Eastman Colloquium – Susannah Scott

Bio
Dr. Scott received her Ph.D. in Inorganic Chemistry from Iowa State University in 1991. She pursued her postdoctoral studies at the Institut de recherches sur la catalyse in Lyon, France with a NATO Postdoctoral Fellowship, and joined the faculty of the University of Ottawa (Canada) in 1994, where she was named to a Canada Research Chair in Catalyst Design. She moved to UCSB in 2002. She is the recipient of an NSERC Women’s Faculty Award (1994-1999), the Polanyi Prize in Chemistry (1994), a Cottrell Scholars Award (1997), and a Union Carbide Innovation Award (1998).

Abstract
The use of polyolefins to make small molecules, not limited to monomers which can be repolymerized, is an intriguing approach to recycle carbon and thereby keep plastic out of the natural environment. While catalytic hydrogenolysis leads to lower value alkanes, tandem ethenolysis-isomerization allows the selective conversion of polyethylene to the commodity monomer propylene. Hydrogen redistribution in the absence of added H2 can achieve tandem hydrogenolysis and dehydrocycloaromatization, resulting in higher value alkylaromatics at moderate reaction temperatures. The coupled reactions are greatly accelerated by the use of bifunctional hydrocracking catalysts whose acidity can be used to tune the selectivity towards surfactant-range alkylbenzenes. The key rate-determining and selectivity-controlling steps involve Brønsted acid catalysis. Unexpectedly, the presence of low pressure H2 in the reactor enhances rather than suppresses alkylbenzene formation, while suppressing undesired polyaromatic formation and accelerating the desired reduction in molecular weight. The number of alkyl substituents on the aromatic rings can be optimized via catalytic transalkylation. Other tandem processes, including the selective conversion of polyethylene to monomers under mild reaction conditions, can be designed to achieve alternative desired reaction outcomes.