•ULTRAVIOLET-VISIBLE-NEAR INFRARED (UV-VIS-NIR) SPECTROSCOPY •ELECTRON PARAMAGNETIC RESONANCE (EPR) or ELECTRON SPIN RESONANCE (ESR) OF ZEOLITES Robert A.
Download ReportTranscript •ULTRAVIOLET-VISIBLE-NEAR INFRARED (UV-VIS-NIR) SPECTROSCOPY •ELECTRON PARAMAGNETIC RESONANCE (EPR) or ELECTRON SPIN RESONANCE (ESR) OF ZEOLITES Robert A.
Slide 1
•ULTRAVIOLET-VISIBLE-NEAR INFRARED
(UV-VIS-NIR) SPECTROSCOPY
•ELECTRON PARAMAGNETIC RESONANCE (EPR)
or ELECTRON SPIN RESONANCE (ESR)
OF ZEOLITES
Robert A. SCHOONHEYDT
Center for Surface Chemistry and Catalysis
K.U. Leuven
Kasteelpark Arenberg 23, 3001 Leuven
Belgium
[email protected]
Slide 2
OUTLINE
1. Principles of UV-VIS-NIR
- physical basis
- methodology
2. In-situ UV-VIS
3. Optical and fluorescence microscopies
4. Principles of EPR
- physical basis
- methodology
5. In-situ EPR
6. Pulse EPR
7. Coordination of transition metal ions (TMI)
8. Conclusions
Slide 3
UV-VIS-NIR
Wavelength nm
Wavenumber
Frequency
cm-1
Hz
200
375
750
2500
50000
26664
13300
4000
8x1014
4x1014
1.2x1014
1.5x1015
UV
VISIBLE
NIR
Slide 4
What do we measure ?
Molecules: unsaturated
* and
n * transitions
Energy level diagramme
n π *
Antibonding
n *
π*
π π *
Antibonding
*
*
π
Nonbonding
π
Bonding
Bonding
Slide 5
Transitions Metal Ions
d – d transitions
Ligand- to Metal Charge Transfer
(LMCT)
Slide 6
Transitions Metal Ions
d – d transitions
Metal - to Ligand Charge Transfer
(MLCT)
example: [Cr(benzene)2]+
Slide 7
UV - VIS - NIR: Methodology
Powdered samples Diffuse Reflectance Spectroscopy (DRS)
Principle
x
I0
J0
I
J + J
x
I + I
J
Slide 8
Ideal Case: Kubelka – Munck formula
F R
1 R 2
2 R
K
kc
S
scattering intensity from infinitely thick sample
R∞ =
scattering intensity from infinitely thick white standard
K : Kubelka-Munck absorption coefficient
S : Kubelka-Munck scattering coefficient
Slide 9
Conditions for use of K M-formula
•diffuse monochromatic irradiation
•isotropic scattering
•infinite sample thickness
•low concentration of absorbing centers
•uniform distribution of absorbing centers
•absence of fluorescence
Slide 10
UV – VIS – NIR: instrumentation
•Every compagny has a UV-VIS-NIR spectrophotometer with
two sources ( Nerst glower, D2 lamp) and two detectors (PbS, PM).
•Integration sphere for DRS
•White standards: MgO, BaSO4, HALON.
Slide 11
IN – SITU UV-VIS-NIR
Praying Mantis
Optical fibre technology
O ptic al fib er
H ig h-tem p. pr ob e
hn
F low in
U V - vis s ourc e
O ven
R eac tor
C atalys t b ed
Gas inlet
M u lti-c h ann el
d etec tor
C om pu ter
Gas outlet
Most sensitive region: VISIBLE
low background
sensitive detection: PM
Q u artz w ool
GC
F low out
Slide 12
IN – SITU UV-VIS-NIR
Examples:
d d (pseudo)tetrahedral Co2+
O Cr6+ charge transfer (chromate, dichromate)
O Cu2+ bis(µ-oxo)dicopper
Slide 13
Microporous crystalline metal-containing
Aluminiumphosphates:isomorphous substitution
O
O
-1
Al
O
O
-2
Co
O O
O
Al
O
O
O
Co2+
O
+1
O
-1
P
O
O
-1
P
O
Isomorphous
substitution
O
O
+1
Al
O
O
O
AlPO4-5
AFI
Slide 14
CoAPO-5: in situ synthesis
synthesis C oAPO -5
2.2
1.8
1.6
absorbance
Absorbance
2.0
24u
1.4
16u
1.2
1.0
0.8
0.6
0u
25°c
0.4
500
1000
1500
2000
wavelength
Wavelength (nm)
Synthesis time
2500
Slide 15
CoAPO-5 synthesis: spectra at RT
Slide 16
Chromate reduction with CO in zeolite Y
Slide 17
bis( µ-oxo )dicopper in ZSM-5
C Z -3 1 -0 .1 6
C Z -3 1 -0 .3 4
a b s o rp tio n (a .u .)
C Z -3 1 -0 .5 8
10000
20000
30000
40000
-1
w a ve n u m b e r (cm )
50000
Slide 18
OPTICAL and FLUORESCENCE MICROSCOPIES
Slide 19
Intergrowth structure of ZSM-5
Accessibility?
Slide 20
Applications
Oligomerization of furfurylalcohol in ZSM-5 and mordenite
Slide 21
Applications
Oligomerization of styrene in ZSM-5
+
H+
R
R
+
R
R
+
+
R
R
R R
B
R
B
A
R
D
T rim e tric o lo g o m e rs
E
Slide 22
oligomerization of styrene: absorption spectra
Slide 23
Decomposition of template molecules in CrAPO-5
Slide 24
Decomposition of template molecules and intergrowth structures
CrAPO-5
SAPO-34
SAPO-5
ZSM-5
Slide 25
ELECTRON PARAMAGNETIC RESONANCE
magnetic moment of the unpaired elelctron
µ g S 2h S
µ
z
g S
z
2h S
z
S = dimensionless spin angular momentum vector of the electron
S2 = s(s+1) s = ½
SZ =ms ms = 1/2, -1/2
e h 9 ,2741 x10 24 JT 1
= Borhmagneton
2me
g, spectroscopic splitting factor = 2.0023
ħ = h/2π
γ = gyromagnetic ratio
Slide 26
ZEEMAN INTERACTION
EZ = -µZB0 = gβB0ms
ms = ½: 1/2g βB0
ms = -½: -1/2g βB0
E
ms = 1/2
E = gβB0
ms = - 1/2
B0
Resonance condition: hν = E = gβB0
Slide 27
EPR: powder spectra
All possible orientations of the spins
Each orientation has its own resonance condition
Spectra are superpositions of all those individual spectra
isotropic
axially symmetric
orthorhombic
Slide 28
EPR: Measurement of g values
measurement at constant frequency and varying magnetic field
Band name
band range, GHz
L
S
C
X
K
Q
V
W
g=
hn
B
1.5
2.6-4
4-6
8.2-12.4
18-26.5
33-50
50-75
75-100
= 7,145x10-9 ν/B0
to be measured with gaussmeter
0
to be read from microwave bridge
reference: DPPH gr = 2,0036 (diphenylpicrylhydrazine)
hn g B
B
g g
B
r
r
0
0
g B
r
r
Slide 29
EPR: METHODOLOGIES
Resonance cavities
Slide 30
EPR: Spin Hamiltonian
-Hyperfine interaction: unpaired electron-nuclear spin: I mI = I, I - 1,…..,- I
each energy level of the electron is split according to mI
selection rule for EPR: ms = 1: mI = 0
- S > ½ more than one unpaired electron: ZERO FIELD SPLITTING
- QUADRUPOLAR INTERACTION: nuclear spins with I > 1/2
-SPIN HAMILTONIAN
H S . g .B S A . I S . D . S I . P . I
Slide 31
EPR: Quantitative
N Nr
I
g r S r ( S r 1)
Ir
g
S ( S 1)
Slide 32
In situ EPR
Set-up
Slide 33
FeAPO-5
Example: calcination of FeAPO-5
Slide 34
PULSE EPR
D. Goldfarb, Weizmann Institute, Israel
ESEEM: electron spin echo envelope modulation
ENDOR: electron nuclear double resonance
Examples:
1. Interaction of Cu2+ with Al nuclei in the zeolite lattice
2. Copper –histidine complexes in supercages of zeolite Y.
Slide 35
Copper – histidine complexes in supercages of zeolite Y
gا
gاا
A(ااmT)
d – d (cm-1)
A
2.054
2.31
15.8
15200
B
2.068
2.25
18.3
15600
Slide 36
TRANSITION METAL IONS IN ZEOLITES
Slide 37
Coordination to lattice oxygens
Characteristics
•Low coordination number
•Free coordination sites
•Low symmetry
Examples: Cu2+, Co2+
Slide 38
Cu2+: DRS + EPR
ZSM-5
Zeolite A
Slide 39
Cu2+: Summary of EPR parameters and d – d transitions
Zeolite
g
A/mT
g
A/mT
mordenite
2.327
15.42
2.062
1.49
ZSM 5
2.277
16.82
2.057
1.19
A, X, Y
2.387
12.20
2.069
1.34
Y, chabasite
2.336
15.85
2.070
1.93
d-d transitions/cm-1
mordenite
12500
13700
14800
A, X, Y
10400
12300
14800
Y, chabasite
10800
12900
14800
ZSM 5
Slide 40
Coordination of Co2+ and Cu2+ to sixrings: LF or AOM
Fixed oxygens: Cu2+/Co2+ in the center of the six- ring on trigonal axis
Cu2+: doubly degenerate ground-state Jahn-Teller distorsion
Co2+: off-axial displacement by 0.078 – 0.104nm
Slide 41
Coordination to six-rings in LTA and FAU
Cu2+
Slide 42
Cu2+:orbital interactions between d(Cu2+) and p(0)
Slide 43
Cu2+in ZSM-5: α sites with zero, one and two Al’s
0
T5
O6
1
Al
T 11
O5
O1
2
2.13
Al
2.02
2.90
1.98
3.09
T1
T4
T7
O4
O3
3.24
2.90
1.98
3.21
1.96
2.12
T8
Al
3.40
Al
binding energy
g-factors
-651
2.29 2.10 2.05
2'
3
4
3.41
2.00
1.94
2.07
2.08
2.00
2.16
Al
2.42
2.27
2.00
3.04
Al
3.26
-498
2.31 2.08 2.07
2.32
3.40
1.98
2.46
-635
2.33 2.10 2.05
2.62
3.46
2.06
3.14
3.19
2.06
-638
2.29 2.09 2.05
3.15
Al
3.60
2.41
O2
T2
2.88
2.92
Al
1.98
-481
2.33 2.08 2.07
Slide 44
Cu2+in ZSM-5: β sites with zero, one and two Al’s
0
1
O6
2
O5
Al
O1
T4
T 10
O2
O4
T 11
1.89
1.96
Al
Al
1.88
1.89
2.11
1 .9 8
1 .9 3
1.87
2 .1 4
1 .8 7
Al
T7
-715
2.23 2.07 2.04
4
5
3.37
3 .6 2
-677
2.25 2.10 2.03
-683
2.24 2.07 2.04
3 .4 6
3.22
1.93
1.96
2.06
1.86
2.09
1 .9 6
2 .4 2
Al
1.87
3 .1 5
1 .7 9
O
H
Al
3.45
-532
2.24 2.07 2.04
Al
3.55
3.53
binding energy
g-factors
2.07
2.08
Al
1.98
O3
1.95
3 .2 4
3.36
3.50
T5
T1
3
3.57
-514
2.25 2.09 2.04
4 .1 0
Al
2 .0 4
Slide 45
Cu2+in ZSM-5: γ sites with zero, one and two Al’s
0
1
3 .4 4
O6
T7
2
3.38
T7
Al
O1
O5
T10
T10
O4
1.96
T11
Al
Al
O2
1 .9 5
1 .9 5
1.93
1.91
2.05
Al
Al
O3
2.17
1.96
Al
1.91
T12
T12
3.00
1 .9 6
1 .9 6
2.09
T11
3
3 .4 1
3.27
3.37
binding energy
g-factors
-698
2.25 2.06 2.06
4
5
1 .9 8
2 .1 0
1 .9 4
-662
2.27 2.07 2.06
6
3 .2 8
3 .3 1
3 .2 9
Al
-680
2.26 2.07 2.05
2 .0 4
2 .0 8
2 .0 7
2 .0 2
1 .9 0
2 .0 2
Al
Al
2 .0 6
1 .9 7
1 .9 3
Al
3 .3 2
-656
2.29 2.07 2.06
3 .3 0
-523
2.27 2.06 2.06
3 .0 9
-505
2.28 2.08 2.05
Slide 46
Cu2+in ZSM-5: δ sites with zero, one and two Al’s
0
1
2
H
T2
1.78 O
2.03
T6
1.92
2.01
2.09
T1
3.57
Al
1.97
1.92
T9
T10
binding energy
g-factors
3.08
Al
1.92
-482
2.27 2.09 2.05
1.95
2.93
2.05
-483
2.25 2.08 2.05
Al
1.99
4.43
3.51
Slide 47
Cu2+in Zeolite: O Cu2+ charge transfer
cm-1/1000
ν (cm-1) = 30,000[χopt(0)-χopt(Cu2+)]
Slide 48
DRS spectrum of Co2+in Zeolite A
Slide 49
DRS spectrum of Co2+in Zeolite Y and its decomposition
Slide 50
DRS spectrum of Co2+in LTA and FAU:visible region
Slide 51
Co2+in FAU: interpretation
LF: trigonal Co2+
T: pseudo-tetrahedral Co2+ in site I’
HF: pseudo-octahedral Co2+ in site I
Slide 52
Coordination sites in pentosil zeolites(ZSM-5, MOR, FER)
Slide 53
Co2+ spectra in pentasil zeolites(ZSM-5, MOR, FER)
Slide 54
CONCLUSIONS
1. Significant technical advancement
DRS in situ single crystal
EPR
wide range of resonance frequencies
in situ
pulse
2. Coordination of transition metal ions
maximize coordination number
site distortion
number of Al tetrahedra
3. In situ
UV-VIS: catalyst activation: chromate Cr3+
active site: bis(µ-oxo)dicopper
isomorphous substitution: Co2+
EPR: isomorphous substitution of Fe3+
Slide 55
CONCLUSIONS
4. Pulse EPR:
- interaction TMI – Al in lattice
- coordination chemistry of Cr(histidine)x in supercages
- In situ techniques and pulse EPR give nice results in
well-chosen problems.
- Specialists are necessary; these are not routine
measurements
Slide 56
Thanks to
Collaborators:
(D. Packet, S. De Tavernier, M. Uytterhoeven,
B. Weckhuysen, A. Verberckmoes, M. Groothaert,
H. Leeman)
Collaborations:
K. Pierloot and A. Ceulemans
K. Klier
Financial support:
Concerted Research Action
Fund for Scientific Research
•ULTRAVIOLET-VISIBLE-NEAR INFRARED
(UV-VIS-NIR) SPECTROSCOPY
•ELECTRON PARAMAGNETIC RESONANCE (EPR)
or ELECTRON SPIN RESONANCE (ESR)
OF ZEOLITES
Robert A. SCHOONHEYDT
Center for Surface Chemistry and Catalysis
K.U. Leuven
Kasteelpark Arenberg 23, 3001 Leuven
Belgium
[email protected]
Slide 2
OUTLINE
1. Principles of UV-VIS-NIR
- physical basis
- methodology
2. In-situ UV-VIS
3. Optical and fluorescence microscopies
4. Principles of EPR
- physical basis
- methodology
5. In-situ EPR
6. Pulse EPR
7. Coordination of transition metal ions (TMI)
8. Conclusions
Slide 3
UV-VIS-NIR
Wavelength nm
Wavenumber
Frequency
cm-1
Hz
200
375
750
2500
50000
26664
13300
4000
8x1014
4x1014
1.2x1014
1.5x1015
UV
VISIBLE
NIR
Slide 4
What do we measure ?
Molecules: unsaturated
* and
n * transitions
Energy level diagramme
n π *
Antibonding
n *
π*
π π *
Antibonding
*
*
π
Nonbonding
π
Bonding
Bonding
Slide 5
Transitions Metal Ions
d – d transitions
Ligand- to Metal Charge Transfer
(LMCT)
Slide 6
Transitions Metal Ions
d – d transitions
Metal - to Ligand Charge Transfer
(MLCT)
example: [Cr(benzene)2]+
Slide 7
UV - VIS - NIR: Methodology
Powdered samples Diffuse Reflectance Spectroscopy (DRS)
Principle
x
I0
J0
I
J + J
x
I + I
J
Slide 8
Ideal Case: Kubelka – Munck formula
F R
1 R 2
2 R
K
kc
S
scattering intensity from infinitely thick sample
R∞ =
scattering intensity from infinitely thick white standard
K : Kubelka-Munck absorption coefficient
S : Kubelka-Munck scattering coefficient
Slide 9
Conditions for use of K M-formula
•diffuse monochromatic irradiation
•isotropic scattering
•infinite sample thickness
•low concentration of absorbing centers
•uniform distribution of absorbing centers
•absence of fluorescence
Slide 10
UV – VIS – NIR: instrumentation
•Every compagny has a UV-VIS-NIR spectrophotometer with
two sources ( Nerst glower, D2 lamp) and two detectors (PbS, PM).
•Integration sphere for DRS
•White standards: MgO, BaSO4, HALON.
Slide 11
IN – SITU UV-VIS-NIR
Praying Mantis
Optical fibre technology
O ptic al fib er
H ig h-tem p. pr ob e
hn
F low in
U V - vis s ourc e
O ven
R eac tor
C atalys t b ed
Gas inlet
M u lti-c h ann el
d etec tor
C om pu ter
Gas outlet
Most sensitive region: VISIBLE
low background
sensitive detection: PM
Q u artz w ool
GC
F low out
Slide 12
IN – SITU UV-VIS-NIR
Examples:
d d (pseudo)tetrahedral Co2+
O Cr6+ charge transfer (chromate, dichromate)
O Cu2+ bis(µ-oxo)dicopper
Slide 13
Microporous crystalline metal-containing
Aluminiumphosphates:isomorphous substitution
O
O
-1
Al
O
O
-2
Co
O O
O
Al
O
O
O
Co2+
O
+1
O
-1
P
O
O
-1
P
O
Isomorphous
substitution
O
O
+1
Al
O
O
O
AlPO4-5
AFI
Slide 14
CoAPO-5: in situ synthesis
synthesis C oAPO -5
2.2
1.8
1.6
absorbance
Absorbance
2.0
24u
1.4
16u
1.2
1.0
0.8
0.6
0u
25°c
0.4
500
1000
1500
2000
wavelength
Wavelength (nm)
Synthesis time
2500
Slide 15
CoAPO-5 synthesis: spectra at RT
Slide 16
Chromate reduction with CO in zeolite Y
Slide 17
bis( µ-oxo )dicopper in ZSM-5
C Z -3 1 -0 .1 6
C Z -3 1 -0 .3 4
a b s o rp tio n (a .u .)
C Z -3 1 -0 .5 8
10000
20000
30000
40000
-1
w a ve n u m b e r (cm )
50000
Slide 18
OPTICAL and FLUORESCENCE MICROSCOPIES
Slide 19
Intergrowth structure of ZSM-5
Accessibility?
Slide 20
Applications
Oligomerization of furfurylalcohol in ZSM-5 and mordenite
Slide 21
Applications
Oligomerization of styrene in ZSM-5
+
H+
R
R
+
R
R
+
+
R
R
R R
B
R
B
A
R
D
T rim e tric o lo g o m e rs
E
Slide 22
oligomerization of styrene: absorption spectra
Slide 23
Decomposition of template molecules in CrAPO-5
Slide 24
Decomposition of template molecules and intergrowth structures
CrAPO-5
SAPO-34
SAPO-5
ZSM-5
Slide 25
ELECTRON PARAMAGNETIC RESONANCE
magnetic moment of the unpaired elelctron
µ g S 2h S
µ
z
g S
z
2h S
z
S = dimensionless spin angular momentum vector of the electron
S2 = s(s+1) s = ½
SZ =ms ms = 1/2, -1/2
e h 9 ,2741 x10 24 JT 1
= Borhmagneton
2me
g, spectroscopic splitting factor = 2.0023
ħ = h/2π
γ = gyromagnetic ratio
Slide 26
ZEEMAN INTERACTION
EZ = -µZB0 = gβB0ms
ms = ½: 1/2g βB0
ms = -½: -1/2g βB0
E
ms = 1/2
E = gβB0
ms = - 1/2
B0
Resonance condition: hν = E = gβB0
Slide 27
EPR: powder spectra
All possible orientations of the spins
Each orientation has its own resonance condition
Spectra are superpositions of all those individual spectra
isotropic
axially symmetric
orthorhombic
Slide 28
EPR: Measurement of g values
measurement at constant frequency and varying magnetic field
Band name
band range, GHz
L
S
C
X
K
Q
V
W
g=
hn
B
1.5
2.6-4
4-6
8.2-12.4
18-26.5
33-50
50-75
75-100
= 7,145x10-9 ν/B0
to be measured with gaussmeter
0
to be read from microwave bridge
reference: DPPH gr = 2,0036 (diphenylpicrylhydrazine)
hn g B
B
g g
B
r
r
0
0
g B
r
r
Slide 29
EPR: METHODOLOGIES
Resonance cavities
Slide 30
EPR: Spin Hamiltonian
-Hyperfine interaction: unpaired electron-nuclear spin: I mI = I, I - 1,…..,- I
each energy level of the electron is split according to mI
selection rule for EPR: ms = 1: mI = 0
- S > ½ more than one unpaired electron: ZERO FIELD SPLITTING
- QUADRUPOLAR INTERACTION: nuclear spins with I > 1/2
-SPIN HAMILTONIAN
H S . g .B S A . I S . D . S I . P . I
Slide 31
EPR: Quantitative
N Nr
I
g r S r ( S r 1)
Ir
g
S ( S 1)
Slide 32
In situ EPR
Set-up
Slide 33
FeAPO-5
Example: calcination of FeAPO-5
Slide 34
PULSE EPR
D. Goldfarb, Weizmann Institute, Israel
ESEEM: electron spin echo envelope modulation
ENDOR: electron nuclear double resonance
Examples:
1. Interaction of Cu2+ with Al nuclei in the zeolite lattice
2. Copper –histidine complexes in supercages of zeolite Y.
Slide 35
Copper – histidine complexes in supercages of zeolite Y
gا
gاا
A(ااmT)
d – d (cm-1)
A
2.054
2.31
15.8
15200
B
2.068
2.25
18.3
15600
Slide 36
TRANSITION METAL IONS IN ZEOLITES
Slide 37
Coordination to lattice oxygens
Characteristics
•Low coordination number
•Free coordination sites
•Low symmetry
Examples: Cu2+, Co2+
Slide 38
Cu2+: DRS + EPR
ZSM-5
Zeolite A
Slide 39
Cu2+: Summary of EPR parameters and d – d transitions
Zeolite
g
A/mT
g
A/mT
mordenite
2.327
15.42
2.062
1.49
ZSM 5
2.277
16.82
2.057
1.19
A, X, Y
2.387
12.20
2.069
1.34
Y, chabasite
2.336
15.85
2.070
1.93
d-d transitions/cm-1
mordenite
12500
13700
14800
A, X, Y
10400
12300
14800
Y, chabasite
10800
12900
14800
ZSM 5
Slide 40
Coordination of Co2+ and Cu2+ to sixrings: LF or AOM
Fixed oxygens: Cu2+/Co2+ in the center of the six- ring on trigonal axis
Cu2+: doubly degenerate ground-state Jahn-Teller distorsion
Co2+: off-axial displacement by 0.078 – 0.104nm
Slide 41
Coordination to six-rings in LTA and FAU
Cu2+
Slide 42
Cu2+:orbital interactions between d(Cu2+) and p(0)
Slide 43
Cu2+in ZSM-5: α sites with zero, one and two Al’s
0
T5
O6
1
Al
T 11
O5
O1
2
2.13
Al
2.02
2.90
1.98
3.09
T1
T4
T7
O4
O3
3.24
2.90
1.98
3.21
1.96
2.12
T8
Al
3.40
Al
binding energy
g-factors
-651
2.29 2.10 2.05
2'
3
4
3.41
2.00
1.94
2.07
2.08
2.00
2.16
Al
2.42
2.27
2.00
3.04
Al
3.26
-498
2.31 2.08 2.07
2.32
3.40
1.98
2.46
-635
2.33 2.10 2.05
2.62
3.46
2.06
3.14
3.19
2.06
-638
2.29 2.09 2.05
3.15
Al
3.60
2.41
O2
T2
2.88
2.92
Al
1.98
-481
2.33 2.08 2.07
Slide 44
Cu2+in ZSM-5: β sites with zero, one and two Al’s
0
1
O6
2
O5
Al
O1
T4
T 10
O2
O4
T 11
1.89
1.96
Al
Al
1.88
1.89
2.11
1 .9 8
1 .9 3
1.87
2 .1 4
1 .8 7
Al
T7
-715
2.23 2.07 2.04
4
5
3.37
3 .6 2
-677
2.25 2.10 2.03
-683
2.24 2.07 2.04
3 .4 6
3.22
1.93
1.96
2.06
1.86
2.09
1 .9 6
2 .4 2
Al
1.87
3 .1 5
1 .7 9
O
H
Al
3.45
-532
2.24 2.07 2.04
Al
3.55
3.53
binding energy
g-factors
2.07
2.08
Al
1.98
O3
1.95
3 .2 4
3.36
3.50
T5
T1
3
3.57
-514
2.25 2.09 2.04
4 .1 0
Al
2 .0 4
Slide 45
Cu2+in ZSM-5: γ sites with zero, one and two Al’s
0
1
3 .4 4
O6
T7
2
3.38
T7
Al
O1
O5
T10
T10
O4
1.96
T11
Al
Al
O2
1 .9 5
1 .9 5
1.93
1.91
2.05
Al
Al
O3
2.17
1.96
Al
1.91
T12
T12
3.00
1 .9 6
1 .9 6
2.09
T11
3
3 .4 1
3.27
3.37
binding energy
g-factors
-698
2.25 2.06 2.06
4
5
1 .9 8
2 .1 0
1 .9 4
-662
2.27 2.07 2.06
6
3 .2 8
3 .3 1
3 .2 9
Al
-680
2.26 2.07 2.05
2 .0 4
2 .0 8
2 .0 7
2 .0 2
1 .9 0
2 .0 2
Al
Al
2 .0 6
1 .9 7
1 .9 3
Al
3 .3 2
-656
2.29 2.07 2.06
3 .3 0
-523
2.27 2.06 2.06
3 .0 9
-505
2.28 2.08 2.05
Slide 46
Cu2+in ZSM-5: δ sites with zero, one and two Al’s
0
1
2
H
T2
1.78 O
2.03
T6
1.92
2.01
2.09
T1
3.57
Al
1.97
1.92
T9
T10
binding energy
g-factors
3.08
Al
1.92
-482
2.27 2.09 2.05
1.95
2.93
2.05
-483
2.25 2.08 2.05
Al
1.99
4.43
3.51
Slide 47
Cu2+in Zeolite: O Cu2+ charge transfer
cm-1/1000
ν (cm-1) = 30,000[χopt(0)-χopt(Cu2+)]
Slide 48
DRS spectrum of Co2+in Zeolite A
Slide 49
DRS spectrum of Co2+in Zeolite Y and its decomposition
Slide 50
DRS spectrum of Co2+in LTA and FAU:visible region
Slide 51
Co2+in FAU: interpretation
LF: trigonal Co2+
T: pseudo-tetrahedral Co2+ in site I’
HF: pseudo-octahedral Co2+ in site I
Slide 52
Coordination sites in pentosil zeolites(ZSM-5, MOR, FER)
Slide 53
Co2+ spectra in pentasil zeolites(ZSM-5, MOR, FER)
Slide 54
CONCLUSIONS
1. Significant technical advancement
DRS in situ single crystal
EPR
wide range of resonance frequencies
in situ
pulse
2. Coordination of transition metal ions
maximize coordination number
site distortion
number of Al tetrahedra
3. In situ
UV-VIS: catalyst activation: chromate Cr3+
active site: bis(µ-oxo)dicopper
isomorphous substitution: Co2+
EPR: isomorphous substitution of Fe3+
Slide 55
CONCLUSIONS
4. Pulse EPR:
- interaction TMI – Al in lattice
- coordination chemistry of Cr(histidine)x in supercages
- In situ techniques and pulse EPR give nice results in
well-chosen problems.
- Specialists are necessary; these are not routine
measurements
Slide 56
Thanks to
Collaborators:
(D. Packet, S. De Tavernier, M. Uytterhoeven,
B. Weckhuysen, A. Verberckmoes, M. Groothaert,
H. Leeman)
Collaborations:
K. Pierloot and A. Ceulemans
K. Klier
Financial support:
Concerted Research Action
Fund for Scientific Research