Determination of interactions between lignin model compounds and catalytically active Metal-Organic Frameworks using NMR and EPR
EMSL Project ID
49310
Abstract
Lignin is the most abundant source of renewable aromatics, with 200-300Mtons/yr projected production by a US biofuels industry that would process ~1B tons of biomass to meet DOE goals. However, there are currently no efficient processes for extracting these aromatics and converting them to value-added chemicals and drop-in fuels. We are working to develop lignin valorization methods in which oxidative solubilization provides a feedstock for industrially robust catalysts based on Metal-organic Frameworks (MOFs). MOF catalysts we developed can cleave various bonds within lignin model compounds, using both hydrogenolysis and oxidative conditions. We propose to use NMR and EPR to probe the interactions of lignin model compounds with catalytically active metal-organic frameworks (MOFs). Our objective is to obtain detailed information concerning the mechanisms of catalysis and to quantify the reaction kinetics, which will assist us in designing improved catalysts that can use solubilized lignin itself as a substrate. Due to harsh reaction conditions (elevated H2 pressures and temperatures, for example), we can only analyze initial and final reaction states with the instrumentation available in our laboratories. During the first year, we will use NMR to probe the interaction of substrate molecules with reactive open metal sites in the MOF catalysts and will perform measurements under elevated H2 pressures using unique, high-pressure, high-temperature cells available at EMSL. We will also examine MOFs doped with transition metals, which exhibit enhanced catalytic activity, to probe the location of these dopants. Reaction kinetics will be quantified by NMR using both "snapshot" experiments (samples reacted for fixed time periods and then quenched) and real-time measurements. Here, we seek to determine rate constants and to identify parasitic side pathways that negatively impact selectivity. Finally, we will employ the EPR instrumentation at EMSL to search for hydrogen radicals, which we hypothesize are formed when H2 is activated by dopant metals in these catalysts. This research will contribute directly to the Energy Materials & Processes Science Program by providing molecular-level information concerning reaction mechanisms for a new class of catalysts that can selectively decompose lignin, providing a promising route to value-added chemicals that can improve the economics of a biofuels industry. Consequently, this work is well aligned with the fundamental DOE mission to provide for U.S. energy security and economical routes to biofuels.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2016-10-01
End Date
2018-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members
Related Publications
Stavila V., M. Foster, J.W. Brown, R.W. Davis, J. Edgington, A.I. Benin, and R.A. Zarkesh, et al. 2019. "IRMOF-74(n)-Mg: a novel catalyst series for hydrogen activation and hydrogenolysis of C-O bonds." Chemical Science 10, no. 42:9880-9892. PNNL-SA-147308. doi:10.1039/C9SC01018A