Quantum chemical and vibrational investigation of sodium exchanged gamma-alumina surfaces.
The sodium cation is well known as an efficient poison of gamma-alumina surface acidity. This poisoning effect has been revealed both by characterization methods and catalytic tests. In this work, we propose an accurate model of sodium exchanged gamma-alumina surfaces. On realistic models of hydroxylated gamma-alumina surfaces, the location of sodium cation is determined by the use of density functional theory (DFT) methods. For the (100) and (110) surfaces of gamma-alumina, the sodium cation is found in a solvated state within an inner solvation sphere complex. Its coordination sphere is constituted by O-mu(2), O-mu(3) and HO-mu(1) surface groups. The stretching frequency of these HO-mu(1) groups is shifted, leading to the appearance of a new band predicted and observed at about 3754 cm(-1) on the IR spectrum.
Digne
Mathieu
M
Direction Physique et Analyse, IFP, BP 3, 69390 Vernaison, France. mathieu.digne@ifp.fr
Raybaud
Pascal
P
Sautet
Philippe
P
Guillaume
Denis
D
Toulhoat
Hervé
H
D000537:Aluminum Oxide / Q000737:chemistry*; D002384:Catalysis; D008958:Models, Molecular; D008968:Molecular Conformation; D010087:Oxides / Q000737:chemistry*; D011789:Quantum Theory; D012964:Sodium / Q000737:chemistry*; D017670:Sodium Compounds / Q000737:chemistry*; D013499:Surface Properties; D014732:Vibration; D014867:Water
D010087:Oxides; D017670:Sodium Compounds; D014867:Water; C096707:sodium oxide; D012964:Sodium; D000537:Aluminum Oxide