BACKGROUND OF THE INVENTION
This invention grows out of previous patents assigned to APPLIED ALUMINUM RESEARCH CORPORATION, which patents disclosed novel processes for producing essentially elemental aluminum from clay, bauxite, or other aluminous materials. In basic form, the AAR process consists of four basic steps:
I. carbo-chlorination of aluminous material to form aluminum trichloride;
Ii. reduction of the aluminum trichloride with manganese to form elemental aluminum and manganese dichloride;
Iii. oxidation of manganese chloride to give one or more forms of manganese oxide and chlorous gases; and
Iv. reduction of manganese oxides to form manganese metal.
These steps, in combination or separately, can be carried out in a variety of ways, as described in U.S. Pats. Nos. 3,615,359 and 3,615,360 and U.S. patent applications Ser. Nos. 858,011, 861,981, 889,402 now U.S. Pat. No. 3,677,742 and Ser. No. 138,663 now U.S. Pat. No. 3,713,811. These disclosures teach Step II as being carried out with gaseous aluminum chloride and molten manganese at temperatures of approximately 900°-1500°C and pressures up to 70 atmospheres.
Other known processes were reviewed wherein metal chlorides were reduced by a reductant metal, a prime example being the KROLL process which is used for current titanium production. Briefly, TiCl4 is reduced with molten magnesium or sodium. The metal halide by-product (MgCl2 or NaCl) is subsequently electrolytically reduced to the elemental metal (magnesium or sodium) and the titanium sponge product resulting from the reduction is removed, crushed, leached of salt, and dried to give high purity titanium sponge. The reduction is carried out at elevated temperatures (712°-920°C) to assure that the reductant sodium or magnesium and product chlorides are molten.
In the direct thermochemical reductions noted above, it will be noted that the reductant metal is always molten thereby necessitating a high temperature reaction coupled with all of the inherent expensive apparatus and energy requirements.
SUMMARY OF THE INVENTION
The instant invention discloses the novel idea that the reductant metal and chloride product can be solid rather than molten resulting in all of the consequential economic advantages.
The primary object of the present invention is to produce a metal by direct reduction of a chloride of that metal by a reductant metal which is in the solid state during the reaction.
It is another important object of the present invention to produce aluminum by reducing AlCl3 in either liquid or gaseous state by manganese in solid state.
It is still another important object of the present invention to produce titanium by reducing TiCl4 in either liquid or gaseous state by manganese or magnesium or aluminum in solid state.
A still further important object of the present invention is to produce silicon by reducing SiCl4 in either liquid or gaseous state by manganese or aluminum in solid state.
These and other important objects and advantages of the present invention will become more apparent after reading the following description, appended claims and drawings. It is to be understood that the word "fluid" as used in this disclosure, means either gaseous or liquid state. Furthermore the word "powder" encompasses particles, granules, grains or other types and sizes of discrete particles.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows in diagrammatic form an apparatus for carrying out the invention when the metal chloride is gaseous;
FIG. 2 shows in diagrammatic form an apparatus for carrying out the invention in a batch process when the metal chloride is liquid;
FIG. 3 shows in diagrammatic form a further apparatus for carrying out the invention in a batch process when the metal chloride is liquid;
FIG. 4 shows in diagrammatic form an apparatus for carrying out the invention in a continuous process when the metal chloride is liquid.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The instant invention has extremely broad applicability. Generally, the scope of the invention deals with reacting a fluid metal chloride with a solid reductant powder. The most important criteria is that the reductant metal powder is in solid form and the metal chloride be in fluid form at the temperature and pressure that the process is carried out at.
Table I shows the various melting points (M.P.) and boiling points (B.P.) of various metals and their chlorides as well as their free energies at 298°K, 500°K and 700°K. From this Table, one skilled in the art can deduct the operating parameters for carrying out the instant inventive process.
Furthermore, it is possible to develop a list of chloride affinities from the free energy data given in Table I. Such a list can be used to readily determine which metal can serve as a reductant for a particular metal chloride. A partial list of chloride affinities at 298°K has been developed and is given in Table II. This Table was generated by considering the free energies of formation of each particular metallic chloride at 298°K. For a given metal chloride, any
TABLE I __________________________________________________________________________ Properties of Metals and Metal Chlorides* Metal ΔF°f, Kcal/gmole Metal M.P.,°K B.P.,°K Chloride M.P.,°K B.P.,°K 298°K 500°K 700°K __________________________________________________________________________ Aluminum(Al) 931.7 2600 AlCl3 465.6 720 -153.0 -144.5 -138.6 Beryllium (Be) 1556 3243 BeCl2 678 (820) (-102.9) (- 96.6) Calcium (Ca) 1124 1760 CaCl2 1055 (2300) -179.65 -172.5 -165.75 Cobalt (Co) 1763 3373 CoCl2 997 1323 - 67.43 - 60.65 - 54.55 Copper (Cu) 1357 2855 CuCl 703 1963 - 28.5 - 25.8 - 23.6 Iron (Fe) Fecl2 950 1299 - 81.9 - 72.6 1803 3008 FeCl3 577 592 - 79.5 - 68.8 Lead (Pb) 600.5 2024 PbCl2 771 1227 - 75.06 - 67.9 - 61.1 Lithium (Li) 453.7 1604 LiCl 887 1653 - 92.5 - 89.2 - 85.6 Magnesium (Mg) 923 1393 MgCl2 987 1691 -141.4 -133.5 -126.1 Manganese (Mn) 1517 2368 MnCl2 923 1463 -105.1 - 98.85 - 95.85 Nickel (Ni) 1725 3073 NiCl2 1303 -- - 61.9 - 54.5 - 47.5 Potassium (K) 336.7 1030 KCl 1043 1680 - 97.55 - 92.8 - 88.2 Silicon (Si) 1683 (2950) SiCl4 205 330 -132.7 Sodium (Na) 371 1162 NaCl 1073 1738 - 91.9 - 87.5 - 82.85 Tin (Sn) SnCl2 500 925 (- 71.6) (- 65.6) 505 2960 SnCl4 240 386 (- 16.9) Titanium (Ti) 1998 3550 TiCl4 250 409 -175.9 -167.45 -161.60 Zinc (Zn) 692.7 1181 ZnCl2 556 1005 - 88.45 (- 81.1) __________________________________________________________________________ *C. E. Wicks and F. E. Block, "Thermodynamic Properties of 65 Elements - Their Oxides, Halides, Carbides, and Nitrides", Bulletin 605, U.S. Bureau of Mines, 1963.
TABLE II ______________________________________ List of Chloride Affinities of Metals at 298°K* ______________________________________ K Highest Chloride Affinity Li Na Ca Mg Mn Be Al Zn Ti Fe (to give FeCl2) Sn (to give SnCl2) Co Si Ni Cu Fe (to give FeCl3) Sn (to give SnCl4) Lowest Chloride Affinity ______________________________________ *Some reordering is expected at other temperatures.
metal above it in the Table (that metal existing as the chloride) can serve as a reductant for the metal chloride. Specific examples will be discussed further on.
AlCl3 AND MANGANESE
Step II of the AAR process, discussed in the Background of the Disclosure, is dramatically improved by the instant inventive process. Fluid aluminum chloride is reacted with powdered (solid) manganese at low temperature (180°-640°C) and pressure (1-30 atm). The basic chemical reaction is:
3Mn(s) + 2AlCl3 (g,l) = 3MnCl2 (s,soln.) + 2Al(s)
Under conditions indicated above, manganese and aluminum exist in the solid form, and aluminum trichloride exists as a gas or liquid, depending on the combination of temperature and pressure. Manganese dichloride exists either in solid form or dissolved in excess liquid aluminum trichloride. Further, chemical complexes between manganese dichloride and aluminum trichloride occur under certain conditions; these substantially increase the ratio of Mn to Al in the gas phase.
Thermodynamics demonstrates that chemical equilibrium for the above reaction is favored toward the right under the indicated conditions. For example, for the reaction with the components in the following forms:
3Mn(s) + 2AlCl3 (l) = 3MnCl2 (s) + 2Al(s)
the free energy of the above reaction at 500° and 600°K is approximately -18.3 Kcal and -16.6 Kcal, respectively. The equilibrium constants at 500° and 600°K are thus approximately 1.0 × 108 and 1.1 × 106, respectively, indicating that the reaction goes virtually to completion.
The advantages of operating at these low temperatures (below the melting point of aluminum) are several fold. For example, less expensive materials of construction can be employed and corrosion problems are minimized; heat exchange requirements for reactants is lessened and costs are thereby reduced; aluminum and manganese, which exist as pure or comingled solid particles can be handled easily and readily contacted with gas or liquid aluminum chloride in any of several conventional forms of apparatus.
Experimental data have demonstrated that the above reaction does in fact proceed under the indicated conditions. The following two examples summarize some corroborating experimental data for conditions under which aluminum trichloride exists as a gas and as a liquid (at and below 600°C).
Turning now to FIG. 1 which diagrammatically shows a low temperature gaseous AlCl3 apparatus, a reactor 26 and AlCl3 generator 22 are integrated in one horizontal 3/4 inch alumina tube 19. Each section of the tube 19 is separated by pyrex wool 28 and an 8-inch void space 24. The AlCl3 generator section 22 contains a 4-inch long bed of aluminum pellets, and the reactor section 26 contains a 1/2-inch long bed of 5 grams of manganese. The condenser 32 is a 2-inch diameter mild steel pipe 5 inches long which is connected to the ceramic tube with a packing gland 30 and has a conduit 34 and valve 36 for venting any gases. The reactor and generator sections of the tube are heated separately with resistance wire 20.
Chlorine vapor from source 10 is passed via conduit 12 through a rotometer 14 to measure the flow rate which is controlled by valve 16 and is passed through conduit 18 into the aluminum pellets in generator 22 to generate AlCl3 at 300°C. The AlCl3 then passes through the bed of Mn in reactor 26 which ranges in particle-size from 45 to 300 microns (all on 325 mesh). The particle size of the Mn was chosen for a size distribution of high surface area to ensure good gas-solid contact. Runs were typically made for 2 hours with 5 grams of Mn at 300° to 600°C and an AlCl3 flow rate or 3 grams/hour with the following results:
TABLE III ______________________________________ LOW TEMPERATURE GAS AlCl3 APPARATUS (PRESSURE = 15 psia) CHARGE DISCHARGE TEMP. AlCl3 FLOW TIME (% Mn) (% Al) (°C) RATE (gms/hr.) (hr.) ______________________________________ 100 0.1 600 0.75 2.0 100 0.7 400 0.69 2.0 100 2.7 400 3.20 2.0 100 3.9 300 2.60 2.0 ______________________________________
The process could be carried out in conventional gas-solid reactors and combinations thereof. The MnCl2 could be removed from the aluminum product by vaporization as an MnCl2 -AlCl3 gas complex or by dissolving in liquid AlCl3 or another solvent. The reaction could be stopped at any degree of Al production and the aluminum then produced separated from the Mn by means such as aluminum subhalide distillation, zinc extraction, zone freezing, or differential vaporization.
It is obvious that these gas phase AlCl3 reactions that have been demonstrated can be optimized (in reaction rate and completion) by high pressure and changes in other variables such as smaller particle-size, more time of exposure, higher gas velocity as in transport or cyclone reactors, or temperatures.
A simplified diagram of a low-temperature liquid AlCl3 laboratory apparatus is shown in FIG. 2. A batch reactor 40 is designed to effectively contact Mn metal granules with liquid AlCl3 in a continuously agitated vessel. The apparatus is designed to operate for various lengths of time at 180°-600°C and 14.7-450 psia, with approximately 30-60 grams Mn and 120-450 grams AlCl3 charge.
The reactor 40 contains a 2 1/2-inch diameter alumina tube 58 which is housed in a 3-inch diameter stainless steel pipe 60 and heated externally by resistance wires 62. A stainless-steel stirrer 56 and shaft 54 along with a motor 50 is mounted in place on the top flange 46 with a packing gland 48. The charge is introduced through conduit 44. A pressure gauge 52 is mounted on conduit 42. Following the reaction period, the unreacted AlCl3 is boiled off through conduit 64, valve 66, into condenser 68 which is vented by conduit 70 and valve 72.
Exemplary results are as follows:
TABLE IV ______________________________________ LOW TEMPERATURE LIQUID AlCl3 APPARATUS Temp. Mn Particle AlCl3 Time Discharge °C Charge Size Charge Hrs. % Al gms. (Mesh) gms ______________________________________ 200 60 300/325 120 1.5 8.0 250 60 200/325 120 1.5 18.0 300 60 200/325 168 1.5 30.0 350 60 200/325 188 1.5 55.0 400 30 200/325 450 2.0 66.0 450 30 200/325 450 4.0 71.0 350 30 8/14 300 3.5 80.0 ______________________________________
It is noteworthy that not only very favorable equilibrium constants and thermodynamics for completion of the reaction exist for the reaction between liquid AlCl3 and solid Mn but also that the kinetics are unexpectedly rapid, especially for what would be ordinarily considered as a slow metal-thru-metal diffusion limitation. The causes for this rapidity of reaction could be unexpectedly intricate and are not known at this time but the following is conjectured. Firstly, the dissolving of the MnCl2 into the moving liquid AlCl3 stream removes a product of reaction from the immediate vicinity of the reaction surface. Secondly, the liquid AlCl3 serves as a solvent to dissolve the solid MnCl2 that is formed at the reaction interface along with the aluminum, thus resulting in a porous aluminum microstructure, through which liquid AlCl3 gains ready access to the unreacted manganese within. Thirdly, another phenomenon might unexpectedly make for porosity, namely, the volume of the MnCl2 and aluminum products would greatly exceed that of the substrate dense manganese so that a tendency would exist for the film of solid reaction products or of the porous aluminum to expand away from the manganese and to thereby add to the porosity.
Another important benefit of the liquid AlCl3 reaction lies in the increase in boiling point of the AlCl3 -MnCl2 liquor as the reaction proceeds due to increased concentration of MnCl2. This permits use of beneficial higher temperatures for the reaction up to 600°C instead of being limited by about 352.5°C, the critical temperature of pure AlCl3. This increased temperature factor thus can be used to readily compensate for any decreasing AlCl3 concentration due to increase of MnCl2 content as the reaction progresses. Additional MnCl2 or other soluble metal salts, could be added as needed to establish optimum conditions.
An advantage of the liquid AlCl3 process lies in the ease of separation of the products formed.
Firstly, as Mn particles are replaced with Al, the density decreases from about 7.4g/ml for Mn to 2.7g/ml for Al. Hence, the finished product can be readily separated by utilization of the vast difference in density. For instance, the product could be carried out of a continuous reactor in the liquor stream at appropriate velocity leaving Mn-containing particles behind; or conventional gravity separation devices could be employed, with recycling of the Mn-containing particles. Alternatively, all the manganese could be replaced with aluminum in the reactor or series of reactors to obviate the need for separation of the aluminum from an intermediate.
The product aluminum can be cleansed of adherent MnCl2 by a wash of fresh liquid AlCl3 in which the MnCl2 is soluble in AlCl3 to 50% by weight MnCl2, the two salts can be readily separated by crystallization, sublimation or by evaporation of the AlCl3. Water or organic solvents can also be used to remove any residual MnCl2 or AlCl3.
The AlCl3 which is left on the surface of the aluminum can be removed readily by sublimation or evaporation. The MnCl2 can be removed from AlCl3 liquor by evaporating the latter with its 180°C atmospheric boiling point versus 1190°C for the boiling point of MnCl2 ; or the MnCl2 can be crystallized out of a hot concentrated solution of MnCl2 and AlCl3 by reducing the temperature. The AlCl3, after removal of the MnCl2, can be reused.
An unexpected advantage of the reaction with liquid AlCl3 is the formation of the aluminum over the surface of the manganese metal in a manner that does not block reaction. This affords the opportunity of cutting short the reaction at any desired time and still being able to readily separate and recover the aluminum. The temperature of the aluminum metal can be brought slightly over its melting point to cause the aluminum to flow from the particles and be collected, leaving the residue of manganese metal with a slight film of high melting point manganesealuminum alloy at the interface. The manganese residue is returned to the reactor or if the particle size is very small, it can be agglomorated first.
Agitation of an abrasive or impact nature can cause the aluminum coating to separate for collection. Furthermore, more unreacted manganese will be exposed. The aluminum can be separated from the manganese by conventional methods such as subhalide or zinc extraction.
This particular aspect of the invention may be practiced in many forms. Firstly, it is amenable to many conventional solid-liquid contactors, reactors and flow arrangements such as fluid, static and moving bed reactors, batch reactors, and cyclone and tube transport reactors, all in concurrent, countercurrent, semi-continuous or batch arrangements. Agitation may be performed by stirrers, flow or recirculation of slurry, vibrators, shakers, or the recycling of an inert gas or liquid AlCl3, rotating or tumbling drums with or without flights, grinding balls, or other obvious means.
The following two examples set forth illustrative apparatus which could be used for commercial production.
FIG. 3 is a schematic diagram illustrating an apparatus for performing the process of the present invention in a batch-wise manner. The process uses a non-corrosive metal or ceramic lined steel reactor 80 having heating means such as electric heating coils 82 for control of the temperature necessary to maintain the AlCl3 in a liquid state and provide other heat demands. The reactor is charged with AlCl3 and manganese from the top through charge and discharge port 84. Generally, an excess of AlCl3 will be present to keep the reactants in the form of a solid-liquid slurry. The reactor is sealed and heated to reaction temperature. At temperature (180°-600°C), the AlCl3 is liquid and exhibits a vapor pressure of 15-450 psia depending on the exact reactor temperature and composition of the liquor. The mixture of reactants is maintained at temperature and pressure until all of the manganese has been consumed to form aluminum metal and MnCl2. The mixture is mechanically stirred by a blade 88 attached to a shaft 86, powered by a motor (not shown) to enhance contact and reduce reaction time. After reaction, any excess AlCl3 is removed by opening the reactor and bleeding off the AlCl3 as a gas through conduit 90 and valve 92. Removal can be enhanced by pulling a vacuum on the reactor and/or by increasing the temperature. The aluminum and MnCl2 are discharged as solids and subsequently separated by means such as melting, vaporization, or solvent extraction.
An apparatus for performing the process of the present invention in a continuous manner is illustrated in FIG. 4. The process uses a corrosion-resistant or ceramic-lined steel counter-current reaction tower 100 having heating means 102 for maintaining the AlCl3 -MnCl2 solution in the liquid state at from 180°-600°C and 15-450 psia. Granular solid manganese is continuously introduced from the top at input port 104 and AlCl3 is continuously introduced from the bottom at input port 106 in the counter-current reactor. The solid aluminum product is continuously removed from the bottom at 110 and the MnCl2 from the top at 108 and/or bottom at 110, depending on the extent to which it dissolves in the AlCl3.
TiCl4 AND MAGNESIUM
Liquid TiCl4 can be reduced by solid powdered magnesium. In such a process, powdered magnesium and TiCl 4 can be simultaneously charged into a reactor as above discussed, heated to 200°-650°C at a pressure from 0-676 psia and reacted to give titanium metal comixed, adhering to, or alloyed with unreacted magnesium, if any, and MgCl2. Under these conditions, magnesium is solid, titanium is solid, MgCl2 in pure form is solid, and TiCl4 is liquid if the total pressure is above the vapor pressure of TiCl4 (critical temperatures = 365°C).
In addition as can be seen from data from Table I, which lists properties of some metals and metal chlorides, the thermodynamics of this reaction is favorable. For example, at 500°K the thermodynamics show the reduction reaction to be quite favorable:
2 Mg (s) + TiCl4 (l) = 2 MgCl2 (s) + Ti(s) ΔGf = - 99.55kcal.
TiCl4 AND MANGANESE
Liquid or gaseous TiCl4 can be reduced by solid powdered manganese in accordance with:
TiCl4 (l,g) + 2Mn(s) = Ti(s) + 2MnCl2 (s-4. The temperature range over which the reaction is favorable is from -30°C (the melting point of TiCl4) to about 1600°C realizing that above about 1175°C some of the manganese will be in liquid phase due to a Ti-Mn eutectic of that melting point. The preferred pressure range is from 0-676 psia. The critical point of TiCl4 is 365°C and 46 atmospheres; however, at high termperatures, vapor pressure lowering due to the presence of other inert metal salts such as NaCl, CaCl2, KCL, MgCl2, BaCl2, etc. allows TiCl4 to remain in the liquid state. In addition, the reaction proceeds favorably with TiCl4 in the gaseous state. Typical experimental results are shown in EXAMPLE V.
SiCl4 AND MANGANESE
Liquid or gaseous SiCl4 can be reduced by solid powdered manganese in accordance with:
SiCl4 (l,g) + 2Mn(s) ➝ Si(s) + 2MnCl2 (s,l).
The temperature range over which the reaction is favorable is from -70°C (the melting point of SiCl4) to about 1600°C realizing that above about 1040°C some of the manganese will be in liquid phase due to a Si-Mn eutectic of that melting point. The critical point of SiCl4 is 234°C and 37 atmospheres. Above the critical temperature the SiCl4 will be a vapor unless a suitable inert metal salt such as NaCl, CaCl2, KCl, MgCl2, BaCl2, etc. allows SiCl4 to remain in the liquid state. In addition, the reaction proceeds favorably in the gaseous state.
SiCl4 AND ALUMINUM
Liquid or gaseous SiCl4 can also be reduced by solid powdered aluminum in accordance with:
3SiCl4 (l,g) + 4Al(s) ➝ 3Si(s) + 4AlCl3 (l,g).
The temperature range over which the reaction is favorable is from -70°C (the melting point of SiCl4) to about 577°C realizing that above about 577°C the aluminum will be in the liquid phase due to a Si-Al eutectic of that melting point. Above 234°C (the critical temperature of SiCl4) SiCl4 will be a vapor unless a suitable inert metallic salt such as NaCl, CaCl2, KCl, MgCl2, BaCl2, etc. allows the SiCl4 to remain in the liquid state.
The following typical experimental results obtained from the apparatus shown in FIG. 2 demonstrate the production of Ti and Si metals from their respective chlorides. In one case the reactor was charged with 60 grams of -100, +200 mesh electrolytic manganese and 410 grams of reagent grade TiCl4. The reactor was heated to 336°C for 3 hours while agitating with a paddle shaped stirrer at 300 rpm under a TiCl4 vapor pressure of 425-443 psig. After 3 hours the TiCl4 was bled from the reactor into a condenser. The hot reactor was then purged with argon and cooled to room temperature. The solid residue in the reactor was removed and analyzed for titanium metal. A total of 3.18 grams of titanium metal was found.
In similar experiment, the reactor was charged with 60 grams of -100, +200 mesh aluminum powder and 695 grams of reagent grade SiCl4. The reactor was heated to 200°C for 3 hours while agitating at 1200 rpm with a turbine shaped stirrer under a SiCl4 vapor pressure of 388 psia. After 3 hours the SiCl4 was bled from the reactor into a condenser. The reactor was cooled to room temperature at which time the solid residue was removed and analyzed for silicon metal. A total of 2.13 grams of silicon metal was found.
TiCl4 AND ALUMINUM
The free energies of reaction per mole of Ti formed are Δ G500 = -21.6Kcal and Δ G700 = -23.2Kcal as calculated from the following stoichiometric reaction:
3TiCl4 + 4Al ⇋ 4AlCl3 + 3Ti.
The free energies of reaction using manganese as the reductant are Δ G500 = -29.25Kcal and Δ G700 = 30.10Kcal per mole of Ti formed as calculated from the following stoichiometric reaction:
TiCl4 + 2Mn ⇋ 2MnCl2 + Ti.
As can be seen the free energies for the two reductants are essentially the same. Therefore on the face of it there would seem to be no advantage in using aluminum as the reductant. However, looking at the physical properties of Al and AlCl3 the following advantages come to light:
1. Although neither AlCl3 or MnCl2 are appreciably soluble in TiCl4, the AlCl3 would be liquid at reaction temperatures (200°-400°C) and would therefore be removed from the metal surface.
2. If coating of titanium metal on the surface was the limit of the reaction, the material could be melted and sold as such since there is a market for Al-Ti alloys containing high percentages of Al.
3. The by-product of the reaction (AlCl3) would be easier to remove than MnCl2 and could be used again in the basic reaction with Mn.
4. If accumulation of by-product is a problem, the AlCl3 can be continuously removed by throttling TiCl4 into and out of the system carrying AlCl3 with it. The MnCl2 produced by reaction of TiCl4 with Mn cannot be removed so easily on a continuous basis.
5. To produce 100 lb. of titanium it would require conversion of 75 lb. of Al and 230 lb. of Mn. The addition of inert metallic salts of low volatility, especially metal halides, are beneficial in carrying out the reactions above described. The inert metallic salts are used to lower the vapor pressure of the metal chloride, e.g. AlCl3, TiCl4, SiCl4, so that a higher temperature can be reached in the closed reactor at a given pressure.
Turning, as an example, to the AlCl3 -Mn reaction, experimental data has shown that the total pressure in the reactor will lower as the reaction proceeds as a result of the formation of MnCl2, and therefore it may well be unnecessary to add other inert metallic salts to the system. However, under certain conditions, it may well prove desirable to carry out the reaction at elevated temperatures with an excess of AlCl3, and the amount of AlCl3 vapor pressure lowering as a result of forming MnCl2 may not be sufficient to operate at the desired temperature and total pressure. In this case, an addition of one or more additional inert metallic salts may be highly desirable. Examples of such salts are NaCl, CaCl2, KCl, MgCl2, BaCl2, etc.
Although the invention has been described and illustrated in detail with respect to chlorides, it is to be understood that this does not delimit the invention but rather the process is applicable to fluorides, bromides and iodides as well. The halides react similarly under like conditions. The spirit and scope being limited only by the language of the appended claims.