Final answer:
Fractionating columns in CHEM 235 work by heating crude oil to vaporize its components, which then ascend through the column and condense at different levels based on their boiling points, allowing for separation into various petroleum fractions. Additional processes like cracking and reforming further refine the products.
Step-by-step explanation:
Fractionating columns used in CHEM 235, or any standard chemical laboratory or industrial process, like those in oil refineries, work on the principle of fractional distillation. These columns separate mixtures based on the differing boiling points of components. In the case of crude oil, it is heated to about 425 °C, vaporizing many of its components. As these vapors ascend through the fractionating column, they pass through trays or bubble caps which help to increase the efficiency of the separation process.
Different components condense at various levels within the column as they reach their respective dew points—petroleum fractions with higher boiling points condense at lower levels, and those with lower boiling points condense higher up in the column. These fractions are then drawn off and further processed to create products like diesel fuel, kerosene, and gasoline.
The process of cracking involves breaking down heavier hydrocarbons into lighter molecules, which can then be reformed into valuable products with carefully controlled compositions. Another method, called reforming, chemically converts straight-chain alkanes to branched alkanes or aromatic hydrocarbons using metal catalysts. These processes, alongside fractional distillation, fine-tune the product mix to meet specific market demands.