Understanding the effect of H2S on the capture of CO2 using K-doped Li4SiO4 sorbent

Li4SiO4 is a well-acknowledged CO2 sorbent in the sorption-enhanced reforming system for low-cost H-2 production with a high purity. However, the inevitable presence of H2S in the biomass-derived syngas etc. could possibly affect the in-situ CO2 adsorption significantly, which is important but has never been reported. In this work, the adsorption of CO2 using Li4SiO4 was investigated under varying H2S concentrations and reaction temperatures, and a series of characterization techniques were utilized to understand the effect of H2S and its action mechanism. The results show that the presence of H2S causes a rapid loss-in-capacity of Li4SiO4 in capturing CO2 during the cyclic reactions, and a higher concentration greatly exacerbates the problem. Moreover, the negative impact of H2S is found to have a strong relationship to the reaction temperature. It is proposed that at 325 similar to 475 degrees C, Li4SiO4 and H2S react to form bits of Li2S and some kinds of sulfates, and at 625 similar to 775 degrees C, a large amount of dense KLiSO4 is generated covering the surface of the sorbent. In contrast, at a high temperature above 925 degrees C, sintering of Li4SiO4 plays a critical role, leading to a significant change on its microstructure.

Automated summary

This study investigated the impact of H2S on the adsorption of CO2 using Li4SiO4, finding that the presence of H2S significantly reduces the capture capacity of Li4SiO4, with higher concentrations exacerbating the issue. Additionally, the negative impact of H2S was found to be strongly correlated to the reaction temperature.