Spectroscopy of Transition Metal Ions on Surfaces

313 Pages·2000·8.124 MB·English

by  Bert M. Weckhuysen, Pascal Van Der Voort, Gabriela Catana

Spectroscopy of
Transition Metal Ions

on Surfaces

Edited by
ert M. Weckhuyse

Pascal Van D^r Voor
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Leuven Universi

SPECTROSCOPY OF TRANSITION METAL IONS ON SURFACES
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SPECTROSCOPY OF
TRANSITION METAL IONS
ON SURFACES
Editors
Bert M. Weckhuysen
Pascal Van Der Voort
Gabriela Catana

Leuven University Press
2000
©2000LeuvenUniversityPress/PressesUniversitairesdeLouvain/UniversitairePersLeuven
Blijde-Inkomststraat5,B-3000Leuven(Belgium)
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instructionsorideasdescribedinthisbook.
ISBN9058670252
D/2000 71869/22
Cover:LejonTits
CONTENTS
Preface 1 1
1. Spectroscopic characterization ofheterogeneous catalysts 13
By Bert M. Weckhuysen, Pascal Van Der Voort and Gabriela Catana
1.1. Transition metal ions on surfaces as heterogeneous catalysts 13
1.2. Spectroscopic characterization ofheterogeneous catalysts 15
1.3. Insitu spectroscopy 19
1.4. References 20
2. Magnetic resonance techniques 23
By Angelika Bruckner, Michel Che, Krystyna Dyrek, Daniella Goldfarb,
PietJ. Grobet, RobertA. Schoonheydt and Bert M. Weckhuysen
2.1. General principles ofmagnetic resonancetechniques 25
2.1.1. Introduction 25
2.1.2. Spin resonance spectroscopy 25
2.1.3. Electron spin resonance spectroscopy 31
2.1.3.1. Magnetic interactions 33
2.1.3.2. Instrumentation 37
2.1.3.3. Quantitative analysis 39
2.1.3.4. Spectrum simulation 40
2.1.4. References 42
2.2. Electron spin resonance: strength andweakness 45
2.2.1. Introduction 45
2.2.2. Advantages and limitations ofESR 47
2.2.3. ESR spectra ofpowder samples 49
2.2.3.1. Physical tools 50
2.2.3.2. Chemical tools 56
2.2.3.3. Numerical tools 60
2.2.4. Quantitative approach 60
2.2.4.l. Standards forspin dosimetry 61
2.2.4.2. Application ofspin dosimetry in solid state chemistryand 61
heterogeneous catalysis
2.2.5. Selected examples 63
2.2.5.1. Methanol oxidation over supportedmolybdenum oxide 63
catalysts
2.2.5.2. Oxidative coupling ofmethane 64
2.2.6. Concluding remarks 66
2.2.7. References 66
2.3. Insitu electron spin resonance 69
2.3.1. Introduction 69
2.3.2. Theoretical background 69
2.3.3. Experimental setup 75
2.3.4. Selected examples 77
2.3.4.1. Supported and unsupported vanadium phosphorus oxide 77
catalysts
2.3.4.2. Supported chromium oxide catalysts 82
2.3.4.3. FAPO-5 molecularsieves 85
2.3.5. Concludingremarks 89
2.3.6. References 90
2.4. Pulsed electron spin resonance techniques 93
2.4.1. Introduction 93
2.4.2. Superhyperfine interaction and the NMR frequencies 94
2.4.2.1. The spin Hamiltonian 94
2.4.2.2. The NMR frequencies forsystems with S = !/•> and I = !/2 96
2.4.2.3. The NMR frequencies forsystems with S = !/2and 1=1 98
2.4.2.4. The NMR frequencies forsystems with S = 5/2 and I = !/2 100
2.4.3. Echo-detected ESR and orientation selectivity 101
2.4.4. ESEEM experiments 103
2.4.4.1. Fouriertransformation and data treatment 104
2.4.4.2. Two-pulse ESEEM 105
2.4.4.3. Three-pulse ESEEM 107
2.4.4.4. Four-pulse ESEEM 110
2.4.4.5. Two-dimensional experiments 111
2.4.5. ENDOR methods 116
2.4.5.1. Davies ENDOR 117
2.4.5.2. High field ESR/ENDOR 121
2.4.5.3. Mims ENDOR 123
2.4.6. Instrumental details 127
2.4.7. Concluding remarks 129
2.4.8. References 130
2.5. Solid state nuclear magnetic resonance techniques 135
2.5.1. Introduction 135
2.5.2. Principles ofnuclearmagnetic resonance spectroscopy 136
2.5.3. Nuclearmagnetic resonance line broadening in solids 137
2.5.3.1. Dipolar interactions 138
2.5.3.2. Chemical shift anisotropy 139
2.5.3.3. Quadrupolar interactions 140
2.5.4. High-resolution solid-state NMR techniques 141
2.5.4.1. Solid-state NMR line-narrowingtechniques 141
2.5.4.2. NMR signal enhancement technique : cross-polarization 145
2.5.5. Selected examples 147
2.5.5.1. Supported chromium oxide catalysts 147
2.5.5.2. Supported vanadium oxide catalysts 149
2.5.6. Concluding remarks 152
2.5.7. References 153
3. Vibrational spectroscopies 155
By Gerhard Mestl, Robert A. Schoonheydt ,Pascal Van Der Voort,
Etienne F. Vansant and Bert M. Weckhuysen
3.1. General principles ofvibrational spectroscopies 157
3.1.1. Introduction 157
3.1.2. Molecular vibrations 157
3.1.2.1. The vibrating diatomic molecule l57
3.1.2.2. The vibrations ofpolyatomic molecules 161
3.1.3. References 164
3.2. Infrared spectroscopy 165
3.2.1. Introduction 165
3.2.2. Principles ofFourierTransform-Infrared spectroscopy l66
3.2.3. Solid state sampling accessories 168
3.2.3.1. Diffuse reflectance spectroscopy 168
3.2.3.2. Photo-acoustic spectroscopy 170
3.2.4. Selected examples 171
3.2.4.1. Indirect study the transition metal ion by studying the 172
support hydroxyls andthe (organic) ligands ofa
transition metal complex
3.2.4.2. Indirect study ofthe transition metal ion by selective 180
complexation with probe molecules
3.2.4.3. Direct study ofthe transition metal ion by reducing the 188
absorbance ofthe support using 'thin film techniques'
3.2.4.4. Direct study ofthe transition metal ion by using an 191
appropriate sampling technique
3.2.5. Concluding remarks 193
3.2.6. References 194
3.3. Raman spectroscopy 197
3.3.1. Introduction 197
3.3.2. Theoretical background 197
3.3.3. Limitations and quantitation 201
3.3.3.1. Limitations 201
3.3.3.2. Quantitation 202
3.3.4. Selected examples 204
3.3.4.1. In situ Raman characterization ofthe oxygen exchange 204
in MoOySb2O4-selective partial oxidation catalysts