Synthesis and CO2 capture properties of mesoporous MgAl(O) sorbent

Abstract

Mesoporous MgAl(O) sorbents with different Mg/Al molar ratios (0, 0.5, 1.0, 1.5) were synthesized via a one-step surfactant assisted precipitation method. The structural properties of these sorbents were systematically characterized by XRD, SEM, FT-IR, N₂ adsorption–desorption and CO₂-TPD. The CO₂ adsorption–desorption performance of the sample was studied in a fixed-bed reactor. The results showed that the xMgAl(O) sorbents possessed a mesoporous structure, high specific surface areas and abundant basic sites. In the synthesis process, Mg and Al species interacted with P123 to form PEO-Mⁿ⁺-anions that promoted the dispersion of MgO on the Al₂O₃. The XRD, FT-IR and CO₂-TPD results showed that the MgO was not only dispersed on Al₂O₃, but enters the Al₂O₃ framework, resulting in more exposed basic sites for CO₂ adsorption. In the CO₂ adsorption process, the CO₂ adsorption capacity of the sorbent was related to the amount of basic sites and the specific surface area. The CO₂ uptake of the sorbent significantly improved in the presence of water vapor. Results of a cycling test suggested that the sorbent was stable in multiple adsorption–desorption cycles.