1 H MAS NMR spectra including TRAPDOR 29 Si MAS NMR 27 Al 3QMAS NMR 27 Al MAS NMR

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Solid-state NMR studies on microporous and mesoporous materials concerning their structure, acidity and catalytic activity. 1 HMASNMR spectra including TRAPDOR 29 Si MAS NMR 27 Al 3QMAS NMR 27 Al MAS NMR 1 H MAS NMR in the range from 160 K to 790 K. - PowerPoint PPT Presentation

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  • Solid-state NMR studies onmicroporous and mesoporous materialsconcerning their structure, acidity and catalytic activityDieter Freude, Institut fr Experimentelle Physik I der Universitt Leipzig METU-Center Workshop on Solid State NMR, 1 November 20071HMASNMR spectra including TRAPDOR29Si MAS NMR27Al 3QMAS NMR27Al MAS NMR1H MAS NMR in the range from 160 K to 790 K

  • 1HMASNMR spectra, TRAPDORH-ZSM-5 activated at 550 C 4 20246 8 10 / ppm 20 468 10 / ppm44.2 ppm2.9 ppm2.9 ppm2.2 ppm1.7 ppm2.2 ppm1.7 ppm2.9 ppm2.9 ppmwith dephasingwithout dephasingdifference spectra2Without and with dipolar dephasing by 27Alhighpower irradiation and difference spectra are shown from the top to the bottom. The spectra show signals of SiOH groups at framework defects, SiOHAl bridging hydroxyl groups, AlOH group.H-ZSM-5 activated at 900 C4.2 ppm4.2 ppm4.2 ppm

  • 1H MAS NMR of porous materials

    MeOH

    Metal or cation OH groups in large cavities or at the outer surface of particles

    SiOH

    Silanol group at the externel surface or at lattice defects

    AlOH

    OH groups bonded to extra-framework aluminium species located in cavities or channels involved in

    hydrogen bonds

    CaOH, AlOH, LaOH

    Cation OH groups located in sodalite cages of zeolite Y and in channels of

    ZSM-5 involved in hydrogen bonds

    SiOHAl

    Bridging OH groups in large channels and cages of zeolites

    SiOH

    Disturbed bridging OH groups in zeolite

    H-ZSM-5 and H-Beta

    SiOHAl

    Bridging OH groups in small channels and cages of zeolites

    1

    3

    ppm

    5

    7

    6

    4

    2

    0

  • 29Si MAS NMR spectrum of silicalite-1SiO2 framework consisting of 24 crystallographic different silicon sites per unit cell (Fyfe 1987).

  • 29Si MAS NMR

    Q3

    Q4

    Q3

    aluminosilicate-type zeolites

    Si(3Si, 1OH)

    Si(4Al)

    Si(3Al)

    Si(2Al)

    Si(0Al)

    Si(1Al)

    Q4

    Q1

    Q2

    Q0

    alkali and

    alkaline earth silicates

    Q4

    zincosilicate-type zeolites

    VP-7, VPI-9

    Si(2Zn)

    Si(1Zn)

    ppm

  • 27Al 3QMAS NMR study of AlPO4-14 AlPO4-14, 27Al 3QMAS spectrum (split-t1-whole-echo, DFS pulse) measured at 17.6 T with a rotation frequency of 30 kHz. The parameters dCS, iso = 1.3 ppm, Cqcc = 2.57 MHz, h = 0.7 for aluminum nuclei at position 1, dCS, iso = 42.9 ppm, Cqcc = 1.74 MHz, h = 0.63, for aluminum nuclei at position 2, dCS, iso = 43.5 ppm, Cqcc = 4.08 MHz, h = 0.82, for aluminum nuclei at position 3, dCS, iso = 27.1 ppm, Cqcc = 5.58 MHz, h = 0.97, for aluminum nuclei at position 5, dCS, iso = -1.3 ppm, Cqcc = 2.57 MHz, h = 0.7 were taken from Fernandez et al.

    position 1

    40

    30

    1/ ppm

    20

    10

    0

    2/ ppm

    position 2

    40

    30

    20

    10

    0

    position 3

    position 5

  • 27Al MAS NMR spectra of a hydrothermally treated zeolite ZSM-5 A signal narrowing by MQMAS or DOR is useless, if the line broadening is dominated by distributions of the chemical shifts.

  • 27Al MAS NMR

    aluminosilicates

    aluminophosphates

    aluminoborates

    aluminosilicates

    aluminates

    aluminophosphates

    aluminoborates

    aluminosilicates

    aluminates

    aluminophosphates

    aluminoborates

    aluminosilicates

    aluminates

    20

    ppm

    120

    110

    10

    100

    90

    80

    70

    60

    50

    40

    30

    20

    10

    0

    6-fold

    coordinated

    5-fold

    coordinated

    4-fold

    coordinated

    3-fold

    coord.

  • Mobility of the Brnsted sites and hydrogen exchange in zeolitesProton mobility of bridging hydroxyl groups in zeolites H-Y and H-ZSM-5 can be monitored in the temperature range from 160 to 790 K. The full width at half maximum of the 1H MAS NMR spectrum narrows by a factor of 24 for zeolite H-ZSM-5 and a factor of 55 for zeolite 85 H-Y. Activation energies in the range 20-80 kJ mol-1 have been determined.

    one-site jumps around one aluminum atom multiple-site jumps along several aluminum atoms

  • Narrowing onset and correlation time40 C120C3,2 kHz17 kHzThe correlation time corresponds to the mean residence time of an ammonium ion at an oxygen ring of the framework.2HNMR, H-Y: at50 C tc=5 s 1HNMR, H-Y: at 40 C tc=20 s 2HNMR, H-ZSM-5: at 120 C tc=3,8 sdn=dnrigid/2dn=dnrigid/22H MAS NMR, deuterated zeolite H-ZSM-5, loaded with 0.33NH3 per crossing1HMAS NMR, zeolite H-Y, loaded with mit 0.6 NH3 per cavityThe correlation time corresponds to the mean residence time of an ammonium ion at an oxygen ring of the framework.

    2,5

    3,0

    3,5

    4,0

    4,5

    5,0

    5,5

    6,0

    1

    10

    20

    1000 T 1/ K1

    1,5

    2,0

    2,5

    3,0

    3,5

    4,0

    4,5

    5,0

    5,5

    0,1

    1

    10

    1000 T 1/ K1

    fwhm of the sideband envelope / kHz

  • 1D 1H EXSY (exchange spectroscopy)EXSY pulse sequenceEvolution timet1=1/4 Dn . Dn denotes the frequency difference of the exchanging species. MAS frequency should be a multiple of Dn Two series of measurements should be performed at each temperature: OffsetDn right of the right signal and offsetDn left of the left signal.

  • Result of the EXSY experimentStack plot of the spectra of zeolite H-Y loaded with 0.35 ammonia molecules per cavity. Mixing times are between tm=3ms and15s.Intensities of the signals of ammonium ions and OH groups for zeoliteH-Y loaded with 1.5ammonia molecules per cavity. Measured at 87C in the field of 9,4T. The figure on the top and bottom correspond to offset on the left hand side and right hand side of the signals, respectively.

    12

    10

    8

    6

    4

    2

    0

    Intensity

    OH

    ammonium ions

    12

    10

    8

    6

    4

    2

    0

    mixing time tm / s

  • Basis of the data processing diagonal peakscross peaksdynamic matrix (without spin diffusion):

  • Laser supported 1H MAS NMRSpectra (at left) and Arrhenius plot (above) of the temperature dependent 1H MAS NMR measurements which were obtained by laser heating. The zeolite sample H-Y was activated at 400 C.

    623 K

    40

    573 K

    20

    423 K

    0

    673 K

    20

    773 K

    723 K

    297 K

    / ppm

    40

    _1225625092.unknown

    1/2 / kHz

    1000 T / K

    10

    1

    0.1

    3.5

    3.0

    2.5

    2.0

    1.5

    1.0

    _1225625092.unknown

  • Laser supported high-temperature MAS NMRfor time-resolved in situ studies of reaction stepsin heterogeneous catalysis: the NMR batch reactor

  • Proton transfer between Brnsted sites and benzene molecules in zeolites H-YIn situ 1H MAS NMR spectroscopy of the proton transfer between bridging hydroxyl groups and benzene molecules yields temperature dependent exchange rates over more than five orders of magnitude. H-D exchange and NOESY MAS NMR experiments were performed by both conventional and laser heating up to 600 K.

  • Exchange rate as a dynamic measure of Brnsted acidityArrhenius plot of the H-D and H-H exchange rates for benzene molecules in the zeolites 85 H-Y and 92 H-Y. The values which are marked by blue or red were measured by laser heating or conventional heating, respectively.The variation of the Si/Al ratio in the zeolite H-Y causes a change of the deprotonation energy and can explain the differences of the exchange rate of one order of magnitude in the temperature region of 350600 K. However, our experimental results are not sufficient to exclude that a variation of the pre-exponential factor caused by steric effects like the existence of non-framework aluminum species is the origin of the different rates of the proton transfer.

  • I acknowledge support fromHorst ErnstClemens GottertJohanna KanellopoulosBernd KnorrLutz MoschkowitzDagmar PragerDenis Schneider

    Deutsche ForschungsgemeinschaftMax-Buchner-Stiftung

    NMR-Untersuchungen der Protonenbeweglichkeit liefern experimentelle Erkenntnisse(Sprungzeiten, Aktivierungsenergien) mit denen man Quantenchemische Modelle berprfen kann. Das erste Zitat demonstriert die langjhrige Kooperation zwischen unserer NMR-Spektroskopie und Quantenchemie, d.h. mit Professor Sauer verbunden. Eine schon seit vielen Jahren diskutierte Frage ist, ob wir haben vor allem Sprnge um ein Aluminium-Atom-keine Diffusion, oder verursacht die Protonenbeweglichkeit eine Translationsbewegung? Im zweiten Zitat betrachtet sauer die Bewegung um ein Aluminiumatom. Im Dritten Zitat werden Translationssprnge . Leider mu ich vorneweg nehmen, dass das Ergebnis dieser Untersuchung zu der langjhrigen guten Zusammenarbeit mit Sauer nicht beitragen wird, da es sich in unserem Fall um eien Vehikelmechanismus handelt, der in Arbeiten bis jetzt noch nicht berechnet worden ist.

    Der berrgang von einem Festkrper-Temperaturunabhngiges T2- und einem beweglichen Bereich (1/T2=tc*M2) Anpassung, Eckpunte , Am Abknickpunkt ist tc gegeben. Unter deer Korrelation kann man sich eine Sprungzeit vorstellen. Groe Sprnge: Korrelation zur vohergehenden Orientierung ist weitesgehend verloren. Die Korrelationszeit ist dadurch gegeben, dass zwischen 2 Sprngen oder innerhalb eines Sprungs die Korrelation der Dipolaren WW zerstrt wird.

    Ploss u.a. [47] haben eine Lorentz-hnliche statische Festkrper-Linienform betrachtet, die man dadurch beschreiben kann, dass eine Lorentzline nach dem zehnfachen der Linienbreite abbricht. Fr eine solche Linienform lsst sich im Gegensatz zu Gl.(1.9)(1.15)berechnen [47], wobei dnrigid die bei tiefen Temperaturen zu beobachtende temperaturunabhngige statische Halbwertsbreite be

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