Deacidification of naphthenic acids from petroleum crude oils using 2-methylimidazole in peg(400) with the aid of Ni/Ce/Al2O3 and Cu/Ce/Al2O3 catalysts [Deasidifikasi asid naftenik dari minyak mentah petroleum menggunakan 2-metilimidazola dalam peg(400) dengan bantuan pemangkin Ni/Ce/Al2O3 dan Cu/Ce Al2O3]

Abstract

The presence of carboxylic acid derivative compound in crude oil adversely contributes to major corrosion in oil pipelines and distillation units installed in crude oil refineries. The acidity level in crude oil is measured based on the total acid number (TAN). Methods that are commonly used to remove naphthenic acid (NA) from crude oil, such as dilution and caustic washing, have several drawbacks, including emulsion formation, high temperature, and massive use of solvent. In order to overcome these shortcomings, catalytic deacidification method had been developed to reduce the TAN value in acidic crude oil by using basic chemical, along with the aid of metal oxide catalyst. In this study, crude oil from Petronas Penapisan Melaka was evaluated. The parameters studied were reagent concentration, reaction temperature, catalyst loading, calcination temperature, and reusability of potential catalyst. The basic chemical used was 2-methylimidazole in polyethylene glycol (PEG 400) with concentrations of 100, 500, 1000, and 1500 ppm. Next, Ce was used as base for the catalyst with both Ni and Cu serving as dopant. The potential catalysts were characterised via Fourier transform infrared spectroscopy (FTIR) and thermogravimetry analysis (TGA) to determine their physicochemical properties. The outcomes showed that the Cu/Ce catalyst met the Petronas requirement as the TAN value reduced to 0.93 mg KOH/g from the original TAN value of 3.93 mg KOH/g. As for Ni/Ce catalyst, the TAN value reduced to 1.03 mg KOH/g. The TGA results revealed the total weight loss of Cu/Ce = 23.40% and Ni/Ce = 25.22% due to complete removal of impurities from the catalysts. The reaction temperature was set at 27 °C, while the catalyst calcination temperature was fixed at 1000 °C, and seven beads of catalyst loading had been employed. It can be concluded that catalytic deacidification method with the aid of Cu/Ce was indeed efficient in removing NA from the acidic crude oil, thus lowering the TAN value to less than 1 mg KOH/g.