Mg-Zn-Al LDH: Influence of intercalated anions on CO2 removal from natural gas

In this study, three components Mg-Zn-Al LDH were synthesized by microwave assisted homogenous precipitation using urea hydrolysis. The physicochemical properties of the prepared solids were evaluated using XRD, FTIR, elemental analysis, surface characterization measurements, and electron microscope. The results indicated the formation of the layered structure containing the three metals in one phase. By controlling the synthesis condition, carbonates as well as nitrogen containing anions were intercalated within the interlayer space of the LDH structure. The type of the nitrogenous species depended on the type and concentration of M (II) cation. The nitrogen adsorption-desorption isotherms were found to be type IV. The specific surface area decreased with increasing zinc content. However, the high specific surface area could be related to inter-particle agglomeration. The TEM images indicated the presence of nanoparticles. The particle size was affected by the concentration of zinc content. The particles of the smallest size (~14-25 nm) were detected in Mg-Zn-Al LDH (Mg:Zn molar ratio = 1:3). The amorphous mixed oxides (LDO) were obtained after the thermal treatment of the as-synthesized LDH at 550 °C. The abilities of the as-synthesized Mg-Zn-Al LDH materials and corresponded LDO to capture carbon dioxide from methane stream were tested using dynamic flow system technique at the ambient conditions of temperature and pressure. The results indicated that the presence of nitrogen containing anions in MgZn(25:75)Al LDH enhance the CO2 adsorption capacity (3.55 mmol/g) relative to its corresponded oxide (3.03 mmol/g).