| Autor: |
Son Nguyen, Vinh, H. Matus, Myrna, Thi Ngan, Vu, Tho Nguyen, Minh, A. Dixon, David |
| Zdroj: |
The Journal of Physical Chemistry - Part C; April 2008, Vol. 112 Issue: 14 p5662-5671, 10p |
| Abstrakt: |
Electronic structure calculations at the CCSD(T) level with the aug-cc-pVnZ and aug-cc-pV(nd)Z basis sets (n D, T, and Q) were employed to construct the potential energy surfaces for H2release from ammonia alane without and with the presence of alane (AlH3). In the AlH3NH3monomer, although the energy barrier for H2loss of ∼29 kcal/mol is comparable with the energy for Al−N bond cleavage (∼27 kcal/mol), kinetics calculations show that only the latter is important at 298 K. The calculated results demonstrate that alane can play the role of an efficient bifunctional catalyst for H2release from ammonia alane. The transition state for H2production from AlH3NH3AlH3is located 4.3 kcal/mol lower in energy than the separated reactants and 18.7 kcal/mol above the complex AlH3NH3···AlH3. A systematic comparison with the reaction pathways for H2loss from ammonia borane (BH3NH3) with AlH3or BH3as the catalyst shows that alane is a better catalyst than borane. The predicted kinetic rate constants for hydrogen elimination from ammonia alane with alane as the catalyst are k(298 K) 2.6 × 10-2s-1and k(400 K) 8.4 × 101s-1, including tunneling corrections. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
|
