Free-radical kinetic model for homogeneous oxidation of methane to methanol

A free-radical reaction mechanism for homogeneous oxidation of methane to methanol was used to investigate the effect of oxygen concentration, residence time, and reaction temperature on the product distribution. The results from the simulation are compared with data for reactor feeds of 2.30-4.35% oxygen and 95.65-97.70% methane and pressure of 50 atm. Methanol selectivities decreased from 55% to 34% as the reaction temperature increased. Oxygen and methane conversions were 100% and approximately equal to the oxygen concentration in the feed, respectively. Helton's free-radical model with a change in the enhancement factors was used for the simulations. The enhancement factors were determined using several temperatures, oxygen conversions of 20-99%, and a residence time of 2 s. For 8- and 17-s residence times the model predicts the performance for the lowest temperature. A simulation is also presented, which suggests a method of operation to achieve methanol selectivities and yields of 70% and 7%, respectively.