CO2 adsorption and desorption properties of calcined layered double hydroxides

Abstract

In this study, the CO2 adsorption properties of different metal mixed oxides (MMO) obtained by calcination of different layered double hydroxides (LDH) are addressed. Four types of LDH, with composition $$\left[{{\text{M}}_ {1 - {\text{x}}}^{2 +} {\text{M}}_{\text{x}}^{3 +} \left({\text{OH}} \right)_{2}} \right]^{{\text{x} +}} \cdot[{\text{A}}_{\text{x/n}}^{{\text{n} -}} \cdot {m}{\text{H}}_{2} {\text{O}}]^{{\text{x} -}},$$ where M2+=Zn, Cu, Ni, M3+=Al, x = 0.33, n = 2 and A = CO 3 2− , were studied by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and thermogravimetric analysis coupled with mass spectrometry (TG-MS). Different thermal behaviors upon heating were observed depending on the LDH composition, resulting in the exploitation of different calcination temperatures to convert LDH into mixed metal oxides (MMO). MMO were exposed to ambient air or pure carbon dioxide atmosphere to evaluate CO2 adsorption properties. Aging in ambient condition leads to adsorption of both CO2 and water, from ambient moisture, with variable ratios depending on the MMO composition. Furthermore, all the MMO were demonstrated to be able to adsorb CO2 in pure gas stream, in the absence of moisture. In both ambient and pure CO2 conditions, the performance of MMO is strongly dependent on the metal composition of MMO. In particular, the presence of Cu in the structure turned out to be beneficial in terms of adsorption capacity, with a maximum mass gain for CuAl MMO of 4 and 15% in pure CO2 and in atmospheric conditions, respectively.