CO2 sorption on hydrotalcite and alkali-modified (K and Cs) hydrotalcites at high temperatures

The concept of in situ removal and capture of CO2 at high temperature using a sorbent for sorption-enhanced reaction processes (SERP) is an area where improvements of sorptive materials are required. The aim of this work is the development of a suitable adsorbent to be employed at temperatures above 573 K in SERP processes for hydrogen production from methane steam reforming. Sorption of carbon dioxide was studied in three commercial hydrotalcites with different Mg/Al ratio. To study the effect of impregnation with two alkali metals, the three hydrotalcites were impregnated with cesium and potassium and a sorbent screening was performed. The novelty of this work was the determination of carbon dioxide sorption equilibrium isotherms at 579, 676 and 783 K on two samples, one modified with potassium carbonate and other with cesium carbonate. The alkali-modified samples showed a maximum loading at 676 K being MG30-K the one with highest capacity (0.76 mol/kg wet basis at 0.40 bar of CO2 partial pressure). A study of the cyclic stability of this material was performed, showing that there was only small loss of capacity after 75 sorption/desorption cycles.