In Situ XRD Detection of Reversible Dawsonite Formation on Alkali Promoted Alumina: A Cheap Sorbent for CO2 Capture

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Abstract
Alkali‐promoted aluminas are inexpensive and robust materials with significant basicity that allow CO2 uptake at relatively high temperature and pressure. In situ XRD experiments show that bulk crystalline carbonate K‐Dawsonite [KAlCO3(OH)2] phase is formed on such materials under relatively high pressure of an equimolar mixture of CO2 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 CO2 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 CO2 removal in industrial systems.

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