CO2 capture by Mg–Al and Zn–Al hydrotalcite-like compounds

Abstract

Hydrotalcite-like compounds (HTC) are distinguished by their properties for CO2 capture, like high surface area, basic sites, thermal stability and good adsorption/desorption efficiency. Mg–Al e Zn–Al HTCs with Al3+ molar ratios x = 0.20, 0.28 and 0.33 were synthesized by coprecipitation, and subsequently calcined at 400 °C. For both HTCs, X-ray diffraction patterns have attested the formation of mixed oxides through calcination. The amount of basic sites, measured by temperature-programmed desorption of CO2, decreases as x increases. The CO2 adsorption was performed in a thermogravimetric balance using an adsorption temperature of 50 °C. Mg–Al and Zn–Al samples with x = 0.33 molar composition presented the highest CO2 adsorption, 0.91 and 0.21 mmol g−1, respectively. The Langmuir isotherm fitted well to the experimental data. It was also found that increasing the number of adsorption/desorption cycles the CO2 adsorption decreases, which is associated with the irreversible chemisorption.