Naphthenic acid
Naphthenic acid (CAS: 1338-24-5 ) (NAs)is the name for an unspecific mixture of several cyclopentyl and cyclohexyl carboxylic acids with molecular weight of 120 to well over 700 atomic mass units. The main fraction are carboxylic acids with a carbon backbone of 9 to 20 carbons. McKee et al. claim that "naphthenic acids (NAs) are primarily cycloaliphatic carboxylic acids with 10 to 16 carbons." Salts of naphthenic acids, which are naphthenates, are widely used as hydrophobic sources of metal ions in diverse applications.
They are obtained by oxidation of the naphtha fraction of the crude oil refining. The composition varies with the crude oil composition and the conditions during refining and oxidation. Naphthenic acids are present in crude oil. Fractions that are rich in naphthenic acids can cause corrosion damage to oil refinery equipment; the phenomenon of naphthenic acid corrosion (NAC) has therefore been well researched. Crude oils with a high content of naphthenic acids are often referred to as high total acid number (TAN) crude oils or high acid crude oil (HAC). Naphthenic acids are the major contaminant in water produced from the extraction of oil from Athabasca oil sands (AOL). Naphthenic acids have both acute and chronic toxicity to fish and other organisms.
They can be extracted from aqueous solution.
Naphthenates are the salts of naphthenic acids. Analogous to the corresponding acetates, which are better defined but less lipophilic. Metal naphthenates are coordination complexes. They have the formula M(naphthenate)2 or are basic oxides with the formula M3O(naphthenate)6. The naphthenates are highly soluble in organic media. They have industrial applications including synthetic detergents, lubricants, corrosion inhibitors, fuel and lubricating oil additives, wood preservatives, insecticides, fungicides, acaricides, wetting agents, thickening agent of napalm and oil drying agents used in painting and wood surface treatment. Industrially useful naphthenates include those of aluminium, magnesium, calcium, barium, cobalt, copper, lead, manganese, nickel, vanadium, and zinc.
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