Review on Naphthenic Acids: An Important Environmental Pollutants Caused by Oil Extraction and Industries

Naphthenic acids are a group of polar organic carboxylic acids that are present in crude oil naturally. They are cycloaliphatic carboxylic acids which have 10 to 16 carbons, which gained importance since the early twentieth century because of corrosion in oil refineries. Moreover, they are the most important environmental pollutants caused by oil extraction from oil sand reserves. Heavy crude oils which have high concentration of naphthenic acids are usually considered as poor-quality oil and sold at a lower price. Often, the high concentration of naphthenic acids in crude oil reduces the life of the equipment which are used in the exploration and refining process because of corrosion. Hence, researchers are increasingly interested in the chemical properties of naphthen-ic acids and the acidic components of the crude oils. The most popular methods for the identification and analysis of naphthenic acids are liquid and gas chromatography (GC), liquid-liquid extraction, Fourier transform infrared spectroscopy (FTIR), and solid-phase extraction (SPE). Naphthenic acids are the most important environmental pollutants caused by oil extraction from oil sand reserves. Previous studies have re-vealed that naphthenic acids can be absorbed by fish, but their distribution in different tissues of fish has not been specified. Experimental samples showed the highest toxici-ty to fish, while there was less toxicity to invertebrates and algae. Moreover, naphthen-ates have various industrial utilizations; they are used in synthetic detergents, corrosion inhibitors, lubricants, fuel and oil additives, wood preservatives, insecticides, fungi-cides, pesticides, wetting agents, napalm thickening agents, and oil desiccants that are utilized in painting and treating wood surfaces.

Automated summary

Naphthenic acids are organic carboxylic acids found naturally in crude oil, which have gained importance due to corrosion in oil refineries and being the most important environmental pollutants caused by oil extraction from oil sand reserves. Researchers are interested in their chemical properties and the acidic components of crude oil. Liquid and gas chromatography, liquid-liquid extraction, Fourier transform infrared spectroscopy, and solid-phase extraction are popular methods for their identification and analysis. Naphthenic acids have high toxicity towards fish but lower toxicity towards invertebrates and algae. They also have various industrial utilizations.