1. No category

Mork Family Department of Chemical Engineering and Materials Science
2006 Student Symposium
The Preparation and Characterization
of Hydrotalcite Membranes
Taewook Kim (Ph.D. Candidate)
Advisors: Muhammad Sahimi and Theodore Tsotsis
Global warming is caused by greenhouse gases such as CO2, CH4, NOx.
Development of stable Mg-Al-CO3
hydrotalcite microporous membranes
with high CO2 selectivity
Biggest challenge: CO2 separation technology.
(PSA, distillation, membrane technology)
Hydrotalcite
Novel inorganic membranes can be applied
under harsh conditions.
M(OH)2
Brucite-like layers
▶ Higher CO2 adsorption capacity
at high temperatures
▶ Good thermal stability
▶ Easy to regenerate
Interlamellar
doamins
[MIIII1-xMMIIIIIIx(OH)
(OH)2]x]+x+[X
[Xm-m-x/mnH
nH2O]
O]x-x[M
2
2
1-x
x
x/m
Two different types of membranes have been prepared:
Electrophoresis: colloids travel
through a fluid in response to
an applied electric field
■ Large-area membranes prepared by dip-coating, EPD (Electrophoretic
deposition), and vacuum suction (w/ silicon treatment) methods on
alumina discs or tubes .
■ Micro-membranes prepared on Si-wafers and stainless-steel discs.
Adding the HT
Etching
with KOH
-w/, w/o sublayer
(γ-alumina)
HT coated Si
HT Membrane
Micromembrane process
MG70Dcoat
Mg70Dparticle
4000
3500
α− alumina peak
3000
Intensity
Silicon treatment
HT + γ-Alumina
coating
Silicon
wafer
silicon layer
HT layer
HT peak
2500
5㎛
2000
1500
1000
HT layer
500
0
10 ㎛
-500
10
20
30
40
2θ
50
60
70
Micromembrane
XRD spectra
Micromembrane
8.0E-09
8.0E-09
Permeance
Permeance
(mol/m22sec
secPa)
Pa)
(mol/m
6.0E-09
6.0E-09
Memb
4.0E-09
4.0E-09
CO2
Ar
1.0E-11
1.0E-11
2.5
2.5
ddk (Ǻ
)
k (Ǻ )
33
∆P
30psi
N2
2.0E-09
2.0E-09
22
Gas
(MW)
Permeance ×
10-8 (mol/m2 s
Pa)
3.5
3.5
44
Permeance order : He> CO2>N2>Ar
Su
#1
He(4)
5.292
N2 (28)
1.18
Ar (40) 0.873
CO2 (44) 0.611
X 5K
Vacuum suction membrane
(before and after silicon treatment)
Silicon treatment
Vacuum-suction membrane
Perm
Permenace
enace
He
10 ㎛
X 5K
Permselectivity
∆P
He/gas
Experimental
Result
40 psi
Ideal
Knudsen
value
30 psi
40 psi
4.93
1.0
1.0
1.0
1.24
0.883
0.604
2.65
3.16
3.32
4.52
6.08
8.72
3.96
5.60
8.15
(psi)
Before coating
40
After coating
Gas
Permeance
30
Permeance [× 10-9 (mol/m2 s Pa)]
N2
26.5
CO2
18.1
N2
24.9
CO2
17.5
CO2/
N2
Permeance
0.0159±0.0014
0.68
0.494±0.002
0.70
0.0165±0.0013
0.450±0.008
Permeance order : He> N2>Ar>CO2
CO2/
N2
silicon-coated
on alumina
membrane
Permeance
31.1±
2.5
0.204
27.3±
1.8
0.204
CO2/
N2
9.6
1.97
10.0
2.04
Permeance order : CO2> H2>He>N2
□ A number of techniques have been developed and studied for the preparation of HT membranes.
□ Different membranes have been tested for their permeation characteristics towards single gases and their mixtures.
□ A number of the membranes were shown to be nanoporous, with some of them showing permselectivity towards CO2.
The support of the U.S. Department of Energy is gratefully acknowledged.