Crude Oil

CRUDE OIL

Petroleum consists mostly of hydrocarbon molecules. The four main classes of hydrocarbons are paraffins (also called alkanes), olefins (alkenes), cycloparaffins (cycloalkanes), and aromatics. Olefins are absent in crude oil but can be formed in certain refining processes. The simplest hydrocarbon is one carbon atom bonded to four hydrogen atoms (chemical formula CH4), and is called methane.

Petroleum usually contains all of the possible hydrocarbon structures except alkenes, with the number of carbon atoms per molecule going up to a hundred or more. These fractions include compounds that contain sulfur, nitrogen, oxygen, and metal atoms. The proportion of compounds containing these atoms increases with increasing size of the molecule.

he chemical structure of petroleum is composed of hydrocarbon chains of different lengths. These different hydrocarbon chemicals are separated by distillation at an oil refinery to produce gasoline, jet fuel, kerosene, and other hydrocarbons. The general formula for these hydrocarbons is CnH2n+2. For example 2,2,4-Trimethylpentane, widely used in gasoline, has a chemical formula of C8H18 which reacts with oxygen exothermically:[4]

C8H18(aq) + 12.5O2(g) ? 8CO2(g) + 9H2O(g) + heat

Incomplete combustion of petroleum or gasoline results in emission of poisonous gases such as carbon monoxide and/or nitric oxide. For example:

C8H18(aq) + 12.5O2(g) + N2(g) ? 6CO2(g) + 2CO(g) + 2NO(g) + 9H2O(g) + heat

Formation of petroleum occurs in a variety of mostly endothermic