How are alkenes isolated from natural sources?

Alkenes are typically isolated from natural sources through the process of steam cracking of hydrocarbons.

Steam cracking is a petrochemical process that involves the breaking down of larger hydrocarbons into smaller ones, such as alkenes. This process is commonly used in the industrial production of ethene, a type of alkene, from natural gas and petroleum.

The process begins with the heating of hydrocarbons to very high temperatures, typically between 700 and 900 degrees Celsius. This causes the hydrocarbon molecules to break apart in a process known as thermal cracking. The resulting mixture of products includes alkenes, along with other types of hydrocarbons.

The alkenes are then separated from the other products through a process called fractional distillation. This involves heating the mixture to different temperatures, causing the various components to evaporate at different rates. The alkenes, which have lower boiling points than many of the other components, evaporate first and can be collected separately.

It's important to note that the specific conditions used in steam cracking, such as the temperature and pressure, can be adjusted to favour the production of certain products. For example, higher temperatures and lower pressures tend to produce a higher proportion of alkenes.

In addition to steam cracking, alkenes can also be produced from natural sources through other methods, such as the dehydration of alcohols. However, these methods are generally less efficient and are not commonly used on an industrial scale.