STUDY OF SURFACE KINETIC MODELS FOR FATTY ACID ESTERIFICATION TO ESTERS USING ACIDIC HETEROGENEOUS CATALYST

Abstract

Fatty acid esterification behavior with varying reaction parameters such as; reaction temperature, alcohol to fatty acid molar ratio, catalyst concentration, and fatty acid carbon chain length have been investigated in a batch reactor system. Compared experimental data of acetic and oleic acid esterification using Langmuir Hinshelwood Hougen-Watson (LHHW) and Eley Rideal (ER) surface reaction kinetic models. Amberlyst 15 dry acidic resin surface considered as standard. Esterification of fatty acids increases with increase in reaction temperature and catalyst concentration. The lower molar ratio in a reaction mixture initially increases conversion but a higher molar ratio gives better reaction conversion over longer reaction time. Carbon chain length of fatty acid has an important effect on esterification, a higher percent conversion was observed with shorter chain length fatty acid in a short reaction time under constant reaction parameters. A maximum esterification of 67.1% and 41.6% was observed for acetic and oleic acids, respectively. Surface reaction was found the rate limiting step for the two fatty acid esterification. ER model for acetic acid with a reaction rate constant k = 4.31/min, proved to be applicable (R2 ≥ 0.94) more accurately on the experimental data than a LHHW model with k= 0.174/min (R2 ≥ 0.92). The opposite kinetic pattern was observed for oleic acid esterification with the rate constant k = 0.197/min (R2 ≥ 0.79) for ER model and 0.263/min (R2 ≥ 0.79) for LHHW model. Determination of reaction rate constants from heterogeneous surface reaction kinetic models should be helpful for designing of scale up esterification reactors.