ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Assaying of lube oil and petroleum distillation cuts for associated naphthenic acids and other selected properties

Festus M. Adebiyi, Odunayo T. Ore, and Faith A. Afe

Management and Toxicology Unit, Department of Biological Sciences, Elizade University, Ilara-Mokin, Nigeria

E-mail: fmbiyi@oauife.edu.ng

Received: 11 April 2022  Accepted: 7 October 2022

Abstract:

The occurrence of naphthenic acids (NAs) in crude oil and its fractional distillation cuts have been widely recognized to be a natural phenomenon. Despite this, they continue to generate wide interest due to the ecological and industrial concerns emanating from their toxicity and corrosion effects. In this study, refined petroleum products were assayed for their physical and chemical properties as well as associated NAs. The NAs were removed using the solvent extraction method and characterized using the gas chromatography–mass spectrometry technique. The total acid number and densities of the gasoline, kerosene, diesel, and lubricating oil samples were 9.37, 5.44, 12.45, and 5.72 mg KOH/g, and 0.63, 0.66, 0.72, and 0.75 g/cm³, respectively. In consonance with other estimated properties, it was observed that lubricating oil was the heaviest of the studied oil samples while gasoline was the lightest. This was attributed to the presence of more aromatic compounds in the lubricating oil sample. Although there were slight variations in the profiles of NAs from sample to sample, they generally contained degree of unsaturation (z), z = 0 to z = − 16 compounds with a high predominance of aliphatic naphthenic acid types. The carbon numbers of the NAs detected in the oil samples ranged from 8 to 15. The estimated carbon preference index (CPI) indicated that the lubricating oil sample may have emanated from biogenic contribution (CPI >  > 1) while the other samples likely emanated from petrogenic sources (CPI < 1). The even–odd carbon ratio (E/O) indicated that there is no carbon preference among the studied oil samples.

Keywords: Corrosion; Crude oil; Density; Naphthenic acids; Refined petroleum products; Total acid number

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-022-02531-3

Chemical Papers 77 (2) 921–934 (2023)