The control questions

1. Methods of determining the chemical composition of crude oil and petroleum products

2. What devices refers to apparattam working with rectification?

3. Methods for determination of fractional composition of petroleum and petroleum products

4. The ring analysis and its purpose

5. The fractional composition of oil and its significance

Lecture 7

Oil heteroatomic compounds. Oxygen compounds of oil and gas. Naphthenic acids, their composition and content in the oil distribution distillates. Methods of isolation of naphthenic acids and their quantitative determination. Chemical characterization and structure determination of naphthenic acids, their application. Phenols.

Plan of the lecture

1. Types of heteroatomic compounds oil

2. Oxygen compounds oil

3. Distribution of oxygen compounds of petroleum fractions

1.With elemental analysis the carbon content of the total oil and hydrogen in it is lower than 100%. This is because the balance in the elements constituting the oil besides the basic elements (carbon and hydrogen) typically contains: oxygen, nitrogen, and sulfur forming oxygen, sulfur and nitrogen compounds. These compounds containing non-hydrocarbon elements in its composition, referred to heteroatom compounds.

Oxygenated hydrocarbons in petroleum are mostly represented acids, phenols, ketones and esters, lactones less anhydrides and furan compounds. They belong to various classes of compounds, their structure corresponds to the structure of the hydrocarbon oil fraction. The main part of the oxygenate compounds are concentrated in the higher boiling fractions ranging from kerosene. Scientists have shown that up to 90-95% of the oxygen necessary for resins and asphaltenes.

Among the compounds of oxygen should be noted naphthenic oil and oil acids, phenols, acid asfaltogennye; possible estolidy (complex products seal hydroxy acids), and is still quite unexplored oxygen compounds of asphaltenes and other components of resinous substances oil. Oxygen takes the following after sulfur heteroatoms place content in the oil.

Most of all, the oxygen in the resinous substances oil, where its content is 6 -7%. In tarry substances contained about 90% of oxygen oils; if we assume that the oil in the resinous material contained oxygen of 0.1 to 1%. It should be noted that the high resinous oils oxygen content amounts to 2%.

The next position after the resinous substances include oxygen compounds occupies naphthenic oil and acid, and finally, phenols; last found in such small quantities, and they have no practical value. Neutral oxygen compounds are also found in small quantities.

2. Oil acid. This term is established relatively recently, it shall mean all acids that make up the oil and its fractions. The term "acid oil" should be distinguished from the term "naphthenic acid", which refers to a cyclo pentane and cyclohexane carboxylic acid.

According to the chemical composition of the naphthenic acids are quite diverse. Their radicals contain naphthenic five or six-membered ring, which is often separated from the carboxyl group of one or more methylene groups. Furthermore, the ring itself can have methyl substituents. By increasing the molecular weight of naphthenic acid can comprise bi- or polycyclic nucleus. As all the carboxylic acids, naphthenic acids are capable of forming acid halides, amides, anhydrides, esters and join other reactions specific for this class of compounds.

Great interest from the practical point of view is salts of naphthenic acids. Most naphthenic acid salt does not crystallize and has a colloidal nature, and sometimes pasty consistency. Alkali metal salts are highly soluble in water and are used as technical soap (oil soap). Naphthenates, calcium and aluminum are thickeners in obtaining oils greases and lead naphthenates lubricants include as a component, operating under elevated pressure. Lead naphthenate, cobalt and manganese are used as desiccants (polymerization accelerators varnish) in the paint industry, copper naphthenate protect wood and fabrics from bacterial decomposition. Quite widely adopted are naphtenats of aluminum. They dissolved in turpentine is used as the lacquer, and a petrol dispersing ability to form gels and sols allow their use as a component of incendiary (napalm).

Naphthenic acid contained in the medium oil fractions. They were first isolated from the oil as early as 1861. In the most general form of the formula can be represented SnNmSOON. Since the beginning, these acids were isolated from naphthenic oils and subsequent studies have shown the content of these acids in the composition of the five-membered and six-membered naphthenic rings, the name - naphthenic acids more suitable.

Naphthenic acid fractions in the processing of them need to be removed because these corrosive acid react with metal oxides during heating and - with the metals themselves. Since naphthenic acids are readily form salts of lead, zinc, copper, iron and less even less aluminum.

The average content of oxygen in the oxygen-containing compounds include,%

Naphthenic acid…………………… 10

Phenols…………………………….. 5

Resin………………………………. 6

From this it can be calculated by taking the average content of 0,5% naphthenic acids, phenols and tars 0.05 15% on average 95%. Oxygen is necessary for the resin.

Phenols. Among the oxygenate content in oil phenols are second only to the acids.

The total content of phenols in the oil, as mentioned above, is small. Usually it is somewhat higher in the oils with a smaller quantity of naphthenic acids. Phenols are well separated by gas-liquid chromatography and can be identified by IR spectroscopy. In heavier product fractions are isolated in the form polycyclic phenols.

Ethers. The presence of esters in oil has been discovered in the last century. The bulk of the esters is concentrated in the fractions distilled above 370 ° C, and a heavy residue and can be up to 1.3% of these products. Studies of the composition concentrates esters selected from residues of certain heavy crudes, by infrared spectroscopy showed that they are rich.

3. In the medium- and high-boiling petroleum fractions acid represented mainly by naphthenic acids. The content of naphthenic acids is increased from kerosene to diesel and gas oil fractions, and then again in the oil fraction is reduced.

The greatest number of naphthenic acids account for the average fraction. In the higher boiling fractions decreases the content of these acids, but still can be identified sludge to 0.3% of naphthenic acids. Naphthenic acids are liquids or solids. The density of these acids decreases somewhat with increasing average molecular weight fraction. Iodine number increases and reaches a maximum acid number of the acid in the distillate vaseline and then decreases again. Naphthenic acids are to form water-soluble salts with alkalis. This property is based on a method for isolating them from the distillate. Upon acidification with sulfuric acid aqueous solution of alkali metal salts, naphthenic acid constitute separate (upper) layer in the free form. These salts are washed with good detergent properties (oil soap); 40% aqueous solution of these salts is used as a plant growth stimulator.

Distribution of naphthenic acids distillate oil shows that the main bulk of their accounts for diesel oil and light oil distillates. Gas substantially free acids, they are also a little kerosene, solar distillate but their number amounts to 2% or more. Subsequent distillates contain a smaller amount of naphthenic acids, although tar content thereof is 0.3%. Clearly, with increasing boiling point of the naphthenic acid content drops may be blocked due to destruction at high temperatures in the distillation.

IR spectra of some oils Tengiz shows absorption at 1710 cm-1, indicating the presence of structures containing oxygen.

The control questions

1. The main representatives of the oxygen-containing hydrocarbon oil

2. Chemical composition of naphthenic acids

3. Phenols, ethers. Methods for determination of oil content

4. The role of oxygen-containing hydrocarbon oil and petroleum products