Study on release and inhibition behavior of COS during high-temperature gas desulfurization process using Zn-based oxide derived from hydrotalcite

High-temperature coal gas desulfurization is one of the key technologies for coal clean conversion process. Previous studies have shown that Zn-based oxide derived from Zn-Al hydrotalcite (ZnAl-HTO) can efficiently remove H2S from high-temperature gas. However, there is a lack of qualitative and quantitative studies on the law of COS release during the desulfurization process. In this study, the possible pathways of COS release in the desulfurization process of ZnAl-HTO were investigated, the thermodynamic analysis and experimental study were also carried out. A nickel doping strategy was proposed to inhibit the formation of COS during the desulfurization process. It was shown that the main way to generate COS when zinc-aluminum hydrotalcite-based oxides to remove CO2 from gas is the gas-solid phase catalytic reaction between H2S and CO2, and the amount of COS released by this way accounts for 78% of the total release. The doping of a small amount of nickel additives into the ZnAl-HTO results in no significant change in the morphology. It also effectively inhibits the COS release during desulfurization process. Under the optimal molar ratio of Zn/Ni (30), the overall desulfurization performance of ZnAl-HTO is significantly improved. Compared to sorbents without Ni-doping, the amount of COS released before H2S-breakthrough reduced by 88%, while the corresponding sulfur capacity declined by only 1.5%. © 2023 Materials China. All rights reserved.