HYDROTHERMAL SYNTHESIS AND CRYSTALLIZATION OF ZEOLITES
• Typical zeolite synthesis
• NaAl(OH)4(aq) + Na2SiO3(aq) + NaOH(aq), 25oC, condensation-polymerization, Na(H2O)n
+ template
• Naa(AlO2)b(SiO2)c.NaOH.H2O(gel) 25-175oC, hydrothermal crystallization of amorphous gel
• Nax(AlO2)x(SiO2)y.zH2O(crystals)
HYDROTHERMAL SYNTHESIS AND CRYSTALLIZATION OF ZEOLITES
• Nax(AlO2)x(SiO2)y.zH2O(crystals)
• Extraframework charge-balancing cations, templates, ion-exchangeable
• Framework Al(III)O4 and Si(IV)O4 tetrahedral primary building-blocks
• (AlO2)- and SiO2 stoichiometry for building blocks as bridging O
• Occluded water, removed by 25-500oC vacuum thermal dehydration
• Organic cationic templates, quaternary alkylammonium, structure-directing, space-filling, charge-balancing, discovery of new structures
ZEOLITE BUILDING UNITS
SHORTHAND NOTATION
Mq+
Cation binding site in six ring resembles crown ether-cation complex
Corner sharing SiO4/AlO4 tetrahedra
Six ring shorthand notation
BUILDING-BLOCK APPROACH TO ZEOLITE SYNTHESIS, STRUCTURES AND PROPERTIES
• Primary tetrahedral units, AlO2-, SiO2, PO2
+ and so forth, combined to give open-framework and framework charge, balanced by extraframework cations
• Existence of primary and secondary units in a synthesis mixture including:
• 4R, 6R, 8R, D4R, DR, 5-1, cubooctahedron
ZEOLITE POST MODIFICATION FOR CONTROLLING PROPERTIES OF ZEOLITES
• Tailoring channel, cage, window dimensions, adsorbents, gas separation, purification
• Tuning Brnsted acidity, hydrocarbon cracking
• Ion exchange capacity, Lewis acid-base character, water softening, detergents
• Size-shape selective catalysis, separations, sensing -reactant, product, transition state selectivity
ZEOLITE POST MODIFICATION FOR CONTROLLING PROPERTIES OF ZEOLITES
• Host-guest inclusion, atoms, ions, molecules, radicals, organometallics, coordination compounds, clusters, polymers (conducting, insulating), nanoreaction chambers
• Advanced zeolite devices, electronic, optical, magnetic applications
• Entry to nanoscale materials, size tunable properties, QSEs
SHAPE SELECTIVE CATALYSIS - REACTANT, PRODUCT, TRANSITION STATE SELECTIVITY
ALKYLATION OF TOLUENE BY METHANOL - SHAPE SELECTIVE CATALYTIC PRODUCTION OF p-XYLENE
Used for manufacture of terephthalic acid for production of polyester fibers
Snug fit can diffuse through channels
Shape slective dehydration of normal and iso-butanols to butenes over calcium ion exchanged zeolite A and zeolite Y
DIAMOND LATTICE OF 1.3 nm SPHERICAL
SUPERCAGES IN ZEOLITE Y
SIMPLIFIED NOTATION FOR ZEOLITE ION EXCHANGE, BRNSTED ACID SITE FORMATION AND
DEALUMINATION TO HIGH SILICA ZEOLITES
The changing face of zeolite science and
technology - pore and channel dimensions way beyond 1 nm -
periodic table of compositions
LAYER-BY-LAYER GROWTH OF ZEOLITE THIN FILMS FOR PERMSELECTIVE MEMBRANES
ORGANICS ORGANIZING INORGANICS
ABIOGENIC
ARCHITECTURAL CONTROL - TEMPLATE DIRECTED TRANSFORMATION OF BUILDING
BLOCKS TO OPEN FRAMEWORK SOLIDS
Ge4S104-
adamantanoid building block
Mq+ links building blocks via S binding and structure directed by Me4N+ template
LEARNING FROM NATURE - TEMPLATING INORGANICS WITH SINGLE MOLECULES AND
SUPRAMOLECULAR ASSEMBLIES