Synthesis of cobalt-silicon molecular sieve with excellent CO2/N2 adsorption selectivity for dynamic CO2 capture

Cobalt has a high polarizability and can form a high dispersion potential energy on the surface of zeolite, which is conductive to the capture of CO2. For the first time, cobalt-silicon molecular sieves (CSMS) were synthesized by hydrothermal method using cobalt nitrate as the cobalt source and sodium silicate as the silica source without organic template. The effects of pH values on the synthesis of molecular sieves were investigated, and the sample CSMS-12 which synthesized at pH = 12, showed the highest specific surface area and pore volume. The specific surface area (SBET) and Total volume (VTotal) of CSMS-12 are 452.8 m2·g−1 and 0.4 cm3·g−1, respectively. The result of adsorption test at 273 K and 100 kPa shows that CSMS-12 has the highest CO2 uptake (1.86 mmol·g−1), and the Dual-site Langmuir isotherm model fits well with the experimental result. CSMS-12 has excellent adsorption selectivity (123) of CO2/N2 calculated by IAST method. Furthermore, fixed-bed adsorption breakthrough experiments were carried out to investigate the performance of dynamic CO2/N2 and CO2/CH4 separation by CSMS-12 at different temperatures. The above results indicate that it can be applied to the separation of CO2 in flue gas and biogas.