Methane dry reforming via a ceria-based redox cycle in a concentrated solar power tower

Drop-in fuels produced using solar energy can provide a viable pathway towards sustainable transportation, especially for the long-haul aviation sector which is strongly dependent on jet fuel. This study reports on the experimental testing of a solar reactor using concentrated solar energy for the production of syngas, a mixture of mainly H2 and CO, which serves as the precursor for the synthesis of kerosene and other liquid hydrocarbon fuels.

Methane dry reforming via a ceria-based redox cycle in a concentrating solar tower

The thermochemical conversion route is based on the dry reforming of CH4 via a 2-step redox cyclic process utilizing the intermediation of non-sacrificial ceria (CeO2), comprising: (1) the endothermal reduction of CeO2−δox with CH4 to form CeO2−δred and syngas (δ denoting the non-stoichiometry); and (2) the exothermal oxidation of CeO2−δred with CO2 to form CO and the oxidized state of CeO2−δox. The solar reactor consists of a cavity-receiver lined with a reticulated porous ceramic (RPC) structure and an axial tubular section at the cavity’s rear filled with a packed-bed of agglomerates, both RPC and agglomerates made of pure ceria. Testing is performed at a high-flux solar tower at conditions and scale relevant to industrial implementation. For a solar radiative power input of 10 kW (corresponding to a mean solar flux of 560 suns) at temperatures in the range 800–1000 °C, with reacting gas flow rates of 105 normal L min−1 and concentrations of CH4 (reduction step) and CO2 (oxidation step) of up to 20% in Ar, the solar-driven redox reforming process yields a peak CH4 molar conversion of 70% and a peak H2 selectivity of 68%. Co-feeding of CH4 and CO2 during the reduction step resulted in the highest solar-to-fuel energy efficiency of 27%, defined as the ratio of the higher heating value of the syngas produced over the sum of the solar radiative power input through the solar reactor’s aperture and the higher heating value of CH4 fed to the solar reactor. Regardless of the operational mode, the syngas product composition was similar at equal δ attained during the reduction. The addition of the tubular packed bed increased the syngas yield by 32%.