Chapter 1 Introduction ..........................................
Christian Hess
References
Chapter 2 C-H Activation of Alkanes in Selective Oxidation
Reactions on Solid Oxide Catalysts .................................. 5
Johannes A. Lercher and Frederik N. Naraschewski
2.1 Introduction ................................................... 5
2.2 Models of C-H Bond Activation over Supported and Unsupported
Oxide Clusters ................................................. 7
2.2.1 Vanadium-Based Clusters ................................. 8
2.2.2 Molybdenum and Tungsten Oxide Clusters ................. 12
2.2.3 Complex Mixed Oxides ................................... 14
2.2.4 Transition-Metal Species in Zeolites ................... 16
2.3 Impact of Anions on C-H Activation ............................ 18
2.3.1 Vanadium Pyrophosphate as Catalyst for Butane
Activation ............................................. 18
2.3.2 Supported LiCl as Catalyst for Oxidative
Dehydrogenation of Ethane to Ethene .................... 20
2.4 Indirect Oxidation via Electrophilic Substitution-
Chlorination and Bromination .................................. 21
2.5 Oxidative C-H Activation via Activation with Nonreducible
Cations ....................................................... 24
2.5.1 C-H Activation of Alkanes by Li-Promoted MgO ........... 24
2.5.2 Bifunctional Oxidative Catalysis with Main Group
Cations at Zeolite Exchange Sites ...................... 26
2.6 Conclusion and Outlook ........................................ 27
References .................................................... 28
Section I Oxide-Catalyzed Selective Oxidations of Light
Hydrocarbons (Chapters 3-7)
Chapter 3 Catalysis of Oxidative Methane Conversions .............. 35
Evgenii V. Kondratenko and Manfred Baerns
3.1 Introduction .................................................. 35
3.2 Methane as a Feedstock for Oxidative Conversions .............. 35
3.3 Oxidative Coupling of Methane (OCM) ........................... 37
3.3.1 Catalytic Materials and Modes of Process Operation ..... 37
3.3.2 Interaction of Methane on Solid Catalytic Surfaces ..... 38
3.3.3 Mechanistic Insights into Ethane, Ethylene and СОд-
Formation .............................................. 39
3.3.4 Oxygen Species in the OCM Reaction ..................... 39
3.3.5 Selectivity- and Activity-Governing Factors ............ 43
3.4 Methane Oxidation to Methanol and Formaldehyde ................ 44
3.4.1 Interaction of Oxygen and Methane on Transition-
Metal Oxides ........................................... 44
3.4.2 Methane to Methanol .................................... 45
3.4.2.1 Homogeneous and Heterogeneous Methanol
Formation ..................................... 45
3.4.2.2 Enzymatic Conversion of Methane to Methanol ... 47
3.4.3 Methane to Formaldehyde ................................ 48
3.5 Outlook ................................................... 50
References .................................................... 51
Chapter 4 Propane-Selective Oxidation to Acrylic Acid ............. 56
Annette Trunschke
4.1 Introduction .................................................. 56
4.2 Technological Background ...................................... 57
4.3 Catalysts and Product Distribution in Selective Oxidation
of Propane .................................................... 59
4.3.1 Phosphates ............................................. 61
4.3.2 Catalysts Derived from Heteropoly Compounds ............ 61
4.3.3 Multimetal Oxides ...................................... 62
4.4 Crystal Structure of the Key Phases in Mo-Based Multimetal-
Oxide Catalysts ............................................... 64
4.5 Phase Cooperation and Crystallinity ........................... 65
4.6 Synthesis of Phase-Pure Mo-Based Multimetal Oxides ............ 67
4.6.1 Preparation of Mo-V-Te-Nb Oxides by Precipitation/
Rapid Solvent Evaporation .............................. 68
4.6.2 Preparation of Mo-V-Te-Nb Oxides by Hydrothermal
Synthesis .............................................. 71
4.7 Characteristics of M1 ......................................... 74
4.7.1 Reaction Network and Mechanism ......................... 74
4.7.2 Chemical Composition and Active Sites .................. 78
4.7.3 Structure Sensitivity and Termination .................. 79
4.7.4 Surface Dynamics ....................................... 82
4.8 Functional Model of M1 ........................................ 84
Acknowledgements .............................................. 86
References .................................................... 87
Chapter 5 Ammoxidation of Propylene and Propane to Acrylonitrile .. 96
Robert K. Grasselli
5.1 Introduction and Historic Background .......................... 96
5.2 General ....................................................... 99
5.3 Propylene Ammoxidation to Acrylonitrile ...................... 100
5.3.1 The SOHIO Acrylonitrile Process ....................... 101
5.3.2 Key Catalytic Functionalities ......................... 104
5.3.3 Role of Lattice Oxygen - Catalyst as Redox Solid ...... 104
5.3.4 Generalized Mechanism of Alkene Ammoxidation .......... 106
5.3.5 Multifunctional Nature of Active Sites ................ 106
5.3.6 Ammoxidation Mechanism (Molybdates, Antimonates) ...... 108
5.3.7 Molybdate Catalysts ................................... 113
5.3.8 Multicomponent Molybdates ............................. 114
5.3.9 Commercial Molybdate Catalysts ........................ 116
5.3.10 Antimonate Catalysts .................................. 119
5.4 Propane Ammoxidation to Acrylonitrile ........................ 122
5.4.1 Structure of MoVNbTeO Catalysts ....................... 124
5.4.2 Symbiosis between M1 and M2 Phases .................... 126
5.4.3 Reaction Network and Mechanism ........................ 130
5.4.4 Future Research ....................................... 135
References ................................................... 136
Chapter 6 Selective Oxidation of n-Butane over Vanadium-
Phosphorous Oxide ................................................. 141
Moises A. Carreon and Vadim V. Guliants
6.1 Introduction ................................................. 141
6.2 VOHPO4-0.5H2O Precursor ...................................... 142
6.2.1 Conventional Synthesis Methods ........................ 142
6.2.2 Thermal Activation .................................... 144
6.2.3 Equilibrated VPO Catalyst ............................. 145
6.2.4 Optimal P/V Ratio ..................................... 146
6.3 Active VPO Surface ........................................... 147
6.4 Proposed Reaction Steps and Active Sites in n-Butane
Oxidation .................................................... 149
6.5 Promoted VPO ................................................. 151
6.6 Alternative Synthesis Strategies to VPO Catalysts ............ 157
6.6.1 Mesostructured VPO Phases ............................. 158
6.6.2 Macroporous VPO Phases ................................ 159
6.6.3 Intercalation and Pillaring of Layered VPO Phases ..... 160
6.6.4 Other Synthesis Methods of Dense VPO .................. 161
6.6.5 Supported VPO ......................................... 162
6.7 Conclusions .................................................. 163
References ........................................................ 164
Chapter 7 Routes to Methacrylic Acid via Partial Oxidation ....... 169
Stephan A. Schunk and Nadine Brem
7.1 Routes to Methacrylic Acid via Partial Oxidation ............. 169
7.2 The Industrial Importance of Methacrylic Acid ................ 169
7.3 Heteropolyacids: Multifunctional Oxidic Materials with
Superior Qualities as Oxidation Catalysts .................... 171
7.4 Cs-Containing Molybdophosphoric Keggin Structures: The
Industrial Workhorse for the Oxidation of Methacrolein to
Methacrylic Acid ............................................. 175
7.5 SbOx/Pt Catalysts as an Interesting Materials Class for the
Selective Oxidation of Isobutane and Isobutene to
Methacrolein ................................................. 178
7.6 Modified Heteropolyacid Catalysts for the Selective
Oxidation of Isobutane to Methacrolein and Methacrylic Acid .. 181
7.7 Formation of Methacrolein and Methacrylic Acid by
Oxidative Dehydrogenation of Isobutyric acid and
Isobutyraldehyde using Iron Phosphate Catalysts .............. 183
References ........................................................ 186
Section II Other Selective Oxidations (Chapters 8-11)
Chapter 8 Gold as a Selective Oxidation Catalyst
Graham J. Hutchings
8.1 Introduction ................................................. 193
8.2 Gold Catalysis: the Early Years .............................. 194
8.3 Very Small Gold Clusters are Active in Oxidation
Reactions .................................................... 196
8.4 Oxidation of Alcohols ........................................ 200
8.5 Alkene Epoxidation ........................................... 205
8.6 Concluding Remarks ........................................... 209
References ................................................... 210
Chapter 9 Ethylene Epoxidation over Silver Catalysts
Valerii I. Bukhtiyarov and Axel Knop-Gericke
9.1 Introduction ................................................. 214
9.2 Mechanisms of Ethylene Epoxidation ........................... 216
9.2.1 The Nature of Ethylene Epoxidizing Oxygen Species ..... 216
9.2.2 The Transformation of Oxygen Species on Ag Catalysts .. 227
9.2.3 The Nature of the Key Surface Intermediate ............ 231
9.2.4 Secondary Reactions ................................... 232
9.2.5 Mechanisms of Ethylene Epoxidation over Silver ........ 234
9.3 Optimization of the EtO Catalysts via Nanostructured
Materials .................................................... 236
9.3.1 Size Effects in Ethylene Epoxidation .................. 236
9.3.2 Modern Trends in Development of the Catalysts for
Ethylene Epoxidation .................................. 241
9.3.2.1 Optimization of Silver Particle Sizes ............... 241
9.3.2.2 Ag-Cu Alloys in Ethylene Epoxidation ................ 241
9.4 The Similarity and Differences in Propylene Epoxidation
Compared to Ethylene Epoxidation ............................. 242
9.5 Outlook ...................................................... 243
References ................................................... 243
Chapter 10 Ruthenium Active Catalytic States: Oxidation States
and Methanol Oxidation Reactions .................................. 248
Raoul Blume, Michael Hävecker, Spiros Zafeiratos, Detre Techner,
Axel Knop-Gericke, Robert Schlögl, Luca Gregoratti, Alexei
Barinov and Maya Kiskinova
10.1 Introductory Remarks ......................................... 248
10.2 Experimental Techniques ...................................... 250
10.3 Oxidation States and Morphology of the Ru Catalyst Surface
Exposed to O2 at Different Temperatures ...................... 251
10.4 Methanol Oxidation ........................................... 256
10.5 Concluding Remarks ........................................... 262
Acknowledgements .................................................. 263
References ........................................................ 263
Chapter 11 Styrene Synthesis: ln-Situ Model Catalysis Studies on
Ethylbenzene Dehydrogenation ...................................... 266
Wolfgang Ranke
11.1 Introduction ................................................. 266
11.1.1 Nonoxidative Dehydrogenation (DH) of Ethylbenzene ..... 267
11.1.2 Oxidative Dehydrogenation (ODH) of Ethylbenzene ....... 269
11.2 Dehydrogenation of Ethylbenzene: Model Catalysis Studies ..... 270
11.2.1 Experimental .......................................... 270
11.2.1.1 Instrumentation .............................. 270
11.2.1.2 Preparation .................................. 271
11.2.2 Catalyst Characterization ............................. 273
11.2.2.1 Surface Structure ............................ 273
11.2.2.2 Adsorption and Interaction ................... 274
11.2.2.2.1 Ethylbenzene and Styrene .......... 274
11.2.2.2.2 Water ............................. 276
11.2.2.2.3 Hydrogen .......................... 276
11.2.3 Catalytic Characterization ............................ 277
11.2.3.1 Low- and Medium-Pressure Reactivity
Measurements ................................. 277
11.2.3.2 In-Situ M icroflow Reactor ................... 279
11.2.3.3 Unpromoted Fe3O4, Fe2O3 ...................... 281
11.2.3.4 K-promoted KFexOy ............................ 285
11.2.4 Microkinetic Modeling ................................. 288
11.3 Summary and Outlook .......................................... 290
References ........................................................ 293
Section III Supported Vanadium-Oxide Systems and Mechanistic
Studies (Chapters 12-14)
Chapter 12 Highly Dispersed Vanadium-Oxide Catalysts .............. 299
Christian Hess
12.1 Introduction ................................................. 299
12.2 Synthesis of Highly Dispersed Vanadium Oxide ................. 302
12.3 Influence of Water on Structure and Dispersion ............... 306
12.3.1 Structure ............................................. 306
12.3.2 Correlation of Changes in Structure and Dispersion .... 309
12.4 Selective Oxidation of Methanol .............................. 312
12.4.1 Reactivity ............................................ 312
12.4.2 Spectroscopic Characterization ........................ 314
12.5 Oxidative Dehydrogenation of Propane ......................... 318
12.5.1 Reactivity ............................................ 318
12.5.2 Influence of Surface Functionalization ................ 319
12.6 Conclusions and Outlook ...................................... 320
Acknowledgement .............................................. 321
References and Notes ......................................... 321
Chapter 13 Surface-Science Models with Chemical Complexity ........ 326
Christian Hess
13.1 Introduction ................................................. 326
13.2 Surface-Science Models with Chemical Complexity .............. 327
13.2.1 Preparation ........................................... 327
13.2.2 Characterization ...................................... 328
13.3 Studies on Silica-Supported Vanadium Oxide ................... 330
13.3.1 XPS Results on Planar Systems ......................... 330
13.3.2 Comparison with Powder Catalysts ...................... 332
13.3.2.1 Loading Dependence ........................... 332
13.3.2.2 Dehydrated State ............................. 335
13.4 Conclusions .................................................. 337
Acknowledgement .............................................. 337
References ................................................... 337
Chapter 14 Mechanistic Aspects of Short Contact Time Oxidative
Functionalization of Propane and Ethane from Temporal Analysis
of Products ....................................................... 340
Evgenii V. Kondratenko
14.1 Introduction ................................................. 340
14.2 Catalytic Performance of Nonreducible and Reducible Metal
Oxides ....................................................... 342
14.3 Mechanistic Analysis of Heterogeneous Reaction Pathways ...... 344
14.3.1 Microkinetics of Oxygen Activation .................... 344
14.3.2 Reactivity of Adsorbed Oxygen Species for Oxygen
Isotopic Exchange ..................................... 346
14.3.3 Oxygen-Assisted Heterogeneous Activation of C-H
Bond in C2H6 and C3H8 ................................. 347
14.4 Interplay Between Heterogeneous and Homogeneous Reaction
Pathways ..................................................... 348
14.4.1 Oxidative Dehydrogenation of Ethane ................... 348
14.4.2 Oxidative Dehydrogenation of Propane .................. 349
14.5 Conclusions .................................................. 352
References ................................................... 353
Chapter 15 Characteristics of Selective Oxidation Reactions ....... 355
Robert Schlögl and Christian Hess
15.1 Introduction ................................................. 355
15.2 Activation and Reoxidation ................................... 356
15.3 Self-Supported Systems ....................................... 374
15.4 Conclusions .................................................. 381
References ........................................................ 383
Chapter 16 Reaction Engineering of Oxidation Reactions ............ 398
Arne Dinse and Reinhard Schomäcker
16.1 Introduction ................................................. 398
16.2 Basic Reactor Models ......................................... 399
16.3 Conversion, Selectivity and Yield ............................ 401
16.4 Mass Balance ................................................. 404
16.5 Heat-Balance and Heat-Transfer Effects ....................... 408
16.6 Effects of Residence Time and Residence-Time Distribution .... 410
16.7 Mass-Transfer Limitations .................................... 411
16.8 Applied Industrial Reactor Designs ........................... 413
16.9 New Developments in Reactor Design ........................... 420
References ................................................... 424
Chapter 17 Outlook ................................................ 427
Christian Hess
Subject Index ..................................................... 430
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