Surface characterization of Li-modified platinum/tin catalysts for isobutane dehydrogenation

The superficial properties of different Pt/y-Al2O3 catalysts, modified by t he addition of tin and/or lithium, were studied by X-ray photoelectron spec troscopy (XPS), scanning electron microscopy, BET, and 2-propanol transform ation. The results obtained were correlated with the behavior of the cataly sts in applied reactions such as the dehydrogenation of isobutane. To obtai n very well defined bimetallic superficial phases; tin was introduced by me ans of surface organometallic chemistry on metals techniques and the nature of the bimetallic-active sites so obtained was compared with the ones prep ared by conventional procedures. XPS measurements indicate that tin is pres ent in both zeroth valent and oxidized states. The addition procedure of bo th tin and lithium has a marked influence on the characteristics of the sur face of the catalysts. The order in which lithium is added generates solids having different properties in relation to texture, dispersion, and cataly tic behavior, for both Pt and PtSn systems.