EFFECT OF THE ADDITION OF ALKALI-METALS ON THE METALLIC PHASE OF PT AL2O3 CATALYSTS/

The effect of the addition of alkali metals to Pt/Al2O3 catalysts for dehydrogenation of paraffins was studied. Results can be interpreted i n terms of different effects. Thus, the addition of alkali metals prod uces a poisoning of the acid sites of the alumina support and a modifi cation of the characteristics of the metallic phase. The latter effect involves not only an increase of the Pt particles size, but also an e lectronic modification of the metallic phase. These two effects are mo re marked with alkali metals with higher ionic radius, such as K.