Methane oxidation to methyl bisulfate at ambient pressure in absorption reactor packed with glass balls in presence of iodine as a catalyst was investigated. The process was performed at temperature 120-130 degrees C, sulfur trioxide concentration in oleum 16-25 wt.%, catalyst concentration 0.008-0.024 mol dm(-3), methane flow: 8.69 cm(3) min(-1). The optimal conditions for high ester concentration were defined. (C) 2011 Elsevier B.V. All rights reserved.