Session: 17-05: Symposium Steinfeld - Concentrated solar power and thermal/thermochemical energy storage

Paper Number: 140548

140548 - Chemical Looping Reforming of Methane Over Ni-Ceria at Elevated Pressure 

Abstract: 

Solar-driven chemical looping reforming of methane (CLRM) is an attractive pathway toward renewable syngas production, a mixture of hydrogen (H₂) and carbon monoxide (CO), which serves as a feedstock for production of liquid hydrocarbon fuels. CLRM consists of two reaction steps, namely the partial oxidation of methane (POM) which is achieved through reduction of an oxygen carrier material, followed by carbon dioxide (CO₂) and/or steam dissociation facilitated by re-oxidization of the oxygen carrier material. POM typically occurs at temperatures ranging from 700°C to 1100°C, with re-oxidation occurring in the same temperature range. The oxygen carrier, also known as a redox intermediate, is typically a metal oxide such as nonstoichiometric ceria (CeO_2-δ), where δ is the oxygen non-stoichiometry of the metal oxide. Recent work from Hill et al. has shown promising CLRM behavior using Ni- decorated CeO_2-δ as the redox intermediate. This is due to the observed rapid kinetics during oxygen exchange, high conversions of reactants, and high selectivity of products toward syngas. However, this has only been experimentally demonstrated at atmospheric pressure with relatively low concentrations of reactant gas (e.g. less than 10%).[1] In this work, we study the effects of increased process pressure (up to 5 bar) on volume-specific yields, reactant conversion, and product selectivity for CLRM using a custom designed, fully automated packed bed reactor and data collection system. Moreover, we are also interested in understanding the impacts of pressure and higher CH₄ concentrations (up to 100 volume-%) on the reaction kinetics and carbon deposition, which model estimates suggest should increase with increasing pressure. Our methodology consists of repeating cycles of reduction and oxidation over a packed bed of Ni- CeO_2-δ, where the sample is fully re-oxidized during the second step of every redox cycle. Each experiment occurs at constant temperature and pressure with varying reactant concentrations for differing cycles. Preliminary results indicate reaction kinetics can be enhanced at higher pressure, but the reaction mechanisms and subsequent impact are currently not well understood. Furthermore, at atmospheric pressure, the effects of carbon deposition during the reduction stage of CLRM are mitigated by delivering sufficient CO₂ during oxidation to fully oxidize the solid carbon. We aim to demonstrate this benefit at higher pressures and understand the potential limitations and impact that carbon deposition can have on the CLRM process under these conditions. The results of this experimental campaign will give insight into the performance and viability of Ni-CeO_2-δ at scale for syngas production via solar-driven CLRM.

[1] Hill, C., Robbins, R., Furler, P., Ackermann, S., and Scheffe, J., 2023, "Kinetic investigation of solar chemical looping reforming of methane over Ni–CeO 2 at low temperature," Sustainable Energy & Fuels, 7(2), pp. 574-584.

Presenting Author: Kathryn Trimm University of Florida

Presenting Author Biography: Kathryn G. Trimm is originally from Alaska and Texas. She received her Bachelor of Science in mechanical engineering from Louisiana Tech University in the spring of 2020. While at Louisiana Tech, Kathryn performed undergraduate research under Dr. Arden Moore. Additional experiences include interning for the Rotorcraft Aeromechanics branch of NASA and interning at the Air Force Research Lab Munitions Directorate. She pursued her Master of Science in mechanical engineering from the University of Florida (UF), under the direction of Dr. Jonathan Scheffe, and graduated in the spring of 2022. While at UF, Kathryn also worked part-time for Applied Research Associates as a simulations intern. Currently, Kathryn is attending the University of Florida, earning her Doctor of Philosophy in mechanical engineering continuing her research under Dr. Jonathan Scheffe.

Authors:

Kathryn Trimm University of Florida
Daymara Nieves University of Florida
Simon Ackermann Synhelion SA
Caroline Hill University of Florida
Philipp Furler Synhelion SA
Jonathan Scheffe University of Florida