US3276851A - Method of processing metallic salts, in particular metal halides, designed for the production of metals - Google Patents

Description

Oct. 4, 1966 B. BERGHAUS ET 3,275,351

METHOD OF PROCESSING METALLIC SALTS, IN PARTICULAR METAL HALIDES, DESIGNED FOR THE PRODUCTION OF METALS Flled Jan 10 1961 2 Sheets-Sheet 1 INVENTORS BEP/VHAPD BEPGHHUS MAP/E STAESCHE BY fi'my/% ATTORNEYS Oct. 4, I966 BERGHAUS ETAL 3,276,851 METHOD OF PROCESSING METALLIC SALTS, IN

PARTICULAR METAL HALIDES, DESIGNED FOR THE PRODUCTION OF METALS 2 Sheets-Sheet 2 Filed Jan. 10. 1961 INVENTORS BER/VHA/PD ERG/MUS MflP/E STAESCHE BY MAM ATTORNEYS United States Patent 3,276,851 METHOD OF PROCESSING METALLIC SALTS, IN PARTICULAR METAL HALIDES, DESIGNED FOR THE PRODUCTION OF METALS Bernhard Berghaus, Zurich, and Marie Staesche, Wettingen, Aargau, Switzerland, assignors to Elektrophysil alische Anstalt Bernhard Berghaus, Vaduz, Liechtenstein, a corporation of Liechtenstein Filed Jan. 10, 1961, Ser. No. 81,735 Claims priority, application Switzerland, Jan. 11, 1960, 231/60; Jan. 14, 1960, 367/60; Jan. 22, 1960, 749/60 9 Claims. (Cl. 23-345) The present invention relates'to' methods of processing metallic salts designed to produce metals, the said metallic salts either being derived directly in the extraction process in their pure form, by way of example as metal chlorides, or obtained with comparative ease from the original or intermediate products which have been decomposed, or otherwise produced.

It is generally known that metals at present industrially employed can be mined in their pure form only in very rare cases, e.g. in places where large meteors have struck which largely consist of such a pure metal. The majority of the metals at present employed on an industrial scale, however, are obtained by more or less complex manufacturing processes from metallic compounds deposited in ore or salt beds.

The costs involved in this manufacturing process play a very important-if not decisive-role in respect to the price of the metal. By way of example, the price of aluminum in the middle of last century was in the order of magnitude of the gold price, which was largely attributable to the costs involved in the manufacturing processes.

But even now in a period of large-scale production of metals, the production costs per ton of metal exceed the cost of the initial material processed in the vast majority of cases. It has therefore always been the concern of specialists in the art to lower the production costs to the greatest extent possible.

Now science, particularly chemistry and physical chemistry, provide a large number of possibilities which all involve the production of the pure metal from the base material, the metallic compound. A substantial portion of these possibilities is excluded from the very outset because the process required to perform the method cannot economically be applied at the present stage of technology, not so much because each step in the process is uneconomical but mostly because these processes at one point produce a compound of which the further processing entails substantial difiiculties.

Experts specializing in the field of metal production have therefore more intensively studied the remaining processes which they found to be the only ones permitting economical performance, and have developed the methods based on those possibilities of solution to the very last details. By way of example, in the production of the various principally employed metals, each metal has a certain production method which is deemed to be the most economical.

To cite an example, aluminum is produced in the following manner: The available raw material, bauxite, Al O -nH O (n=1, 2 or 3), with impurities of iron hydroxide Fe(OI-I) is ground and boiled in caustic soda solution, and the aluminate solution obtained separated from the undissolved iron hydroxide by filtering, to be subsequently precipitated from the filtrate:

in the form of aluminum hydroxide Al(OH) by introducing CO 3,276,851 Patented Oct. 4, 1966 The intermediate product Al('OH) obtained is trans- "ice formed into aluminum oxide A1 0 by calcining, from which pure aluminum is obtained by means of fusion electrolysis with a fusion composed of approximately 10% A1 0 andapproximately cryolite Na AlF the product collecting in the box which forms the cathode.

The disadvantages encountered with this fusion electrolysis, such as the evaporation of the fusion and the required electrical power of 20 kwh. per kilo of aluminum, and the fusion temperature of approx. 950 C. required to perform fusion electrolysis were accepted as unavoidable since on substantial improvement of these properties of fusion electrolysis could apparently be achieved, particularly through direct channels.

As many parallel cases in technology reveal, the improvement of such factors already regarded as permanent requires basic research which does not proceed with a view to improving one or several of these factors considered to be predetermined, but which disregards the prejudices held by specialists in the art-that the methods applied constitute an optimum in respect of economy-and seeks and tests fundamentally new processes although the solutions underlying such processes reach a point where the further processing of the intermediate product obtained involves, according to the views currently held, such expenditure as to make the processes unec-onomical for large-scale application from the very outset.

In such a search for new methods of producing metals, the inventors proceeded from the well-known fact that the halides of the metals involved can be obtained with relative ease during the processing and extracting operations, by way of example in the case of aluminum from the aluminum hydroxide Al-( OH) obtained as an intermediate product, under the action of hydrochloric acid HCl in the form of and furthermore that the natural deposits of the compounds of some metals are already in the form of the halides of these metals, e.g. "besides the chlorides of the alkali metals sodium and potassium, particularly the halides, also obtained from salt deposits, of magnesium-magnesium chloride and magnesium bromide which is gaining more and more importance as a raw material.

This starting point, however, at first appeared to offer only little prospect inasmuch as it was considered a general fact that these metal halides can be separated from their halogen content only at considerable expense because the halides are bonded comparatively firmly to the metal, and that also in any case the working up, particularly of the higher valence metal halides, is associated with considerable difliculties because of their instability toward air and moisture.

In accordance with the invention, this basic problem in a process for treating salts or salt-containing starting materials for the purpose of reducing the salt-forming content, and particularly for the treatment of metal halides for the purpose of reducing their halogen content is solved by bringing into reaction with the salt or saltcontaining starting material, substances, e.g. nitrogenhydrogen compounds, and, among them, particularly ammonia, and preferably attached to the salt, to which compounds the anionic portion of the salt, i.e., the salt former, has in definite temperature ranges a greater afiinity than to the cationic portion of the salt, i.e., to the metal, to such a degree that these substances are capable in such temperature ranges to tear away the anionic portion of the salt from the cationic portion, e.g., to remove the salt former from the metal and bind it.

The reduction of the salt-former content or of the it halogen content is effected by subjecting the salt to a temperature treatment under the action of the substances to be brought into reaction or to be attached or added thereto and to this end is brought to a temperature which is within the said temperature range of higher aifinity of the anionic portion of the salt, i.e., of the salt-former, to the substances to be brought into reaction or added substances, than to the cationic portion of the salt; thus for example, to the metal, and kept at this temperature until the salt or the addition compound is freed of a quantity of its halogen salt-former, e.g., content which is predeterminable from the temperature selected.

This second step, which constitutes a temperature treatment may either be performed in a separate installation designed therefor or, as disclosed in the following examples of application, constitute part of those processes in which the addition compounds with the metallic salts produced as intermediate products in the first step are employed. Such a possibility of performing the second step not separately but in conjunction with such a process will always be present if the intermediate products within the process are subjected to a corresponding temperature treatment as in the second step.

Since the intermediate products obtained in the first step are not stable in air in contradistinction to the final products obtained in the second step, but will decompose, e.g. if ammonia has been added, into the corresponding metal hydroxide and ammonium chloride in the presence of air so that they are most difiicult to handle in that they must not come into contact with air, these intermediate products may particularly be employed where the temperature treatment is the result of a chemical process in which these intermediate products are involved and in which, :as shown in a practical example below, e.g. the heat of formation necessary for the temperature treatment is released owing to the formation of a compound, while in all cases in which both the intermediate product and the final product may be employed the final product is preferably employed owing to the greater ease of handling.

In investigating the usability of the final product obtained in the second process, the inventors made the surprising discovery that this final product excellently lends itself for addition to the melt in the fusion electrolysis designed to produce a metal. The improvements so achieved, e.g. in the fusion electrolysis of aluminum with only small additions of approximately to the melt are, firstly, a reduction of evaporation of the melt; secondly, a substantial increase in the conductivity of the electrolyte and a considerable reduction, connected therewith, .of the power consumption per unit weight of aluminum produced, and, thirdly, a reduction of the melting temperature of the melt.

Since the temperature of the melt is within the said temperature range in which the halogen possesses greater afiinity to the added substances than to the metal, it was to be expected, in accordance with the above facts, that the use of the intermediate product as in addition to the melt would involve a corresponding advantage since these intermediate products in the melt will first be subjected to the same temperature treatment as in the second-step of the method. A check revealed this assumption to be correct and it was found that the intermediate products vwill entail an absolutely similar effect as the final products provided that the metal content of the quantities added is the same as in the final products. Accordingly, if the intermediate products are used, the additions must, in view of their lower metal content relative to the final product, be correspondingly larger; in the example of the fusion electrolysis of aluminum approximately at 3% of the melt.

An example in which only the use of the intermediate products obtained in the second step may be practically considered is their use as a raw material for the production of metals in the application of methods in which .free

metal is formed under the action of reducing agents ionized by means of electrical discharges, upon the raw material. In these processes, part of the substances contained in the intermediate products and added to the metallic salt will combine with the reducing agents, preferably ionized gases, acting on the intermediate product and ionized by means of an electrical discharge, particularly a glow discharge, and therefore highly reactive, the said compound separating from the intermediate product. The heat of formation obtained in the formation of this compound heats the metallic salt and the residual added substances to temperatures within the temperature ranges in which the added substances, on the one hand, are separated and the halogen possesses, on the other hand, Such higher aifinity to the added substances than to the metal that it is torn away by the separating added substances and combines at least with part of these separating added substances and combines at least with part of these separating added materials so that free metal, compounds of the added substances and the halogen, and compounds of the added substances and the reducing agents acting upon them, elements released in the formation of one compound being capable of co-operating in the formation of the other compound or, respectively, being contained therein.

The metallic salts and raw materials containing metallic salts are preferably metal halides and initial materials containing metal halides respectively, such as compounds of a metal and iodine, bromine, fluorine or chlorine. Among these preferred metal halides and raw materials containing metal halides, again the metal chlorides or raw materials containing metal chlorides are preferred, such as AlCl BeCl MgCl- TiCl Besides, certain metallic salts or raw materials containing metallic salts will enter into consideration for the treatment according to the method of the invention, particularly metal nitrites and raw materials containing metal nitrites, such as Cu(NO met-a1 nitrates and raw materials containing metal nitrates, such as Cu(NO Ca(NO Zn(NO and Cd(NO metal chlorates and raw materials containing metal chlorates, such as Cu(ClO Zn(ClO and Cd(ClO and metal perchlorates or raw materials containing metal perchlorates, such as Cu(ClO and Cd(ClO The first step of the method is preferably performed in such a manner that the metallic salt or the raw material containing the metallic salt and the substances to be added to it to form the addition compound are introduced into a reaction vessel in very fine dispersion and in such a mandiate products obtained in the first step of the method,

for a protective gas atmosphere free from oxygen to be provided in the reaction vessel.

Of particular advantage is a very fine distribution of the metallic salt or of the raw material containing the metallic salt in an oxygen-free carrier gas free from oxygen, which cannot react with the same and which simultaneously can act as a protective gas for the addition compound formed in the reaction vessel, e.g. a rare gas such as argon or -a molecular nitrogen.

The metallic salt and, respectively, the raw material containing the metallic salt is preferably dispersed in the carrier gas in the form of vapour, this dispersion being obtained, by way of example, in such a manner that the carrier gas is passe-d, in the form of gas bubbles, through the metallic salt or the raw material containing the metalhe salt in the liquid state and heated to evaporation temperature.

The substance designed for addition should preferably formance of the method and should further naturally be in very fine dispersion. Ammonia gas is suitable as a substance for addition.

The number of molecules of the substance designed for addition which add themselves in this addition process to a molecule of the metallic salt or of the raw material containing metallic salt will then essentially depend on the temperature at which this addition is performed. Accordingly, the temperature should be selected in accordance with the number of molecules desired for addition to a metallic salt molecule. In order to provide the temperature selected for the performance of the method, the heat released in the exothermic formation process of the addition compounds will preferably be employed at least in part. In addition, extraneous sources of heat acting on the reaction point may be employed to produce the temperature selected for the performance.

The temperature required for the performance is preferably obtained by keeping the supply of metallic salt or the raw material containing the metallic salt at a temperature depending on the heat supply by the exothermic formation process (e.g. TiCl for the formation of at minus C. to 0 C., for the formation of at plus 20 C., and for the formation of TiCl -4NH at plus 80 C. to plus 90 C.) and supplied to the reaction vessel at this temperature.

The process is advantageously performed at such a temperature that the number of the molecules of the substance selected for addition added to a molecule of the metallic salt or the raw material containing the metallic salt is as small as possible and that the quantity of the substances designed for addition required per unit volume of the metallic salt or the raw material containing the metallic salt to form the addition compound is kept at a minimum. In this connection it should be pointed out that the final product obtained in the second step of the method at such a period of processing the intermediate product so that the separation of the compound formed of the added substances and the halogen removed from the metal from the intermediate product at the end of the processing period has reached its boundary value depending on the operating temperature in this second step, consequently ceases, independently of the number of molecules originally added to a molecule of the metallic salt, exercises the same effect, and apparently also possesses the same composition.

Furthermore, the first step of the method is preferably performed in such a manner that the volumes of metallic salt or raw material containing the metallic salt supplied to the reaction vessel per unit time on the one hand, and the substances designed for addition on the other are so adjusted in accordance with the number of molecules to be added to the former volume at the temperature selected for the performance of the method that they may fully react With one another.

It is furthermore advantageous to adjust the metallic salt or the raw material containing the metallic salt on the one hand, and the subtsances designed for addition on the other in such a manner in respect of their mutual chemical action that the addition compound forming the reaction product is a solid substance and will therefore precipitate. Such a reaction product, which is obtained in powder form, may be compressed by pressing the powder in moulds at a higher amount of pressure, e.g. kgs. per sq. cm.

In the second step of the method operation is performed at a temperature corresponding to the desired degree of stabilization of the final product, the said degree of stabilization being determined mainly by the desired stability of the final product in respect of air, humidity and other atmospheric influences.

The intermediate products should preferably be subjected to a treatment, in the second step, of a duration designed to ensure that the separation of the compound formed of the substances added and the halogens removed from the metal of the intermediate product reaches, at the end of the treatment period, its boundary value dependent on the processing temperature, and will therefore Cease.

With intermediate products unstable in air, the second step of the method, too, must be performed in an oxygenfree protective gas atmosphere.

From the compound separating from the intermediate product and formed of the added substances and the halogens removed from the metal, the substances used for addition may advantageously be recovered by treatment with appropriate chemicals and again be supplied to the process for the formation of further addition compounds, by way of example, in the case of NH added to metal chlorides, by passing the separating NH Cl into lime milk Ca(OH) for recovery of the NH The final products obtained in the second step of the method may further be transformed, after heat treatment, into a nitrate stable in air and water by fuming off with small quantities of concentrated nitric acid HNO at a maximum of C.

The method according to this invention may be employed with particular advantage with halides of a metal of the group of light metals such as aluminum, magnesium, beryllium and titanium. Among these, again the chlorides of the said metals enter into consideration. The first step of the method may, by way of example, be designed to form one of the addition compounds AlCl -2NH MgCl -2NH BeCl -4NH and TiCl -4NH which is then subjected to the corresponding heat treatment in the second step.

Apart from the halides of the said light metals principally envisaged for the treatment by the method according to the invention, the halides of a metal of the group including vanadium, tin, hafnium, zirconium, thorium, uranium, boron, tantalum, molybdenum, tungsten, niobium and cerium Will enter into consideration mainly for the formation of ammonia addition compounds, such as for the formation of ThCl -6NH UCl -8NH MoCl -6NH which Will then be subjected to the heat treatment disclosed in the second step of the method.

The final products or intermediate products obtained from a metallic salt by the method according to this invention are preferably employed as additions for the melt in the fusion electrolysis for the production of this metal and there offer great advantages. In particular, final products or intermediate products obtained from the metallic salt of a metal of the group of the light metals aluminum, magnesium, beryllium and titanium Will be employed as additions to the melt in the fusion electrolysis for the production of the metal in question.

By Way of example, ammonia addition compounds to AlCl obtained by the method according to this invention will be suitable in this form or after heat treatment according to the second step as additions to the melt containing an approximately 100% alkali metal aluminum fluoride like N a AlF for the fusion electrolysis employed to produce aluminum. A further example is presented by the ammonia addition compounds to TiCl obtained according to the method of the invention, which are excellently suited as additions to a melt containing an approximately 100% alkali metal titanium fluoride like K TiF likewise in the form of either an addition compound or after a heat treatment according to a second process step in the fusion electrolysis for the production of titanium.

The intermediate products or final products of a metal of the group comprising vanadium, tin, hafnium, zirconium, thorium, uranium, tantalum, boron, molybdenum, tungsten, niobium and cerium obtained under the method according to this invention are perfectly suitable as additions to the melt in the fusion electrolysis for the production of this metal.

produced by fusion electrolysis.

Furthermore, intermediate products or final products obtained from the salt of a metal under the method according to this invention may advantageously be employed as additions to the melt in the fusion electrolysis for the production of another metal, e.g. intermediate products or final products obtained from a salt of zirconium as addition to the melt in the fusion electrolysis for the production of titanium. This is of advantage particularly when the metal of which the salt is to be added to the melt as an addition after treatment by the method according to this invention is designed to become an alloying constituent of the metal contained in the solution. In this case, the volume added should advantageously be so selected that the corresponding alloying constituent percentage desired is contained in the metal In-addition, it may be of great advantage, e.g. with an alloy consisting of a base metal and a plurality of alloying constituents, to employ as additions various intermediate products or final products obtained from the salts of several-metals, e.g. from all or a portion of the metals used as alloying constituents, by the method according to this invention, by way of example in quantities corresponding to the alloying percentages, to the solution in the fusion electrolysis for the production of e.g.

the base metal. Both additions obtained only from the salts of the alloying metals and, furthermore, an addition obtained (from the salt of the base metal may be employed.

When intermediate products not stable in air are employed as additions to the melt, they must be supplied to the solution in the absence of air, i.e. While an oxygen-free protective gas is employed.

The substances recited as additions to the melt are preferably employed in a small percentage of the melt, which is normally between 0.2 and Naturally, this applies not to the case above disclosed when certain alloying percentages are to be obtained because the quantity of the substance added is determined by the alloying percentage desired.

The substances employed-as additions to the melt may very advantageously be employed to lower the temperature of the electrolyte and, respectively, of the melting temperature of the solution, to reduce evaporation of the solution and to increase the conductivity of the electrolyte and, along With that, to reduce the consumption of electrical energy per unit weight of the metal produced.

The use of the substances cited as additions to the solution furthermore oifers the great advantage that they form crystal nuclei around which the monocrystals of the metal contained in the solution will form.

The method according to this invention is described in greater detail in reference to the description of devices for the performance of the said method and of several examples illustrative of the method. In the drawing:

FIG. 1 shows a laboratory-type device by means of which an addition compound is obtained from metal halides in the liquid state and a heat treatment performed of this addition compound, and

FIG. 2 shows a device by means of which an addition compound is obtained from metal halides in the liquid state and a chemical transformation of this addition compound under the action of ionized reducing agents along with a heat treatment occurring during transformation can be performed.

In the arrangement shown in FIG. 1 to perform the two steps of the method according to claims 1 and 2, the vessel 1 contains a metal halide, e.g. titanium tetrachloride in the liquid state. Supplied through the tube 2 is a carrier gas, by way of example molecular nitrogen, which must be varefully purified of oxygen. The carrier gas arises, in the form of gas bubbles, to the surface of the liquid metal halide heated to evaporation temperature and is accordingly enriched with a mist of this metal chloride while it rises. The temperature of the metal halide is so selected that the desired number of molecules are through for e.g. one hour.

added, inthe reaction with the substances designed for addition, to a molecule of the metal halide. By way of example, in the addition of ammonia to titanium tetrachloride at a temperature of the liquid titanium tetrachloride of minus 20 to 0 C., 8 molecules ammonia are added to a molecule of titanium tetrachloride; at a temperature of plus 20 C., 6 molecules ammonia, and at a temperature between plus C. and C., 4 molecules ammonia. Through the tube 3 this metal halide dispersed in the carrier gas in the form of vapour passes into the reaction vessel 4. The reaction vessel 4 is further supplied, through the tube 5, with ammonia gas which will immediately form a solid addition compound with the finely dispersed metal halide supplied, the said compound becoming visible, in the case of titanium tetrachloride, as a yellow turbidity and conglomerating soon into loose flakes at the wall and in the funnel-type lower portion of the reaction vessel 4 so as to be passed downward from time to time by means of the scraper 6. The surplus gases (molecular nitrogen and ammonia) are removed via the annular tube 7 communicating with the interior of the reaction vessel 4 via openings, and pass first into the collecting chamber 8 where particles of the addition compound formed which may have been carried along, can be deposited. The surplus gases will then emerge from the settling chamber 8 through the tube 9.

The reaction vessel 4 is connected to the transverse glass or Plexiglas tube 11 by means of a tapered neck portion 10 of sufficient width and taper so as to mate with the funnel-type lower portion of vessel 4. Arranged so ,as to be longitudinally slidable in the tube 11 is a steatite boat 12 which may be slid into the steatite tube 17 passing the heating oven 16 via the gas-tight stuffing box 13 by means of the rod 14, across the slide 15 in the tube 11. At the position Where the steatite boat 12 is placed for the heat treatment in the steatite tube 17, a thermocouple element 18 is located which indicates the available temperature at this point by means of the instrument 20 connected to element 18 via the lines 19. At its other end, the steatite tube 17 is again connected, in gas tight connection, with the delivery device formed of glass or Plexiglas, which is here composed, by way of example, of the tube 21 with the funnel 22 and the conical ground member 23 to which the neck of the flask 24 communicates in gas-tight relationship.

Prior to the experiment, the device is evacuated to at least one mm. Hg pressure and checked for tightness. It is then filled with dry ammonia gas through the tube 5. Subsequently, the metal halide finely dispersed in the carrier gas" is supplied to the reaction vessel 4 through the tube 3 and the product obtained collects in the steatite boat 12 located in the left-hand part of the tube 11. The boat is then shifted slowly to the right by means of the rod 14 attached to it until completely filled. The boat is thereupon moved further to the right over the slide 15 to the center of the oven 16 and there heated after the slide 15 has been closed. After reaching the desired temperature, the substance is kept at such temperature After a certain amount of cooling so as to protect the tube 21, the boat 12 is moved into the tube 21, tilted and emptied into the flask 24. During the entire heating and cooling process, ammonia gas is passed through the oven via the tube 17. The surplus ammonia gas and the heating products obtained are removed by means of an absorbing device not shown, and the ammonia gas is cycled to vessel 4.

At approximately 200 C. lwhite vapours of mostly ammonium chloride NH Cl begin to escape. If the temperature is held constant, the formation of a gas comprising ammonium chloride will stop after some time .and a product of yellow-to orange colour is obtained which is, however, largely stable-to atmospheric moisture.

On further heating additional ammonium chloride is formed. If the temperature is kept constant, evolution of gas again ceases but is resumed when the temperature is raised further. It has been found that ammonium chloride is formed in not inconsiderable quantities even at 1100 C.

The product in the boat depending on the temperature selected will be yellow, orange, brown, black or, at very high temperatures, brown with a bronze cast. The stability in atmospheric humidity and even to water treatment increases at higher temperatures without noticeable reduction of the chemical activity. A product calcined at temperatures as high at 1100 C. will still react with acids and exercise the improved effects as an additive for fusion electrolysis.

Behind the boat (towards the outlet) in the tube 17 there will always be located a batch of yellow, orange or brown colour which is composed mainly of ammonium chloride. On the average it will still contain up to about 2% of the metal of which the halide was the starting material in the process.

The boat 12 in the tube 11 may also be replaced by a conveyor and compressing worm driven via a shaft 14 which conveys the loose product coming from the vessel 4 through the wide neck in the direction towards the closed slide 15 forcing it against the same. This conveyor and compressing worm enables the loose product to be compacted into a tablet immediately in front of the slide and accordingly to be compressed. After opening the slide 15, this tablet may then be moved into the tube 17 in the oven 16 in a suitable manner and withdrawn from the oven after termination of the heating and cooling cycle. The use of such a pre-compacted tablet enables the throughput per unit time to be increased.

In the processing device disclosed above, the heating oven 16 may also be replaced by a device for dielectric high-frequency heating of the product. Heating of the addition compounds obtained in a glow or gas discharge vessel is also possible.

The final products so obtained may then be processed into metal directly. While the metal halides used as raw materials hold only a comparatively low percentage of metal owing to the relatively high atomic weight of the halogens, the major portion of the final products consists of the metal contained in the raw material. By way of example, the metal halide titanium tetrachloride usable as raw material contains about 25% titanium, and aluminum trichloride about 20% aluminum. The addition compound AlCl -2NH contains 64% chlorine, 16% aluminum, and the balance consists of NH If this addition compound is kept at a temperature of 420 C. for one hour, it will contain only 12% chlorine, 36% aluminum and the balance NH while 5% chlorine, 46% aluminum and the balance NH are found at a temperature of 500 C. It is seen that the percentage of the metal involved in the final product will rise with a rising temperature applied in the heat treatment.

However, it is substantially more advantageous to employ the heat treated addition products as the additives in fusion electrolysis. This procedure will now be discussed in greater detail in reference to examples of titanium and aluminum production.

In the fusion electrolysis for the production of titanium which is commonly used, the solution consists of approximately 5% of an alkali titanium fluoride, e.g. Na TiF and of approximately 95% other salts such as NaF and CaF and KCl, NaO and SrF This fusion electrolysis is performed at a voltage of approximately 3 volts and a solution temperature between 700 and 750 C., and produces a power efficiency of approximately 80%.

In fusion electrolysis including the electrolyte additives according to this invention, a solution consisting of almost 100% alkali titanium fluoride may be employed. If fractions of one percent :up to several percent, preferably approximately 1% of a final product obtained by means of heat treatment of an ammonia addition compound of titanium tetrachloride are added to such a solution using a titanium anode and a cathode formed of copper, nickel, steel or the like, voltages of below 1 volt, preferably between 0.5 and 0.7 volt, will produce pronounced separation of extremely coarse crystalline titanium at the cathode, which largely exceeds the titanium quantities dissolved at the anode and therefore originates in the solution. The addition substances here operate as crystal nuclei around which the monocrystals of the metal contained in the solution will form. The temperature of the solution, depending on the quantity of the substance added, will be around 700 C. to 730 C. and it is therefore substantially lower than the melting temperature of the pure alkali titanium fluoride which is at approximately 870 C. for Na TiF At the same time a power efficiency of between and is obtained on the basis of monovalent titanium. Instead of using the final heat-treated product, addition of the addition compound not subjected to heat treatment, i.e. the intermediate productfmay be employed with the same results. In this case, however, the quantities added must be increased, in accordance with the lesser titanium content of the untreated addition compound, so that the same titanium content is present in the addition. The quantities to be added here range between 1% and 10%, preferably 3% approximately. Without the addition of either the heat treated additive or the intercalcated addition compound, no metal will be separated under the same voltage conditions even if the temperature is raised beyond the melting point of the salt solution. After several hours of electrolysis, the current will drop. It will soon be restored to its original level by addition of further material. Electrolysis can in this manner be continued until the electrolyte is completely exhausted.

In the fusion electrolysis for the production of aluminum now commonly used, the solution consists of approximately 10% aluminum oxide A1 0 and approximately 90% of an :alkali aluminum fluoride, by way of example Na AlF This fusion electrolysis is performed with a voltage between 5 and 6 volts and a temperature of approximately 950 C. and will yield a power efliciency of approximately 95 When the electrolyte additive obtained according to the method of this invention in the form of an ammonia addition compound of aluminum chloride or a stable product obtained from this intermediate product by means of heat treatment is added in a volume which is in the range of fractions of one percent and several percent, preferably 1% by weight in the case of the heat-treated product, and at about three times this quantity, preferably approximately 3% by weight in the case of the intermediate product, considerable increase in the conductivity of the electrolyte and a reduction of the melting temperature of the solution by about C. to approximately 800 C. will be obtained. In order to maintain this solution temperature, the considerable increase in the conductivity of the electrolyte will necessitate a voltage of only about 1 volt. At this voltage, about the same current will flow as in the case where fusion electrolysis is performed without such additions at a voltage between 5 and 6 volts. In addition, the fusion electrolysis with additives enables a power efliciency based on monovalent aluminum of about 95 to 97% to be achieved. The reduction in the voltage and the increase of the absolute current efficiency by reason of the monovalence of the produced aluminum enable the electrical energy previously required for the production of 1 kilo aluminum in fusion electrolysis without additives to be lowered from 20 kwh. to 1 to 2 kwh. in the fusion electrolysis with additives. This improvement is quite considerable insofar as a large portion of the production costs of aluminum was accounted for by the electrical energy required for fusion electrolysis.

The method according to this invention may be applied to almost all metals and relates particularly to the metals capable of forming addition compounds with ammonia in the form of halides, occasionally also of nitrate, chlorates and perchlorates. The addition compounds, particularly ammonia addition compounds of metal halides, are

largely unstable in air and humidity. Some of the halides are solid and stable in air. This is particularly true of halides of the groups I and II as well as VI and VIII in the periodic table of elements. Apart from the group of the metalloids (Si, Ge, Sn) the center of the periodic table consists of the light metals and the so-called transition metals of which the halides are liquid or gaseous and unstable in air. The method according to this invention is particularly suited to these groups. It therefore relates particularly to the metal halides of titanium, zirconium, hafnium, thorium, niobium, vanadium, aluminum, beryllium, and boron. The method according to this invention may advantageously be applied also to other metal halides such as tin halides or halides which are hygroscopic, as magnesium chlorate, and the halides of the alkaline-earth metals, or to such halides as are stable in air, such as the halides of cerium, lanthanum and the halides of other rare earths, molybdenum and the like.

Among the metals investigated in respect of the applicability of the method according to this invention, the following are singled out for mention which belong to the following six groups:

I. Alkali metals Licl with 5, 4, 3, 2 and 1NI-I II. Alkaline-earth metals Ca, Sr, Ba

III. Light metals Be, Mg, Al, Ti

IV. Heavy metals A. Nonferrous heavy metals:

Cu, Pb, In, Hg, Cd, Sn, Sb, Bi, Ga In Tl, Cr, Gr, Th, U (Ni, Co)

(Ni and Co only insofar as addition compounds are present which may be obtained under certain circumstances.)

B. Iron and steel improving agents: Fe, Mo, V, Mn, Nb, Ta

The W which belongs here yields no addition compounds, but nitrides.

V. Semimetals B, As, Te

Boron produces, besides the imides typical of semimetals, e.g. (BI-I NI-I also a boron trichloroborazol (BClNH which can be decomposed in glow discharges in the manner discussed.

. VI. Rare earths Lanthanides, including scandium and yttrium.

Some addition compounds are cited as examples which may be formed with various metals taken from the number of metals investigated:

I LiCl with 5, 4, 3, 2 and lNH (Also LiBr and LiI) CaCl -8, 4, 2, 1NH

CaCl 2N2H4 Ca(NO 8, 4, 1NH

' Becl 12, 6, 4, 2NH

AlCl 14, 9, 7, 6, 5, 3,l /6,1NH

InCl -6, 5, 4, 2NH

IHCI22N2H4 111(NO3 2 6, 4, II1(NO3) 2 3N2H2 In(ClO -x NH (x not determined) In(ClO.,) -x NH (x not determined) 12 CdCl -6, 5, 4, 3, 2, 1NH3 CdC1 -2N H Cd(C1O 6, 4NH3 GaCl -14, 7, 6, 5, 3, 1NH

Bromides and iodides as well InCl 15, 7, 5, 3, 2, 1NH TlCl'3NH ThCl 18, 12, 7, 6, 4NH

as well as complex compounds AsCl -7, 4, 2NH

SbC1 -2, 1NH

SbCl -6, 4, 3NH

TeCl -6, 5, 4, 3NH MoCl 6NH besides complex compounds UCl 12, 8NH

FeCl 10, 6, 2, 1NH

bromides and iodides as well.

This list furthermore shows that the number of the ammonia molecules which may be added to a metallic salt molecule apparently does not seem to have a definite upper limit. In addition, it may be seen that other metallic salts enter into consideration in the place of the metal halides preferably employed in the method according to this invention. However, the number of other metallic salts in question is substantially smaller than the number of metal halides employable in the method according to this invention. In general, they are the anions N0 N0 C10 and C10 Further instances of these metal salts which may also be considered for the method according to this invention are the following:

On the other hand, e.g., titanium nitrate or titanium perchlorate do not form addition compounds with ammonia, but other products may be obtained by carefully turning off the final product obtained by means of heat treating an additive compound of titanium tetrachloride with nitric acid, chloric acid or perchloric acid. Compounds Will then be formed of which the cation is Ti while the anion may e.g. consist of N(NH, NH and N0 or C10 or C10 A number of embodiments of the method according to this invention are recited below:

Production of a titaniferous final product from ammonia gas and titanium tetrachloride.

Titanium tetrachloride is passed into the vessel 4 (FIG. 1) at room temperature, the yellow addition compound formed with ammonia collects in the boat 12 which is passed into the oven 16. After heating to 680 C. and a processing time of approximately 1 hour, the boat held a black product intermingled with brown particles, which was largely stable in air. The analysis for titanium dis closed, in the largely brown particles, 73.5% Ti; in the largely black particles, 66.2% Ti, and 69.4 to 70.6% titanium in the average substance depending on the mixing ratio.

The sublimate in the tube 17 was grey-white to green-yellow and contained between 0.4 and 2.9% Ti (0.4/O.5/0.6/0.8/0.9/1.1/2.5/2.9% Ti).

Produced in the same manner were:

An Al-containing final product from an AlCl addition compound A Be-containing final product from a BeCl addition compound An Hf-containing final product from a HfCL, addition compound A Mg-containing final product from a MgCl addition compound A Th-containing final product from a ThCL, addition compound A Zr-containing final product from a ZrCl addition compound A B-containing final product from a BCl addition compound A Ta-containing final product from a TaCl addition compound A Mo-containing final product from a MoCl addition compound A W-containing final product from a WCl addition compound A V-containing final product from a VCl addition compound.

In conjunction with the device shown in FIG. 2, the production is described of an addition compound to a metallic salt and the use of this intermediate product for the obtention of a metal according to a production method in which free metal is formed under the action of reducing agents ionized by means of an electrical discharge on the intermediate product and in which a heat treatment corresponding to the second step of the method is elfected by means of the heat of formation generated in the formation of the compound of the reduction substances.

The raw material selected is, by way of example, titanium tetrachloride in liquid from which is located in a supply tank 25 and designated at 26. From this supply tank 25 the metalliferous compound 26 is injected into the container 28 by means of gas pressure in the form of a finely dispersed liquid jet through the nozzle 27. The necessary gas which is under corresponding pressure is supplied to the supply tank 25 via the line 29. A gas must be selected, by Way of example argon, which cannot react with the metalliferous compound 26 and which can also operate as a protective gas for the intermediate product produced in the container 28. In the container 28, the finely dispersed titanium tetrachloride is intimately mixed with an atmosphere containing nitrogen and hydrogen, by way of example ammonia gas, which is blown in through the inclined tubes 30 in the direction of the liquid jet. This gas is supplied to the tubes 30 via a regulating member 31 from the container 32. It is also possible to employ a compound formed of nitrogen and hydrogen other than ammonia gas. Advantageously the gas volume supplied is adjusted to the quantity of the metal compound supplied in such a manner that the solid intermediate product will absorb a portion of the gas as large as possible. The surplus gas is pumped from the container 28 through the connection 33, a comparatively small pump output being sufficient for the purpose if the quantities supplied are adequately adjusted.

If titanium tetrachloride is atomized via the nozzle 27 and ammonia gas supplied through the tubes 30, a titaniferous solid addition compound will be formed as the intermediate product 34 which will be deposited at the lower end of the container 28. If the quantities of the reactants are adequately adjusted, the intermediate product will consist mainly .of TiCl -6NH i.e., form an addition compound consisting of titanium tetrachloride and ammonia. This intermediate product is stable if located in a suitable protective gas atmosphere. If desired, such a protective gas, such as argon, may be added to the gaseous reactant in the container 32 and be supplied to the reaction vessel 28 along with the latter. The protective gas should be so selected that it will not take part in the reaction in the container 28.

The solid intermediate product is removed from the lower portion of the container 28 by means of a suitable conveying device, such as the conveyor worm 36 driven by the shaft 35, and supplied for further processing in the second cycle of the production process.

In order to obtain the free metal from this intermediate product, the -latter is processed by way of example, in an ionized gas atmosphere which advantageously contains at least one of the constituents nitrogen and hydrogen. Depending on the processing conditions in this second cycle of the production process a more or less substantial portion of free metal may be obtained from the intermediate product.

In the embodiment disclosed, the intermediate product obtained in the first step is passed through the container 40 on an endless conveyor belt 39 running over the rollers 37 and 38, collected in the funnel 41 and removed from the container 40 by means of a suitable conveying device, by way of example by means of the conveyor worm 43 driven via the shaft 42. The product so obtained in the present case will contain at least portions of free titanium metal.

During the passage through the container 40 the intermediate product located on the conveyor belt 39 is subject to the action of the ionized gas jets 44 which are blown into the container 40 through the two nozzles 45. In the container 40 a predetermined mined gas pressure is maintained, e.g. by means of a pumping device connected to the tubular connection 46. Since the entire interior of the container 40 is supplied only by the gas jets 44, an ionized atmosphere is set up which can act on the intermediate product.

The gas jets 44 enter via a nozzle-type bore in the metallic inner member 47 which is electrically insulated against the metallic cover 49 of the container 40 by the insulator member 48. Arranged in front of the nozzle 45 are annular counter-electrodes 50 which are electrically insulated relative to the metallic wall of the container 40 by means of the insulator members 51. One of the metal inner leads 47 with its associated counterelectrode 50 is connected to the pair of terminals 52, the other metallic inner lead 47 with its associated counterelectrode 50 is connected to the pair of terminals 52.

The gas located in the container 55 is supplied, under adequate pressure, to the bores of the metallic inner members 47, the nozzles 45, via the lines 53 and the regulator 54. The container 55 is supplied with appropriate gases via the lines 56 and 57, either pure nitrogen or pure hydrogen or a mixture of nitrogen and hydrogen and, respectively NH being provided.

If an adequate pressure is maintained in the container 40 via the tubular connection 46 and if the gas is supplied, via the lines 53, under a pressure ensuring that a gas jet 'will emerge through each of the bores of the inner members 47, a voltage at the pairs of terminals 52 of e.g. to 400 volts may produce a so-called electrical ray discharge by means of which the gas jets 44 produced will undergo pronounced ionization.

If titanium tetrachloride is employed and ammonia gas as a reactant in the first step of the production process, a solid yellowish intermediate product 34 will be obtained which will be transformed into a powdery final product of a white-to-grey colour under the action of the ionized atmosphere in the container 40. An examination of this product has revealed that it contains a portion of free metallic titanium of approximately 15% and, in addition, hydrazine chloride and ammonium chloride as well as a small portion of titanium tetrachloride.

The separation of the final product obtained which, if the reaction has been complete (which is adjustable) consists of a time metal powder With NH Cl and N H Cl, is treated with water when metals are involved which are not or only with difficulty attached by water, such as titanium, and the metal filtered oil. The dissolved salts are heated 'with lime milk, NH being released from the NH Cl, and returned into the process (formation of the addition compound), while the hydrazine will be distilled off during further boiling.

If the metal reacts with water, separation is performed by sedimentation e.g. with a non-aqueous sedimentation agent.

In the device disclosed, the two cycles of the production process are performed in two separate reaction chambers, i.e. the first step is performed in the container 28 and the second step in the container 40. If the plant for the performance of the method is suitably designed, the two steps of the production process may, however, be performed during the passage of the substances involved through a common reaction chamber, the first step taking place upstream of the second step.

In the device disclosed the ionized gas atmosphere which is provided in the performance of the second step of the production process is create-d by a so-called ray discharge which may be considered to be a variant of the well-known gas and glow discharges. However, other electrical means for the ionization of the atmosphere to be passed by the intermediate product during the second production step may be applied, such as electrical spray and brush discharges as known in high-voltage technology and occasionally referred to as corona discharges. It is further possible to obtain ionization of the atmosphere by high-frequency gas discharges. The atmosphere may also be ionized by means of electrical arc discharges, but suitable measures must then be taken (by way of example magnetic widening of the arc) in order to create a zone as evenly ionized as possible without adversely affecting the intermediate products by excessive temperatures. Ionization of the gas atmosphere by intensive irradiation by accelerated corpuscles such as electrons or alpha rays is possible as well.

In the performance of the method according to this invention it has been found to be important that the degree of ionization of the gas atmosphere in the second step of the production process is adjusted .to the type and the volume of the intermediate products to be processed. Excessively intense ionization is just as unsuitable as deiicient ionization. It has been found to be advantageous for the gas jets impinging on the intermediate product in the device disclosed to consist of NH, and N since it appears that the desired chemical reactions of the intermediate product are advantageously affected by the recombine-ton, which takes part simultaneously, of dissociated nitrogen. It may 'be possible that this desirable efiect depends on the simultaneous occurrence of exothermic and endothermic chemical processes of which the thermal balance is at least substantially adjusted.

To conclude, this production method will be described in conjunction with an example:

In a device similar to that described in connection with FIG. 1, 10 gms. titanium tetrachloride was processed. The liquid titanium tetrachloride was atomized by means of nitrogen gas and mixed with 10 liters NH gas. A sulphurous yellow solid addition compound was spontaneously formed which chemical analysis revealed to be TiCl -6NH The two raw materials supplied were almost 100 percent transformed into the yellow intermediate product. This intermediate product can be stored indefinitely under a protective gas, in the present case nitrogen gas, but will rapidly decompose into a white compound in air, which consists mainly of TiO A small portion of NH Cl can be found as well.

The yellow intermediate product was subjected to an ionized gas jet formed of nitrogen in the absence of air and under protective gas respectively. The nozzle bore employed had a cross-sectional area of about 1 mm. and the gas supplied amounted to approximately 3 to liters per minute. Between the counter-electrode 50 and the nozzle body 47, an electrical voltage of 150 to 190 volts was applied and a negative pressure of about 30 mm. Hg maintained in the container 40. Under these conditions, an electrical power of approximately 40 watts had to be supplied. The metallic nozzle body 47 formed the cathode of the glow discharge or ray discharge produced.

In view of the small amount of intermediate product, the latter was piled on only one point of the conveyor belt 39 and this point subjected to the ionized gas jet 44 for a period of four hours. The intermediate product changed from a sulphurous yellow colour into white to grey.

After this processing period, the product obtained was removed :from the container 40 and dissolved in water, and a deposit of about 2 gms. could be filtered off which proved to be free metallic titanium. The titanium yield was therefore approximately in the present example. By titration of the filtered solution by means of an iodine solution according to Stolle, a content of 5.7 gms. hydrazine chloride (N H )Cl was found. The balance of the solution consisted of ammonium chloride NH Cl and a small quantity of unchanged titanium tetrachloride.

What we claim is:

1. A process for treating an ammonia addition compound of a metal chloride comprising heating said addition compound in an oxygen-free protective gas atmosphere to a temperature exceeding 200 C. to free ammonium chloride and maintaining the temperature a sufiicient time above 200 C. until the evolution of ammonium chloride ceases and recovering a product of increased stability consisting of metal, chlorine, nitrogen, and hydrogen and containing less atoms of chlorine, of nitrogen, and of hydrogen, per metal-atom than said addition compound of a metal halide.

2. A process as claimed in claim 1 wherein said protective gas comprises ammonia.

3. A process as claimed in claim 1 wherein said ammonium chloride is chemically treated to recover ammonia and said ammonia is transferred back to the process as protective gas.

4. A process as claimed in claim 1 wherein said product of increased stability is vaporized with small amounts of nitric acid at a temperature of less than C.

5. A process as claimed in claim 1 wherein said addition compound is heated by an electric gas discharge.

6. A process as claimed in claim 1 wherein the metal of said metal halide is selected from the group consisting of Al, Mg, Be, Ti, V, Sn, Hf, Zr, Th, U, B, Ta, Mo, Nb and Ce.

7. A process as claimed in claim 1 wherein the heating of said addition compound is at a temperature from 200 C. to 1100 C. p

8. A process for treating an ammonia addition compound of a titanium chloride comprising heating said addition compound in an oxygen-free protective gas atmosphere to a temperature exceeding 200 C. to free rammonium chloride and maintaining the temperature a sufiicient time above 200 C. until the evolution of ammonium chloride ceases and recovering a product of increased stability consisting of titanium, chlorine, nitrogen, and hydrogen :and containing less atoms of chlorine, of nitrogen, and of hydrogen, per titanium-atom than said addition compound of a titanium halide.

9. A process for treating an ammonia addition compound of an aluminum chloride comprising heating said addition compound in an oxygen-free protective gas atmosphere to a temperature exceeding 200 C. to free ammonium chloride and maintaining the temperature a suflicient time above 200 C. until the evolution of ammonium chloride ceases and recovering a product of increased stability consisting of aluminum, chlorine, nitrogen, and hydrogen and containing less atoms of chlorine, of nitrogen, and of hydrogen, per aluminum-atom than said addition compound of an aluminum halide,

References Cited by the Examiner UNITED STATES PATENTS 2,606,815 8/1952 Sowa 23190 X 2,654,654- 10/1953 Leah et a1. 23-145 2,659,655 11/1953 Sweet 2314.5

(Other references on following page) UNITED STATES PATENTS Me1lorA Comprehensive Treatise on Inorganic and 2 3 6 56 C 204 64 Theoretical Chemistry, Longmans, Green & Co., London, 52,3 x3 23 87 March 1947, vol. 4, 203, 234, 235, vol. 7, pp. 83, 84 2,904,486 9/1959 Bown et a1. 204-164 ii A C h T I d 2956 936 10/1960 Huber et aL 204 64 5 e or ompre ensrve reatrse on norgamc an 2970887 2/1961 Hm 23 87 Theoretical Chermstry (1947), vol. 5, pp, 319-320. 2,985,573 5/ 1961 chefrief et 204164 L. DEWAYNE RUTLEDGE, Primary Examiner. 3,117,837 1/1964 Haase 23190 I. R. SPECK, CARL D. QUARFORTH, REUBEN OTHER REFERENCES 10 EPSTEIN, Examiners.

Brager, A.: Chem. Abstracts, vol. 33, Ju1ySeptember T, JOHNSON, J, D VOIGHT, L. A, SEBASTIAN, 1939, 7168 (7) and 7074(6). Assistant Examiner.

Claims (2)

1. A PROCESS FOR TREATING AN AMMONIA ADDITION COMPOUND OF A METAL CHLORIDE COMPRISING HEATING SAID ADDITION COMPOUND IN AN OXYGEN-FREE PROTECTIVE GAS ATMOSPHERE TO A TEMPERATURE EXCEEDING 200*C. TO FREE AMMONIUM CHLORIDE AND MAINTAINING THE TEMPERATURE A SUFFICIENT TIME ABOVE 200*C. UNTIL THE EVOLUTION OF AMMONIUM CHLORIDE CEASES AND RECOVERING A PRODUCT OF INCRESED STABILITY CONSISTING OF METAL, CHLORIDE, NITROGEN, AND HYDROGEN AND CONTAINING LESS ATOMS OF CHLORINE, OF NITROGEN, AND OF HYDROGEN, PER METAL-ATOM THAN SAID ADDITION COMPOUND OF A METAL HALIDE.

6. A PROCESS AS CLAIMED IN CLAIM 1 WHEREIN THE METAL OF SIX METAL HALIDE IS SELECTED FROM THE GROUP CONSISTING OF AL, MG, TI, V, SN, HF, ZR, TH, U, B, TA, MO, NB AND CE.

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