METHOD FOR METAL PRODUCTION

Abstract

This invention relates to a method for the production of reducible metal oxides (e.g. V.sub.2O.sub.3). The invention also relates to a method for the production of metals (e.g. vanadium) from said oxides. More specifically, the method facilitates the preparation of metal oxides that are capable of being further reduced to their respective metals with high purity.

Claims

1. A method for the production of a partially reduced metal oxide, said method comprising the steps of: (a) mixing an oxide of a metal in a receptacle with a first reducing agent comprising a Group II metal or a hydride thereof, wherein the oxide of the metal and the reducing agent are present in a first mass ratio; and (b) heating the mixture of the oxide of the metal and the first reducing agent to produce a partially reduced metal oxide; wherein the partially reduced metal oxide is suitable for further reduction to form a metal.

2. The method of claim 1, wherein the metal is selected from a transition metal, a rare earth metal, and aluminium.

3. The method of claim 1, wherein the metal is selected from vanadium, titanium, tantalum, niobium, hafnium, zirconium, and aluminium.

4. The method of claim 1, wherein the metal is vanadium and the oxide of the metal is vanadium pentoxide.

5. The method of claim 1, wherein the metal oxide used in step (a) is a mixture of different metal oxides.

6. The method of claim 1, wherein the first reducing agent is selected from calcium, magnesium, calcium hydride, and magnesium hydride.

7. The method of claim 1, wherein the first reducing agent is calcium.

8. The method of claim 1, wherein the mass ratio of metal oxide to first reducing agent is in the range of from 1:0.5 to 1:1.5.

9. The method of claim 1, further comprising the step of washing the product of step (b) with an acid.

10. A method for the production of a metal, said method comprising the steps of: (c) mixing the partially reduced metal oxide formed in step (b) of claim 1, with a second reducing agent comprising a Group II metal or a hydride thereof, wherein the partially reduced metal oxide and the second reducing agent are present in a second mass ratio; and (d) heating the mixture of the partially reduced metal oxide and second reducing agent to form the metal.

11. The method of claim 10, wherein the second reducing agent is selected from calcium, magnesium, calcium hydride, and magnesium hydride.

12. The method of claim 10, wherein step (c) further comprises the step of mixing the product of step (b) and the second reducing agent with one or more additional metals and/or metal oxides.

13. The method of claim 12, wherein the one or more additional metals or metal oxides is selected from aluminium, titanium, molybdenum, zirconium, tin, silicon, niobium, iron, and chromium, or an oxide thereof.

14. The method of claim 10, wherein the mass ratio of partially reduced metal oxide to second reducing agent is in the range of from 1:1 to 1:5.

15. The method of claim 10, further comprising the step of washing the product of step (d) with an acid.

16. The method of claim 10, further comprising the step of melting the washed metal or alloy product of step (d) and casting the molten metal or alloy in to a desired shape/form.

17. The method of claim 10, wherein the washed metal or alloy product of step (d) is subject to an electron beam remelting step.

18. The method of claim 10, wherein the washed metal or alloy product of step (d) is subjected to a gas atomisation step.

19. A partially reduced metal oxide obtainable by the method of claim 1.

20. A metal or metal alloy obtainable by the method of claim 10.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:

[0089] FIG. 1 shows the XRD spectrum for the samples obtained by the method described in Example 1.

[0090] FIG. 2 shows the XRD spectrum for the samples obtained by the method described in Example 1.

[0091] FIG. 3 shows the XRD spectra for the samples obtained by the method described in Comparative Examples 1 and 2.

[0092] FIG. 4 shows the XRD spectra for the samples obtained by the method described in Comparative Examples 3 and 4.

[0093] FIG. 5 depicts a flow diagram detailing a typical method for producing partially reduced vanadium oxides according to the first aspect (stage 1) and for producing metal or vanadium-titanium alloy, according to the second aspect (stage 2).

DETAILED DESCRIPTION

[0094] The terms metal oxide and oxide of the metal are used interchangeably throughout this specification.

[0095] The term partially reduced metal oxide, as used throughout this specification, may refers to a metal oxide formed in a process of the invention, in which the metal is in a lower oxidation state than in the metal oxide starting material. Certain such oxides are capable of being further reduced to a metal under any of the conditions described with respect to the second aspect. The term partially reduced metal oxide may refer to a metal oxide comprising cations of only one metallic element.

[0096] The term complex metal oxide may refer to a metal oxide that is unable to be reduced to metal under metallothermic reduction conditions. The term complex metal oxide, as used throughout this specification, may refer to a metal oxide that is unable to be reduced to a metal under any of the conditions described with respect to the second aspect. The term complex metal oxide may refer to a metal oxide that comprises more than one metal.

[0097] The term non-reducible metal oxide, as used throughout this specification, refers to a metal oxide that is not able to be reduced to a metal under any of the conditions described with respect to the first and/or second aspect. The non-reducible metal oxide may be a metal oxide comprising cations of only one metallic element, or it may be a complex metal oxide, as defined herein.

[0098] It is to be understood that the term metal, as used throughout this specification, may be considered to encompass semi-metals. For example, the term metal may be considered to encompass silicon. The term metal may also be understood to refer only to metals. Thus, the term metal may exclude semi-metals, such as silicon. In these embodiments, the term metal may only refer to transition metals and rare earth metals.

[0099] The present invention provides a method for the production of a reducible partially reduced metal oxide, as defined herein. The present invention also provides a method for the production of a metal or metal alloy, as defined herein. The process is particularly suited to the production of metals from metal oxides that are susceptible to forming non-reducible metal oxides that are not easily further reduced to their respective metal.

Methods and Examples

Methods

X-ray Diffraction (XRD)

[0100] X-ray diffractometry was performed with Cu K radiation (XRD, Bruker D8 AXS Advance X-ray diffractometer with linxeye detector). The PXRD run in Braggs-Brentano with a copper source operating at a wavelength of 0.15406 nm, voltage of 40 kV and a filament emission of 30 mA.

Scanning Electron MicroscopyEnergy Dispersive X-Ray (SEM-EDX)

[0101] SEM-EDX analysis was performed utilising an Oxford Xplore 30 detector with the AZtec Live Software suite. The SEM-EDX was typically operated under high vacuum (1E-4 Torr); at an accelerating voltage of 20 kV using tungsten filament, and magnifications between 10x-600x, with the samples carbon coated prior to analysis.

EXAMPLES

Example 1

[0102] 5 g of vanadium pentoxide (V.sub.2O.sub.5) was mixed with 3.81 g of calcium. The resultant mixture was heated to 900 C. for 5 hours at 10.sup.3 mbar. The resultant mixture was cooled and washed with distilled water and diluted hydrochloric acid solution (0.05M). The washed product was then dried and analysed using SEM-EDX, the results of which are shown in Table 1.

TABLE-US-00001 TABLE 1 Element (% Weight) Sample V O Ca Al Si P Cl Br Sample 15 65.98 17.80 16.08 0.04 0.01 0.01 0.07 0.02

[0103] The XRD spectrum of FIG. 1 shows that the product of the process described in Example 1, i.e. a process according to the first aspect, includes V.sub.2O.sub.3 and CaV.sub.2O.sub.4.

Example 2

[0104] The partially reduced metal oxides obtained according to Example 1 were mixed with 4 g of calcium. The resultant mixture was heated to 900 C. for 5 hours at 10.sup.3 mbar. The resultant mixture was cooled and washed with distilled water and diluted hydrochloric acid solution (0.4M). The washed product was then dried and analysed using SEM-EDX, the results of which are shown in Table 2.

TABLE-US-00002 TABLE 2 Element (% Weight) Sample V O Ca Al Si S Cl Sample 19 91.31 6.80 1.80 0.01 0.02 0.01 0.04

[0105] The XRD spectrum of FIG. 2 shows indicated that the product of the process described in Example 2, i.e. a process according to the second aspect of the invention, includes pure vanadium metal and a small amount (approximately 15-20 wt %) of vanadium oxide (VO).

Comparative Example 1

[0106] 2.5 g of vanadium pentoxide (V.sub.2O.sub.5) was mixed with 5 g of calcium. The resultant mixture was heated to 900 C. for 7 hours at 10.sup.3 mbar. The resultant mixture was cooled and washed with distilled water and diluted hydrochloric acid solution (0.05M). The washed product was then dried and analysed using SEM-EDX, the results of which are shown in Table 3.

TABLE-US-00003 TABLE 3 Sample 9 Element (% Weight) V Al Ca O Si S 52.04 0.41 21.67 25.23 0.05 0.12 Cl Mn Ni Fe Cu Cr 0.02 0.02 0.01 0.04 0.02 0.37

[0107] It is clear from the results shown in Table 3, and in FIG. 3, that a one-step reduction process in which the mass ratio of vanadium pentoxide to calcium is 1:2 (i.e. a process of the prior art), is insufficient to result in the production of vanadium metal.

Comparative Example 2

[0108] 2.5 g of vanadium pentoxide (V.sub.2O.sub.5) was mixed with 5 g of calcium. The resultant mixture was heated to 900 C. for 10 hours at 10.sup.3 mbar. The resultant mixture was cooled and washed with distilled water and diluted hydrochloric acid solution (0.05M). The washed product was then dried and analysed using SEM-EDX, the results of which are shown in Table 4.

TABLE-US-00004 TABLE 4 Sample 11 Element (% Weight) V O Ca Al Cr Fe Ni Cu Zn Mo 67.08 15.55 16.34 0.29 0.39 0.01 0.03 0.06 0.02 0.01 Ge Os Na Si S Cl Br Yb Eu Pr 0.03 0.01 0.02 0.02 0.03 0.01 0.01 0.01 0.01 0.08

[0109] It is clear from the results shown in Table 4, and in FIG. 3, that increasing the period of time for the prior art reduction process is insufficient to fully reduce vanadium pentoxide to vanadium metal.

Comparative Example 3

[0110] 2.5 g of vanadium pentoxide (V.sub.2O.sub.5) was mixed with 5 g of calcium. The resultant mixture was heated to 1050 C. for 5 hours at 10.sup.3 mbar. The resultant mixture was cooled and washed with distilled water and diluted hydrochloric acid solution (0.05M). The washed product was then dried and analysed using SEM-EDX, the results of which are shown in Table 5.

TABLE-US-00005 TABLE 5 Sample 12 Element (% Weight) V O Ca Al Cr Fe Si S Cl 63.14 18.39 18.21 0.13 0.03 0.07 0.01 0.01 0.01

[0111] It is clear from the results shown in Table 5, and in FIG. 4, that increasing the temperature for the prior art reduction process is insufficient to fully reduce vanadium pentoxide to vanadium metal.

Comparative Example 4

[0112] 2.5 g of vanadium pentoxide (V.sub.2O.sub.5) was mixed with 5 g of calcium. The resultant mixture was heated to 1100 C. for 5 hours at 10.sup.3 mbar. The resultant mixture was cooled and washed with distilled water and diluted hydrochloric acid solution (0.05M). The washed product was then dried and analysed using SEM-EDX, the results of which are shown in Table 6.

TABLE-US-00006 TABLE 6 Sample 13 Element (% Weight) V O Ca Al Na Si S 46.75 28.96 24.14 0.10 0.01 0.01 0.02

[0113] It is clear from the results shown in Table 6, and in FIG. 4, that increasing the temperature for the prior art reduction process is insufficient to fully reduce vanadium pentoxide to vanadium metal.

[0114] Throughout the description and claims of this specification, the words comprise and contain and variations of them mean including but not limited to, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0115] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0116] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

REFERENCES

[0117] [1] Vanadium processingThe metal and its alloys, Encyclopedia Britannica, 2021. [Online]. Available: https://www.britannica.com/technology/vanadium-processing/The-metal-and-its-alloys. [Accessed: 27 Jul. 2021]. [0118] [2] R. Moskalyk and A. Alfantazi, Processing of vanadium: a review, Minerals Engineering, vol. 16, no. 9, pp. 793-805, 2003. Available: 10.1016/s0892-6875 (03) 00213-9 [Accessed 14 Feb. 2021]. [0119] [3] Y. Oka and R. Suzuki, Direct Reduction of Vanadium Oxide in the Molten Calcium Chloride, Journal of the Japan Institute of Metals, vol. 72, no. 3, pp. 181-187, 2008. Available: 10.2320/jinstmet.72.181 [Accessed 14 Feb. 2021]. [0120] [4] F. Wang, B. Xu, H. Wan, J. Yang, B. Yang and W. Jiang, Preparation of vanadium powders by calcium vapor reduction of V2O3 under vacuum, Vacuum, vol. 173, p. 109133, 2020. Available: 10.1016/j.vacuum.2019.109133 [Accessed 14 Feb. 2021].