Alumina-supported manganese oxide sorbent prepared by sub-critical water impregnation for hot coal gas desulfurization

Manganese oxide was loaded on the surface of γ-Al2O3 by sub-critical water impregnation using manganese acetate and manganese nitrate precursors to synthesize Mn(A) and Mn(N) sorbents for removing H2S from hot coal gas. Active component precursors present very obvious effect on the desulfurization capacity of sorbent. Mn(A, 11) sorbent with 11% Mn content in γ-Al2O3 maintains a desulfurization efficiency of close to 100% over 480 min. However, it reduces to below 90% for Mn(N, 11) sorbent when the reaction lasts over 75 min. The characterizing results of fresh and used sorbents from different precursors using AAS, SEM, BET, Raman, XAS and XPS techniques show that the acidity and alkalinity of active component precursor solution greatly influences the loading rate, valence state and dispersion of manganese on γ-Al2O3, which are the main properties for improving desulfurization performance of sorbents. The manganese loading rate of Mn(A) sorbent is much higher than Mn(N) sorbent. The better dispersion of manganese on γ-Al2O3 and the higher Mn2+ and Mn3+ contents on the surface of sorbent afford the high desulfurization activity of Mn(A). Moreover, Mn(A, 11) performs well in removing H2S from hot gas at 400 °C after three desulfurization -regeneration cycles.

► Manganese oxide/γ-Al2O3 sorbent was prepared by subcritical water impregnation method.
► Sorbent from Mn(Ac)2∙4H2O precursor show higher sulfidation capacity than Mn(NO3)2.
► Acidity and alkalinity of precursor solution influence the properties of sorbent.
► Loading rate, valence state and dispersion of manganese dominate sorbent performance.