Adsorption microcalorimetry is used to study the surface thermodynamics of supported platinum and platinum/tin catalysts for reactions of importance to the reformulation of gasoline, specifically dehydrogenation and isomerization of light paraffins. Probe molecules are selected to study the chemical bonding properties of the surface for adsorbates relevant to the catalytic reactions of interest. The enthalpic and entropic changes associated with the interactions of these probe molecules with surfaces are measured. The surface thermodynamic data are compared with reaction kinetic data from steady-state studies, isotopic tracing, and temperature-programed desorption to explore correlations between surface thermodynamics and surface kinetics. Relationships between surface thermodynamics and catalyst structure are also examined. This project is a major contribution to the data base on surface thermodynamics. It also provides a good test of the utility of such data in catalyst design. The test system employed has immediate implications in meeting the new standards under the Clean Air Act.
