Theoretical study of small clusters Au 3-4 on Au/SAPO-11 catalysts and their interactions with CO

Quantum chemistry calculations were done, using the ONIOM2 methodology at two different levels of calculation, B3LYP for the high level and UFF for the low level. These calculations were performed on Au₃/SAPO-11, Au₄/SAPO-11, CO-Au₃/SAPO-11 and CO-Au₄/SAPO-11 aggregates to analyze the geometries of small clusters of Au₃ and Au₄ on SAPO-11 support. Au₃ cluster present a triangle structure in Au₃/SAPO-11. Au₄ cluster shows a “Y shaped” structure in Au₄/SAPO-11. Au₄ as a rhombus structure is also studied but it is an unstable intermediate to the “Y shaped” structure. The CO interaction with Au₃ and Au₄/SAPO-11 is studied, this CO adsorption is different from reported in the literature. The formation energy ΔE_F of the aggregates and the CO adsorption energy ΔE_ads on them are presented.