Adsorption of CO₂on Hydrotalcite-Derived Mixed Oxides: Sorption Mechanisms and Consequences for Adsorption Irreversibility

Abstract

Magnesium−aluminum double oxides derived from the thermal treatment of layered hydroxides (hydrotalcites) have been tested for CO2 adsorption. The effects of various preparation parameters, such as the incorporated cation (K or Na), the mode of addition of magnesium and aluminum precursors, the presence of sonication, and the calcination temperature, on the adsorption capacity under mild conditions were studied using thermogravimetry and calorimetry. Calorimetric and FTIR data were used to explain the adsorption mechanisms leading to the undesirable irreversible adsorption. This adsorption was related to the formation of unidentate CO2-adsorbent species with the strongest adsorption sites, whereas bidentate and surface bicarbonates lead to highly reversible adsorption. In conclusion, preparation procedures that lead to an increase in the strength of basic sites do not lead to significant increases in the adsorption capacity, but rather lead to more difficult regeneration of the saturated support.

The influences of Mg/Al molar ratio on the properties of PtIn/Mg(Al)O- x catalysts for propane dehydrogenation reaction

“…The hysteresis loop of PtIn/Mg (Al)O-2 can be classified as type H3 (according to IUPAC), the pores are correlated with slit-shaped pores due to the aggregation of flake-like particles [44]. Furthermore, type H2 hysteresis loop can be observed over PtIn/Mg(Al)O-6 and PtIn/Mg(Al)O-8 samples, which was often associated with complex and interconnected pore structure [45]. However, the isotherms of PtIn/Mg(Al)O-4 sample present an intermediate shape between those of PtIn/Mg(Al)O-2 and PtIn/Mg(Al)O-6.…”

Hydrotalcite and Hydrocalumite in Mortar Binders from the Medieval Castle of Portilla (Álava, North Spain): Accurate Mineralogical Control to Achieve More Reliable Chronological Ages

“…However, in the third decomposition step (200 • C to 600 • C) of target fraction (0.5 µm to 2 µm) from Portilla Castle samples, the TGA curve shows two weight loss steps (Figure 10). These weight losses correspond to the decomposition of LDH phases and are attributed to the loss of the OH − groups bonded to Al 3+ and to Mg 2+ in Mg-Al-CO 3 compounds [72,73]. Figure 10.…”

Effect of Mg/Al Ratio on Catalytic Behavior of Fischer–Tropsch Cobalt-Based Catalysts Obtained from Hydrotalcites Precursors

“…A first weight loss in the range 100-250°C corresponds to the loss of water molecules from the interlayer space (still maintaining the layered structure). A second weight loss at higher temperatures (300-550°C), could be attributed to dehydroxylation of the hydroxide layers together with the loss of interlayer anions, inducing the layered structure collapse in order to generate a mixedoxide [12,31,32]. Additional information is shown in online resource 1.…”