Studying Zeolitic Diffusion by Interference and IR Microscopydiffusion.uni-leipzig.de/projects/irg_col_2006/Kaerger.pdf · Extension for the Period from 2006-2009 0 10 203040 50 0.0

Package of Research Projects ”Diffusion in Zeolites”by CNRS (France), DFG (Germany), EPSRC (United Kingdom), NSF (USA)

Extension for the Period from 2006-2009

Studying Zeolitic Diffusion by Interference and IR Microscopy

Studying Zeolitic Diffusion by Interference and IR Microscopy

Jörg KärgerSergey Vasenkov (Gainesville, University of Florida)

Pavel Kortunov (Exxon-Mobil)Christian Chmelik

DB Shah (Cleveland University)Lars Heinke

Despina Tzoulaki

Project 5



What do we measure?What do we measure?

Pulsed Field Gradient (PFG) NMR

<r2(t)> = 2D tr(t)

self-diffusion

Interference Microscopy (IFM)

j = – D(T) grad c j

transport diffusion



Adsorption system and cyclesAdsorption system and cycles2. Preparation for adsorption1. Pumping / Activation

T=4000C

3. Adsorption4. Preparation for desorption



IFM TechniqueIFM Technique

Spatial resolution: 0.5 μm × 0.5 μm

L

0)0(

2ϕ)0(1ϕ

)(1

Lϕ )(2

Lϕ0)( ≠Δ Lϕ

0)0( =Δϕ

Δφ ~ Δn ~ Δc

n1 n2



OutlineOutline

y

xz

(a) 1-D pore structure of the MOF crystals

(b) 2-D pore structure of the Ferrierite zeolite

z

y

x

Dy

Dx

Dz

(c) 3-D pore structure of the SAPO STA-7



(*) D.N. Dybtsev, H. Chun, S.H. Yoon, D. Kim and K. Kim; J. Am. Chem. Soc., 2004, 126, 32-33

y

xz

1-D pore structure of MOF crystal (*)

0 20 40 60 80 100

0.0

0.2

0.4

0.6

0.8

1.0

Methanol adsorption 0 → 10 mbar into MOF crystal

√t , s1/2

Rel

ativ

e co

ncen

tratio

n

fitting by diffusion resistance model

Davarage = 1.05 × 10-12 m2/s

Macroscopic adsorption techniques:

Interference microscopy technique:



0 10 20 30 40 500.0

0.2

0.4

0.6

0.8

1.0

gas

phas

e ou

tsid

e of

the

crys

tal

gas

phas

e ou

tsid

e of

the

crys

tal

space of the crystal

400 sec

310 sec

250 sec

190 sec

130 sec

70 sec

50 se

c

Δ(Δc/Δx)/Δx

Δc/Δt

Δc/Δx

10 se

c

Methanol adsorption into MOF crystal

x , μm

Con

cent

ratio

n

before 0 sec

ceq- c(t)

y

xz

Surface PERMEABILITY

46 48 50 520.7

0.8

0.9

1.0

Con

cent

ratio

n

x , μm

ceq- c(t)

Δc/Δx ≈ dc/dx

3 6 9 12 150.3

0.4

0.5

0.6

0.7

Con

cent

ratio

n

x , μm

Δ(Δc/Δx)/Δx ≈ d 2C/dx 2

Δc/Δt ≈ dC/dt

Local DIFFUSION

First and second Fick‘s laws



1-D diffusion in the MOF crystal

Local DIFFUSION(microscopic analysis)

πDta

cccct 2

0

0 ≈−−

∞

Average DIFFUSION(macroscopic analysis)



OutlineOutline

y

xz



z

y

x

Dy

Dx

Dz




2-D pore structure of Ferrierite crystals



Directions of methanol adsorption in Ferrierite crystal



Fick’s Second Law:

0 10 20 30 40 50

0.0

0.2

0.4

0.6

0.8

1.0

t = 2250 sec

t = 1650 sec

t = 1100 sec

t = 750 sec

t = 400 sec

t = 230 sec

t = 110 sec

t = 30 sec

Δ(Δc/Δx)/Δx

M

olec

ular

con

cent

ratio

n

y, μm

Adsorption of Methanol (0 → 5 mbar) into Ferrierite

Δc/Δt

t = 0 sec5 10 15

0.2

0.4

0.6 Δ(Δc/Δx)/Δx ≈ d 2c/dx 2

Δc/Δt ≈ dc/dt

Fick’s First Law:x = 24 μm

Local diffusion and surface resistance



0.0 0.2 0.4 0.6 0.8 1.010-13

10-12

10-11

0.0 0.2 0.4 0.6 0.8 1.0

10-3

10-2

10-1

100

Desorption 5 → 0 mbar Desorption 10 → 0 mbar

Desorption of Methanol from Ferrierite

Diff

usiv

ity ,

m2 s-1

Norm. concentration

P

erm

eabi

lity

×10-6

, m s

-1

0 10 20 30 40 50

0.0

0.2

0.4

0.6

0.8

1.0

experimental points calculation using D(c) and α(c)

t = 1950 sect = 1350 sec

t = 900 sec

t = 600 sec

t = 400 sec

t = 3450 sect = 7350 sec

t = 210 sec

t = 90 sec

t = 30 sec

y , μm

Desorption Methanol (10 → 0 mbar) from Ferrierite

Con

cent

ratio

n

beforet = 0 sec

TESTLocal DIFFUSION

Concentration dependence of the molecular diffusivity



y

xz



z

y

x

Dy

Dx

Dz


OutlineOutline



3-D pore structure of STA-7 materials (*)

z

y

x

Dy

Dx

Dz

(*) Paul A. Wright, Martin J. Maple et al., J. Chem. Soc., Dalton Trans., 2000, 1243–1248



3-D pore structure of STA-7 materials

z

y

x

Dy

Dx

Dz



0 5 10 15 20 25

0.0

0.2

0.4

0.6

0.8

1.0

C(y

)=∫ C

(x,y

,z20

μm) d

x

t = 70 sec

before adsorptiont = 0 sec

y , μmx , μm

y , μm

22.5

0 22.5

t = 70 sec

Uptake in y- and x-directions

z

y

x

0 5 10 15 20 25

0.0

0.2

0.4

0.6

0.8

1.0


C(y

)=∫ C

(x,y

,z20

μm) d

x

t = 10 sec

y , μmx , μm

y , μm

22.5

0 22.5

t = 10 secjy

jx

0 5 10 15 20 25

0.0

0.2

0.4

0.6

0.8

1.0

C(y

)=∫ C

(x,y

,z20

μm) d

x


y , μmx , μm

y , μm

22.5

0 22.5

t = 0 sec

0 5 10 15 20 25

0.0

0.2

0.4

0.6

0.8

1.0


C(y

)=∫ C

(x,y

,z20

μm) d

x

t = 30 sec

y , μmx , μm

y , μm

22.5

0 22.5

t = 30 secjy

jx

0 5 10 15 20 25

0.0

0.2

0.4

0.6

0.8

1.0

C(y

)=∫ C

(x,y

,z20

μm) d

x

equilibriumt = 18 min

t = 350 sec

t = 170 sec

t = 30 sec

t = 70 sect = 50 sec

t = 10 sec


y , μm



thermo isolated box

IFM perspectives…IFM perspectives…

P2

P1

vacuumpump

ampoulewith liquid

large tank

optical cell

additionalentrance

interference microscope

thermo isolated box

heater/cooler

Tmax = 1000C (2040C)

Tmin = 00C (-500C)

Documents

Studying Zeolitic Diffusion by Interference and IR Microscopydiffusion.uni-leipzig.de/projects/irg_col_2006/Kaerger.pdf · Extension for the Period from 2006-2009 0 10 203040 50 0.0