Isomorphous substitution of transition metals into zeolites as a tool for creation of new catalysts

Transcription

1 Isomorphous substitution of transition metals into zeolites as a tool for creation of new catalysts Frederik Tielens, Anna Wojtaszek, Maciej Trejda, Gabriella Skara, Frank De Proft, Monica Calatayud, Maria Ziolek, Stanislaw Dzwigaj NEXTLAB 2014 Rueil-Malmaison, France April

2 Methodology Combination of Experiment and Theory CMPUTATINAL CHEMISTRY Most calcuations are performed using:

3 Strategy Material characterization via computational techniques 1. Knowledge of the molecular structure of the material 2. Building the representative models 3. QC description of the models 4. Calculation of properties 5. Comparison with the experiment Detective job! Agatha Christie s Hercule Poirot The famous Belgian detective

4 Characterization of a surface Geometry: Angles, dihedrals, distances Vibrational Frequencies (IR-spectrum) NMR shifts Deprotonation energies, (acid/base prop.) Thermodynamics (hydration, oxidation envir.) Electron density properties Chemical reactivity descriptors Theory Experiment Vibrational Spectrum (IR and RAMAN) UV-Vis, XPS, EPR, NMR, Adsorption probe molec., Catalytic tests, Etc.

5 BEA zeolite Zeolites

6 Zeolites H TAl SD T = group V and VI Different xidation States Hydration 5

7 Zeolites Substitution of a T-site by Nb SD + M q+ MSD + 4+ Substutution Energy: /V: 1.54 ev /Nb: 0.57 ev /Ta: ev Ta/ substitution is more favorable than Nb/ and V/(IV) substitution For hypothetical ion-ion substitution with T = +IV But what for other environments?

8 Group I VSD Group II V BV4 Bond Breaking W4 BT4 V4 H-Transfer V H H T4 Reduction V H V5 H-Transfer B3 BV5 H V Bond Breaking T5 +H 2 +H +H Hydrolysis +H +H +H 2 2 +H TW4 BTT4 VW5 BTV5 Group III H-Transfer TT5 TW5 BTT5 +H +H Group IV

9 V H B3 V H H H H V H H BTT4 V H BV5 BT4 V H H BV4 V H H V H H H BTT5 V4 BTV5 V H H H V H H H TT5 7

10 Characterization What do the experimentalists bserve? EPR RAMAN/IR Acidity NMR Thermodynamics A. Wojtaszek, M. Ziolek, S. Dzwigaj, F. Tielens, Chem. Phys. Lett. 514, 70 (2011). F. Tielens, S. Dzwigaj, Chem. Phys. Lett. 501, 59 (2010). F. Tielens, T. Shishido, S. Dzwigaj, J. Phys. Chem. C 114, 9923 (2010). F. Tielens, S. Dzwigaj, Catal. Today 152, 62 (2010). F. Tielens, J. Comp. Chem. 30, 1946 (2009). F. Tielens, J. Mol. Struct. (THECHEM) 903, 23 (2009). F. Tielens, M. Calatayud, S. Dzwigaj, M. Che, Micropor. & Mesopor. Mater. 119, 137 (2009). F. Tielens, S. Dzwigaj, M. Trejda, M. Ziolek, Catal. Today 139, 221 (2008).

11 Characterization V-Zeolites lanol 3736 cm ? VBEA BEA V loaded BEA zeolite using FTIR in situ measurement

12 F. Tielens, S. Dzwigaj, M. Trejda, M. Ziolek, Catal. Today 139, 221 (2008). Characterization V-Zeolites V loaded BEA zeolite using FTIR in situ measurement H H T T H H H T lanol V(V)-H Bridging H V(IV)-H

13 V-H group o T H Energetically most favorable site X H H H T Beside the vanadyl site if there is a less stable V-H site, which is it? TT5 No V(IV)-H group, no bridging H V(V)-H group BEA Zeolite has 2 crystallographic sites! NLY 1 H GRUP PER VANADIUM H T T5 lens, M. Calatayud, S. Dzwigaj, M. Che, Micro. & Mesopor. Mater. 119, 137 (2009)

14 T= group V loaded BEA zeolite using RAMAN Characterization of V= environment! 2 environments explains the spectrum Isolated and hydroxylated V= group! A.E. Lewandowska, M.A. Banares, F. Tielens, M. Che, S. Dzwigaj., J. Phys.Chem. C 114, (2010).

15 The deprotonation and protonation energy ( E (de)prot. ) was used to study the reactivity. (increase in E indicates a decrease in acidity) ZeolH Zeol - + H + Zeol + H + ZeolH + E deprot. (ev) Protonation more easy than Deprotonation! Nb zeolites have basic Character E prot. (ev) T4 (-H) 5.95 T5 (Nb--H 2+ ) 4.82 T4 (Nb-H) 5.19 T5 (Nb-(H + )-) 4.32 Nb5 (-H) 5.92 Nb5(Nb=-H + ) 4.39 B3 ((H)Nb) 4.63 Nb5(Nb-(H + )-) 3.66 BNb4 ((H)Nb) 4.59 BNb4 (-H) 5.94 T5 (Nb-H) 5.17 Characterization Nb-Zeolites Bridging oxygen

16 T= or T-H sites/ effect of Al content E (T=) E (T-H) Al-SD -SD V Nb Ta V= Nb=/Nb-H Ta-H Independently of the presence of Al in the framework Al Na Metal(Group V) A. Wojtaszek, M. Trejda, M. Ziolek, F. Tielens, J. Phys. Chem. C (2012).

17 Phase Diagrams/Thermodynamics Effect of hydration and oxidizing environment The general expression for the free energy of a surface in equilibrium with particle reservoirs at the temperature T and pressure p: + = ), ( ), ( ), ( ),,, ( 1 ), ( mod mod p T N p T N p T G N N p T G A p T H H site el ref sodalite T H site el sodalite T µ µ γ 8

18 Thermodynamics 0-2 µ(η 2 ) -4 Nb + Nb + H µ( 2 ) F. Tielens, T. Shishido, S. Dzwigaj, J. Phys. Chem. C 114, 9923 (2010). 0 Nb H Nb Nb H H 2 - H H 2 Nb Niobium

19 Fukui Function Fukui Function & Elect. Pot. For a N electrons system the FF at a point r is defined as: µ: Electronic Chemical Potential = - atomic electronegativity ρ(r): Electron Density v(r): External Potential Electrophilic Attack Nucleophilic Attack High positive FF values correspond to reactive sites soft soft Interactions

20 Fukui Function & Elect. Pot. Electrostatic Potential Potential energy of a proton at point r Positive values: repulsion, low electron density Negative values: attraction, high electron density hard hard Interactions

21 Fukui Function & Elect. Pot. FF EP soft soft Interactions hard hard Interactions

22 Vanadium Niobium Tantalum licon T-atom xygen Hydrogen EP -7.41

23 V= Nb-H (Nb=) Nb + & Nb- - Ta-H Conclusions Group 5 and 6 framework sites in sodalite model/ BEA zeol. were investigated with: Periodic DFT Group 5 Acidity (Effect of Al!) IR, EPR, Acidity, UV-vis Group 6 Reducibility T(V)/T(IV) INCREASES Framework substitution F. Tielens, M.M. Islam, G. Skara, F. De Proft, T. Shishido, S. Dzwigaj, Micropor. Mesopor. Mater. 156, 66 (2012).

24 Amorphous lica

25 The elaboration of a representative model Started from bulk lica coordinates MD relaxation Geometry ptimization Charaterized IR freqs NMR shifts Hydration Very few models used at the ab initio/dft level! 1. Tielens (VASP) 2. P. Ugliengo (Crystal) Amorphous lica F. Tielens et al. Chem. Mater. 20, 3336 (2008). 16

26 Amorphous lica Properties in agreement with a real hydrated lica surface used in our experiments Aerosil Type lica F. Tielens et al. Chem. Mater. 20, 3336 (2008). 16

27 Amorphous lica/h2

28 Amorphous lica/h2 H 2 AIMD/CP2K Immobilized H 2 layer Amorphous lica A. Cimasa, J.Phys.Cond.Mat. In press

29 Amorphous lica/h2 lica Super Cell Interface Liquid water Interface Amorphous H 2 Amorphous 2 Representitive and predictive model lica A. Cimasa, J.Phys.Cond.Mat. In press

30

31 Bio-organic species grafted on metal oxide supports Pre-biotic chemistry origin of life on earth Evaluating the catalytic power of lica towards the polymerisation of amino acids Polymerisation de la glycine Adsorption mode of Glycine on silica Glycine + H 3 N-CH 2 -C - 2 Functional groups in interaction with surface silanols Lambert, J.-F. rig. Life Evol. Biosphere 2008, 38, 211 NMR 1 H, 13 C(C=) et 15 N

32 Acknowledgements High Performance Computing Centre

33 Thank you 33