DFT Reactivity Descriptors and Catalysis - Vrije Universiteit Brussel

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The Direct Mechanism • Methanol and benzene coadsorb on the acid site • Zeolite proton moves to methanol; formation of water; methylgroup of methanol moves to benzene transferring a proton to the zeolite Si2 Cb Hb O2 Al Cm Om Ha Hm O3 Si3 TS2 O4 acid zeolite + methanol (g) + benzene (g) acid zeolite + toluene (g) 84.25 40.21 + water (g) R2 194.87 27.28 71.32 P2 Si2 O2 Cb Hb Ha O1 Al O4 Om O3 Cm Hm Si3 Si2 Cb Hb O2 O4 Cm Ha Om Hm Al O1 O3 Si1 Si3 Pag. 30-9-2008 24
• Rate Constant Evaluation • Transition State Theory k r k T h Q Q ‡ B = ⋅ ⋅ ∏ i i e −E / bar RT • Q ‡ ,Q i …: partition functions in rigid rotor, harmonic oscillator approximation • E bar : activation barrier Example: one step reaction, A and B reacting simultaneously with an acidic zeolite HZ: reaction rate per acid proton ‡ ( Q Q Q ) k T k ( ) − r = N AvV × ⋅e h Q Q Q Q Q Q Q Q Q 2 B v r t TS − E / RT ( ) ( ) ( ) v r t A v r t B v r t HZ bar Arrhenius type analysis E A , A, ∆S Act • Tested via H/D Exchange reaction of methane: 3T cluster model fair agreement between theoretical and experimental activation energy A.M. Vos, F.De Proft, R.A.Schoonheydt, P. Geerlings, Chem.Comm., 1108 (2001) Pag. 30-9-2008 25
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: The Two Step Consecutive Mechanism
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 and 34: Cyclic TS characterized by several
Page 35 and 36: 4. Towards the Inclusion of Confine
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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