Partial Oxidation of Methane to Methanol by Using Molecular O2 on Pd2+ Catalyst: An Insight from Theory

The partial oxidation of methane to methanol using cationic Pd-2 dimers is investigated by employing density functional theory (DFT) method. We used B3PW91 functional for geometry optimization, and frequency calculations of all species involved in [Pd-2](+)+O-2+2CH(4) reaction. Furthermore, a density-fitting triple zeta valence with single-polarization (def2TZVP) is used in the calculation to determine the atomic orbitals of the atoms. We oxidized Pd-2(+) to [Pd2O2](+) using O-2 and performed possible partial oxidation of methane to methanol on [Pd2O2](+) and [Pd2O](+) and explored various intermediates and transition states on the potential energy surface (PES) diagram. From Potential Energy Surface (PES) analysis, it is found that the [Pd2O2](+) in doublet spin state multiplicity (SM=2) following radical mechanism is the more preferred pathway for methane to methanol conversion.