US2770541A

US2770541A - Method of producing titanium

Info

Publication number: US2770541A
Application number: US304388A
Authority: US
Inventors: Richard H Singleton
Original assignee: Nat Res Corp
Current assignee: National Research Corp
Priority date: 1952-08-14
Filing date: 1952-08-14
Publication date: 1956-11-13
Anticipated expiration: 1973-11-13

Description

United rates METHOD OF PRODUCING TITANIUM Application August 14, 1952, Serial No. 304,388

9 Claims. (Cl. 7584.5)

This invention relates to the production of titanium metal or lower chlorides of titanium, and more particularly to the production of pure titanium metal or pure titanium trichloride from impure titanium alloys.

It is a principal object of the present invention to provide an improved process for manufacturing titanium from alloys of titanium so as to obtain the titanium in a form essentially uncontaminated by the original alloying metal.

Another object of the invention is to provide a cheap source of relatively pure titanium trichloride.

Still another object of the invention is to provide a process which is particularly adapted to the production of cheap titanium trichloride for conversion to titanium metal or titanium tetrachloride.

Another object of the invention is to provide a process for the manufacture of titanium metal which obviates the necessity of manufacturing titanium tetrachloride by chlorination of titanium ores.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the process involving the several steps and the relation and the order of one or more such steps with respect to each of the others which are exemplified in the following detailed disclosure, and the scope of the application of which Will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description, taken in connection with the accompanying drawings, wherein:

Fig. l is a schematic diagrammatic flow sheet illustrating one embodiment of the invention, particularly directed to the use of aluminum trichloride; and

. Fig. 2 is a schematic diagrammatic flow sheet illustrating one embodiment of the invention, particularly directed to the use of zinc chloride.

The present invention is primarily directed to the production of titanium or lower chlorides of titanium from titanium alloys. In particular, the present invention is concerned with the use of copper-titanium alloys as a starting material, although other titanium alloys, such as the alloys of titanium with nickel, can be employed. From the standpoint (of cheapness and ease of operability of the process, the copper-titanium alloys are much preferred. Alloys of titanium can be relatively cheaply manufactured by reducing titanium oxides with carbon in the presence of an alloying metal, for example copper. While such an alloy is not particularly useful by itself, it can furnish a source of titanium which is relatively free of oxygen. In the present invention this crude titanium alloy will be considered, for simplicity of description, as a titanium-copper alloy. This alloy may be made by the arc furnace reduction of ilmenite or the like with carbon in the presence of copper or copper oxide. Equally it can be made by dissolving impure titanium in molten copper.

The titanium-copper alloy if fed from an arc furnace 8 atent icg- (Figs. 1 and 2) to a first high temperature reactor 10 which is arranged to hold the molten titanium-copper alloy at a temperature above about 1000 C. so as to provide a large surface area for contact with a chloride of a third metal. This third metal chloride is preferably selected from the class consisting of zinc chloride (ZnClz) and aluminum trichloride (AlCla). This third metal chloride vapor may be generated in any suitable manner and fed to the high temperature reactor 10 so as to provide adequate contact with the titanium content of the titanium-copper molten alloy. At high temperatures on the order of 1000 C. and above, the copper in the titanium alloy is relatively inert to aluminum trichloride or zinc chloride, while the titanium will react with these chlorides to form gaseous titanium chlorides and gaseous lower valence derivatives of the aluminum trichloride or Zinc chloride. The copper which remains after removal of its titanium content is recycled to the arc furnace 8 for the preparation of more titanium-copper alloy. In the case of aluminum trichloride (illustrated in Fig. l), the principal (and idealized) titanium reaction is expressed by the following equation:

3A1Clao) o 2TiClm) B o) In the case of zinc chloride (Fig. 2) the principal (and idealized) reaction is expressed by the equation:

The reaction products from Equation A or B are preferably removed from the high temperature reactor as gases, and are preferably shock-cooled (at 12) to a temperature below about 500 C. This shock-cooling is preferably achieved by the use of a relatively inert gas such as argon or hydrogen. The shock-cooled products are then reacted in a low temperature reactor 14 with titanium tetrachloride to convert these products to titanium trichloride and the third metal chloride which was originally supplied to the high temperature reactor. As a result of the shock cooling and the reaction with the titanium tetrachloride, essentially all of the titanium is in the form of titanium trichloride, and all of the third metal (i. e., zinc or aluminum) is in the form of either zinc chloride or aluminum trichloride.

A number of reactions take place during the process of shock-cooling and reaction with the titanium tetrachloride. For simplicity these will be considered separately for the metals zinc and aluminum. In the case of aluminum the aluminum monochloride leaving the high temperature reactor 10 disproportionates during shock cooling to aluminum metal and aluminum trichloride gas in accordance with the following equation:

100 C. AlClam +2 l t or (1) Since the high temperature reactor 10 or the shockcooling may produce some titanium dichloride (due to disproportionation of titanium trichloride or vapor phase reduction thereof by aluminum monochloride) there is usually some titanium dichloride mixed-in with the shocl cooled product. This titanium dichloride is converted (in the. low temperature reactor 14) to .titaniumtrichloa ride by reaction with the tetrachloride in accordance with a the following equation:

2TiCls(.)

nium trichloride in accordance with the following equation:

C. Tim 3TiCI4 4T1Clao) (F) The above reactions are quite exothermic and will'raise the temperature of the shock-cooled products in low temperature reactor 14 to a point where sublimation of the titanium trichloride begins to occur, this sublimation serving as a top limit for the temperature in reactor 14. The reactions expressed by Equations D, E and F will take place very rapidly, even at low temperatures, and achieve essentially complete removal of the aluminum chloride from the reaction products prior to any appreciable amount of sublimation of the titanium trichloride. This aluminum trichloride may be condensed in a condenser 17 therefor.

Since there may be some oxides, carbides or nitrides of titanium, or even some oxides of aluminum in the lowtemperature reaction product in reactor 14, it is preferred to resublime the contained titanium trichloride so as to obtain this titanium trichloride in a'state of high purity. This resublimation may be readily accomplished by heating the reaction products in the second reactor 14 'under an atmosphere of titanium tetrachloride. to a temperature on the order of about 600 C. to 800 C. Although this temperature is well above the disproportionation. temperature for titanium trichloride, the titanium trichloride will not disproportionate, due to the atmosphere of titanium tetrachloride, and may be transported to a suitable condenser 16 for condensing the titanium trichloride as a solid. Any

aluminum trichloride which has condensed along with the titanium trichloride may be separated therefrom in a relatively simple step (not shown) by dissolving this aluminum trichloride in boiling titanium tetrachloride. The aluminum trichloride can be readily separated from the titanium tetrachloride by cooling the titanium. tetrachloride and thereby crystallizing the aluminum trichloride. The crystallized aluminum trichloride can be easily filtered from the liquid titanium tetrachloride.

While the low temperature reaction has been shown as a single step, for simplicity of illustration, it is preferably operated as a two-stage reaction. The first stage is the conversion of all of the shock-cooled products to titanium trichloride and the other metal chloride (e. g. aluminum trichloride) peratures on the order of 200 C. to 300 C. The second stage is primarily a purification step and takes place at a somewhat higher temperature (e. g. 600 C.-800 C.) and involves the sublimation of titanium trichloride. Obviously these two stages can be combined in one or can be carried out in separate pieces of equipment at separate times.

The reaction of zinc chloride with the titanium-copper alloy, as presented in Equation B above is shown in Fig.

2. In this case the gaseous products leaving the high.

temperature reactor are primarily titanium trichloride gas and zinc gas. However, there may also be some titanium dichloride as well as some titanium tetrachloride. These vapors are also preferably shock cooled at 12 (by use of a cooling gas such as argon or hydrogen) to a temperature below the melting point of Zinc so as to obtain titanium trichloride solid, titanium dichloride solid and zinc solid. These shock-cooled products are also preferably treated with titanium tetrachloride vapors This first stage can be operated at tem-' in low-temperature reactor 14 in a manner similar to that discussed above in connection with the treatment of the shock-cooled products from the aluminum trichloride high-temperature reactor. The zinc metal will react with titanium tetrachloride to form lower chlorides of titanium and zinc chloride in accordance with the following equations:

2 'liChm TiO1z(;)+ nClz(qor-) The titanium metal and the titanium dichloridein, the low temperature reactor 14 are converted to titanium trichloride by reaction with titanium tetrachloride in accordance with Equations E and F above. The final products in the second reaction zone are thus primarily in the form of either titanium trichloride or zinc chloride. The titanium trichloride is preferably sublimed from the reaction mass (since this mass may contain contaminants such as titanium oxides, carbides, or nitrides) by heating to about 600-800 C. in an atmosphere of titanium tetrachloride. The resulting titanium trichloride vapors are condensed in a separate condenser 16. Since the zinc chloride will also sublime at the sublimation temperature of the titanium trichloride, the zinc chloride will also condense with the'titanium trichloride; However, the zinc chloride can be removed from the titanium. trichloride by dissolving in an organic solvent such as other. This separation is achieved in separator 18, which may comprise a heating chamber for distilling ether from the titanium trichloride and a second heating chamber for recovering ether from the zinc dichloride solutionp Both of the above processes result in high yields of essentially pure titanium trichloride. This titanium trichloride may be converted to titanium metal by a number of techniques, such as in a disproportionation apparatus 20 of the type described and claimed more fullyin the copending application of Singleton and van Arkel, Serial No. 285,975, filed May 3, 1952. The disproportionation reaction is particularly useful since it provides relatively large quantities of titanium tetrachloride which may be recycled to the low temperature reactor 14 for reaction with'titanium dichloride, titanium metal and aluminum or zinc (as the case may be) so as to obtain high yields of the titanium trichloride in the second reactor 14. 'Equally, the titanium trichloride may be thermally reduced to titanium metal by the use of reducing agents, or may be fed to an electrolysis cell, as disclosed more fully in the copending application of Benner and Chadsey, Serial No. 233,204, filed June 23, 1951. Additionally, the titanium trichloridemay be chlorinated to titanium tetrachloride for use in thermal reduction processes such as those shown in the Kroll Patent No. 2,205,854, Maddex Patent No. 2,556,763, or in'the torch process described and claimed more fully by Findlay in patentapplication 200,606, filed December 13, 1950.. i

In the preferred form of apparatus employed with the or carbon. When carbon or graphite is'used, the'neces sary heat input can be readily achieved by using the carbon or graphite as an electrical heating element in either an induction or resistance heating circuit; Where mechanical movement is required in the high-temperature portions, it is preferred to' employ refractory metals, such as .molybdenum, for those parts requiring high-temperature mechanical strength or wear-resistance. Those portions of the apparatus which operate at temperatures of about 600 C. or lower can be formed of stainless steel, nickel or refractory metals, such as molybdenum and the like. Carbon and graphitecan equally be used in the relatively low-temperature portions of the apparatus, but, for mechanical reasons, may be less preferred than the metals in many cases. i i

In general, the high temperature reactor may be a countercurrent still, such as a zinc still or a rotary kiln, these arrangements furnishing a large surface area for the titanium-copper alloy to be reacted with the third metal halide. The shock cooling may take place in a portion of the high temperature reactor, in which case the shockcooledproducts may be removed therefrom as solids. Equally, the shock-cooling may take place outside of the high temperature reactor, the shock cooling in this case being preferably a portion of the low temperature reactor 14.

' The percentage of titanium in the titanium-copper alloy-is ,preferably in the range of 40% titanium to 60% titanium, the percent titanium being reduced to about 5% before the copper is recycled to the electric furnace for addition of -mo re titanium.

In connection with the above discussion of the present invention, little emphasis has been placed on the shockcooling requirements. It should be pointed out that the shock-cooling gases must be free of oxygen, nitrogen and compounds thereof such as water vapor, carbon monoxide and the like. This is due to the extreme reactivity of titanium and its chlorides with oxygen and the like. The great mass of cold hydrogen or argon required to shock-cool the hot reaction products necessitates high purity for these gases and, as a consequence, these gases are preferably used on a recycle basis with any necessary purification apparatus in the recycle system.

While resublimation of the product titanium trichloride in the temperature reactor 14 has been set forth as a highly desirable step in the process it is not essential in all cases. This is particularly true where this titanium trichloride is essentially pureor sufiiciently pure for its subsequent use. This purity will naturally depend upon the purity of the starting materials and the degree of carry-over of contaminants from the high temperature reactor to the shock cooling zone. The purity requirements of the titanium trichloride will vary considerably with the details of the further processing steps. For example, if disproportionation is to be employed, the titanium trichloride must have a very high purity. If the subsequent step is chlorination to titanium tetrachloride the titanium trichloride need not be particularly pure, provided the contaminants can be separated from titanium tetrachloride. With regard to electrolysis the purity requirements Will be largely dependent upon the solubility of the inpurities in the molten electrolyte.

Since certain changes may be made in the above process without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. The process of manufacturing titanium trichloride which comprises heating a copper-titanium alloy in a first reaction zone to a temperature above 1000 C. in the presence of a vapor of a third metal chloride selected from the class consisting of zinc chloride and aluminum trichloride to convert said titanium to a gaseous lower chloride of titanium and to convert the metallic portion of said third metal chloride to a gaseous lower valence state, passing the gaseous products from the first reaction zone to a second reaction zone, reacting said products with titanium tetrachloride at a lower temperature in said second zone to form titanium trichloride and said third metal chloride, and separating titanium trichloride from the reaction mass and by-products.

2. The process of manufacturing titanium which comprises forming a crude alloy of titanium and copper, heating said alloy in a first reaction zone to a temperature above about 1000 C. and contacting said hot alloy with a vapor of a third metal chloride from the class consisting of zinc chloride and aluminum trichloride to convert said titanium to a gaseous chloride and to convert the metallic portion of said third metal chloride to a gaseous lower valence state, passing the' gaseous products from the first reaction zone to a second reaction zone maintained at a lower temperature, reacting the products from said first zone with titanium tetrachloride in said second zone to form titanium trichloride and said chloride of said third metal, separating said titanium trichloride from the reaction mass and by-products, disproportionating said titanium trichloride to titanium metal and titanium tetrachloride, and recycling said titanium tetrachloride to said second zone to increase the production of titanium trichloride therein.

3. The process of manufacturing titanium trichloride which comprises forming a crude alloy of titanium and a second metalselectedfrom the classconsisting of copper and nickel, heating said alloyin a first reaction zone to a temperature above about 1000 C. and contacting said hot-allow with a vapor of aluminumtrichloride to form titanium chlorides and aluminum chlorides in the vapor phase, passing said chlorides into a second zone at a temperature below about 1000 C. where the vapor phase products from the first reaction zone and products resulting from disproportionation of said vapor phase products are reacted together in the presence of titanium tetrachloride to produce titanium trichloride and aluminum trichloride, and separating said titanium trichloride and said aluminum trichloride.

4. The process of manufacturing titanium trichloride which comprises forming a crude alloy of titanium and a second metal selected from the class consisting of copper and nickel, heating said alloy in a first reaction zone to a temperature above about 1000 C. and contacting said hot alloy with a vapor of zinc chloride to form titanium chlorides and zinc in the vapor phase, shock cooling said vapor phase products, reacting said shock-cooled products with titanium tetrachloride to produce titanium trichloride and zinc chloride, and separating said titanium trichloride and said zinc chloride.

5. The process of manufacturing titanium which comprises forming a crude alloy of titanium and copper, heating said alloy in a reaction zone to a temperature above about 1000 C., contacting said hot alloy with a vapor of a third metal chloride selected from the class consisting of zinc chloride and aluminum trichloride to convert said titanium to a gaseous lower chloride of titanium and to convert the metallic portion of said metal chloride to a gaseous lower valence state, passing the gaseous products from the first reaction zone, shock cooling the gaseous products leaving said reaction zone to a temperature below about 500 C., reacting the shock cooled products with titanium tetrachloride to convert said products to titanium trichloride and said third metal chloride, subliming titanium trichloride in an atmosphere of titanium tetrachloride, condensing said sublimed titanium trichloride, and converting said titanium trichloride to titanium metal.

6. The process of manufacturing essentially pure titanium trichloride which comprises forming a crude alloy of titanium and copper, heating said alloy in a reaction zone to a temperature above about 1000 C., contacting said hot alloy with a vapor of a third metal chloride selected from the class consisting of zinc chloride and aluminum trichloride to convert the metallic portion of said titanium to a gaseous lower chloride of titanium and to convert said metal chloride to a gaseous lower valence state, removing the gaseous products from the first reaction zone, shock cooling the gaseous products to a temperature below the melting point of said third metal to condense said third metal in a finely powdered, highly reactive condition, reacting the shock cooled products with an atmosphere of titanium tetrachloride to convert said products to titanium trichloride and said third metal chloride, subliming said titanium trichloride under an atmosphere of titanium tetrachloride, and condensing said sublimed titanium trichloride.

7. The process of claim 6 wherein said third metal chloride is aluminum trichloride and the titanium trichloride is condensed at a temperature above the condensation temperature'of the aluminum trichloride.

8. The process of claim 6 wherein said third metal chloride is zinc chloride which is condensed with the titanium trichloride, and the zinc chloride is extracted from the mixture by dissolving in an organic solvent.

9. The process of claim 6 wherein said third metal chloride is aluminum trichloride which is condensed With the titanium trichloride, and the aluminum trichloride is extracted from the mixture by dissolving in titanium tetrachloride.

References Cited in the file of this patent UNITED STATES PATENTS 1,173,012 Meyer et al. Feb. 22, 1916 3 2,306,184 Pechukas Dec. 22,1942 2,452,665 Kroll et a1. t. Nov. 2, 1948 2,519,385 Loonam Aug. 22, 1950 2,607,675 Gross ....iAug. 19, 1952 2,618,549 Glasser et a1. Nov. 18, 1952 2,647,826 Jordan Aug. 4, 1953 2,670,270

Jordan r Feb. 23, 1954 OTHER REFERENCES Comprehensive Treatise on Inorganic and Theoretical Chemistry, by Mellor, vol. 7, pub. 1927 by Longmans, Green and Co., New York. Pages 74-79; V

Report of Investigations 4519, pub. Aug.. 1949 by Bureau of Mines, Washington, D. C. Entire report 37 15 pages and 2 figures, pages 9-13 relied upon.

Titanium, by Barksdale, page 81. Pub. 1949 by The Ronald Press Co., New York.

Claims

2. THE PROCESS OF MANUFACTURING TITANIUM WHICH COMPRISES FORMING A CRUDE ALLOY OF TITANIUM AND COPPER, HEATING SAID ALLOY IN A FIRST REACTION ZONE TO A TEMPERATURE ABOVE ABOUT 1000* C. AND CONTACTING SAID HOT ALLOY WITH A VAPOR OF A THIRD METAL CHLORIDE FROM THE CLASS CONSISTING OF ZINC CHLORIDE AND ALUMINUM TRICHLORIDE TO CONVERT SAID TITANIUM TO A GASEOUS CHLORIDE AND TO CONVERT THE METALLIC PORTION OF SAID THIRD METAL CHLORIDE TO A GASEOUS LOWER VALENCE STATE, PASSING THE GASEOUS PRODUCTS FROM THE FIRST REACTION ZONE TO A SECOND REACTION ZONE MAINTAINED AT A LOWER TEMPERATURE, REACTING THE PRODUCT FROM SAID FIRST ZONE WITH TITANIUM TETRACHLORIDE IN SAID SECOND ZONE TO FORM TITANIUM TRICHLORIDE AND SAID CHLORIDE OF SAID THIRD METAL, SEPARATING SAID TITANIUM TRICHLORIDE FROM THE REACTION MASS AND BY-PRODUCTS, DISPROPORTIONATING SAID TITANIUM TRICHLORIDE TO TITANIUM METAL AND TITANIUM TETRACHLORIDE, AND RECYCLING SAID TITANIUM TETRACHLORIDE TO SAID SECOND ZONE TO INCREASE THE PRODUCTION OF TITANIUM TRICHLORIDE THEREIN.