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Composition of petroleum

Composition of petroleum

Primary coverage
1.General properties, elemental composition and fractions of petroleum
2.Hydrocarbon composition of petroleum fractions
3.Non hydrocarbon compounds in petroleum
4.Trace elements in petroleum
5.Colloid and asphaltene in residue and residuum

General properties of petroleum

1. Physical properties
Petroleum (or crude oil) is usually a black or brown flowing or semi-flowing viscous liquid with a relative density between 0.8 and 0.98. The oil produced in different parts of the world varies in varying degrees in nature.

The solidification point and wax content of crude oils in main oilfields in China are relatively high, and the relative density is mostly between 0.85 and 0.95, which belongs to heavy conventional crude oil.

 Element composition
Basically, it consists of five elements: carbon, hydrogen, sulfur, nitrogen and oxygen. (there are also some trace elements).
In crude oil:
The mass fraction of carbon is generally 83%~87%
The mass fraction of hydrogen is 11%~14%
The mass fraction of sulfur is 0.05%~8%
The mass fraction of nitrogen is 0.02%~2%
The mass fraction of oxygen is 0.05% ~2%

Hydrocarbon content and hydrogen / carbon ratio

The ratio of hydrogen to carbon atoms in crude oil reflects the properties of crude oil. The ratio of hydrogen to carbon atoms in light crude oil or paraffin-based crude oil is higher than that in heavy crude oil or naphthenic crude oil.

The ratio of hydrogen to carbon also contains an important structural information, which is a parameter related to the chemical structure.
Alkanes > naphthenic hydrocarbons > aromatic hydrocarbons

Contents of sulfur, nitrogen and oxygen

Sulfur, nitrogen and oxygen in petroleum do not exist as elements, but as compounds (derivatives of hydrocarbons). It has great influence on the processing technology of petroleum and the performance of petroleum products. Example: catalyst poisoning and environmental pollution.

China's crude oil is low sulfur and high nitrogen. Most of the crude oil has a sulfur content of less than 1% and a nitrogen content of more than 3 per thousand.