Solar fuels via chemical-looping reforming

Analysis of Two‐Step Solar Thermochemical Looping Reforming of Fe3O4 Redox Cycles for Synthesis Gas Production

“…As shown in Figure f, both H 2 and CO concentrations increased to the maximum peak when the ratio of CH 4 :O 2 was increased from 1:5 to 4:3. Thus, a decrease in the concentration of oxygen promoted both H 2 and CO production . The decrease in the amount of H 2 and CO production for the ratios of CH 4 :O 2 = 4:2 and 5:2 can be attributed to the decrease in CH 4 conversion due to the limitation of lattice oxygen exchange and thermal loss.…”

“…The result indicated that higher consumption of CH 4 resulted in a higher production of syngas. Thus, excess use of methane could lead to high selectivity toward H 2 and CO by decreasing carbon formation because, in practice, carbon formation may be limited by kinetics or heat transfer . As can be seen in Figure d, the thermal reduction of Fe 3 O 4 into FeO—Fe mixed oxide solid solution increased with the concentration of CH 4 .…”

“…However, CLC does not provide enough understanding regarding the sustainable utilization of CO 2 in chemical fuels. Furthermore, metal oxide redox with CO 2 splitting is still high between 1573 and 2250 K and is not quite compliant with the current status of concentrated solar thermal technologies . Thus, solar thermochemical looping reforming (STCLR) redox cycles for syngas production is an attractive and sustainable pathway for CH 4 and CO 2 utilization to produce H 2 and CO .…”

Rebuttal to “Theoretical and Experimental Investigation of Solar Methane Reforming through the Nonstoichiometric Ceria Redox Cycle”

“…We acknowledge that it is also beneficial to examine nonideal conditions as was done by Warren et al [1] An oxide-independent analysis was provided in our most recent work [5,6] to projecte fficiency as af unctiono fp arameters normally reportedf or experimental studies:m ethane conversion, hydrogen and carbon monoxide selectivities,a nd oxidizer conversion. Chemical-equilibrium predictions of conversions and selectivities are provided for ar ange of CH 4 /O 2 ratios.…”

“…Chemical-equilibrium predictions of conversions and selectivities are provided for ar ange of CH 4 /O 2 ratios. [6] The thermodynamic analysis of the oxide-independent process includes treatment of separationw ork for extracting syngas from the product streams,w hich has as ignificanta nd negative impact on efficiencyf or operation with incomplete methanec onversion or selectivities less than one. [6] We attribute the higher efficiency for isothermal cycling at 1273 K predicted by Warren et al [1] with excessm ethane( i.e., n = 0.5) in comparison to the predicted efficiency in our earlier analysis with n = Dd to the assumption of ah igher concentration ratio and their omission of losses caused by convection and conductionf rom the reactor.T he efficiency reported by Warren et al is higher than it would be in practice due to neglecting the work to separatesyngas from product streams.…”