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  • Title: Quantum chemical and vibrational investigation of sodium exchanged gamma-alumina surfaces.
    Author: Digne M, Raybaud P, Sautet P, Guillaume D, Toulhoat H.
    Journal: Phys Chem Chem Phys; 2007 May 28; 9(20):2577-82. PubMed ID: 17508090.
    Abstract:
    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.
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