The first major step (shown in another video) in refining crude oil is fractional distillation where they heat the crude and literally “boil off” the different hydrocarbon chains. This causes the vertical separation of the different hydrocarbon molecules in the tower.
But because fractional distillation only produces about 20% gasoline from the crude, petroleum engineers get techy by using some sophisticated combinations of physic and chemistry in a process called "cracking”.
Cracking is the process of breaking apart longer hydrocarbon molecular chains into smaller pieces. The process breaks or cracks the heavier, higher boiling-point petroleum fractions into more valuable products such as gasoline and diesel fuel. Though that may sound simple, it’s far from it. In fact, they use several different sophisticated methods of cracking hydrocarbon molecules in a modern refinery.
The first is thermal cracking that they do inside a unit called a “coker” where they subject the hydrocarbons to extreme heat and pressure. Coking is a severe method of thermal cracking used to upgrade heavy residuals into lighter products or distillates. Coking produces straight-run gasoline (naphtha) and various middle-distillate fractions used as catalytic cracking feedstock. The process so completely reduces hydrogen that the residue is a form of carbon called "coke."
Another form of cracking is hydrocracking. A hydrocracking unit, or hydrocracker, takes heavier and higher boiling range molecules and cracks the heavy molecules into distillate and gasoline using hydrogen and a catalyst.
When you’re ready to crack into more layers of refining science, click on the “Learn More” tab below. Also, don’t miss exploring the other videos and lesson activities on our website that complete the rest of the crude oil refining and transportation story.
Plus, take a moment and check out the jazzed petroleum industry careers video on the right and the link to “Careers for Petroleum Engineers” below. Then, click the link of our educational partner here to discover bonus info about refining and transporting crude oil.