Jackson S.D., Hargreaves J.S.J. Metal Oxide Catalysis
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List of Contributors XXI
Zili Wu
Oak Ridge National Laboratory
Chemical Science Division
Center for Nanophase Materials
Sciences
Oak Ridge, TN 37831 - 6493
USA
Wuzong Zhou
University of St. Andrews
School of Chemistry
Purdie Building, North Haugh
St. Andrews, Fife KY16 9ST
United Kingdom
Contents to Volume 2
Contents to Volume 1 XI
11 Oxidation Reactions over Supported Metal Oxide Catalysts:
Molecular/Electronic Structure – Activity/Selectivity Relationships 487
Israel E. Wachs and Taejin Kim
11.1 Overview 487
11.2 Introduction 487
11.3 Monolayer Surface Coverage 488
11.4 Molecular and Electronic Structures 490
11.5 Number of Exposed Catalytic Active Sites (N
s
) 491
11.6 Surface Reactivity 492
11.7 Steady-State Reactivity (TOF) 493
11.8 Number of Participating Catalytic Active Sites in Oxidation
Reactions 494
11.9 Role of Surface Acid Sites on Oxidation Reactions 495
11.10 Other Supported MO
x
Redox Active and Acidic Systems 496
11.11 Conclusions 496
References 497
12 Vanadium Phosphate Catalysts 499
Johnathan K. Bartley, Nicholas F. Dummer, and Graham J. Hutchings
12.1 Introduction 499
12.2 The Active Catalyst 500
12.2.1 The Oxidation State of the Catalyst 502
12.2.2 The Phosphorus-to-Vanadium Ratio of the Catalyst 504
12.2.3 The Role of Amorphous Material 505
12.2.4 The Disordered Plane 507
12.2.5 Acid–Base Properties 507
12.3 Preparation of VPP Precursors 508
12.3.1 The Preparation of Novel Vanadium Phosphates 513
12.4 Activation of the Catalyst Precursors 514
12.4.1 Activation Procedures 514
12.4.2 Structural Transformations during Activation 517
V
Metal Oxide Catalysis. Edited by S. David Jackson and Justin S. J. Hargreaves
Copyright © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
ISBN: 978-3-527-31815-5
VI Contents to Volume 2
12.5 Promoted Catalysts 519
12.6 Mechanism of n-Butane Partial Oxidation 524
12.6.1 Consecutive Alkenyl Mechanism 524
12.6.2 Consecutive Alkoxide Mechanism 527
12.6.3 Concerted Mechanism 529
12.6.4 Redox Couple Mechanism 530
12.7 Concluding Comments 530
References 531
13 Heterogeneous Catalysis by Uranium Oxides 539
Stuart H. Taylor
13.1 Introduction 539
13.2 Structure of Uranium Oxides 540
13.3 Historical Uses of Uranium Oxides as Catalysts 543
13.4 Catalysis by Uranium Oxides 547
13.4.1 Total Oxidation 547
13.4.2 Selective Oxidation 528
13.4.3 Reduction 554
13.4.4 Steam Reforming 556
13.5 Conclusions 558
References 559
14 Heteropolyoxometallate Catalysts for Partial Oxidation 561
Jacques C. Védrine and Jean-Marc M. Millet
14.1 Introduction 561
14.2 History of Polyoxometallates 565
14.3 Properties and Applications of Polyoxometallates 566
14.4 Catalytic Applications in Partial Oxidation
Reactions 568
14.4.1 Oxidation with Molecular Oxygen 570
14.4.2 Oxidation by Hydrogen Peroxide 575
14.5 Characterization: Redox and Acid–Base Properties 578
14.5.1 IR Spectroscopy 581
14.5.2 Photoacoustic Spectroscopy 582
14.5.3 UV-Visible Spectroscopy 583
14.5.4 Nuclear Magnetic Resonance Spectroscopy 583
14.5.5 Electron Spin Resonance (ESR) Spectroscopy 584
14.5.6 Electrochemistry of Keggin Heteropoly Compounds 585
14.5.7 Thermal Analysis 586
14.5.8 Microcalorimetry of Acid or Basic Probe
Adsorption 586
14.6 Conclusions and Perspectives in Polyoxometallate Application
in Heterogeneous Oxidation Catalysis 587
References 589
Contents to Volume 2 VII
15 Alkane Dehydrogenation over Vanadium and Chromium Oxides 595
S. David Jackson, Peter C. Stair, Lynn F. Gladden, and James McGregor
15.1 Introduction 595
15.2 Commercial LPG Dehydrogenation Process 596
15.3 Lummus/Houdry CATOFIN
®
Process 596
15.4 Chromia 596
15.5 Vanadia 601
15.6 Conclusions 610
References 610
16 Properties, Synthesis and Applications of Highly Dispersed Metal
Oxide Catalysts 613
Juncheng Hu, Lifang Chen, and Ryan Richards
16.1 Introduction 613
16.2 Properties 614
16.2.1 Structure and Bonding 614
16.2.2 Defects 616
16.2.3 Acid–Base Properties of Metal Oxides 617
16.2.4 Redox Property of Metal Oxides 619
16.3 Synthesis 619
16.3.1 Sol–Gel Technique 620
16.3.1.1 Hydrolysis and Condensation of Metal Alkoxides 622
16.3.1.2 Solvent Removal and Drying 623
16.3.2 Co-precipitation Methods 627
16.3.2.1 Co-precipitation from Aqueous Solution at Low
Temperature 628
16.3.2.2 Sonochemical Co-precipitation 630
16.3.2.3 Microwave-Assisted Co-precipitation 631
16.3.3 Solvothermal Technique 633
16.3.4 Micro-Emulsion Technique 636
16.3.5 Combustion Methods 638
16.3.6 Others 639
16.3.6.1 Vapor Condensation Methods 639
16.3.6.2 Spray Pyrolysis 640
16.3.6.3 Templated/Surface Derivatized Nanoparticles 640
16.4 Applications in Catalysis 641
16.4.1 Oxygenation of Alkanes 641
16.4.2 Biodiesel Production 643
16.4.3 Methanol Adsorption and Decomposition 645
16.4.4 Destructive Adsorption of Chlorocarbons 649
16.4.5 Alkene Metathesis 650
16.4.6 Claisen–Schmidt Condensation 652
16.5 Conclusions 653
References 654
VIII Contents to Volume 2
17 Preparation of Superacidic Metal Oxides and Their Catalytic Action 665
Kazushi Arata
17.1 Introduction 665
17.2 Preparation 669
17.2.1 Sulfated Metal Oxides of Zr, Sn, Ti, Fe, Hf, Si, and Al 669
17.2.1.1 Preparation of Zirconia Gel 669
17.2.1.2 Preparation of Stannia Gel 669
17.2.1.3 Preparation of H
4
TiO
4
670
17.2.1.4 Preparation of Fe(OH)
3
670
17.2.1.5 Preparation of Hf(OH)
4
670
17.2.1.6 Sulfation, Calcination, and Catalytic Action 670
17.2.1.7 Preparation of Sulfated Silica 671
17.2.1.8 Preparation of Sulfated Alumina 671
17.2.1.9 Property and Characterization 671
17.2.1.10 One-Step Method for Preparation of SO
4
/ZrO
2
672
17.2.1.11 Commercial Gels for Preparation of SO
4
/ZrO
2
and SO
4
/SnO
2
672
17.2.1.12 Effect of Drying and Calcination Temperatures on the Catalytic
Activity of SO
4
/ZrO
2
673
17.2.2 Tungstated, Molybdated, and Borated Metal Oxides 674
17.2.2.1 Preparation of WO
3
/ZrO
2
and MoO
3
/ZrO
2
674
17.2.2.2 Preparation of WO
3
/SnO
2
, WO
3
/TiO
2
, and WO
3
/Fe
2
O
3
674
17.2.2.3 Preparation of B
2
O
3
/ZrO
2
674
17.2.2.4 Property and Characterization 675
17.3 Determination of Acid Strength 675
17.3.1 Hammett Indicators 676
17.3.2 Test Reactions 677
17.3.3 Temperature-Programmed Desorption (TPD) 677
17.3.4 Temperature-Programmed Reaction (TPRa) 678
17.3.5 Ar-TPD 678
17.3.6 Ar-Adsorption 680
17.4 Nature of Acid Sites 682
17.5 Isomerization of Butane Catalyzed by Sulfated Zirconia 685
17.6 Isomerization of Cycloalkanes 686
17.7 Structure of Sulfated Zirconia 687
17.8 Promoting Effect 689
17.8.1 Effect of Addition of Metals to Sulfated Zirconia on the Catalytic
Activity 689
17.8.2 Effect of Mechanical Mixing of Pt-Added Zirconia on the Catalytic
Activity 690
17.9 Friedel–Crafts Acylation of Aromatics 692
17.10 Ceramic Acid 695
17.10.1 Tungstated Stannia 696
17.10.2 Tungstated Alumina 697
17.11 Application to Sensors and Photocatalysis 698
References 698
Contents to Volume 2 IX
18 Titanium Silicalite-1 705
Mario G. Clerici
18.1 Synthesis and Characterization 706
18.2 Hydroxylation of Alkanes 707
18.2.1 Titanium Silicalite-1 708
18.2.2 Other Ti-Zeolites 712
18.3 Hydroxylation of Aromatic Compounds 712
18.3.1 Hydroxylation of Phenol 713
18.3.1.1 Titanium Silicalite-1 713
18.3.1.2 Other Ti-Zeolites 715
18.3.2 Hydroxylation of Benzene 716
18.3.3 Oxidation of Substituted Benzenes 717
18.4 Oxidation of Olefi nic Compounds 717
18.4.1 Epoxidation of Simple Olefi ns 717
18.4.1.1 Titanium Silicalite-1 718
18.4.1.2 Other Ti-Zeolites 722
18.4.2 Epoxidation of Unsaturated Alcohols 724
18.4.3 Epoxidation of Allyl Chloride and other Substituted Olefi ns 726
18.4.4 Epoxidation with Solvolysis/Rearrangement of Intermediate
Epoxide 726
18.5 Oxidation of Alcohol and Other Oxygenated Compounds 727
18.6 Ammoximation of Carbonyl Compounds 730
18.7 Oxidation of N-Compounds 732
18.8 Oxidation of S-Compounds 734
18.9 Industrial Processes Catalyzed by TS-1 734
18.9.1 Hydroxylation of Phenol to Catechol and Hydroquinone 734
18.9.2 Salt-Free Production of Cyclohexanone Oxime 734
18.9.3 Propene Oxide Synthesis (HPPO) 735
18.10 Problems in the Use of H
2
O
2
and Possible Solutions 736
18.10.1 Direct Synthesis of Hydrogen Peroxide 737
18.10.2 In Situ Production of Hydrogen Peroxide 737
18.10.3 Process Integration 738
18.10.4 Miscellanea 739
18.11 Adsorption, Active Species and Oxidation Mechanisms 740
18.11.1 Adsorption and Catalytic Performances 740
18.11.2 The Structure of Ti
–
OOH Species 742
18.11.3 Reactive Intermediates and Oxidation Mechanisms 743
18.11.4 Proposal for a General Mechanistic Scheme 746
18.12 Conclusions 748
References 749
19 Oxide Materials in Photocatalytic Processes 755
Richard P.K. Wells
19.1 Introduction 755
19.2 Basic Principles of Heterogeneous Photocatalysis 756
X Contents to Volume 2
19.3 Traditional Photocatalysts 757
19.4 Improving Photocatalytic Activity 760
19.4.1 Visible Light Sensitization by Adsorption of Organic and Inorganic
Dyes 760
19.4.2 Visible Light Sensitization by Anion Doping 760
19.4.3 Visible Light Sensitization by Metal Ion Implantation Techniques 761
19.4.4 Physical Methods to Enhance Photocatalytic Activity 763
19.4.5 Potential-Assisted Photocatalysis 766
19.5 Conclusions 766
References 767
20 Catalytic Ammoxidation of Hydrocarbons on Mixed Oxides 771
Fabrizio Cavani, Gabriele Centi, and Philippe Marion
20.1 Introduction 771
20.2 Propene Ammoxidation to Acrylonitrile 775
20.3 Propane Ammoxidation to Acrylonitrile 778
20.3.1 Mo/V/Te/Sb/(Nb)/O Catalysts 782
20.3.2 Rutile-Type Antimonate Catalysts 786
20.4 Alkylaromatic Ammoxidation 791
20.4.1 Alkylbenzenes and Substituted Alkylbenzenes 791
20.4.2 Alkylaromatics Containing Hetero-Groups 795
20.4.3 Ammonolysis vs Ammoxidation 796
20.5 Ammoxidation of Unconventional Molecules 797
20.5.1 The Ammoxidation of C
4
Hydrocarbons 797
20.5.2 The Ammoxidation of Cyclohexanol and Cyclohexanone 800
20.5.3 The Ammoxidation of Cyclohexane and n-Hexane 802
20.5.4 The Ammoxidation of Benzene 805
20.5.5 Ammoxidation of C
2
Hydrocarbons 807
20.5.6 Conclusions on the Ammoxidation of Unconventional Molecules 808
20.6 Use of Other Oxidants for Ammoxidation Reactions 810
20.7 Conclusions 810
References 811
21 Base Catalysis with Metal Oxides 819
Khalaf AlGhamdi, Justin S. J. Hargreaves, and S. David Jackson
21.1 Introduction 819
21.2 Catalysts and Catalytic Processes 825
21.2.1 Alkali Metal Oxides 826
21.2.2 Alkaline Earth Metal Oxides 830
21.2.3 Hydrotalcites 835
21.2.4 Rare Earth Oxides 836
21.2.5 Basic Zeolites 837
21.2.6 Zirconia Superbases 837
21.3 Outlook 838
References 840
Index 845
Contents to Volume 1
1 EPR (Electron Paramagnetic Resonance) Spectroscopy of Polycrystalline
Oxide Systems 1
Damien M. Murphy
2 The Application of UV-Visible-NIR Spectroscopy to Oxides 51
Gianmario Martra, Enrica Gianotti, and Salvatore Coluccia
3 The Use of Infrared Spectroscopic Methods in the Field of Heterogeneous
Catalysis by Metal Oxides 95
Guido Busca
4 Resonance Raman Spectroscopy – Θ-Al
2
O
3
-Supported Vanadium Oxide
Catalysts as an Illustrative Example 177
Zili Wu, Hack-Sung Kim, and Peter C. Stair
5 Solid-State NMR of Oxidation Catalysts 195
James McGregor
6 Photoelectron Spectroscopy of Catalytic Oxide Materials 243
Detre Teschner, Elaine M. Vass, and Robert Schlögl
7 X-ray Absorption Spectroscopy of Oxides and Oxidation Catalysts 299
Michael Stockenhuber
8 Theory: Periodic Electronic Structure Calculations 323
Rudy Coquet, Kara L. Howard, and David J. Willock
9 Thermal Analysis and Calorimetric Methods 391
Simona Bennici and Aline Auroux
10 Transmission Electron Microscopy 443
Wuzong Zhou
Metal Oxide Catalysis. Edited by S. David Jackson and Justin S. J. Hargreaves
Copyright © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
ISBN: 978-3-527-31815-5
XI
EPR (Electron Paramagnetic Resonance) Spectroscopy
of Polycrystalline Oxide Systems
Damien M. Murphy
1
1
1.1
Introduction
Electron Paramagnetic Resonance ( EPR ), sometimes referred to as Electron Spin
Resonance ( ESR ), is a widely used spectroscopic technique to study paramagnetic
centers on various oxide surfaces, which are frequently encountered in heteroge-
neous catalysis. Diamagnetic oxide materials can also be studied using suitable
paramagnetic probes, including nitroxides and transition metal ions. These observ-
able paramagnetic centers may include surface defects, inorganic or organic radi-
cals, metal cations or supported metal complexes and clusters. Each of these
paramagnetic species will produce a characteristic EPR signature with well defi ned
spin Hamiltonian parameters. However, the magnetic properties, stability and
reactivity of these centers may vary dramatically depending on the nature of the
support or the measurement conditions. In some case, radicals stable on one
surface may be transient on another, while variations in the EPR spectra of these
radicals may be observed simply by altering the pre - treatment conditions of the
support. Furthermore, the spin Hamiltonian parameters for a particular paramag-
netic species may vary greatly from one support to another. A number of “ external ”
perturbations, such as the specifi c location of the species on a surface, the presence
of other interaction species in the catalytic system, the size of the metal particles,
and so on, can alter the spin Hamiltonian parameters, resulting in a signifi cantly
modifi ed EPR profi le. Therefore one must interpret the experimental spectrum
with careful consideration of these variables and where possible record the spectra
under a variety of conditions to reinforce the assignment. Finally, the accurate
analysis of the experimental spectrum can only be achieved by simulation and the
resulting spin Hamiltonian parameters can then be compared to values obtained
by theoretical treatments. All of the steps are crucial in order to derive a complete
description of the electronic structure of the paramagnetic species, and the purpose
of this chapter is to explain and illustrate how these analytical steps are performed
in the interpretation of EPR spectra.
Metal Oxide Catalysis. Edited by S. David Jackson and Justin S. J. Hargreaves
Copyright © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
ISBN: 978-3-527-31815-5
2 1 EPR (Electron Paramagnetic Resonance) Spectroscopy of Polycrystalline Oxide Systems
Most of the literature on surface paramagnetic centers since the mid - 1990s has
originated from studies in heterogeneous catalysis and material science. EPR has
long been recognized as a powerful tool for the catalytic chemist, as the high sen-
sitivity of the technique permits the detection of low concentrations of active sites.
A number of review articles and monographs have appeared over the years specifi -
cally on EPR in catalysis, notably by Lunsford [1] , Howe [2] , Che [3] , Giamello [4] ,
Sojka [5] and Dyrek [6] . The applications of EPR spectroscopy to studies in catalysis
and surface chemistry of metal oxides has also been treated in a number of papers
[7, 8] . Selected examples illustrate the possibilities offered by EPR techniques
towards a deeper understanding of catalyst preparation, the nature of the surface
active sites and the types of reaction intermediate as well as details of catalytic
reaction mechanisms [9, 10] . Hunger and Weitkamp [11] reviewed the subject of
in situ spectroscopic methods, including in situ EPR to directly follow the evolution
of paramagnetic surface intermediates in conditions extremely similar to those
occurring in a real catalytic reactor, and so this area will not be covered here.
A complete description of the physics and fundamental concepts behind the EPR
technique is beyond the scope of this chapter. Numerous textbooks on the subject
of EPR, describing the practicalities of the technique, the fundamental theory and
also the primary applications of the technique to different areas of chemistry,
physics and biology, are widely available [12 – 17] , in addition to the more specialist
textbooks devoted to pulsed methods [18] . It is important to acknowledge that since
1993 there has been extensive development in the areas of pulsed techniques [18]
and high - frequency EPR. High - frequency EPR provides several advantages over
low - frequency techniques. For example, it offers increased resolution of g values,
which is important in systems where spectral lines may not be resolved at lower
fi elds. Additionally, high - frequency EPR has an increased absolute sensitivity
making it particularly useful for studying systems where the number of paramag-
netic species is inherently low. Pulsed EPR has also provided the experimentalist
with additional tools to interrogate the paramagnetic system, particularly in relation
to the advanced hyperfi ne techniques of ENDOR ( Electron Nuclear Double Reso-
nance ), HYSCORE ( Hyperfi ne Sublevel Correlation ), ESEEM ( Electron Spin Echo
Envelope Modulation ) and ELDOR ( Electron Electron Double Resonance ) detected
NMR. In this chapter, only the basic principles of continuous wave ( cw - ) EPR will
be presented, since this method is still the most widely used (primarily owing to
instrumental availability) in studies of heterogeneous catalysis.
1.2
Basic Principles of EPR
1.2.1
The Electron Z eeman Interaction
The electron is a negatively charged particle which possesses orbital angular
momentum as it moves around the nucleus. The electron also possesses spin