DFT Reactivity Descriptors and Catalysis - Vrije Universiteit Brussel

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Sequence AlCl 3 < L 1 < BF 3 < Al(OH) 3 ; also for H-exchange reaction ? Note: all hardness related descriptors failed in describing these reactions Lewis acid catalyzed reactions are much better described by softness related descriptors than the acid zeolite catalyzed ones. AlCl 3 always more active than BF 3 in agreement with experimental data. Ranking of Al(OH) 3 and L 1 with comparative active centers less obvious and incites further research on structure /acid strength of Lewis acid sites in zeolites A.M.Vos, R.A.Schoonheydt, F.De Proft, P.Geerlings, J.Catal. 220, 333 (2003) P. Geerlings, A.M. Vos, R. Schoonheydt, J.Mol.Struct. (Theochem), 762, 69 (2006) (A. Goursot Festschift) Pag. 30-9-2008 34
4. Towards the Inclusion of Confinement Effects • Relevance cfr. PCCP Thematic Issue “Molecules in Confined Space” “ … intricate chemistry of molecules taking place in the confined space of e.g. zeolites …” • Zeolites with their 3D network involving cages are archetypal structures • Early work (C.M. Zicovich- Wilson, A. Corma, P. Viruela, J.Phys.Chem., 98, 10863 (1993) • New concept: “electronic confinement”: density of the guest molecule orbitals suddenly drops to nearly zero when reaching the walls of the zeolite as a consequence of the shortrange repulsion with the delocalized electronic cloud of the lattice change is orbital energy levels •Hückel Theory ethylene HOMO-LUMO gap, and so the hardness, decreases if the molecule is spatially confined. c=c η LUMO HOMO η LUMO HOMO Pag. 30-9-2008 35
Page 1 and 2: DFT Reactivity Descriptors and Cata
Page 3 and 4: Outline 1. Robert Schoonheydt and t
Page 5 and 6: Pag. 30-9-2008 5
Page 7 and 8: Pag. 30-9-2008 7
Page 9 and 10: Pag. 30-9-2008 9
Page 11 and 12: 2. Chemical Concepts from DFT Funda
Page 13 and 14: Conceptual DFT (R.G. Parr, W. Yang,
Page 15 and 16: Identification of two first derivat
Page 17 and 18: • Ambiguity in the definition var
Page 19 and 20: Applications until now mostly on (g
Page 21 and 22: 3. Some applications of global and
Page 23 and 24: The Two Step Consecutive Mechanism
Page 25 and 26: • Rate Constant Evaluation • Tr
Page 27 and 28: • Local level • Softness indica
Page 29 and 30: 3.2 Lewis acid Catalysis: the role
Page 31 and 32: Transition States C m H 3Cb X 1 H 2
Page 33: Cyclic TS characterized by several
Page 37 and 38: Atoms • previous work (1992-2005)
Page 39 and 40: An atom test case: helium Radial De
Page 41 and 42: Ethylene: planar confinement • Sa
Page 43 and 44: A first try: an order of magnitude
Page 45 and 46: Epilogue: looking back at the 1979-
Page 47: 6. Acknowledgments Prof. Wilfried M

DFT Reactivity Descriptors and Catalysis - Vrije Universiteit Brussel

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