NEW STRATEGY OF CREATION OF LOCAL CATALYTIC SITES IN DEFINITE ELECTRONIC AND COORDINATION STATES

Atomic-scale engineering of catalytic functions of isolated redox site s in confined environments of zeolitic channels is proposed as a new a pproach to the investigation of structure-properties relationship in h eterogeneous 'biomimetic' catalysis. It is shown that the design of su ch catalysts, on the base of high-silica zeolites, containing isolated transition-metal cations as active redox sites, may present promising opportunities for creation of new types of contacts from a practical point of view. A detailed analysis of transition-metal cation incorpor ation into high-silica zeolites by either conventional or solid-state exchange is given. Stabilization of one or several transition-metal io ns by matrices of high-silica zeolites (mainly H-ZSM-5) is discussed. The influence of different factors on the processes of cationic-specie s stabilization is analyzed. These data are correlated with the result s of catalytic testing in reactions of total oxidation of hydrocarbons (HC), direct decomposition of NOx and SCR of NOx by HC. The relations hip between catalytic activity and selectivity of cationic sites and t heir coordination and electronic state, regulated by either thermal tr eatment or introduction of different anionic ligands, is analyzed.