NMR and Computational Studies of Chemical Transformations at Complex Interfaces for Catalytic Applications
EMSL Project ID
34001
Abstract
Catalysis science is at the core of many of the DOE's programs including its core energy mission. Catalysts, both homogeneous and heterogeneous, facilitate the control of chemical reactions by raising the rates at which chemical bonds are formed or broken, which can lead to: improved selectivity and control over the formation of unwanted by-products, lower energy use, and reduction of the waste stream for the process. We are employing an integrated experimental/theoretical approach with an overall objective to advance significantly our ability to understand, design, and control chemical transformations on transition metal oxide (TMO) catalysts, specifically for reduction-oxidation and acid-base chemistries, and for metals embedded in zeolites to control a variety of catalytic reactions forming C-C bonds. Our approach combines novel synthesis methods for preparing supported metal oxide catalysts with controlled structures and atomic connectivity on a wide range of well-defined scaffolds, structural and functional characterization of realistic and model catalysts, mechanistic chemistry, and a strong coupling of electronic structure calculations with the experiments. Two critical tools which are closely integrated in our proposed effort are the use of NMR and computational chemistry. This proposal describes our use of these two tools including the development of new NMR probes to better understand the catalytic chemistry of metal oxides and single metals embedded in oxide supports. We propose to use modern NMR methods coupled with advanced computational techniques to address the complex interfaces present in heterogeneous catalysts. This work falls into the Science of Interfacial Phenomena science theme of the EMSL. We propose to study TMO catalysts to enable the control of the activity and selectivity of TMO catalyzed acid-base and redox chemistry. We can use organometallic precursors to exchange with the protons in the acid site of a zeolite to generate catalysts which combine the high activity and selectivity of molecular homogeneous catalysis with the ease of separation and lack of corrosion of heterogeneous catalysis. We propose to use our experimental and computational techniques to fully explore the details of the potential energy surface for complete catalytic processes, for example C-C bond forming reactions as well as ligand exchange processes. For instrumental development, we propose to construct the next generation of our DMAT probe on the EMSL 300MHz spectrometer so that pressure control up to 15 atms and temperature up to 250°C can be reached. We propose to study a variety of reactions on these catalysts. We will use MAS NMR to measure the chemical shifts of 51V, 95Mo, 27Al and 1H MAS to determine further information on the electronic nature of the catalysts and to quantify key species. NMR chemical shifts for a wide range of systems will be calculated at the density functional theory (DFT) level, in some cases, including relativistic effects. We will calculate not only the chemical shifts but also the chemical shift tensor components to better understand the actual electron distributions in the heterogeneous catalyst sites. The combination of techniques will provide us with unique insights into the interfacial behavior of catalysts.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2009-10-01
End Date
2012-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Carr RT, M Neurock, and E Iglesia. 2011. "Catalytic Consequences of Acid Strength in the Conversion of Methanol to Dimethyl Ether." Journal of Catalysis 278(1):78-93. doi:10.1016/j.jcat.2010.11.017