EFFECT OF ADDED COPPER ON THE STATE AND CATALYTIC PROPERTIES OF PLATINIZED ZINC ALUMINUM SPINEL CATALYSTS FOR THE DEHYDROGENATION OF LOWER PARAFFINS

A study has been made of the genesis of phase composition of Pt-Cu/ZnAl2O4 catalysts, prepared by either simultaneous or successive impregnation. It has been shown that in the course of oxidative treatment of the catalysts at high temperatures, platinum-copper oxide phases are formed. The degree of interaction of the components depends on the catalyst preparation method and is the greatest when the samples are prepared by simultaneous impregnation. Stabilization of platinum during the stage of oxidative activation in the form of CuPt3O6 and Cu1-xPtxO phases results in a higher degree of dispersity of the Pt-Cu solid solutions that are formed during the subsequent reduction. It has been established that surface and volume segregation of the Pt-Cu alloys takes place when the conditions of the n-butane dehydrogenation process are changed. Depending on the Cu/Pt ratio in the Pt-Cu solid solutions, the fcc structure of copper may act as a promoter or a catalytic poison in relation to the platinum.