EXPERIMENTAL AND MODELING STUDY OF THE SELECTIVE HOMOGENEOUS GAS-PHASE OXIDATION OF METHANE TO METHANOL

The partial oxidation of CH4 to CH3OH with air has been investigated experimentally and theoretically. Experimentally, the homogeneous gas phase reaction was studied at pressures in the range 40 x 10(5)-60 x 10(5) Pa, temperatures in the range 723-823 K, and O2 concentrations in the range 2.6-4.4% relative to CH4. CH3OH selectivities between 35 and 55% were obtained at low conversions, 1.2-2.6%. A kinetic model, based on 61 elementary reactions, was able to reproduce experimental observations, indicating that only moderate selectivities to CH3OH (50-65%) are obtainable at low CH4 conversion (<4%). The model is used to investigate an extended span of temperatures, pressures, and O2 concentrations in search of favorable conditions for CH3OH formation. The model predicts CH3OH formation to be favored by high pressure, moderate temperature 673-723 K, and low O2 concentrations 2-4%. The predicted effects are discussed and illustrated in a mechanistic perspective.