Which chemical process involves the use of heat to convert heavy fractions into lighter products?

The correct choice is related to a process that employs heat to transform heavier hydrocarbon fractions into lighter, more valuable products. In the context of refining, delayed coking is a thermal cracking method that processes heavy residues, typically from the bottom of a distillation column, into lighter hydrocarbons and petroleum coke. The process takes place in a coker unit, where heavy feedstock is heated, causing the larger hydrocarbon molecules to break down into smaller fractions.

This method is particularly advantageous for managing and upgrading heavy crude oil and bitumen, which would otherwise be difficult to refine. As the feedstock is heated, it undergoes thermal decomposition, leading to the production of lighter distillates such as naphtha and diesel, which can then be further processed or utilized as fuels or chemical feedstocks.

In comparison to the other options, while catalytic cracking and hydrocracking also aim to convert heavier fractions into lighter products using heat and sometimes catalysts or hydrogen, delayed coking is distinct in its reliance solely on heat without the necessity for catalysts. Fractional distillation, on the other hand, is a separation process that does not chemically alter the components; it simply separates them based on boiling points.