Synthesis of LSX Using Seed-iteration Approach with High N2 Adsorption Capacity for Air Separation

A series of low silica X zeolites (LSX) was synthesized through a seed-iteration approach, based on the seed addition strategy, and then loaded with lithium ions by an ion exchanging method to obtain high N 2 adsorption capacity. These zeolites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR), thermogravimetric analysis (TGA) and N 2 adsorption-desorption, and the adsorption capacity of N 2 and O 2 was evaluated by the vacuum pressure swing adsorption (VPSA) operation. The results showed that the nucleation period of the synthetic process could be effectively shortened by adding seed; as the seed iterations increased, the specific surface area and pore volume of the zeolites increased; the higher specific surface area and the pore volume, the higher the extent of the N 2 adsorption capacity, with the maximum reaching 28.05 cm 3 /g. However, there were no significant differences in the adsorbed capacity of O 2 by each sample. Therefore, the N 2 /O 2 separation factor also increased gradually with iterations, with the maximum up to 6.61.