The invention relates to a process for the preparation of a ketone and/or an aldehyde, comprising the steps of: a) forming a reaction mixture by bringing a starting ketone or a starting aldehyde or a mixture of a starting aldehyde and a starting ketone into the gaseous phase; b) bringing the reaction mixture in contact with a catalyst, said catalyst comprising silica, said silica having a purity higher than 95 wt.%, whereby the ketone and/or the aldehyde is/are formed and whereby the reaction conditions are such that the conversion of at least the understoichiometrically present starting compound(s) is at least 50%.