Petroleum Chemistry is made of a mixture of different hydrocarbons. The most prolific hydrocarbons found in the chemistry of petroleum are alkanes, these are also sometimes knows as branched or linear hydrocarbons.
A significant percentage of the remaining chemical compound is the made up of aromatic hydrocarbons and cycloalkanes. Additionally petroleum chemistry contains several more complex hydrocarbons such as asphaltenes.
Each geographical location and hence oil field will produce a raw petroleum with a different combination of molecules depending upon the overall percentage of each hydrocarbon it contains, this directly affects the colouration and viscosity of the petroleum chemistry.
The primary form of hydrocarbons in the chemistry of petroleum are the alkanes, which are also often named paraffins. These are termed saturated hydrocarbons and the exhibit either branched or straight molecule chains.
The paraffins are very pure hydrocarbons and contain only hydrogen and carbon; it is the alkanes which give petroleum chemistry its combustible nature. Depending upon the type of alkanes present in the raw petroleum chemistry it will be suitable for different applications.
For fuel purposes only the alkanes from the following groups will be used: Pentane and Octane will be refined into gasoline, hexadecane and nonane will be refined into kerosene or diesel or used as a component in the production of jet fuel, hexadecane will be refined into fuel oil or heating oil.
When it comes to the chemistry of petroleum which does not contain a significant quantity of the kinds of paraffins required to produce a combustible fuel then things become simpler, as many non-fuel applications of petroleum are far more lenient in the chemical compound of the raw petroleum.
The exception to this are the petroleum molecules which have less than five carbon atoms, these are a form of natural petroleum gas and will either be burned away or harvested and sold under pressure as LPG (Liquid Petroleum Gas).
The cycloalkanes, which are also often referred too as the napthenes are classed as a saturated form of hydrocarbon. By saturated we mean the molecule contains either one or several carbon rings with atoms of hydrogen attached to them. These hydrocarbons display almost identical properties to paraffins but have a much higher point of combustion.
Lastly, the aromatic hydrocarbons are another form of unsaturated hydrocarbon. The specific difference between the other hydrocarbons in the petroleum molecule is that the aromatic hydrocarbons will contain benzene rings, with atoms of hydrogen attached to them. Aromatic hydrocarbons tend to produce far more emissions when combusted, many will have a sweet, sickly smell to them, hence the name aromatic hydrocarbons.
The quantity and percentages of the specific types of hydrocarbons in raw petroleum chemistry can be determined by testing in a laboratory. The process involves extracting the, molecules using some form of solvent and then separating them using a gas chromatograph. Finally an instrument such as a mass spectrometer will be used to examine the separate molecules in the chemical compound of the sample.