Isotopes in Heterogeneous Catalysis

Contents......Page 6
Contributors......Page 12
Preface......Page 14
1. Introduction......Page 16
2. H/D Exchange in the Strongest Liquid Superacids......Page 17
3.1. The number of exchangeable acid sites on the catalyst......Page 20
3.2. H/D exchange with methane and ethane......Page 25
3.3. H/D exchange with alkanes having more than 2 carbon atoms......Page 29
3.4. The case of propane......Page 33
3.5.1. Molecular rearrangement......Page 36
3.5.2. Deactivation of acidic catalysts......Page 38
4. Conclusion......Page 40
References......Page 42
1. Introduction......Page 46
2.1. Hydrocarbon cracking and isomerisation over acidic catalysts......Page 47
2.2. Formation and rupture of C5-cyclic hydrocarbons......Page 54
2.3. Aromatisation of branched alkanes......Page 55
3. Study of Reaction Kinetics by Isotope Tracer......Page 59
3.1. Benzene hydrogenation......Page 60
3.2. The kinetic isotope method......Page 61
4. Reaction Pathway Studies by the Determination of the Position of the Label......Page 63
4.1. Dehydrocyclisation......Page 65
4.2. Skeletal transformations of cyclic hydrocarbons......Page 66
4.3. Fischer-Tropsch synthesis......Page 68
References......Page 73
Introduction......Page 78
1.1. Single crystals......Page 81
1.2. Non-supported catalysts......Page 82
1.3. Supported catalysts......Page 84
2. Catalysts’ Sulfur Mobility......Page 89
2.1. Catalyst sulfur exchange with hydrogen sulfide......Page 90
2.2. Sulfur exchange via thiophene HDS......Page 94
2.3. Sulfur exchange via HDS of thioaromatic compounds......Page 98
3. On the Role of Catalyst Sulfur in Catalytic Hydrodesulfurisation: Some Conclusions from Tracer Studies......Page 101
3.1. On the mechanism of sulfur exchange......Page 102
3.2. On the reaction mechanism of desulfurisation......Page 103
References......Page 108
1. Introduction......Page 112
2. Radiochemical Facilities......Page 113
3. Tritiation Procedures......Page 121
4. Discussion......Page 122
5. Conclusion......Page 126
References......Page 127
1. Introduction......Page 130
2. Activity Patterns......Page 133
3. Nature of the Exchange Site......Page 141
4. Conclusion......Page 145
References......Page 146
Glossary of Symbols Used......Page 148
1. Introduction......Page 149
2.1. Overview......Page 150
2.2.1. Definitions......Page 151
2.2.2. Kinetics of the exchange between a gas and a monophasic solid......Page 152
2.3. Mechanisms of isotopic exchange of oxygen on oxide-supported catalysts......Page 153
2.4.1. Mechanism and kinetic conditions......Page 154
2.4.2. Determination of the rate of exchange......Page 156
2.4.3. Initial rates of exchange......Page 157
2.4.4. Numbers of exchanged and of exchangeable atoms......Page 158
2.5.1. Exchange is controlled by adsorption-desorption of X2 on the metal......Page 159
2.5.2. Exchange is controlled by the metal  support transfer......Page 160
2.5.3. Exchange is controlled by the surface diffusion on the support......Page 162
2.5.4. Exchange is controlled by bulk diffusion into the support......Page 163
2.6. Isotopic homoexchange on supported metal catalysts......Page 164
2.6.1. Mechanisms......Page 165
2.6.2. Kinetics......Page 166
3.1. Overview......Page 168
3.2.1. 1H2/2H2 equilibration......Page 169
3.2.2. 16O2/18O2 equilibration......Page 171
3.3.1. 2H2 exchange with 1HS species of oxides......Page 174
3.3.2. 18O2 exchange with 16OS species of oxides......Page 178
3.4.1. 2H2 heteroexchange with 1H species of alumina in the presence of metals......Page 181
3.4.2. Hydrogen exchange on other supports......Page 184
3.5. Surface diffusion of oxygen species on supported metal catalysts......Page 185
3.6. Comparison between H and O surface diffusion......Page 187
4. Recent Developments of 16O/18O Isotopic Exchange: Case of Oxides with Very High Oxygen Mobility......Page 189
References......Page 192
1. Introduction......Page 198
2. Theory......Page 199
3.1. Deconvolution......Page 205
3.2. Convolution......Page 206
4.1. H2-D2......Page 208
4.3. Readsorption......Page 209
4.4. Steady-state versus non-steady-state analysis......Page 211
5.1. TOF on metals......Page 212
5.2. Cause of deactivation......Page 213
5.3. Effects of promotion......Page 214
5.4. Effect of alloying......Page 215
5.5. Acid catalysis......Page 216
5.6. High temperature reaction......Page 218
5.7. Effect of temperature......Page 219
6. Summary......Page 221
Acknowledgement......Page 222
References......Page 223
1. Introduction......Page 228
1.1. Positron emission and positron-electron annihilation......Page 229
1.2. Positron emission detection methods......Page 231
1.3. Positron Emission Tomography (PET), Particle Tracking (PEPT) and Profiling (PEP)......Page 232
1.4. The TU/e PEP detector......Page 234
2. Synthesis of Radio-labelled Molecules......Page 237
2.1. 13NH3 production......Page 238
3. Positron Emission Profiling Study on the Catalytic Ammonia Oxidation......Page 239
3.1. Activation of ammonia dissociation on Pt......Page 240
3.1.2. Activation of ammonia adsorption by oxygen......Page 241
3.1.3. Influence of temperature on the ammonia dissociation on pre-oxidised Pt......Page 243
3.1.4. Determination of adsorbed species by temperature programmed desorption......Page 245
3.1.5. Determination of adsorbed species by temperature programmed oxidation......Page 247
Reaction with hydrogen......Page 249
Reaction with ammonia......Page 250
Reaction with NO......Page 251
3.1.7. Conclusions......Page 254
3.2. Low temperature ammonia oxidation on Pt......Page 255
Conversion and selectivity......Page 256
Positron Emission Pro.ling......Page 257
Temperature programmed desorption......Page 259
Temperature programmed oxidation......Page 261
Temperature programmed reaction with NO......Page 262
3.2.4. Conversion and selectivity on pre-oxidised platinum......Page 263
3.2.5. Desorption of water......Page 264
3.2.6. Reaction mechanism......Page 266
3.2.7. Conclusion......Page 268
3.3.1. Experimental details......Page 269
3.3.3. [13N]-NH3 Adsorption Assisted Desorption pulse experiments......Page 270
3.3.4. Conclusions......Page 271
References......Page 272
Index......Page 276