Investigation of the reaction time and hydrothermal synthesis route on the SSZ-13 zeolite particle crystallization and CO2 adsorption

Abstract

This study investigates the influence of synthesis time (1–4 days) and synthesis route for the fast production of SSZ-13 zeolites via the conventional hydrothermal method for CO₂ adsorption. Two synthesis routes were examined using different Si precursors: tetraethyorthosilicate (Route T) and silica (Route L). The samples were characterized by XRD, FTIR, SEM, ²⁹Si and ²⁷Al MAS-NMR, and gas sorption, the results were correlated to CO₂ adsorption kinetics. Route T produced fully crystalline SSZ-13 zeolite within 1 day with high yield, resulting in ultramicroporous materials through particle-mediate crystallization, transitioning from coarse spherical particles with high specific surface area (750 m² g⁻¹) and the highest equilibrium CO₂ adsorption capacity of 81.08 mg g⁻¹, to perfectly cubic structures for longer synthesis with decreased specific surface area (610 m² g⁻¹) and porosity. A disorder-to-order transition for synthesis longer than 3 days, along with the elimination of the interspaces internal, significantly decreased CO₂ adsorption capacity (63.03 mg g⁻¹). Meanwhile, SSZ-13 zeolites by Route L produced ultramicroporous crystalline particles only after 2 days, featuring intricate, layered structures formed by stacked sheets, indicating layer-by-layer mechanism. Longer synthesis times further increased particle complexity, reaching specific surface area of 858 m² g⁻¹ for the 4-day synthesis, along with improved CO₂ adsorption capacity. However, the CO₂ adsorption capacity for highly crystalline SSZ-13 samples obtained by Route L varied within 68.72–80.39 mg g⁻¹, suggesting that structural properties also influenced CO₂ adsorption performance. These findings demonstrate that conventional hydrothermal synthesis can rapidly produce SSZ-13 adsorbents, allowing fine-tuning material properties and CO₂ adsorption capacity by selecting the appropriate synthesis route.