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

Abstract

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.

N2 and CO2 Adsorption by Soils with High Kaolinite Content from San Juan Amecac, Puebla, México

“…The CO 2 retention at 298 K in HDP-montmorillonite (clay) (0.038-0.06 mmol/g) [26] and Skardon River kaolinite (0.056 mmol/g) [27] also have different operation conditions from those proposed in the present research. At the same time, these are all lower than those previously reported in activated carbons [16,28], zeolites [2], and synthetic materials [29]. …”

Ultramicroporous silicon nitride ceramics for CO2 capture

“…3,4 Materials with chemisorption mechanism adsorb CO 2 selectively even in the presence of other gases and can operate at high temperatures, indicating advantages over solid materials, which operate by physisorption mechanism. [11][12][13] These materials include amine-modified solid sorbents, 12,14,15 inorganic-based materials such as hydrotalcites, 16 lithium zirconates, 17 and partially, porous materials with unsaturated metal centers (UMCs). 13 Because of the rigid network of UMCs, the accessibility of CO 2 to the adsorption sites is restricted and thus, CO 2 is not adsorbed through a pure chemisorption mechanism.…”

Novel Sorption Enhanced Reaction Process for Simultaneous Production of CO2 and H2 from Synthesis Gas Produced by Coal Gasification

“…A final peak is associated with a large amount of CO 2 (m/e - = 44) and it increases past the the temperature limitations of the system and is due to breakdown of the 59 hydrotalcite structure. 54 The relatively large size of these peaks reveals that the majority of the methanol had been adsorbed onto these stronger surface basic sites. The strength of the particular sorption sites can be directly related to the temperature at which they desorb; lower desorption temperatures indicate a weaker interaction with the surface.…”