TMS2008_oi_slide 1

Fundamental Study on Titanium Production Process by

Disproportionation Reactions of TiCl2in MgCl2 Molten Salt

Taiji Oi1 and Toru H. Okabe2

1 Department of Materials Engineering, The University of Tokyo, Japan.2 Institute of Industrial Science, The University of Tokyo, Japan.

TMS2008_oi_slide 2

Titanium

1. Light and high-strength2. Corrosion resistance3. Biocompatibility4. Some titanium alloys:

shape memory alloysuper elasticity

Features of Titanium

Titanium is the 9th most abundantelement in the earth’s crust !!

TMS2008_oi_slide 3

Huge exothermic reaction for the reduction→ Reduction rate is extremely slow.Batch type processe.g.) 10 days are required for producing 10 ton of Ti.

Overall reaction: TiO2 + C → Ti + CO2

Chlorination: TiO2 + C + 2Cl2 → TiCl4 + CO2

Reduction: TiCl4 + 2Mg → Ti + 2MgCl2Electrolysis: MgCl2 → Mg + Cl2

The Kroll Process

(+ )

A new production process is urgently required for further expansion of the applications of titanium metal.

TMS2008_oi_slide 44

MgCl2 (+ TiClx)

Fluidized bed chlorination

Rutile, Upgraded ilmeniteCalcined coke

Purification of TiCl4

CO, CO2

TiCl4

Vacuum distillation

Crude TiCl4 (+ VOClx, SiCl4, SnCl4)

VOClx, SiCl4,SnCl4

Production of TiCl2

Disproportionation of TiCl2

TiClx (+ MgCl2)

Ti powder (or Ti on Fe) (+ MgCl2,TiClx)

Scrap Ti

TiCl4

TiCl4This study

Ti powder (or Ti on Fe)

(Mg)(1) Production of TiCl2:

TiCl4 + Ti → 2 TiCl2TiCl4 + Mg → TiCl2 + MgCl2

(2) Disproportionation of TiCl2: 3 TiCl2 → Ti + 2TiCl32 TiCl2 → Ti + TiCl4

Flow chart of the proposed new Ti production process

TMS2008_oi_slide 55

Titanium Production Process by Disproportionation Reactions of TiCl2

(1) TiCl2 synthesis process: TiCl4 (g) + Ti (s, scrap) → 2 TiCl2 (s, l) TiCl4 (g) + Mg (l) → TiCl2 (s, l) + MgCl2 (l)

Step (2):Ti production by disproportionation of TiCl2 in MgCl2 molten salt

Step (1):High-efficient synthesisof TiCl2 in MgCl2 molten salt

MgCl2–TiCl2

TiCl4 Scrap Ti

MgCl2–TiCl2

TiCl4TiCl3

(2) Ti production process: 3 TiCl2 (s, l) → Ti (s) + 2TiCl3 (g)(2) Ti production process : 2 TiCl2 (s, l) → Ti (s) + TiCl4 (g)

Ti

TMS2008_oi_slide 66

Features of This Process◎High purity Ti products with low oxygen◎→ Chloride metallurgy◎Applicable to titanium coating method◎Utilizing titanium scrap for the feed

These problems can be solved by utilizing condensed phase like molten salt as a reaction medium.

Purpose of This Study

Development of (1) high-efficient TiCl2 synthesis process(2) Ti production process and/or Ti plating methodbased on disproportionation of TiCl2 in molten salt.

×Slow reaction speed in gas phase reaction×Still no efficient synthesis method of high-purity TiCl2

TMS2008_oi_slide 7

MgCl2 (+ TiClx)

Fluidized bed chlorination

Rutile, Upgraded ilmeniteCalcined coke

Purification of TiCl4

CO, CO2

Vacuum distillation

Crude TiCl4 (+ VOClx, SiCl4, SnCl4)

VOClx, SiCl4,SnCl4

Production of TiCl2

Disproportionation of TiCl2

TiClx (+ MgCl2)

Ti powder (or Ti on Fe) (+ MgCl2,TiClx)

Scrap Ti

TiCl4

TiCl4This study

Ti powder (or Ti on Fe)

(Mg)

(1) Production of TiCl2: TiCl4 (g)+ Ti (s) → 2 TiCl2 (l) in MgCl2 (l)

MgCl2–TiCl2

TiCl4 Scrap Ti

(1) TiCl2 synthesis by reaction of TiCl4 with Ti in Molten Salt

TMS2008_oi_slide 8[Komarek and P. Herasymenko: J. Electrochem. Soc. 105 (1958) p 210.]

MgCl2 TiCl2TiCl2 content, xTiCl2(mol%)

0 20 40 60 80 100

Tem

pera

ture

,T/ K

900

1000

1100

1200

1300 1298 K

L

989 K ?987 K

700

800

900

1000

Tem

pera

ture

,T’/

℃

0 20 40 60 80 100TiCl2 content, xTiCl2

(mass%)

Solubility at 1273 K: 83 mol% TiCl2

Nominal comp. of Exp. A

Nominal comp.of Exp. C and D

Experimental ProcedureQuasi-binary phase diagramfor the MgCl2–TiCl2 system

MgCl2 is expected to work as a medium that removes TiCl2 film formed on the surface of metallic Ti by dissolving it.

MgCl2 accumulates TiCl2 in its interior.

TiCl4(l, g) + Ti(s, scrap) → 2 TiCl2(s, l)

MgCl2–TiCl2

TiCl4 Ti

Nominal comp. of Exp. B

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Stainless-steelcontainer

Stainless-steel tubefor TiCl4 feed

Ti spongeMolten MgCl2

Stainless-steelbasket

TiCl4 (l, g) flowThermocouple (T2)

Thermocouple (T1)

Stainless-steelouter chamber

Alumina crucible

Heating element

10 mm

20 mm

TiCl2 Synthesis: Experimental

Experimental temperature, T1= 1273 KAr atmosphere

TMS2008_oi_slide 10

(a)

10 mm

Black flake precipitatewith green salt

Ti sponge residueafter experiment

(d)(e)

(b)(c)

Solidification of the salt

TiCl2 Synthesis: Experimental Results (1)

TMS2008_oi_slide 11

1/2 Cl2 (g)

1/3 MgCl2 (l) 1/3 TiCl2 (s)

Phase diagram for the Ti–Mg–Cl ternary systemat 1273 K

1/4 TiCl3 (g)

1/5 TiCl4 (g)

Ti (s)Mg (l) Ti (s)Ti (s)

MgCl2(l)－TiCl2(l)liquid line

C◦, D◦A◦ B◦A’ B’

C’,D’

TiCl2 Synthesis: Experimental Results (2)

Overall compositions of all the experiments wereclose to MgCl2-TiCl2(l) liquid line！

Nominal comp. before exp.

Overall comp. after exp.

○

□

△

D

●

■

▲

▼

A

B

C

△

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The efficiency of TiClx formation was improvedby using molten MgCl2 as a reaction medium.

Table Yield of TiClx and Ti consumption rate.

Direct reaction of TiCl4 with Ti*Yield of TiClx: 23~35%Consumption ratio of feed Ti: 42~45%

TiCl2 Synthesis: Experimental Results (3)

* Takeda et al., The 1st Workshop on Reactive Metal Processing (2006).

Yield of TiClx, RTiClx

(%)Ti consumption ratio, RTi' (%)

TiCl4 feed rate,r / g min-1

Exp.No.

84490.13A75600.65B84500.85C

94421.64D

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(2) Disproportionation of TiCl2:3 TiCl2 → Ti (s) + 2TiCl3 (g)2 TiCl2 → Ti (s) + TiCl4 (g)

MgCl2–TiCl2

Ti

TiClx

(2) Ti production by disproportionation of TiCl2 in MgCl2 molten salt

MgCl2 (+ TiClx)

Fluidized bed chlorination

Rutile, Upgraded ilmeniteCalcined coke

Purification of TiCl4

CO, CO2

Vacuum distillation

Crude TiCl4 (+ VOClx, SiCl4, SnCl4)

VOClx, SiCl4,SnCl4

Production of TiCl2

Disproportionation ofTiCl2

TiClx (+ MgCl2)

Ti powder (or Ti on Fe) (+ MgCl2,TiClx)

Scrap Ti

TiCl4

TiCl4

This study

Ti powder (or Ti on Fe)

(Mg)

TMS2008_oi_slide 1414

Disproportionation: Experimental

Experimental temperature, T = 1273 KReaction time, t = 3 or 6 hAr atmosphere

MgCl2–TiClx

Viton rubber stopper

Coolant inlet

Heating element

Stainless-steel chamber

Thermocouple

Alumina tube

Nickel crucible

Coolant outlet

Ti sponge 10 mm

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Disproportionation: Experimental Results (1)

(b)

Black chip with white powder

Solidification of the salt

10 mm

(a)

10 mm10 mm

Black sintered objectcoated by gold colored membrane

b-1 from top side b-2 from bottom side

TMS2008_oi_slide 16

a: Determined by X-ray fluorescence analysis (XRF); the value excludes carbon and gaseous elements.

Table Analytical results of the obtained samplesafter leaching.

0.301.001.36<0.0197.36Z(b)0.431.241.59<0.0196.76Z(a)0.150.090.53<0.0199.23Y(b)0.130.090.71<0.0199.13Y(a)CrNiFeMgTit / h

Concentration of element iin obtained Ti sample,

Ci (mass%)aTime,Exp.No.(position)

Titanium powder with a purity of over 99% was successfully obtained.

Disproportionation: Experimental Results (2)In

tens

ity, I

(a.u

.)

After leaching (Exp. Y(b))

:α-Ti, JCPDS: ♯44-1294.

40 60 80Angle, 2θ (degree, Cu Kα1)

XRD pattern of the sample obtained after leaching

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Disproportionation: Experimental Results (3)

Cationic molar fraction of titaniumin the MgCl2-TiCl2 salt was evaluated;

R = (1－ )×100

R = 49% (Exp. Y, 3 h)R = 87% (Exp. Z, 6 h)

ηTi

/ (η M

g＋

η Ti)

0.5

0.4

0.3

0.2

0.1

0

Disproportionation of TiCl2 in MgCl2 molten saltalmost finished by the reaction time of 6 h.

0 3 6Reaction time, t / h

xTi (after experiment)xTi (initial)

Initial

Exp. Y

Exp. Z

Cat

ioni

c m

olar

frac

tion

of T

i, x T

i,

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Conclusions

A high-efficient synthesis process for TiCl2and a production process for titanium metalwere investigated by using reactions in molten salt.

The efficiency of TiCl2 synthesis was improved when using molten MgCl2 as a reaction medium.

The feasibility of the titanium production processby disproportionation of TiCl2 in molten MgCl2was confirmed.