The structure-reactivity relationships of using three-dimensionally ordered macroporous LaFe1−xNixO3 perovskites for chemical-looping steam methane reforming

Abstract

Chemical-looping steam methane reforming (CL-SMR) is a novel technology for syngas and hydrogen production without purification process. A series of three-dimensionally ordered macroporous (3DOM) LaFe1−xNixO3 (x = 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) perovskite-type oxides were synthesized using the polystyrene colloidal crystal templating method. The structural and physico-chemical properties of the obtained oxides were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Brunauere-Emmette-Teller (BET) surface area technologies. The structure-reactivity relationships and effects of Ni-substitution on the improvement of reactivity and resistance to carbon formation were investigated in a thermo-gravimetric analyzer and a fixed-bed reactor. It was found that the as-prepared oxides obtained standard perovskite structures and the well-ordered skeleton was surrounded with uniform close-packed macroporous windows. Ni-substitution improved the ability for oxygen supply but simultaneously enhanced the methane dissociation. While the openness channel and large surface area of 3DOM perovskite allowed low mass-transfer resistances and provided high active sites for reaction. Complicated factors synergistically affected the reactivity and an optimal value for Ni-substitution is confirmed with x = 0.1 by comprehensively considering from the points of reactivity, resistance to carbon formation, as well as hydrogen generation capacity. During the following successive redox reactions, 3DOM LaFe0.9Ni0.1O3 exhibited good regenerability and thermo-stability probably converting 90% of CH4 into syngas in methane reforming stage and generating ∼210–220 ml hydrogen in steam splitting stage.