Adsorption behavior and kinetics of H\u3csub\u3e2\u3c/sub\u3eS on a potassium-promoted hydrotalcite

\u3cp\u3eAdsorption of H\u3csub\u3e2\u3c/sub\u3eS and the influence of steam on its adsorption capacity and kinetics were studied on a commercial potassium-promoted hydrotalcite. The sorbent shows a very high cyclic working capacity for H\u3csub\u3e2\u3c/sub\u3eS compared to CO\u3csub\u3e2\u3c/sub\u3e and H\u3csub\u3e2\u3c/sub\u3eO, even at lower partial pressures and at different operating temperatures ranging between 300 and 500 °C. The operating temperature does not significantly influence the cyclic working capacity for half-cycle times of 30 min. The adsorption mechanism, however, changes at higher temperatures. At lower temperatures (300 °C) a fast adsorption with a fast approach to steady state was observed. At higher operating temperatures, H\u3csub\u3e2\u3c/sub\u3eS reacts with the hydrotalcite structure, forming strongly bonded sulfuric species on the sorbent. When using dry regeneration conditions, the first cycles in cyclic operation at higher temperatures show a significantly higher adsorption of H\u3csub\u3e2\u3c/sub\u3eS (especially the first cycle), which cannot be desorbed during regeneration with N\u3csub\u3e2\u3c/sub\u3e. After the first fast initial adsorption rate a continuous slow adsorption of H\u3csub\u3e2\u3c/sub\u3eS occurs, probably caused by a surface reaction between H\u3csub\u3e2\u3c/sub\u3eS and the hydrotalcite structure. This reaction is, however, reversible if steam is used. The adsorption mechanism for H\u3csub\u3e2\u3c/sub\u3eS and H\u3csub\u3e2\u3c/sub\u3eO was determined using multiple cyclic experiments comparable to previous studies performed for CO\u3csub\u3e2\u3c/sub\u3e and H\u3csub\u3e2\u3c/sub\u3eO adsorption. It is evident that the adsorption mechanism developed for CO\u3csub\u3e2\u3c/sub\u3e on the same sorbents is also valid for H\u3csub\u3e2\u3c/sub\u3eS, indicating that the developed mechanism is consistent for sour gas adsorption on this type of sorbents. The cyclic working capacity can be significantly increased if steam is used during the regeneration step of the sorbent. The mechanistic model developed for the adsorption of CO\u3csub\u3e2\u3c/sub\u3e and H\u3csub\u3e2\u3c/sub\u3eO was successfully validated with more than 160 different TGA experiments. An operating temperature of 400 °C seems to be optimal to achieve a high cyclic working capacity for H\u3csub\u3e2\u3c/sub\u3eS, because at higher temperatures the regeneration of the formed sulfuric species seems to be hindered resulting in a significant decrease in the cyclic working capacity.\u3c/p\u3