CAREER: Mechanistic Understanding and Strategies to Improve the Regeneration of Supported Nickel Catalysts for Methane Conversion

University Of Connecticut, Storrs CT

Investigators

Abstract

The acceleration of global warming has produced a pressing need to reduce greenhouse gas emissions despite the ever-increasing demand for energy. In the United States, natural gas combustion has become the No. 1 source of electricity generation. However, the carbon dioxide (CO2) associated with natural gas combustion, combined with methane emissions during its extraction and transport, still contributes to greenhouse gas emissions beyond levels required for energy sustainability. Two technologies - gas-to-liquids (GTL) and catalytic methane pyrolysis (CMP) – hold promise for producing hydrogen for both fuel and chemicals manufacturing while decreasing greenhouse gas emissions. However, catalyst deactivation due to carbon deposition and metal sintering are still major challenges in methane valorization reactions. Previous research studies have not explored process-based catalyst deactivation and regeneration mechanisms in sufficient depth to devise energy-efficient, effective regeneration strategies. To that end, the project will directly address fundamental knowledge gaps in the regeneration of prototypical supported nickel (Ni) catalysts to enable new options for extending methane catalyst lifetime, thus contributing to better carbon management and further reduction of greenhouse gas emissions during the transition to sustainable fuels and chemicals. Although the regeneration of spent methane conversion metal catalysts has been described phenomenologically, a comprehensive fundamental understanding of carbon gasification and metal redispersion has been lacking. This is partly due to conventional investigation methodologies in heterogeneous catalysis that focus mainly on the catalytic reaction kinetics and dynamics of molecules adsorbed on catalyst surfaces, not on the structural dynamics of solid catalysts. The project will combine state-of-the-art, in-situ environmental transmission electron microscopy (ETEM) with a branch of machine learning known as computer vision to directly monitor both carbon deposits and Ni catalyst structural changes under regeneration conditions. Advancement of fundamental understanding of spent metal catalyst regeneration will be achieved through three aims: 1) establish an operando methodology for high-throughput correlation of regeneration performance and structural evolution, 2) determine carbon gasification mechanisms and kinetics for optimized gasification conditions, and 3) determine metal redispersion mechanisms and support effects enabling a cyclic reaction-regeneration process. Successful integration of the three aims will establish direct correlations between the gasification kinetics and state of the catalyst during the carbon removal, gasification-induced sintering, and Ni redispersion sequence. The correlations will enable rational tuning of regeneration condition parameters to achieve complete carbon removal and effective Ni catalyst redispersion. These fundamental insights into rejuvenating spent Ni catalysts can lead to new practical regeneration strategies for other supported metal catalyst systems. Beyond the technical aspects of the project, the investigator will establish an interdisciplinary, practical, and inspiring program “The Amazing Life Cycle of Nanocatalysts.” The program will train a new generation of students in catalysis through activities integrating research into education, interactive workshops that excite and inspire students and K–12 teachers about STEM fields, and outreach efforts attracting and recruiting underrepresented students to engineering. 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.