Optimization of Oleic Acid Esterification with Butanol, Hexanol, and Octanol: Effect of Catalyst, Molar Ratio, and Temperature

Esterification reactions between carboxylic acids and alcohols, catalyzed by acids or bases, yield esters and water as a byproduct. These reactions hold significant industrial relevance, as esters are widely used in the production of lubricants, plasticizers, coatings, solvents, flavors, pharmaceuticals, cosmetics and biofuels. Environmental concerns regarding the spillage or improper disposal of mineral oils have heightened the demand for renewable and environmentally benign alternatives such as biolubricants, which are derivated from vegetable oils. This study investigates the influence of the oleic acid to butanol molar ratio, reaction temperature, time, and catalyst type in the production of butyl oleate and assess the best conditions for the production of methyl, ethyl, hexyl and octyl esters. Molar ratios of 1:3, 1:6 and 1:9 (oleic acid to butanol) were tested at reaction temperatures of 60, 80, 100 and 120 °C. Catalysts evaluated included H2SO4, AlCl3, Fe2(SO4)3 and APTS (p-toluenesulfonic acid), each at 1 wt % relative to oleic acid. Optimal conditions for producing butyl oleate were identified as a molar ratio of 1:6, a temperature of 80 °C, and 1 wt % H2SO4, affording a 92.3 ± 0.2% yield after 6 h. Hexyl and octyl oleates were obtained in yields of 92.8 ± 0.1% and 94.8 ± 0.1%, respectively, under conditions of 2.5 wt % H2SO4, 1:3 molar ratio, 80 °C, and 2 h reaction time. Determining the optimal conditions for these alkyl oleates is important for future studies on their potential applications as biolubricants.