DE1194591B - Process for the production of metals, in particular titanium and aluminum, by melt-flow electrolysis - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

C22d

German class: 40 c- 3/14

Number: 1194591

File number: E 20424 VI a / 40 c

Filing date: January 10, 1961

Opening day: June 10, 1965

The present invention relates to a method for the production of metals, in particular of titanium and aluminum, by fused-salt electrolysis from their halides.

Today there is a specific one for the extraction of each of the main metals used Manufacturing process that is considered the most economical.

For example, aluminum is produced as follows:

The bauxite available as a base material, Al ₂ O ₃ · wH ₂ O (k = 1.2 or 3), with impurities of iron hydroxide, Fe (OH) ₃ , is boiled in ground form in sodium hydroxide solution and the resulting aluminate solution is filtered separated from the undissolved iron hydroxide and then from this filtrate in the following form:

2 NaAlO ₂ + CO ₂ + 3 H ₂ O -> Na ₂ CO ₃ + 2 Al (OH) ₃

by introducing CO ₂ aluminum hydroxide, Al (OH) ₃ , precipitated. The resulting intermediate product, Al (OH) ₃ , is converted into aluminum oxide, Al ₂ O ₃ , by annealing, which is then converted into aluminum oxide, Al 2 O 3, by means of fused-salt electrolysis with a cryolite of about 10% Al ₂ O ₃ and about 90% cryolite, Na _{3 AlF 6} , existing «5 melt pure aluminum is obtained.

The ones that occur in aluminum fused-salt electrolysis Disadvantages, such as smoking off the melt and also the need for electrical equipment Energy of 17 to 20 kWh per kilogram of aluminum and that for the implementation of the melt flow electrolysis necessary melt temperature of about 950 ° C were considered unavoidable conditions accepted, because apparently and at least in a direct way there are no significant improvements these properties of the fused flux electrolysis can be achieved.

In a search for new methods of metal extraction, the inventors went from the known The fact that most metals in the preparation and extraction process with relative The halides of the metals can be produced with little effort and that also the natural ones Occurrence of the compound of some metals are already the halides of these metals, so z. B. in addition to the chlorides of the alkali metals sodium and potassium, in particular those also from salt deposits obtained halides of magnesium, namely magnesium chloride and magnesium bromide.

However, this starting point seemed to offer little prospect at first, as it was generally known that these metal halo processes could be used for the production of metals,
especially of titanium and aluminum
Molten electrolysis

Applicant:

Electrophysical Institute

Bernhard Berghaus, Vaduz (Liechtenstein)

Representative:

K. Gerlings, lawyer,

S'iegburg, Mühlenstr. 14th

Named as inventor:
Bernhard Berghaus, Zurich;
Dr.-Ing. Chem. Marie Staesche,
Wettingen (Switzerland)

Claimed priority:

Switzerland of January 11, 1960 (231),
of January 14, 1960 (367),
dated January 22, 1960 (749)

can not be decomposed or only with considerable effort in the fused-salt electrolysis, because the halogens are relatively tightly bound to the metal.

The object on which the invention is based was therefore to find a method to deal with The metal halides provided as the starting material and others, of course, require little technical effort to decompose existing or easily producible metal compounds in the fused-salt electrolysis and making the pure metals in the process.

According to the invention, this object is in a method for the production of metals, in particular of titanium and aluminum, by molten electrolysis in an electrolyte, the alkali halide and halide of the metal to be recovered, dissolved in that the electrolyte in proportionally small amounts, preferably between 0.2 and 5 percent by weight, of one or more additives are added that consist of addition compounds in which nitrogen-hydrogen compounds or their complex compounds with metal salts from the group of halides, nitrates, nitrites, chlorates

509 579/318

3 4

and perchlorates are deposited, consist or come from mainly the metal chlorides or metal-

this after a heat treatment in an acid chloride-containing starting material in question, z. B.

substance-free protective gas atmosphere were obtained. AlCl ₃ , BeCl ₂ , MgCl ₂ , TiCl ₄ . Come next to these

The additive used is preferably a product consisting of a further specified metal salts or metal addition compound to a salt of the starting materials containing salt to be produced for the production of metal or a product derived therefrom, in particular a metal product. It is also advantageous to use nitrites or metal nitrite-containing starting materials as an additive, e.g. B. Cu (NO ₂ ) ₂ , metal nitrates or metal nitrate compound existing or derived therefrom. B. Cu (NO ₃ ) ₂ , Ca (NO ₃ ) ₂ , genes product to use, in which on a molecule io Zn (NO ₃ ) ₂ and Cd (NO ₃ ) ₂ , metal chlorates or metal of the metal salt the lowest possible number of starting materials containing chlorate, e.g. B. Cu (ClO ₃ ) ₂ , molecules of the additive is attached. Zn (C10 ₃ ) ₂ and Cd (C10 ₃ ) ₂ , and metal perchlorates

When using the plant or metal perchlorate-containing starting materials, e.g.

tion compound as an additive of this to the electro- Cu (ClC> 4) ₂ and Cd (ClO ₄ ) U.

lytes under the exclusion of air or under an oxygen- 15 Die according to the method of the invention

supplied in a free protective gas atmosphere. Melt in the melt flow electrolysis to produce

In the production of titanium by the process according to the invention, additives added to metals, by fused-salt electrolysis, there are great advantages. In particular, an electrolyte containing alkali titanium fluoride contains additives consisting of ammonia and a metal, preferably an electrolyte consisting essentially of sodium halide of a metal from the group of light titanium fluoride and, as an additive, metals aluminum, magnesium, beryllium and titanium from an ammonia addition compound are produced, as additives to the melt in the case of a titanium halide, preferably titanium chloride, melt-flow electrolysis for the production of the resulting or resulting metal promising metals,
turns. 35 For example, ammonia accumulation

In the production of aluminum according to the compounds of AlCl ₃ already in this form or the method according to the invention by melt flow after a temperature treatment as an additive to the electrolysis in an essentially alkali z. B. about 10% Al ₂ O ₃ and 90% Na _{3 AlF 6} containing existing electrolyte is used as a melt in the fused-salt electrolysis for aluminum additive preferably from an ammonia 30 minium production. A further example is formed by the addition compound on aluminum chloride when a product produced by the process according to the invention or a product obtained therefrom is used. Ammonia addition compounds to TiCl ₄ , the

In the production of aluminum by the process according to the invention either as an addition compound by melt flow or after a temperature treatment as an additive electrolysis in a substantially alkali 35 to the z. B. about 5% Na ₂ TiF ₆ and 95% other aluminum halide and up to about 10% aluminum salts containing melt in the melt flux oxide existing electrolyte is suitable as an additive electrolysis for titanium production,
Preferably, the substances listed as a compound to an aluminum halide, preferably an additive to the melt, are used in a product consisting of aluminum chloride or a small percentage of the melt obtained from it. which is usually between 0.2 and 5%.

In some cases it can also be beneficial, with great advantage that can be used as an addition to as an additive, a substance listed from an addition compound to lower the melt to a salt of a temperature other than that to be obtained for the electrolyte or the melting metal existing or resulting 45 temperature of the melt, to reduce the Product or from addition compounds to salts fuming the melt and increasing the of the to be extracted and other metals existing conductivity of the electrolyte and thus for or resulting products or a reduction in the consumption of electrical energy used from addition compounds to salts of several metals produced per unit weight the metal to be extracted of various metals will be 5 °.

existing or resulting products The method according to the invention is now

to use. standing on the example of the production of titanium and

It is also advantageous to use an additive made from aluminum by fused-salt electrolysis.

an addition compound after one to tert.

Termination of the deposition of substances from the 55 In the previously customary fused-salt electrolysis for

Titanium production, the melt consists of about 5%

act to use the product received. Favorably an alkali titanium fluoride, for example K ₂ TiF ₆ , and

is also, as an additive, an addition of about 95% other salts, such as NaF and CaF ₂

compound after a in a flowing protective and KCl, NaO and SrF ₂ . This melt electrolysis

Gas atmosphere carried out heat treatment 60 is at a voltage of about 3 V and a

to use the product received. Temperature of the melt between 700 and 750 ⁰ C

The one operated for the production of the additives in question and gives a current efficiency, related

Coming metal salts or metal salt-containing compounds on tetravalent titanium, of about 80%.

transition materials are metal halides or metal- In fused-salt electrolysis with the addition of a

Halide-containing starting materials, for example an additive by the process according to the invention

Compounds between a metal and iodine, bromine, can be made from almost 100% alkali titanium fluoride

Fluorine or chlorine. Use existing melt from these metal halides. If you mix one

or metal halide-containing starting materials such a melt using a titanium anode

and a cathode made of copper, nickel, steel or the like. Fractions of a percent to a few percent, preferably about l ^o / _o , of an additive produced from an ammonia addition compound on titanium tetrachloride by means of heat treatment, then one obtains at voltages below 1 V. , preferably between 0.5 and 0.7 V, a strong deposition of extremely coarse crystalline titanium on the cathode, which far exceeds the amount of titanium dissolved at the anode, i.e. comes from the melt.

The additives act as crystal nuclei around which single crystals of the metal contained in the melt are formed. The melt temperature, depending on the amount of the additive at about 700 to 73O ⁰ C, is thus substantially lower than the melting temperature of the pure alkali titanium fluoride, which is, for example Na ₂ TiF ₆ at about 87O ⁰ C. A current yield of between 90 and 95%, based on monovalent titanium, is achieved. Instead of the heat-treated addition compound as an additive, the addition compound that is not subjected to a heat treatment can also be used with the same success. In this case, however, the added amounts have to be increased by about so much in accordance with the lower titanium content of the untreated addition compound that the same titanium content is again contained in the additive. The amounts to be added are between about 1 and 10%, preferably about 3% - Without the addition of either the heat-treated or the non-heat-treated addition compound, no metal is deposited under the same stress conditions, even if the temperature is above the melting point the molten salt is increased. After a few hours of electrolysis, the current drops. By adding new additives, it quickly rises back to its old height. You can continue the electrolysis in this way until the electrolyte is completely used up.

In the usual and known igneous electrolysis aluminum production is the melt from about 10% aluminum oxide Al ₂ O ₃ and about 90 ° / ₀ of an alkali aluminum fluoride, preferably Na ₃ AlF. ₆ This melt-flow electrolysis is operated at a voltage between 5 and 6 V and a temperature of approximately 950 ^° C. and results in a current yield of approximately 95%.

When using an additive according to the method according to the invention in the form of an ammonia addition compound on aluminum trichloride or a product made from this addition compound by means of heat treatment in an amount that, when using the heat-treated product, is between fractions of a percent to a few percent, preferably about 1% by weight , and when using the addition compound is about three times the amount, preferably about 3% by weight, there is a significant increase in the conductivity of the electrolyte and a lowering of the melting temperature of the melt by about 150 ^° C. to about 800 ^° C. Maintaining this temperature of the melt only a voltage of about 1V is necessary due to the significant increase in the conductivity of the electrolyte. At this voltage, roughly the same current flows as in the case where the fused-salt electrolysis is operated at a voltage between 5 and 6 V without such additives. Furthermore, this fused flux electrolysis with additives results in a current yield of around 95 to 97 %.Due to the lowering of the voltage, the electrical energy previously required for the production of 1 kg aluminum in fused flux electrolysis without additives is from 17 to 20 kWh to 3 to 4 kWh for fused flux electrolysis lowered with additives. This improvement is quite considerable in that a large part of the production costs of aluminum is at the expense of the electrical energy used for the fused salt electrolysis

The method according to the invention is in the case of the fused-flow electrolytic Manufacture of almost all metals is applicable and specifically refers to the manufacture of the metals that are capable of being Halides, occasionally also as nitrates, chlorates and perchlorates with ammonia or hydrazine addition compounds enter, because to carry out the method according to the invention existing or produced from such addition compounds Additives are required. These addition compounds, especially ammonia addition compounds of metal halides, are largely unstable to air and moisture. Some of the halides are solid and air-resistant. This is particularly true of halides of groups I and II as well as VI to VIII of the Periodic Table of the Elements. Lie in the middle apart from the group of metalloids (Si, Ge, Sn), that of light metals and so-called transition metals. For these groups is the inventive Method particularly suitable. It particularly concerns the manufacture of titanium and aluminum. With Advantageously, the inventive method can also be used in the production of other metals, such as Use zirconium, hafnium, thorium, niobium, vanadium, boron and tin, or even such metals, whose halides are hygroscopic, as of magnesium, beryllium and the alkaline earth metals, or on those metals whose halides are resistant to air, such as cerium, lanthanum and of other rare earth metals and molybdenum.

Claims (9)

Patent claims: 1. Process for the production of metals, in particular titanium and aluminum, by Fused metal electrolysis in an electrolyte, the alkali halide and halide of the to be recovered Contains metal, characterized that the electrolyte in proportionally small amounts, preferably between 0.2 to 5 percent by weight, one or more additives are added that consist of addition compounds in which nitrogen-hydrogen compounds or their complex compounds with metal salts of the group of halides, nitrates, Nitrites, chlorates and perchlorates are deposited, consist or consist of these after heat treatment were obtained in an oxygen-free protective gas atmosphere. ' 2. The method according to claim 1, characterized in that one of such as an additive Addition compound existing or product obtained therefrom is used, in the case of a molecule of the metal salt is the smallest possible Number of molecules of the additive is attached. 3. The method according to claim 1 or 2, characterized in that when using the addition compound as an additive, this is supplied to the electrolyte in the absence of air or in an oxygen-free protective gas atmosphere will. 4. The method according to any one of claims 1 to 3 for the production of titanium by melt flow ίο electrolysis in an electrolyte containing alkali titanium fluoride, characterized in that a an electrolyte consisting essentially of sodium titanium fluoride and an additive an ammonia addition compound to a titanium halide, preferably titanium chloride, existing or a product obtained therefrom is used. 5. The method according to any one of claims 1 to 3 for the production of aluminum by melting ao flow electrolysis in an electrolyte consisting essentially of alkali aluminum chloride, characterized in that an additive consisting of an ammonia addition compound is used as an additive Aluminum chloride consisting or obtained product is used. 6. The method according to any one of claims 1 to 3 for the production of aluminum by molten electrolysis m an essentially of alkali aluminum halide and up to about 10% Aluminum oxide existing electrolytes, characterized in that as an additive from an ammonia addition compound to an aluminum halide, preferably to aluminum chloride, existing or derived product is used. 7. The method according to any one of claims 1 to 3, characterized in that an additive from an addition compound to a salt of a metal other than the one to be recovered existing or derived product is used. 8. The method according to any one of claims 1 to 7, characterized in that as an additive from an attachment compound after one to the completion of the deposition of substances the product obtained by the addition compound is used. 9. The method according to any one of claims 1 to 8, characterized in that as an additive from an attachment compound after one carried out in a flowing protective gas atmosphere Heat treatment obtained product is used. Considered publications:
"Reports of the German Chemical Society", (1928). Pp. 1569/1570. $ 09 579/318 6.65 © Bundesdruckerei Berlin