(609e) Experimental Investigation of Methane Reformation Via the Nonstoichiometric Ceria Redox Cycle

Dry reformation of methane via the nonstoichiometric ceria (CeO₂ â?? CeO_2-δ)redox cycle was theoretically and experimentally examined for converting high-temperature solar process heat to syngas. The aforementioned cycle is conducted through two phases: (1) endothermic reduction of ceria in methane and (2) exothermic oxidation of the reduced ceria with carbon dioxide. In both regimes, chemical equilibrium calculations suggest total selectivity and favorability towards syngas production above 827 °C, enabling isothermal operation and providing motivation for the following experimental evaluation. An array of seven xenon short arc lamps provided solar-simulated, high-flux radiation to indirectly irradiate a packed bed of ceria situated within a cavity receiver. The endothermic reduction of ceria in methane was demonstrated at three discrete temperatures: 950, 1035, and 1120 °C. Upon completion of reduction, nonstoichiometry (δ) equaled 0.07, 0.21, and 0.24, yielding methane conversions of 9, 41, and 51 % respectively. Subsequent oxidation was first performed with oxygen to indirectly quantify carbon deposition. This proved to be minimal, but its overall long term effect on cycling stability is still under investigation. Finally, isothermal operation was executed at 1120 °C and the solar-to-fuel conversion efficiency, defined as the ratio of calorific value of syngas (H₂ and CO) produced to the combined input solar radiative energy and the caloric value of methane converted, was measured as 3.71 % average and 4.56 % peak. Results indicate that a packed bed configuration is not optimal for this process and further reactor optimization efforts are underway.