Abstract: KS-III-3 Нанокластеры – что дальше? Small pore solids such as zeolites and the MCMs can serve as hosts for nanoclusters, resulting in materials whose catalytic potential is enormous, but arguably as yet not fully exploited. The purpose of this paper is to present a brief survey of these materials and to describe a new variety of sulfur-containing nanoclusters. Alkali metal clusters in zeolites may have been the first to spark interest, followed by catalysts hoped to have petroleum processing potential, such as Pt-ZSM-5 and Pt-L. The platinum nanoclusters formed may be confined within the pores of the matrix, or may stretch or fracture it. The extent to which the electronic properties of the metallic clusters is modified by the matrix remains a matter of some controversy. The greatest boost to interest in nanoclusters in zeolites undoubtedly came from the discovery about ten years ago, by Iwamoto and others, of the success of Cu-ZSM-5 materials as decomposition catalysts for NOx, and for the selective catalytic reduction of NOx in the presence of excess oxygen (SCR). Much subsequent academic study has shown that the most active site for both of these reactions is probably a copper oxo-dimer. Turnover number studies by Moretti suggest that isolated copper ions may be wholly inactive for NOx decomposition, while work in our laboratory shows that dimers and other oxo-clusters are more active in the SCR reaction than isolated ions. More recently, iron containing zeolites have attracted interest, mainly due to their significant stability in the SCR reaction, and their ability to activate N2O. We have shown that when Fe-ZSM-5 is prepared by impregnation from aqueous solution, the result is small nanoclusters such as Fe4O4• We now report that these materials can be almost fully converted to their sulfur analogues by exposure to H2S. We have also shown that the sulfided Fe-ZSM-5 materials can act as catalysts for the hydration of acetonitrile to acrylamide, a reaction which is also catalysed by iron-sulfur containing enzymes. If time permits, the prospects for nanoclusters containing electronegative elements other than oxygen and sulfur will be examined. Секция: Секция III: Methods of investigation of the mechanisms of catalytic reactions

Cite: Joyner R.W. , Stockenhuber M. , Tkachenko O.K.
Nanoclusters - where next?
VI Russian Conference on Catalytic Reaction Mechanisms 01-05 Oct 2002