Solid-phase synthesis of silicalite-1 molecular sieve based on fly ash and its CO2 adsorption performance

In this work, an alkali melting-pickling assisted solid phase synthesis method of S-1 zeolite molecular sieve with excellent adsorption properties for CO₂ was successfully developed by using solid waste fly ash. SiO₂ with a purity of up to 97.84% was successfully extracted by using alkaline fusion activation, high temperature calcination and pickling. The CO₂ adsorption capacity of the prepared SiO₂ was 0.51 mmol/g at 298 K and 1 bar. Silicalite-1 molecular sieve was prepared by solid phase synthesis method using SiO₂ extracted from fly ash as silicon source. The results showed that the prepared Silicalite-1 had good morphology and relatively high crystallinity. The specific surface area is 623.30 m²/g, and the total pore volume is 0.31 cm³/g. In addition, the adsorption capacity of CO₂ was 2.05 mmol/g at 298 K and 1 bar. Compared with the prepared SiO₂, the adsorption capacity of CO₂ by Silicalite-1 molecular sieve increased by four times. Moreover, under the test condition of 298 K, it has a high selectivity coefficient for CO₂/N₂ mixed gas, and after 10 times of adsorption-desorption cycle tests, the adsorption capacity of Silicalite-1 molecular sieve for CO₂ does not change significantly, and its adsorption rate can still be as high as 89.31%. The results indicate that Silicalite-1 molecular sieve prepared by solid phase synthesis method has good adsorption selectivity and adsorption–desorption cycle regeneration stability, and can be used in the field of CO₂ adsorption, separation and purification. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.