Solar fuels via chemical-looping reforming

Krenzke, Peter T.; Fosheim, Jesse; Davidson, Jane H.

doi:10.1016/j.solener.2017.05.095

Cited by 64 publications

(65 citation statements)

References 187 publications

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“…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.…”

Section: Resultsmentioning

confidence: 93%

“…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 .…”

Section: Resultsmentioning

confidence: 99%

“…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 .…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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A two‐step solar thermochemical looping reforming (STCLR) of CH4—Fe3O4 redox cycles via H2O and CO2 splitting is investigated for H2 and CO production. The P1 approximation is adopted for the radiation heat transfer and high‐temperature thermal characteristics of active materials in the reaction medium. A benchmark experimental setup for the conversion of solar energy to syngas based on the solar thermochemical technology is presented. The effects of operating conditions on the yield of H2 and CO as well as syngas production are investigated at both thermal reduction and oxidation steps. It is found that the key performance of two‐step CH4—Fe3O4 redox cycles for a higher H2 and CO production depends on the efficiency of methane and oxidizer (H2O and CO2) conversion. Furthermore, a substantial amount of H2 and CO production with carbon deposition is obtained when the thermal reduction is extended to the mixed oxide solid solution (FeO—Fe). Among the oxygen carriers, FeO exhibits a higher oxygen exchange for H2 production. However, the synergetic effect of FeO—Fe reactivity strongly contributes to syngas yield. The present solar reactor model can significantly contribute to the reduction of greenhouse gas emission by utilizing 40% of CO2 emissions into solar fuels such as H2 and syngas. The results indicate that highly selective syngas with an H2/CO ratio close to 2 can be obtained with a strong control of γ = H2O/CO2.

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Section: Resultsmentioning

confidence: 93%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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“…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.…”

mentioning

confidence: 99%

“…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.…”

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confidence: 99%

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

Krenzke

Davidson

2017

Energy Tech

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In this note, we rebut the implication by Warren et al. in 10.1002/ente.201700083 that the sequential method of applying equilibrium applied by us to model the reaction between ceria and methane in solar chemical looping reforming (SCLR) is incorrect. They assert that their simultaneous method produces different results. Here, we point out that the two methods are fundamentally identical. The only difference in the two approaches is the mechanics of performing the calculations. Furthermore, the nonstoichiometries reported by Warren et al. support the consistency of the two methods when interpreted correctly.

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Modified Ceria for “Low‐Temperature” CO₂Utilization: A Chemical Looping Route to Exploit Industrial Waste Heat

Haribal

Wang

Dudek

et al. 2019

Advanced Energy Materials

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Efficient CO 2-utilization is key to limit global climate change. Carbon monoxide, which is a crucial feedstock for chemical synthesis, can be produced by splitting CO 2. However, existing thermochemical routes are energy-intensive requiring high operating temperatures. We report a Hybrid Redox Process (HRP) involving CO 2-to-CO conversion using a lattice oxygen-deprived redox catalyst at relatively low temperatures (<700 °C). The lattice oxygen of the redox catalyst, restored during CO 2-splitting, is subsequently used to convert methane to syngas. Operated at temperatures significantly lower than a number of industrial waste heat sources, this cyclic redox process allows for efficient waste heat-utilization to convert CO 2. To enable the low temperature operation, we report lanthanum modified ceria (1:1 Ce: La) promoted by rhodium (0.5 wt. %) as an effective redox catalyst. Near-complete CO 2 conversion with a syngas yield of up to 83% at low temperatures were achieved using Rh-promoted LaCeO 4-x. While La improves low-temperature bulk redox properties of ceria, Rh considerably enhances the surface catalytic properties for methane-activation. Density Functional Theory calculations further illustrate the underlying functions of La-substitution. The highly effective redox catalyst and HRP scheme provide a potentially attractive route for chemical production using CO 2 , industrial waste heat, and methane, with appreciably lowered CO 2 emissions.

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Solar fuels via chemical-looping reforming

Cited by 64 publications

References 187 publications

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

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

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

Modified Ceria for “Low‐Temperature” CO₂Utilization: A Chemical Looping Route to Exploit Industrial Waste Heat

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Solar fuels via chemical-looping reforming

Cited by 64 publications

References 187 publications

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

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

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

Modified Ceria for “Low‐Temperature” CO2Utilization: A Chemical Looping Route to Exploit Industrial Waste Heat

Contact Info

Product

Resources

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

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

Modified Ceria for “Low‐Temperature” CO₂Utilization: A Chemical Looping Route to Exploit Industrial Waste Heat