US2793098A - Method of producing alkali metal titanium double fluorides in which the titanium has a valence of less than four - Google Patents

Description

United tats Eugene Wainer, Cleveland Heights, Ohio, assignor, by mesne assignments, to Horizons Titanium Corporation, Princeton, N. J., a corporation of New Jersey No Drawing. Application August 17, 1956, Serial No. 604,623

4 Claims. (Cl; Zi -83) This invention relates to a method for preparing titanium fluorides in which the titanium has a valence less than four. More particularly, it relates to a method for preparing simple fluorides of titanium or complex alkali-metal titanium fluorine compounds in which the titanium has a valence of less than four from readily available starting materials comprising, 1) alkali-metal fluotitanates in which the titanium is tetravalent, and (2) a titanium oxycarbide.

Lower valent titanium halides, and particularly lower valent titanium fluorides, have been recently shown to be useful for many purposes, particularly forthe production of titanium metal by thermal or electrolytic means. Several patents describe procedures whereby such lower valent halides may be produced. One such process is set forth in Patent 2,672,399, covering, a method of producing. alkali metal-titanium double fluorides in which the titanium has a valence of three by reacting titanium monoxide with an alkali metal fluoride and an acid fluoride at relatively low temperatures Another recently issued patent, namely 2,718,464, describes the reaction between an alkali fluotitanate in which the titanium is tetravalent and titanium bearing material such as impure titanium metal. Still another process is set forth in U. S. Patent 2,723,182 in which the preparation of lower valent alkali metahtitanium double fluorides, in which the titanium has a valence of less than four, from various oxides of titanium, carbon and alkali-metal titanium, double fluorides in which the titanium has a valence of four, is described.

I have now found that it is possible to prepare lower valent titanium fluorides directly from a reaction between a titanium oxycarbide, a term I use to designate titanium in combination with oxygen and carbon in certain proportions and an alkali metal fluotitanate in which the titanium has a valence of four. In my process the titanium oxycarbide is reacted with sodium, potassium or lithium fluotitanate by bringing these reactants into intimate contact with oxycarbide at temperatures within the range of 750 C. and about 1000" C. under an inert atmosphere. Alakli-metal chlorides, i. e., sodium, potassium or lithium chlorides, may also be included among the reactantsas diluent salts. As a result of the reaction, an alkali-metal titanium double fluoride in which the titanium has a valence of less than four is formed. The alkali-metal double fluoride product may be recovered from the reaction residue either by aqueous separation techniques or in the form of a molten bath of the product salt in the manner disclosed in the aforementioned U. S. Patent 2,723,182.

The alkali metal fluotitanates useful in the practice of my invention include sodium fiuotitanate, potassium fluotitanate and lithium fluotitanate. In order to avoid undesirable side reactions and possible contamination of the product, the fluotitanate employed should be of recrystallized quality. That is to say, the fluotitanate should be substantially free of silica and metallic impurities, and Should contain less than about .01% water and .01%

atcnt O ing the desired mutual titanium oxycarbide.

2,793,098 Patented May 21, 1957 insolubles. Because of the relative cheapness and availability of potassium fiuotitanate, I presently prefer to use this fluotitanate in my process. Therefore, in the interest of simplicity, my invention will be desciibed in connection with the use of potassium fiuotitanate as a representative of all metal alkali fluotitanates. However, it should be kept in mind that what is said with respect to potassium fluotitanate applies equally to the other alkali metal fluotitanates. Moreover, although the use of diluent alkali metal chlorides may not be specifically set forth, all reaction mixtures hereinafter referred to may contain as diluents alkali metal chlorides up to an amount equal molecularly to about the amount of alkali metal fluotitanate employed. Substantially chemically pure sodium, potassium and lithium chlorides suitable for use as diluents are available commercially. The alkali metal fluorides are not desirable diluents in the reaction mixture because of their ability to dissolve titanium oxides with the resulting formation of titanium oxyfluorides. Bromides and iodides of the alkali metals do not dissolve titanium oxides but these halides form unstable titanium bromides and iodides which decompose or disproportionate at high temperatures to evolve tetrabromides and tetraiodides of titanium.

The titanium oxycarbide employed in my process may be prepared by any of several equivalent techniques. For example, it may be prepared by reacting titanium monoxide, and carbon in the manner disclosed in one of my copending applications, Serial No. 369,513, that is, by forming an intimate mixture of the titanium monoxide withelement-al carbon in which the molar ratio of car bon to titanium monoxide is not greater than one, and heating the mixture toa, reaction temperature within the range of 1500 to 1800 C. Another method for preparsolid solution of TiC and TiO, which I have previously designated as titanium oxycarbide, is by reacting titanium sesquioxide with carbon in the manner disclosed in another of my copending applications, namely Serial ,No. 369,512. The process therein described comprises forming an intimate mixture of titanium sesquioxide and carbon in which the proportion of carbon in the mixture is greater than one but not greater than three times the number of mols of titanium sesquioxide in the mixture, and heating the mixture to a reaction temperature within the range of about 1500 to 1800 C. The titanium monoxide and titanium sesquioxide of a purity satisfactory for use in the above processes may be prepared in accordance with the methods disclosed in U. 8. Patents 2,681,847; 2,681,848; 2,681,849; 2,681,850 and 2,681,851, or in any other known fashion.

Regardless of the manner in which, the titanium oxycarbide or mutual solid solution of titanium carbide and titanium monoxide is produced, the material which is acceptable for the purposes of this invention may contain between 5% and 13% by weight of carbon andbetween 3% and 13% by weight of oxygen, and the balance titanium, provided that the carbon content is such that at least one atom of carbon is provided for each atom of oxygen in the oxycarbide. Preferably, a composition approximating Ti, 6% C and 4%. O by. weight is employed in the processes hereinafter described. Since the amount of carbon present in the oxycarbide is such that there is at least one atom of carbon for each atom of oxygen in the oxycarbide together with. a slight excess, the reaction is carried out under reducing conditions.

Theoretically, in order to prepare a trivalent complex alkali metal titanium fluoride, there should be 3 mols of normal (tetravalent) fluotitanates present in the reaction mixture for each mol of titanium ,present in the When it is desired to prepare. a divalent titanium fluoride a correspondingly smaller 3 amount of the normal fluotitanate is required in the reaction.

One method of carrying out my invention is to heat an intimate mixture of finely divided normal flu'otitanate and oxycarbide materials to a reaction temperature. Another method of bringing the titanium oxycarbide and fiuotitanate into intimate contact is to heat the fluotitanate to a temperature sufficiently high to vaporize it and then to pass the vapor over or through the titanium oxycarbide. In order to promote a complete reaction the oxycarbide should be in a form presenting the maximum surface area to the fluo'titanate vapor, and to this end I find that crushing the oxycarbide to a size of about 200 mesh (Tyler Standard) will serve my purpose. The oxycarbide may be held in a molybdenum or other refractory .metal boat and may, if desired, be supported on molybdenum wire to improve the contact between the vapor and solid phase.

In both of the foregoing modifications, the actual reaction takes place at temperatures between 750 C. and 1000 C. The resulting product in the first instance may be recovered as a molten salt and may be purified by simply filtering the salt through a suitable screen to remove any unreacted solid material. In the second modification, the lower valent titanium fluoride may be recovered as a vapor by sweeping the reaction zone with an inert atmosphere, for example with a noble gas, or by conducting the reaction in an actively pumping vacuum, or it may be recovered in the form of a condensed solid or liquid product.

Suitable apparatuses for carrying out my processes are described in both U. S. Patent 2,718,464 and 2,723,182 and are known in the art.

The following examples are illustrative but not limitative of the practice of my invention.

Example I A mixture of 76 parts by weight of a titanium oxycarbide (1 mole) having a formula corresponding to TizOC and 1440 parts by weight of potassium fluotitanate (K2Tis6 moles) was blended together. The mixture was placed in a molybdenum crucible and heated to a temperature of about 900 C. in an inert atmosphere furnace in which a continuously changing argon atmosphere had been established. The reactants were maintainedat reaction temperature for about 2 hours, whereupon the furnace was permitted to cool. The resulting product was a salt cake having a violet color. The salt cake was ground to a fine powder and was analyzed and was found to contain 24.7% titanium. Assuming the thermal reaction represented by the following equation, the percentage yield was 98.5%

Ti2OC+ 6K2TiFe- 8TiFa 12KF+CO Example I] 90 parts by weight of a titanium oxycarbide analyzing 90% titanium 6% carbon and 4% oxygen by weight (corresponding to the formula Ti1sO2C4) was placed in a molybdenum boat. A vapor formed by heating 910 parts by weight of potassium fluotitanate (KzTiFc) to about 950 C. was passed over the oxycarbide in the zone maintained at about 900 C. The resulting vapors were condensed on a cold titanium sheet. The solid product was analyzed and found to contain 48.1% titanium, indicating about a 3:1 molar ratio of trivalent titanium to divalent titanium. One possible representation of the reaction would be:

,tion of parts NaCl by weight to 1 part of oxycarbide by weight. The product was recovered as a molten salt. The molten salt product was filtered through a molybdenum wire filter and thereafter was electrolyzed in an inert atmosphere cell, such as that described in Patent 2,707,169. Titanium metal was deposited at the cathode.

I claim:

1. The method of producing alkali metal titanium double fluorides in which the titanium has a valence of less than four which comprises: bringing an alkali metal titanium double fluoride in which the titanium has a valence of four and a titanium oxycarbide into intimate contact in relative proportions such that up to three mols of tetravalent titanium are provided as alkali metal titanium double fluoride for each mol of titanium provided as oxycarbide at a temperature within the range of about 750 C. and 1000 C. under a fluid medium inert with respect to said alkali metal titanium double fluoride and titanium oxycarbide and recovering from the reaction zone at least one alkali metal titanium double fluoride in which the titanium has a valence of less than four.

2. The method of producing alkali metal titanium double fluorides in which the titanium has a valence of less than four which comprises: bringing an alkali metal between about 5-13 by weight of carbon and an amount of oxygen such that at least one atom of carbon is available for each atom of oxygen in said oxycarbide, in relative proportions such that up to three mols of tetravalent titanium are provided as alkali metal titanium double fluoride for each mol of titanium provided as oxycarbide into intimate contact under a fluid medium inert with respect to said double fluoride and oxycarbide and at a temperature within the range of about 750 C. and 1000" C. and recovering from the reaction zone at least one alkali metal titanium double fluoride in which the titanium has a valence of less than four.

3. The method of producing potassium titanium double fluorides in which the titanium has a valence of less than four which comprises: bringing a potassium titanium double fluoride in which the titanium has a valence of four and a titanium oxycarbide in which at least one atom of carbon is present for each atom of oxygen, in relative proportions such that up to three mols of tetravalent titanium are provided as alkali metal titanium double fluoride for each mol of titanium provided as oxycarbide into intimate contact at a temperature within the range of about 750 C. and 1000 C. and under an atmosphere inert with respect to said double fluoride and oxycarbide, and recovering from the reaction zone at least one potassium titanium double fluoride in which the titanium has a valence of less than four.

4. The method of producing a potassium titanium double fluoride in which the titanium has a valence of less than four which comprises: bringing a potassium titanium double fluoride in which the titanium has a valence of four and a titanium oxycarbide in which at least one atom of carbon is present for each atom of oxygen, in relative proportions such that up to three mols of tetravalent titanium are provided as alkali metal tit-anium double fluoride for each mol of titanium provided as oxycarbide into intimate contact in a fused melt consisting of at least one alkali metal chloride at a temperature within the range of about 750 C. and 1000 C. and recovering from the reaction zone at least one potassium titanium double fluoride in which the titanium has a valence of less than four.

References Cited in the file of this patent UNITED STATES PATENTS Sibert et al. Nov. 8, 1955 OTHER REFERENCES I. Barksdale: Titanium, 1949 ed., page 61, the Ronald Press 00., N. Y.

Claims (1)

1. THE METHOD OF PRODUCING ALKALI METAL TITANIUM DOUBLE FLUORIDES IN WHICH THE TITANIUM HAS A VALENCE OF LESS THEN FOUR WHICH COMPRISES: BRINING AN ALKALI METAL TITANIUM DOUBLE FLUORIDE IN WHICH THE TITANIUM HAS A VALENCE OF FOUR AND A TITANIUM OXYCARBIDE INTO INTIMATE CONTACT IN RELATIVE PROPORTIONS SUCH THAT UP TO THREE MOLS OF TETRAVALENT TITANIUM ARE PROVIDED AS ALKALI METAL TITANIUM DOUBLE FLUORIDE FOR EACH MOL OF TITANIUM PROVIDED AS OXYCARBIDE AT A TEMPERATURE WITHIN THE RANGE OF ABOUT 750*C. AND 1000*C. UNDER A FLUID MEDIUM INERT WITH RESPECT TO SAID ALKALI METAL TITANIUM DOUBLE FLUORIDE AND TITANIUM OXYCARBIDE AND RECOVERING FROM THE REACTION ZONE AT LEAST ONE ALKALI METAL TITANIUM DOUBLE FLUORIDE IN WHICH THE TITANIUM HAS A VALENCE OF LESS THAN FOUR.