NANOHYDROMECHANICS - Foundations of Nanotechnology: Pore Size in Carbon-Based Nano-Adsorbents - page 227

calculations and estimates of energy costs upon receipt of such media in different
ways and their application to problems of oil production.

5.2 PETROLEUM COMPOSITION
Chemically, oil is a complexmixture of hydrocarbons (HC) andcarbon compounds.
Itconsists of the followingelements:carbon (84-87%), hydrogen (12-14%), oxy-
gen, nitrogen, sulfur (1-2%). The sulfur contentcan reach up to3-5%. Oils can
contain the followingparts:a hydrocarbon, asvalto-resinous, porphyrins, sulfur
and ash. Oilhas adissolvedgas thatis released whenit comes to theearth's surface.
The main partof petroleumhydro carbons are different in their composition,
structure and properties, whichmay be ingaseous, liquidandsolid state. Depending
on thestructure of the molecules they are classified intothree classes-paraffinic,
naphthenicand aromatic.But a considerable proportionof oil ishydrocarbonsof
mixedstructurecontainingstructuralelements of all threeabove-mentioned classes.
The structure ofthe moleculesdetermines theirchemical and physical properties.
Carbonis characterized byits ability to formchains in whichthe atomsare con-
nected in serieswith each other. In remaining connections hydrogen atoms are
attached to the carbon. The number of carbon atoms in the molecules of paraffinic
hydrocarbons exceeds the number of hydrogen atoms twice, with some constant
excess in all the molecules equal to 2. In other words, the general formula of this
classof hydrocarbons is

C

n H

. Paraffinic hydrocarbonschemicallymore stable-

2 + n 2

and referto the limiting HC.
Depending on the numberof carbon atomsin the molecule hydrocarbons may-
be in one of the threestates of aggregation.
Thus, paraffin hydrocarbonsinoilcan be represented bygases, liquids and
solidcrystalline substances. Theyhave different effectson the propertiesof
oil:gasreduces viscosityandincreases the vapor pressure.
Fluidparaffinsdissolve wellinoilonly at elevated temperatures, forming a ho-
mogeneous mixture. Hardparaffins alsodissolve well inoilformingthe truemolecu-
lar mixtures. Paraffinhydrocarbons (with the exception of ceresin) can be easily
crystallized inthe form of platesand platestrips.
Naphthenic(tsiklanovae oralicyclic) hydrocarbonshavecyclic structure

( / ), to be exact, they arecomposed of severalgroups-CH 2 -interconnect-

edinringedsystem. Oil contains mainly naphthenes consisting off iveor six groups
of CH 2 .Allconnections of carbon and hydrogen are saturated, so then aphtheni
coil has stableproperties.Compared withparaffin, naphthenes have a higherden-
sityandlowervapor pressureandhave bettersolvent power.
Aromatic hydrocarbons (arena) are represented by the formula C n H n , are most
poor by hydrogen. The molecule has a form ofa ring with unsaturated carbon
connections. The simplest representative of this class of hydrocarbons is benzene
C 6 H 6 , which consists of six groups of CH 2 . For aromatic hydrocarbons a large
solubility, higher density and boiling point are typical.

C C

n H 2 n