Zeolites and CatalysisSynthesis, Reactions and Applications Edited by Jiˇr´ı ˇCejka, Avelino Corma, and Stacey Zones... Zeolites and CatalysisSynthesis, Reactions and Applications Edited
Trang 1Zeolites and Catalysis
Synthesis, Reactions and Applications
Edited by
Jiˇr´ı ˇCejka, Avelino Corma, and Stacey Zones
Trang 3Zeolites and Catalysis
Edited by
Jiˇr´ı ˇCejka, Avelino Corma, and Stacey Zones
Trang 4Blaser, H.-U., Federsel, H.-J (eds.)
Barbaro, P., Bianchini, C (eds.)
Catalysis for Sustainable Energy
New Approaches based on Synthesis,
Characterization and Modeling
Jackson, S D., Hargreaves, J S J (eds.)
Metal Oxide Catalysis
2009 ISBN: 978-3-527-31815-5
Ding, K., Uozumi, Y (eds.)
Handbook of Asymmetric Heterogeneous Catalysis
2008 ISBN: 978-3-527-31913-8
Ertl, G., Kn¨ozinger, H., Sch¨uth, F.,Weitkamp, J (eds.)
Handbook of Heterogeneous Catalysis
Eight Volumes
2008 ISBN: 978-3-527-31241-2
Trang 5Zeolites and Catalysis
Synthesis, Reactions and Applications
Edited by
Jiˇr´ı ˇCejka, Avelino Corma, and Stacey Zones
Trang 6Prof Dr Jiˇr´ı ˇCejka
Academy of Sciences of the Czech Republic
Heyrovsk´y Institute of Physical Chemistry
Dokjˇskova
Dolejskova 3
182 23 Prague 8
Czech Republic
Prof Dr Avelino Corma
University Politecnica de Valencia
Institute de Tecnologia Quimica
Avenida de los Naranjos s/n
46022 Valencia
Spain
Prof Dr Stacey I Zones
Chevron Texaco Energy Research
and Technology Company
Library of Congress Card No.: applied for
British Library Cataloguing-in-Publication Data
A catalogue record for this book is available from the British Library.
Bibliographic information published by the Deutsche Nationalbibliothek
The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbib- liografie; detailed bibliographic data are available on the Internet at
Composition Laserwords Private Limited, Chennai
Printing and Bookbinding strauss GmbH, M¨orlenbach
Cover Design Formgeber, Eppelheim
Printed in the Federal Republic of Germany Printed on acid-free paper
ISBN: 978-3-527-32514-6
Trang 7Contents to Volume 1
Preface XIII
List of Contributors XVII
1 Synthesis Mechanism: Crystal Growth and Nucleation 1
Pablo Cubillas and Michael W Anderson
1.2.12 Growth Mechanisms: Rough and Smooth Surfaces 10
1.3 Nucleation and Growth in Zeolites 11
1.4.2 Solution Chemistry – Oligomers and Nanoparticles 17
1.4.2.1 Nuclear Magnetic Resonance 17
1.4.2.2 Mass Spectrometry 19
Zeolites and Catalysis, Synthesis, Reactions and Applications Vol 1.
Edited by Jiˇr´ı ˇ Cejka, Avelino Corma, and Stacey Zones
Copyright 2010 WILEY-VCH Verlag GmbH & Co KGaA, Weinheim
Trang 81.5.6 Metal Organic Frameworks 47
1.6 Conclusions and Outlook 49
2.4 Dry Gel Conversion Syntheses 61
2.5 Low Water Syntheses 62
3.2 Hydrothermal, Solvothermal, and Ionothermal Synthesis 89
3.3 Ionothermal Aluminophosphate Synthesis 90
3.4 Ionothermal Synthesis of Silica-Based Zeolites 92
Trang 9Contents VII
3.5 Ionothermal Synthesis of Metal Organic Frameworks and
Coordination Polymers 92
3.6 Ambient Pressure Ionothermal Synthesis 93
3.7 The Role of Cation-Templating, Co-Templating, or No
Templating 95
3.8 The Role of the Anion – Structure Induction 97
3.9 The Role of Water and Other Mineralizers 99
3.10 Unstable Ionic Liquids 101
3.11 Summary and Outlook 101
References 102
4 Co-Templates in Synthesis of Zeolites 107
Joaquin P´erez-Pariente, Raquel Garc´ıa, Luis G´omez-Hortig¨ uela,
and Ana Bel´en Pinar
4.2 Templating of Dual-Void Structures 108
4.3 Crystallization of Aluminophosphate-Type Materials 113
4.4 Combined Use of Templating and Pore-Filling Agents 116
4.5 Cooperative Structure-Directing Effects of Organic Molecules and
5 Morphological Synthesis of Zeolites 131
Sang-Eon Park and Nanzhe Jiang
5.2 Morphology of Large Zeolite Crystals 132
5.2.1 Large Crystals of Natural Zeolites 132
5.2.2 Synthesis of Large Zeolite Crystals 133
5.3 Morphology Control of MFI Zeolite Particles (of Size Less than
100µm) 138
5.3.1 Dependence of Structure-Directing Agents (SDAs) 139
5.3.2 Dependence on Alkali-Metal Cations 141
5.4 Morphological Synthesis by MW 142
5.4.1 Examples of MW Dependency 142
5.4.2 Morphological Fabrication by MW 143
5.4.3 Formation Scheme of Stacked Morphology 146
Trang 10Acknowledgments 150
References 150
6 Post-synthetic Treatment and Modification of Zeolites 155
Cong-Yan Chen and Stacey I Zones
6.2 Direct Synthesis of Zeolites 155
6.3 Post-synthetic Treatment and Modification of Zeolites 157
6.3.1 Aluminum Reinsertion into Zeolite Framework Using Aqueous
Al(NO3)3Solution under Acidic Conditions 158
6.3.1.1 Experimental Procedures 158
6.3.1.2 One-Step Method versus Two-Step Method 159
6.3.1.3 Effects of the Ratio of Al(NO3)3to Zeolite 160
6.3.1.4 Effects of pH, Time, Temperature, and Other Factors 161
6.3.1.5 Applicable to Medium Pore Zeolite? 161
6.3.2 Synthesis of Hydrophobic Zeolites by Hydrothermal Treatment with
Acetic Acid 162
6.3.2.1 Experimental Procedures 162
6.3.2.2 Highly Crystalline Pure-Silica Zeolites Prepared via This
Technique 163
6.3.2.3 Effects of Type of Acid, pH, Temperature, and Other Factors 163
6.3.2.4 Experimental Results from Our Lab 164
Acknowledgments 167
References 167
7 Structural Chemistry of Zeolites 171
Paul A Wright and Gordon M Pearce
7.2.4 Faujasitic Zeolites X and Y as Typical Examples 178
7.2.5 Key Inorganic Cation-Only Zeolites Pre-1990 179
7.2.6 Structures Templated by Simple Alkylammonium Ions 182
7.2.7 Lessons from Nature 184
7.3 The Expanding Library of Zeolite Structures: Novel Structures,
Novel Features 185
7.3.1 Introduction 185
7.3.2 Novel Structures and Pore Geometries 187
7.3.3 Expansion of the Coordination Sphere of Framework Atoms 191
Trang 11Contents IX
7.3.4 The Current Limits of Structural Complexity in Zeolites 193
7.3.5 Chirality and Mesoporosity 195
7.3.6 Ordered Vacancies and Growth Defects 197
7.3.7 Zeolites from Layered Precursors 198
7.3.8 Substitution of Framework Oxygen Atoms 199
7.4.2 Outlook 202
References 204
8 Vibrational Spectroscopy and Related In situ Studies of Catalytic
Reactions Within Molecular Sieves 209
Eli Stavitski and Bert M Weckhuysen
8.2 Acidity Determination with IR Spectroscopy of Probe Molecules 211
8.3 Zeolite Synthesis Processes 218
8.4 Selection of Zeolite-Based Catalytic Reactions 221
8.4.1 Catalytic Decomposition of Nitric Oxides 221
9 Textural Characterization of Mesoporous Zeolites 237
Lei Zhang, Adri N.C van Laak, Petra E de Jongh, and Krijn P de Jong
Trang 129.3.6 In situ Optical and Fluorescence Microscopy 271
Acknowledgments 274
References 274
10 Aluminum in Zeolites: Where is it and What is its Structure? 283
Jeroen A van Bokhoven and Nadiya Danilina
10.1 Introduction 283
10.2 Structure of Aluminum Species in Zeolites 284
10.2.1 Reversible versus Irreversible Structural Changes 285
10.2.2 Cautionary Note 286
10.2.3 Development of Activity and Changing Aluminum Coordination 286
10.3 Where is the Aluminum in Zeolite Crystals? 289
10.3.1 Aluminum Zoning 289
10.3.2 Aluminum Distribution Over the Crystallographic T Sites 292
10.4 Summary and Outlook 296
Acknowledgment 298
References 298
11 Theoretical Chemistry of Zeolite Reactivity 301
Evgeny A Pidko and Rutger A van Santen
11.5 Molecular Recognition and Confinement-Driven Reactivity 321
11.6 Structural Properties of Zeolites: Framework Al Distribution and
Structure and Charge Compensation of Extra-framework Cations 326
11.7 Summary and Outlook 330
References 331
12 Modeling of Transport and Accessibility in Zeolites 335
Sof´ıa Calero Diaz
12.1 Introduction 335
12.2 Molecular Models 336
12.2.1 Modeling Zeolites and Nonframework Cations 336
12.2.2 Modeling Guest Molecules 337
12.3 Simulation Methods 338
12.3.1 Computing Adsorption 339
Trang 13Contents XI
12.3.2 Computing Free Energy Barriers 341
12.3.3 Computing Volume-Rendered Pictures, Zeolite Surface Areas,
and Zeolite Pore Volumes 343
12.3.4 Computing Diffusion 344
12.4 Molecular Modeling Applied to Processes Involving Zeolites 346
12.4.1 Applications in Technological Processes 346
12.4.1.1 Molecular Modeling of Confined Water in Zeolites 346
12.4.1.2 Molecular Modeling of Hydrocarbons in Zeolites 348
12.4.1.3 Molecular Modeling of Separation of Mixtures in Zeolites 349
12.4.2 Applications in Green Chemistry 351
12.4.2.1 Carbon Dioxide Capture 351
12.4.2.2 Natural Gas Purification 352
12.5 Summary and Outlook 353
Acknowledgments 354
References 354
13 Diffusion in Zeolites – Impact on Catalysis 361
Johan van den Bergh, Jorge Gascon, and Freek Kapteijn
13.2.4 Diffusion Measurement Techniques 365
13.2.5 Relating Diffusion and Catalysis 366
13.3 Diffusion in Zeolites: Potential Issues 368
13.3.1 Concentration Dependence of Diffusion 368
13.3.2 Single-File Diffusion 370
13.3.3 Surface Barriers 372
13.3.4 The Thiele Concept: A Useful Approach in Zeolite Catalysis? 374
13.4 Pore Structure, Diffusion, and Activity at the Subcrystal Level 375
13.5 Improving Transport through Zeolite Crystals 379
13.6 Concluding Remarks and Future Outlook 382
References 383
Contents to Volume 2
14 Special Applications of Zeolites 389
V´ıctor Sebasti´an, Clara Casado, and Joaqu´ın Coronas
15 Organization of Zeolite Microcrystals 411
Kyung Byung Yoon
Trang 1416 Industrial Potential of Zeolites 449
Giuseppe Bellussi, Angela Carati, and Roberto Millini
17 Catalytically Active Sites: Generation and Characterization 493
Michael Hunger
18 Cracking and Hydrocracking 547
Marcello Rigutto
19 Reforming and Upgrading of Diesel Fractions 585
Carlo Perego, Vincenzo Calemma, and Paolo Pollesel
20 Recent Development in Transformations of Aromatic Hydrocarbons
over Zeolites 623
Sulaiman Al-Khattaf, Mohammad Ashraf Ali, and Jiˇr´ı ˇ Cejka
21 Advanced Catalysts Based on Micro- and Mesoporous Molecular Sieves
for the Conversion of Natural Gas to Fuels and Chemicals 649 Agust´ın Mart´ınez, Gonzalo Prieto, Andr´es Garc´ıa-Trenco,
and Ernest Peris
22 Methanol to Olefins (MTO) and Methanol to Gasoline (MTG) 687
Michael St¨ocker
23 Metals in Zeolites for Oxidation Catalysis 713
Takashi Tatsumi
24 Environmental Catalysis over Zeolites 745
Gabriele Centi and Siglinda Perathoner
25 Zeolites as Catalysts for the Synthesis of Fine Chemicals 775
Maria J Climent, Avelino Corma, and Sara Iborra
26 Zeolites and Molecular Sieves in Fuel Cell Applications 827
King Lun Yeung and Wei Han
Index 863
Trang 15Contents to Volume 1
1 Synthesis Mechanism: Crystal Growth and Nucleation 1
Pablo Cubillas and Michael W Anderson
2 Synthesis Approaches 57
Karl G Strohmaier
3 Ionothermal Synthesis of Zeolites and Other Porous Materials 87
Russell E Morris
4 Co-Templates in Synthesis of Zeolites 107
Joaquin P´erez-Pariente, Raquel Garc´ıa, Luis G´omez-Hortig¨ uela, and Ana Bel´en Pinar
5 Morphological Synthesis of Zeolites 131
Sang-Eon Park and Nanzhe Jiang
6 Post-synthetic Treatment and Modification of Zeolites 155
Cong-Yan Chen and Stacey I Zones
7 Structural Chemistry of Zeolites 171
Paul A Wright and Gordon M Pearce
8 Vibrational Spectroscopy and Related In situ Studies of Catalytic
Reactions Within Molecular Sieves 209
Eli Stavitski and Bert M Weckhuysen
9 Textural Characterization of Mesoporous Zeolites 237
Lei Zhang, Adri N.C van Laak, Petra E de Jongh, and Krijn P de Jong
10 Aluminum in Zeolites: Where is it and What is its Structure? 283
Jeroen A van Bokhoven and Nadiya Danilina
Zeolites and Catalysis, Synthesis, Reactions and Applications Vol 2.
Edited by Jiˇr´ı ˇ Cejka, Avelino Corma, and Stacey Zones
Copyright 2010 WILEY-VCH Verlag GmbH & Co KGaA, Weinheim
Trang 1611 Theoretical Chemistry of Zeolite Reactivity 301
Evgeny A Pidko and Rutger A van Santen
12 Modeling of Transport and Accessibility in Zeolites 335
Sof´ıa Calero Diaz
13 Diffusion in Zeolites – Impact on Catalysis 361
Johan van den Bergh, Jorge Gascon, and Freek Kapteijn
Contents to Volume 2
Preface XIII
List of Contributors XVII
14 Special Applications of Zeolites 389
V´ıctor Sebasti´an, Clara Casado, and Joaqu´ın Coronas
14.1 Introduction 389
14.2 Zeolite Membranes 389
14.2.1 Membrane Reactors and Microreactors 390
14.2.2 Zeolite-Based Gas Sensors 392
15 Organization of Zeolite Microcrystals 411
Kyung Byung Yoon
Trang 17Contents VII
15.2.1.5 Four Key Processes Occurring during Monolayer Assembly 417
15.2.1.6 Effect of Method on Rate, DCP, Coverage, and Binding Strength 424
15.2.1.7 Factors Affecting Binding Strengths 426
15.2.1.8 Driving Forces for Uniform Orientation and Close Packing 427
15.2.2 Patterned Monolayer Assembly on Substrates 429
15.2.3 Multilayer Assembly on Substrates 431
15.2.4 Organization into 2D Arrays on Water 431
15.2.5 Organization into Surface-Aligned Zeolite Microballs 434
15.2.6 Self-Assembly of Substrate-Tethering Zeolite Crystals with
15.4 Current and Future Applications 441
15.5 Summary and Outlook 442
Acknowledgments 444
References 444
16 Industrial Potential of Zeolites 449
Giuseppe Bellussi, Angela Carati, and Roberto Millini
16.1 Introduction 449
16.2 Application of Zeolites in Slurry Processes 450
16.2.1 TS-1 Based Catalyst for Liquid-Phase Oxidation Processes 451
16.2.2 New Advance in Slurry Phase Reaction with Zeolitic Catalysts 453
16.3 Rebalancing the Refinery Products Slate 455
16.3.1 Bottom Cracking Conversion 457
16.3.2 LCO Upgrading 459
16.3.3 Olefins Oligomerization 461
16.4 Advanced Separation Technologies 462
16.5 Zeolites and Environmental Protection: Groundwater
Remediation 467
16.6 New Materials for Emerging Applications 471
16.6.1 Zeolites 471
16.6.2 Hierarchical Zeolites 473
16.6.3 Silica-Based Crystalline Organic–Inorganic Hybrid Materials 479
16.7 Summary and Outlook 484
References 485
17 Catalytically Active Sites: Generation and Characterization 493
Michael Hunger
17.1 Introduction 493
17.2 Acid Sites in Zeolites 494
17.2.1 Nature of Acid Sites 494
17.2.2 Formation of Brønsted and Lewis Acid Sites 496
Trang 1817.3 Characterization of Acid Sites 498
17.3.1 Catalytic Test Reactions 498
17.3.2 Titration with Bases 500
17.3.3 Temperature-Programmed Desorption of Bases 501
17.3.4 Microcalorimetry 504
17.3.5 FTIR Spectroscopy 508
17.3.6 NMR Spectroscopy 514
17.4 Base Catalysis 521
17.4.1 Nature of Base Sites 521
17.4.2 Formation of Base Sites 522
17.5 Characterization of Base Sites in Zeolites 523
17.5.1 Test Reactions 523
17.5.2 Analytical and Spectroscopic Methods 525
17.6 Metal Clusters in Zeolites 529
17.6.1 Nature of Metal Clusters 529
17.6.2 Formation of Metal Clusters 530
17.7 Characterization of Metal Clusters in
18.1.1 The Oil Refinery – Where to Find Zeolites in It, and Why – and the
Place of Hydrocracking and Catalytic Cracking 547
18.1.2 The Changing Environment for Refining 549
18.2.1 The FCC Process 551
18.2.2 The FCC Catalyst, and Catalytic Chemistry 555
18.2.3 Residue Cracking and the Effect of Deposited Metals on the
Catalyst 558
18.2.4 Light Alkenes by Addition of ZSM-5 559
18.2.5 Potential Use of Other Zeolites in FCC 561
18.3.1 The Hydrocracking Process 561
18.3.2 Feedstocks and Products 563
18.3.3 Hydrocracking Catalyst Systems, and Catalytic Chemistry 566
18.3.4 Zeolite Y in Hydrocracking 570
18.3.5 New Catalyst Developments 575
18.3.6 Residue Conversion – Some Notes 576
18.4 Summary and Outlook 576
References 578
Trang 19Contents IX
19 Naphtha Reforming and Upgrading of Diesel Fractions 585
Carlo Perego, Vincenzo Calemma, and Paolo Pollesel
19.3.1.1 Catalytic Dewaxing via Shape Selective Cracking 605
19.3.1.2 Dewaxing via Isomerization 607
20.3.1 Zeolite Modification by Silicon Deposition 626
20.3.2 Zeolite Modification by Precoking 627
20.3.3 Zeolite Modification by Dealumination 627
20.3.4 Zeolite Modification by Metal Deposition 628
20.3.5 Factors Affecting Toluene Disproportionation 629
20.4 Ethylbenzene Disproportionation 630
20.4.1 Effect of Crystal Size and Surface Modification 631
20.4.2 Kinetic Investigations of Ethylbenzene
20.6.2.1 Modification of the External Surface of Zeolites 638
20.6.3 Ethylation of Toluene and Ethylbenzene 640
20.7 Miscellaneous 642
20.8 Summary and Outlook 643
Acknowledgments 644
References 644
Trang 2021 Advanced Catalysts Based on Micro- and Mesoporous Molecular Sieves
for the Conversion of Natural Gas to Fuels and Chemicals 649 Agust´ın Mart´ınez, Gonzalo Prieto, Andr´es Garc´ıa-Trenco,
and Ernest Peris
21.1 Introduction 649
21.2 Direct Conversion of Methane 651
21.2.1 Oxidative Conversion: OCM and Methylation Processes 651
21.2.2 Nonoxidative Methane Homologation and Alkylation
Processes 654
21.2.3 Nonoxidative Methane Dehydroaromatization (MDA) 655
21.3 Syngas Conversion Processes 659
21.3.1 Selective Synthesis of Short-Chain (C2–C4) Olefins 659
21.3.3.2 Syngas to Higher (C2+) Oxygenates 674
21.3.3.3 Carbonylation of MeOH and DME 676
21.4 Summary and Outlook 678
22.2 Mechanism and Kinetics of the MTO and MTG Reactions 690
22.3 Methanol to Olefins (MTO) 697
22.3.1 Catalysts and Reaction Conditions 697
22.3.2 Deactivation 697
22.3.3 Process Technology and Design 699
22.3.4 Commercial Aspects/Economic Impact 700
Trang 2123.2.4 Other Titanium-Containing Zeolites 731
23.2.5 Solvent Effects and Reaction Intermediate 732
23.3 Other-Metal-Containing Zeolites 736
References 739
24 Environmental Catalysis over Zeolites 745
Gabriele Centi and Siglinda Perathoner
25 Zeolites as Catalysts for the Synthesis of Fine Chemicals 775
Maria J Climent, Avelino Corma, and Sara Iborra
25.2.4 Acetalization of Carbonyl Compounds 787
25.2.5 Fischer Glycosidation Reactions 789
25.2.6 Isomerization Reactions: Isomerization of
α-Pinene and α-Pinene Oxide 792
25.2.7 Oxidation and Reduction Reactions 795
Trang 2225.4 Summary and Outlook 819
References 819
26 Zeolites and Molecular Sieves in Fuel Cell Applications 827
King Lun Yeung and Wei Han
26.1 Introduction 827
26.2 Zeolites in Electrolyte Membrane 827
26.2.1 Zeolite Conductivities 829
26.2.2 Zeolite/Polymer Composite Membranes 833
26.2.2.1 Zeolite/PTFE Composite Membranes 839
26.2.2.2 Zeolite/PFSA Composite Membranes 839
26.2.2.3 Zeolite/Chitosan Composite Membranes and Others 840
26.2.2.4 Self-Humidifying Composite Membranes 841
26.2.3 Zeolite and Mesoporous Inorganic Membranes 841
26.3 Zeolite Electrocatalysts 842
26.4 Zeolites and Molecular Sieves in Fuel Processing 844
26.4.1 Removal of Sulfur Compounds in Fuel 845
26.4.2 Hydrogen Production and Purification 845
Trang 23Preface
One can safely say that the impact of zeolites in science and technology in the last
50 years has no precedents in the field of materials and catalysis Although the firstdescription of zeolites dates back up to 250 years ago, the last five decades experi-enced an incredible boom in zeolite research activities resulting in the successfulsynthesis of almost 200 different structural types of zeolites, numerous excellentscientific papers on the synthesis of zeolites, characterization of their properties,and applications of zeolites in adsorption and catalysis that have revolutionized thepetrochemical industry In addition, based on the knowledge of zeolites severalother areas of porous materials have recently emerged including mesoporous ma-terials, hierarchic systems, metal-organic frameworks (cationic-periodic polymers)and mesoporous organosilicas All these materials have substantially increased theportfolio of novel porous materials possessing new interesting properties, but thistopic is not covered in this book
This book consists of two volumes The first one is mostly concentrated on recentadvances in the synthesis of zeolites and understanding of their properties whilethe second volume describes recent achievements in the application of zeolitesmostly in catalysis
More specifically, the first volume starts with a chapter by P Cubillas and M.W.Anderson (Chapter 1) discussing mechanisms of the synthesis of zeolites andzeotypes, including nucleation and crystal growth, employing various microscopictechniques This is followed by a chapter of K Strohmaier (Chapter 2) providing adetailed survey on the synthesis of novel zeolites and different layered precursorsincorporating different metal ions into the framework, and applying ever increasingnumber of structure-directing agents A new approach to the synthesis of zeolitesand other porous materials by ionothermal synthesis combining ionic liquids asthe solvent together with the structure-directing agent is presented by R Morris(Chapter 3) Zeolite synthesis can also be controlled by a simultaneous use of twodifferent templates providing new tool for creative chemistry Nas discussed by thegroup of J P´erez-Pariente (Chapter 4) Morphological control of zeolite crystals isone of the key issues to understand the mechanism of zeolite crystallization as well
as to control the performance of zeolites in various applications as it is outlined byS.-E Park and N Jiang in Chapter 5 Introduction of other elements than siliconinto the zeolite framework can be done not only via synthesis but also in the
Zeolites and Catalysis, Synthesis, Reactions and Applications Vol 1.
Edited by Jiˇr´ı ˇ Cejka, Avelino Corma, and Stacey Zones
Copyright 2010 WILEY-VCH Verlag GmbH & Co KGaA, Weinheim
Trang 24postsynthesis steps as highlighted for deboronation followed by realumination asdescribed by C.Y Chen and S.I Zones (Chapter 6) P.A Wright and G.M Pearceshow how the individual zeolite structures are built from basic secondary buildingunits The authors focus not only on general aspects of zeolite structures but also
on the description of structures of zeolites determined very recently (Chapter 7).Structural and textural characterization of zeolites starts in Chapter 8, written
by E Stavitski and B.M Weckhuysen, providing good examples of application
of vibrational spectroscopy under static conditions that can drive into in situ
catalytic investigations The group of K de Jong (Chapter 9) makes an effort toevaluate different physicochemical methods used for textural characterization ofzeolites Gas physisorption, mercury porosimetry, electron microscopy (including
3D experiments), various NMR techniques up to in situ optical and fluorescence
microscopy are discussed in detail The location, coordination, and accessibility
of framework aluminum are of key importance for acid-catalyzed reactions inzeolites and these issues are addressed by J.A van Bokhoven and N Danilina
in Chapter 10 Theoretical background of zeolite reactivity employing differentcomputational approaches and models is covered in Chapter 11 by E.A Pidko andR.A van Santen S Calero Diaz presents an overview of current developments inmodeling of transport and accessibility in zeolites showing some recent models andsimulation methods that are applied for systems of environmental and industrialinterests (Chapter 12) The final chapter of the first volume is written by the group
of F Kapteijn (Chapter 13), in which diffusion in zeolites starting from basicmodels of diffusion up to the role of diffusion in adsorption and catalytic processes
is discussed
The second volume starts with a chapter of the group of J Coronas ing on special applications of zeolites including green chemistry, hybrid materials,medicine, veterinary, optical- and electrical-based applications, multifunctionalfabrics, and nanotechnology (Chapter 14) After that K.B Yoon presents the op-portunities to organize zeolite microcrystals into two- and three-dimensionallyorganized structures and the application of these organized entities in membranes,antibacterial functional fabrics, supramolecularly organized light-harvesting sys-tems, and nonlinear optical films (Chapter 15)
concentrat-The remaining chapters are exclusively devoted to the application of zeolites incatalysis G Bellussi opens this part with a broad overview of current industrialprocesses using zeolites as key components of the catalysts and further challenges
in this area (Chapter 16) Generation, location, and characterization of catalyticallyactive sites are discussed in depth by M Hunger showing different aspects ofshape selectivity and structural effect on the properties of active sites (Chapter 17)
M Rigutto (Chapter 18) stresses the importance of zeolites and the main reasonsfor their application in cracking and hydrocracking, the largest industrial processesemploying zeolites as catalysts Further, C Perego and his coworkers focus onreforming and upgrading of diesel fractions, which with gasoline are by far the mostimportant and valuable key fractions produced by petroleum refineries (Chapter 19).Transformation of aromatic compounds forms the heart of petrochemical processeswith zeolites as key components of all catalysts S Al-Khattaf, M.A Ali, and J ˇCejka
Trang 25of the strategic raw materials in future Novel processes transforming methanolinto olefins or gasoline are covered in Chapter 22 by M St¨ocker Incorporation ofcatalytically active species into zeolite frameworks or channel systems for oxidationreactions is covered in Chapter 23 by T Tatsumi The main attention is devoted
to Ti-silicates G Centi and S Perathoner focus on increasing applicability ofzeolites in environmental catalysis with a particular attention to conversion ofnitrogen oxides (Chapter 24) K.L Yeung and W Han describe the emerging field
of application of zeolites in fuel cells for clean energy generation The authorsshow that zeolites can play an important role in hydrogen production, purification,conditioning, and storage (Chapter 25) The final chapter by the authors fromthe group of A Corma presents possibilities of application of zeolite as catalysts
in the synthesis of fine chemicals The examples discussed include, for example,acylation, hydroxyalkylation, acetalization, isomerization, Diels–Alder, and Fischerglucosidation reactions
Bringing together these excellent chapters describing the cutting edge of zeoliteresearch and practice provides an optimistic view for the bright future of zeolites.The number of new synthesized zeolites is ever increasing and particularly novelextra-large pore zeolites or even chiral zeolitic materials will surely be applied
in green catalytic processes enabling to transform bulkier substrates into desiredproducts In a similar way, application of zeolites in adsorption or separation isone of the most important applications of this type of materials saving particularlyenergy needed for more complex separation processes if zeolites were not available
to do the job Fast development of experimental techniques enables deeper insightinto the structural and textural properties of zeolites, while particularly spectro-scopical methods provide new exciting information about the accessibility of innerzeolite volumes and location and coordination of active sites Catalysis is still themost promising area for application of zeolites, in which novel zeolitic catalystswith interesting shape-selective properties can enhance activities and selectivitiesnot only in traditional areas such as petrochemistry but also in environmentalprotection, pollution control, green chemistry, and biomass conversion Last butnot least, novel approaches in the manipulation and modification of zeolites di-rected to fuel cells, light harvesting, membranes, and sensors clearly evidence alarge potential of zeolites in these new areas of application The only limitation inzeolite research is the lack of our imagination, which slows down our effort andattainment of new exciting achievements
It was our great pleasure working with many friends and excellent researchers
in the preparation of this book We would like to thank sincerely all of them fortheir timely reviews on selected topics and the great effort to put the book together
We believe that this book on zeolites will be very helpful not only for experienced
Trang 26researchers in this field but also students and newcomers will find it as a usefulreference book.
October 2009
Trang 27List of Contributors
Sulaiman Al-Khattaf
King Fahd University of
Petroleum & Minerals (KFUPM)
Mohammad Ashraf Ali
King Fahd University of
Petroleum & Minerals (KFUPM)
Center of Excellence in Refining
Refining & Marketing Division
Research & Technological
Refining & Marketing Division
20097 San Donato Milanese (MI)
Italy
Angela Carati
EnitecnologieSan Donato MilaneseResearch CentreRefining & Marketing DivisionResearch & TechnologicalDevelopment
Department and NanoscienceInstitute of Arag´on
Mar´ıa de Luna 3
50018 ZaragozaSpain
Zeolites and Catalysis, Synthesis, Reactions and Applications Vol 2.
Edited by Jiˇr´ı ˇ Cejka, Avelino Corma, and Stacey Zones
Copyright 2010 WILEY-VCH Verlag GmbH & Co KGaA, Weinheim
Trang 28Gabriele Centi
Universita di Messina
Dip Di Chimica Industriale ed
Ingegneria dei Materiali
University Politecnica de Valencia
Institute de Tecnologia Quimica
Avenida de los Naranjos s/n
46022 Valencia
Spain
Joaqu´ın Coronas
Universidad de Zaragoza
Chemical and Environmental
Engineering Department and
Nanoscience Institute of Arag´on
Instituto de Tecnolog´ıa Qu´ımica
Avenida de los Naranjos s/n
PR China
Michael Hunger
University of StuttgartInstitute of Chemical Technology
70550 StuttgartGermany
Sara Iborra
Universidad Polit´ecnica
de ValenciaInstituto de Tecnolog´ıa Qu´ımicaUPV-CSIC
Avda de los Naranjos s/n
46022 ValenciaSpain
Agust´ın Mart´ınez
UPV-CSICInstituto de Tecnolog´ıa Qu´ımicaAvenida de los Naranjos s/n
46022 ValenciaSpain
Roberto Millini
EnitecnologieSan Donato MilaneseResearch CentreRefining & Marketing DivisionResearch & TechnologicalDevelopment
Via F Maritano 26
20097 San Donato Milanese (MI)Italy
Trang 29List of Contributors XIX
Instituto de Tecnolog´ıa Qu´ımica
Avenida de los Naranjos s/n
46022 Valencia
Spain
Siglinda Perathoner
Universita di Messina
Dip Di Chimica Industriale ed
Ingegneria dei Materiali
Refining & Marketing Division
20097 San Donato Milanese (MI)
Italy
Gonzalo Prieto
UPV-CSIC
Instituto de Tecnolog´ıa Qu´ımica
Avenida de los Naranjos s/n
50018 ZaragozaSpain
Michael St¨ ocker
SINTEF Materials and ChemistryDepartment of HydrocarbonProcess Chemistry
P.O Box 124 Blindern
0314 OsloNorway
Takashi Tatsumi
Tokyo Institute of TechnologyChemical Resources LaboratoryDivision of Catalytic Chemistry4259-R1-9 Nagatsuta-choMidori-ku
Yokohama 226–8503Japan
King Lun Yeung
The Hong Kong University ofScience and TechnologyDepartment of Chemical andBiomolecular EngineeringClear Water Bay KowloonHong Kong
PR China
Kyung Byung Yoon
Sogang UniversityDepartment of ChemistryCenter for Microcrystal AssemblySeoul 121–742
Korea
Trang 311
Synthesis Mechanism: Crystal Growth and Nucleation
Pablo Cubillas and Michael W Anderson
1.1
Introduction
Crystal growth pervades all aspects of solid-state materials chemistry and the tries that rely upon the functionality of these materials In the drive toward greener,more efficient processes crystal engineering is an increasingly important require-ment in materials such as catalysts; semiconductors; pharmaceuticals; gas-storagematerials; opto-electronic crystals; and radio-active waste storage materials In order
indus-to impart this desired functionality it is crucial indus-to control properties such as crystalperfection, crystal size, habit, intergrowths, chirality, and synthesis cost [1]
The issues that concern crystal growth for nanoporous materials are similar
to those that concern all crystal growths Crystal habit and crystal size are ofvital importance to the efficient functioning of these, and any other crystals, forreal application In the extreme case, single-crystal nanoporous films will requiresubstantial skewing of both habit and size from normal bounds – this is currentlyimpossible for zeolites but is being realized to some extent for metal organicframework (MOF) materials Less extreme is the modification of crystal aspectratio, for example, in hexagonal crystal systems where the pore architecture isoften one-dimensional, growth of tablet-shaped crystals is usually preferred overmore common needle-shaped crystals, particularly when molecular diffusion isimportant All crystals incorporate both intrinsic and extrinsic defects, but whereasthe presence of the latter may be easily controlled through purity of synthesisconditions, control of the former requires a deep knowledge of the underlying crystalgrowth mechanism By defect we mean a well-defined aperiodic interruption in theperiodic crystal structure First, it is important to understand the nature of the defect,which normally requires a form of microscopy Transmission electron microscopy(TEM) is the principal method used for this, but scanning probe microscopy
is also useful Owing to the structural complexity of framework crystals, eachcrystal system tends to display a unique defect structure that must be individuallycharacterized An extension of the same phenomenon is the incorporation ofintergrowth and twin structures Such defects are introduced during the crystalgrowth stage usually as a result of competing crystallization pathways that are near
Zeolites and Catalysis, Synthesis, Reactions and Applications Vol 1.
Edited by Jiˇr´ı ˇ Cejka, Avelino Corma, and Stacey Zones
Copyright 2010 WILEY-VCH Verlag GmbH & Co KGaA, Weinheim
Trang 32energy equivalent By understanding the growth mechanism it should be possible
to identify the crucial step that controls this fork in the crystal growth, determinethe energetic considerations, and predict modifications to growth conditions so as
to enhance the probability of forming one particular crystal over another This iscrucial, for instance, for the preparation of chiral crystals that are assembled from
a spiral stacking of achiral units [2, 3]
The advent of atomic force microscopy (AFM) (Figure 1.1) has opened up newpossibilities to investigate the molecular events that occur during crystal growth
and dissolution/recrystallization The technique can be used both in situ and ex situ with each method suited to particular problems Ex situ operation allows a vast array
of synthetic parameters to be varied without concern for the delicacies of the AFMoperation In this respect, careful quenching experiments whereby the state of thenanoscopic features at the crystalline surface may be frozen rapidly before transfer
to the AFM can be performed This is crucial to prevent secondary processescaused by changing growth conditions upon crystal cooling and extraction from themother-liquor Rates and energies of crystal growth processes can be determined
via such ex situ experiments through modeling both crystal topology and habit.
In situ AFM gives a more direct approach to determining growth and dissolution
rates Further, surface structures that are inherently less stable may not be seen
in ex situ analysis Consequently, where possible, in situ analysis is preferred The
Figure 1.1 (a) Interlaced spiral on aluminophosphate
STA-7; (b) zeolite A reducing supersaturation; (c) metal
or-ganic framework ZIF-8; (d) in situ ZnPO4-FAU growth
(f, g) in situ dissolution of zeolite L.
Trang 331.2 Theory of Nucleation and Growth 3
structural details leading to the observed crystal growth, defect, and intergrowthstructure can also be probed using electron microscopy, and by slicing crystalsopen we can look at the consequences of structural growth decisions in the heart ofthe crystals To probe the solution chemistry from which the crystals have evolved,
a combination of the speciation delineation of nuclear magnetic resonance (NMR)with the speed and sensitivity of mass spectrometry is increasing our knowledgesubstantially Both these techniques also probe the extent of oligomerization in thebuildup to nucleation that can be further probed using cryo-TEM methods
1.2
Theory of Nucleation and Growth
1.2.1
Nucleation
The formation of a new crystalline entity from a solution starts through the
nucleation process Nucleation is defined as the series of atomic or molecular
processes by which the atoms or molecules of a reactant phase rearrange into acluster of the product phase large enough as to have the ability to grow irreversibly
to a macroscopically larger size The cluster is defined as nucleus [4] or critical
nuclei
Nucleation can be homogeneous, in the absence of foreign particles or crystals inthe solution, or heterogeneous, in the presence of foreign particles in the solution
Both types of nucleation are collectively known as primary nucleation Secondary
nucleation takes place when nucleation is induced by the presence of crystals ofthe same substance
1.2.2
Supersaturation
The driving force needed for the nucleation and growth of a crystal is referred to
as supersaturation and is defined as the difference in chemical potential between a
molecule in solution and that in the bulk of the crystal phase:
whereµsis the chemical potential of a molecule in solution andµcis the chemicalpotential of the molecule in the bulk crystal Following thermodynamics Eq (1.1)can be expressed as
where k is the Boltzmann constant, T is the absolute temperature, and S is the
supersaturation ratio When µ > 0 the solution is said to be supersaturated,
meaning that nucleation and/or growth is possible, whereas when µ < 0 the
solution will be undersaturated and dissolution will take place The form of
Trang 34the supersaturation ratio will change depending on the system considered (i.e.,gas/solid, solution/solid, melt/solid) For nucleation and growth from solutions ittakes the following form:
S=a ni i
a ni
i,e
(1.3)
where n i is the number of ith ions in the molecule of the crystal, and a i and a i,ethe
actual and equilibrium activities of the i molecule in the crystal.
1.2.3
Energetics
According to nucleation theory, the work necessary to form a cluster of n number
of molecules is the difference between the free energy of the system in its finaland initial states [4, 5] plus a term related to the formation of an interface betweennucleus and solution This can be expressed by (assuming a spherical nucleus):
where r is the radius of the nucleus and σ is the surface free energy If each molecule
in the crystal occupies a volume V, then each nucleus will contain (4 /3)π · r3/V
molecules Eq (1.4) will then take the following form:
Figure 1.2 (a) Total free energy versus cluster size.
(b) Nucleation rate as a function of supersaturation
(show-ing the critical supersaturation).
Trang 351.2 Theory of Nucleation and Growth 5
Figure 1.2a shows a plot of G T as a function of r; it can be seen how the
function reaches a maximum, which represents the energetic barrier that needs to
be surpassed to achieve nucleation (G∗) The value of r at this maximum (r∗) is
defined as the critical radius or nucleus size [4, 5] Its value is defined by
r = 2σ · V
It has been proved that the value of r∗decreases (as well as that ofG∗) as the
supersaturation increases [6], meaning that the probability of having nucleation in
a given system will be higher, the higher the supersaturation
1.2.5
Heterogeneous and Secondary Nucleation
Equations (1.5) and (1.6) shows that bothG∗and r∗depend heavily on the surface
free energy (σ ), so any process that modifies this value will have an effect on the
possible viability of the nucleation process It has been proved that in the presence of
a foreign substrate the decrease in the value ofσ therefore reduces the values of G∗
and r∗at constant supersaturation [6], that is, making nucleation more favorable
A decrease inσ will also decrease the value of the critical supersaturation (µc),since the nucleation rate is also dependent on the surface energy (Eq (1.7)) Thiswill make heterogeneous nucleation more viable than homogeneous nucleation atlow supersaturation conditions The reduction of the surface energy will be thehighest when the best match between the substrate and the crystallizing substance
is achieved This situation is created, of course, when both the substrate and
the crystallizing substance are the same, referred to as secondary nucleation This
mechanism will be more favorable than both heterogeneous and homogeneousnucleation and thus produced at lower supersaturation
Trang 36Induction Time
Induction time is defined as the amount of time elapsed between the achievement
of a supersaturated solution and the observation of crystals Its value will thus
depend on the setting of t= 0 and the technique used to detect the formation ofcrystals The induction period can be influenced by factors such as supersaturation,agitation, presence of impurities, viscosity, and so on Mullin [5] defined theinduction time as
1) transport of atoms through solution;
2) attachment of atoms to the surface;
3) movement of atoms on the surface;
4) attachment of atoms to edges and kinks
The first process is the so-called transport process, whereas 2–4 are referred
to as surface processes (and may involve several substeps) Since these different
steps normally occur in series, the slowest process will control the overall crystalgrowth Therefore, growth can be transport (when step 1 is the slowest) or surfacecontrolled (when steps 2–4 are the slowest)
1.2.8
Crystal Surface Structure
Crystal growth theories are based on considerations of the crystal surface structure.One of the most commonly used models was that provided by Kossel [9] This modelenvisions the crystal surface as made of cubic units (Figure 1.4) which form layers
of monoatomic height, limited by steps (or edges) These steps contain a number
of kinks along their length The area between steps is referred to as a terrace, and
it may contain single adsorbed growth units, clusters, or vacancies According tothis model, growth units attached to the surface will form one bond, whereas thoseattached to the steps and kinks will form two and three bonds, respectively Hence,kink sites will offer the most stable configuration Growth will then proceed by
Trang 371.2 Theory of Nucleation and Growth 7
(4)
(6) (5)
(7)
(3)
(2) (4)*
(3) (2) (1)
(b)
Figure 1.3 (a) Schematic representation
of processes involved in the crystal growth:
(1) Transport of solute to a position near
the crystal surface; (2) diffusion through
boundary layer; (3) adsorption onto
crys-tal surface; (4) diffusion over the surface;
(4*) desorption from the surface; (5) ment to a step or edge; (6) diffusion along the step or edge; (7) Incorporation into kink site or step vacancy (b) Associated energy changes for the processes depicted in (a).
attach-Figure modified from Elwell et al [7].
the attachment of growth units to kink sites in steps The kink will move alongthe step producing a net advancement of the step until this step reaches the faceedge Then, a new step will be formed by the nucleation of an island of monolayerheight (or two-dimensional (2D) nucleus) on the crystal surface This mechanism
of growth is normally referred to as layer growth or single nucleation growth and
is represented in Figure 1.5 A variation of this growth mechanism occurs whenthe nucleation rate is faster than the time required for the step to cover the wholecrystal surface In this case, 2D nuclei will form all over the surface and on top
Growth unit
Figure 1.4 Kossel model of a crystal surface.
Trang 38(b)
(c)
Figure 1.5 Schematic representation of layer growth (a)
Incorporation of growth units into step (b) The step has
almost advanced to the edge of the crystal (c) Formation of
2D nucleus.
of other nuclei These nuclei will spread and coalesce forming layers This growth
mechanism is normally referred to as multinucleation multilayer growth or birth and spread [10].
Trang 391.2 Theory of Nucleation and Growth 9
It can be seen that the value of r 2D∗is half of the nucleus size for homogeneous
In the initial stage the dislocation creates a step (Figure 1.6a) Growth units attach
to the step making it advance and thus generating a second step (Figure 1.6b)
This second step will not advance until its length equals 2r 2D∗; this is because any
growth of a step with a smaller size is not thermodynamically favored Once thesecond step starts advancing, it will generate a third step which in turn will not start
moving until its length equals 2r 2D∗(Figure 1.6c), then a fourth step will appear,
and so on (Figure 1.6d) This will generate a spiral pattern around the dislocationcore, and a self-perpetuating source of steps where growth requires less energythan a layer mechanism (therefore, it can proceed at smaller supersaturation) Inthe case of a curved step, the spiral will be rounded and its curvature will be
determined by the r 2D∗value at the specific supersaturation conditions in which
Trang 40the crystal grows The theory of crystal growth by spiral dislocation was further
refined by Burton, Cabrera, and Frank [13], giving rise to what is known as the BCF theory.
a schematic diagram showing the formation of a spiral of this type according tovan Enckevort [14] The surface in the figure is produced by two distinct types of
steps (I and II), of height 1/2 dhkl, emanating from a central point O Layers oftype I are bound by steps a and b, whereas layers from type II are bound by steps
c and d Steps a and d move fast and steps b and c move slowly This results insteps a of layer I catching up with steps c from layer II, producing a double step ofunit-cell height The same process is observed in steps d joining the slow steps b.The result is a pattern of unit-cell height steps with interlaced crossovers formed by
lower steps of height 1/2 dhkl Interlaced spirals have been observed in numeroussystems, including barite [15], molecular crystals [16, 17], silicon carbide [18], GaN[19], and sheet silicates [20]
1.2.12
Growth Mechanisms: Rough and Smooth Surfaces
The growth mechanisms can be classified into three types depending on theinterface structure If the surface is rough the growth mechanism will be ofadhesive type, whereas if the surface is smooth growth will take place by either
d
d Type I
a
a c
c c c
c
a a
Figure 1.7 Interlaced spiral formation Figure modified from van Enckevort et al [14].