Quantum study of the active sites of the gamma-alumina surface: chemisorption and adsorption of water, hydrogen sulfide and carbon monoxide on aluminum and oxygen sites

In this work, we have performed quantum calculations, using cluster models, in order to study the reactivity of the aluminum and oxygen sites of the g amma-alumina surface. Water, hydrogen sulfide and carbon monoxide molecules are employed as the test molecules for our cluster models. It is found tha t the tricoordinated aluminum sites of the surface are the dissociative sit es for the water and the hydrogen sulfide molecules. The tetracoordinated a luminum sites are the non-dissociative adsorption sites for the water molec ule, whereas they are the dissociative sites for the hydrogen sulfide molec ule. The pentacoordinated aluminum sites are the non-dissociative sites for the water and the hydrogen sulfide molecules. On the aluminum sites, carbo n monoxide is preferentially adsorbed via its carbon atom. In contrast to t he aluminum sites, the oxygen sites of the alumina surface are not adsorpti on sites for water, hydrogen sulfide and carbon monoxide molecules. (C) 200 0 Elsevier Science B.V. All rights reserved.