Novel Fe–Mn–Zn–Ti–O mixed-metal oxides for the low-temperature removal of H2S from gas streams in the presence of H2, CO2, and H2O

Abstract The efficiency of Fe–Mn–Zn–Ti–O mixed-metal oxides of varying composition prepared by sol–gel methods toward removal of H 2 S from a gas mixture containing 0.06 vol% H 2 S, 25 vol% H 2 , 7.5 vol% CO 2 , and 1–3 vol% H 2 O was studied in the 25–100 °C range. In particular, the effects of the Fe/Mn molar ratio in the Fe–Mn–Zn–Ti–O solids on the H 2 S uptake and regeneration performance of the solids were studied. The nominal chemical composition (metal mol%) of the Fe–Mn–Zn–Ti–O solids was found to strongly influence the chemical composition, particle size, and morphology of the crystal phases formed. It was found that the 5 Fe–15 Mn–40 Zn–40 Ti–O mixed-metal oxide provides the highest H 2 S uptake as fresh and after regeneration in 20% O 2 /He gas mixture in the 500–750 °C range compared with the other solids investigated. It was also found that 5 Fe–15 Mn–40 Zn–40 Ti–O exhibits higher H 2 S uptake than a commercial Ni-based H 2 S adsorbent in the 25–50 °C range. In particular, a three times greater H 2 S uptake at 25 °C compared with that on the commercial adsorbent was found. The effectiveness of the regeneration procedure of 5 Fe–15 Mn–40 Zn–40 Ti–O solid after complete sulfidation was found to be in the 48–82% range, depending on the sulfidation temperature and regeneration conditions applied. A detailed characterization of the fresh, sulfided, and regenerated 5 Fe–15 Mn–40 Zn–40 Ti–O and 20 Fe– 40 Zn–40 Ti–O solids, which exhibited the best and worst H 2 S uptake performance, respectively, using BET, XRD, Raman, XPS, and Mossbauer techniques revealed important information on the sulfidation mechanism. The present work provides new fundamental knowledge that could trigger further research efforts toward the development of alternative mixed metal oxides not based on toxic chromia (Cr 2 O 3 –Fe 2 O 3 / α -Al 2 O 3 ), which is used today in several industrial plants for the catalytic oxidation of H 2 S (Claus process).

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