The present invention relates to novel uses of stable inorganic peroxoacids as catalysts in the preparation of alkanesulfonic acids from alkanes and sulfur trioxide, methods for the production of alkanesulfonic acids employing said catalysts as well as reaction mixtures comprising said catalysts. The invention particularly relates to the production of methanesulfonic acid from methane and sulfur trioxide employing stable inorganic peroxoacids as catalysts.