Structural Effects on the High Temperature Adsorption of CO2 on a Synthetic Hydrotalcite

• Published in: Chemistry of materials Vol. 16; no. 21; pp. 4135 - 4143
• Main Authors: Hutson, Nick D, Speakman, Scott A, Payzant, E. Andrew
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 19.10.2004
• Subjects: Applied sciences; Chemistry; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; General and physical chemistry; Physicochemistry of polymers; Physics; Polymers; Inorganic compounds; Organic compounds
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm040060u

Hydrotalcite-like compounds (HTlcs) are solid sorbents that may potentially be used for high-temperature separation and capture of CO2. The high-temperature adsorption of CO2 on Mg−Al−CO3 HTlc is affected by structural changes that take place upon heating of the material. The structural changes of a synthetic HTlc upon heating to 200 and 400 °C in a vacuum were characterized using various analytical techniques. These structural changes were then related to observed behavior with respect to the physisorption and chemisorption of CO2 at 200 °C. Upon heating to 200 °C, the material retains its layered structure, though the interlayer spacing is decreased by ∼0.6 Å due to loss of interlayer water. Chemisorption of CO2 at 200 °C represents more than half of the total adsorption capacity (at 107 kPa) due to increased availability of the framework Mg2+ cation and the subsequent formation of MgCO3. There is no significant increase of surface area or pore volume after heating to 200 °C. Upon heating to 400 °C the CO3 2- in the interlayer is decomposed and the material is completely dehydrated and partially dehydroxylated. The resulting amorphous 3-D structure with increased surface area and pore volume and decreased availability of the Mg2+ cation favors physisorption over chemisorption for these samples. An increased understanding of structure−property relationships will help in the further development of HTlcs as viable CO2 solid sorbents.