Session: 13-02: Hydrogen Production and Storage

Paper Number: 156511

156511 - Nickel-Catalyzed Methane Reforming With Synergistic Cerium-Assisted Iron Oxidation in Chemical Looping Dry Reforming 

Abstract: 

Methane (CH₄) and carbon dioxide (CO₂) are two major greenhouse gases that contribute to global warming leading a climate change. Chemical looping dry reforming of methane (CLDRM) decouples dry reforming of methane into two separate chemical reactions, including methane and CO₂ steps. CLDRM converts two major greenhouse gases into value-added products called syngas, H₂ and CO, which can be utilized as a feedstock for various fuels and chemicals. This study investigates the synergistic interaction between iron-nickel oxide and ceria for CLDRM at 700°C, 800°C, and 900°C. At various temperatures, ceria, Fe-Ni oxide, and Fe oxide on ceria, exhibited negligible reactivity. Ni oxide on ceria showed high reactivity but it suffers from carbon accumulation even during 10 cycles. However, when Fe-Ni oxide is supported on ceria, it greatly enhances the reactivity for both CH₄ and CO₂. The mechanistic understanding of the materials has been investigated by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS).

XAS discovered nickel does not serve as an oxygen carrier. Additionally, XRD confirms that nickel remains its metallic phase even after CO₂ step. Based on performance, the role of Ni is facilitating methane pyrolysis and promotes the reduction of cerium oxide. At 800°C, a certain amount of nickel is required to reduce cerium oxide. At an elevated temperature, less Ni loading is needed for methane pyrolysis because high temperature also facilitates methane pyrolysis.

On the other hand, Fe and Ce act as oxygen carriers. Two outperformed materials at each temperature, Fe_0.50Ni_0.50O_x/CeO₂ at 800°C and Fe_0.85Ni_0.15O_x/CeO₂ at 900°C, exhibited the highest iron redox exchange capacity. During the CO₂ step, Fe can chemically interact with cerium oxide to form cerium orthoferrites (CeFeO₃) as an oxidation product, which enhances methane conversion. XRD proved that Fe_0.50Ni_0.50O_x/CeO₂ is the only material that showed both cerium reduction and CeFeO₃ formation. At 900°C, there is more CeFeO₃ formation as the sample has more iron contents, despite the anomalous Ce redox giving +3 Ce in the oxidation product.

Therefore, using an optimal Ni loading, which depends on the reaction temperature, is critical to provide sufficient Ni catalysis of methane conversion and sufficient Fe and Ce for high redox capacity via CeFeO₃. Fe_0.85Ni_0.15O_x/CeO₂ material demonstrated stable conversion rates for methane and CO₂ over 100 CLDRM cycles at 900°C, with a negligible amount of the carbon accumulation in methane accumulating as solid carbon across the cycles. Our findings illustrate the mechanisms of the iron-nickel-cerium oxide system for efficient and durable CLDRM, offering valuable insights into mixed catalyst and oxygen carrier material system design.

Presenting Author: Minjung Kim The Ohio State University

Presenting Author Biography: I am a 3rd-year PhD student in the Department of Mechanical and Aerospace Engineering, specializing in hydrogen production. The current research focuses on converting two major greenhouse gas into value-added products. I am passionate about addressing global energy challenges.