HYDROTHERMAL SYNTHESIS AND CRYSTALLIZATION OF ZEOLITES Typical zeolite synthesis NaAl(OH) 4 (aq) +...

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