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HYDROTHERMAL SYNTHESIS AND CRYSTALLIZATION OF ZEOLITES

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Presentation on theme: "HYDROTHERMAL SYNTHESIS AND CRYSTALLIZATION OF ZEOLITES"— Presentation transcript:

1 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)  oC, hydrothermal crystallization of amorphous gel Nax(AlO2)x(SiO2)y.zH2O(crystals)

2 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 oC vacuum thermal dehydration Organic cationic templates, quaternary alkylammonium, structure-directing, space-filling, charge-balancing, discovery of new structures

3 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

4 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, D6R, 5-1, cubooctahedron

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8 ZEOLITE POST MODIFICATION FOR CONTROLLING PROPERTIES OF ZEOLITES
Tailoring channel, cage, window dimensions, adsorbents, gas separation, purification Tuning Brnsted acidity, hydrocarbon cracking Ion exchange capacity, Lewis acid-base character, water softening, detergents Size-shape selective catalysis, separations, sensing -reactant, product, transition state selectivity

9 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

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12 SHAPE SELECTIVE CATALYSIS - REACTANT, PRODUCT, TRANSITION STATE SELECTIVITY

13 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

14 Shape slective dehydration of normal and iso-butanols to butenes over calcium ion exchanged zeolite A and zeolite Y

15 DIAMOND LATTICE OF 1.3 nm SPHERICAL SUPERCAGES IN ZEOLITE Y

16 SIMPLIFIED NOTATION FOR ZEOLITE ION EXCHANGE, BRNSTED ACID SITE FORMATION AND DEALUMINATION TO HIGH SILICA ZEOLITES

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18 The changing face of zeolite science and technology - pore and channel dimensions way beyond 1 nm - periodic table of compositions

19 LAYER-BY-LAYER GROWTH OF ZEOLITE THIN FILMS FOR PERMSELECTIVE MEMBRANES

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21 ORGANICS ORGANIZING INORGANICS ABIOGENIC

22 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

23 LEARNING FROM NATURE - TEMPLATING INORGANICS WITH SINGLE MOLECULES AND SUPRAMOLECULAR ASSEMBLIES


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