Abstract

 
 
 
 For the purpose of extraction and identification of cyclic alkane hydrocarbons in oil from the Taribani field, Georgia, concentrates isolated from 200-350oC fractions have been studied. The concentrate preparation included the following steps: (a) distillation of a crude oil, (b) dearomatization of distillates by silica gel, (c) three-stage thermal diffusion separation of isoalkanes and cycloalkanes, and (d) thiourea adduction. Ten thermal diffusion fractions were obtained. A mixture of the IX and X fractions and separately the VIII fraction were studied. The extracts from these fractions with thiourea were studied as well. Composition of concentrates has been determined by the gas chromatography – mass spectrometry (GC-MS) method.The main components of the VIII thermodiffusion fraction were C11- C22 isoprenoid alkanes. Among them the predominant were pristane C19 and the phytane C20, the well-known biomarkers of oil. In the VIII thermodiffusion faction including dimethyl-, trimethyl-, tetramethyl-, ethyl-, methyl-ethyl-, diethyl-, propyl, methyl-propyl adamantanes, were identified.
 
 
 
Highlights
Naphthenic hydrocarbons make up the main part of petroleum hydrocarbons (40-60%)
Chromatograms of the thiourea extracts obtained from the naphthenic concentrate of the saturated distillation fractions of Taribani oil are shown in Figures 1 and 2
In Taribani oil 1-n- and 2-n-propyladamantanes, 1-methyl-3-propyl-adamantane, 1-n- and 2-n-butyladamantanes were detected that is confirmed with the corresponding mass-spectra for all derivatives the adamantly cation C10H15+ (m/z 135) is observed, as well as molecular ions C12H20+ (m/z 164) for ethyl, C13H22+ (m/z 178) for propyl, and C14H24+ (m/z 192) for butyl-derivatives are visible in spectra compared with the NIST database
Summary
Naphthenic hydrocarbons make up the main part of petroleum hydrocarbons (40-60%). They are the most interesting components, the presence of which determines the valuable chemical and technical properties of petroleum products. The complexity of the composition and structure of bi-, tri-, tetra- and pentacyclic naphthenes represented in them with different type of bonding of five- and six-membered rings (joined, condensed, bridged type, etc.) significantly increases These hydrocarbons, due to the variety of structural and spatial isomers, are the least studied hydrocarbons, with the. Interest towards the study of polycyclic naphthenes present in the middle fractions of petroleum was caused by the scarcity of information about these fractions and about the tri-, tetra- and pentacyclic alkanes present in them in the form of compact structure of C11-C16 composition Studies of these hydrocarbons in Georgian oils were carried out for the first time at the molecular level, with the aim of determining individual chemical compounds in oils with definite deciphering of their structure and spatial structure. Qualitative determination of polycyclic saturated hydrocarbons in the high-boiling fraction (200-350°C) of the Taribani oil
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