research subject 1 development of new inorganic membranes membranes – ceramic membranes for h 2...
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Research Subject 1
Development of New Inorganic Membranes
• Membranes
– Ceramic membranes for H2 separation
– Ceramic membranes for CO2 separation
– Studies address mechanism of permeation• Prediction of permeation properties
New Silica Membranes
Alumina support(Pall Corporation, pore size 100 nm)
Si(C2H5O)4
(TEOS) SiO2 membrane
(Nanosil)
Thermal CVD(873 K)
Connected by glass joints
Dense alumina tubingPorous support
1 cm
Experimental Equipment for CVD
4 cm
CVD condition : 873 K, 1 atm(0.07 mol % of TEOS)
Mass FlowController
ATSB
Oil Bath
Balance Gas
Dilution Gas
Furnace
Membrane
Carrier Gas
Vent
Oxygen & WaterTrap
MFC
MFC
MFC
Vent
TemperatureController
TEOS
Water Bath
MFC
Heating Tape
Al
O
O
sec-Bu
sec-Bu
ATSB
sec-BuO
Si
O
O
O
CH2CH3
CH3CH2 O CH2CH3
CH2CH3
TEOS
Cracking Infiltration
Smaller sol particles Larger sol particles
Incomplete coverageLarge spaces
Graded layers
Approach for a Thin, Defect-free Intermediate Layer
Sol Processing & Particle Size Distributions of Sols
•Lower acidity produces larger particle sizes
H+/Al alkoxideAluminum alkoxide
Stirring & heating
Acid
Water
Hydrolysis
Peptization
Clear Boehmite Sol
Refluxing
-Al2O3 Layers
Calcination
Al(OR)3 + H2O
Al(OH)3
-(O-Al-O-Al)x
AlOOH colloidal particles
Scanning Electron Microscopy
Silica layer
Graded substrate
Support
1000 nm
High resolutionSiO2 layer(L = 20 nm)
-Al2O3 layer
100 nm
Permeability and Selectivity ofNanosil Membranes
P = 5 x 10-7
S > 99.9%
0 1 2 3 4 51E-11
1E-10
1E-9
1E-8
1E-7
1E-6
1E-5
1E-4
0 1 2 3 4 51
10
100
1000
Se
lect
ivity
Pe
rme
an
ce /
mo
l m-2 s
-1 P
a-1
Deposition time / h
H2
CH4
CO CO
2
a)
H
2/CH
4
H2/CO
H2/CO
2
Two-layer membrane
0 1 2 31E-11
1E-10
1E-9
1E-8
1E-7
1E-6
1E-5
1E-4
0 1 2 31
10
100
1000
10000
Sel
ectiv
ity
Per
mea
nce
/ mol
m-2s-1
Pa-1
Deposition Time / h
H2
CH4
CO CO
2
b)
H2/CH
4
H2/CO
H2/CO
2
Three-layer membrane
Y. Gu, S. T. Oyama, J. Membr. Sci. 2007, 306, 216.
Comparison to Palladium
0 500 1000 1500 2000 25001E-8
1E-7
1E-6
H2
Pe
rme
an
ce /
mo
l m-2 s
-1 P
a-1
Thickness / m
Our work Davis, et al. Holleck Balovnev Katsuta, et al. Morreale, et al.
PdMembranes
Statistical Model
Key parameters: * = vibrational frequency
d = jump distance
ΔEk
Ns = number of solubility sites
Permeation occurs by jumps between adjacent solubility sites
Translation Rotation Vibration
Membrane Membrane
Permeation equation:
S. T. Oyama , D. Lee, P. Hacarlioglu, R. F. Saraf, J. Membr. Sci., 2004, 244, 45.Y. Gu, S. T. Oyama, Adv. Mater. 2007, 19, 1636
* *
32 2 22
2 2 2 2
( )1
6 2 8 ( )KE RTs A
h kT h kT
N Nd h hQ e
L h mkT IkT e e
P
Structure of Pd-Cu Membrane (5 nm)
Low resolution (20 k X) High resolution (100 k X)
Pd-Cu
Intermediatelayer
- alumina support (5 nm pore)
Dip coating of one intermediate layer
Electroless plating of Pd-Cu
Diffusion Energy Calculation
Model: Becke3lyp (DFT) Basis set: 6-311G(2d,p)x
y
z
Normal tothe xy plane
Saddle Point
Diffusion Energy
Activation Energy vs. Distance to O atoms
0.20 0.24 0.28 0.32 0.36 0.400.1
1
10
100
1000
A
ctiv
atio
n E
nerg
y / k
J m
ol-1
Center to Oxygen Distance / nm
Hydrogen
Helium
8-membered
4-membered
5-membered
6-membered
7-memberedGlasses
Silica layer
P. Hacarlioglu, D. Lee, G.V. Gibbs and S.T. Oyama, J. Membr. Sci. 2008, 313, 278-283 .