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.