Microwaves in Catalysis: Methodology and Applications

List of Contributors XVII
Preface XXI

1 General Introduction to Microwave Chemistry 1
Satoshi Horikoshi and Nick Serpone

1.1 ElectromagneticWaves and Dielectric Materials 1
1.2 Microwave Heating 2
1.3 The Various Types of Microwave Heating Phenomena 4
1.3.1 Conduction Loss Heating (Eddy Current Loss and Joule Loss) 5
1.3.2 Dielectric Heating 5
1.3.3 Magnetic Loss Heating (Eddy Current Loss and Hysteresis Loss Heating) 6
1.3.4 Penetration Depth of Microwaves 6
1.4 Fields of Applications with Microwave Heating 9
1.5 Microwaves in Solid Material Processing 11
1.6 Microwaves in Organic Syntheses 12
1.7 Microwave Chemical Equipment 12
1.8 Chemical Reactions Using the Characteristics of Microwave Heating 17
1.9 Microwave Frequency Effect in Chemical Syntheses 21
1.10 Summary 25
References 25

Part I Fundamentals 29

2 Loss Mechanisms and Microwave-Specific Effects in Heterogeneous Catalysis 31
A.E. Stiegman

2.1 Introduction 31
2.2 Heterogeneous Catalyst Systems 33
2.3 Physics of Microwave Absorption 33
2.4 Microwave Loss Processes in Solids 35
2.4.1 Dielectric Loss 35
2.4.2 Charge Carrier Processes 36
2.4.2.1 Conduction Loss 36
2.4.2.2 Space–Charge Recombination 37
2.4.2.3 Dipolar Loss 38
2.4.3 Magnetic Loss Processes 40
2.5 Loss Processes and Microwave-Specific Catalysis: Lessons from Gas–Carbon Reactions 41
2.5.1 Thermochemical Considerations 42
2.6 Final Comments on Microwave-Specific Effects in Heterogeneous Catalysis 45
Acknowledgments 45
References 46

3 Transport Phenomena and Thermal Property under Microwave Irradiation 49
Yusuke Asakuma

3.1 Introduction 49
3.2 Bubble Formation 50
3.3 Convection 53
3.4 Surface Tension 56
3.5 Discussion of Nonthermal Effect for Nanobubble Formation 58
References 59

4 Managing Microwave-Induced Hot Spots in Heterogeneous Catalytic Systems 61
Satoshi Horikoshi and Nick Serpone

4.1 What Are Hot Spots? 61
4.2 Microwaves in Heterogeneous Catalysis 61
4.3 Microwave-Induced Formation of Hot Spots in Heterogeneous Catalysis 63
4.3.1 Hot Spot Phenomenon 63
4.3.2 Mechanism(s) of Formation of Hot Spots 68
4.3.3 Particle Aggregation by Polarization of Activated Carbon Particulates 69
4.3.4 Control of the Occurrence of Hot Spots 73
References 75

Part II Applications – Preparation of Heterogeneous Catalysts 77

5 Preparation of Heterogeneous Catalysts by a Microwave Selective Heating Method 79
Satoshi Horikoshi and Nick Serpone

5.1 Introduction 79
5.2 Synthesis of Metal Catalysts on Carbonaceous Material Supports 79
5.3 Photocatalysts 81
5.3.1 Preparation of TiO2/AC Particles 83
5.3.2 Proposed Mechanism of Formation of TiO2/AC Particles 86
5.3.3 Photoactivity ofMW-Prepared TiO2/AC Composite Particles in the Degradation of Isopropanol 87
5.4 Microwave-Assisted Syntheses of Catalytic Materials for Fuel Cell Applications 88
5.4.1 Microwave-Assisted Synthesis of Pt/C Catalyst Particulates for a H2 Fuel Cell 89
5.4.2 Preparation of Nanocatalysts for a Methanol Fuel Cell 91
5.4.3 Effects of pH on Pt Particle Size and Electrocatalytic Activity of Pt/CNTs for Methanol Electro-oxidation 93
5.5 Other Catalysts Prepared by Microwave-Related Procedures 94
5.6 Concluding Remarks 103
References 103

Part III Applications – Microwave Flow Systems and Microwave Methods Coupled to Other Techniques 109

6 Microwaves in Cu-Catalyzed Organic Synthesis in Batch and Flow Mode 111
Faysal Benaskar, Narendra Patil, Volker Rebrov, Jaap Schouten, and Volker Hessel

6.1 Introduction 111
6.2 Microwave-Assisted Copper Catalysis for Organic Syntheses in Batch Processes 112
6.2.1 Bulk and Nano-structured Metals in a Microwave Field 112
6.2.1.1 Interaction of Bulk Metal with Microwaves 112
6.2.1.2 Metallic Catalyst Particle Size and Shape Effect on Microwave Heating 113
6.2.1.3 Polymetallic Systems in Microwave Chemistry 115
6.2.2 Microwave-Assisted Copper Catalysis for Chemical Synthesis 116
6.2.2.1 Bulk Copper Particles for Catalysis and Microwave Interaction 116
6.2.2.2 Microwave-Assisted Copper-Catalyzed Bond Formation Reactions 117
6.2.3 Supported Cu-Based Catalyst for Sustainable Catalysis in Microwave Field 120
6.2.3.1 Microwave Activation and Synthesis of Cu-Based Heterogeneous Catalysts 120
6.2.3.2 Cu-Supported Catalyst Systems for C–O, C–C, C–S, and C–N Coupling Reactions 121
6.3 Microwave-Assisted Copper Catalysis for Organic Syntheses in Flow Processes 122
6.3.1 Microwave-Assisted Catalyzed Organic Synthesis in Flow Processes 122
6.3.1.1 Microwave Heating in Homogeneously Catalyzed Processes 122
6.3.1.2 Microwave Energy Efficiency and Uniformity in Catalyzed Flow Processes 124
6.3.2 Structured Catalyst in Microwave-Assisted Flow Processing for Organic Reactions 130
6.3.2.1 Thin-Film Flow Reactors for Organic Syntheses 130
6.3.2.2 Structured Fixed-Bed Reactors for Flow Synthesis 131
6.3.2.3 Scale-Up of Microwave-Assisted Flow Processes 133
6.4 Concluding Remarks 136
References 136

7 Pilot Plant for Continuous Flow Microwave-Assisted Chemical Reactions 141
Mitsuhiro Matsuzawa and Shigenori Togashi

7.1 Introduction 141
7.2 Continuous Flow Microwave-Assisted Chemical Reactor 142
7.2.1 Basic Structure 142
7.3 Pilot Plant 145
7.3.1 Design ofWaveguide 145
7.3.2 Configuration of Pilot Plant 147
7.3.3 Water Heating Test 148
7.3.4 Sonogashira Coupling Reaction 151
7.4 Conclusions 153
Acknowledgment 154
References 154

8 Efficient Catalysis by Combining Microwaves with Other Enabling Technologies 155
Giancarlo Cravotto, Laura Rinaldi, and Diego Carnaroglio

8.1 Introduction 155
8.2 Catalysis with Hyphenated and Tandem Techniques 157
8.3 Microwave and Mechanochemical Activation 159
8.4 Microwave and UV Irradiation 162
8.5 Microwave and Ultrasound 164
8.6 Conclusions 166
References 166

Part IV Applications – Organic Reactions 171

9 Applications of Microwave Chemistry in Various Catalyzed Organic Reactions 173
Rick Arneil Desabille Arancon, Antonio Angel Romero, and Rafael Luque

9.1 Introduction 173
9.1.1 Homogeneous Catalysis 175
9.2 Microwave-Assisted Reactions in Organic Solvents 175
9.3 Microwave-Assisted Reactions inWater-Coupling Reactions 179
9.3.1 The Heck Reactions 180
9.3.2 The Suzuki Reaction 186
9.4 Conclusions and Prospects 190
Acknowledgments 190
References 191

10 Microwave-Assisted Solid Acid Catalysis 193
Hyejin Cho, Christian Schäfer, and Béla Török

10.1 Introduction 193
10.2 Microwave-Assisted Clay Catalysis 193
10.3 Zeolites in Microwave Catalysis 199
10.4 Microwave Application of Other Solid Acid Catalysts 205
10.4.1 Heteropoly Acids 205
10.4.2 Acidic Ion-Exchange Resins (Nafion-H, Amberlyst, Dowex) 206
10.4.2.1 Nafion-H 206
10.4.2.2 Amberlyst 207
10.4.2.3 Dowex 208
10.5 Conclusions and Outlook 209
References 209

11 Microwave-Assisted Enzymatic Reactions 213
Takeo Yoshimura, ShigeruMineki, and Shokichi Ohuchi

11.1 Introduction 213
11.2 Synthewave (ProLabo) 217
11.2.1 Lipase 217
11.2.2 Glucosidase 220
11.3 Discover Series (CEM) 220
11.3.1 Lipase (Synthesis, Esterification) 220
11.3.2 Enzymatic Resolution 228
11.3.3 β-Glucosidase, β-Galactosidase 232
11.3.4 Aldolase 233
11.4 Mechanism of the Microwave-Assisted Enzymatic Reaction 233
References 236

Part V Applications – Hydrogenation and Fuel Formation 239

12 Effects of Microwave Activation in Hydrogenation–Dehydrogenation Reactions 241
Leonid M. Kustov

12.1 Introduction 241
12.2 Specific Features of Catalytic Reactions Involving Hydrogen 242
12.3 Hydrogenation Processes under MWConditions 246
12.4 Dehydrogenation 250
12.5 Hydrogen Storage 252
12.6 Hydrogenation of Coal 254
Acknowledgment 254
References 254

13 Hydrogen Evolution from Organic Hydrides throughMicrowave Selective Heating in Heterogeneous Catalytic Systems 259
Satoshi Horikoshi and Nick Serpone

13.1 Situation of Hydrogen Energy and Feature of Stage Methods 259
13.2 Selection of Organic Hydrides as the Hydrogen Carriers 261
13.3 Dehydrogenation of Hydrocarbons with Microwaves in Heterogeneous Catalytic Media 262
13.3.1 Selective Heating by the Microwave Method 262
13.3.2 Dehydrogenation of Tetralin in a Pt/AC Heterogeneous Catalytic Dispersion Subjected to a Microwave Radiation Field 263
13.3.3 Effects of the Tetralin: Pt/AC Ratio on Tetralin Dehydrogenation 264
13.3.4 Dehydrogenation of an Organic Carrier in a Continuous Flow System 266
13.3.5 Dehydrogenation of Methylcyclohexane in a Microwave Fixed-Bed Reactor 269
13.3.6 Simulation Modeling for Microwave Heating of Pt/AC in the Methylcyclohexane Solution 271
13.4 Dehydrogenation of Methane with Microwaves in a Heterogeneous Catalytic System 272
13.5 Problems and Improvements of Microwave-Assisted Heterogeneous Catalysis 273
Acknowledgments 277
References 277

Part VI Applications – Oil Refining 281

14 Microwave-Stimulated Oil and Gas Processing 283
Leonid M. Kustov

14.1 Introduction 283
14.2 Early Publications 283
14.3 Use of Microwave Activation in Catalytic Processes of Gas and Oil Conversions 285
14.3.1 Hydrogen Production 285
14.3.2 CO2 Conversion 286
14.3.3 Synthesis Gas (Syngas) Production 286
14.3.4 Methane Decomposition 287
14.3.5 Methane Steam Reforming 288
14.3.6 Oxidative Coupling of Methane 288
14.3.7 Partial Oxidation and Other Hydrocarbon Conversion Processes 291
14.3.8 Oxidative Dehydrogenation 294
14.3.9 Oil Processing 295
14.4 Prospects for the Use of Microwave Radiation in Oil and Gas Processing 295
Acknowledgment 297
References 297

Part VII Applications – Biomass andWastes 301

15 Algal Biomass Conversion under Microwave Irradiation 303
Shuntaro Tsubaki, Tadaharu Ueda, and Ayumu Onda

15.1 Introduction 303
15.2 Microwave Effect on Hydrothermal Conversion – Analysis Using Biomass Model Compounds 304
15.2.1 Degradation Kinetics of Neutral Sugars under Microwave Heating 304
15.2.2 Effects of Ionic Conduction on Hydrolysis of Disaccharides under Hydrothermal Condition 308
15.3 Hydrolysis of Biomass Using Ionic Conduction of Catalysts 309
15.3.1 Hydrolysis of Starch and Crystalline Cellulose Using Microwave Irradiation and Polyoxometalate Cluster 309
15.3.2 Hydrolysis Fast-Growing Green Macroalgae Using Microwave Irradiation and Polyoxometalate Cluster 311
15.4 Dielectric Property of Algal Hydrocolloids inWater 313
15.4.1 Comparison of Dielectric Property of Aqueous Solution of Hydrocolloids Obtained from Algae and Land Plants 313
15.4.2 The Effects of the Degree of Substitution of Acidic Functional Groups on Dielectric Property of Aqueous Solution of Algal Hydrocolloids 315
15.4.3 The Correlation of Loss Tangent at 2.45 GHz and Other Physical Properties of Sodium Alginates and Carrageenans inWater 316
15.5 Summary and Conclusions 319
Acknowledgments 319
References 319

16 Microwave-Assisted Lignocellulosic Biomass Conversion 323
TomohikoMitani and TakashiWatanabe

16.1 Introduction 323
16.2 Lignocellulosic Biomass Conversion 324
16.3 Multi-mode Continuous Flow Microwave Reactor 325
16.4 Direct-Irradiation Continuous Flow Microwave Reactor 327
16.4.1 Concept of Reactor 327
16.4.2 Designing of Microwave Irradiation Section 327
16.4.3 Prototypes of Reactors 329
16.5 Pilot-Plant-Scale Continuous Flow Microwave Reactor 331
16.5.1 Concept of Reactor 331
16.5.2 Designing of Microwave Irradiation Section 331
16.5.3 Demonstration Experiments of Microwave Pretreatment 333
16.6 Summary and Conclusions 335
References 335

17 Biomass andWaste Valorization under Microwave Activation 337
Leonid M. Kustov

17.1 Introduction 337
17.2 Vegetable Oil and Glycerol Conversion 338
17.3 Conversion of Carbohydrates 339
17.4 Cellulose Conversion 340
17.5 Lignin Processing 342
17.6 Waste and Renewable Raw Material Processing 343
17.7 Carbon Gasification 347
17.8 Prospects for the Use of Microwave Irradiation in the Conversion of Biomass and Renewables 348
Acknowledgment 350
References 350

Part VIII Applications – Environmental Catalysis 355
18 Oxidative and Reductive Catalysts for Environmental Purification Using Microwaves 357
Takenori Hirano

18.1 Introduction 357
18.2 Microwave Heating of Catalyst Oxides Used for Environmental Purification 358
18.3 Microwave-Assisted Catalytic Oxidation of VOCs, Odorants, and Soot 361
18.4 Microwave-Assisted Reduction of NOx and SO2 364
18.5 Conclusions 367
References 367

19 Microwave-/Photo-Driven Photocatalytic Treatment of Wastewaters 369
Satoshi Horikoshi and Nick Serpone

19.1 Situation ofWastewater Treatment by Photocatalytic Classical Methods 369
19.2 Experimental Setup of an Integrated Microwave/Photoreactor System 370
19.3 Microwave-/Photo-Driven PhotocatalyticWastewater Treatment 371
19.3.1 Degradation of Rhodamine B Dye 371
19.3.2 Change of TiO2 Surface Condition under a Microwave Field 376
19.3.3 Specific Nonthermal Microwave Effect(s) in TiO2 Photoassisted Reactions 377
19.3.4 Microwave Frequency Effects on the Photoactivity of TiO2 379
19.3.5 Increase in Radical Species on TiO2 under Microwave Irradiation 380
19.3.6 Microwave Nonthermal Effect(s) as a Key Factor in TiO2 Photoassisted Reactions 382
19.4 Microwave Discharge Electrodeless Lamps (MDELs) 386
19.4.1 The Need for More Efficient UV Light Sources 386
19.4.2 Purification ofWater Using TiO2-Coated MDEL Systems in Natural Disasters 387
19.5 Summary Remarks 389
References 389

Index 393