(297a) Promoting Selectivity In Heterogeneous Catalysis with Self-Assembled Monolayers

The utilization of inorganic catalyst modifiers in supported metal catalysts is widespread, but the intentional use of organic modifiers to promote selectivity is rare. Modification of metal surfaces with organic ligands represents a unique opportunity, in that the structure and functionality of the ligands can be controllable varied to optimize performance.  Our group has explored several techniques to promote selectivity in hydrogenation reactions, including the modification of supported metal catalysts with organic ligands.  Alkanethiols can be deposited on metal surfaces to form organized self-assembled monolayers (SAMs) that alter the selectivity of several catalytic reactions.  This attachment strategy was found to enhance the selectivity to the desired product during epoxybutene hydrogenation from 15% on uncoated catalysts to as high as 95% on SAM coated catalysts at equivalent reaction conditions. SAM-coated Pd catalysts also exhibited improved selectivity at comparable conversion for acetylene hydrogenation to ethylene. In this contribution, experiments aimed at identifying the mechanisms behind observed selectivity and activity trends will be described.