Partial oxidation of methane to formaldehyde and methanol with molecular oxygen has been investigated. The reaction was carried out at the atmospheric pressure at 350-650 degreesC. ZSM-5 molecular sieves with the iron and silicon tetrahedral framework were used as catalysts. The Si/Fe molar ratio was 45, 34 and 22. Fe-ZSM-5 was applied both in the sodium and hydrogen form. Higher values of methane conversion were acquired when Fe-HZSM-5 (31.51% for Si/Fe = 22) was used. Fe-NaZSM-5 resulted in procuring higher values of the selectivity of the oxidation of methane to methanol (74% for Si/Fe = 45). It was found that increasing the temperature as well as extending the contact time increases the conversion of methane to methanol and at the same time lowers the value of the selectivity of the oxidation of methane to methanol. The influence of the iron content on the kinetics of the carried out reactions was discussed. (C) 2004 Elsevier B.V. All rights reserved.