INFLUENCE OF PRETREATMENT CONDITIONS ON ACIDITY OF COBALT-BASED BIMETALLIC SYSTEMS IN NAY ZEOLITE

Co/NaY, Pt/NaY, Ru/NaY, Ru-Co/NaY and Pt-Co/NaY samples were pretreate d in different ways and their Bronsted and Lewis acidities were measur ed by means of pyridine adsorption and by double-bond isomerization of 1-butene. It is established that during nitrogen/hydrogen pretreatmen t small metal or bimetallic particles are formed and the system posses ses Bronsted and Lewis acidity, whereas by pretreatment in oxygen/hydr ogen only Lewis acidity is developed (large metal particles segregated to the zeolite surface). The difference is due to the formation of pr oton-metal adducts inside the zeolite supercage when nitrogen/hydrogen pretreatment is applied and this is ceased when oxygen/hydrogen pretr eatment is used. This is fully supported by the double-bond isomerizat ion of 1-butene to cis- and trans 2-butenes.