ÃÛÌÇÖ±²¥

ChBE Patten Distinguished Lecturer
Seminar: Binding Sites and their Environment in Surface Catalysis

Speaker: Enrique Iglesia, Distinguished Professor and Theodore Vermeulen Chair in Chemical Engineering, University of California, Berkeley; Laboratory Fellow – Pacific Northwest National Laboratory

Host: Will Medlin

Seminar Abstract
The properties of molecular species that act as intermediates and transition states and of the surface sites that bind them act in concert to select reaction channels in chemical transformations mediated by surfaces. In acid-base and oxidation catalysis on oxides, theory and experiments have uncovered unprecedented details about site requirements and mechanisms, at the level of local architectures and elementary steps, respectively. On acids, the deprotonation energy of a solid and the proton affinity of the relevant analogs of transition states determine reactivity and selectivity, because such chemistries involve proton transfer and ion-pairs at transition states. Oxidation cycles on redox-active oxides occur via elementary steps reduce metal centers via H-abstraction from C-H bonds in reactants.Ìý The relevant transition states involve bound di-radical pairs with O-H and C-H bonds that are nearly formed and cleaved, respectively, thus making the energies of H-binding at surface O-atoms and of C-H homolysis the relevant surface and molecular descriptors of oxidation reactivity.Ìý In both types of reactions, more accurate descriptions, however, require assessments of how molecular species and sites interact and delocalize electron density in stabilizing intermediates and transition states, specifically ion-pairs and di-radicals in acid and oxidation catalysis, respectively. The environments that surround the active sites complement theirÌý binding properties through solvation effects that can stabilize specific bound intermediates and transition states through weak concerted van der Waals or H-bonding interactions.Ìý Such stabilization is particularly evident when sites reside within inorganic voids of molecular dimensions or exist in contact with dense phases, such as liquids or dense adlayers. These inner and outer sphere effects on reactivity and the fidelity brought forth by solids with well-defined atomic architectures are bringing us closer to the purposeful design of catalytic surfaces.

Biosketch
Enrique Iglesia is a distinguished professor and the Theodore Vermeulen Chair in Chemical Engineering at the University of California, Berkeley and a laboratory fellow at Pacific Northwest National Laboratory. He holds degrees from Princeton and Stanford and doctor honoris causa from the Universidad Politecnica de Valencia and the Technical University of Munich His research addresses the synthesis and the structural and functional characterization of porous inorganic solids as catalysts that enable the efficient production and use of energy carriers and chemicals and the mitigation of their environmental footprint. He is a member of the National Academy of Engineering, the American Academy of Arts and Sciences, the National Academy of InventorsÌýand the Real Academia de Ciencias (Spain). His research has been recognized by the American Chemical Society (ACS) with the Olah, Somorjai, and Murphree awards, by the American Institute of Chemical Engineering (AIChE) with the Wilhelm, Alpha Chi Sigma, and Walker awards, and by chemical and catalysis societies in North America and Europe with the Emmett, Burwell, BoudartÌýand Distinguished Service awards, as well as the Francois Gault and Cross Canada lectureships. He is the recipient of the ENI Energy Prize, the Kozo Tanabe Prize in Acid-Base CatalysisÌýand the International Natural Gas Conversion Award. He has served as editor-in-chief of Journal of Catalysis and as president of the North American Catalysis Society. He is a fellow of ACS, AIChEÌýand the Royal Society of Chemistry and an honorary fellow of the Chinese Chemical Society. His dedication to teaching has been recognized by several campus awards, including the Noyce Prize, the highest teaching award in the sciences at Berkeley.