Formic acid is at least partly removed from an aqueous solution comprising formic acid, cyclohexanone and cyclohexanol by decomposition over certain decomposition catalysts.The method is preferably used for processing reaction products from the oxidation of cyclohexane and comprises: (i) extracting a product gas mixture obtained in the oxidation of cyclohexane with an aqueous scrubbing liquid, (ii) separating the aqueous solution obtained in (i) by distillation into an aqueous solution comprising formic acid, cyclohexanone and cyclohexanol together with further minor organic components and a carboxylic acid mixture (iii) removing the formic acid at least partially from the aqueous solution obtained in (ii) by decomposition, and (iv) further processing the aqueous solution obtained in (iii) to give epsilon-caprolactam, or using the aqueous solution obtained in (iii) as scrubbing liquid in (i).