US2785973A - Production and purification of titanium - Google Patents

Description

PRODUCTION AND PURIFICATION OF TITANIUM Philipp Gross, Eton, and David Leon 'Levi,Chalfont St; 1 Peter, England, assignors to Fulmer Research Institute Limited, Stoke Poges, England No Drawing. Application August 19, 1952,

' Serial No. 305,292

Claims priority, application Great Britain I September 5, 1951 5 Claims. (Cl. 75-844 metallic consitutents, for example, iron and silicon, is, formed, also having properties so much inferior to those of substantially pure titanium that its usefulness in metallurgical practice is very restricted.

'.Stahler and Bachran (Ber. deutsche chem. Ges.. 44

(191 1 2907 formed metallic titanium by the thermal decomposition of titanium dichloride, vtitanium tetrachloride vapour being formed simultaneously; while the corresponding reaction with titanium dibromide was observed by Young andSchumb (J. Amer. Chem. Soc., 52 (1930-), 4233), These dihalides were themselves formed by thermal decomposition at somewhat lower temperatures of the solid 'trichloride and tribromide respectively, likewise with the simultaneous formation of. titanium tetrachloride and tetrabromide respectively. Klemm and Grimm (Zeits. anorg. chem. 249 1942), 198) converted metallic titanium to a mixture of condensed lower tita-- nium chlorides by reaction in a sealed tube with titanium tetrachloride, and Young and Schumb (J. Amer.

Chem. Soc. 52 (1930), 4233) carried out asimilar re action with titanium and titanium tetrabromide. Meyer, Bauer and Schmidt (Ber. deutsche chem. Ges. ,56B (l923), 19 08) in reducing titanium tetrachloride vapour with hydrogen so as. to condense titanium trichloride,

foundthat when titanium was placed in the gas stream to absorb excess hydrogen chloride, an increased yield was obtained, and that the condensate contained'aproportion of titanium dichloride.

We have found that the normally stable lower chlorides orbromides, especially the dihalides, of titanium can be obtained in a convenient way and with a very high yield by the reaction of the corresponding tetrahalide vapour with heated titanium bearing material, preferably under'reduced pressure, whereby the vapoursof these lower halides areformed and can be condensed as solids in a cooler zone, When using the unsaturated tetrahalide vapour the lower halides are condensed entirely free from halide, pure titanium is bearing material and the originally applied tetrahalide is produced from the titanium recovered.

We have also found that the metallic titanium formed by this procedure, consisting of small discrete leaflets (flakes) can on account of its form very readily be submitted to further metallurgical processing, for example to pressing and 'sintering, and on this account has considerable advantages over other metallic titanium products, for example .the sponge which is formed by the reduction of titanium tetrachloride with magnesium.

According to the present invention, therefore, pure metallic titanium can be extracted from titanium hearing material of the group consisting of impure titanium and titanium alloys (especially impure titanium ortitanium alloys, such as ferrotitanium, made by reduction of a raw material with carbon) by passing over them titanium.

tetrachloride or titanium tetrabromide vapour at elevated temperatures and in an inert atmosphere, i. e. an atmosphere containing titanium halides either alone and if so under reduced pressure or mixed with an inert carrier gas, such as argon, whereby these halides react with the titanium-bearing material to give the vapour of the normally stable titanium diand/ or tri-chloride or bromide respectively, leading these vapours from the reaction zone into a separate and adjacent zone where they are L cooled, whereby the lower halides mainly condense as solids, and also to a small extent disproportionate into metallic titanium which condenses and titanium tetrachloride or tetrabromide vapours respectively which vapours are led into a separate and cooler condenser (tetrahalide condenser). In a subsequentstep the solid condensed diand/or trichlorides or bromides are heated preferably in vacuo but otherwiseunder a partial pressure of titanium tetrachloride or tetrabromide respectively lower.

than their decomposition pressures into these tetrahalides at the prevailing temperature, whereby they decompose,

yielding metallic titanium and titanium tetrachloride or tetrabromide vapour respectively; If the decomposition is carried out using hydrogen as carrier gas, the metallic titanium may afterwards require heating in vacuum to 'remove' absorbed hydrogen. The titanium tetrahalide formed is also led into a separate condenser preferably the tetrahalide condenser referred to above,,so that the whole of the titanium tetrachloride or tetrabromide originally used may be re-applied for further extraction; alternatively, since the vapour pressures of the titanium tetrachloride or tetrabromide are high at moderately. elevated temperatures, they may be recirculated in the gaseous state without previous condensation. Again, since the diand tri-chlorides (or bromides) are highly hygroscopic solids it is usually advantageous, but not necessary, to

unreacted'tetrahalide, if any, which unreacted halide therefore suitable for further use. We have further found I that'the impurities usually contained in'im'pure titanium such as' carbon '(usually as carbide), oxygen and also small amounts of other metals such as iron, donot react with the tetrahalide: vapour under these conditions 'so that-the" lower halides obtained hen using impu'retitaoifoth'ertitaniumbearin'g materials are'sub's'tantially Thus by disproportioning near-rem such impurities. v these lower halides into, metallic titanium and the tetrause one converter for both condensing and decomposing the lower halides by carrying out the process in the same chamber (converter) but in two consecutive steps, in the first of which titanium tetrachloride or tetrabromide is led over the titanium bearing material and metallic titanium and lower titanium halides condensed in the converter by cooling, and in the second of which the converter is heated while the stream of gaseous reaction products is diverted from it, and the solid lower titanium 'chlorides (or bromides) thus decomposed. By having at least two converters which are alternately heated and cooled and correspondingly connected with and disconnected from the stream of tetrachloride or tetrabromide, a, continuous extraction can be achieved using either continuous circulationlof the tetrahalide without condensation, or-alternativelycondensihg the tetrahalide 'and'using at least two tetrahalide condensers serving alternately as condensers and evaporators.

The 'method'may beillustrated by considering typical Patented Mar. 19, l9 ;57

3 reactionsoccurring in the extraction of titanium by means of titanium tetrachloride according to the method -of the invention. In the primary reaction we have in general Z-TiClz (sol:id) Ti (solid, pure) +TiCl4 (vapour) The process for the production of titanium from titanium" bearing material of the group consisting of impure titanium and titanium alloys according to the invention, thus comprises the following'steps, all carried'out in an inert atmosphere; heating the titanium bearing. material, evaporating a titanium tetrahalide of the group consistin'g'of chloride and bromide, leading the vapour of said tetrahalide in an unsaturated state over the heated material, thereby to form a vapour mixture containing said tetrahalide and lower normally stable titanium halides, leading said vapour mixture to a cooler zone whereby the lower halides condense as solids except for a small amount which decomposes into tetrahalide vapour and purified titanium which condenses with the lower halides, reducin'gthe tetrahalide pressure in said cooler zone to-a value lower than the decomposition pressure of the lower halides while heating the condensate therein to a temperature below the temperature at which under applied pressure the halides will dissociate into metallic titanium and free halogen, thereby to decompose the condensed lower halides into purified metallic titanium and. tetrahalidevapour, and re-using the tetrahalide from the condensation and decomposition steps for further extraction of titaniunrfrom the titanium bearing material.

In the primary reaction the extentof conversion of V employed, as will also the relative proportions of the different lower halides formed. Similarly, according tothe reaction conditions the relative proportions-of the lower halides'in the solid condensateto one anotherwill vary, in some cases one halide predominating, asfor example. the dichloride under theconditions describedin theex'amples below. Both reactionsare endothermic, so thatthe conversion into the lower halides'will be -higher at higher temperatures. The conversion is also-dependcut on the pressure the dihalide formation beingzrelative'lysomewhat favoured by decreasingpressure. (See spec.)

In carrying out the process according tothe invention, in order to ensure that the condensed solid-lower titanium halides are pure and are not contaminated with small quantities of oxide or carbide or other'impuritiessuch as silicon or aluminum, it is of importance that these lower halides are condensed on a surface composed of materials which do not react. with the lower halides to produce substances which bring about such contami nation. The use of titanium and. also of. molybdenum,- for example, has been found advantageous for this purpose. A suitable lining of titanium may also be" formed on the surface of another refractory n'iat'erial; for example mullite or similan oxygen-containing materialsgdue to reaction between. the lower titaniumhalides and the origi' nal. surface of the refractory leading. tothe formation of] a protective surface layer: on which =the lower-titanium halides may be condensed without" contamination. Graphite (or a refractory carbide) likewise provid'es a suitable condenser material, protective coatings (of titanium carbide) being formed in'this' case also.

A suitable combination of temperature and pressure when using titanium tetrachloride according to the method of the invention maybe seen from the following example. A stream of argon was saturated with titanium tetrachloride vapour at 20 C. (thusc'ontaining titanium tetrachloride at a partial pressure of about 1-0 mm.) and was passed over pieces of impure titanium (3 to 6 mesh), containing carbon as main impurity, maintained at about 1050 C. and contained in a graphite tube lined with a material, su'chas molybdenum, showing no reaction with the gaseous products under these reaction conditions. The reaction products passed into a cooler zone of the tube where a condensate formed consisting mainly of titanium dichloride in yield corresponding to about 40% of complete conversion of tetrachloride, but containing also much smaller amounts of metallic titanium and titanium trichloride. The stream of argon containing titatetrachloride' vapour was discontinued, a stream of pure argon passed and the temperature of the condensate raised toabout' 950 C. Titanium tetrachloride vapour was evolved and collected in a suitable condenser, but after some time the argon stream leaving the reaction tube no longer contained titanium tetrachloride vapour, and metallic titanium, free from carbon, remained in the condenser;

In a similar experiment in" which the partial pressure of titanium tetrachloride was 180 mms., and the impuretitanium was'maintained at 1050 C., the reaction products condensing" again consisted mainly of titanium dichloride (in a yield corresponding to about 35% of complete conversion of the'tet'rachloride), together with much smaller amounts of titanium trichloride and metallic titanium. The lower chlorides were converted to metallic titanium by'heating' to 950 C. in the manner described above;

IH'SimilaT experiments with titanium tetrabromide in which partial pressures of about 5 mms. and mms. were used, and the impure titanium was maintained around 1000"C., the reaction products in the condenser consisted mainly of titanium dibromide which was ob tained ingood yield, together with minor amounts of that-- niumtribromide and'metallic titanium. The reaction products were heated in a stream of pure argonat around 800 C., and" the'tit'anium tetrabromide evolved was collected' in a suitable condenser. When decomposition of the lower halides was'c'omplete, metallic titanium free fromcarbon' remained in the condenser.

I We claim:

1. A process for extracting titanium from titanium bearing'material of the group consisting of impure titaniunr'a'nd" titanium alloys which comprises the following. st'eps,-all"carried out in an inert atmosphere;.heating, the titanium bearing "material, evaporating a titanium tetra halide of the group consisting of chloride and bromide, leading the vapour' of said tetrahalide in an unsaturated state over'the heated material, thereby to form a vapour mixture containing said tetrahalide and lower normally stable titanium halides, leading. said vapour mixture toacooler zone whereby the lower halides condense as-solids except fora small amount which decomposes into tetrahalidevapour and purified titaniu m which condenseswith thelowerh'alides, reducing the tetrahalide pressure in said cooler zone to a value. lower than the decomposition ressure of'th'e lower halides while heatingthe condensate' therein toatemperaturebelow the temperature at-Which under the applied pressure the halides willdissociate intometallietitanium and free halogen, thereby to decompose thdctindensedi lower halides into purified metallic tiraniumandtetranalide vapour, and re-using. the -tetrahalide-from thecondensa'tion' and decomposition steps for further extraction of titanium from the-titanium bearing material. 7

A'process for extracting titanium from titanium hearing material of the group consisting of impure tita-' nium and titanium alloys which comprises the following steps, all carried out in an inert atmosphere; heating the titanium bearing material, evaporating a titanium tetrahalide of the group consisting of chloride and bromide, leading the vapour of said tetrahalide in an unsaturated state and under a partial vacuum over the heated material thereby to form a vapour mixture containing said tetrahalide and lower normally stable titanium halides, leading said vapour mixture to a cooler zone whereby the lower halides condense as solids except for a small amount which decomposes into tetrahalide vapour and purified titanium which condenses with the lower halides, reducing the tetrahalide pressure in said cooler Zone to a value lower than the decomposition pressure of the lower halides while heating the condensate therein to a temperature below the temperature at which under the applied pressure the halides will dissociate into metallic titanium and free halogen, thereby to decompose the condensed lower halides into purified metallic titanium and tetrahalide vapour, and re-using the tetrahalide from the condensation and decomposition steps for further extraction of titanium from the titanium bearing material.

3. A process for extracting titanium from titanium bearing material of the group consisting of impure titanium and titanium alloys which comprises the following steps, all carried out in an inert atmosphere; heating the titanium bearing material, evaporating a titanium tetrahalide of the group consisting of chloride and bromide, leading the vapour of said tetrahalide in an unsaturated state over the heated material, thereby to form a vapour mixture containing said tetrahalide and lower normally stable titanium halides, leading said vapour mixture to a cooler zone whereby the lower halides condense as solids except for a small amount which decomposes into tetrahalide vapour and purified titanium which condenses with the lower halides as flakes, reducing the tetrahalide pressure in said cooler zone to a value lower than the decomposition pressure of the lower halides while heating the condensate therein to a temperature below the temperature at which under the applied pressure the halides will dissociate into metallic titanium and free halogen, thereby to decompose the condensed lower halides into flakes of purified metallic titanium and tetra halide vapour, and re-using the tetrahalide from the condensation and decomposition steps for further extraction of titanium from the titanium bearing material.

4. A process for extracting titanium from titanium bearing material of the group consisting of impure titanium and titanium alloys which comprises the following steps, all carried out in an inert atmosphere; heating the titanium bearing material, evaporating a titanium tetrahalide of the group consisting of chloride and bromide, leading the vapour of said tetrahalide in an unsaturated state over the heated material, thereby to form a vapour mixture containing said tetrahalide and lower normally stable titanium halides, leading said vapour mixture to a cooler zone whereby the lower halides condense as solids except for a small amount which decomposes into tetrahalide vapour and purified titanium which condenses with the lower halides, reducing the tetrahalide pressure in said cooler zone to a value lower than the decomposition pressure of the lower halides while heating the condensate therein to a temperature below the temperature at which under the applied pressure the halides will dissociate into metallic titanium and free halogen, thereby to decompose the condensed lower halides into purified metallic titanium and tetrahalide vapour, leading the vapour from the condensation and decomposition steps into a still cooler zone to condense said tetrahalide, heating said condensate in said last named zone to re-evaporate said tetrahalide and using said tetrahalide vapour for further extraction of titanium from the titanium bearing material, at least two such still cooler zones being provided and used alternately as condenser and evaporator.

5. A process for extracting titanium from titanium bearing material of the group consisting of impure titanium and titanium alloys which comprises the following steps, all carried out in an inert atmosphere; heating the titanium bearing material, evaporating a titanium tetrahalide of the group consisting of chloride and bromide, leading the vapour of said tetrahalide in an unsaturated state over the heated material, thereby to form a vapour mixture containing said tetrahalide and lower normally stable titanium halides, leading sai-d vapour mixture to a cooler zone whereby the lower halides condense as solids except for a small amount which decomposes into tetrahalide vapour and purified titanium which condenses with the lower halides, reducing the tetrahalide pressure in said cooler zone to a value lower than the decomposition pressure of the lower halides while heating the condensate therein to a temperature below the temperature at which under the applied pressure the halides will dissociate into metallic titanium and free halogen, thereby to decompose the condensed lower halides into purified metallic titanium and tetrahalide vapour, at least two such cooler zones being provided and used alternately as lower halide condensers and decomposers, and re-using the tetrahalide from the condensation and decompositon steps for further extraction of titanium from the titanium bearing material.

References Cited in the file of this patent UNITED STATES PATENTS 1,046,043 Weintraub Dec. 3, 1912 2,670,270 Jordan Feb. 23, 1954 2,706,153 Glasser Apr. 12, 1955 OTHER REFERENCES Deutsche Chemishe Gesellschaft Berichte, Jahrig 44, Band 3. Oct. 9, Dec. 11, 1911. Pages 2906-2915.

A Comprehensive Treatise on Inorganic and Theoretical Chemistry by Mellor, vol. VII, page 74. Pub. 1927 by Longmans, Green & Co., 55 fifth Ave., N. Y.

Information Circular 7381, Nov. 1946, pages 5, 6. Pub. by Bureau of Mines, D. C.

Bureau of Mines Report of Investigations 4519. Pub. Aug. 1949 by Bureau of Mines, Dept. of Interior, Washington, D. C. Page 13.

Jordan, Abandoned application Serial No. 165,863, filed June 2, 1950.

Claims (1)

1. A PROCESS FOR EXTRACTING TITANIUM FROM TITANIUM BEARING MATERIAL OF THE GROUP CONSISTING OF IMPURE TITANIUM AND TITANIUM ALLOYS WHICH COMPRISES THE FOLLOWING STEPS, ALL CARRIED OUT IN AN INERT ATMOSPHERE; HEATING THE TITANIUM BEARING MATERIAL, EVAPORATING A TITANIUM TETRAHALIDE OF THE GROUP CONSISTING OF CHLORIDE AND BROMIDE, LEADING THE VAPOR OF SAID TETRAHALIDE IN AN UNSATURATED STATE OVER THE HEATED MATERIAL, THEREBY TO FORM A VAPOUR MIXTURE CONTAINING SAID TETRAHALIDE AND LOWER NORMALLY STABLE TITANIUM HALIDES, LEADING SAID VAPOR MIXTURE TO A COOLER ZONE WHEREBY THE LOWER HALIDES CONDENSE AS SOLIDS EXCEPT FOR A SMALL AMOUNT WHICH DECOMPOSES INTO TETRAHALIDE VAPOUR AND PURIFIED TITANIUM WHICH CONDENSES WITH THE LOWER HALIDES, REDUCING THE TETRAHALIDE PRESSURE IN SAID COOLER ZONE TO A VALUE LOWER THAN THE DECOMPOSITION PRESSURE OF THE LOWER HALIDES WHILE HEATING THE CONDENSATE THEREIN TO A TEMPERATURE BELOW THE TEMPERATURE AT WHICH UNDER THE APPLIED PRESSURE THE HALIDES WILL DISSOICATE INTO METALLIC TITANIUM AND FREE HALOGEN, THEREBY TO DECOMPOSE THE CONDENSED LOWER HALIDES INTO PURIFIED METALLIC TITANIUM AND TETRAHALIDE VAPOUR, AND RE-USING THE TETRAHALIDE FROM THE CONDENSATION AND DECOMPOSITION STEPS FRO FURTHER EXTRACTION OF TITANIUM FROM THE TITANIUM BEARING MATERIAL.