Crude oil, also known as black gold, is a complex mixture of hydrocarbons found in sedimentary rocks. It is believed to have formed from the remains of ancient plants and animals over millions of years. Crude oil is composed mainly of paraffin hydrocarbons, along with other components like naphthenes, aromatics, asphaltenes and various chemical elements. The four main categories of hydrocarbon types in crude oil are paraffins, olefins, naphthenes and aromatics, which have varying molecular structures and properties. Crude oil can also contain small amounts of sulfur, nitrogen, oxygen and heavy metal compounds.

1. Basic of Petroleum

2. Petroleum or Crude oil
 Crude oil, also known as Black gold, is a thick, dark brown
or greenish flammable liquid, which is found in the upper
strata of some regions of the Earths crust.
 It is a complex mixture of various hydrocarbons, along with
traces of other chemicals and compounds.
 Crude oil can be categorized as Sour crude( sulfer content
less than 0.5% ).

5. ORIGIN OF PETROLEUM
 Based on two theories
1) Organic theory
2) Inorganic theory
 Organic theory
 95 % scientists believes in organic theory.
 Organic theory commands that the oil and gas are formed from the remains of plants, animals and
insects.
 Some believe it is formed from the dinosaurs.
 Some believe it is due to marine organism.
 Some believe in convergence of phytoplankton into petroleum.

6. Composition of Petroleum
• Occur in all possible states and varies colour from light brown to dark
brown or black, exhibiting luminescence in some case.
• It is a mixture of various hydrocarbon, homologues series namely
paraffin’s, naphthenes and aromatic.
• Main element is C= 84-86%
H= 11-14%
(O2, N2, S)= 8%
Metal Traces.
• Petroleum is more homogenous than coal and occur mostly in
sedimentary rocks.

7. Composition of Petroleum
 Paraffins
Olefins
Alkynes
Diolefins
Naphthanes
Aromatics
Inorganics
Oxygen and Nitrogen
Asphalts, resins and bitumens

8. Paraffins
 General formula: CnH2n+2
First three compounds are gases and upto C16 are liquid and beyond that
are semisolids.
Beyond C30, solid blocks are even crystalline forms.
There are number of isomeric compounds for each compounds.
Specific gravity of the series increase with MW.
 Less Specific gravity and Boiling Point than aromatics.
 Viscosity of paraffins is less.
 Stable, not attacked by sulphuric acid or other oxidizing agents
 Higher paraffins are very much insoluble in water;
While lower ones are soluble in ethers and alcohols.

9. Unsaturated (Olefins)
General formula: CnH2n
Olefins do not naturally occur in crude oil but are formed during
cracking operation
First four are gases and upto C15 are liquid and beyond that are
solids.
Boiling Points of olefins are generally lower by few degree than the
saturated compounds of the same carbon number.
Chemically different than paraffin’s
Easily attacked by sulfuric acid. And some of them are polymerize.
Do not appear in measurable quantities.

10. Alkynes (Acetylenes and Properties)
• General formula: CnH2n-2
• Acetylenes yield crystalline compounds with ammonical solution of
copper salts.
• Easily Attacked by sulfuric acid.
• These are isomeric with diolefins.
• Diolefins: CnH2n-2
• Diolefins are produced during cracking reaction.
• Distinguished by acetylenes as they do not form salts with ammonical
solution of copper salts.

11. Naphthenes
General formula: CnH2n
These are saturated ring compounds.
Cycloparaffin hydrocarbons in which all of the available bonds of the
carbon atoms are saturated with hydrogen are called napthenes.
Exhibit both the properties of saturated and unsaturated.
All the properties are in between.

12. Aromatics
First smallest aromatics : benzene followed by toluene, xylene, and
cumene.
High Boiling Point
Burn with red flame with much shoot.
As these behave like saturates, they resist oxidation.

13. Inorganics
Sulfur compounds.
Sulfur in the form of free sulfur, hydrogen sulfide, mercaptans and
thiophenes etc.
Occupy prominent position due to corrosion and odour.
Petroleum is considered "sour" if it contains more than 0.5% sulfur
(or 1% by certain definitions), and "sweet" if it contains less than 0.5%
sulfur.

14. Oxygen and Nitrogen
• Do not occur in free state.
• Oxygen occurs as oxygenated compounds like phenols, cresols, naphthenic acids,
sulphonates, sulphates and sulfoxides.
• Nitrogen presence in form of natural gas only.
• Nitrogen exists in the form of indoles, pyridines, quinolines, and amines below
2%.
• Create problem in processing and stability of products
• Catalyst deactivation or poisoning and gum formation (insoluble solids) are some
offshoots of nitrogen.
• Nitrogen present in two form basic and non basic.
• Nitrogen pigment impart color to crude and fractions.
• Compound of nitrogen : Porphyrins

15. Asphalts, Resins and Bitumen
• Asphalts are high MW, black in color, soluble preferably in aromatic
solvents and carbon disulphide.
• Resins are mostly compounds of highly condensed ring structures,
containing O, S, N sometimes inorganics too.
• Bitumen is manufactured product.
• made of three compounds, asphalts, resins and mineral oil.
• These three component comprise a colloidal system; asphalts are
suspended in oil and resin contribute to stability of the system.

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