Surface Studies of Multifunctional Oxygenates on Metals

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

CBET-0828767 Medlin Intellectual merit. The development of integrated biorefineries for production of fuels and chemicals from biomass-derived sugars poses a number of key challenges for catalysis. Among these challenges is the need to design catalysts that are selective for reactions of a single functional group within a multifunctional oxygenate molecule. Nearly all of the so-called biorefining building block molecules?including polyols, levulinic acid, and their derivatives?incorporate at least two functional groups that are typically oxygen-containing. In the case of polyols these functional groups are invariant, whereas in other cases (such as for levulinic acid and its cyclic derivatives) the various functional groups are distinct. In all cases, however, it is desirable to be able to control reactivity to a single functional position. To design catalyst structures with controlled selectivity, a better understanding is needed of the binding configurations adopted by multifunctional oxygenates on key catalytic surfaces, such as Pt-group metals. It is proposed to study the adsorption and thermal chemistry of a variety of multifunctional oxygenates, focusing on polyols and cyclic esters or ethers, on the Pd(111) surface. High resolution electron energy loss spectroscopy will be employed to characterize adsorbate structure and to identify reaction intermediates, and temperature programmed desorption will be used to track the kinetics for adsorbate desorption and the evolution of volatile reaction products. Density functional theory calculations will be employed as a tool to facilitate atomic-scale interpretation of spectroscopic results. Molecular parameters such as the number of functional groups, the spacing between functional groups, and the length of pendant alkyl groups will be varied in the studies of adsorption and thermal chemistry of these oxygenates. The primary objective of the proposed work is to identify how the presence of multiple functional groups in oxygenate molecules affects adsorption and surface reaction pathways. The ultimate goal of this line of research is to aid in developing strategies for achieving better control over reactivity toward a single functional group in a complex carbohydrate molecule. While this goal will require consideration of how surface processes are altered by changes in surface structure and composition, the principal focus of this proposal is on a thorough assessment of how changes in the molecules themselves control surface chemistry. Broader impact. The general objective of achieving selectivity control in reactions of molecules with multiple functional groups on surfaces would be transformative for many applications related to production of both petroleum- and biomass-derived chemicals. Furthermore, the surface chemistry of compounds such as polyols and furans is important both within the biorefining concept and in the traditional chemical sector. A better understanding of the factors controlling multiple binding of adsorbates could therefore make an impact in a number of industries. The proposed research is well-aligned with the objectives of the Colorado Center for Biorefining and Biofuels (C2B2), an industry-supported center for which the PI is the University of Colorado site director. The project will benefit from several programs associated with C2B2, including a program modeled after the NSF REU program, a postdoctoral fellows program, and regular meetings with industry sponsors. A program for involvement of minority undergraduate researchers in this research is also proposed.