01.Crude oil & gas compound

1.Crude oil & gas compound

Hydrocarbons reffers to either oil or gas ,the name of hydrocarbons derived from two words « hydrogen+carbons » ,by this definition we can understand that oil & gas are mainly made with a composition of hydrogen and carbons ,we consider 3/4 of oil & gas compound either hydrogen or carbons.

      I.            Chemistry classification of hydrocarbons :

There is two main types of hydrocarbons that are mentioned as follows

1.     saturated hydrocarbons :

they have a single bond (σ bond) between carbon atoms , the name of this type of hydrocarbon is alkane & its formula is C_nH_2n+2 .

Alkanes are either linear (exemple of n-butane fig.01)

Fig.01 : n-butane(linear)

                          Or branched

                                               

Fig.02 : iso-butane(branched)

      2.      unsaturated hydrocarbons (with π bond):

are the hydrocarbons with more double or triple bonds between carbons

-double bounds : are called alkenes their formula is C_nH_2n

-triple bounds : are called alkynes their formula is C_nH_2n-2

      I.            Paraffins , Naphthenes ,Olefins, Aromatic :

1.     Paraffins (Alkanes) :

-paraffins also called Alkanes which is characterized by linear chains

-if a chain contains more than 18 carbon atoms so the hydrocarbon is called paraffins waxes or mineral waxes.

-if the linear chains have a methyl group linked with the second carbon of the chain then this hydrocarbon is called iso-paraffin

-but if we have more than one Alkyl group linked to this chain so the hydrocarbon is called paraffins branching

-the binding energy between hydrogen & carbon atoms in paraffins is between 80-140 kcal

-the density of paraffins is between 0.6-0.8

-when we deal with high moleculaire weight paraffins then   :                                                                     

      Viscosity for linear chains > viscosity for branched chains

-except tiny paraffins , for each carbon atom added the temperature of boiling is increasing by 20-30 C°

-paraffins are chemically stable

-Paraffins do not react with inorganic acids like  H₂S, HCl,HNO₃

-paraffins are exposed to some biological reaction with yeasts and paraffins are transformed to proteins and fatty acids.

2.     Naphthenes ( cycloalkane) :

-This saturated hydrocarbon is an assembly of methylene group(-CH₂-)    and one or more rings

          Naphthenes = -CH₂-   +  A  Rings ………………………..(1)

a.     First  case is A=1:

-the formula of naphthene would be C_nH_2n

-a ring contains between 3-9 carbon atoms

b.     Second case A>1:

-each ring added will lead to decrease two atoms of hydrogen

-the formula will be C_nH_2n-2x

          x: the number of ring added

                 -Naphthenes has low viscosity

                 -Naphthenes has a high octane index

                 -Naphthenes temperature  combustion is very high

       3.     Olefins:

-Olefins are unsaturated hydrocarbons ,  we find this olefins in crude oil with an average ratio of 3%.

-for each methylene added to the chain so the temperature of combustion will rise by 20-30 C°

-but the temperature decrease if we have a lot of branching

-olefins are charcterized  by a very high octane index

-we use alkylation process to create Iso-octane which have a high octane index .

4.     Aromatic :

-aromatic  contain one ring of benzene or more .

- the formula of aromatic is C_nH_n-2x   where X: the number of added rings of benzene to the original one.

-the key role of aromatic is evaluating the quality of petroleum products

-benzene is the simplest aromatic hydrocarbons

-in high temperatures and in chemical reactions aromatic are known for their stability

- the name aromatic derived from the fact that many of aromatic hydrocarbons have pungent aromas

- toluene = benzene +methyl

      

      I.            None hydrocarbonic compound :

We have three major types of none hydrocarbonic compound

1.     Oxygenic compound :

we have four principles families :

-         Fatty acids CH3(CH2)_nCOOH

-         Naphthenic acids

-         Phenols

-         Alcohol

                Some of those acids are a result of oxidation of oil

2.     Sulfur compound :

We find sulfur compound in a form of H₂S in natural gas for example.

3.     Nitrogen compound:

We have two mainly types:

-         Basic nitrogen

-         None basic nitrogen