A reaction model for the conversion of methane to C1-oxygenates (methanol and formaldehyde) with NO x (x = 1, 2) has been proposed theoretically using the ab initio molecular orbital method. The geometric and electronic structures for all the present molecules have been calculated by means of the MP2 (frozen core)/6-311++G(2d,p) level of theory. On the basis of the optimized structures, the single point calculations of the energies are carried out at the CCSD(T) level with the same basis sets. Through the theoretical analysis of the simplified CH4−NO x system instead of the experimental CH4−O2−NO system, we found the possible reaction path leading to C1-oxygenates within all the barriers of less than 40 kcal/mol via CH3O at 800 K. NO2 has a higher activity for the hydrogen abstraction from methane than NO and O2, though the calculated rate constants at 800 K indicate that this reaction is the rate-determining step in the conversion of methane to C1-oxygenates. It is also found that increasing the concentration of NO promotes the yield of formaldehyde with the decreasing formation of methanol, which is consistent with recent experimental results in the CH4−O2−NO system.

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A reaction model for methane oxidation on a reduced SnO 110 crystal 2 surface has been proposed theoretically using a point-charge model. The geometric and electronic structures for all the molecules along the four reaction channels have been Ž . calculated by means of the MP2r6-311qqG 2d, p level of theory. On the basis of the optimized geometries in the gas phase, the single-point calculations of the energies on the point-charge model are carried out. The results indicate that the energetically favorable reaction paths to yield methanol and formaldehyde on the reduced SnO surface are via 2 the reactant complex CH O-H O and via the secondary production of methanol 3 2 oxidation, respectively. It is also found that CH O y is a stable anion on the surface due 3 to having the high barriers of about 70 kcalrmol in both hydrogen abstraction with O y and thermal decomposition, which is favorable to yield methanol and also is consistent Ž . with X-ray photoelectron spectroscopy XPS experiments.