BASF Distinguished Lecture: Enrique Iglesia
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Abstract: The properties of the chemical species that act as intermediates and transition states and of the binding sites that stabilize them act in concert to determine reactivity and selectivity for reactions catalyzed by surfaces. The dynamics of this interplay are specifically addressed here for acid-base and oxidation catalysis on oxides, but with illustrative extensions to other types of solids. Experiment and theory are combined to demonstrate the sites required and the mechanisms of surface catalysis at the level of atomic identity and connectivity in solids and of the kinetic relevance of specific elementary steps on surfaces faithful, in structure and function, to those used in practice. On solid acids, their deprotonation energies and the proton affinity of gaseous analogs of the relevant transition states combine to determine reactivity, as well as the role of acid strength, in acid catalysis, because such transformations require proton transfer and cation-anion pairs at transition states. Aerobic oxidations on redox-active oxides depend on the dynamics of elementary steps that cause the reduction of metal centers in oxides through H-abstraction from C-H bonds in reactants. The late transition states that mediate such steps consist of interacting di-radical pairs that contain a nearly-formed O-H bond and a nearly-cleaved C-H bond, thus making H-addition energies at lattice O-atoms in oxides and C-H bond dissociation energies in the organic substrates the respective binding site and molecular properties relevant for reactivity and selectivity. The environment that surrounds the binding site complements such binding sites through solvation effects that can preferentially stabilize specific reactive intermediates and transition states through weak concerted van der Waals or H-bonding interactions. Such “outer sphere” stabilization can be conferred by confinement effects mediated by voids of molecular dimensions, but also by dense phases, such as liquids or dense adlayers of bound species, near the point of binding. Taken together, the properties of binding sites and of their local environment confer upon solids their remarkable diversity in channeling chemical reactivity towards specific paths in the practice of surface catalysis. Acting in concert, a binding point and a local environment define the catalytic active site; theory, spectroscopy, kinetic and isotopic probes, and accurate assessments of the structure of inorganic architectures have brought us closer to the purposeful design of such active sites.
Biography: Enrique Iglesia is the Theodore Vermeulen Chair in Chemical Engineering and the University of California at Berkeley, and a Laboratory Fellow at Pacific Northwest National Laboratory. He holds degrees in chemical engineering from Princeton (B.S.) and Stanford (Ph.D.) and doctor honoris causa from the Universidad Politecnica de Valencia and the Technical University of Munich. He joined the Berkeley faculty in 1993 after research and management positions at the Exxon Corporate Research Labs. Enrique Iglesia has been elected to the National Academy of Engineering, the American Academy of Arts and Sciences, and the National Academy of Inventors. He is the former Editor-in-Chief at the Journal of Catalysis, a Fellow of AIChE and ACS, and an Honorary Fellow of the Chinese Chemical Society. He has received the Murphree, Somorjai and Olah Awards from the American Chemical Society, the Alpha Chi Sigma, Wilhelm, and Walker Awards from the American Institute of Chemical Engineers, and the Emmett, Boudart, Burwell, and Distinguished Service Awards from the Catalysis Society. He has been named the Gault Lecturer by the European Federation of Catalysis Societies and the Cross-Canada Lecturer by the Chemical Institute of Canada. He has received the ENI Prize for his research on energy carriers and conversion, the Kozo Tanabe Prize in Acid-Base Catalysis, and the International Natural Gas Conversion Award. His dedication to teaching has been recognized with the Donald Sterling Noyce Teaching Prize, the highest teaching recognition in the physical sciences at Berkeley, and with several College of Chemistry teaching awards. He has co-authored more than 350 publications and 40 U.S. patents. The Iglesia research group addresses conceptual and practical challenges in heterogeneous catalysis in areas relevant to energy, to the synthesis of chemicals and fuels, and to the prevention and abatement of environmental impacts of energy conversion and use by combining kinetic, spectroscopic, isotopic and theoretical methods with the synthesis of inorganic solids with novel architectures.