Promoted methane conversion to syngas over Fe-based garnets via chemical looping

Fe-based oxygen carries (OCs) have attracted wide attention due to the low cost and environmental compatibility for chemical looping methane partial oxidation. However, they usually suffer from low CH4 reactivity mainly due to insufficient synergy between catalytic CH4 activation and lattice oxygen mobility. In this work, Fe ions with different amount were incorporated into a novel garnet structure (Y3FexAl5-xO12), which exhibited drastically increased CH4 conversion with reduction time. This resulted from in-situ formed Fe-0 sites at the early stage of reduction, which led to a more efficient reaction route involving methane catalytic decomposition on Fe-0 and the resulted carbon oxidation easier by lattice oxygen, compared with methane directly oxidized by OCs. Moreover, the amount of Fe ions in garnet influenced surface exposed Fe-0 sites and oxygen mobility, inducing Y3Fe2Al3O12 performed the best with almost 94 % methane conversion thanks to the combined advantages of larger surface exposed Fe-0 and higher lattice oxygen mobility.