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

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 layer100 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

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.

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

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

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 .