Evaluation of Fe substitution in perovskite LaMnO3 for the production of high purity syngas and hydrogen

Abstract

Chemical looping reforming of methane (CLRM) technology is a new approach for syngas and pure hydrogen generation. During the whole reaction, methane is first partially oxidized to syngas by the lattice oxygen of the oxygen carrier, and then the lattice oxygen of the reduced oxygen carrier is recovered by thermal water splitting, with pure hydrogen produced. LaMnO3 is used as an oxygen carrier for the CLRM. It obtains a high resistance to carbon deposition, while a lower CH4 conversion due to the unstable structure. Fe ion substitution in LaMnO3 can be used to improve its reactivity and thermal stability. La1-xMnFexO3/LaMn1-xFexO3 (x = 0.05, 0.1, 0.15, 0.2) oxygen carriers own higher reactivity and better resistance to carbon deposition, producing high purity syngas and hydrogen. La0.85MnFe0.15O3 sample exhibits the highest CO selectivity (~99%), syngas productivity (3.78 mmol g−1) and H2 productivity (1.76 mmol g−1) due to the higher oxygen vacancy concentration, and its H2/CO molar ratio is maintained at the ideal ratio of 2.0 (1.93–2.07) during the whole process. Notably, no carbon deposition is generated over LaMnO3, La0.85MnFe0.15O3 and LaMn0.9Fe0.1O3 oxygen carriers even after 20 redox cycles, and La0.85MnFe0.15O3 exhibits superior resistance to carbon deposition due to the better structural and thermal stability.