Naphthenic acid (CAS: 1338-24-5 ) 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. The naphtha fraction of the crude oil refining is oxidized and yields naphthenic acid. The composition differs with the crude oil composition and the conditions during refining and oxidation.[1] Naphthenic acids are present in crude oil and leads to corrosion problems within the oil refineries, therefore "naphthenic acid corrosion" phenomena are well researched.[2][3] Crude oils with a high content of naphthenic acids are often referred to as high TAN (Total Acid Number) crude oils or high acid crude oil (HAC). There is also a conference called the High TAN Crude Conference which was first organized in 2005.
Mixtures of a flammable substance and naphthenic and palmitic acid aluminium salts were discovered during World War II to make napalm. These acids caused flammable hydrocarbons to gel.
Other uses of naphthenic acids depend on the refinement of the material. Naphthenic acids are used as a source material in the manufacture of corrosion inhibitors, wood preservatives, lubricant and fuel additives, driers for paints and inks, and in the production of metal soaps.
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Naphthenates are the salts of naphthenic acids. These salts have industrial applications including synthetic detergents, lubricants, corrosion inhibitors, fuel and lubricating oil additives, wood preservations, insecticides, fungicides, acaricides, wetting agents, and oil drying agents used in painting and wood surface treatment.
Industrially useful naphthenates include barium naphthenate, calcium naphthenate, cobalt naphthenate, copper naphthenate, lead naphthenate, magnesium naphthenate, manganese naphthenate, nickel naphthenate, sodium naphthenate, vanadyl naphthenate and zinc naphthenate.