Oxidative conversion of C1–C3 alkanes by vanadium oxide catalysts. DFT results and their accuracy^†

Elementary steps in the oxidative conversion of methane, ethane, and propane by supported vanadium oxide species are studied by density functional theory, specifically B3LYP. Two models are adopted, namely OV(OH)₃ and OVSi₇O₁₂H₇, which yield similar energy profiles. The initial and rate-determining step is hydrogen abstraction. Within the C1–C3 series, energy barriers and reaction energies follow the same trend as the CH bond strength in the different alkanes. For methane, only methanol formation is possible whereas for ethane and propane, oxidative dehydrogenation yields the corresponding alkenes. Single point CCSD(T)/TZVP calculations are used to assess the B3LYP error. For the barrier of the initial hydrogen abstraction the B3LYP error is larger than usual, −40 to −60 kJ/mol. With the non-hybrid BP86 and PBE functionals even larger errors occur and the potential energy surface is qualitatively different. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008