Unveiling the Superiority: Chlorosulfonic acid−functionalized Y zeolite as an efficient catalyst for lactic acid esterification

Esterification of lactic acid is a key reaction for producing biodegradable polymers and solvents. In this study, a chlorosulfonic acid-functionalized Y zeolite (ClHSO₃−Y) catalyst was developed using a simple excess impregnation method, yielding a mesoporous structure with enhanced acidity and stability. After functionalization, the mesoporous proportion of Y zeolite increased from 22 % to 60 %, improving reactant diffusion and boosting esterification efficiency. FTIR analysis confirmed the incorporation of chlorosulfonic acid, and NH₃-TPD showed strong acidity and a high number of acidic sites. The optimized ClHSO₃−Y catalyst achieved a 73.2 % lactic acid conversion in 5 min. Reaction parameters, including the ethanol−to−lactic acid ratio, catalyst loading, and temperature, were systematically optimized. This study demonstrates that ClHSO₃−Y offers high activity, excellent stability, and reusability, making it a promising candidate for sustainable lactic acid ester production.