Final Technical Report: Metal—Organic Surface Catalyst for Low-temperature Methane Oxidation: Bi-functional Union of Metal—Organic Complex and Chemically Complementary Surface

Technical Report · Sat Oct 01 00:00:00 EDT 2016

DOI:https://doi.org/10.2172/1411530· OSTI ID:1411530

Tait, Steven L.  ^[1]

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1. Indiana Univ., Bloomington, IN (United States)

Stabilization and chemical control of transition metal centers is a critical problem in the advancement of heterogeneous catalysts to next-generation catalysts that exhibit high levels of selectivity, while maintaining strong activity and facile catalyst recycling. Supported metal nanoparticle catalysts typically suffer from having a wide range of metal sites with different coordination numbers and varying chemistry. This project is exploring new possibilities in catalysis by combining features of homogeneous catalysts with those of heterogeneous catalysts to develop new, bi-functional systems. The systems are more complex than traditional heterogeneous catalysts in that they utilize sequential active sites to accomplish the desired overall reaction. The interaction of metal—organic catalysts with surface supports and their interactions with reactants to enable the catalysis of critical reactions at lower temperatures are at the focus of this study. Our work targets key fundamental chemistry problems. How do the metal—organic complexes interact with the surface? Can those metal center sites be tuned for selectivity and activity as they are in the homogeneous system by ligand design? What steps are necessary to enable a cooperative chemistry to occur and open opportunities for bi-functional catalyst systems? Study of these systems will develop the concept of bringing together the advantages of heterogeneous catalysis with those of homogeneous catalysis, and take this a step further by pursuing the objective of a bi-functional system. The use of metal-organic complexes in surface catalysts is therefore of interest to create well-defined and highly regular single-site centers. While these are not likely to be stable in the high temperature environments (> 300 °C) typical of industrial heterogeneous catalysts, they could be applied in moderate temperature reactions (100-300 °C), made feasible by lowering reaction temperatures by better catalyst control. They also serve as easily tuned model systems for exploring the chemistry of single-site transition metals and tandem catalysts that could then be developed into a zeolite or other stable support structures. In this final technical report, three major advances our described that further these goals. The first is a study demonstrating the ability to tune the oxidation state of V single-site centers on a surface by design of the surrounding ligand field. The synthesis of the single-site centers was developed in a previous reporting period of this project and this new advance shows a distinct new ability of the systems to have a designed oxidation state of the metal center. Second, we demonstrate metal complexation at surfaces using vibrational spectroscopy and also show a metal replacement reaction on Ag surfaces. Third, we demonstrate a surface-catalyzed dehydrocyclization reaction important for metal-organic catalyst design at surfaces.

• Research Organization: Indiana Univ., Bloomington, IN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences, and Biosciences Division
• DOE Contract Number: SC0008792
• OSTI ID: 1411530
• Report Number(s): DE-IU-0008792
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
catalysis
homogeneous
heterogeneous
surface chemistry
metal-organic complexation