C=C Bond Cleavage on Neutral VO3(V2O5)(n) Clusters

摘要

The reactions of neutral vanadium oxide clusters with alkenes (ethylene, propylene, 1-butene, and 1,3-butadiene) are investigated by experiments and density function theory (DFT) calculations. Single photon ionization through extreme ultraviolet radiation (EUV, 46.9 nm, 26.5 eV) is used to detect neutral cluster distributions and reaction products. In the experiments, we observe products (V2O5)(n)VO2CH2, (V2O5)(n)VO2C2H4, (V2O5)(n)VO2C3H4, and (V2O5)(n)VO2C3H6, for neural VmOn clusters in reactions with C2H4, C3H6, C4H6, and C4H8, respectively. The observation of these products indicates that the C=C bonds of alkenes can be broken on neutral oxygen rich vanadium oxide clusters with the general structure VO3(V2O5)(n=0,1,2...). DFT calculations demonstrate that the reaction VO3 + C3H6 -> VO2C2H4 + H2CO is thermodynamically favorable and overall barrierless at room temperature. They also provide a mechanistic explanation for the general reaction in which the C=C double bond of alkenes is broken on VO3(V2O5)(n=0,1,2...) clusters. A catalytic cycle for alkene oxidation on vanadium oxide is suggested based on our experimental and theoretical investigations. The reactions of VmOn with C6H6 and C2F4 are also investigated by experiments. The products VO2(V2O5)(n)C6H4 are observed for dehydration reactions between VmOn clusters and CA. No product is detected for VmOn clusters reacting with C2F4. The mechanisms of the reactions between VO3 and C2F4/C6H6 are also investigated by calculations at the B3LYP/TZVP level.