(127e) Beyond the Active Site - Controlling the Local Chemical Environment of Active Sites to Achieve Improved Catalytic Performance

I will discuss our recent work on developing multifunctional catalytic materials that allow for not only the control over the structure of the active catalytic site but also the environment in which this active site resides. By controlling the environment, we are able to control the chemical potential of reactive species and therefore direct chemical transformations in specific (desired) directions.

I will illustrate the phenomena using examples of developing catalyst/membrane multifunctional systems for oxidative coupling of methane (OCM) and propane dehydrogenation (PDH). OCM is a direct route for converting methane into ethylene and ethane (C₂). When performed in conventional packed bed reactors (PBRs) this process suffers from significant thermodynamic and kinetic limitations over almost all explored catalysts. We will show that a membrane/catalyst system with distributed oxygen feed (i.e. an O^2- conducting membrane reactor) and properly selected catalyst and membrane materials can give significantly higher C₂ selectivity and yield compared to a PBR. In another example, we will focus on PDH. The conversion in the PDH reaction is equilibrium limited. We will show how membrane/catalyst systems allow us to in-situ remove H₂ from the product stream and by taking advantage of the Le Chatelier's principle remove the equilibrium limitations on the reaction conversion.

References:

1. AH Motagamwala, R Almallahi, J Wortman, VO Igenegbai, S Linic*, Stable and selective catalysts for propane dehydrogenation operating at thermodynamic limit, Science, 373 (6551), 217-222, 2021, (DOI: 10.1126/science.abg7894)
2. V.O. Igenegbai, R. Almallahi, R.J. Meyer, S. Linic*, Oxidative Coupling of Methane over Hybrid Membrane/Catalyst Active Centers: Chemical Requirements for Prolonged Lifetime, ACS Energy Letters, 4 (6), pp 1465-1470, 2019: (DOI: 10.1021/acsenergylett.9b01075)