Zeolites and Zeolitic Materials Molecular sieves = highly organized matrices of tunable pore shape, size, and polarity for separation, recognition, and organization of molecules with precision of about 1 Á. detergent builders adsorbents size-shape selective catalysts supramolecular chemistry nanotechnology Chemical composition Silica Si02 Aluminosilicates MxIAlxSi2.x04. nH20 Aluminophosphates A1P04 (isoelectronic with Si204) Metallophosphates MP04 Silicoaluminophosphates M^SixAlP^ 04 Pores Channels ZSM-5[010] B&la [100] Zeolites and Zeolitic Materials >40 naturally occurring zeolites >139 structure types many hundreds of zeolite compounds Nomenclature www.iza-structure.org/databases Structure types - three capital letter codes (Most well known zeolite archetypes: SOD, LT A, FAU, MOR, MFI ) Four-connected frameworks Interrupted frameworks (denoted by a hyphen: -CLO, cloverite) Structure types do not depend on: chemical composition, element distribution, cell dimensions, symmetry Several zeolite compounds can belong to the same structure type: FAU - faujasite, Linde X, Y, Beryllophosphate-X, SAPO-37, Zincophosphate-X Zeolites and Zeolitic Materials Names of zeolite materials: trivial names - Alpha, Beta, Rho chemical names - Gallogermanate-A mineral names - Chabazite, Mordenite, Stilbite, Sodalite codes - A1P04-5, 8,11,..., 54, ZSM-4,18, 57,... brand names - Linde A, D, F, L, N, Q , R, T, W, X, Y university names VPI-5 (Virginia Polytechnical Institute) ULM (University Le Mans) 4 Zeolites and Zeolitic Materials Primary building units: A1(III)04, P(V)04 and Si(IV)04 tetrahedra Isoelectronic relationship (Si02); [AlSi04 ]- A1PO, Secondary (Structural) Building Units (SBU) 3R 4R 5R 6R 8R ^1 spiro-5 D4R D6R IP 4-1 D8R 4=1 4-2 4-4=1 5-1 5-2 5-3 6-2 2-6-2 6E1 (C6R) Chain composite building units (a) zig-zag unbranched single chain, periodicity of two (b) sawtooth unbranched single chain, periodicity of three (c) crankshaft unbranched single chain, periodicity of four (d) natrolite branched single chain (e) double crankshaft chain, an unbranched double chain (f) narsarsukite chain, a branched double chain (g) a pentasil chain doubt 4-mg (tMfíl Polyhedral composite building units i® Q islJleG-iMiflrtSFfl V&1 dCĽMeS-rníFÍMR) r.inirrnľv: rjK- rcflSviliŕ 8 Ö M z ! i, -; i —L E5'(l] [ť s'] USS61 I í'5'6'] IVť-] lsu*'J t4"6V] Sodalite Unit Truncated octahedron (c) Cubotahcdron Truncated euboctahedron " •■' 10 Sodalite Unit Packing of the sodalite units: SOD - bcc, sharing of 4-rings LTA - sc, 4-rings connected through O bridges FAU (faujasite) - cubic diamond, 6-rings connected through O bridges EMT - hexagonal diamond, 6-rings connected through O bridges Zeolite LTA 12 (a) [T04] tetrahedra as BBU (b) four-membered single rings (c) IB fuenfer chains (d) cubes [46] (e) truncated octahedra [4668] (sodalite- or ß-cages) (f) truncated cubeoctahedra [4126886] (a-cavities) 13 Pores in Zeolite A (LTA) (a) the sodalite cage [4668] (b) the a-cavity [4126886] (c) the 3-dimensional channel system (d) the 8-ring defining the 0.41 nm effective channel width 14 (a) D4R AFM growth studies of LTA S. Sugiyama et. al. Microporous and Mesoporous Materials 28 (1999) 1-7 Double-four ring (D4R) 0.7201 nm 1.2273nm 1.2273nm D4R 1.2273nm 16 Zeolite FAU (X and Y) and EMT FAU Cubic ABCABC... analagcnis 15-crown-5 stacking of to zinc structure layers agent hl ende directing agent EMT Hexagonal A B A B A B... an a 1 age u s LS-crown-6 stacking of towurtzite structure lay eis directing agent Fig. 1. Structure of zeolite Y: (a) cubic polymorph known as FAU with ABCABC.. stacking (b) hexagonal polymorph known as EMT with AB ABAB... Hacking. 17 Molecular Sieves ite Cation Code Pore diameter ite A: Na 4A 0.42 nm Ca 5A 0.48 nm Na, K 3A 0.38 nm iteX: Na 13X 0.8-1.0 nm Ca ÍOX 0.7 nm Zeolite Y contains more Si 18 Framework Framework density (FD) fd 16- Defined as the number of tetrahedral atoms (T-atoms) per cubic nanometer (1000 A3) n- FD is related to the void volume of the crystal: as the FD value decreases, the void volume and capacity for adsorption increases 16 - FD < 20 are characteristic of microporous structures w- the minimum known FD is 12.5 with the void occupying just over half of the crystal volume 10 - Density ■=. ■■r-—-* quartz IUI tadh ;il J- GOD!« fj.' L J" TBL ľiC^ld na J I U" -.9 ľ mHf ■ 4» "T 19 n^ ^r^ ^^ ^r^ 4+ s 5+ e Size of Smalte st Ring Pores Various sizes (4 -13 Á), shapes (circular, elliptical, cloverleaf-like), and connectivity (1-3D) The size of the rings formed by the T04 tetrahedra ranges from 4 to 18 of the T-atoms and determines the pore aperture Extraframework charge-balancing cations Ion-exchangeable, size, charge, positions, distribution, ordering, coordination number Si-to-Al ratio Influences cation content, hydro-phobicity/-philicity, acidity Löwenstein rule: absence of the Al-O-Al moieties, in aluminosilicates Si/Al > 1 Linde A (LTA) Si/Al = 1 ZK-4 (LTA) Si/Al = 2.5 ZSM-5 Si/Al = 20 - 00 Pure Si02 Si/Al = 00 Pentasils ZSM-5 Zeolite Synthesis Synthesis - an empirical and heuristic process, new phases are often discovered by serendipity Aluminosilicates - high pH Ô Mixing NaAl(OH)4(aq) + Na2Si03(aq) + NaOH(aq), 25 °C, condensation-polymerization, gel formation Ô Ageing Na(H20)n+ template effect -^ Naa(A102)b(Si02)c.NaOH.H20(gel) -> 25-175 °C Ô Hydrothermal crystallization of amorphous gel, 60-200 °C Nax(A102)x(Si02)rzH20(crystals) Ô Separation of the solid product by filtration Ô Calcination - occluded water, removed by 25-500 °C vacuum thermal dehydration -template removal - calcination in 02 at 400-900 °C removes the guest molecules from the framework without altering it - extraction (neutral templates) Zeolite Synthesis Structure of the zeolite product depends on: - Composition - Concentrations and reactant ratios - Order of mixing - Temperature - Ageing time (hours to weeks) - Crystallization time (days to weeks, kinetics of the structure-directing process is slow) -pH - Stirring/no stirring - Pressure - Seeding - Reactor material (PTFE, glass, steel) - Templates Templates: Organic cationic quaternary alkylammonium salts, alkylamines, aminoalcohols, crownethers, structure-directing, space-filling, charge-balancing Vary the template - discover new structures ! T ■ * . „ Templates Template or guest compounds A Three levels of the guest action with increasing structure-directing specificity: ■ Space-filling - the least specific, observed, for example, in the synthesis of AlP04-5,23 different, structurally unrelated compounds, could be employed, they pack in the channels of the structure thereby increasing its stability. ■ Structure-directing - a higher degree of specificity, only tetramethylammonium hydroxide is effective in the synthesis of AIPO4-2O -elongated molecules, such as linear diamines, initiate the formation of channels -nondirectional-shaped guests leads to the formation of cage-like cavities, the size of these cavities correlates with the size of freely rotating guests ■ True templating - very rare, it requires even more precise host-guest fit which results in the cessation of the free guest-molecule rotation A curiosity: aluminophosphate VPI-5 does not require any guest for its formation! 23 Templates The ratio T02/(C + N + O) is a measure of space-fillin of the framework by the guest molecules, characteristic for a specific guest and structure. Existence of primary and secondary units in a synthesis mixture 4R, 6R, 8R, D4R, D6R, 5-1, cubooctahedron Zeolite Synthesis Mechanisms (a) gel dissolution and solution mediated crystallization (SBU in solution) a x (b) "in situ" rearrangement of the gel 25 Zeolite Synthesis Mechanisms Mechanism of structure-directing action of the TPA template I 3 ^-H- H soluble silicate species \ v< jr* $ 26 Zeolites and zeolitic materials Wide range of solid state characterization methods for zeolites: diffraction, microscopy, spectroscopy, thermal, adsorption and so forth Zeolite post modification for controlling properties of zeolites Tailoring channel, cage, window dimensions: -^Cation choice (Ca exchanged for Na ) -^Larger Si/Al decreases unit cell parametrs, window size decreases number of cations, free space increases hydrophobicity -^Reaction temperature, higher T, larger pores 27 Stability Rules Löwenstein rule: never Al-O-Al Dempsey rule: Al-0-Si-O-Si-O-Al is more stable than Al-0-Si-O-Al NNN-principle Bronsted Acidity Tuning Bronsted acidity: Ion exchange for NH4+ Pyrolysis to expel NH3 Calcination to expel H20 Solid acid for the hydrocarbon cracking The larger the Si/Al ratio,the more acidic is the zeolite Na 0 Na © O. Si ,0 0.0. Al Si /\ O o .0 0.o. Al ,0 Si /\ O o Ion Exchange 0 +NH4 0 NH4 O. .0.0.0. Si Al o^o J\ 0 -Na 0 NH4 O. © ^O. .0 Si Al Si /V „A A 0 0 0 0 0 0 Heating H •N,--0-!,'-'0 NH3 Bronsted acid H 0 Nr /\ o o -O. © .0 0 ,0 AI Si .A A oooo Calcination 600 »C -H20 Lewis acid O. ,0. Si 0^0 Al 0A0 v A o o o 0/0> AI ,0 Si /\ O o 29 Brensted Acidity Protonation of hydrocarbons Size- Size-shape selective catalysis, separations, sensing Selectivity at: •Reactants •Products •Transition state hape Selectivity H3C CH2 CH2 CH2 OH OH CH2 CH3 CH2 CH2 CH^ CH3 Or; H3C^ CH3CH3 A ŕ L, C CH CH3 CH2 CH 3 H;JC gH3?H3 OH OH .CH CH2 CH3 4V PRODUCT OH j5-l C" H3C-f VCH2-CH3 *—' OH TZZZZTŽZi OH CH3 HjC—CH2 CH2 CH3 TRANSITION STAI p-xylene ch3 /77-xylene ^/j^J / / / //^ / l^Q L-------->H3C^^>)ch2 -^- - no tolu oh h3c^^> oh no triff H3C^CS>sCH2 °H-^-». no toluene, Hlc^^> oh no trimethyl- SzzsázŽzzzŽS benzenes 31 Separation of xylene isomers by pervaporation thru a MFI membrane 32 Zeolite Applications Odor control, adsorbents Ion exchange capacity, water softening, detergents (25wt% zeolite) Host-guest inclusion, atoms, ions, molecules, radicals, organometallics, coordination compounds, clusters, polymers (conducting, insulating) Nanoreaction chambers Advanced zeolite devices, electronic, optical, magnetic applications, nanoscale materials, size tunable properties, QSEs HRTEM 34 Aquaculture Ammonia filtration in fish hatcheries Biofilter media Agriculture Odor control Confined animal environmental control Livestock feed additives Horticulture Nurseries, Greenhouses Floriculture Vegetables/herbs Foliage Tree and shrub transplanting Turf grass soil amendment Reclamation, revegetation, landscaping Silviculture (forestry, tree plantations) Medium for hydroponie growing Household Products Household odor control Pet odor control Industrial Products Absorbents for oil and spills Gas separations Radioactive Waste Site remediation/decontamination Water Treatment Water filtration Heavy metal removal Swimming pools Wastewater Treatment Ammonia removal in municipal sludge/wastewater Heavy metal removal Septic leach fields Aluminophosphates "f Isoelectronic relationship of A1P04 to (Si02)2 +Ionic radius of Si4+ (0.26 Á) is very close to the average of the ionic radii of Al3+ (0.39 Á) and P5+ (0.17 Á) Many similarities between aluminosilicate and A1P04 molecular sieves Dense A1P04 phases are isomorphic with the structural forms of Si02: quartz, tridymite, and cristobalite Aluminosilicate framework charge balanced by extraframework cations Aluminophosphate frameworks neutral (A102~)(P02+) = A1P04 Aluminophosphates Some A1P04 structures are analogous to zeolites while other are novel and unique to this class of molecular sieves. Only even-number rings = the strict alternation of Al and P atoms Incorporation of elements such as Si, Mg, Fe, Ti, Co, Zn, Mn, Ga, Ge, Be, Li, As, and B into the tetrahedral sites of A1P04 gives a vast number of element-substituted molecular sieves (MeAPO, MeAPSO, SAPO) important heterogeneous catalysts M1+, M2+, and M3+ incorporate into the Al sites M5+ elements incorporate into the P sites This substitution introduces a negative charge on these frameworks. Si4+, Ti4+, and Ge4+ can either replace P and introduce a negative charge or a pair of these atoms can replace an Al/P pair and retain the charge neutrality. 37 Aluminophosphates Gallophosphates 39 Aluminophosphate Synthesis Aluminophosphates prepared by the hydrothermal synthesis Source of Al: pseudoboehmite, Al(0)(OH), Al(0/-Pr)3 Mixing with aqueous H3P04 in the equimolar ratio - low pH ! Forms an A1P04 gel, left to age One equivalent of a guest compound = template Crystallization in a reactor Separated by filtration, washed with water Calcination Other zeolite materials Oxide and non-oxide frameworks, sulfides, selenides Coordination frameworks, supramolecular zeolites The quest for larger and larger pore sizes 40 Metallo-Organic Framework Structures 41 A + — «r -Vigular ľnit Linear Unií (A) iL) Solvent /\ Z---i Triangle (A1,!,',) A Solvent Square (A'tL1^ Sohcnl c^ +/^S ■=> Skútri (A^A1,) Solvent Square {A^a'j} 110' Sfltwenl A £J FarsJIti.mnim (A lA1^ Solvent V* \ ioa \ / A L k-^-r Pernatou f a'jL1^ -O. . - - lid- + no -Os. . 130- + S*lrail O Soluni (*" >| rletagon (A^j Solvent Triangulär Prísna 78-M Solvent Octahedron (V4a\) Cube í a'iL'u) 109* Solvent > Cubwfabedim (A'jL1,,) 42 Metallo-Organic Framework Structures 30 +- OTf i R^P-Pl-PRj OTT 26R=El,ll=L 2TR=Ph,n=2 Scheme A. Self-Assembly of Dodecahedra 20 /** CH^Clfr acetone, rt n 60+ 60*OTf Ph,n=2 (09%) ■SwBSB&iffraJ 10 nm 43 Metallo-Organic Framework Structures 44 and Metallo-Organic Quartz 45