Casey O'Brien: Rational Catalyst Design from Model Studies with a Molecular-Beam/Surface-Spectroscopy Apparatus
Location:131 DeBartolo Hall
Selective hydrogenation of α,β-unsaturated aldehydes, a class of multi-functional compounds that have conjugated C=C and C=O bonds, is a critical step in the production of many fine chemicals and pharmaceuticals. The unsaturated alcohol produced from selective hydrogenation of the C=O bond is the desired product, but thermodynamics strongly favors hydrogenation of the C=C bond. Therefore, selective hydrogenation of α,β-unsaturated aldehydes is not only an industrially important reaction, it is also a fundamentally interesting problem: how does the structure of a heterogeneous catalyst influence the selectivity, and how can a catalyst be rationally designed with high selectivity towards unsaturated alcohol production?
In this talk, I will show that the selectivity in hydrogenation of α,β-unsaturated aldehydes can be controlled by manipulating the structure of Pd model catalysts—both single crystal Pd(111) and Pd nanoparticles dispersed on planar oxide supports. Near 100% selectivity towards the desired product unsaturated alcohol is possible, but only after modification of the catalyst surface by organic deposits during the initial stages of the reaction. By applying a combination of multi-molecular beam techniques and in-situ infrared reflection absorption spectroscopy, the chemical nature of the organic deposit that enhances selectivity is identified. Using structure-selectivity relationships obtained from these model studies under well-defined ultra-high vacuum conditions, several promising strategies for designing practical catalysts with high selectivity towards C=O hydrogenation in α,β-unsaturated aldehydes are proposed.
Army Research Laboratory
Casey O’Brien received his B.S. in Chemical Engineering from the University of Colorado at Boulder in 2006 and his Ph.D. in Chemical Engineering from Carnegie Mellon University in 2011. Thereafter, he was a postdoctoral fellow in the Chemical Physics Department of the Fritz Haber Institute of the Max Planck Society. He joined the Sensors and Electron Devices Directorate of the U.S. Army Research Laboratory in 2014. His research is focused on understanding how the structure and composition of catalytic surfaces—including heterogeneous catalysts and catalytic membranes—influences the surface reaction mechanisms in order to rationally design surfaces with high activity, selectivity, and durability. He has recently developed a novel spectroscopic tool and technique, operando membrane spectroscopy, which enables the spectroscopic characterization of membranes under realistic permeation conditions with simultaneous measurement of trans-membrane gas permeation rates.