CAREER: Nitrogen Activation: Splitting Kinetic Cycles and Breaking Energetic Barriers with Pulsed Catalysis

Worcester Polytechnic Institute, Worcester MA

Investigators

Abstract

Many industrial chemical processes utilize catalysts to increase reaction rates at fixed conditions of feed rates, temperature, and pressure. The project addresses a new approach to process technology, known as dynamic catalysis, in which the catalyst temperature is varied on the time scale of reactions occurring on the catalyst surface. The rapid temperature modulation can potentially create conditions that dramatically accelerate the overall reaction rate or change the product distribution in favorable ways. The study will evaluate the effectiveness of dynamic catalysis by both experimental and theoretical means, with an ultimate aim of decreasing the energy requirements for the catalytic synthesis of ammonia. Considering the highly energy-intensive nature of the industrial ammonia synthesis process, a cleaner and less energy-intensive alternative will have significant economic and environmental impacts. The primary goal of the study is to develop a new catalytic strategy for overcoming thermodynamic and kinetic barriers by dynamically operating a catalytic cycle at various temperatures and thermodynamic environments. However, the catalytic nitrogen fixation cycle is blocked at near-ambient conditions by a lack of energy to overcome kinetic/thermodynamic barriers (low temperature) or unfavorable binding energies for surface intermediates (high temperature/low pressure). The study will investigate the possibility that energetic barriers can be overcome at catalytically relevant resonant cycle times by rapidly and dynamically pulsing energy into the system (timescale of approximately 10 milliseconds). The approach combines 1) multi-scale modeling to demonstrate expected catalytic enhancement and determine optimal operating conditions, and 2) experimental testing and reactor design of a pulsed catalysis platform. The expected outcome is new understanding of the potential for nonequilibrium catalytic turnover from both theoretical and experimental approaches. Ideally, the fundamental understanding will lead to the design of catalyst platforms that operate beyond the theoretical maximum in catalytic turnover suggested by the classic volcano plot relation. The research will be integrated with a wide range of educational and outreach activities aimed at elevated engagement in STEM from students and the public, with particular emphasis on connections between basic research and societal impacts of the nitrogen cycle. 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.