Naphthenic acids, structure

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. 

Oxygen can be present in naphthenic acids, phenols and furan (analogue structures to thiophene and pyrrole) and higher derivatives. Oxygenated compounds give rise to corrosion and product deterioration. Hydrodeoxygenation is particularly important in the upgrading of biomass. 

The naphthenic acids in crude oil are primarily monocarboxylic acids possessing an alkylated, cyclopentane single-ring structure. Fused ring, branched aliphatic and dicarboxylic acid compounds are also found in lower numbers. Most species contain 10 carbon atoms, but 20-carbon-atom species have been identified. 

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 are based on saturated single or inulticyclic condensed ring structures, The low molecular weight naphthenic acids contain alkylated cyclopentane carboxylic acids, with smaller amounts of cyclohexane derivatives occurring, The carboxyl group is usually attached to a side chain rather than directly attached to the cycloalkane, The simplest naphthenic... 

Copper Naphthenate. When naphthenic acids are neutralized with alkali, they react with a number of metal salts to form naphthen-ates. Because of its fungicidal properties, copper is normally the metal used. The naphthenic acids 2 are structurally variable (3). The... 

Yu Y, Lu X, Zhou Q et al (2008) Biodegradable naphthenic acid ionic liquids synthesis, characterization, and quantitative structure-biodegradation relationship. Chem Eur J 14 11174-11182... 

The napthanate is derived from naphthenic acid and is a mixture of molecular weight acids. No chemical structure is available. 

Napalm, A coprecipitated aluminum soap from naphthenic acids and the fatty adds of coconut oil devdoped early in 1942 (Fieser. Harris, Hershberg, Morgana, Novdlo, Putnam) for prepn of gasoline gels for incendiary munitions U.S. pats. 2,606,107 (1952) Herron, U.S. pat. 2,684,339 (1954 to Safety Fuel Chem. Corp ). The name was derived from the naphthenic and palmitic acids which are its major constituents. Structure and mfg problems Chem. Historical account L. F. Fieser, The Scientific Method (Rdnhold, New York, 1964) Bruce, Chemical Warfare—Flame in Kirk-Othmer Encyclopedia of Chemical Technology (Interscience, New York, 1964) p 888. 

Naphthenic acid corrosion Naphthenic acid pertains to a group of organic acids present in crude oil with the general chemical formula R (CH2) COOH, where R is one or more cyclopentane rings, and n is typically greater than 12. The ring structure can be tricyclic, tricyclic, or polycyclic. In addition, crude oil contains various other organic acids that contribute to acidity. These are often... 

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. 

The results of estimation of naphthenic acids for persistence, bioaccumulation and toxicity are presented in Table 2. The components of naphthenic adds are commonly classified by their structures and the number of carbon atoms in the molecule. 

Naphthenic acids are a by-product of oil refining. They are monocarboxylic acids of cyclic alkanes according to the following structure ... 

The need for alkaline conditions in the oil sand slurry has already been emphasized. The main role of the base (e.g., NaOH) is to produce (saponify) natural surfactants from the bitumen [45, 54], In the 1960s, Bowman and co-workers used foam fractionation and spectroscopic characterization of the isolated waxy material obtained to establish that the surfactants produced in the process are primarily carboxylic salts of naphthenic acids [67-69] with the possibility of sulfonic salts as well. Figure 10 shows an example of an early identification of the possible surfactant structure and illustrates the reaction of base with the acid form... 

Figure 10. Simplified representation of the structure of the naphthenic acids produced during hot water processing, compiled from the literature of the 1960s. (From Schramm et al. [102]. Copyright 1984, Alberta Oil Sands Technology and Research Authority.)...

Figure 12. Simplified formulae for the major structural types of naphthenic acids produced during hot water processing, as determined more recently. The total carbon numbers are likely to be about 14 to 16.

An FTIR method has also been developed for the determination of the naphthenic acids in oil sand process tailings [97]. In this method, a tailings sample is clarified by filtration (0.45 pm nominal pore size) then by ultrafiltration. Acidification to pH 2.5 with sulfuric acid ensures the acid form of all carboxylate functionalities and thus complete dissolution. The sample is then extracted with methylene chloride and evaporated to dryness. The naphthenic acid residue is dissolved in methylene chloride, the carbonyl stretching frequencies at 1708 and 1748 cm are observed and the corresponding absorbance values determined by FTIR. The method determines total organic carboxylates and therefore is sensitive to a broader range of structures than the carboxylate surfactants alone, but is sometimes used as an indicator of relative carboxylate surfactant concentrations, especially in studies of oil sand tailings pond samples. 

Figure 32. Source of naphthenic acids in oil sand processing and examples of the types of structures and the range of compounds included in the naphthenic acid group.

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]. 

Structurally the difference between PEN and PET is in the double (naphthenic) ring of the former compared to the single (benzene) ring of the latter. This leads to a stiffer chain so that both and are higher for PEN than for PET (Tg is 124°C for PEN, 75°C for PET is 270-273°C for PEN and 256-265°C for PET). Although PEN crystallises at a slower rate than PET, crystallization is (as with PET) enhanced by biaxial orientation and the barrier properties are much superior to PET with up to a fivefold enhancement in some cases. (As with many crystalline polymers the maximum rate of crystallisation occurs at temperatures about midway between Tg and in the case of both PEN and PET). At the present time PEN is significantly more expensive than PET partly due to the economies of scale and partly due to the fact that the transesterification route used with PEN is inherently more expensive than the direct acid routes now used with PET. This has led to the availability of copolymers and of blends which have intermediate properties. 

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