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Abstract: Flue gas SO2 removal at 200°C over Mo and Co doped V2O5/AC catalyst-sorbents and regeneration of the used catalyst-sorbents in H2 at 380°C in the same reactor are studied in this paper. Compared with V2O5/AC, the catalyst-sorbents containing Co show higher SO2 uptake while the one containing Mo shows a slightly lower SO2 uptake. Elemental sulfur is produced during H2-regeneration of the used catalyst-sorbents when effluent gas of the regeneration is recycled back to the reactor. H2-regeneration of the used V2O5/AC produces little elemental sulfur, but the Mo and Co doped ones show high elemental sulfur yields with an elemental sulfur selectivity of 50% for a catalyst-sorbent containing 2% V2O5, 0.5% MoO3 and 0.5% CoO, V2Mo0.5 Co0.5/AC. Molybdenum and cobalt sulfides are likely formed in the regeneration, which catalyze the elemental sulfur formation but reduce the SO2 uptake of the catalyst-sorbents in the subsequent SO2 removal stage. [Copyright &y& Elsevier]

Abstract: H2 regeneration of an activated carbon supported vanadium and cobalt oxides (V2O5-CoO/AC) catalyst–sorbent used for flue gas SO2 removal is studied in this paper. Elemental sulfur is produced during the H2-regeneration when effluent gas of the regeneration is recycled back to the reactor. The regeneration conditions affect the regeneration efficiency and the elemental sulfur yield. The regeneration efficiency is the highest at 330 °C, with SO2 as the product. The production of elemental sulfur occurs at 350 °C and higher with the highest elemental sulfur yield of 9.8 mg-S/g-Cat. at 380 °C. A lower effluent gas recycle rate is beneficial to elemental sulfur production. Intermittent H2 feeding strategy can be used to control H2S concentration in the gas phase and increase the elemental sulfur yield. Two types of reactions occur in the regeneration, reduction of sulfuric acid to SO2 by AC and reduction of SO2 to elemental sulfur through Claus reaction. H2S is an intermediate, which is important for elemental sulfur formation and for conversion of CoO to CoS that catalyzes the Claus reaction. The catalyst–sorbent exhibits good stability in SO2 removal capacity and in elemental sulfur yield. [Copyright &y& Elsevier]

Abstract: Bi2WO6 samples with hierarchical microspheres structures built by higher order 2D nanoplate alignment were successfully synthesized by sol–gel-hydrothermal route. The structures and morphologies of the products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). UV–vis diffuse reflectance spectra indicated that as-prepared Bi2WO6 with hierarchical microspheres structures had enhanced absorption in both UV and visible light areas. Photocatalytic activities of the samples were evaluated by the degradation of methylene blue (MB) under visible light irradiation. Due to the unique morphology and porous structure, the hierarchical Bi2WO6 microspheres exhibited better photocatalytic activities than that of the Bi2WO6 prepared by hydrothermal routes. [Copyright &y& Elsevier]