Ordered mesoporous Fe-Al2O3 based-catalysts synthesized via a direct 'one-pot' method for the dry reforming of a model biogas mixture

Abstract

Biogas plays a vital role in the emerging renewable energy sector and its efficient utilization is attracting significant attention as an alternative energy carrier to non-renewable fossil fuel resources. Since biogas consists mainly of CH4 and CO2, dry reforming of methane arises as an appropriate process enabling its chemical conversion to high-quality synthesis gas (syngas: H2 and CO mixtures). In this study, we synthesized via a direct "one-pot" method following an evaporation-induced self-assembly approach, ordered mesoporous Fe10%, Ni5% and Fex%Ni(1-x) (x: 2.5, 5 or 7.5%) in Al2O3 as catalysts for syngas production via dry reforming of a model biogas mixture (CH4/CO2 = 1.8, at a temperature of 700 °C). Monometallic Fe10%Al2O3 catalyst presented lower reactivity levels and slightly deactivated during catalysis compared to stable Ni5%Al2O3. According to physico-chemical characterization techniques, the incomplete reduction of Fe2O3 into Fe3O4 rather than Fe0 nanoparticles (catalytically active) coupled with the segregation of Fe3O4 oxides were the main factors leading to the low performance of mesoporous Fe10%Al2O3. These drawbacks were overcome upon the partial substitution of Fe by Ni (another transition metal) forming specifically bimetallic Fe5%Ni5%Al2O3 displaying reactivity levels close to thermodynamic expected ones. The formation of Fe-Ni alloys stabilized iron inside alumina matrix and protected it from segregation. Along with the confinement effect, spent catalyst characterizations showed high resistance towards coke deposition.