X-type and MCM-41-type molecular sieves from full component utilization of coal gasification fine slag and amino modification for CO₂ capture

The development of coal gasification technology inevitably generates a substantial amount of coal gasification fine slag (CGFS), which contains abundant silica-aluminum elements. Utilizing these elements to synthesize molecular sieve materials for CO₂ capture is of great significance. In this paper, to fully utilize the elements in CGFS, X-type and MCM-41-type molecular sieves were synthesized through activated hydrothermal and microwave treatment of the solid residue after alkali fusion and the silica source filtrate, respectively. These molecular sieves were then modified with varying mass fractions of tetra ethylene phentermine (TEPA). The microscopic morphology, pore structure, and CO₂ adsorption performance of the animated molecular sieves were subsequently characterized. The results showed that the synthesized X-type molecular sieves exhibited regular cubic crystals, with a specific surface area of 542 m²/g and an adsorption capacity of 56.3 cm³/g (298 K). After TEPA modification, there was a significant reduction in both specific surface area and pore volume, which led to a decrease in adsorption capacity. The adsorption process demonstrated typical physical adsorption characteristics. The synthesized MCM-41-type molecular sieve has a two-dimensional six-square structure with a specific surface area of 1469 m²/g and an adsorption capacity of 17.9 cm³/g (298 K), which was modified by 30 % TEPA with a decrease in the pore volume, a narrower pore size distribution, and the appearance of the -NH group, and the increase in the active site increased the adsorption capacity of the CO₂ molecule by 6.6 cm³/g (298 K), which showed a typical chemisorption characteristic. This coupled strategy, which involves the full-component utilization of CGFS components and CO₂ capture, provides both a theoretical and practical foundation for the effective use of solid waste.