In Situ XRD Detection of Reversible Dawsonite Formation on Alkali Promoted Alumina: A Cheap Sorbent for CO 2 Capture

Alkali‐promoted aluminas are inexpensive and robust materials with significant basicity that allow CO 2 uptake at relatively high temperature and pressure. In situ XRD experiments show that bulk crystalline carbonate K‐Dawsonite [KAlCO 3 (OH) 2 ] phase is formed on such materials under relatively high pressure of an equimolar mixture of CO 2 and steam (total pressure of 10 bar) and at temperatures up to 300 °C. In parallel, typical needle‐shaped Dawsonite crystallites are observed by SEM after exposure to similar conditions. Furthermore, the in‐situ experiments show that the carbonate crystalline phase disappears between 300–400 °C, and that K‐Dawsonite crystalline phase can be reformed by lowering the temperature in the range 200–300 °C and contacting the material with both steam and CO 2 at sufficiently high partial pressure. In a fixed‐bed reactor a high breakthrough capacity of 1.5–1.7 mmol g –1 has been measured. The experimental results reported herein highlight the high potential of alkali‐promoted alumina for cyclic CO 2 removal in industrial systems.