CN112011804A - Method for preparing low-oxygen metal by fused salt electrolysis-magnesiothermic reduction of metal oxide - Google Patents
Method for preparing low-oxygen metal by fused salt electrolysis-magnesiothermic reduction of metal oxide Download PDFInfo
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- 150000003839 salts Chemical class 0.000 title claims abstract description 194
- 229910052751 metal Inorganic materials 0.000 title claims abstract description 103
- 239000002184 metal Substances 0.000 title claims abstract description 103
- 239000001301 oxygen Substances 0.000 title claims abstract description 90
- 229910052760 oxygen Inorganic materials 0.000 title claims abstract description 90
- 229910044991 metal oxide Inorganic materials 0.000 title claims abstract description 63
- 150000004706 metal oxides Chemical class 0.000 title claims abstract description 62
- 238000000034 method Methods 0.000 title claims abstract description 31
- 238000006722 reduction reaction Methods 0.000 claims abstract description 101
- 238000005868 electrolysis reaction Methods 0.000 claims abstract description 86
- 238000006243 chemical reaction Methods 0.000 claims abstract description 67
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 54
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L magnesium chloride Substances [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 claims abstract description 35
- 238000010438 heat treatment Methods 0.000 claims abstract description 32
- 238000002156 mixing Methods 0.000 claims abstract description 32
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 30
- 229910001629 magnesium chloride Inorganic materials 0.000 claims abstract description 29
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 29
- 239000012702 metal oxide precursor Substances 0.000 claims abstract description 25
- 229910052761 rare earth metal Inorganic materials 0.000 claims abstract description 22
- 150000002910 rare earth metals Chemical class 0.000 claims abstract description 21
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 10
- 239000010936 titanium Substances 0.000 claims description 32
- 239000000843 powder Substances 0.000 claims description 18
- 238000005292 vacuum distillation Methods 0.000 claims description 16
- 238000001035 drying Methods 0.000 claims description 13
- 238000005245 sintering Methods 0.000 claims description 13
- 238000007789 sealing Methods 0.000 claims description 11
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 10
- 238000003825 pressing Methods 0.000 claims description 9
- -1 oxygen metals Chemical class 0.000 claims description 8
- 238000002360 preparation method Methods 0.000 claims description 6
- 239000011780 sodium chloride Substances 0.000 claims description 6
- 239000000853 adhesive Substances 0.000 claims description 4
- 230000001070 adhesive effect Effects 0.000 claims description 4
- 238000000465 moulding Methods 0.000 claims description 4
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 claims description 3
- XHCLAFWTIXFWPH-UHFFFAOYSA-N [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] Chemical class [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] XHCLAFWTIXFWPH-UHFFFAOYSA-N 0.000 claims description 2
- WIHZLLGSGQNAGK-UHFFFAOYSA-N hafnium(4+);oxygen(2-) Chemical class [O-2].[O-2].[Hf+4] WIHZLLGSGQNAGK-UHFFFAOYSA-N 0.000 claims description 2
- 229910000476 molybdenum oxide Inorganic materials 0.000 claims description 2
- 229910000484 niobium oxide Inorganic materials 0.000 claims description 2
- URLJKFSTXLNXLG-UHFFFAOYSA-N niobium(5+);oxygen(2-) Chemical class [O-2].[O-2].[O-2].[O-2].[O-2].[Nb+5].[Nb+5] URLJKFSTXLNXLG-UHFFFAOYSA-N 0.000 claims description 2
- PQQKPALAQIIWST-UHFFFAOYSA-N oxomolybdenum Chemical class [Mo]=O PQQKPALAQIIWST-UHFFFAOYSA-N 0.000 claims description 2
- BPUBBGLMJRNUCC-UHFFFAOYSA-N oxygen(2-);tantalum(5+) Chemical class [O-2].[O-2].[O-2].[O-2].[O-2].[Ta+5].[Ta+5] BPUBBGLMJRNUCC-UHFFFAOYSA-N 0.000 claims description 2
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical class [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 claims description 2
- 230000035484 reaction time Effects 0.000 claims description 2
- 229910001936 tantalum oxide Inorganic materials 0.000 claims description 2
- 229910001930 tungsten oxide Inorganic materials 0.000 claims description 2
- 229910001935 vanadium oxide Inorganic materials 0.000 claims description 2
- 229910001928 zirconium oxide Inorganic materials 0.000 claims description 2
- UOUJSJZBMCDAEU-UHFFFAOYSA-N chromium(3+);oxygen(2-) Chemical class [O-2].[O-2].[O-2].[Cr+3].[Cr+3] UOUJSJZBMCDAEU-UHFFFAOYSA-N 0.000 claims 1
- VVRQVWSVLMGPRN-UHFFFAOYSA-N oxotungsten Chemical class [W]=O VVRQVWSVLMGPRN-UHFFFAOYSA-N 0.000 claims 1
- SOQBVABWOPYFQZ-UHFFFAOYSA-N oxygen(2-);titanium(4+) Chemical class [O-2].[O-2].[Ti+4] SOQBVABWOPYFQZ-UHFFFAOYSA-N 0.000 claims 1
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 39
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 36
- 239000000047 product Substances 0.000 description 35
- 239000011777 magnesium Substances 0.000 description 33
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 23
- 239000011733 molybdenum Substances 0.000 description 23
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 17
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 17
- 239000010935 stainless steel Substances 0.000 description 17
- 229910001220 stainless steel Inorganic materials 0.000 description 17
- 239000000203 mixture Substances 0.000 description 16
- 229910052749 magnesium Inorganic materials 0.000 description 15
- 239000004408 titanium dioxide Substances 0.000 description 15
- 239000008188 pellet Substances 0.000 description 14
- 229910052709 silver Inorganic materials 0.000 description 13
- 238000002844 melting Methods 0.000 description 12
- 230000008018 melting Effects 0.000 description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 11
- 229910052799 carbon Inorganic materials 0.000 description 11
- 239000002243 precursor Substances 0.000 description 11
- 238000004140 cleaning Methods 0.000 description 10
- 238000001291 vacuum drying Methods 0.000 description 10
- 239000007789 gas Substances 0.000 description 9
- 239000012535 impurity Substances 0.000 description 9
- 239000000395 magnesium oxide Substances 0.000 description 9
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 8
- 239000003795 chemical substances by application Substances 0.000 description 8
- 238000005086 pumping Methods 0.000 description 8
- 239000004372 Polyvinyl alcohol Substances 0.000 description 7
- 239000004020 conductor Substances 0.000 description 7
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- 239000003638 chemical reducing agent Substances 0.000 description 6
- 239000006227 byproduct Substances 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 230000001404 mediated effect Effects 0.000 description 5
- 229910052720 vanadium Inorganic materials 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- SKKMWRVAJNPLFY-UHFFFAOYSA-N azanylidynevanadium Chemical compound [V]#N SKKMWRVAJNPLFY-UHFFFAOYSA-N 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 4
- 229910052804 chromium Inorganic materials 0.000 description 4
- 239000011651 chromium Substances 0.000 description 4
- 238000005265 energy consumption Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 229910052758 niobium Inorganic materials 0.000 description 4
- 239000010955 niobium Substances 0.000 description 4
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 4
- 229910052726 zirconium Inorganic materials 0.000 description 4
- 229910052684 Cerium Inorganic materials 0.000 description 3
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 3
- 229910052689 Holmium Inorganic materials 0.000 description 3
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 3
- 239000003085 diluting agent Substances 0.000 description 3
- 238000004821 distillation Methods 0.000 description 3
- GNTDGMZSJNCJKK-UHFFFAOYSA-N divanadium pentaoxide Chemical compound O=[V](=O)O[V](=O)=O GNTDGMZSJNCJKK-UHFFFAOYSA-N 0.000 description 3
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 3
- 239000010937 tungsten Substances 0.000 description 3
- 229910052727 yttrium Inorganic materials 0.000 description 3
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 2
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 description 2
- 229910019015 Mg-Ag Inorganic materials 0.000 description 2
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 239000001099 ammonium carbonate Substances 0.000 description 2
- 150000001805 chlorine compounds Chemical class 0.000 description 2
- 229910000423 chromium oxide Inorganic materials 0.000 description 2
- 229910052735 hafnium Inorganic materials 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 229910052746 lanthanum Inorganic materials 0.000 description 2
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 2
- 238000005554 pickling Methods 0.000 description 2
- 239000000049 pigment Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000011946 reduction process Methods 0.000 description 2
- 229910052715 tantalum Inorganic materials 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- 229910000013 Ammonium bicarbonate Inorganic materials 0.000 description 1
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- 229910004664 Cerium(III) chloride Inorganic materials 0.000 description 1
- 229910002249 LaCl3 Inorganic materials 0.000 description 1
- 229910002420 LaOCl Inorganic materials 0.000 description 1
- 229910017544 NdCl3 Inorganic materials 0.000 description 1
- 229910052779 Neodymium Inorganic materials 0.000 description 1
- 229910052777 Praseodymium Inorganic materials 0.000 description 1
- 229910009523 YCl3 Inorganic materials 0.000 description 1
- MCMNRKCIXSYSNV-UHFFFAOYSA-N ZrO2 Inorganic materials O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 235000012538 ammonium bicarbonate Nutrition 0.000 description 1
- 235000012501 ammonium carbonate Nutrition 0.000 description 1
- 235000019270 ammonium chloride Nutrition 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- QDOXWKRWXJOMAK-UHFFFAOYSA-N chromium(III) oxide Inorganic materials O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 description 1
- 229910000449 hafnium oxide Inorganic materials 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- JKQOBWVOAYFWKG-UHFFFAOYSA-N molybdenum trioxide Inorganic materials O=[Mo](=O)=O JKQOBWVOAYFWKG-UHFFFAOYSA-N 0.000 description 1
- ZKATWMILCYLAPD-UHFFFAOYSA-N niobium pentoxide Inorganic materials O=[Nb](=O)O[Nb](=O)=O ZKATWMILCYLAPD-UHFFFAOYSA-N 0.000 description 1
- QGLKJKCYBOYXKC-UHFFFAOYSA-N nonaoxidotritungsten Chemical compound O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1 QGLKJKCYBOYXKC-UHFFFAOYSA-N 0.000 description 1
- 239000011833 salt mixture Substances 0.000 description 1
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- 230000001502 supplementing effect Effects 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/04—Electrolytic production, recovery or refining of metals by electrolysis of melts of magnesium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B5/00—General methods of reducing to metals
- C22B5/02—Dry methods smelting of sulfides or formation of mattes
- C22B5/04—Dry methods smelting of sulfides or formation of mattes by aluminium, other metals or silicon
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Electrolytic Production Of Metals (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
The invention provides a method for preparing low-oxygen metal by molten salt electrolysis-magnesiothermic reduction of metal oxide, which comprises the following steps: preparing a metal oxide precursor; rare earth RE and excess MgCl2Placing in a reaction vessel, heating to melt to obtain MgCl2‑RECl3Mixing molten salt; in the mixed molten salt, C is used as an anode, Ti or W or Mo is used as a cathode to form a molten salt electrolytic cell, and molten salt electrolysis is carried out under the conditions that the temperature is 700-900 ℃ and the voltage is 2.4-3.0V; and after the fused salt electrolysis is finished, communicating the metal oxide precursor in the mixed fused salt with the cathode deposited with metal Mg for reduction reaction, and obtaining the low-oxygen metal after the reduction reaction is finished. The method of the invention can reduce the oxygen content in the metal of the reduction product to below 500 ppm.
Description
Technical Field
The invention belongs to the technical field of metal preparation, and particularly relates to a method for preparing low-oxygen metal by molten salt electrolysis-magnesium thermal reduction of metal oxide.
Background
At present, the preparation of metals such as titanium, vanadium and the like in magnesium chloride molten salt by virtue of magnesiothermic reduction is reported, but the oxygen content of the product metal obtained based on the existing magnesiothermic reduction technology is high, and the oxygen content in the general product metal is up to more than 10000 ppm. For example, for the magnesium thermal Reduction of metallic Titanium, the synthetic of Titanium magnetic Reduction of TiO2(Pigment) (synthesis of titanium by magnesiothermic reduction of titanium dioxide (Pigment)), authors: MSR boli tivar, DIB Friedrich first reported the thermal reduction of titanium dioxide using magnesium. Because titanium dioxide is in the process of reducing step by step, a large amount of heat is released in the process of generating Ti from TiO, the reaction temperature is increased rapidly, thermodynamic conditions required by the reaction cannot be achieved, and the oxygen content in the final product is higher. If the amount of magnesium is increased or calcium heat is used for further reduction, the experimental result shows that the oxygen content of the product is still over 20000ppm (2%), and the oxygen content in the product is still very high.
Publication No. CN107639234A, entitled: magnesiothermic reduction of TiO2The patent application discloses a method for preparing metallic titanium powder by using titanium dioxide, magnesium powder and a diluent as raw materials and reducing the raw materials at the temperature of 400-1400 ℃ to prepare the metallic titanium powder. According to the heat generated by reducing titanium dioxide by magnesium, the addition amount of the diluent is calculated, so that the diluent absorbs the heat released in the reaction process, the heat absorption process and the heat release process are balanced, and the reaction of reducing titanium dioxide by magnesium heat is promoted, thereby reducing the content of titanium dioxide in the product and reducing the oxygen content of the prepared metal titanium powder. However, it is clear from examples 1 to 6 that the oxygen content in the prepared metallic titanium powder is still high, and the lowest oxygen content of the metallic titanium powder is 3700ppm (0.37%).
Oxygen in the metallic titanium exists in a solid solution state, and the performance of the titanium metal product is directly influenced by the content of the oxygen. In the prior art, the oxygen content in the metallic titanium prepared by the magnesium thermal reduction is high, the oxygen content in the metallic titanium can not be reduced to be below 500ppm, and the requirement of American Society for Testing and Materials (ASTM) on the first-grade pure titanium can not be met.
Disclosure of Invention
In view of the deficiencies in the prior art, it is an object of the present invention to address one or more of the problems in the prior art as set forth above. For example, it is an object of the present invention to provide a method for producing a metal in which the oxygen content is controlled to 500ppm or less, and even to 300ppm or less.
The invention provides a method for preparing low-oxygen metal by molten salt electrolysis-magnesiothermic reduction of metal oxide, which comprises the following steps: preparing a metal oxide precursor; rare earth RE and excess MgCl2Placing in a reaction vessel, heating to melt to obtain MgCl2-RECl3Mixing molten salt; in the mixed molten salt, C is used as an anode, Ti or W or Mo is used as a cathode to form a molten salt electrolytic cell, and molten salt electrolysis is carried out under the conditions that the temperature is 700-900 ℃ and the voltage is 2.4-3.0V so as to deposit metal Mg on the cathode; and after the molten salt electrolysis is finished, stopping applying the voltage, communicating the metal oxide precursor in the mixed molten salt with the cathode deposited with the metal Mg to perform a reduction reaction, and obtaining the low-oxygen metal after the reduction reaction is finished.
FIG. 1 is a schematic view of the reduction process and apparatus of the present invention. Rare earth RE and excess MgCl are added to a reaction vessel 62. NaCl and/or KCl may be added to the reaction vessel as required. After the reaction vessel 6 is heated until the molten salt is melted, MgCl can be obtained in the reaction vessel2-RECl3Mixed molten salt or NaCl-MgCl2-RECl3Mixed molten salts or KCl-MgCl2-RECl3Mixed molten salt or KCl-NaCl-MgCl2-RECl3Mixed molten salt (MgCl in FIG. 1)2-(NaCl-KCl)-RECl3Molten salt). The anode 4 may be a carbon anode and the cathode 3 may be Ti or Mo or W. The anode 4, the cathode 3, the power supply, the lead and the mixed molten salt form a molten salt electrolytic cell, wherein e-Representing electrons. The reactions that occur in the molten salt electrolysis cell are:
anode: c(s) + xO2-＝COx(g)+2xe- (1)
Cathode: xMg2++2xe-＝xMg(l) (2)
After the molten salt electrolysis process is completed, metal Mg is generated on the cathode 3. Cl may also occur on the anode—After losing electrons, it becomes Cl2. The switch 5 is then turned on, the molten salt electrolysis cell is no longer energized (i.e. no molten salt electrolysis is performed), and the metal oxide precursor 1 placed in the mixed molten salt is communicated with the cathode 3 on which the metal Mg is electrodeposited via a metal conductor 2 (e.g. Mo rod). After the connection, the reduction reaction is started under the condition that the temperature is 700-900 ℃. The metal conductor, the cathode and the anode may be connected by a wire. The switch 5 is closed, the metal conductor 2 and the cathode 3 are communicated through the conductor to form a reduction cell, the metal Mg deposited on the cathode 3 is active and loses electrons, the electrons are transmitted to the metal conductor 2, the metal oxide connected with the metal conductor 2 obtains electrons and is reduced into metal, namely the metal oxide is reduced through an Electron Mediated Reaction (EMR), and the following reaction occurs:
negative electrode: yMg (l) ═ yMg2++2ye- (3)
And (3) positive electrode: a. thexOy+2ye-＝xA+yO2- (4)
And (3) total reaction: a. thexOy+yMg(l)＝xA+yMgO (5)
Wherein A can be one of Ti, V, Cr, Zr, Hf, Nb, Ta, Mo and W.
In the molten salt electrolysis process, the reducing agent metal magnesium can be obtained through the reaction (2). Magnesium metal is attached to the cathode 3. The above-mentioned reactions (3) to (5) can occur by an electron-mediated reaction to reduce the metal oxide. The fused salt electrolysis and the metal oxide reduction reaction (electron mediated reaction) are separated, so that Mg can be prevented from being directly separated out on the surface of the metal oxide, the metal oxide can not be coated, and the reduction reaction can be ensured to be smoothly carried out. If molten salt electrolysis and oxide reduction are not separated, the metal oxide is directly used as a cathode of a molten salt electrolysis cell, Mg separated out during molten salt electrolysis can be directly separated out on the surface of the metal oxide, the Mg is coated on the surface of the metal oxide to prevent a reduction by-product (magnesium oxide) from being dissolved in molten salt, the reduction by-product is coated on the surface of the metal oxide to prevent the metal oxide to be reduced from contacting with a reducing agent, and therefore the reduction reaction is prevented from being carried out. In addition, the pollution of carbon and iron can be effectively inhibited.
During the electron mediated reaction, the following two reactions can occur for the by-product MgO.
On the one hand, MgO can react with RECl in molten salts3The reaction of formula (6) takes place, the by-products of the reduction of the intermediate reaction MgO and RECl3After the reaction, the activity of MgO in the molten salt is gradually reduced, and the chemical equilibrium of the reaction (5) is promoted to move rightwards, so that the reduction of the metal oxide can be more thorough. Oxygen ([ O ]) in product metal]A) Reaction (7) occurs, reducing the oxygen content of the product metal.
MgO(s)+RECl3(l)＝MgCl2(l)+REOCl(s) (6)
[O]A+Mg(l)+RECl3(l)＝MgCl2(l)+REOCl(s) (7)
On the other hand, MgO can also be dissolved in molten salts to form Mg2+And O2-，O2-Migrate to the C anode and can react (1) to form CO or CO2Discharging the molten salt system. Due to O2-The activity of MgO in the molten salt is continuously reduced, and the chemical equilibrium of the reaction (5) is promoted to move rightwards, so that the reduction of the metal oxide can be more complete. And because the activity of oxygen ions dissolved in the molten salt is reduced, the oxygen in the product metal can be favorably transferred out. For the reasons of the above two aspects, the method of the present invention can reduce oxygen in the product metal to 500ppm or less, and if the time of the reduction reaction is longer than 10 hours, oxygen in the metal can be reduced to 300ppm or less.
In addition, the invention can realize (semi-) continuous operation. By replacing the C anode and supplementing molten salt, the (semi-) continuous operation is realized.
Compared with the prior art, the beneficial effects of the invention at least comprise at least one of the following:
(1) the invention adds rare earth chloride RECl into the molten salt3The oxygen content in the metal of the reduction product can be reduced to be below 500 ppm;
(2) through the mutual cooperation of molten salt electrolysis and electron mediated reaction, the method can realize (semi-) continuous operation of metal oxide reduction, and has high efficiency, small magnesium consumption and low cost;
(3) the mixed molten salt used in the invention has low melting point, can lower the temperature required by reduction, and saves energy consumption;
(4) according to the invention, the residual metal Mg and molten salt on the surface of the product metal are removed by vacuum distillation cleaning, and acid solution cleaning is not needed, so that the energy is saved and the environment is protected;
(5) the invention can realize the clean and cyclic utilization of the rare earth by-product (such as REOCl), does not consume rare earth, and saves resources;
(6) the invention adopts magnesium as a reducing agent, and the price of Mg is low and the cost is low;
(7) the invention has low reduction temperature and easy control of the reduction process;
(8) the invention can effectively inhibit the pollution of carbon and iron to metal products.
Drawings
The above and other objects and features of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:
FIG. 1 shows the principle and schematic diagram of an example of the method for preparing low-oxygen metal by molten salt electrolysis-magnesiothermic reduction of metal oxide according to the present invention.
Description of reference numerals:
1-metal oxide, 2-metal conductor, 3-cathode, 4-anode, 5-switch, 6-reaction vessel.
Detailed Description
Hereinafter, a method for preparing a low-oxygen metal by molten salt electrolysis-magnesiothermic reduction of a metal oxide according to the present invention will be described in detail with reference to the accompanying drawings and exemplary embodiments.
The invention provides a method for preparing low-oxygen metal by molten salt electrolysis-magnesiothermic reduction of metal oxide. In one exemplary embodiment of the method of molten salt electrolysis-magnesiothermic reduction of metal oxides to low oxygen metals of the present invention, the method may comprise:
s01, preparing the metal oxide precursor.
S02, mixing rare earth RE and excess MgCl2Placing the mixture in a reaction vessel, heating the mixture to be molten, and fully reacting the mixture to obtain MgCl2-RECl3And (4) mixing the molten salt. The reaction vessel here may be of the same type as the metal in the pre-reduced metal oxide.
S03, in the mixed molten salt, C is used as an anode, Ti or W or Mo is used as a cathode to form a molten salt electrolytic cell, and molten salt electrolysis is carried out under the conditions that the temperature is 700-900 ℃ and the voltage is 2.4-3.0V. For example, Ti may be used as a cathode in the preparation of low-oxygen metal titanium, and W or Mo may be used as a cathode in the preparation of low-oxygen metal vanadium, low-oxygen metal chromium, low-oxygen metal zirconium, low-oxygen metal hafnium, low-oxygen metal tantalum, low-oxygen metal niobium, low-oxygen metal molybdenum, and low-oxygen metal tungsten.
And S04, stopping applying voltage after molten salt electrolysis is finished, communicating the metal oxide precursor in the mixed molten salt with the cathode deposited with metal Mg to perform reduction reaction, and obtaining the low-oxygen metal after the reduction reaction is finished.
Further, the metal oxide may include titanium oxide, vanadium oxide, chromium oxide, zirconium oxide, hafnium oxide, tantalum oxide, niobium oxide, molybdenum oxide, and tungsten oxide. For example, titanium dioxide, vanadium pentoxide, chromium oxide, etc. may be mentioned.
Further, preparing the metal oxide precursor may include: mixing metal oxide powder with an adhesive, and then pressing and molding under the pressure of 600-750 MPa; sintering the pressed metal oxide at 1000-1200 ℃ for 24-30 h to obtain the metal oxide precursor. For example, the material may be press-molded under a pressure of 720MPa and then sintered at 1100 ℃. The press forming may include pressing the metal oxide powder into a round cake shape having a diameter of 15mm to 25mm and a thickness of 4mm to 8 mm. For example, preparing a titanium dioxide precursor can include: pressing and molding titanium dioxide powder under the pressure of 700-750 MPa; sintering the pressed and formed titanium dioxide at 1050-1200 ℃ for 24-28 h to obtain the titanium dioxide precursor. For example, the material may be press-molded under a pressure of 720MPa and then sintered at 1100 ℃. The press-molding may include pressing the titanium dioxide powder into a cake shape having a diameter of 15mm to 25mm and a thickness of 4mm to 8 mm. The titanium dioxide powder may be anatase type titanium dioxide. The adhesive may be an adhesive commonly used in the art, for example, PVB, polyvinyl alcohol, etc., and may be added in an amount of 3% to 8% by mass based on the mass of the metal oxide. For example, 5%.
Further, the porosity of the metal oxide precursor may be set to 22% to 33%. The porosity of the metal oxide precursor has an important influence on the effective reaction area, the entry of reducing substances into the precursor, and the diffusion of oxygen ions in the metal oxide. The porosity is large, so that the circulation between the metal oxide precursor and external high-temperature molten salt is easy, on one hand, the porosity is set to be more than 22%, molten magnesium can enter the interior of the precursor through the pores, the reaction of the metal oxide in the precursor is accelerated, and the phenomena that the reaction of the metal oxide in the precursor does not completely influence the oxygen content of the product metal and the reaction time is influenced because the magnesium is contacted with the metal oxide in the precursor too slowly are avoided; and, because the porosity is suitable, the magnesium oxide generated after the reaction of magnesium and metal oxide is easy to discharge the precursor, and the reaction (5) is promoted to be carried out rightwards, so that the reduction speed of the metal oxide is increased, and the metal oxide can be completely reduced. On the other hand, the porosity of the precursor cannot be more than 33%, and the porosity is too high, so that the strength of the precursor is not enough, and the formed product is powder dispersed in the mixed molten salt in the reaction process, which is not beneficial to the collection of metal. On the other hand, the porosity is not less than 22%, and the porosity is less than 22%, so that the magnesium and the molten salt are not beneficial to entering the interior of the metal oxide precursor, and the reduction reaction is not beneficial to being carried out. Preferably, the porosity of the precursor is 28%, at which point the oxygen content of the product metal is lower, and can reach below 280 ppm. The relationship between the porosity and the metal oxygen content shows a rapid descending trend, and after the porosity reaches 22%, the oxygen content of the metal changes relatively stably and becomes lower. Therefore, in order to ensure that the oxygen content of the metal oxide is low and the product formed by pressing has a complete structure and is convenient to recover, the porosity of the metal oxide precursor is controlled to be 22-33%. Here, the porosity in the present invention means a percentage of the volume of the open pores inside the material to the total volume of the metal oxide precursor.
Further, preparing the metal oxide precursor may include: uniformly mixing metal oxide and pore-forming agent, and then pressing and forming under the pressure of 600-750 MPa; sintering the mixture of the metal oxide and the pore-forming agent which are formed by pressing at the temperature of 1000-1200 ℃ to obtain a metal oxide precursor. For example, the powder may be press-molded under a pressure of 700MPa and then sintered at 1140 ℃. The porosity of the sintered pellets gradually decreases as the sintering temperature increases. When the sintering temperature is below 900 ℃, the produced product metal is distributed in molten salt in a powder form and is inconvenient to recover. When the sintering temperature is 1300 ℃, the porosity of the sintered small pieces is low, oxygen in the metal product is not favorably migrated out, and the oxygen content in the metal oxide is high. Therefore, the sintering temperature is controlled to be 1000-1200 ℃.
In the above, the sintering process of the mixture of the pressed metal oxide and the pore-forming agent may be: heating to 300-350 ℃ at a heating rate of 3-4 ℃/min, keeping the temperature for 1-2 h, heating to 600-700 ℃ at a heating rate of 5-6 ℃/min, keeping the temperature for 30-50 min, and finally heating to 1000-1200 ℃ at a heating rate of 6-8 ℃/min, keeping the temperature for 24-30 h. Both the sintering temperature and the sintering time have a great influence on the porosity of the metal oxide precursor. By adopting the sectional roasting and the sectional heating, the uniform pore-forming of the metal oxide precursor can be ensured. The uniform gaps can form channels which are uniformly communicated with each other from outside to inside in the metal oxide precursor, so that magnesium and oxygen ions as reducing agents can be better migrated, and the reduction reaction is promoted to be carried out. The pore-forming agent can be one or a combination of ammonium bicarbonate, ammonium carbonate or ammonium chloride. Of course, the pore-forming agent of the present invention is not limited thereto, and other inorganic pore-forming agents may be used. By adopting the step-type temperature rise to reach the sintering temperature, compared with the direct heating to reach the sintering temperature, the reduction is carried out under the conditions with the same other parameters, and when the same metal oxygen content is obtained, the reduction time is shortened by more than 3 percent on average.
Further, in order to increase the reaction area of the reducing agent magnesium and the metal oxide precursor, the mixture of the metal oxide and the pore-forming agent may be pressed into a tablet having a thickness of 4mm to 8 mm. For example, pressed into small pieces having a thickness of 5 mm. The small pieces can be round small pieces with the diameter of 15-25 mm. Of course, the pellet shape of the present invention is not limited thereto, and may be pressed into a cube or rectangular parallelepiped pellet. The mixture of metal oxide and pore former may also be pressed into pellets. During large-scale production, uniform gaps can be formed among the pellets, so that molten salt is conveniently distributed around the pellets, and reduction is facilitated. For example, pellets having a diameter of 2mm to 4mm can be prepared. The mixture of the metal oxide and the pore-forming agent can also be pressed into a cylinder with the bottom surface diameter of 2 mm-4 mm and the height of 3 mm-6 mm.
Further, MgCl was obtained2-RECl3The step of mixing the molten salt may include:
charging RE and excess MgCl to the reaction vessel2And heating to 700-900 ℃ until the molten salt is melted to obtain the mixed molten salt. The following reaction occurs after heating to melt:
2RE (s) + 3MgCl2 (l) ＝ 3Mg (l) + 2RECl3 (l) (8)
reaction (8) produces RECl3. During the reaction, no rare earth RE in the reaction vessel remains, and MgCl2There is a surplus, and therefore, a mixed molten salt can be obtained in the reaction vessel. The Mg prepared by the reaction (8) can be used as a part of reducing agent. Above, excess MgCl2Refers to MgCl added according to reaction (8)2More MgCl is required than the RE is completely consumed2. For example, MgCl added2The content may be 5 wt.% to 30 wt.% more than actually theoretically needed, for example, 15 wt.% more. Further, MgCl was obtained2-RECl3KCl and/or Na can also be added into the reaction vessel in the step of mixing the molten saltCl, MgCl can be obtained2-KCl-RECl3Mixed molten salt, MgCl2-NaCl-RECl3Mixed molten salts or MgCl2-KCl-NaCl-RECl3And (4) mixing the molten salt. In MgCl2-RECl3The melting point of the mixed molten salt can be further reduced by adding KCl and/or NaCl into the mixed molten salt. Preferably, the mixed molten salt may be MgCl2-KCl-RECl3Mixed molten salt, MgCl2-NaCl-RECl3Mixed molten salts or MgCl2-KCl-NaCl-RECl3And (4) mixing the molten salt. Compared to MgCl2-RECl3The melting point of the mixed molten salt can be obviously reduced if KCl and/or NaCl is added into the mixed molten salt, and energy consumption is saved. More preferably, the mixed molten salt is MgCl due to lower melting point of the mixed molten salt containing KCl-NaCl2-KCl-NaCl-RECl3。
Further, MgCl was obtained2-RECl3The step of mixing the molten salt may further comprise:
s201, to MgCl2And (5) carrying out drying treatment. For example, MgCl may be used2Vacuum drying at 200 deg.c for 24-48 hr.
S202, placing rare earth RE and a predetermined amount of Ag at the bottom of the reaction vessel, and placing MgCl after drying2Adding into a reaction vessel, sealing the reaction vessel and vacuumizing. Placing rare earth RE and a predetermined amount of Ag into a reaction vessel, and taking out dried MgCl from a vacuum drying oven2Quickly pouring into a reaction container, putting the reaction container into a stainless steel reactor, covering the stainless steel reactor with a cover, sealing the reactor, and vacuumizing the reactor. The Ag here may be a 99.99% Ag ingot. The amount of Ag added may be 30g to 60 g. Of course, the amount of Ag added may be determined depending on the amount of the actually reduced metal oxide, and may be a given value or an empirical value. The purpose of adding Ag into the molten salt is to enable Mg which is generated by electrolysis and is free in the molten salt and not attached to a cathode to react with the added Ag to generate Mg-Ag alloy, the density of the generated Mg-Ag alloy is higher than that of the molten salt, and the Mg does not float on the surface of the molten salt to cause short circuit. If Ag is not added, Mg not attached to the cathode may float up to the surface of the molten salt to cause short-circuiting.
S203, will turn overDrying the container at 350-450 deg.c in vacuum environment, and heating to melt to obtain MgCl2-RECl3And (4) mixing the molten salt. For example, the drying may be carried out for 24 hours after evacuation at 400 ℃.
As described above, after the rare earth RE and a predetermined amount of Ag are placed in the reaction vessel, KCl and/or NaCl may be added simultaneously. While Ag is added to the reaction vessel, a predetermined amount of titanium sponge may be added. The titanium sponge can absorb oxygen in a reaction environment. The mass of the added titanium sponge can be determined according to the amount of the molten salt and the amount of the metal oxide, and can be a given value or an empirical value. For example, the amount of titanium sponge added may be 20 g.
Further, after obtaining the mixed molten salt, the molten salt electrolysis is preceded by pre-electrolysis, which may include: and C is used as an anode, and the reaction vessel is used as a cathode to pre-electrolyze the mixed molten salt. The purpose of pre-electrolysis is to remove impurities such as residual gas or metal in the mixed molten salt. The pre-electrolysis temperature can be 700-900 ℃, the pre-electrolysis voltage can be 2.0-2.2V, and the pre-electrolysis time can be 5-12 h.
Further, the temperature of the molten salt electrolysis is set to be 700-900 ℃, the electrolysis voltage is set to be 2.4-3.0V, and the electrolysis time can be 86-173 ks (kiloseconds). For example, the electrolysis time may be 24 to 48 hours. The temperature for molten salt electrolysis needs to be set higher than the melting point of molten salt, so the temperature for molten salt electrolysis is set between 700 ℃ and 900 ℃. The voltage requirement for molten salt electrolysis is higher than MgCl2But lower than the decomposition electrolysis of other chlorides.
Further, the reduction time may be 8 to 12 hours. For example, the reduction time may be 10 hours. For the reduction time, if the reduction time is less than 8 hours, the incomplete reduction of the metal oxide will affect the oxygen content in the product metal, which is very high. If the reduction time is longer than 12 hours, the oxygen content in the product metal is not substantially reduced. By counting the oxygen content of the product metal under different reduction times, the oxygen content in the product metal is gradually reduced along with the extension of the reduction time, and the oxygen content in the product metal is slowly reduced after the reduction time reaches 12h, so that the reduction time is set to be 8 h-12 h in consideration of cost and reduction time saving.
Further, the step of obtaining the low-oxygen metal may further comprise: taking out the reduction product in the reaction vessel after the reduction reaction is finished; and (3) carrying out vacuum distillation on the reduction product for 3-5 h under the conditions that the temperature is 850-1000 ℃ and the pressure is 0.1-1 Pa to obtain the low-oxygen metal. After the metal oxide is reduced to metal, a large amount of molten salt adheres to the surface of the metal. In order to obtain a metal with high purity, molten salt on the surface needs to be removed. Distillation is carried out in vacuum, the boiling point of the fused salt can be reduced in a vacuum environment, the fused salt can volatilize under the condition of 850-1000 ℃, the volatilized fused salt can be directly recycled and reused, and waste water and waste of the fused salt after pickling caused by removing the fused salt on the surface by other operations such as pickling are avoided. The distillation temperature is too low, and the molten salt cannot volatilize; the distillation temperature is too high, the energy consumption is increased, and unnecessary waste is caused. For example, the temperature of the vacuum distillation may be 920 ℃ and the pressure 0.6 Pa. The time of vacuum distillation can be 3.5 h-5 h. The molten salt can be thoroughly treated in the vacuum distillation time, unnecessary vacuum distillation time is avoided, and energy consumption is saved. The molten salt obtained by vacuum distillation can be recycled.
Further, the RE rare earth metal can be any one of Y, La, Ce, Nd, Ho, Gd, Dy, Lu and Pr. La and Ce are cheap and low in cost. After using the chlorides of Y or Ho, the oxygen content in the reduction product metallic titanium can be reduced to a lower degree. The solubility of YOCl or HoOCl in the molten salt is greater than that of LaOCl or CeOCl, and REOCl is dissolved in the molten salt, so that the activity is reduced, and the following deoxidation reactions are promoted to be carried out in the forward direction:
[O]A+Mg(l)+RECl3(l)＝MgCl2(l)+REOCl(s) (9)
the deoxidation reaction is more thorough and the deoxidation effect is better.
In order that the above-described exemplary embodiments of the invention may be better understood, further description thereof with reference to specific examples is provided below.
Example 1
And 3, heating to 400 ℃, and drying for 24 hours under the vacuum-pumping condition.
And 5, carrying out pre-electrolysis by taking carbon as an anode and a titanium crucible as a cathode to remove residual gas and metal impurities in the molten salt.
Step 7, performing formal molten salt electrolysis by using the device shown in the attached figure 1: c is used as an anode, Ti is used as a cathode (35 mm is inserted), the electrolysis temperature is 700 ℃, the voltage is applied to 2.4V, and the electrolysis time is 86 ks.
And 8, stopping molten salt electrolysis after the molten salt electrolysis is finished, turning on a switch 5 in the figure 1, starting the reduction reaction, and keeping for 10 hours to ensure that the reduction reaction is completely carried out.
And 9, after the reduction is finished, taking out the reduced small pieces, removing the residual molten salt on the surface of the titanium by vacuum distillation (the temperature is 850 ℃, the time is 3.5h, and the system pressure is 0.2Pa), and then cleaning by using a small amount of dilute hydrochloric acid (1+ 10). Finally, the oxygen content was determined using LECO (TC-400). The oxygen content in the product titanium metal was determined to be 298 ppm.
Example 2
And 3, heating to 400 ℃, and drying for 24 hours under the vacuum-pumping condition.
And 5, carrying out pre-electrolysis by taking carbon as an anode and a titanium crucible as a cathode to remove impurities such as residual gas or metal in the molten salt.
Step 7, performing formal molten salt electrolysis by using the device shown in the attached figure 1: c is used as an anode, Ti is used as a cathode (inserting 38mm), the electrolysis temperature is 800 ℃, the voltage is applied to 2.9V, and the electrolysis time is 168 ks.
And 8, stopping molten salt electrolysis after the molten salt electrolysis is finished, turning on the switch 5, starting the reduction reaction, and keeping for 11 hours to ensure that the reduction reaction is completely carried out.
And 9, after the reduction is finished, taking out the reduced small pieces, removing residual molten salt on the surface of the titanium by vacuum distillation (the temperature is 850 ℃, the time is 4 hours, and the system pressure is 1Pa), and then cleaning by using a small amount of dilute hydrochloric acid (1+ 10). Finally, the oxygen content was determined by LECO (TC-400) and the oxygen content in the product titanium was 308 ppm.
Example 3
And 3, heating to 400 ℃, and drying for 24 hours under the vacuum-pumping condition.
And 5, carrying out pre-electrolysis by taking carbon as an anode and a vanadium-nitrogen crucible as a cathode to remove impurities such as residual gas or metal in the molten salt.
Step 7, performing formal molten salt electrolysis by using the device shown in the attached figure 1: c is used as an anode, Mo is used as a cathode (40 mm is inserted), the electrolysis temperature is 900 ℃, the voltage is applied to 3.0V, and the electrolysis time is 87 ks.
And 8, stopping molten salt electrolysis after the molten salt electrolysis is finished, turning on the switch 5, starting the reduction reaction, and keeping for 10 hours to ensure that the reduction reaction is completely carried out.
And 9, after the reduction is finished, taking out the reduced small pieces, removing the residual molten salt on the surface of the vanadium by vacuum distillation (the temperature is 950 ℃, the time is 3.7h, and the system pressure is 0.8Pa), and then cleaning by using a small amount of dilute hydrochloric acid (1+ 10). Finally, the oxygen content was determined by LECO (TC-400) and the oxygen content in the product vanadium metal was determined to be 275 ppm.
Example 4
And 3, heating to 400 ℃, and drying for 24 hours under the vacuum-pumping condition.
And 5, carrying out pre-electrolysis by taking carbon as an anode and a molybdenum crucible as a cathode to remove impurities such as residual gas or metal in the molten salt.
Step 7, performing formal molten salt electrolysis by using the device shown in the attached figure 1: c is used as an anode, Mo is used as a cathode (38 mm is inserted), the electrolysis temperature is 850 ℃, the voltage is applied to 2.8V, and the electrolysis time is 100 ks.
And 8, stopping molten salt electrolysis after the molten salt electrolysis is finished, turning on the switch 5, starting the reduction reaction, and keeping for 10 hours to ensure that the reduction reaction is completely carried out.
And 9, after the reduction is finished, taking out the reduced small pieces, removing the residual molten salt on the surface of the chromium by vacuum distillation (the temperature is 950 ℃, the time is 3.7h, and the system pressure is 0.8Pa), and then cleaning by using a small amount of dilute hydrochloric acid (1+ 10). Finally, the oxygen content is measured by LECO (TC-400), and the oxygen content in the product metal chromium is 258 ppm.
Example 5
And 3, heating to 450 ℃, and drying for 24 hours under the vacuum-pumping condition.
And 5, performing pre-electrolysis by using carbon as an anode and a molybdenum crucible as a cathode to remove impurities such as residual gas and metal in the molten salt.
Step 7, performing formal molten salt electrolysis by using the device shown in the attached figure 1: c is used as an anode, Mo is used as a cathode (inserting 38mm), the electrolysis temperature is 770 ℃, the voltage is 2.7V, and the electrolysis time is 140 ks.
And 8, stopping molten salt electrolysis after the molten salt electrolysis is finished, switching on a switch, starting the reduction reaction, and keeping for 12 hours to ensure that the reduction reaction is completely carried out.
And 9, after the reduction is finished, taking out the reduced small pieces, removing the residual molten salt on the surface of the zirconium by vacuum distillation (the temperature is 950 ℃, the time is 3.7h, and the system pressure is 0.8Pa), and then cleaning by using a small amount of dilute hydrochloric acid (1+ 10). Finally, the oxygen content is measured by LECO (TC-400), and the oxygen content in the product metal zirconium is 321 ppm.
Example 6
And 3, heating to 450 ℃, and drying for 24 hours under the vacuum-pumping condition.
And 5, performing pre-electrolysis by using carbon as an anode and a molybdenum crucible as a cathode to remove impurities such as residual gas and metal in the molten salt.
Step 7, performing formal molten salt electrolysis by using the device shown in the attached figure 1: c is used as an anode, Mo is used as a cathode (inserting 38mm), the electrolysis temperature is 770 ℃, the voltage is 2.6V, and the electrolysis time is 140 ks.
And 8, stopping molten salt electrolysis after the molten salt electrolysis is finished, turning on the switch 5, starting the reduction reaction, and keeping for 12 hours to ensure that the reduction reaction is completely carried out.
And 9, after the reduction is finished, taking out the reduced small pieces, removing the residual molten salt on the surface of the niobium by vacuum distillation (at the temperature of 950 ℃, the time of 3.7h and the system pressure of 0.8Pa), and then cleaning by using a small amount of dilute hydrochloric acid (1+ 10). Finally, the oxygen content was measured by LECO (TC-400), and the oxygen content in the product niobium metal was measured to be 321 ppm.
Example 7
And 3, heating to 400 ℃, and drying for 24 hours under the vacuum-pumping condition.
And 5, performing pre-electrolysis by using carbon as an anode and a molybdenum crucible as a cathode to remove impurities such as residual gas and metal in the molten salt.
Step 7, performing formal molten salt electrolysis by using the device shown in the attached figure 1: c is used as an anode, Mo is used as a cathode (inserting 38mm), the electrolysis temperature is 900 ℃, the voltage is applied to 2.9V, and the electrolysis time is 140 ks.
And 8, stopping molten salt electrolysis after the molten salt electrolysis is finished, turning on the switch 5, starting the reduction reaction, and keeping for 8 hours to ensure that the reduction reaction is completely carried out.
And 9, after the reduction is finished, taking out the reduced small pieces, removing the residual molten salt on the surface of the molybdenum by vacuum distillation (the temperature is 950 ℃, the time is 3.7h, and the system pressure is 0.8Pa), and then cleaning by using a small amount of dilute hydrochloric acid (1+ 10). Finally, the oxygen content is measured by LECO (TC-400), and the oxygen content in the product metal molybdenum is 321 ppm.
Example 8
And 3, heating to 400 ℃, and drying for 24 hours under the vacuum-pumping condition.
And 5, performing pre-electrolysis by using carbon as an anode and a molybdenum crucible as a cathode to remove impurities such as residual gas and metal in the molten salt.
Step 7, performing formal molten salt electrolysis by using the device shown in the attached figure 1: c is used as an anode, Mo is used as a cathode (inserting 38mm), the electrolysis temperature is 900 ℃, the voltage is applied to 2.9V, and the electrolysis time is 150 ks.
And 8, stopping molten salt electrolysis after the molten salt electrolysis is finished, turning on the switch 5, starting the reduction reaction, and keeping for 9 hours to ensure that the reduction reaction is completely carried out.
And 9, after the reduction is finished, taking out the reduced small pieces, removing the residual molten salt on the surface of the tungsten by vacuum distillation (the temperature is 950 ℃, the time is 3.7h, and the system pressure is 0.8Pa), and then cleaning by using a small amount of dilute hydrochloric acid (1+ 10). Finally, the oxygen content is measured by LECO (TC-400), and the oxygen content in the product metal tungsten is 321 ppm.
Although the present invention has been described above in connection with exemplary embodiments, it will be apparent to those skilled in the art that various modifications and changes may be made to the exemplary embodiments of the present invention without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. A method for preparing low-oxygen metal by molten salt electrolysis-magnesiothermic reduction of metal oxide is characterized by comprising the following steps:
preparing a metal oxide precursor;
rare earth RE and excess MgCl2Placing in a reaction vessel, heating to melt to obtain MgCl2-RECl3Mixing molten salt;
in the mixed molten salt, C is used as an anode, Ti or W or Mo is used as a cathode to form a molten salt electrolytic cell, and molten salt electrolysis is carried out under the conditions that the temperature is 700-900 ℃ and the voltage is 2.4-3.0V so as to deposit metal Mg on the cathode;
and after the molten salt electrolysis is finished, stopping applying the voltage, communicating the metal oxide precursor in the mixed molten salt with the cathode deposited with the metal Mg to perform a reduction reaction, and obtaining the low-oxygen metal after the reduction reaction is finished.
2. A method of molten salt electrolysis-magnesiothermic reduction of metal oxides to produce low oxygen metals according to claim 1, wherein the metal oxides comprise titanium oxides, vanadium oxides, chromium oxides, zirconium oxides, hafnium oxides, tantalum oxides, niobium oxides, molybdenum oxides, and tungsten oxides.
3. A method of molten salt electrolysis-magnesiothermic reduction of metal oxide to low-oxygen metal according to claim 1 or 2, wherein preparing a metal oxide precursor comprises:
mixing metal oxide powder with an adhesive, and pressing and molding under the pressure of 600-750 MPa;
and sintering the pressed metal oxide at the temperature of 1000-1200 ℃ for 24-30 h to obtain the metal oxide precursor.
4. A method of molten salt electrolysis-magnesiothermic reduction of metal oxides to produce low oxygen metals according to claim 3, wherein press forming comprises pressing the metal oxide powders into a round cake shape of 15mm to 25mm diameter and 4mm to 8mm thickness.
5. A method for the preparation of a reduced oxygen metal by the molten salt electrolysis-magnesiothermic reduction of a metal oxide according to claim 1, 2 or 4, wherein MgCl is obtained2-RECl3The step of mixing the molten salt further comprises adding KCl and/or NaCl into the reaction vessel to obtain MgCl2-KCl-RECl3Mixed molten salt, MgCl2-NaCl-RECl3Mixed molten salts or MgCl2-KCl-NaCl-RECl3And (4) mixing the molten salt.
6. A method for the preparation of a reduced oxygen metal by the molten salt electrolysis-magnesiothermic reduction of a metal oxide according to claim 1, 2 or 4, wherein MgCl is obtained2-RECl3The step of mixing the molten salt further comprises:
for MgCl2Drying treatment is carried out;
placing rare earth RE and a predetermined amount of Ag at the bottom of a reaction vessel, and adding dried MgCl2Adding into a reaction vessel, sealing the reaction vessel and vacuumizing;
drying the reaction container in a vacuum environment at 350-450 ℃, and heating to melt to obtain MgCl2-RECl3And (4) mixing the molten salt.
7. A method of molten salt electrolysis-magnesiothermic reduction of metal oxides to produce low oxygen metals according to claim 1, 2 or 4 further comprising pre-electrolysis prior to molten salt electrolysis, the pre-electrolysis comprising pre-electrolysis of the mixed molten salt with C as anode and the reaction vessel as cathode.
8. A method of molten salt electrolysis-magnesiothermic reduction of metal oxides to produce low oxygen metal according to claim 1, 2 or 4, wherein the time of molten salt electrolysis is from 86 to 173 ks.
9. A method for preparing low-oxygen metal by molten salt electrolysis-magnesiothermic reduction of metal oxide according to claim 1, 2 or 4, wherein the reduction reaction time is 8-12 h.
10. A method of molten salt electrolysis-magnesiothermic reduction of metal oxides to produce low-oxygen metal according to claim 1, 2 or 4, wherein the step of obtaining low-oxygen metal further comprises:
taking out the reduction product in the reaction vessel after the reduction reaction is finished;
and (3) carrying out vacuum distillation on the reduction product for 3-5 h at the temperature of 850-1000 ℃ and under the pressure of 0.1-1 Pa to obtain the low-oxygen metal.
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| CN114016083A (en) * | 2021-11-05 | 2022-02-08 | 澳润新材料科技(宜兴)有限公司 | Method for regenerating alkali metal reducing agent in process of preparing metal by thermally reducing metal oxide with alkali metal |
| CN114192791A (en) * | 2021-12-15 | 2022-03-18 | 宁夏东方钽业股份有限公司 | Method for producing tantalum powder for capacitor by adopting alkaline earth metal to reduce tantalum oxide |
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| CN112828279A (en) * | 2020-12-31 | 2021-05-25 | 昆明理工大学 | Metal powder gas phase deoxidation method |
| CN114016083A (en) * | 2021-11-05 | 2022-02-08 | 澳润新材料科技(宜兴)有限公司 | Method for regenerating alkali metal reducing agent in process of preparing metal by thermally reducing metal oxide with alkali metal |
| CN114016083B (en) * | 2021-11-05 | 2023-11-03 | 澳润新材料科技(宜兴)有限公司 | Method for regenerating alkali metal reducing agent in process of preparing metal by alkali metal thermal reduction of metal oxide |
| CN114192791A (en) * | 2021-12-15 | 2022-03-18 | 宁夏东方钽业股份有限公司 | Method for producing tantalum powder for capacitor by adopting alkaline earth metal to reduce tantalum oxide |
| CN114192791B (en) * | 2021-12-15 | 2023-10-24 | 宁夏东方钽业股份有限公司 | Method for producing tantalum powder for capacitor by adopting alkaline earth metal to reduce tantalum oxide |
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| CN112011804B (en) | 2022-04-29 |
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