Synthesis of binder-free pelletized Y zeolite for CO₂ capture

Y-type zeolites are widely used in the carbon dioxide (CO2) adsorption applications due to their exceptional ion exchange performance and high stability. However, the pelletization of Y powder by adding binders such as kaolin often results in performance drops, which has limited its industrial application. This study employs a zeolite-kaolin blend to produce cylindrical pelletized Y zeolite, in which the kaolin is then transformed to zeolites via hydrothermal crystallization, resulting in binder-free Y pellets. The Design-Expert software and the response surface method (RSM) are employed to optimize the hydrothermal crystallization conditions for binder transformation, with the objective of attaining a maximized capacity for CO2 adsorption. Results demonstrate that optimized synthesis conditions yield cylindrical Y zeolite with a notable CO2 adsorption capacity of 5.52 mmol/g at 298 K and 1 bar, surpassing that of the initial Y powder. The average crushing strength is 110 N per particle (Diameter x Height = 3 mm x 3 mm). The IAST selectivity of CO2/N-2 (15/85) is 824 at 298 K and 1 bar. The reaction mechanisms of the binder transformation are also investigated via experiments and DFT simulation. This study presents a simple and reliable method for manufacturing binder free Y zeolite, which is promising for carbon capture applications.