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

Abstract

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, O6‐Fe3+(Oh) was highly active for the total oxidation of methane, while O5‐Fe3+(Tr) and O4‐Fe3+(Th) selectively oxidized CH4 to synthesis gas. The sole CO2 oxidant only selectively recovered O5‐Fe3+(Tr) and O4‐Fe3+(Th), and thus is more favorable for improving synthesis gas selectivity than O2/air, which offers an attractive opportunity for CO2 utilization. © 2017 American Institute of Chemical Engineers AIChE J, 64: 550–563, 2018