This award supports Gary L. Haller of the Department of Chemical Engineering, Yale University, in a research collaboration with Johannes A. Lercher, Institute for Physical Chemistry, Technical University of Vienna, Austria. These scientists share an interest in the surface chemistry of bimetallic catalysts, particularly platinum/nickel and platinum/cobalt which vary significantly in their catalytic and other chemical properties. The goal of their collaborative research is to understand the role of support effects on stabilization of non-zero valent metal species and on hydrogen absorption-desorption equilibrium. Several supports will be used. Catalysts will be characterized by chemical methods and by physical methods such as x-ray diffraction, extended x-ray absorption fine structure (EXAFS) analysis, time resolved Fourier transform infrared (FTIR) spectroscopy, etc. The rates of hydrogen absorption/desorption, the equilibrium isotherm and several hydrogenation reactions will be used as chemical probes. The collaborative arrangement expedites this work by bringing to bear complementary expertise in physical characterization (EXAFS on the US side and time resolved FTIR spectroscopy on the Austrian side) as well as a division of labor in carrying out different reaction studies on the same catalysts in the two laboratories. Although transition metals are among the most frequently used catalysts for hydrogenation reactions, the reasons for their high activity and for particular selectivities in hydrogenation of more complex organic molecules are, at best, only qualitatively understood. Numerous concepts have been proposed to explain their selectivity, including work carried out independently by these collaborating scientists which showed that support effects on hydrogen absorption equilibrium and the presence of non-zero valent metal sites may greatly affect the selectivity of hydrogenation reactions. One of the objectives of the joint research is to establish the relative importance of these two factors. Understanding and manipulating these properties may lead to significant improvements in the activity and selectivity of the hydrogenation reactions.
