NSF-DFG Echem: CAS: Electrochemical Pyrrolidone Synthesis: An Integrated Experimental and Theoretical Investigation of the Electrochemical Amination of Levulinic Acid (ElectroPyr)

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Today's chemical, energy, and transportation industry is increasingly confronted with a depletion of fossil resources. In addition, anthropogenic climate change is strongly related to utilization of fossil oil, gas, and coal. For later generations, it is of major importance to valorize renewable carbon sources for industrial applications and avoid further increase of CO2 emissions. Biomass presents a promising renewable carbon source bearing the potential to create closed carbon cycles, with net zero CO2 emissions. With funding from the NSF Division of Chemistry, Professor Philippe Sautet of the University of California-Los Angeles, in collaboration with German colleagues at the RWTH-Aachen, is developing bio-based routes to fine chemicals. Renewable energy sources (solar, wind, etc.) already generate an excess of electricity and the electrochemical conversion of renewable raw materials into fine chemicals or fuel additives is one way of making sensible use of this excess. The chosen reactant, levulinic acid, is one of the twelve most promising platform chemicals identified by the US Department of Energy. The project focuses on its electrochemical transformation into pyrrolidones, important intermediates for pharmaceutical products, solvents, and polymers. In general, electrochemistry enables milder reaction conditions compared to chemocatalysis and provides the potential to integrate renewable electrical energy into chemical value chains. In the case of the proposed pyrrolidone synthesis, high hydrogen pressure can be avoided, and aqueous electrolytes are projected to facilitate an integration along the bio-refinery value chain. In addition to the broader socioeconomic impacts of the research outcomes on a sustainable economy and on climate, the international collaboration between the US and German research teams will provide the students involved in the research with a unique cultural and educational experience.The project aims for an integrated experimental and theoretical investigation of the electrochemical amination of levulinic acid to produce pyrrolidones. The Sautet group will focus on first-principle simulations of the electrocatalytic surface reaction aiming for a comprehensive mechanistic understanding. The RWTH-Aachen group will experimentally investigate the transformation with emphasis on the influence of electrocatalyst and process parameters. The project will likely improve fundamental understanding of the mechanism of electrochemical amination. It will also provide key insights into the factors controlling catalytic surface reactivity of the electrocatalyst. Finally, major process parameters will be explored experimentally. The major objective of this study is for the collaborative team to conduct a detailed mechanistic investigation. For this purpose, the reaction, which can be divided into three sub-steps, will be considered separately. First, the imine formation on model substrates, then the electrocatalytic hydrogenation to the amine and finally the condensation to the pyrrolidone will be investigated both computationally and experimentally. The proposed reaction pathway will be examined by detailed mechanistic studies and will be further investigated by comparison with model substrates. Acetone, for example, is a suitable model compound for the first and second reaction steps. However, deeper experimental insights will be given by variation of the chain length as well as expansion of the functional groups present in the corresponding model substrates. Moreover, all experimental investigations will be accompanied by an optimization of the electrode material and the reaction conditions. A computational screening of different electrocatalysts will be performed, based on kinetic modelling and scaling relations.This research was funded under the NSF-DFG Lead Agency Activity in Electrosynthesis and Electrocatalysis (NSF-DFG EChem) opportunity NSF 20-578.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.