GAS-PHASE REACTIVITY OF SUBNANOMETRIC BARIUM CLUSTERS WITH METHANOL UNDER THERMALIZATION CONDITIONS

Basic oxides play a crucial role in various industrial catalytic processes due to their ability to activate the O-H, C-H, and C-O bonds of simple alcohols on the M²?-O²? catalytic center, which consists of a Lewis acid and a Brønsted base. This study investigated the mechanisms at the molecular level of gas-phase reactions between methanol and cationic subnanometric barium-containing clusters, namely, Ba??, Ba(OH)?, and Ba(H?O)??, which are used as model systems for the active sites of heterogeneous basic oxide catalysts. The experiments were performed under thermalization conditions at 291.5 K on a new experimental setup based on a Smalley cluster source coupled to a fast flow reactor, which is enclosed in a molecular beam apparatus with time-of-flight mass spectrometry detection. Complementary theoretical calculations at the density functional theory level were carried out on the various relevant reactions to aid in the interpretation of the experiments. The joint experimental and theoretical results suggest that the adsorptive behavior of basic oxides like BaO towards methanol and water molecules can already be evidenced in these small clusters, reinforcing their role as potential active sites in heterogeneous basic catalysts.