SURFACE-MODIFIED BIMETALLIC CATALYSTS - PREPARATION, CHARACTERIZATION, AND APPLICATIONS

The basic principles of the preparation of surface modified catalysts, the problems of characterization of the metals, and models describing their active surface are considered. The characteristics of surface transformations and the distribution of modifying elements are defined by the ratio of reactivity/diffusivity under the conditions of the surface modification. The state of the metals (Ni, Pd, Cr, Si, Sn) is characterized by using electron spectroscopy for chemical analysis, laser microprobe analysis, extended X-ray absorption fine structure, Mossbauer spectroscopy as well as magnetization and chemisorption. The high activity, selectivity, and tolerance to common poisons are demonstrated for catalysts based on supported nickel and palladium in hydrogenation and dehydrogenation reactions.