Elucidating the Role of Basic Promoters in Transition Metal Catalysis

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Abstract- Davis - 9729812 Prof. Robert J. Davis of the University of Virginia will investigate the mechanism of promotion of supported Ru metal catalysts for the ammonia synthesis reaction, by alkaline-earth elements and rare-earth oxides. This proposal is of relevance to the science of catalysis and of wider relevance to the chemical industry, in particular that concerned with agrochemical and commodity chemical production. Ammonia synthesis over base-promoted Ru catalysts may lead to reduced consumption of process energy and consequently less environmental impact. Basic promoters for Ru metal will include alkali and alkaline-earth as well as rare-earth oxides: K, Ba, Ca, and oxides of Ce and Pr, for example. Supports will include zeolites, other oxides, and carbon. The proposal objectives are to determine the atomic structure of Ru clusters by EXAFS and their electronic structure by XANES and IR spectroscopy of adsorbed N2. The promoter distribution in the vicinity of, and on Ru clusters over non-zeolitic supports, will be examined by analytical HRTEM, and correlated with ethane hydrogenolysis activity. The density of active sites will be determined with TPD of N2 and H2 chemisorption, and their intrinsic activity by N2 activation and by NH3 synthesis at atmospheric and at 20-bar pressure. The surface coverage by various reactive intermediates will be investigated by means of steady state isotopic transient kinetics.