The aim of our work was to examine halogens as the catalysts of methane esterification in oleum. The experiments were performed at 160 C in oleum containing 25 wt% SO3, at methane pressure of 4.27 MPa. A mathematical model including the impact of the catalyst concentration on the initial reaction rate was proposed. The solubility of elemental iodine in 25 wt% oleum at 160 C was found to be ca. 17 mmol/dm3.