Mol.Sieves (2004) 4:1–200 DOI 10.1007/b94235 Vibrational Spectroscopy Hellmut G.Karge1· Ekkehard Geidel2 1 Fritz-Haber-Institut der Max-Planck-Gesellschaft,Faradayweg 4–6,14195 Berlin,Germany E-mail:[email protected] 2 Institut für Physikalische Chemie,Universität Hamburg,Bundesstraße 45,20146 Hamburg, Germany.E-mail:[email protected] 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2 Theoretical Background . . . . . . . . . . . . . . . . . . . . . . 12 2.1 Normal Mode Analysis . . . . . . . . . . . . . . . . . . . . . . . 13 2.2 Molecular Mechanics . . . . . . . . . . . . . . . . . . . . . . . . 19 2.3 Molecular Dynamics Simulations . . . . . . . . . . . . . . . . . 21 2.4 Quantum Mechanical Calculations . . . . . . . . . . . . . . . . 24 2.5 Some Selected Examples ofModeling Zeolite Vibrational Spectra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 3 Spectra Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . 35 3.1 Qualitative Interpretation . . . . . . . . . . . . . . . . . . . . . 35 3.2 Quantitative Evaluation . . . . . . . . . . . . . . . . . . . . . . 35 4 Experimental Techniques . . . . . . . . . . . . . . . . . . . . . 40 4.1 Transmission IR Spectroscopy . . . . . . . . . . . . . . . . . . . 40 4.2 Diffuse Reflectance IR (Fourier Transform) Spectroscopy (DRIFT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 4.3 Photoacoustic IR Spectroscopy (PAS) . . . . . . . . . . . . . . . 43 4.4 Fourier Transform Infrared Emission Spectroscopy (FT-IRES) 44 4.5 Raman Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . 45 4.6 Inelastic Neutron Scattering Spectroscopy (INS) . . . . . . . . 47 5 Information Available from IR,Raman and Inelastic Neutron Scattering Spectroscopy . . . . . . . . . . . . . . . . . . . . . . 48 5.1 Introductory Remarks . . . . . . . . . . . . . . . . . . . . . . . 48 5.2 Framework Modes . . . . . . . . . . . . . . . . . . . . . . . . . 49 5.2.1 Pioneering Work . . . . . . . . . . . . . . . . . . . . . . . . . . 49 5.2.2 More Recent Investigations ofVarious Molecular Sieves . . . . 52 5.2.2.1 Faujasite-Type Zeolites (FAU) . . . . . . . . . . . . . . . . . . . 52 5.2.2.2 Zeolite A (LTA) . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 5.2.2.3 Sodalite (SOD) . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 5.2.2.4 Clinoptilolite (Heulandite-Like Structure,HEU) . . . . . . . . . 54 5.2.2.5 Erionite (ERI),Offretite (OFF) . . . . . . . . . . . . . . . . . . . 55 5.2.2.6 Zeolite L (LTL) . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 © Springer-Verlag Berlin Heidelberg 2004 2 H.G.Karge · E.Geidel 5.2.2.7 Zeolite Beta (BEA) . . . . . . . . . . . . . . . . . . . . . . . . . 55 5.2.2.8 Ferrierite (FER) . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 5.2.2.9 Chabazite (CHA) . . . . . . . . . . . . . . . . . . . . . . . . . . 55 5.2.2.10 ZSM-5 (MFI),ZSM-11 (MEL),MCM-22 (MWW), ZSM-35 (FER),ZSM-57 (MFS) . . . . . . . . . . . . . . . . . . . 56 5.2.2.11 AlPO s,SAPOs,MeAPOs . . . . . . . . . . . . . . . . . . . . . . 56 4 5.2.2.12 Miscellaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 5.2.3 Effect ofCation-Loading on Framework Vibrations . . . . . . . 57 5.2.4 Effect ofAdsorption on Framework Vibrations . . . . . . . . . 58 5.2.5 Effect ofDealumination and n /n Ratio on Framework Si Al Vibrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 5.2.6 Effect ofIsomorphous Substitution on Framework Vibrations 61 5.3 Cation Vibrations . . . . . . . . . . . . . . . . . . . . . . . . . . 64 5.3.1 Cation Vibrations in Pure Zeolites . . . . . . . . . . . . . . . . . 64 5.3.2 Cation Vibrations Affected by Adsorption . . . . . . . . . . . . 71 5.4 Hydroxy Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 5.4.1 Hydroxy Groups ofZeolites Characterized by IR Fundamental Stretching Bands . . . . . . . . . . . . . . . . . . . . . . . . . . 73 5.4.1.1 Faujasite-Type Zeolites (FAU) . . . . . . . . . . . . . . . . . . . 73 5.4.1.1.1 Non-Modified Faujasite-Type Zeolites . . . . . . . . . . . . . . 74 5.4.1.1.2 Dealuminated Faujasite-Type Zeolites . . . . . . . . . . . . . . 78 5.4.1.1.3 Cation-Exchanged Faujasite-Type Zeolites . . . . . . . . . . . . 82 5.4.1.2 Other Zeolites . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 5.4.1.2.1 Zeolite A (LTA) . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 5.4.1.2.2 Zeolite L (LTL) . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 5.4.1.2.3 Mordenite (MOR) . . . . . . . . . . . . . . . . . . . . . . . . . . 86 5.4.1.2.4 Heulandite (HEU) and Clinoptilolite . . . . . . . . . . . . . . . 87 5.4.1.2.5 Erionite (ERI) and Offretite (OFF) . . . . . . . . . . . . . . . . 88 5.4.1.2.6 Zeolite Beta (BEA) . . . . . . . . . . . . . . . . . . . . . . . . . 88 5.4.1.2.7 Ferrierite (FER) . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 5.4.1.2.8 Zeolites ZSM-5 (MFI) and ZSM-11 (MEL) . . . . . . . . . . . . 91 5.4.1.2.9 Miscellaneous:Zeolites MCM-22 (MWW),Chabazite (CHA), Omega (MAZ),ZSM-20 (EMT/FAU) and ZSM-22 (TON) . . . . 93 5.4.1.2.10 Isomorphously Substituted Molecular Sieves . . . . . . . . . . 94 5.4.1.2.11 SAPOs,MeAPOs and VPI-5 . . . . . . . . . . . . . . . . . . . . 94 5.4.2 Hydroxy Groups ofZeolites Characterized by Deformation, Overtone and Combination Bands . . . . . . . . . . . . . . . . 97 5.4.2.1 Characterization by Transmission IR Spectroscopy . . . . . . . 97 5.4.2.2 Characterization by Diffuse Reflectance IR Spectroscopy . . . . 98 5.4.2.3 Characterization by Inelastic Neutron Scattering Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 5.5 Characterization ofZeolite/Adsorbate Systems . . . . . . . . . 103 5.5.1 Introductory Remarks . . . . . . . . . . . . . . . . . . . . . . . 103 5.5.2 Selected Zeolite/Adsorbate Systems . . . . . . . . . . . . . . . . 106 5.5.2.1 Homonuclear Diatomic Molecules (N ,H ,D ,O ) 2 2 2 2 as Adsorbates . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 5.5.2.2 Carbon Monoxide (CO) as an Adsorbate . . . . . . . . . . . . . 111 Vibrational Spectroscopy 3 5.5.2.3 Linear Triatomic Molecules (N O,CO ) as Adsorbates . . . . . . 119 2 2 5.5.2.4 Methane (CH ) as an Adsorbate . . . . . . . . . . . . . . . . . . 122 4 5.5.2.5 Bent Triatomic Molecules (SO ,H S,H O) as Adsorbates . . . . 124 2 2 2 5.5.2.6 Adsorption ofProbe Molecules for the Characterization of Zeolitic Acidity and Basicity . . . . . . . . . . . . . . . . . . . . 130 5.5.2.6.1 Introductory Remarks . . . . . . . . . . . . . . . . . . . . . . . 130 5.5.2.6.2 Pyridine,Ammonia and Amines as Probes for Acid Sites . . . . 131 5.5.2.6.3 Hydrogen (Deuterium),Light Paraffins and Nitrogen as Probes for Acid Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 5.5.2.6.4 Nitriles as Probes for Acid Sites . . . . . . . . . . . . . . . . . . 138 5.5.2.6.5 Halogenated Hydrocarbons and Phosphines as Probes for Acid Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 5.5.2.6.6 Carbon Monoxide as a Probe for Acid Sites . . . . . . . . . . . . 140 5.5.2.6.7 Nitric Oxide as a Probe for Acid Sites . . . . . . . . . . . . . . . 143 5.5.2.6.8 Benzene and Phenol as Probes for Acid Sites . . . . . . . . . . . 145 5.5.2.6.9 Acetone and Acetylacetone as Probes for Acid Sites . . . . . . . 147 5.5.2.6.10 Probes for Basic Sites . . . . . . . . . . . . . . . . . . . . . . . . 147 5.5.2.7 Adsorption ofMethanol,Benzene,Simple Benzene Derivatives, Light Alkanes,Boranes and Silanes . . . . . . . . . . . . . . . . 149 5.5.2.8 Adsorption ofLarge and Complex Molecules . . . . . . . . . . 153 5.5.2.9 Infrared Micro-Spectroscopy ofMolecules in Single Crystals or Powders ofZeolites . . . . . . . . . . . . . . . . . . . . . . . 155 5.6 In-situ IR and Raman Spectroscopic Investigation ofProcesses in Zeolites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 5.6.1 Introductory Remarks . . . . . . . . . . . . . . . . . . . . . . . 156 5.6.2 Zeolite Synthesis and Crystallization . . . . . . . . . . . . . . . 156 5.6.3 Chemical Reactions in Zeolites . . . . . . . . . . . . . . . . . . 158 5.6.4 Diffusion in Zeolites . . . . . . . . . . . . . . . . . . . . . . . . 163 5.6.5 Kinetics ofSolid-State Ion Exchange in Zeolites . . . . . . . . . 168 6 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . 169 7 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 Abbreviationsa A zeolite structure (LTA,cf.[235]) A absorbance of,e.g.,OH groups in IR,A(OH),etc. A parameter in Eq.(13) A,A parameter in the Buckingham term ofEq.(16) i,j A,A parameter in the Lennard-Jones potential ofEq.(18) i,j a Unfortunately, many of the above-indicated abbreviations have various meanings (vide supra);in view ofthe current conventions in the literature,this is hardlyavoidable.However, thecorrect meaning ofthe abbreviations should follow from the respective context. 4 H.G.Karge · E.Geidel A initial absorbance initial A integrated absorbance int AD adsorption energy AN acetonitrile AlPO –n microporous aluminophosphate zeolite-like structure 4 (n=5,8,11,20,...,cf.[235]) A maximal absorbance max A absorbance after treatment treat B Brønsted (e.g.,Brønsted acid sites,B-sites,Brønsted acidity) B parameter in Eq.(13) B,B parameter in the Lennard-Jones potential ofEq.(18) i,j B formation matrix between internal and Cartesian displacement 33 coordinates B benzene BATE boric acid trimethyl ester BEA zeolite structure,acronym for zeolite Beta (cf.[235]) bpy 2,2¢-bipyridine [B]ZSM-5 zeolite structure (MFI,cf.[235]) containing boron in the framework C cation (C) site,cation Lewis acid site C,C parameter in the Buckingham term ofEq.(16) i,j C parameter in the dispersion term ofthe potential function i,j Eq.(21) c concentration c velocity oflight 0 C Brodskii constant in Eq.(24) B CA chemical analysis CE conventional ion exchange CHA zeolite structure;acronym for chabazite,(cf.[235]) CLIN abbreviation ofclinoptilolite;note:not a three-letter code according to [235];(clinoptilolite is isostructural with heulandite,HEU) CoAPO–n microporous aluminophosphate zeolite-like structures with cobalt in the AlPO –n framework (i.e.,MeAPO–n,Me=Co, 4 n=5 (AFT structure),n=11 (AEL structure),n=e.g.,31,37, 40,...cf.[235]) D transport diffusion coefficient D(B) diffusion coefficient ofbenzene D(T) diffusion coefficient oftoluene d thickness (ofa zeolite wafer in,e.g.,mg cm–2) DAM-1 Dallas amorphous material DAY dealuminated Y-type zeolite DEB diethylbenzene DENOX process for removal ofnitrogen oxides DEXAFS dispersive extended x-ray absorption fine structure DFT density functional theory DM dimethylphosphine Vibrational Spectroscopy 5 D4R double four-membered ring in,e.g.,the structure ofzeolite A D6R double six-membered ring in,e.g.,the structure ofzeolites X or Y D6R indicates a four-membered ring in the hexagonal prism of Fig.5 DPPH 2,2-diphenyl-1-picrylhydrazyl,ESR standard DRIFT diffuse reflectance IR Fourier transform (spectroscopy) DRS diffuse reflectance spectroscopy (in IR or UV-Visible region) DTG differential thermogravimetry DH (differential) heat ofadsorption ad E total energy E unit matrix 33 EB ethylbenzene EDAX energy dispersive x-ray (spectroscopy) EDS energy dispersive x-ray spectroscopy ElAPSO an MeAPSO material (see below) which contains in addition to the elements ofMeAPSO other ones (Li,Be,B,Ga,Ge,As,or Ti) [957] EM energy minimization EMT zeolite structure;hexagonal faujasite (cf.[235]) EMT/FAU structural intermediate (cf.ZSM-20,[235]) ERI zeolite structure;acronym for erionite (cf.[235]) ESR electron spin resonance (spectroscopy) Et N triethylamine 3 ETS-4 zeolite structure related to zorite (cf.[313–316]) ETS-10 zeolite structure (cf.[313–316]) EXAFS extended x-ray absorption fine structure F Schuster-Kubelka-Munk remission function F force constant matrix 33 F force constant F elements ofthe force constant matrix i,j Fr stretching force constant Fa bending force constant F second derivative ofthe total energy with respect to Cartesian X coordinates frr,faa,fra interaction force constants related to atomic distances (rr), i,j i,j i,j bond angles (aa),simultaneous change ofatomic distances and bond angles (ra) F stretching force constants ofTO bonds (T=Si,Al;cf.Eq.(13)) TO F stretching force constant ofthe SiO bond SiO F stretching force constant ofthe AlO bond AlO f(n) density ofvibrational states F electric field strength R F second derivative ofthe total energy with respect to internal R coordinates FAU zeolite structure;acronym for faujasite (cf.[235]) [Fe]ZSM-5 zeolite structure (MFI,cf.[235]) containing iron in the framework; cf.footnoteb 6 H.G.Karge · E.Geidel [Fe]MCM-41 mesoporous MCM-41 material containing iron in the pore walls, cf.footnoteb FER zeolite structure;acronym for ferrierite (cf.[235]) FIR far infrared (spectroscopy) FR frequency response (spectroscopy) FKS Flanigen-Khatami-Szymanski (correlation) fs femtosecond (=10–15s) FT Fourier transform FTIR Fourier transform infrared (spectroscopy) FT-IRES Fourier transform infrared emission spectroscopy FWHH full-width at half-height (ofa band) G–1 kinetic energy matrix 33 [Ga]BEA zeolite with Beta (BEA) structure containing gallium in the framework,(cf.[530–534]) [Ga]ZSM-5 zeolite with MFI structure containing gallium in the framework, (cf.[530]) GC gas chromatography GF indicates Wilson’s method to solve vibrational problems using the inverse ofthe kinetic energy matrix and the force constant matrix GVFF generalized valence force field ˆ H Hamilton operator h Planck’s constant H Hammett value (acidity and basicity scale) 0 HEU zeolite structure;acronym for heulandite (cf.[235]) HF Hartree-Fock (theory) HF high frequency (e.g.,HF band ofOH) 1H MAS NMRproton magic angle spinning nuclear magnetic resonance (spectroscopy) HMS hexagonal mesoporous silicate [783] I transmitted radiation energy I incident radiation energy 0 INS inelastic neutron scattering IQNS incoherent quasielastic neutron scattering IR infrared (spectroscopy) IRES infrared emission spectroscopy IVFF internal valence force field K absorption parameter in the Schuster-Kubelka-Munk remission function ofEq.(28) KED kinetic energy distribution K harmonic spring constant between a positively charged mass i point and a negatively charged massless shell in Eq.(17) b Presenting an element symbol in square brackets should indicate that the respective element is supposed to be incorporated into the framework ofthe material designated by the sub- sequent acronym or abbreviation.For instance,“[Ti]SOD”is indicating that titanium is in- corporated into the framework ofsodalite. Vibrational Spectroscopy 7 k improved angle bending force constant in Eq.(20) a L matrix transforming internal into normal coordinates 33 L Lewis (e.g.,Lewis acid sites,L-sites,Lewis acidity) L zeolite structure (LTL structure,cf.[235]) LF low-frequency (e.g.,LF band ofOH) LO longitudinal optical (splitting) LTA Linde type A zeolite (cf.[235]) LTL Linde type L zeolite (cf.[235]) M diagonal matrix ofatomic masses 44 M metal or metal cation M indicates a metal ofsort 1,e.g.,Na 1 M indicates a metal ofsort 2,e.g.,Ca 2 m cation mass (cf.,e.g.,Eq.(24)) MAS NMR magic angle spinning nuclear magnetic resonance (spectroscopy) MAZ zeolite structure;acronym for mazzite (cf.[235]) MFI zeolite structure (of,e.g.,ZSM-5 or silicalite,cf.[235]) MD molecular dynamics MeAPO microporous metal aluminophosphate zeolite-like structure with metal (Me) in the framework [235,501,957] MAPSO-37 an MeAPSO material (see below) with Me=Mg [235,501,957] MeAPSO microporous metal aluminophospate zeolite-like structures with metal (Me) and additionally silicon in the framework [235, 501,957] MCM-22 zeolite structure (acronym or IZA structure code is MWW; cf.[235]) MCM-41 mesoporous material with hexagonal arrangement ofthe uniform mesopores (cf.Volume 1,Chapter 4 ofthis series) MCM-48 mesoporous material with cubic arrangement ofthe uniform mesopores (cf.Volume 1,Chapter 4 ofthis series) MCM-58 zeolite structure (acronym or IZA structure code is IFR) MIR mid infrared (spectroscopy) MM molecular mechanics MO molecular orbital MOR zeolite structure;acronym for mordenite (cf.[235]) MP2 Møller-Plesset perturbation theory truncated at second order MR membered ring (xMR:x-membered ring,x=3,4,5,6,8,10,12,etc.) n librational quantum number n /n ratio ofmetal to aluminum atoms in the framework M Al n /n ratio ofsilicon to aluminum atoms in the framework Si Al n-Bu N tri-n-butylamine 3 NCA normal coordinate analysis NCL-1 high-silica (n /n =20 to infinity) zeolite (cf.[337]) Si Al NMA normal mode analysis NIR near infrared (spectroscopy) NIR-FT near infrared Fourier transform (spectroscopy) NU-1 zeolite structure (cf.RUT,RUB-10 [235]) OFF zeolite structure,acronym for offretite (cf.[235]) 8 H.G.Karge · E.Geidel O-T-O angle between adjacent T (T=Si,Al,etc.) and O atoms inside a tetrahedron OTO framework fragment,i.e.,OSiO or OAlO P branch ofa vibrational-rotational spectrum (P branch) p,p parameter in the Buckingham term ofEq.(16) i,j PAS photoacoustic (infrared) spectroscopy Pc phthalocyanine PED potential energy distribution PES potential energy surface n-Pr N tri-n-propylamine 3 PT proton transfer PV pivalonitrile (2,2-dimethylproprionitrile) p-X para-xylene Py pyridine Q branch ofa vibrational-rotational spectrum (Q branch) Q normal coordinate (column vector) • Q time derivative ofthe normal coordinate QT transpose ofthe column vector Q q,q,q atomic charges i j q cation charges QM quantum mechanical (calculations) R internal displacement coordinate (column vector) • R time derivative ofan internal displacement coordinate R branch ofa vibrational-rotational spectrum (R branch) R diffuse reflectance ofan infinitely (i.e.,very) thick sample • R actual distance between the ith core and its shell in Eq.(17) i RR resonance Raman (spectroscopy) r cation radius r,r atomic distances along chemical bonds i j r bond length between T and O (T=Si,Al) in Eq.(13) TO RE rare earth metal (cation) RHO zeolite structure,acronym for zeolite rho (cf.[235]) S1,S2,S3 cation positions in the structure ofzeolite A (adjacent to the single six-membered ring openings to the b-cages,near the center ofthe eight-membered ring openings to the (large) a-cages and in the center ofthe (large) a-cages,respectively) SI,SI¢,SII,SII¢,SIII cation positions in zeolite X or Y,i.e.,FAU (cf.[236]) S scattering parameter in the Schuster-Kubelka-Munk remission function ofEq.(28) s,s ionic radii i j SAPO-n microporous silicoaluminophosphates,n=5,17,18,20,31,34,39 etc.(cf.[235]) SCR selective catalytic reduction [Si]MFI MFI-type zeolite structure containing (exclusively) Si as T-atoms, i.e.silicalite-1;cf.footnoteb [Si]SOD SOD-type zeolite structure containing (exclusively) Si as T-atoms; cf.footnoteb Vibrational Spectroscopy 9 [Si,Fe]MFI MFI-type zeolite structure containing Si and Fe as T-atoms; cf.footnoteb [Si,Ti]MFI MFI-type zeolite structure containing Si and Ti as T-atoms; cf.footnoteb [Si,Fe]BEA zeolite structure ofBeta-type (BEA) with small amounts ofiron besides silicon in the framework;cf.footnoteb [Si,Ti]BEA zeolite structure ofBeta-type (BEA) with small amounts of titanium besides silicon in the framework,[336];cf.footnoteb [Si,V]MFI MFI-type zeolite structure with small amounts ofvanadium besides silicon in the framework;cf.footnoteb [Si,Ti]MFE zeolite structure ofZSM-11 type (MFE) with small amounts of titanium besides silicon in the framework;cf.footnoteb [Si,Al]MCM-41 mesoporous MCM-41 material containing both silicon and aluminum in the walls ofthe pores,[350,351];cf.footnoteb [Si,Ti]MCM-41 mesoporous MCM-41 material containing both silicon and titanium in the walls ofthe pores [350,351];cf.footnoteb [Si,V]MCM-41 mesoporous MCM-41 material containing both silicon and vanadium in the walls ofthe pores [350,351];cf.footnoteb SGVFF simplified generalized valence force field S intermediate Sanderson electronegativity int SOD zeolite structure,acronym for sodalite (cf.[235]) SOD four-membered rings in the sodalite structure (particular meaning in Fig.5) SQM scaled quantum mechanical (force field) SSZ-n series ofzeolite structures;aluminosilicates,e.g.,SSZ-24 and SSZ-13,isostructural with corresponding aluminophosphates, AlPO –5 (AFI) and AlPO –34 (CHA structure) (cf.[235]) 4 4 SUZ-4 zeolite structure [877] T (tetrahedrally coordinated) framework atom (cation) such as Si,Al,Ti,Fe,V,B T absolute temperature,in Kelvin (K) T indicating the transpose ofa matrix or column vector T kinetic energy T transmittance (transmission) T* transmittance (transmission) ofthe background (base line) T toluene TAPSO Ti-containing microporous silicoaluminophosphate ofthe MeAPSO family [335,573] T kinetic energy ofelectrons E T kinetic energy ofnuclei N TEHEAOH triethyl(2-hydroxyethyl)ammonium hydroxide [Ti]MMM-1 Ti-containing material with both mesoporous (MCM-41) and microporous (TS-1) constituents [353];cf.footnotebofthe table TO framework fragment (SiO,AlO,etc.) TMP trimethylphosphine TO transversal optical (splitting) TON zeolite structure;acronym for theta-1 (cf.[235]) 10 H.G.Karge · E.Geidel T-O-T angle between adjacent T and O atoms (T=Si,Al,Ti,etc.) TPA tetrapropylammonium TPAOH tetrapropylammonium hydroxide TPD temperature-programmed desorption TPO temperature-programmed oxidation TPR temperature-programmed reduction TS-1 ZSM-5 (MFI) structure containing small amounts oftitanium besides silicon in the framework TS-2 ZSM-11 (MFE) structure containing small amounts oftitanium besides silicon in the framework TMS tetramethylsilane UV-Vis ultraviolet-visible (spectroscopy) US-Y ultrastable Y-type zeolite V potential energy V term ofthe potential function accounting for the electrostatic framework-cation interaction Vcore-shell additional term ofthe potential function accounting for oxygen anions and extra-framework cations V potential energy originating from electron-electron repulsion EE V potential energy originating from nucleus-nucleus repulsion NN V potential energy originating from electron-nucleus attraction EN V Lennard-Jones (12–6) potential ij v vibrational quantum number VPI-5 microporous aluminophosphate zeolite-like structure (VFI, cf.[235]) VPI-7 zeolite structure (VSV;cf.[235,279,280]) VPI-8 microporous all-silica zeolite-like structure (VET,cf.[235]) VS-1 zeolite structure (MFI,cf.[235]) containing vanadium besides silicon in the framework [V]ZSM-5 zeolite structure (MFI,cf.[235]) containing vanadium in the framework (VS-1);cf.footnoteb [V]MCM-41 mesoporous MCM-41 material containing vanadium in the pore walls X zeolite structure (faujasite-type structure with n /n <2.5, Si Al cf.[235]) X xylene XAS x-ray absorption spectroscopy XRD x-ray diffraction Y zeolite structure (faujasite-type structure with n /n ≥2.5, Si Al cf.[235]) YAG yttrium aluminum garnet (laser) Z frequently used as an abbreviation of“zeolite”or a (charged) “zeolite fragment” ZBS zirconium-containing mesoporous material [778] ZK-4 zeolite structure (LTA,cf.[235]) ZSM-5 zeolite structure (MFI,cf.[235]) ZSM-11 zeolite structure (MFE,cf.[235])