Naphthenic acids (NA) are a mixture of several cyclopentyl and cyclohexylcarboxylic acids with a molecular weight of 120 to 700 or more atomic mass units. The main fraction are carboxylic acids with a carbon skeleton from 9 to 20 carbon atoms. Scientists claim that naphthenic acids (NA) are cycloaliphatic carboxylic acids with 10-16 carbon atoms, although acids containing up to 50 carbon atoms have been found in heavy oils.
Etymology
The term has its roots in the somewhat archaic term "naphthene" (cycloaliphatic but non-aromatic), which is used to classify hydrocarbons. It was originally used to describe a complex mixture of petroleum-based acids when analytical methods available in the early 1900s could only identify a few with accuracy.naphthenic type components. Today, naphthenic acid is used more generally to refer to all carboxylic acids present in petroleum (whether cyclic, acyclic, or aromatic compounds) and carboxylic acids containing heteroatoms such as N and S. Numerous studies have shown that most cycloaliphatic acids also contain straight and branched chain aliphatic acids and aromatic acids. Some acids contain > 50% combined aliphatic and aromatic acids.
Formula
Naphthenic acids are represented by the general formula CnH2n-z O2, where n is the number of carbon atoms and z is the homologous series. The z-value is 0 for saturated acyclic acids and increases to 2 in monocyclic acids, to 4 in bicyclic acids, to 6 in tricyclic acids, and to 8 in tetracyclic acids.
S alts of acids called naphthenates are widely used as hydrophobic metal ion sources in a variety of applications. The aluminum and sodium s alts of naphthenic acid and palmitic acid were combined during World War II to make napalm. And napalm was successfully synthesized. The word "napalm" comes from the words "naphthenic acid" and palmitic acid".
Oil connection
The nature, origin, extraction and commercial use of naphthenic acid have been studied for quite some time. It is known that crude oil from fields in Romania, Russia, Venezuela, the North Sea, China and West Africacontains a large amount of acidic compounds compared to most US crude oil. The carboxylic acid content of some Californian petroleum products is particularly high (up to 4%), where the most common classes of carboxylic acids are reported to be cycloaliphatic and aromatic acids.
Composition
The composition varies depending on the composition of the crude oil and the conditions during processing and oxidation. Fractions that are rich in naphthenic acids can cause corrosion damage to refinery equipment, so the acid corrosion (NAC) phenomenon has been well studied. High acid crude oil is often referred to as high total acid number (TAN) crude oil or high acidity crude oil (HAC). Naphthenic acids are a major contaminant in water from the extraction of oil from the Athabasca oil sands (AOS). Acids have both acute and chronic toxicity to fish and other organisms.
Environmental
In his oft-cited paper published in Toxicological Sciences, Rogers stated that naphthenic acid mixtures are the most significant environmental pollutants from oil sands production. They found that under worst-case conditions, acute toxicity is unlikely for wild mammals exposed to acids in the water, but repeated exposure may have adverse he alth effects.
In his 2002 articlecited over 100 times, Rogers et al reported a solvent-based laboratory procedure designed to efficiently extract acids from large volumes of Athabasca Oil Sands Tailings Pond (TPW) water. Naphthenic acids are present in AOS Tailings Water (TPW) at an estimated concentration of 81 mg/L, too low a level for TPW to be considered a viable source for commercial recovery.
Delete
Naphthenic acid is removed from petroleum substances not only to minimize corrosion, but also to recover commercially useful products. The largest current and historical use of this acid is in the production of metal naphthenates. Acids are extracted from petroleum distillates by alkaline extraction, regenerated in an acid neutralization process, and then distilled to remove impurities. Acids sold commercially are classified by acid number, impurity level, and color. Used to produce metal naphthenates and other derivatives such as esters and amides.
Naphthenates
Naphthenates are acid s alts analogous to the corresponding acetates, which are better defined but less useful. Naphthenates, like the naphthenic acids in petroleum, are highly soluble in organic media such as paints. They are used in industry, including the production of such useful things: synthetic detergents, lubricants, corrosion inhibitors, fuel and lubricating oil additives, preservativesfor wood, insecticides, fungicides, acaricides, wetting agents, napalm thickeners and oil desiccants used in painting and wood surface treatment.
Oil sands
One study states that naphthenic acids are the most active environmental pollutant of all substances derived from the extraction of oil from oil sands. However, under conditions of leakage and contamination, acute toxicity is unlikely to occur in wild mammals exposed to acids in tailings pond water, but repeated exposure may have adverse animal he alth effects. Acids are present in oil sands and tailings water at an estimated concentration of 81 mg/L.
Using the Organization for Economic Co-operation and Development (OECD) protocols for toxicity testing, US researchers argued that, based on their studies, purified NAs, when taken orally, were not acutely genotoxic to mammals. However, damage caused by NDT from short-term exposure during acute or intermittent exposure may accumulate with repeated exposure.
Cyclopentane
Cyclopentane is a flammable alicyclic hydrocarbon with the chemical formula C5H10 and CAS number 287-92-3, consisting of a ring of five carbon atoms, each bonded to two hydrogen atoms above and below the plane. It is often presented in the formcolorless liquid with an odor similar to gasoline. Its melting point is -94°C and its boiling point is 49°C. Cyclopentane belongs to the class of cycloalkanes and are alkanes with one or more rings of carbon atoms. It is formed by cracking cyclohexane in the presence of alumina at high temperature and pressure.
The production of naphthenic acids, including cyclopentane, has lost its former mass character in recent years.
It was first prepared in 1893 by the German chemist Johannes Wieslikus. Recently, it is often referred to as naphthenic acids.
Role in production
Cyclopentane is used in the production of synthetic resins and rubber adhesives, and as a blowing agent in the production of polyurethane insulating foam, which is found in many household appliances such as refrigerators and freezers, replacing environmentally harmful alternatives such as CFCs -11 and HCFC- 141b.
Multiple Cyclopentane Alkylation (MAC) lubricants have low volatility and are used in some specialized applications.
The United States produces more than half a million kilograms of this chemical per year. In Russia, naphthenic acids (including cyclopentane) are produced as a natural product of oil processing.
Cycloalkanes can be made using a process known as catalytic reforming. For example, 2-methylbutane can be converted to cyclopentane using a platinum catalyst. This is especially used incars, as branched alkanes will burn much faster.
Physical and chemical characteristics
Surprisingly, their cyclohexanes start to boil 10 °C higher than hexahydrobenzene or hexanaphthene, but this riddle was solved in 1895 by Markovnikov, N. M. Kishner and Nikolai Zelinsky when they repurposed hexahydrobenzene and hexanaphthene as methylcyclopentane - the result of an unexpected backlash.
Although rather non-reactive, cyclohexane undergoes catalytic oxidation to form cyclohexanone and cyclohexanol. A mixture of cyclohexanone-cyclohexanol, called "KA oil", is the raw material for adipic acid and caprolactam, precursors of nylon.
Application
It is used as a solvent in some brands of correction fluid. Cyclohexane is sometimes used as a non-polar organic solvent, although n-hexane is more commonly used for this purpose. It is also often used as a recrystallization solvent, as many organic compounds exhibit good solubility in hot cyclohexane and poor solubility at low temperatures.
Cyclohexane is also used to calibrate differential scanning calorimetry (DSC) instruments due to the convenient crystal-to-crystal transition at -87.1 °C.
Cyclohexane vapors are used in vacuum carburizing furnaces in the manufacture of heat treatment equipment.
Deformation
A ring with 6 vertices does not match the shape of a perfect hexagon. The planar hexagon conformation has significant angular strain because its bonds are not 109.5 degrees. Torsional deformation will also be significant as all bonds will be eclipsed.
Therefore, in order to reduce torsional deformation, cyclohexane adopts a three-dimensional structure known as "conformational chair". There are also two other intermediate conformers - "half chair", which is the most unstable conformer, and "twist boat", which is more stable. These eccentric names were first proposed as early as 1890 by Hermann Sachs, but gained wide recognition much later.
Half of the hydrogen atoms are in the plane of the ring (equatorially), and the other half are perpendicular to the plane (axially). This conformation provides the most stable cyclohexane structure. There is another conformation of cyclohexane, known as the "conformational boat", but it will convert to a slightly more stable "stool" formation.
Cyclohexane has the lowest angle and torsional strain of all cycloalkanes, resulting in cyclohexane being considered 0 in total ring strain. The same is true for sodium s alts of naphthenic acids.
Phases
Cyclohexane has two crystalline phases. High temperature phase I, stable between +186 °C and temperaturemelting point +280 °C, is a plastic crystal, which means that the molecules retain some degree of freedom of movement. The low-temperature (below 186°C) phase II is more ordered. The other two low-temperature (metastable) phases III and IV were obtained by applying moderate pressures above 30 MPa, and phase IV appears exclusively in deuterated cyclohexane (note that the application of pressure increases all transition temperatures).
