Naphthenic acid , complexes

Naphthenic acids, complex carboxylic acids that are believed to have a cyclopentane ring or cyclohexane ring in the molecule, occur in petroleum. They seem to be of little consequence enviromnentally since thermal decarboxylation can occur during the distillation process. During this process, the temperature of the crude oil in the distillation column can reach as high as 395°C (740°F). Hence decarboxylation is possible (Speight and Francisco, 1990) ... 

The use of carboxylic acids for the removal of iron(III) from solutions of the rare-earth metals has been reported,38 but has not been described in detail. The stoichiometries of the extracted complexes of iron(III) have not been clearly established. The n-decanoic acid complex has been variously described as (FeA3)3 and Fe3A9 x(OH) (HA) 51 or [Fe(OH)A2]2 and [Fe(OH)2A-HA]2,57 the H-octanoic acid complex as (FeA3-H20)3,58 the naphthenic acid complex as FeA3,47 and that of Versatic 10 acid as [FeA3(HA)J>, or [Fe(OH)A2]3.59... 

Copper quinolinolate (oxine copper) is the chelate of divalent copper and 8-hydroxyquinoline and shares most of its market with copper naphthenate, which is a complex copper salt of mixed naphthenic acids. The principal uses are in wood treatments and some military textiles, where the green color is not objectionable. Copper naphthenate has an odor but is cheaper than oxine. Both copper naphthenate and 2inc naphthenate have performed well in environment tests, with exposure to soil above-ground, as well as concrete (33). 

The term naphthenic acid, as commonly used in the petroleum industry, refers collectively to all of the carboxyUc acids present in cmde oil. Naphthenic acids [1338-24-5] are classified as monobasic carboxyUc acids of the general formula RCOOH, where R represents the naphthene moiety consisting of cyclopentane and cyclohexane derivatives. Naphthenic acids are composed predorninandy of aLkyl-substituted cycloaUphatic carboxyUc acids, with smaller amounts of acycHc aUphatic (paraffinic or fatty) acids. Aromatic, olefinic, hydroxy, and dibasic acids are considered to be minor components. Commercial naphthenic acids also contain varying amounts of unsaponifiable hydrocarbons, phenoHc compounds, sulfur compounds, and water. The complex mixture of acids is derived from straight-mn distillates of petroleum, mosdy from kerosene and diesel fractions (see Petroleum). 

Oxygen levels in the VGO parallel the nitrogen content. Thus, the most identified oxygen compounds are phenols and carboxyUc acids, frequendy called naphthenic acids. These may account for from ppm to neady 3% of a VGO. The presence of numerous complex naphthenic and naphtheno aromatic acid stmctures in cmde oils, especially immature forms, has been shown (34). Among the different stmctures a number of specific steroid carboxyUc acids have been identified. 

Oxygen compounds in crude oils are more complex than the sulfur types. However, their presence in petroleum streams is not poisonous to processing catalysts. Many of the oxygen compounds found in crude oils are weakly acidic. They are carboxylic acids, cresylic acid, phenol, and naphthenic acid. Naphthenic acids are mainly cyclopentane and cyclohexane derivatives having a carboxyalkyl side chain. 

Most of the inhibitors in use are organic nitrogen compounds and these have been classified by Bregman as (a) aliphatic fatty acid derivatives, b) imidazolines, (c) quaternaries, (d) rosin derivatives (complex amine mixtures based on abietic acid) all of these will tend to have long-chain hydrocarbons, e.g. CigH, as part of the structure, (e) petroleum sulphonic acid salts of long-chain diamines (preferred to the diamines), (/) other salts of diamines and (g) fatty amides of aliphatic diamines. Actual compounds in use in classes (a) to d) include oleic and naphthenic acid salts of n-tallowpropylenediamine diamines RNH(CH2) NH2 in which R is a carbon chain of 8-22 atoms and x = 2-10 and reaction products of diamines with acids from the partial oxidation of liquid hydrocarbons. Attention has also been drawn to polyethoxylated compounds in which the water solubility can be controlled by the amount of ethylene oxide added to the molecule. 

Naphthenic acids and sulfur- and nitrogen-containing heterocycles and naphthenoaromatic compounds can all be found in distillate fuel fractions. Degradation through condensation type reactions rather than through free-radical-initiated polymerization can be more common in distillate fuel. Because of this, degradation products are often quite complex in nature and structurally diverse. 

Naphthenic Acids Acids derived from crude oil which are usually monocarboxylic, monocyclic, and completely saturated. Many are derivatives of cyclopentane and more complex alicyclic ring systems. 

Straight-chain alkyl carboxylic acids derived from petroleum that also have a terminal cyclohexyl or cyclopentyl group are known as naphthenic acids. They form complexes, presumably polymeric, with many transition metals, and these compounds are freely soluble in petroleum. Copper naphthenates are used as fungicides, aluminum naphthenate was used as a gelling agent in napalm, and cobalt naphthenates are used in paints. 

Pyhala (68) reports that distillates from two Russian petroleums contained 11 to 12 times as much naphthenic acids as the undistilled crude oils, indicating that, like the nitrogen bases, the naphthenic acids are mainly thermal decomposition products of more complex materials. 

The products formed vary somewhat with the catalyst and the temperature employed, but in general represent all the stages of the oxidation of aliphatic hydrocarbons from alcohols to oxygenated acids, together with hydrocarbons and oxidized bodies resulting from secondary reactions. Alcohols, ketones, aldehydes, naphthenic acids and other substances formed make up a mixture of such complexity that quantitative analysis, even, is a hopelessly complicated task. 0... 

High-temperature crude corrosion is a complex problem. There are at least three mechanisms (i) furnace tubes and transfer lines where corrosion is dependent on velocity and vaporization and is accelerated by naphthenic acid (ii) vacuum column where corrosion occurs at the condensing temperature, is independent of velocity, and increases with naphthenic acid concentration (iii) side-cut piping where corrosion is dependent on naphthenic acid content and inhibited somewhat by sulfur compounds. 

Corrosion by naphthenic acid some organic acids, those having a naphthenic structure, together with iron, give rise to complex salts and, at temperatures between 200°C and dOO C, are particularly aggressive for carbon steels and low-alloy steels. 

In general, the complex and changing nature of mixtures of naphthenic acids make it difficult to predict toxicity. By determining the critical mechanism of toxicity of naphthenic acids, it might be possible to develop more effective predictive relationships to account for the toxic effects observed in living organisms exposed to naphthenic acids. 

Several methods have been developed specifically for naphthenic acids, a class which includes the surface active carboxylate surfactants. Naphthenic acids are present as a complex mixture of a number of homologues with only a small range in molar mass (166-450 mol/g), little change in solubility character, and have been difficult to assay using conventional analytical methods. Methods such as negative ion-mode mass spectrometry using fast atom bombardment (FABMS), have been successfully applied to the analysis of naphthenic acid mixtures [93, 94], Other promising techniques include fluoride ion chemical ionization mass spectrometry (FI-MS) [95], and electrospray ionization mass spectrometry (ESIMS), which may allow for the quantification of the various naphthenic acid fractions [96]. 

Preston (1985) described the solvent extraction behavior of a large number of metal cations including rare earth nitrates in solutions of Versatic 10 (2-ethyl-2-methylheptanoic acid), naphthenic, 2-bromodecanoic and 3,5-diisopropylsalicylic acids in xylene. The last two acids extract metal cations under more acidic conditions, pH 1-2. For Versatic 10 the order of extraction of yttrium and lanthanides is La < Ce < Nd < Gd < Y < Ho < Yb and for naphthenic acids it is La < Ce < Y < Nd < Gd k Ho Yb. The lanthanides tend to form complexes of predominantly ionic nature. In the case of Versatic 10, the stability of the complexes increases uniformly with atomic number due to the increase in electrostatic energy as a result of the decrease in ionic radius. The primary branched naphthenic acid allows the formation of complexes with high coordination number, nine for La to Nd, eight and eventually six as the metal ionic radius decreases. In general, the extraction of a metal ion by a carboxylic acid H2A2 can be represented by the reaction... 

The inhibitors most widely used in petroleum refining contain nitrogen bases such as amines, diamines, imadazolines, pyrimidines, and their salts, or complexes with fatty acids, naphthenic acids, and sulfonates. Inhibitors vary in solubility, etc., as mentioned above and also must be chosen in consonance with pH range and other fluid properties. 

The most common accelerators for methyl ethyl ketone peroxide and cyclohexanone peroxide are salts of metals which exhibit more than one valency. The most widely used metal of this kind is cobalt, although salts of cerium, iron, manganese, tin and vanadium also find some application. In order to be effective as an accelerator a metal salt must be soluble in the polyester resin. The most commonly used salts are naphthenates, which are readily soluble octoates also may be used. (Naphthenic acid is extracted from the gas oil and kerosene fractions of petroleum and consists of a complex mixture of carboxylic acids of substituted cyclopentanes and cyclohexanes. ) The decomposition of a hydroperoxide (ROOH) by a metal salt such as cobalt naphthenate to give free radicals proceeds according to the following chain reaction ... 

The process of desalting in Oil Refining Process usually involves addition 1-20% (w.) of wash water to the crude oil, mixing to form a W/O emulsion and then subjecting the emulsion to electrostatic demulsification or hydrocydone treatment (Goyal, 1993, Varadaraj et al., 2001). Most crude oils that contain asphaltenes and naphthenic acids, especially heavy crude oils form marine environments trend to form stable W/O emulsions, which are complex scattered systems (Kumar et al., 2001). 

Naphthenic acid is a kind of organic acid in crude oils and has a saturated ring structure. Its content is typically measured and indirectly expressed by non-aqueous titration with potassium hydroxide (mg KOH per 100 ml for clean oils) or total acid number (TAN, as milligrams of KOH required to neutralize the acid in one gram of oil). Naphthenic acid in crude oils is a rather complex mixture. Its molecular weight ranges from 180 to 700, mainly from 300 to 400 [4]. 

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