Center for Functional Nanomaterials Seminar
"Controlling selectivity in heterogeneous catalysis with self-assembled monolayers"
Presented by Professor Will Medlin, University of Colorado
Tuesday, July 30, 2013, 10 am
Bldg. 735, Conf. Rm. B
Hosted by: Peter Sutter
Performing selective reactions of reagents with multiple functional groups is a challenging objective, since each functional group can potentially adsorb and react on a catalytic surface. Addressing this problem is particularly important for the conversion of biomass to chemicals and fuels, because carbohydrates and their downstream intermediates contain multiple reactive functional groups. For example, furfural and hydroxymethyl furfural (HMF), which can be produced in high volumes from dehydration of sugars, contain one or more oxygenate (alcohol or aldehyde) functions together with a furan ring. Alcohols, aldehydes, and furan in isolation are all reactive on Pt-group metal surfaces, and the individual reaction pathways of each group are observable when these functions are located on the same molecule. Furthermore, as will be demonstrated in this presentation, the multiple functions on furfuryl oxygenates have synergistic effects on reactivity, opening up additional reaction pathways not available to reagents containing only a single functional group. Thus, controlling selectivity through heterogeneous catalyst design is highly complex. Our group has explored several techniques for aligning multifunctional molecules above metal surfaces to promote selective reaction of a particular functional group. One such approach involves the modification of supported metal catalysts with organic ligands such as alkanethiols. Alkanethiols can be deposited on metal surfaces to form organized self-assembled monolayers (SAMs) that can potentially cause reagent molecules to adopt particular orientations above the metal surface, altering selectivity. We have recently shown that such a strategy can be applied to technical supported catalysts such as Pd/Al2O3 and Pt/TiO2 to yield dramatic selectivity improvements in several applications. At least two mechanisms by which SAMs can improve selectivity have been identified. First, SAM coatings can be used to tune