La-hexaaluminate for synthesis gas generation by Chemical Looping Partial Oxidation of Methane Using CO2 as Sole Oxidant

Chemical looping partial oxidation of methane using a sole CO2 oxidant (CL-POM-CO2) is an emerging technology for synthesis gas generation and CO2 utilization, which is highly dependent on an oxygen carrier (OC). In this work, Fe-substituted La-hexaaluminate as the OC was found to exhibit good reactivity and stability during 50 periodic CH4/CO2 redox cycles due to the formation of magnetoplumbite La-hexaaluminate structure with the introduction of La. Deeper reduction for synthesis gas generation did not destroy the La-hexaaluminate structure via a charge compensation mechanism, which increased CH4 reactivity and further improved CO2 utilization under subsequent re-oxidation. In the La-hexaaluminate structure, O-6-Fe3+(Oh) was highly active for the total oxidation of methane, while O-5-Fe3+(Tr) and O-4-Fe3+(Th) selectively oxidized CH4 to synthesis gas. The sole CO2 oxidant only selectively recovered O-5-Fe3+(Tr) and O-4-Fe3+(Th), and thus is more favorable for improving synthesis gas selectivity than O-2/air, which offers an attractive opportunity for CO2 utilization. (c) 2017 American Institute of Chemical Engineers AIChE J, 64: 550-563, 2018