Redox Behavior of Fe-Mo-O Catalysts Studied by Ultrarapid In Situ Diffraction

摘要

The term Fe-Mo-O is used to denote a mixed-phase catalyst system as used, for example, in the production of formaldehyde, which is an important building block for complex chemicals in many consumer products. Almost all formaldehyde is manufactured by either: 1) dehydrogenation of a methanol-rich air mixture over a silver catalyst or 2) direct oxidation of methanol over a Fe-Mo-O-based catalyst.[1], [2a] The latter process is advantageous in that the exothermic reaction can be carried out at comparatively lower temperatures, typically 375-350 ?C, and the catalyst offers comparatively higher activity and selectivity.[2b] The mechanism is assumed to follow a Mars/van Krevelen like process of oxidative dehydrogenation of hydrocarbons and has been demonstrated for an industrial Fe-Cr-Mo-O preparation.[3] Methanol oxidation proceeds with a partial reduction of the active iron molybdate Fe2(MoO4)3 phase [Eq. (1)], followed by catalyst regeneration:[4], [5]