Hydrocarbon Cracking & Why It Is Done | Organic Chemistry | Chemistry | FuseSchool

Crude oil contains hydrocarbons of varying chain lengths. Smaller hydrocarbons, with lower boiling points and higher volatility, are more useful as fuels like those used in cars and airplanes. This creates a high demand for short-chain hydrocarbons. However, fractional distillation yields a large supply of long-chain molecules.

Cracking breaks down long-chain alkanes into smaller alkanes and an alkene molecule. This process helps meet the demand for short-chain hydrocarbons. The resulting alkenes are also valuable, used in plastic manufacturing. The breakdown is somewhat random; for example, C12H26 can crack into various combinations, but the total number of carbon and hydrogen atoms remains constant.

There are two primary methods of cracking: thermal cracking and catalytic cracking. Thermal cracking uses high temperatures (up to 750°C) and high pressures (70 atmospheres) to break carbon-carbon bonds. Catalytic cracking, which is preferred in industry, uses lower temperatures (around 500°C) and pressures, employing a zeolite catalyst. This method specifically produces molecules with 5 to 10 carbon atoms, making them highly useful for petrol.

Cracking is the process of converting large alkanes into smaller alkanes and alkenes. Thermal cracking uses high heat and pressure, while catalytic cracking, favored in industry, utilizes a catalyst at lower temperatures and pressures to produce more molecules suitable for petrol.