Novel Zn-Ti-based mixed metal oxides for low-temperature adsorption of H2S from industrial gas streams

The efficiency of various Zn-Ti-based mixed metal oxides prepared by the sol-gel method towards H2S adsorption from a gas mixture containing 0.06 vol.% H2S, 25 vol.% H2, 7.5 vol.% CO2 and 1 vol.% H2O was studied in the 25-100 °C range. The effects of the chemical nature of a third metal additive (M = Mn, Cu, Mo) and its at.% composition in the M-Zn-Ti-O solid on the H2S adsorption and regeneration performance of the latter were studied. The nominal chemical composition (metal at.%) of the solid adsorbent was found to have an important effect on the number, chemical composition and particle morphology of the crystal phases formed. It was found that the mixed metal oxides with compositions 20Zn-80Ti-O and 40Zn-60Ti-O present higher maximum H2S uptakes than ZnO and TiO2 solids also prepared by the sol-gel method. In addition, the Zn-Ti-O mixed metal oxides showed higher H2S uptakes after regeneration with 20% O2/He in the 500-750 °C range compared to the ZnO and TiO2 solids. It was found that the10Mn-45Zn-45Ti-O solid results in higher H2S uptakes than a commercial Ni-based H2S adsorbent in the 25-50 °C range. The effectiveness of the regeneration procedure of the 10Mn-45Zn-45Ti-O solid following sulfidation was found to be in the 45-170% range depending on the sulfidation temperature and regeneration conditions applied. The solid with composition 10Cu-45Zn-45Ti-O calcined at 200 °C (after synthesis) exhibited three times higher H2S uptakes at 25 °C than a commercial Ni-based adsorbent, result not obtained at higher calcination temperatures.