DOI: https://doi.org/10.55373/mjchem.v28i2.278

Keywords: Green Chemistry, water removal, molecular sieve, solvent-free, non-catalyzed

Abstract

Esterification is constrained by its reversible nature, where water accumulation suppresses ester formation and promotes hydrolysis of esters and anhydrides. Although water removal strategies are well established in catalyzed and solvent-based systems, their role in uncatalyzed, solvent-free systems (SFS) remain underexplored. This study investigates the use of molecular sieves (MS) for in situ water removal to overcome equilibrium limitations and enhance ester production in a catalyst-free SFS, consistent with green chemistry principles. Batch esterification of isoamyl alcohol with acetic anhydride was conducted using 3 Å and 4 Å MS to examine the effects of adsorbent type, loading (0–10% w/v), temperature (50–80 °C), and reactant molar ratio (2:1–3:1). Incorporation of MS markedly improved yield: without adsorbent, ester concentration reached 2.87 mol/L after 360 min, whereas 6% 3A MS increased yield to 3.81 mol/L (33% enhancement). Reaction acceleration was also evident, with 2.53 mol/L achieved in 75 min using 4% MS compared to 135 min without. While higher temperatures favored ester formation, adsorption efficiency declined above 70 °C. Notably, a 2:1 molar ratio with MS achieved yields comparable to a 3:1 ratio without, demonstrating reduced reliance on excess alcohol. This approach provides a practical, sustainable route to intensify esterification.