The selective deposition of Fe species inside ZSM-5 for the oxidation of cyclohexane to cyclohexanone

摘要

The design of efficient iron-based catalysts remains a great challenge for selective cyclohexane oxidation to cyclohexanone under mild conditions.Because of the complex distribution of iron location on the support,the selectivity is always low.Here,we report a general strategy to selectively deposit highly-dispersed FeO_(x) into the micropore of ZSM-5 by atomic layer deposition(ALD).The framework of ZSM-5 and the Bronsted acid sites are intact during ALD,and the Fe species are selectively deposited onto the defect and Lewis acid sites of ZSM-5.Besides,more Fe–O–Si bonds are formed over FeO_(x)/ZSM-5 with a low loading of Fe,while FeO_(x) nanoparticles are generated at high Fe loading.They cannot be realized by the traditional solution method.The obtained FeO_(x)/ZSM-5 catalysts perform high selectivity of cyclohexanone(92%–97%),and ALD cycle numbers of FeO_(x) control the activity.Compared with the Fe nanoparticles,the Fe–O–Si species performs higher turnover frequency and stability in the oxidation reaction.