Table 1. Conventional Methods of CO2 Separation.

Chemical Amine(Monoethanol amine, KS-1 3, Methyl diethanol amine) Aqueous K2CO3 solution Chilled-ammonia

Physical(under pressurizing)

Ionic liquid (Imidazolium compounds) Selexol process, Rectisol process

Absorption

Solid Absorbent Alkali metal compound Li-silicate) Alkali-earth metal comp.(hydrotalcite Mg6Al2 OH 16CO3 4H2O)

Adsorption Solid Adsorbent

Thermal swing of zeolite Meso-porous silica + amine Activated carbon, Carbon microbead, Carbon nano-tube

(amine coating, alkali adhesion)

Polymer membrane Polyimide, Polycarbonate, Polyphenylene oxide, etc. Polyacetylene membrane substituent

Multi-polymer membrane Polymer(with amine, carboxyl) multi-coated ultra membrane

Inorganic film Carbon, Silica, Zeolite, Ceramics

Facilitated transport mem. Porous polymer containing liquid

Membrane

Organic/inorganic mem. Inorganic materials dispersed in polymer

Liquefaction Separation by the difference of liquidus temperature

Distillation Separation by the difference of vaporization temperature Low temp. separation

Solidification Separation by the reaction of liquid gas with solid

Others Hydrate One CO2 molecule trapped in the basket consisted of 20(24 or 28) water molecules

Fig.1 Temperature dependence of log PCO2

at MxO/MxCO3 equilibrium.Fig.2 Temperature dependence of log PH2O

at M2O/MOH equilibrium.

-20

-10

10

0.5

logP

CO

2 / a

tm MgO

CaO

BaO

Li2O

Na2OK2O

m

m

M

m

1.0 1.5 2.0

103/T / K-1

3001500 1000 500

Temperature /

MxO + CO2 = MxCO3

M: Melting point of oxidem: Melting point of carbonate

0

-30

-20

-10

0

1 2 3

K2O

Na2O

Li2O

4

m: Melting point of hydrate

m

m

m

1000 500 0100

M2O(s) + H2O(g) = 2MOH

sat. at 20

103/T / K-1

logP

H2O

/ a

tm

Temperature /

Fig.3 Phase diagram of Li2O-TiO2 system10).

Fig.4 Weight change and reaction ratio of Li2O-TiO2 compounds plotted against temperature.

0 200 400 600 800 1000-10

0

10

20

30

Temperature /

Wei

ght c

hang

e / %

Li4TiO4

Li2TiO3

Li2CO3m.pt : 733 5)

0

50

100

Rea

cted

ratio

/ %

20 m

20 m

a)

b)

Fig.5 SEM images of Li4TiO4 sample before reaction (a) and after heating up to 600ºC in CO2 (b).

10 m

Fig.6 SEM images of Li4TiO4 sample after heating up to 800ºC in CO2.20 m 10 m

10 20 30 40 50 60 70

X-r

ay in

tens

ity

2 / deg.

Before

After

10

20

30 40 50 60 70

X-r

ay in

tens

ity

2 / deg.

Before

After

Fig.7 Comparison of X-ray characteristic peaks before and after heating at 600ºC in CO2 for 4 h.

Fig.8 Comparison of X-ray characteristic peaks before and after heating at 800ºC in CO2 for 4 h.

Fig.9 Effect of grain size of Li4TiO4 on its weight change in CO2.

200~250 m

1 mm 100 m 20 m

1 mm 100 m

53 m

20 m

1 mm 100 m 20 m

100~150 m

Fig.10 SEM images of classified Li4TiO4 particles after heating up to 1100ºC in CO2.

0

10

20

30

0 200 400 600 800 1000

Temperature /

Wei

ght c

hang

e / % 53 m

100 150 m200 250 m

CO2 100%

1 mm 100 m

Fig.11 Influence of CO2 partial pressure on CO2 adsorption and desorption of Li4TiO4.

Fig.12 SEM images of the surface of Li4TiO4 samples after heating up to 1100ºC in Ar-10%CO2.

0 200 400 600 800 1000

0

10

20

30

Temperature /

Wei

ght c

hang

e / %

100%CO210%CO2

JFE21

Wei

ght c

hang

e /

%

Tem

pera

ture

/ o C

0 100 2000

500

1000

1500

Time / min

0

10

20

Fig.13 Variation of Li4TiO4 weight in cycle test of CO2 adsorption and desorption in Ar-10% CO2.