Optimization of the Removal of Naphthenic Acids from Crude Oil via Catalytic Esterification

This study was carried out to ascertain the optimum parameters for maximum total acid number (TAN) reduction via catalytic esterification using chicken eggshell ash as catalyst. A central composite design (CCD) was created to optimize TAN reduction by varying temperature and catalyst weight %. The chicken eggshell ash was calcined and reactivated in a furnace at 900 °C for an hour. An oil solution (referred to as synthetic solution) of diesel was adulterated with the organic acid m-toluic which served as a representation for highly acidic oil. Titration using alcoholic potassium hydroxide (KOH) and an indicator (phenolphthalein) was used to deduce the total acid number of the synthetic solution before and after esterification. The optimum parameters for maximum TAN reduction obtained from the model were a temperature of 56.90 °C, a catalyst weight % of 11.45%, and a maximum TAN reduction of approximately 94%. Fourier Transform Infrared (FTIR) Spectroscopy also confirmed that TAN reduction had taken place as the peaks that represent the carbonyl group (C=O stretch at ~1605 cm-1) was reduced significantly.