Tuning zeolite properties through reflux time: Enhanced catalytic performance in esterification

NaA zeolite was synthesized using sodium silicate and sodium aluminate precursors via the reflux method at 80 °C with time variations of 1, 3, and 5 h, producing samples Z801H, Z803H, and Z805H. The influence of reflux time on the physicochemical properties and catalytic activity of the zeolites was systematically investigated. XRD and FTIR analyses confirmed a progressive transformation from amorphous aluminosilicate (1 h) to partially crystalline zeolite (3 h), and to highly crystalline NaA zeolite (5 h), with a consistent Si/Al ratio of 1.0 as determined by EDX. SEM micrographs revealed morphological evolution from amorphous gel to well-defined cubic NaA crystals. BET analysis showed that Z801H and Z803H were mesoporous with higher surface area (46.49 and 28.26 m2/g) and pore volume, while Z805H was microporous with very low surface area (1.28 m2/g). Acidity, measured by NH3 adsorption, followed the same trend, with Z801H exhibiting the highest acidity (1.22 mmol/g). Catalytic activity was tested in the esterification of acetic acid with butanol. The use of zeolite catalysts significantly enhanced ester yield compared to the non-catalyzed reaction (34.81%), with Z801H achieving the highest yield (75.95%). GC-MS confirmed butyl acetate as the main product. These results demonstrate that reflux time strongly governs zeolite structure, porosity, and catalytic performance.