DFT studies on dehydrogenation mechanism of methane activated by gas-phase niobium cations
- 化学化工－已发表论文 
Density functional calculations were employed to investigate the quintet, triplet and singlet energies of methane direct- or inserted- dehydrogenation by gas-phase Nb+ as well as the influence of spin-inversion on the reaction mechanism. The results indicate that the inserted-dehydrogenation mechanism is more favorable than the direct-dehydrogenation. The minimum energy reaction path is thought to be related to the spin flip from 2S + 1 = 5 to 3, which decreases the activation barrier of methane-dehydrogenation significantly. The formed intermediate HNbCH3+ is transformed into (H-2) NbCH2+ via a four-centered transition state, and the final product is the triplet NbCH2+ + H-2. The rate determined step of reaction is the dehydrogenation of (H-2) NbCH2+. In addition, the reactivities of gas-phase group V cations (V+, Nb+ and Ta+) towards the de-hydrogenation of methane were also discussed.