载镍ZSM-5沸石的XPS研究Ⅰ氧化态NiZSM-5沸石

XPS STUDY OF NI-CONTAINING ZSM-5 ZEOLITES 1.Unrcduced Ni ZSM-5 Zeolites

本文借助ESCA技术研究了(?)交换法、浸溃法及机械混合法制备的载镍ZSM-5沸石的表面特性;并讨论了表面物种与催化活性的相关关系。

In the present paper, the surface characterization of NiZSM-5 zeolites in the redox cycle was studied by XPS. It was found that the Ni(Ⅱ) species in the surface layers of NiZSM-5 zeolites can be partially reduced to metallic nickel under the given condition. The degree of reduction of Ni(Ⅱ) species depended mainly on the forms of Ni(Ⅱ) species. Moreover, the metallic nickel particles formed by reduction of Ni(Ⅱ) species with hydrogen were unstable, which can be obviously reoxided by dry air at room temperature. It seems that the redox cycle is only partially reversible. The enrichment of element Ni in the surface layers was found. It was suggested that the treatment of NiZSM-5 zeolites with hydrogen at high temperature have two effects, of these, calcination at high temperature resulted in the diffusion of element; and the reduction with hydrogen caused the migration of Ni species.