Study On CO₂Capture Using Layered Double Hydroxides As Adsorbents

In view of the green house gas CO2emissions reduction, which is one of the international issues, this work has carried out to study on CO2capture using layered double hydroxides as adsorbents.Anionic surfactant intercalated layered double hydroxides was synthesized by a coprecipitation method. The physical and chemical properties of these materials have been studied, using X-ray diffraction, N2adsorption and desorption at lower temperature and elemental analysis. Adsorption of CO2on these materials were investigated by thermogravimetric analysis. The cluster models of the layered double hydroxide were fully optimized by density functional theory at the level of B3PW91/Lanl2DZ. The effect of various factors, such as kinds of anion surfactants, kinds of divalent and trivalent metal cations, replacement with Ni, addition of potassium carbonate, on the physical and chemical properties of layered double hydroxides have been studied. These properties were correlated with the CO2adsorption capacity of layered double hydroxides, when the metal composition of layered double hydroxides was unchanged and kinds of anion organic surfactants was changed, CO2adsorption capacity was bigger on the material with a smaller surfactant anion intercalated, because of it had a bigger total pore volume. When the kinds of anion organic surfactants was unchanged and divalent and trivalent metal cations was changed, the total pore volume of the material with more surfactant anions intercalated was smaller. However, the CO2adsorption capacity was determined by the intermolecular force between CO2molecular and layers. If the brucite-like layers had a bigger LUMO orbital density of hydroxyl, the hydrogen bond between CO2molecular and hydroxyl could be formed more easily. CO2adsorption capacity of the material was decreased, if Replaced of Mg to Ni and adding of potassium carbonate.Amine modified layered double hydroxides were prepared by an exfoliation route. The physical and chemical properties of these materials have been studied, using X-ray diffraction, N2adsorption and desoiption and elemental analysis. Adsorption of CO2on these materials were investigated by thermogravimetric analysis. The CO2adsorption mechanism was studied by using the in-situ diffuse reflectance infrared Fourier transform spectroscopy and quantum chemistry calculation. The effect of various factors, such as kinds of divalent and trivalent metal cations, replacement with Ni, addition of deionized water at amine modified, on the physical and chemical properties of layered double hydroxides have been studied.CO2adsorption capacity of the material was determined by the content of amine loading. When the Mg was replaced by Ni, the content of amine loading was decreased. When the kinds of divalent and trivalent metal cations was changed, the content of amine loading was increased on anionic surfactant intercalated material with a big crystallite size along the c axis. The adsorption of CO2on amine modified layered double hydroxides followed the mechanism of zwitterion mechanism. Upon amine modified, the optimal amount of deionized water added was O.lml/g, and it had nothing to do with the kinds of amino silane. CO2adsorption capacity and amine efficiency were the highest with the optimal amount of deionized water added.This work will provide experimental and theoretical basis for exploiting CO2adsorbents with high adsorption capacity, excellent adsorption selectivity and good cycle performance, provide for reference on developing environment friendly, efficient and economical CO2capture technology.