US3137641A

US3137641A - Electrolytic process for the production of titanium metal

Info

Publication number: US3137641A
Application number: US109443A
Authority: US
Inventors: Harvey L Slatin
Original assignee: Timax Associates
Current assignee: Timax Associates
Priority date: 1949-08-10
Filing date: 1949-08-10
Publication date: 1964-06-16
Anticipated expiration: 1981-06-16

Description

June 16, 1964 H. L. SLATIN ELECTROLYTIC PROCESS FOR THE PRODUCTION OF TITANIUM METAL Filed Aug. 10, 1949 2 Sheets-Sheet 1 (0 Ti C|4 5 HEAT /7 Ti Cl (3) Ti Clo? Ti Cl4 VAPOR 4 Ti 01 T MOLTEN HALIDE ELECTROLYSIS I3 (5) TiOl SOLUTE IN Ti MOLTEN HALIDE NC DEPOSIT GENERATED FIG. 2

Ti m HEAT VAPOR Ti Cl4 Ti Ti Cl INVENTOR. SOLUTE IN MOLTEN HALIDE BY Harvey L.Slot|n TO ELECTR OLYSIS ATTORNEY Jupe 16, 1964 Filed Aug. 10, 1949 H. L. SLATIN ELECTROLYTIC PROCESS FOR THE. PRODUCTION OF TITANIUM METAL VOLTAGE 2-2.4;

FIG. 4 T

2 Sheets-Sheet 2 /ANODE(CARBON) LIBERATING CATHODE(Ti) HEAT l5 Km? SOLUTE MOLTEN HALIDE CONTINUOUS ELECTROLYSIS J ZO HALOGEN '/-CATHODE (Ti) COLLECTING Ti METAL DEPOSIT MOLTEN {ASIDE BATH TEMP. 700 C INVENTOR.

Horvey L. Slofin ATTORNEY United States Patent 3,137,641 ELECTROLYTIC PROCESS FOR THE PRODUCTION OF TITANIUM METAL Harvey L. Slatin, New York, N.Y., assignor, by mesne assignments, to Timax Associates, New York, N.Y., a partnership of New York Filed Aug. 10, 1949, Ser. No. 109,443 9 Claims. (Cl. 20464) This invention relates to the production of titanium metal.

The principal object of the invention is to provide a process for the making of titanium metal by electrolysis.

A further object of the invention is to maintain conditions of electrolysis so as to produce the titanium metal in the form of relatively large crystalline aggregates resistant to oxidation.

Further objects of the invention, particularly the provision of special procedures which develop the titanium salt solute of the electrolytic bath in an economical and effective manner, will appear from the following specification taken in connection with the accompanying drawings in which:

FIG. 1 shows a typical flow sheet outlining the main features and steps involved;

FIGS. 2 and 3 are similar showings of modified procedures; and

FIG. 4 is a diagrammatic sectional view of an electrolytic cell illustrating a typical operation of the process of FIG. 3.

In the specific process illustrated in FIG. 1 a supply of titanium tetrachloride is indicated at 5. This is pro duced from the titanium ore by any of the known processes such, for instance, as the treatment of ilmenite with carbon and chlorine.

The tetrachloride 5 is not suited for electrolysis and must be reduced to the trichloride or dichloride, for example, by heating in contact with titanium metal, designated 6 in the drawing, as follows:

Some TiCl, remains with the TiCl in the form of vapor and liquid giving a mixture of trichloride and tetrachloride, designated 8, also containing dichloride.

Separation of the desired trichloride and dichloride from the tetrachloride is accomplished by carrying over the mixture 8 into contact with the surface of a molten mass, preferably a halide such as sodium chloride, as indicated at 9 in the drawing. On contact the tetrachloride is vaporized and passes off at 10 While the trichloride and dichloride are received and dissolved in the molten mass, this procedure being continuous and accumulating the trichloride and dichloride as a solute in the solution.

This molten solution of titanium trichloride and dichloride is then passed into a cell where it is subjected to electrolysis by potential applied across cathode 12 and anode 13, the concentration, temperature and current density being regulated to give a desired formation of the titanium deposit on the cathode 12, with chlorine liberated at the anode. The solution may be reinforced from time to time with additional trichloride and/or dichloride and the

electrodes

12, 13 may be removed and replaced, making the electrolysis continuous in its production of the titanium metal.

The chlorine may, of course, be reclaimed and used, for instance, in the production of the tetrachloride from the ore.

The preferred concentration of the trichloride and dichloride in the molten bath is of the order of 20% to 30% by weight on an equivalent trichloride basis. Con- Patented June 16, 1964 ICE centrations within the range of 12% to 43%, have been electrolyzed. Too high a concentration results in unnecessary loss of trichloride and dichloride or titanium by adherence to the cathode with the titanium. Too low a concentration will lower the efficiency and capacity of the cell. These are the controlling factors so far as concentration is concerned. The temperature range is 400 C. to above 1050 C. with best results at 700 C. to 800 C. for large crystalline aggregates of good bright metal. At low temperatures the tendency is toward titanium deposits in granulated or powdery form.

The cathode current density is from a fraction of an ampere per square inch to about 20 amperes. The most effective range for larger metal particles is 0.1 to 0.5 ampere per square inch. At lower and higher densities the particle size of the deposit decreases, the larger crystals being characteristic of the intermediate current densities. The voltage across the cell terminals is normally 2.0 to 2.4 volts, whichis above the decomposition potential of the titanium compounds, and may range from 1.5 volts minimum up to 5 volts depending, for instance, on temperature and other factors.

Good results with large crystals and favorable weight distributions with most of the metal in large masses have been obtained at 2.4 volts, 1.5 amperes (equivalent to 0.3 ampere per square inch at the cathode), 28% TiCl equivalent and at 850 C. to 710 C. The chlorine is desirably separated from the cell rapidly by appropriate bafiling.

The cathode material 12 can be any conducting metal which remains solid at the temperature of the bath during electrolysis. Titanium is preferred and copper, nickel, iron, stainless steel, and tungsten have been used. The anode 13 is preferably of graphite or electrocarbon.

Carbon and graphite have been used, titanium may be used when desirable to maintain a constant concentration of the solute titanium salt and at low temperatures and current densities tungsten may be used.

When the trichloride and dichloride are dissolved in the bath they do not decompose even though the temperature of the bath is above their disproportionation temperatures because as solute they are stabilized.

The titanium trichloride or dichloride may be dissolved in the molten halide of any metal more electropositive than titanium. Potassium chloride has been used as have mixtures such as (a) lithium and potassium chlorides and (b) sodium-lithium-potassium chlorides and (c) sodiumpotassium chlorides and (d) sodiumpotassium-barium chlorides, and (e) sodium-calcium chlorides and (,f)

sodium-potassium-calcium chlorides.

The procedures outlined in the flow sheet of FIG. 1 leading to the final electrolytic bath may be simplified and improved by effecting the reduction of the titanium tetrachloride by the titanium metal in a. molten halide bath, thus combining steps designated 2, 3 and 4 as diagrammed in FIG. 2. The reduction of the tetrachloride and the solution of the trichloride and dichloride in the molten halide is then attained in a single step. This is accomplished by vaporizing the tetrachloride, as shown at 15 in FIG. 2, and by bringing the tetrachloride vapors into contact with the molten mass of the halide 16 containing titanium metal 17 which acts as a reducing agent. The tetrachloride fed to the body of the molten halide is reduced by the titanium metal and the supply is controlled to avoid excess of tetrachloride and give the desired concentration in the molten halide bath. This may be the concentration desired for electrolysis or further blending or additions to bring it into condition for electrolysis may be required.

A further simplification of the operations is diagrammed in FIG. 3 which combines the reduction and electrolysis in a single reaction vessel 20 as illustrated in outline in FIG. 4. The titanium tetrachloride (preferably in liquid form) is continuously fed to the bottom of the molten electrolyte 21, where it vaporizes, through flow tube 22 and onto the titanium metal pieces 17 at such rate as to maintain a constant trichloride equivalent concentration in the bath. The container may be of iron, the inner surface being coated with solid salt Within which the molten electrolyte is kept fluid by the heat of the electrolysis.

The tetrachloride vapor impinges on the metal maintained at the temperature of electrolysis of about 700 C. as above indicated. The gas aids in stirring the fused salt 21 and in the distribution of the trichloride and dichloride. The 13.0. potential across the anode 23 and cathode 24 deposits metallic titanium at the cathode, the voltage being maintained at about 2.4 volts. The cathode 24 may be periodically removed for recovering of the adhered titanium crystals, and replaced for subsequent deposition.

The temperature of reduction of the tetrachloride by the titanium metal may be in the neighborhood of 400 C. to 500 C. and other reducing agents may be used for this reduction step, namely hydrogen, zinc, cadmium, iron, nickel, aluminum, magnesium, or titanium carbide.

The process is readily controlled to provide a deposit of titanium metal in desired form and the procedures are efficient and may be economically combined in a compact, simple manner. It is possible to use other halides of titanium as the solute in the molten bath but the chlorides are preferred and other halides of metals more electropositive than titanium may be used in molten form as the solvent. The operations substantially exclude water from the bath and the complications resulting from its presence.

I claim:

1. The process of producing titanium metal in solid form comprising, dissolving a material of the group consisting of titanium dichloride and titanium trichloride as a solute in a solvent molten bath composed of materials of the group consisting of alkali-metal chlorides and alkaline-earth chlorides and mixtures thereof, and electrolyzing said bath containing said solute in a cell containing a solid cathode, thereby depositing titanium metal in crystalline aggregates on said cathode.

2. The process of claim 1 wherein said cathode is titanium metal.

3. The process of producing titanium metal in solid form comprising, dissolving a material of the group consisting of titanium dichloride and titanium trichloride as asolute in a solvent molten bath composed of materials of the group consisting of alkali metal chlorides and alkaline-earth chlorides and mixtures thereof free of water, electrolyzing said bath containing said solute in a cell containing a solid cathode, thereby depositing titanium metal in crystalline aggregates on said cathode, and providing a separate molten supply of said bath components containing said solute and continuously passing it into said cell thus maintaining the continuity of the depositing of said titanium metal.

4. The process of producing titanium metal in solid form comprising, producing a solute material of the group consisting of titanium dichloride and titanium trichloride in a solvent molten bath composed of materials of the group consisting of alkali metal chlorides and alkalineearth chlorides and mixtures thereof which contains titanium metal by introducing titanium tetrachloride into said bath into contact with said metal, and electrolyzing said bath containing said solute in a cell containing a solid cathode, thereby depositing titanium metal in crystalline aggregates 011 said cathode.

5. The process of producing titanium metal in solid form comprising, producing a solute material of the group consisting of titanium dichloride and titanium trichloride in a solvent molten bath composed of materials of the group consisting of alkali metal chlorides and alkalineearth chlorides and mixtures thereof, and continuously supplying said solute-containing bath to a molten electrolyte containing an anode and a solid cathode, and electrolyzing said solute in said bath between said electrodes thereby depositing titanium metal in crystalline aggregates on said cathode.

6. The process of producing titanium metal in solid form comprising, dissolving a material of the group consisting of titanium dichloride and titanium trichloride as a solute in a solvent molten bath composed substantially of sodium chloride and electrolyzing said bath containing 1 said solute in a cell containing a' solid cathode, thereby depositing titanium metal in crystalline aggregates on said cathode.

7. The process of producing titanium metal in solid form comprising, dissolving a material of the group consisting of titanium dichloride and titanium trichloride as a solute in a solvent molten bath composed of materials of the group consisting of alkali metal chlorides and alkaline-earth chlorides and mixtures thereof, and electrolyzing said bath containing said solute in a cell containing a titanium metal anode and a solid cathode, thereby depositing titanium metal in crystalline aggregates on said solid cathode.

- 8. The process of producing titanium metal in solid form comprising dissolving a material of the group consisting of titanium dichloride and titanium trichloride as a solute in a solvent molten bath composed of materials of the group consisting of alkali metal chlorides and alkaline earth chlorides and mixtures thereof, and electrolyzing said bath containing said solute in a cell having a titanium metal anode and a solid cathode to maintain a concentration of titanium dichloride and trichloride in said electrolyte, thereby depositing titanium metal in crystalline aggregates on said solid cathode.

9. The process of producing titanium metal in solid form comprising providing a material of the group consisting of titanium dichloride and titanium trichloride as a solute in a solvent molten bath composed of materials of the group consisting of alkali metal chlorides and alkaline earth chlorides and mixtures thereof, and electrolyzing said bath containing said solute in a cell having a solid cathode and an anode containing titanium to maintain a concentration of titanium dichloride and trichloride in said electrolyte, thereby depositing titanium metal in crystalline aggregates on said solid cathode.

References Cited in the file of this patent UNITED STATES PATENTS 1,408,141 Seward Feb. 28, 1922 FOREIGN PATENTS 263,301 Germany Aug. 5, 1913 615,951 Germany July 16, 1935 OTHER REFERENCES Annales de Chimie, 9th series, volume 16 (1921),

r page 18 of paper by Billy.

Mellors Comprehensive Treatise on Inorganic and Theoretical Chemistry, volume 7 (1927), page 11.