Calculations of Methane to Methanol Conversion Using a Nickel Catalyst and Ozone

Jennifer E. Ruliffson, Melanie White, Kai Lister, Joshua J. Melko

Department of Chemistry, University of North Florida, Jacksonville FL 32206

Methane is an important agricultural product that must be converted to methanol for transport due to economic and safety concerns. Direct conversion using a strong oxidant (e.g. ozone) is restricted kinetically and thermodynamically, and requires a catalyst such as nickel. Here we investigate the catalytic cycle formed by Ni⁺ + O₃ → NiO⁺ + O₂ ; NiO⁺ + CH₄ → CH₃OH + Ni⁺, which represents a single-site catalyst. Using Gaussian 09 software, we explore computational methods to characterize the reaction pathways in conjunction with experimentally determined products for this cycle. After comparing results of candidate methods to established literature values, the functional B3LYP with the SDD-gd3bj basis set was selected in addition to the functional M06 with the 6-311G+d,p basis set. For the initial reaction of nickel with ozone, the calculated pathways and experimental results concur that NiO⁺ and O₂ are the most prevalent products, and calculated kinetic barriers agree with the 100 percent reaction efficiency observed in experiment. For the reaction of NiO⁺ with CH₄, a submerged barrier and spin crossings are found that limit the reaction efficiency, in agreement with the experimentally determined low rate constant.