Lecture 4

General characteristics of the aromatic hydrocarbon content in the oil properties and path selection. Hydrocarbon hybrid and mixed structure. Content in petroleum fractions, their influence on the properties of oil.

Plan of the lecture

1. Characteristics of aromatic hydrocarbons

2. Characteristics of hydrocarbon hybrid structure

3. The distribution of aromatic hydrocarbons in petroleum fractions

1. Aromatic hydrocarbons in petroleum are represented by different rows of a number corresponding benzene hydrocarbons monocyclic, bicyclic naphthalene series, three or tetracyclic. Aromatic hydrocarbons increase with boiling petroleum fractions and, on average, up to 25% in the most high-boiling fractions. Since many oils paraffinic hydrocarbons disappear in higher fractions as the latter are considered a mixture of naphthenic and aromatic hydrocarbons.

Aromatic hydrocarbons (arenes) crudes typically contain smaller amounts compared to paraffinic and naphthenic hydrocarbons. In various oils total content of these hydrocarbons varies quite widely, averaging 10-20% (wt). In some crudes content may reach 35% (wt.) Or more. On the content of aromatic hydrocarbons in petroleum fractions can be divided into three classes. The first class is characterized in that aromatic hydrocarbons are concentrated mainly in the upper fractions. This class includes oil with a specific gravity of about 0.900. In these oils, aromatic hydrocarbons represented mainly polycyclic compounds.

The second class encompasses oil with a specific gravity of from 0.85 to 0.90. Aromatic hydrocarbons are more evenly distributed in all fractions with a maximum content accounted for middle fractions 250-450°. Oil first and second classes relate mainly to naphthenic and naphthenic - aromatic.

The third class of oils is characterized by a relative predominance of aromatic hydrocarbons in the light fraction to 300°. This class includes mainly methane oil. Since these oils nearly always much gasoline fractions can be said that this class predominate monocyclic and bicyclic aromatic hydrocarbons. In heavy gas oil, oil and higher oil fractions were also found and polycyclic arena, representatives of which are, in particular, the following hydrocarbons and their alkyl (mostly methyl) derivatives:

2. Hybrid naphthene - aromatic hydrocarbons. Naphthene aromatics hydrocarbons are well represented in the oil, especially in the higher fractions. They do not belong to the arena.

The simplest representatives of naphthene - aromatic hydrocarbons, homologs are present in kerosene - gas oil fractions, are:

Naphthene - aromatic hydrocarbons with one or two alicyclic rings can prevail over alkylbenzenes with the same number of carbon atoms.

Most hybrids contain condensed aromatic hydrocarbons and alicyclic rings. At the same time, found in oils and small amounts of non-condensable hydrocarbon type or phenylcyclohexane 1-cyclohexylethan -2- phenyl.

3. With increasing molecular weight fraction content arena in them increases. Aromatic hydrocarbons are more condensed. For gasoline fractions are characterized by the presence of almost all isomers of benzene homologues. The more saturated hydrocarbon molecule, and the more it is branched, the more of them is contained in the fraction. In the gasoline fraction present the simplest hydrocarbon hybrid - indan.

In kerosene fractions, aromatic hydrocarbons represented by benzene homologues but with longer hydrocarbon chains than gasoline fractions. Along with it, established the presence of naphthalene homologues. Kerosene - gas oil, diesel and lube arena presents homologous naphthalene and condensed aromatic hydrocarbons.

The control questions

1. The main components of aromatic hydrocarbons

2. Chemical and physical properties of aromatic hydrocarbons

3. Hybrid naphthene-aromatic hydrocarbons and their content in oil