Experimental and theoretical studies of the reaction between cationic vanadium oxide clusters and acetylene

The time of flight mass spectrometer coupled with a laser ablation/supersonic expansion cluster source and a fast flow reactor was adopted to study the reactivity of cationic vanadium oxide clusters (VmOn+) toward acetylene (C2H2) molecules under gas phase (P, similar to 1.14 kPa), under near room temperature (T, similar to 350 K) conditions. Association products, VmOnC2H2+ (m,n = 2,4; 2,6; 3,7-8; 4,9-11; 5,12-13; 6,13-16, and 7,17), are observed. The oxidation of C2H2 by (V2O5)(n)(+)(n = 1-3) is experimentally identified. The reactivity of (V2O5)(n)(+) decreases as n increases. Density functional theory (DFT) calculations were carried out to interpret the reaction mechanisms. The DFT results indicate that a terminal oxygen atom from V2O5+ can transfer overall barrierlessly to C2H2 at room temperature, which is in agreement with the experimental observation. Other experimental results such as the observation of V2O6C2H2+ and non-observation of V2O7,8C2H2+ in the experiments are also well interpreted based on the DFT calculations. The reactivity of vanadium oxide clusters toward acetylene and other hydrocarbons may be considered in identifying molecular level mechanisms for related heterogeneous catalysis.