Synthesis of Porous Cobalt Oxide and Its Performance for H2S Removal at Room Temperature

Two types of cobalt oxide–silica composites were prepared by sol–gel method using different alcohols (n-butyl alcohol and ethylene glycol) in sol precursors. The corresponding adsorbents with 3DOM structure were also fabricated via a colloidal crystal template method. Physicochemical properties of the materials were characterized by means of numerous techniques, and the performance for hydrogen sulfide (H2S) removal were evaluated at room temperature. It was found that using n-butyl alcohol in sol precursors could achieve a material (SCN57-500) with plentiful ordered mesoporous in grains and thus had very large surface area (314.5 m2/g), whereas the sample obtained from ethylene glycol (SCE57-500) only possessed a smaller surface area. After introducing 3DOM structure into the bulk counterpart, the surface area improved remarkably as in the case of 3D-SCE57-500, which is consistent with our previous studies. However, 3D-SCN57-500 showed a decreased surface area compared with SCN57-500. The loss of surface area was due to the sharply decreased pores in grains, which is originated from sintering when the hard template was burning out during the preparation process. It can be deduced that the increased surface area after introducing 3DOM structure was ascribed to the excellent dispersion, i.e., the newly formed very small nanoscale grains. The results of adsorption experiments show that although SCN57-500 owned the highest surface area among these four adsorbents, however, it exhibited a poorest performance for H2S capture. Both 3DOM samples possessed very favorable breakthrough H2S capacity compared to the counterparts without 3DOM structure. The results indicated that size of crystalline or dispersion and not the surface area is what contributes to the reactivity of the adsorbent. The well-ordered and interconnected macropores play an important role as well. The breakthrough sulfur capacity of 3D-SCE57-500 could reach as high as 189 mg/g with Co3O4 utilization of 63%. The involved reactions for H2S removal by Co3O4 in experimental conditions were suggested.