FFC Cambridge process

A process for electrochemical production of titanium through the reduction of titanium oxide in a calcium chloride solution was first described in a 1904 German patent,{{cite journal|last1=Takeda|first1=O.|last2=Ouchi|first2=T.|last3=Okabe|first3=T. H. |year=2020|title=Recent Progress in Titanium Extraction and Recycling |journal=Metall. Mater. Trans. B|volume= 51|issue=4 |pages= 1315–1328|doi=10.1007/s11663-020-01898-6|doi-access=free|bibcode=2020MMTB...51.1315T }}{{Cite patent|number=DE150557C|title=Publication of DE150557C|url=https://patents.google.com/patent/DE150557C/en}}{{cite book |last1=Rideal |first1=Eric Keightley |url=https://archive.org/details/industrialelect00ridegoog |title=Industrial Electrometallurgy, Including Electrolytic and Electrothermal Processes |publisher=D. Van Nostrand co. |year=1919 |page=137}} and in 1954 {{US patent|2845386A}} was awarded to Carl Marcus Olson for the production of metals like titanium by reduction of the metal oxide by a molten salt reducing agent in a specific gravity apparatus.{{Cite patent|number=US2845386A|title=Production of metals|gdate=1958-07-29|invent1=Marcus|inventor1-first=Olson Carl|url=https://patents.google.com/patent/US2845386A/en/}}

The FFC Cambridge process was developed by George Chen, Derek Fray, and Thomas Farthing between 1996 and 1997 at the University of Cambridge. (The name FFC derives from the first letters of the last names of the inventors).{{Cite journal | doi = 10.1038/35030069| pmid = 11014188| year = 2000| last1 = Fray | first1 = D. J. | title = Direct Electrochemical Reduction of Titanium Dioxide to Titanium in Molten Calcium Chloride| journal = Nature| volume = 407| issue = 6802| pages = 361–4| last2 = Chen | first2 = G. Z. | last3 = Farthing | first3 = T. W. | bibcode = 2000Natur.407..361C| s2cid = 205008890}} The intellectual property relating to the technology has been acquired by Metalysis, (Sheffield, UK).{{Citation needed|date=March 2022}}

The process typically takes place between 900 and 1100 °C, with an anode (typically carbon) and a cathode (the oxide being reduced) in a solution of molten CaCl₂. Depending on the nature of the oxide it will exist at a particular potential relative to the anode, which is dependent on the quantity of CaO present in CaCl₂.

The electrocalciothermic reduction mechanism may be represented by the following sequence of reactions, where "M" represents a metal to be reduced (typically titanium).

: (1) {{chem|MO|x| + x Ca → M + x CaO}}

When this reaction takes place on its own, it is referred to as the "calciothermic reduction" (or, more generally, an example of metallothermic reduction). For example, if the cathode was primarily made from TiO then calciothermic reduction would appear as:

: {{chem| TiO + Ca → Ti + CaO}}

Whilst the cathode reaction can be written as above it is in fact a gradual removal of oxygen from the oxide. For example, it has been shown that TiO₂ does not simply reduce to Ti. It, in fact, reduces through the lower oxides (Ti₃O₅, Ti₂O₃, TiO etc.) to Ti.

The calcium oxide produced is then electrolyzed:

: (2a) {{chem| x CaO → x Ca²⁺ + x O²⁻}}

: (2b) {{chem|x Ca²⁺ + 2x e⁻ → x Ca}}

and

: (2c) {{chem|x O²⁻ → x/2 O₂ + 2x e⁻}}

Reaction (2b) describes the production of Ca metal from Ca²⁺ ions within the salt, at the cathode. The Ca would then proceed to reduce the cathode.

The net result of reactions (1) and (2) is simply the reduction of the oxide into metal plus oxygen:

: (3) {{chem|MO|x| → M + x/2 O₂ }}

The use of molten CaCl₂ is important because this molten salt can dissolve and transport the "O²⁻" ions to the anode to be discharged. The anode reaction depends on the material of the anode. Depending on the system it is possible to produce either CO or CO₂ or a mixture at the carbon anode:

:{{chem| C + 2O²⁻ → CO₂ +4 {{SubatomicParticle|electron}}}}

:{{chem| C + O²⁻ → CO + 2 {{SubatomicParticle|electron}}}}

However, if an inert anode is used, such as that of high density SnO₂, the discharge of the O²⁻ ions leads to the evolution of oxygen gas. However the use of an inert anode has disadvantages. Firstly, when the concentration of CaO is low, Cl₂ evolution at the anode becomes more favourable. In addition, when compared to a carbon anode, more energy is required to achieve the same reduced phase at the cathode. Inert anodes suffer from stability issues.

: {{chem| 2O²⁻ → O₂ + 4 {{SubatomicParticle|electron}}}}

{{reflist}}

• {{cite journal|author1=R. Bhagat |author2=M. Jackson |author3=D. Inman |author4=R. Dashwood |title =Production of Ti-Mo Alloys from Mixed Oxide Precursors via the FFC Cambridge Process|journal = J. Electrochem. Soc.|year = 2008|volume = 155|issue = 6|pages = E63–69|doi = 10.1149/1.2904454|bibcode=2008JElS..155E..63B }}
• {{cite journal|author1=R. Bhagat |author2=M. Jackson |author3=D. Inman |author4=R. Dashwood |title =Production of Ti-W Alloys from Mixed Oxide Precursors via the FFC Cambridge Process|journal = J. Electrochem. Soc.|year = 2009|volume = 156|issue = 1|pages = E1–7|doi = 10.1149/1.2999340|bibcode=2009JElS..156E...1B |url = http://wrap.warwick.ac.uk/28972/}}
• {{cite journal|title = Calciothermic reduction of TiO₂ and in situ electrolysis of CaO in the molten CaCl₂|author = Ryosuke O. Suzuki|journal = Journal of Physics and Chemistry of Solids|volume = 66|issue = 2–4|date = February–April 2005|pages = 461–465|doi = 10.1016/j.jpcs.2004.06.041|bibcode = 2005JPCS...66..461S }}
• {{cite journal|title = Production of titanium powder directly from TiO₂ in CaCl₂ through an electronically mediated reaction (EMR)|author1=Il Park |author2=Takashi Abiko |author3=Toru H. Okabe |journal = Journal of Physics and Chemistry of Solids|volume = 66|issue = 2–4|date = February–April 2005|pages = 410–413|doi = 10.1016/j.jpcs.2004.06.052|bibcode = 2005JPCS...66..410P }}
• {{cite journal|author1=X. Ge |author2=X. Wang |author3=S. Seetharaman |title = Copper extraction from copper ore by electro-reduction in molten CaCl₂–NaCl |journal = Electrochimica Acta |year = 2009|volume = 54|issue = 18|pages = 4397–4402 |doi = 10.1016/j.electacta.2009.03.015}}

• [https://www.youtube.com/watch?v=97dfa1GoF7w YouTube video:Metalysis FFC process]
• [https://www.metalysis.com Metalysis Ltd. website]

{{DEFAULTSORT:Ffc Cambridge Process}}

Category:Chemical processes

Category:Electrochemistry

Category:Titanium processes