Enhanced CO2 capture from methane-stream using MII -Al LDH prepared by microwave-assisted urea hydrolysis

In this study, layered double hydroxide [M^II-Al LDH (M^II = Mg/Zn)] were used as selective CO₂ adsorbents from methane stream. It prepared by microwave (MW) assisted homogenous precipitations via urea hydrolysis. The LDH structures and the type of intercalated anions were confirmed by the X-ray diffraction (XRD), Fourier transform infrared (FTIR), thermal analysis (DSC and TGA), and elemental analysis, and scanning and transmission electron microscopes (SEM and TEM) imaging. The results indicated that; the LDH morphology and the intercalated anions (carbonate and urea species) were dependent on MW power, time, and M^II type. The predominant urea species were carbamate and isocyanate for Mg-Al LDH and Zn-Al LDH, respectively. The efficiencies of the LDH were tested towards CO₂ capture from methane stream using dynamic flow system under atmospheric pressure. Effect of temperature and adsorption/desorption cycles were studied. The best CO₂ adsorption capacities obtained at (30 °C) were 3.25, and 2.47 mmol g⁻¹ for Mg-Al-LDH and Zn-Al LDH, respectively. Whereas, those for the calcined LDH (at 550 °C) were 2.96 and 2.29 mmol g⁻¹ for Mg-Al-LDO and Zn-Al LDO, respectively. The results revealed the role of the intercalated urea derived anions type in enhancing the LDH adsorption properties to selectively capture CO₂ from methane stream.