Molecular Sieves Principles of Synthesis and Identification

Transcription

1 Molecular Sieves Principles of Synthesis and Identification Second Edition R. SZOSTAK Clark Atlanta University Atlanta, GA USA V D BLACKIE ACADEMIC & PROFESSIONAL An Imprint of Chapman & Hail London Weinheim New York Tokyo Melbourne Madras

2 Contents Preface to the second edition Acknowledgments 1 Molecular sieves: history and nomenclature 1.1 Molecular sieves today 1.2 Zeolithos 1.3 Early commercial zeolites 1.4 Green zeolite technology 1.5 Molecular sieve nomenclature Identifying new zeolite minerals Synthetic zeolites Rules for naming synthetic zeolites 1.6 Zeolites, molecular sieves and microporous materials: a series Zeolite Molecular sieve Microporous materials Clathrasils Interrupted structures Mesoporous materials 1.7 Compositional variability in zeolites and material identity Crystallographic criteria Synthetic criteria Nomenclature and mixed elemental compositions 1.8 Other zeolite definitions 2 Structural aspects 2.1 Molecular sieve structures 2.2 Lowenstein's rule 2.3 Dempsey's rule 2.4 Zeolite and molecular sieve frameworks First level: pore size Determining pore size Second level: dimensionality and shape Visualizing as a hollow tube or a room with Windows Shape of the pore opening Void volume 2.5 Drawing zeolite structures 2.6 Sorting out molecular sieve structures: other approaches Early Classification of zeolites Secondary building unit Three-dimensional nets and polyhedra Sigma transformation 'Pentasü' net

3 Vlll CONTENTS Structural representation via cages or tubes Categories based on synthesis method Summary 3 Faulted and intergrown phases 3.1 Crystal imperfections Rotational stacking faults Twin faults Inclusion faults Domain intergrowths Random phases 3.2 Difficulties in naming faulted or intergrown phases 3.3 Early identification errors 3.4 Characterizing faulted phases 3.5 Dealing with faulted phases in synthesis 3.6 Point defects 4 Fundamentals of synthesis 4.1 Where do we begin? Reproducing nature 4.2 Ostwald's rule and Goldsmith's 'simplexity principle' 4.3 Crystallization flelds 4.4 Crystallization curves 4.5 Practical considerations in zeolite synthesis Chemical purity of reagents Laboratory handling of reagents Crystallizing vessels Cleaning crystallizing vessels Calculation of zeolite batch composition 4.6 Reaction mixture components Gel silica/alumina ratio Hydroxide concentration Monitoring ph in zeolite crystallization Role of inorganic cations Anions other than hydroxide Water for transport and structure direction Influence of temperature and heating rate Seeds and aging Source materials Stirring or static? 4.7 Summary 5 Process of zeolite formation on a molecular level 5.1 From macro to micro Methodology for studying gels Q-units 5.2 Silicate fragments in zeolite synthesis Orthosilicates Pyrosilicates Metasilicates, specifically those containing ring Silicate ions Synthetic polysiloxanes: dimers and cyclic structures 5.3 Silicates in water Solutions 5.4 Amphoteric oxides in water Solutions

4 CONTENTS IX 5.5 Secondary building units and their role in zeolite synthesis Starting very small: probing species in Solution Distribution of silica and alumina; compositional analysis Infrared and Raman spectroscopic techniques applied to Silicates Trapping Silicate fragments through trimethylsilylation NMR techniques to identify Silicate species in Solution Light scattering and nucleation events Electron microscopy methods Theories of zeolite nucleation and growth Solid-gel transformation Zeolite crystallization from Solution So what's happening in there? Thermodynamics, telling us something Can we put it together? Organosilicates and organoaluminosilicates Polymorphs of silica Organic additives in zeolite synthesis Template theories Circumstantial evidence for the role of organic additives as 'templates' Non-spherical organic amines: diquats Void filier, buffer or what? ZSM-5(MFI) synthesis Step 1: synthesis from Na 2 0-Si0 2 -Al 2 03-H Step 2: addition of organic amines to change the Si/Al ratio Crown ethers in synthesis Synthetic routes to clathrasils Organometallic complexes in organosilicate synthesis Mesoporous silicas Organoaluminosilicates versus zeolites Observing differences in acidity Exploring bulky organic additives C/Nfactor Adamantane derivatives Tricyclodecane derivatives Slow-release sources of oxide reagents: zeolites and other microporous materials The next generation Specialized methods of synthesis Tailoring synthesis to applications Secondary methods of synthesis Dealumination Aluminum insertion into a Silicate or defected silica Non-aqueous synthesis Preformed zeolites and Silicates Large crystal production Microporous films and coatings Metal Silicate molecular sieves Molecular sieves and the periodic table Breaking the rules 208

5 CONTENTS Substitution of gallium for aluminum Germanium aluminate molecular sieves Boron Iron Comparing acidity and catalytic activity in M 3+ (M = B, AI, Ga, Fe) Silicates Beryllium incorporation into Silicate lattices Zinc Silicates Tin- and lead-containing materials Titanium Synthesis of other microporous metal Silicates Metal Sulfides: their inorganic chemistry The aluminophosphates Aluminophosphate molecular sieves: first examples of pentavalent framework ions Natural aluminophosphates Early synthetic aluminophosphates Phosphate zeolites Synthesis of aluminophosphate molecular sieves Role of the organic additive Stability and solubility Adding inorganic cations Studies of gel chemistry Changing aluminum coordination number in aluminophosphate materials Adsorption properties of aluminophosphate molecular sieves Structural information from 27 AI and M P NMR Gallophosphates Silica incorporation into aluminophosphates Metal aluminophosphates (MeAPO) and related materials New functional materials or interesting soil science? Identification of molecular sieve structures The bare necessities X-ray powder diffraction: identification of a crystalline material Typical examples of diffraction patterns from synthesis experiments Characterizing faulted phases Measuring X-ray crystallinity Aluminum content through unit cell volume expansion Identifying new materials Adsorption properties: pore volume Adsorption crystallinity Pore gaging Hydrophobicity and hydrophilicity Optical and scanning electron microscopy Acidity measurements from ammonia desorption Structural features from infrared spectroscopy Identification of 5-member rings Identifying Substitution of other elements from infrared spectroscopy Acid characteristics determined from infrared spectroscopy Structural identification by NMR spectroscopy NMR studies of silica-rich molecular sieves 316

6 CONTENTS XI Structural Information from alummum NMR High-resolution electron microscopy Molecular modeling Identification of structural features through catalytic test reactions Identification of new materials Appendix Zeolite structures 325 Prepared by DEWI LEWIS Index 339 Microporous materials and their structure codes 355