A Fixed-Bed Reactor for Methane Dry Reforming via a Ceria-based Redox Cycle – Modeling and Experimental Validation

Mario Zuber¹Aldo Steinfeld^1*Simon Ackermann²

• ¹ETH Zürich, Zurich, Switzerland
• ²Synhelion SA, Lugano, Switzerland

This study explores the production of sustainable aviation fuels through the sun-to-liquid pathway, focusing on the thermochemical production of syngas – a mixture of H2 and CO – using concentrated solar energy. One promising route, termed dry redox reforming, involves the dry reforming of CH4 via 20 a 2-step redox cyclic process using non-stoichiometric ceria (CeO2). This process consists of: (1) the methanothermal reduction of ceria to form syngas; and (2) the oxidation of reduced ceria with CO2 to form CO. Thermodynamic modeling and fixed-bed tubular reactor simulations of dry redox reforming are presented. Ellingham diagrams and species-temperature diagrams illustrate reaction favourability 25 and equilibrium compositions, detailing how elevated non-stoichiometries improve syngas selectivity. The thermodynamic relations are incorporated into a computational fluid dynamic solver developed within OpenFOAM. The transient solver models a system of reversible heterogeneous reactions and fluid flow over a non-stoichiometric solid oxide as a fixed-bed, accounting for the governing conservation equations in both fluid and solid phases. The model is validated with experiments 30 conducted in a lab-scale tubular reactor (𝐷fxb = 19 mm, 𝑙fxb = 30 cm, 5% educts, 𝑉̇in = 1 Ln·min-1, 𝑇sp = 936–1016 °C, ambient pressure, ceria pellet morphology), showing relative errors within 7% for key metrics such as cumulative and instantaneous conversion and selectivity. The validated model is applied as a design tool. A geometric case study considering 100% CH4 educt, ambient pressure, 𝑙fxb = 2 m, and temperatures at around 990 °C, suggests optimal operation of a reactor tube at 𝑉̇in = 10 35 Ln·min-1, with tube diameters of 7–10 cm. A novel operating strategy is introduced, priming and cycling, that leverages the 𝛿-gradient in the fixed-bed to enhance syngas selectivity and conversion, indicating the potential production of a high-purity syngas stream.