Study of nature of the factors determining activity, stability and selectivity of zeolite catalyst

Abstract

The dependences of catalytic properties of zeolites of type Y, mordenite, highly siliceous zeolite (ZSM) in cracking of n-octane and synthesis of hydrocarbons from methanol (activity and stability of action) on the concentration and state of hydroxyl groups, aluminium atoms, and on the coordination environment of silicon atoms in zeolites have been investigated. The state of active centres was studied by 2Al and 29Si n.m.r., and i.r. spectroscopy. Activity, stability and selectivity of zeolites are concluded to be dependent on the concentration of groups having more than one aluminium atom in the second coordination sphere of silicon atom, one of which can be in the cation position. Concerted (associative) effect of the proton-donor and Lewis centres on reagent is proposed. Lewis centres may have aluminium atoms in the cation position outside the framework.