Structural and textural properties of Fe2O3/γ-Al2O3 catalysts and their importance in the catalytic reforming of CH4 with H2S for hydrogen production

Abstract

Newer catalysts for the methane reforming with H2S are designed, which are based on Fe2O3/γ-Al2O3, nanocrystalline γ-Al2O3 supports, and 1.0 to 6.0 wt% Fe. The main phases are identified as hematite and γ-Al2O3, with sizes of about 2–4 nm. The structural features are characterized by X-ray diffraction, Rietveld's Refinement and Radial Distribution Function analysis. The textural properties of these catalysts are determined by N2 sorption and surface fractal dimension calculations. Also, the electronic states are inferred by Mössbauer and UV–Vis (diffuse reflectance) spectroscopies. The activity of Fe2O3/γ-Al2O3 catalysts in the methane reforming is tested in a fixed bed type reactor. Further calculations indicate that Fe2O3/γ-Al2O3 catalysts go through a charge transfer decrease, which depends on the iron content, i.e., from 1.08 to 0.88 eV; Mössbauer spectroscopy reveals that Fe3+ ions adopt a tetrahedral coordination, which coincides with their higher activity for hydrogen production, with respect to catalysts having octahedral coordination. The specific surface area of these catalysts is about 84 m2 g−1, with a mean pore diameter of 2.5 nm. A mechanism for the methane reforming with H2S is proposed herein.