熔盐电化学的新进展

Figure Reduction of the TiO2 powder to titanium metal.
Chemical and material production from HTMS
• Electrowinning of molten Ti from TiO2 • Electrolyte CaF2 • Cathode Carbon • Anode Carbon • Temperature 1800oC
Using an electronconductive CaF2-CaO-based molten oxide in which TiO2 dissolved
Chemical and material production from HTMS
OS process
Chemical and material production from HTMS
The figure shows a polished cross-section of partially-reduced TiO2 material. A variety of microstructural features are observed, from the broad band of gold TiO at the sample surface, to an interior comprising a homogeneous mixture of fine gold TiO, purple Ti2O3 and beige CaTiO3 particles. In between the two regions are blocky, purple grains of Ti2O3, while bluish-white “starbursts” of CaTi2O4 are distributed throughout the transition and interior regions
– Cations
• 1-alkyl-3-methylimidazolium • N-methyl-Nalkylpyrrolidinium • tetraalkylammonium
Development of RTMS
高温熔盐（HTMＳ）
• Best known molten salts
– Na3AlF6-Al2O3 – LiCl-KCl eutectic melt – LiF-NaF-KF
• Applications
– Chemical and material production – Material tailoring – Energy conversion
Chemical and material production from HTMS
• Old topics
– Highly reactive metals, e.g. Al, Mg, Na, Li and rare earth metals – Electroplating of refractory metals, e.g. Ti, Zr, Nb, Ta, Mo and W
Derek Fray
Professor of Materials Chemistry University of Cambridge
Chemical and material produபைடு நூலகம்tion from HTMS
• The FFC process
– Electrolyte molten CaCl2 – Anode Carbon or inert anode – Cathode Pellets of TiO2
熔盐电化学的新进展 The Development of Electrochemistry of Molten Salts
高炳亮
内容
• 熔盐体系 – 室温熔盐(room temperature molten salt, RTMS) – 高温熔盐(> 200oC) • 熔盐电解新工艺 • 熔盐电池
室温熔盐（RTMS)
Chemical and material production from HTMS
Development of RTMS
• The first generation of RTILs
– aluminum halides (AlCl3) + alkylpyridinium or 1,3dialkylimidazolium types, eg. [NBupy]Cl-AlCl3, [emim]Cl-AlCl3 – Sensitivity to atmospheric moisture
– Electrodeposition of highpure Al and Al alloys – Electrodeposition of Transition metal– aluminum alloys, MAlx alloys (MCo, Ni, Fe, Cu and Ag) – Electrodeposition of semiconductors, Ga and As could be co-deposited from a GaCl3–EMIC melt containing AsCl3
• The FFC process • The process permits electrowinning of pure metals and alloys directly from their oxides by way of cathodic polarisation in a CaCl2-based molten salt electrolyte
Development of RTMS
• AlCl3–EMIC melts exhibit Lewis acidbase chemistry
– Cl-is a Lewis base – AlCl3 is a Lewis acid
Development of RTMS
• Applications of AlCl3–EMIC melts
• Titanium production by molten salt electrolysis • Titanium is currently produced by the Kroll process • Only calcium and rare earth metals can reduce the residual oxygen to less than 1,000 mass ppm
One reason the direct-reduction method using calcium could not be considered as a realistic process was the lack of an efficient method to remove the CaO film.
Development of RTMS
• The second generation of RTILs
– Water stable – Anions:
• tetrafluoroborate (BF4-) • hexafluorophosphate (PF6-) • bis(trifluoromethylsulfonyl)im ide [bistriflimide, N(Tf)2-
OS process K. Ono and R.O. Suzuki FFC process Fray-Farthing-Chen [FFC] process
Chemical and material production from HTMS
Electroslag refining (ESR) process
• 也称为室温离子液体（room temperature ionic liquid, RTIL） • A compound composed entirely of ions that exists in its liquid state at temperatures around 298K and below • high thermal stability, nonvolatility, high polarity, large viscosity, high intrinsic conductivity, wide electrochemical windows • K.R. Seddon estimate that, if binary and ternary mixtures are included, there are approximately one trillion (1018) accessible room temperature ionic liquids.
Chemical and material production from HTMS
• Titanium production by molten salt electrolysis
Electroslag refining (ESR) process
T. Takenaka et al.,and the Quebec Iron and Titanium Corporation
Review of RTMS
• Alkylammonium nitrate, [EtNH3][NO3], which has a melting point of 12 oC, was first described in 1914! • In the late 1970s, the field of modern ionic liquid chemistry took off when they were envisaged as lower-temperature alternatives for the molten alkali halide salts used as electrolytes in thermal batteries. • Throughout the 1980s, ionic liquid-based research was primarily of an electrochemical nature as these materials were employed as alternative solvents in which to explore the redox properties of a whole host of different inorganic, organometallic, and organic compounds. • With the advent of more air- and moisturestable RTILs however, the use of ionic liquids has expanded into many other fields including organic and inorganic synthesis, catalysis, polymerisation, and industrial applications, to the extent that in the present day they are regarded as one of the most promising greener alternatives to the volatile organic solvents currently in widespread use.
• New topics
– Titanium production by molten salt electrolysis – Electrorefining of Si from SiO2 in CaCl2 melt
Chemical and material production from HTMS