Thermodynamic assessment of non-catalytic Ceria for syngas production by methane reduction and CO2 + H2O oxidation

Abstract

Chemical looping syngas production is a two-step redox cycle with oxygen carriers (metal oxides) circulating between two interconnected reactors. In this paper, the performance of pure CeO 2 /Ce 2 O 3 redox pair was investigated for low-temperature syngas production via methane reduction together with identification of optimal ideal operating conditions. Comprehensive thermodynamic analysis for methane reduction and water and CO 2 splitting was performed through process simulation by Gibbs free energy minimization in ASPEN Plus ®. The reduction reactor was studied by varying the CH 4 /CeO 2 molar ratio between 0.4 and 4 along with the temperature from 500 to 1000 °C. In the oxidation reactor, steam and carbon dioxide mixture oxidized the reduced metal back to CeO 2 , while producing simultaneous streams of CO and H 2 respectively. Within the oxidation reactor, the flow and composition of the mixture gas were varied, together with reactor temperature between 500 and 1000 °C. The results indicate that the maximum CH 4 conversion in the reduction reactor is achieved between 900 and 950 °C with CH 4 /CeO 2 ratio of 0.7-0.8, while, for the oxidation reactor, the optimal condition can vary between 600 and 900 °C based on the requirement of the final product output (H 2 /CO). The system efficiency was around 62% for isothermal operations at 900 °C and complete redox reaction of the metal oxide.

A perspective on three sustainable hydrogen production technologies with a focus on technology readiness level, cost of production and life cycle environmental impacts

“…Apart from these two materials, no material could produce hydrogen efficiently below 1373 K in literature on the thermochemical hydrogen production cycles. Non-volatile non-stoichiometric oxides ( in M is not an integer but a decimal number) such as zirconium oxide have provided a new route for the development of thermochemical materials for renewable energy production due to their superior thermo-kinetic characteristics for hydrogen production, good structural stability, and moderate reduction temperature [ 93 ]. Heat recovery is crucial to improve the energy conversion efficiency.…”

Solar Disc Concentrator: Material Selection for the Receiver

“…Considerable research studies point out interesting aspects and points for improvement. For example, the efficiency of thermochemical cycles must be improved [20,21]. Considerable improvements, also in terms of cyclability and repeatability must be achieved, not only for solar-driven thermochemical cycles but also for other applications.…”