Crude Oil Refining and Cracking
Ever wondered how we get petrol from crude oil? It starts with fractional distillation, where crude oil (mainly alkane hydrocarbons) is heated and passed through a column. Different fractions condense at different heights based on their boiling points. Larger hydrocarbons have higher boiling points due to stronger van der Waals forces, so they settle in lower fractions.
When there's too much of the larger hydrocarbons and not enough of the smaller ones, we use cracking to break C-C bonds. This converts large hydrocarbons into smaller, more valuable products. Thermal cracking uses high temperatures and pressure to produce mainly alkenes for polymers, while catalytic cracking uses a zeolite catalyst at lower temperatures (450°C) to produce branched and cyclic hydrocarbons for cleaner-burning motor fuels.
The combustion of alkanes releases heat energy, making them excellent fuels. Complete combustion (with excess oxygen) produces CO₂ and H₂O, while incomplete combustion produces less energy and forms carbon monoxide, soot, and water. This is why proper air flow is crucial when burning fuels.
Did you know? Branched and cyclic hydrocarbons have higher octane numbers, making them better for engines as they burn more cleanly and efficiently.
