reduction in the reaction need not be carried further than the point at which 82% of the titanium tetrachloride fed in has been reduced to titanium metal.

All of the titanium tetrachloride added to sodium amalgam of almost any concentration is reduced at least to titanium dichloride, if the ratio of sodium to titanium tetrachloride is at least equal to two moles of sodium to one of titanium tetrachloride. While the subsequent reduction of titanium dichloride to titanium metal by sodium amalgam in the reactor can be eflected, the rate is slow, due principally to the difiiculty of contacting or mixing the solid dichloride with the amalgam. It is therefore desirable to conduct the reaction of titanium tetrachloride with sodium amalgam under conditions such that an initial and direct reduction of titanium tetrachloride to metal is obtained. The conditions previously described are those which achieve substantially this result. However, since the heterogeneous nature of the system in the reactor renders improbable an absolutely complete primary reduction of titanium tetrachloride directly to titanium metal, some formation of titanium subchlorides may be expected. These subhalides are nevertheless largely converted to metal during their subsequent residence time in the reactor while exposed to sodium amalgam. In the great majority of cases, the over-all yield of titanium metal in the reaction as carried out in the reactor will be at least of the titanium introduced as titanium tetrachloride, and in many cases the yields are in the range from to Returning to the flow diagram, the spent amalgam is drained from the reactor l6 and may be passed, as by means of a line l9, back into the amalgam concentrator H for reconcentration. As previously mentioned. the spent amalgam should, in all cases, contain at least 0.35 percent sodium to insure that optimum reaction conditions are achieved in the reactor IS, with a maximum initial reduction of the titanium tetrachloride to metallic titanium in that stage.

The products of the reduction consist, of titanium, sodium chloride, sodium amalgam, and any incompletely reduced titanium subchlorides. The products are initially removed from the bulk of the amalgam present in the reactor it as by means of a conveyor, 9. scraper, or a plow, operating at the surface of the amalgam, or the amalgam can be drained off, depending upon whether the reactor is being operated continuously or batchwise. The mixture so removed may be in the form of a free-flowing powder, or soft lumps, or a thick, heavy sludge, depending upon the sodium concentration in the adhering amalgam, the temperature, and the mechanical means used to remove the reaction products from the reactor. For example, as disclosed in the copending application Serial No. 189,404, filed October 10, 1950 and assigned to the same assignee as the present invention, when a screw conveyor enclosed in a tube is used j 23 enteringthe the sodium chloride recovered from the sale removal zone 25 passed through aline *mation of thesodium i It shouldfurther be appease The reaction products are withdrawn fromv the reactor by any of the means previously described, and passed through a line 20 into a mercury removal zone 2|. action mixture may be treated for the separation of mercury by gradually heating the reaction mixture to about 600 0., either with or without the application of pressure to assist in squeezing the mercury from themixture. Alternatively, the mercury or spent amalgam may be drained or filtered 01f by other well known gravity separation means.

The mercury recovered from the mercury removal zone 2| may then be returned through a line 22 and line 23 back into the mercury cathode cell I 0.

After the removal of a major proportion of the mercury in the mercury removal zone 2|, the remaining reaction products are passed by means of a line 24 into a salt removal zone 25 where some or all of-the sodium chloride produced as a by-product of the reaction is removed. Conveniently, sodium chloride removal may be effected by heating the reaction mixture at a temperature above the melting point of sodium chloride (800 C.) to liquefy or volatilize the salt. At the same time, any traces of mercury remaining in the reaction product from the mercury removal zone 2| may also bevolatilized. The temperature in the salt removal zone is preferably maintained at a value from 800 to 950 C. for removal of the adherent salt by draining and/or by expressing the liquefied salt.

As an alternative, the sodium chloride may be retained in solid phase and removed in a subsequent melting operation.

Over 80% of the sodium chloride can be easily removed by drainage of sodium chloride at the elevated temperatures in the salt removal zone, and the resulting sintered mixture containing upwards of 50% titanium can be fed directly to an inert atmosphere arc melting furnace for the formation of titanium ingots. The titanium mass produced in this manner can also be formed into a coherent compact and fed as a consumable electrode into an inert atmosphere melting furnace copending applications Serial Nos. 165,346 and 165,347, filed May 31, 1950 and assigned to the same assignee as the present application. The sodium chloride associated with the reaction product is vaporized during the arc melting and condensed on cooler portions of the furnace housing from which it can be removed at intervals or continuously.

Any mercury separated in the salt removal zone may bepassed by means of "a line '26 into the line mercury cathode cell. Similarly,

can be collected, lv ed,' and (2,! back into the'mercury cathode cell for subsequent electrolysis in the foramalgam.

mentioned that the separamercury and. salt removal.

on "operation of the In zone 2!, the resuch as disclosed in zones should be conducted under non-oxidizing conditions, as for instance under an atmosphere of argon or helium.

After melting, the massive titanium recovered according to these processes contains at least about 99.5% Ti, has a Vickers hardness of. about to 250, and is extremely ductile.

The following examples will illustrate specific processes utilizing the principles or the present invention.

Example I Fifty pounds of sodium amalgam containing 0.78 percent by weight sodium were placed in a vertical, cylindrical reactor equipped with a stirring device, an inlet for titanium tetrachloride, an inlet and outlet for the amalgam; an inlet and outlet for an inert gas, and an enclosed screw conveyor located in a side housing attached at an upwardly inclined angle to the reactor wall so that the conveyor flights could pick up solids floating on the amalgam surface and convey them to a discharge point at the end oi the housing. After the reactor and amalgam had been heated to q a temperature of 140 C., and the conveyor to a temperature of 300 C. by means of electrical resistance windings around the reactor shell and the conveyor housing, titanium tetrachloride in liquid phase was admitted to the reactor at a central point one inch above the bottom and six inches below the amalgam surface and immediately beneath the stirrer. The reactor was maintained under a non-oxidizing atmosphere of argon. A feed rate of 20 ml. of titanium tetrachloride per minute was maintained for a period of six minutes. At the end of the addition' period, the temperature in the reactor had risen to (3., and the con centration of sodium in the amalgam had been decreased to 0.35 per cent by weight. A total of 2430 grams of reaction products, containing 50 grams of titanium, 250 grams of sodium chloride and 2130 grams of 0.35 percent sodium amalgam was removed by the screw conveyor in the form of soft lumps of finely divided solids. The reaction so conducted resulted in the reduction of practically 100 percent of the titanium tetrachloride to elemental titanium. The reaction mixture was heated to a temperature of 600 0., to remove substantially all the mercury by drainage the furnace. The mercury removal, salt removal, and titanium melting'were all carried out in an atmosphere of argon toprevent contamination of 'the metal with oxygen or nitrogen.

v Example II p Fifty 5tsds of sodium; amalgam ccntaining 1.l .perce1 1'jt sodium. byweight were placed in the same reactor as described in Example I, and-16.6

ml. of liquid titanium tetrachloride per minute were added over a minute period to the reactor. The temperature rose from an initial 140 C. to 170 C. at which value it was maintained by the use of water cooled coils on the reactor shell. The temperature of the conveyor was held at 300 C. by the electrical resistance winding on the conveyor housing. While the conveyor was removing the reaction products formed during this period, pounds of the sodium amalgam, now at a sodium concentration of 0.5 percent, were withdrawn from .the reactor and replaced by 25 pounds of sodium amalgam containing 1.1 percent sodium. To the resultant approximately 50 pounds of 0.8 percent sodium amalgam were added 83 ml. of titanium tetrachloride over a 10 minute period. By continuing this semi-continuous production of titanium with the withdrawal of dilute amalgam, addition of concentrated amalgam, and addition of titanium tetrachloride, a total of 250 grams of titanium were prepared and withdrawn from the reactor. The over-all reduction of titanium tetrachloride to metal was 84 percent and the mercury/titanium weight ratio in the removal reaction products was about 31/1. After removal by drainage and distillation of mercury from the reaction products so removed, enough sodium was contained in the residual mass to cause complete reduction to metal of the relatively small amount of titanium dichloride present therein when the residual mass was heated gradually to a temperature of 538 C. in a perforated tube. The temperature of the mass was then raised to 1000 C. and liquid sodium chloride was drained from the matrix of titanium crystals which remained. The remaining product, containing about 75% titanium and 25% sodium chloride by weight was introduced into an arc melting furnace as in Example I, to produce a ductile titanium ingot of high purity (about 99.5%).

As in Example I, the reduction, purification, and melting operation were carried out in an inert atmosphere of argon.

The process of the foregoing examples can be carried out equally as well on a potassium cycle, using potassium amalgam prepared in a mercury cathode cell, and forming and handling potassium chloride instead of sodium chloride in the reaction and separation stages. The effective and preferred potassium concentration range in the potassium amalgam utilized is from 1.3 to 2.5 percent by weight and the lower limit of residual amalgam in the reactor is about 0.5 percent by weight of potassium in the amalgam. Other conditions of operation are essentially the same as for. the sodium cycle described above.

From the foregoing it will be evident that the method described represents a substantial improvement over the method described in the previously mentioned applications, Serial Nos. 90,954 and 161,448, in that the direct reduction of the titanium tetrahalide to metallic titanium is facilitated. with a minimum production of the subhalides of titanium in the reaction mass. The process of the present invention also has the advantages described in the aforementioned applications in that the reaction can be conveniently carried out in liquid-liquid phase at relatively low temperatures.

It will be understood that modifications and variations may be eflected with departing from the scope of the novel concepts of the present invention.

We claim as our invention:

1. The process of producing elemental titanium which comprises introducing titanium tetrachloride with vigorous agitation into a supply of an alkali metal amalgam maintained in a reaction zone in the presence of an inert gas and at a temperature not exceeding the boiling point of the amalgam, the molar amount of alkali metal in said amalgam being in excess of four times the molar amount of the titanium tetrachloride introduced, continuing agitation and maintaining the alkali metal concentration in said amalgam at a value of at least 3 atomic per- ,oentbut not over 18.3 atomic percent by weight during the reaction of said titanium tetrachloride with said amalgam until a reaction product containing elemental titanium, alkali metal chloride and amalgam results, removing said reaction product from said reaction zone, separating .the alkali metal chloride and amalgam from the titanium in said removed reaction product and v recovering elemental titanium therefrom.

2. The process of producing elemental titanium which comprises introducing titanium tetrachloride into a supply of an alkali metal amalgam maintained in a reaction zone in the presence of an inert gas and at a temperature in the range from 100 C. to the boiling point of the amalgam, the molar amount of the alkali metal in said amalgam being in excess of four times the molar amount of the titanium tetrachloride introduced, maintaining the alkali metal concentration in said amalgam at a value of at least 3 atomic pr= cent but not over about 18.3 atomic percent by weight during the reaction of said titanium tetrachloride with said amalgam, vigorously agitating said titanium tetrachloride amalgam until a reaction product containing elemental titanium, alkali metal chloride and admixed amalgam results, removing said reaction product from said reaction zone, separating the alkali metal chloride and amalgam from the titanium in said removed reaction product and recovering elemental titanium therefrom.

. uid sodium amalgam having a sodium content of from 0.5 to 1.5% by weight, said amalgam being maintained in a reaction zone in the presence of an inert gas and at a temperature in the range from 100 C. to the boiling point of the amalgam continuing agitation and maintaining the sodium content in said amalgam at a value of at least 0.35% but not over about 2.5% by weight during the reaction between said titanium tetrachloride and said amalgam until at least of the titanium tetrachloride has been reduced to metallic titanium and a reaction product containing elemental titanium, sodium chloride and admixed amalgam results, removing said reaction product from said reaction zone, separating the sodium chloride and admixed amalgam from said reaction product so-removed, and recovering elemental titanium therefrom.

4. The method of producing elemental titanium which comprises introducing liquid titanium tetrachloride below the surface of an agitated supply of sodium amalgam in a reaction zone having an inert gaseous atmosphere and a temperature in the range from C. to the boiling point of the amalgam, said amalgam at the start said supply of sodium ama'lgam at the start of the reaction being in excess or four times the total molar amount of titanium tetrachloride introduced into said supply of sodium amalgam, continuing agitation and maintaining the sodium content in said amalgam at a value of at least 0.35% but not over about 2.5% by weight during the reaction between said titanium tetrachloride and said amalgam until said reaction is substantially complete to produce a reaction product containing elemental titanium, sodium chloride and admixed amalgam removing said reaction product from said reaction zone, sep- ,arating the sodium chloride and the amalgam from the removed reaction product and recovering elemental titanium therefrom. a

5. The method of producing elemental titanium which comprises introducing titanium tetrachloride into a supply of sodium amalgam reaction zone having an inert gaseous atmosphere and maintained at a temperature between 100 C. and the boiling point of said amalgam, agitating said amalgam in said reaction zone, maintaining the sodium level in said amalgam during the entire reaction at a-value of at least 0.35% but not over about 2.5% by weight, continuing agitation until a reaction mass contain ing elemental titanium sodium chloride and admixed amallgam results, removing said reaction mass from said reaction zone, heating said removed reaction mass to a temperature of about 600 C. to remove mercury, and removing the sodium chloride in said reaction mass at a temperature in the range from 800 to 950 C. to recover elemental titanium.

6. A continuous method for the recoyery of elemental titanium which comprises introducing titanium tetrachloride and a liquid sodium amalgam having a sodium concentration at the start in the range from 0.5 to 1.5% by weight into a reaction zone having an inert gaseous atmosphere, the proportions of said titanium tetrachloride and said amalgam at the start being such that the sodium content of the added amalgam is in excess of four molar proportions of sodium for every molar proportion of titanium tetrachloride, agitating said amalgam in said reaction zone, maintaining a temperature not in excess of the boiling point of the amalgam in said reaction zone, maintaining a sodium concentration in said amalgam of at least 0.35% but not over about 2.5% by weight, thereby producing reaction products containing elemental titanium, sodium chloride and admixed amalgam, withdrawing spent amalgam having a sodium concentration of at least 0.35% by Weight from said reaction zone, concentrating said spent amalgam to a sodium content of between 0.5 and 1.5% by weight, returning the resulting concentrated amalgam to said reaction zone, continuously removing some of said reaction products including elemental titanium, amalgam and sodium chloride from said reaction zone, separating mercury from said removed reaction products, separating sodium chloride from said removed reaction products, and recovering elemental titanium from said residual reaction products.

7. A method for the recovery of elemental titanium which comprises introducing titanium tetrachloride into and below the surface of an agitated supply of liquid sodium amalgam in a reaction zone maintained under an inert gaseous atmosphere, said amalgam initially having a sodium concentration in the range from 0.5 to 1.5% by weight, reacting said titanium tetrachloride and said sodium amalgam at a temperature in the range from C. to the boiling point of the amalgam, continuing agitating and maintaining the sodium concentration in said amalgam at avalue of at least 0.35% but not over about 2.5% by weight during said reaction until a reaction mass containing elemental titanium, sodium chloride and amalgam results, removing said reaction mass from the bulk of the sodium amalgam in said reaction zone, heating the resulting reaction mass containing elemental titanium. sodium chloride amalgam to a temperature of about 600 C. to remove mercury therefrom, heating the remaining reaction mass after the mercury removal to a temperature above the melting point of sodium chloride and separating to remove sodium chloride therefrom, and recovering elemental titanium from the reaction mass after the removal of sodium chloride.

8. 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 between about 0.5% and 2.5% by weight of said amalgam and being suflicient 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 the sodium chloride and spent amalgam from the titanium and recovering elemental titanium.

CLIFFORD A. HAMPEL. JULIAN GLASSER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,148,345 Freudenberg Feb. 21, 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 Dictionary of Applied Chemistry, by Thorpe. Pub. 1916 by Longmans, Green & Co., New York, vol. 5, pp 5 and 6.

Dictionary of Applied Chemistry, 'by Thorpe, 4th ed. Pub. 1950 by Longmans, Green 82 Co., New York, vol. 10, pp. 810 and 811.

Comprehensive Treatise on Inorganic and Theoretical Chemistry, by Mellor. Pub. 1927 by Longmans, Green & Co., New York, vol. 7, pages 7, 9, 74-77, and 81.

Claims (1)

1. 8. 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 BETWEEN ABOUT 0.5% AND 2.5% BY WEIGHT OF SAID AMALGAM AND BEING SUFFICIENT 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 THE SODIUM CHLORIDE AND SPENT AMALGAM FROM THE TITANIUM AND RECOVERING ELEMENTAL TITANIUM.

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