Design and applications of single-site heterogeneous catalysts : contributions to green chemistry, clean technology and sustainability

For far too long chemists and industrialists have relied on the use of aggressive reagents such as nitric and sulphuric acids, permanganates and dichromates to prepare the massive quantities of both bulk and fine chemicals that are needed for the maintenance of civilised life -- materials such as fuels, fabrics, foodstuffs, fertilisers and pharmaceuticals. Such aggressive reagents generate vast quantities of environmentally harmful and often toxic by-products, including the oxides of nitrogen, of metal oxides and carbon dioxide.Now, owing to recent advances made in the synthesis of nanoporous solids, it is feasible to design new solid catalysts that enable benign, mild oxidants to be used, frequently without utilising solvents, to manufacture the products that the chemical, pharmaceutical, agro- and bio-chemical industries require. These new solid agents are designated single-site heterogeneous catalysts (SSHCs). Their principal characteristics are that all the active sites present in the high-area solids are identical in their atomic environment and hence in their energy of interaction with reactants, just as in enzymes.Single-site heterogeneous catalysts now occupy a position of growing importance both academically and in their potential for commercial exploitation. This text, the only one devoted to such catalysts, dwells both on principles of design and on applications, such as the benign synthesis of nylon 6 and vitamin B3. It equips the reader with unifying insights required for future catalytic adventures in the quest for sustainability in the materials used by humankind.Anyone acquainted with the language of molecules, including undergraduates in the physical and biological sciences, as well as graduates in engineering and materials science, should be able to assimilate the principles and examples presented in this book. Inter alia, it describes how clean technology and 'green' processes may be carried out in an environmentally responsible manner.

Gerhard Ertl

Foreword	p. vii
Preface	p. ix
Acknowledgements	p. xiii
Permissions	p. xxiii
Part I Basics and Background	p. 1
Chapter 1 Introduction to the Salient Features of Single-site Heterogeneous Catalysts	p. 3
Chapter 2 Lessons from the Biological World: The Kinship Between Enzymes and Single-site Heterogeneous Catalysts	p. 11
2.1 The Story of Lysozyme and Its Consequences	p. 11
2.2 Hybrid Enzymes	p. 15
2.3 Immobilized Enzymes	p. 16
2.4 The Kinship between Enzymes and SSHCs	p. 16
Chapter 3 Distinctions between Single-site Heterogeneous Catalysts and Immobilized Homogeneous Catalysts	p. 23
3.1 Outline of Historical Background	p. 23
3.2 Metal Cluster Compounds as Molecular Precursors for Tailored Metal Nanocatalysts	p. 27
3.3 The Essence of Surface Organometallic Chemistry (SOMC)	p. 30
3.4 Highly Active Organometallic Catalysts Based on Self-assembled Monolayers	p. 36
3.5 Colloid-bound Organometallic Catalysts of Exceptional Activity	p. 37
3.6 Analogies with Single-site Homogeneous Polymerization Catalysts	p. 38
3.7 The Taxonomy of SSHCs: A Résumé	p. 40
Part II Microporous Open Structures	p. 51
Chapter 4 Microporous Open Structures for the Design of New Single-site Heterogeneous Catalysts	p. 53
4.1 Introduction	p. 53
4.2 The Salient Characteristics of Microporous SSHCs	p. 59
4.3 Some Examples of Acidic Microporous SSHCs	p. 64
4.3.1 Environmentally benign, solvent-free alkylations, acylations and nitrations using acidic SSHCs	p. 67
4.3.2 Brønsted acidic microporous SSHCs for hydroisomerization (dewaxing) of alkanes: designing new catalysts in silico	p. 69
4.4 Brønsted Acidic Microporous SSHCs for the Dehydration of Alkanols: Environmentally Benign Routes to Ethylene, Propylene and Other Light Alkenes	p. 74
4.4.1 Catalytic dehydration of ethanol using Brønsted acidic SSHCs	p. 75
4.4.2 The methanol-to-olefin conversion over Brønsted acidic SSHCs	p. 75
4.4.3 Structural and mechanistic aspects of the dehydration of isomeric butanols over porous aluminosilicate acid catalysts	p. 80
4.5 Lewis Acidic Microporous SSHCs for a Range of Selective Oxidations	p. 87
4.6 Cascade Reactions with TAPO-5	p. 88
4.6.1 One-pot reactions: a contribution to environmental protection using Lewis acid active sites	p. 90
4.7 Redox Active Sites in Microporous Solids	p. 92
4.7.1 Introduction	p. 92
4.7.2 Single-site redox active centres for the benign selective oxidation of hydrocarbons in air or 02	p. 93
4.8 Insights from Quantum Chemical Computations into the Mechanism of C-H Activation at Mn III Catalytic Centres in Microporous Solids	p. 102
4.9 Bifunctional Single-site Microporous Catalysts: A Solvent-free Synthesis of Caprolactam, the Precursor of Nylon 6	p. 107
4.10 Single-site Metal Cluster Catalysts Supported on a Microporous Host: Reactive Environments Influence the Structure of Catalysts	p. 109
Chapter 5 Single-site Heterogeneous Catalysts for the Production of Pharmaceuticals, Agrochemicals, Fine and Bulk Chemicals	p. 121
5.1 Introduction	p. 121
5.2 Fine Chemicals and Pharmaceuticals	p. 122
5.2.1 Facile, one-step production of niacin (vitamin B 3 ) and other nitrogen-containing chemicals with SSHCs	p. 122
5.2.2 Facile, one-step production of isonicotinic acid from 4-picoline	p. 125
5.2.3 Production of pharmaceutically important derivatives of quinoline	p. 127
5.3 Environmentally Benign Oxidative Methods of Producing Bulk Chemicals Using SSHCs	p. 128
5.3.1 The synthesis of benzaldehyde from toluene	p. 129
5.3.2 The one-step conversion of cyclohexane to adipic acid	p. 132
5.3.3 The one-step aerobic, solvent-free conversion of p-xylene to terephthalic acid	p. 134
5.4 Environmentally Benign, Brønsted Acid-catalysed Production of Bulk Chemicals with Microporous SSHCs	p. 136
5.5 Transformations Involving Lewis Acid Microporous Catalysts	p. 137
5.5.1 Conversions of sugars to lactic acid derivatives using Sn-based zeotypic SSHCs	p. 137
5.5.2 Single-site, Lewis acid microporous catalysts for the isomerization of glucose: a new efficient route to the production of high-fructose corn syrup	p. 140
5.6 Baeyer-Villiger Oxidations of Ketones to Lactones with SSHCs	p. 141
5.6.1 Introduction	p. 141
5.6.2 A redox SSHC for Baeyer-Villiger aerobic oxidations under Mukaiyama conditions	p. 142
5.6.3 Sn-centred single-site microporous catalysts for Baeyer-Villiger oxidations with H 2 O 2	p. 144
5.7 The Crucial Role of Single-site Microporous Catalysts in New Methods of Synthesizing ¿-Caprolactam and Nylon 6	p. 145
5.7.1 Introduction	p. 145
5.7.2 The primacy of nylon 6	p. 145
5.7.3 Existing routes to the synthesis of ¿-caprolactam	p. 147
5.7.4 The design of a green, one-step production of ¿-caprolactam using a bifunctional SSHC	p. 149
5.7.5 Optimizing SSHCs for oxime production	p. 151
5.8 Envoi	p. 152
Part III Mesoporous Open Structures	p. 157
Chapter 6 Epoxidations and Sustainable Utilization of Renewable Feedstocks, Production of Vitamin E Intermediates, Conversion of Ethene to Propene and Solvent-free, One-step Synthesis of Esters	p. 159
6.1 Introduction	p. 159
6.2 A Comprehensive Picture of the Nature and Mechanism of the Ti IV -catalysed Epoxidation of Alkenes	p. 162
6.2.1 Mechanism of the Ti IV -centred epoxidation of alkenes	p. 165
6.2.2 An alternative method of introducing isolated Ti centres to mesoporous silica	p. 169
6.2.3 The use of H 2 O 2 over Ti IV -grafted mesoporous silica catalysts: a further step towards sustainable epoxidation	p. 171
6.2.4 Ti IV mesoporous catalysts have an important role to play in a sustainable way to utilize renewable feedstocks from fats and vegetable sources	p. 173
6.3 Other Examples of Single-site, Metal-centred Catalysts Grafted onto Mesoporous Silica	p. 175
6.4 Titanium Cluster Sites for the Production of Vitamin E (Benzoquinone) Intermediates	p. 176
6.5 Single-site Metal Complexes Grafted onto Mesoporous Silica	p. 179
6.5.1 Stability and recyclability of supported metal-ligand complex catalysts: a critical note	p. 181
6.6 A Trifunctional, Mesoporous Silica-based Catalyst: Highly Selective Conversion of Ethene to Propene	p. 182
6.7 Hybrid SSHCs are Chemically Robust	p. 183
6.8 The Confluence of Heterogeneous and Homogeneous Catalysis Involving Single Sites	p. 184
6.9 Beyond Mesoporous Silica	p. 188
6.9.1 The merits of clay-based single-site catalysts	p. 188
6.9.2 Pillared zeolites?	p. 191
6.10 Envoi	p. 192
Chapter 7 Exploiting Nanospace for Asymmetric Conversions	p. 201
7.1 Background	p. 201
7.2 Whither Chiral Zeolites?	p. 202
7.3 Chiral Metal-organic Frameworks (MOFs)	p. 206
7.4 Harnessing the Asymmetric Catalytic Potential of Mesoporous Silicas Using SSHCs	p. 210
7.4.1 Background	p. 210
7.4.2 Exploiting nanospace for asymmetric catalysis: confinement of immobilized single-site chiral catalysts enhances enantioselectivity	p. 212
7.4.3 Asymmetric hydrogenation of E-¿-phenylcinnamic acid and methyl benzoylformate: the advantages of using inexpensive diamine asymmetric ligands	p. 219
7.4.4 One step is better than two	p. 221
7.5 Epilogue	p. 225
Chapter 8 Multinuclear, Bimetallic Nanocluster Catalysts	p. 233
8.1 Definitions: Nanoclusters are Distinct from Nanoparticles	p. 233
8.1.1 Bimetallic nanoclusters and bimetallic nanoparticles are not alloys	p. 235
8.2 The Merits of Studying Bimetallic Nanocluster Catalysts	p. 236
8.3 Why Focus on Bimetallic Catalysts Based on Platinum Group Metals (PGMs)?	p. 241
8.4 Specific Examples of High-performance Bimetallic Nanocluster Catalysts for Selective Hydrogenations under Benign Conditions	p. 244
8.4.1 Bimetallic nanocluster catalysts for ammoxidation	p. 246
8.4.2 Bimetallic nanocluster catalysts for the (sustainable) synthesis of adipic acid	p. 247
8.5 Bimetallic and Trimetallic Nanocluster Catalysts Containing Tin: The Experimental Facts	p. 249
8.6 Quantum Computational Insights	p. 249
8.6.1 The computational method	p. 253
8.6.2 Assessing the structure and electronic properties of Ru 5 PtSn in the gas phase and when supported on silica (cristobalite)	p. 253
8.6.3 Quantum insights into the structure and densities of states of Ru n Sn n (n = 3 to 6) clusters in the gas phase	p. 258
8.7 Comparisons with Nanocluster Catalysts Involving Gold, Platinum, Palladium and Iridium	p. 260
8.7.1 Nanocluster catalysts of palladium and iridium	p. 265
8.7.2 The role of the catalyst support	p. 267
8.8 Envoi	p. 268
Appendix I Reference Works Dealing With Green Chemistry, Clean Technology and Sustainability	p. 277
Index	p. 281

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