Research Subject 1
description
Transcript of Research Subject 1
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Research Subject 1Development of New Inorganic Membranes
• Membranes
– Ceramic membranes for H2 separation
– Ceramic membranes for CO2 separation
– Studies address mechanism of permeation• Prediction of permeation properties
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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
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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
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Cracking Infiltration
Smaller sol particles Larger sol particles
Incomplete coverageLarge spaces
Graded layers
Approach for a Thin, Defect-free Intermediate Layer
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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
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Scanning Electron Microscopy
Silica layer
Graded substrate
Support
1000 nm
High resolutionSiO2 layer(L = 20 nm)
-Al2O3 layer100 nm
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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
Sel
ectiv
ity
Per
mea
nce
/ mol
m-2 s
-1 P
a-1
Deposition time / h
H2
CH4
CO CO
2
a)
H
2/CH
4 H
2/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 H
2/CO
H2/CO2
Three-layer membrane
Y. Gu, S. T. Oyama, J. Membr. Sci. 2007, 306, 216.
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Comparison to Palladium
0 500 1000 1500 2000 25001E-8
1E-7
1E-6
H2 P
erm
eanc
e / m
ol m
-2 s
-1 P
a-1
Thickness / m
Our work Davis, et al. Holleck Balovnev Katsuta, et al. Morreale, et al.
PdMembranes
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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 MembranePermeation 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
( )16 2 8 ( )
KE RTs Ah kT h kT
N Nd h hQ eL h mkT IkT e e
P
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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
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Diffusion Energy Calculation
Model: Becke3lyp (DFT) Basis set: 6-311G(2d,p)x
y
z
Normal tothe xy plane
Saddle Point
Diffusion Energy
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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 .