The overhead product is composed of which type of hydrocarbons?

• A. Lighter hydrocarbons
• B. Heavier hydrocarbons
• C. Non hydrocarbon gases
• D. A mixture of water and light ends

Answer: (A)

When you distill a hydrocarbon mixture, the column separates components by boiling point. The overhead stream is the vapor that reaches the top and is condensed, so it reflects the lightest fractions that boil at the lowest temperatures. Because these low-boiling compounds rise to the top while heavier ones stay toward the bottom, the overhead product ends up being lighter hydrocarbons. This is why methane, ethane, propane, and butanes (as part of the light-cut) are typical constituents of the overhead, depending on how far the column is operated. Non-hydrocarbon gases or water aren’t the main components of overhead; they’re either removed separately or stay out of the hydrocarbon light-end stream.