The residual solids from the fractional distillation of petroleum are used as?

Analysis

This question tests your knowledge of the fractional distillation of crude oil (petroleum) and the specific uses of the various fractions obtained from the process. You are asked to identify the application of the "residual solids" (often called bitumen or asphalt) left at the bottom of the fractionating column.

Concept: Fractional Distillation of Petroleum

In a fractionating column, crude oil is heated, and components are separated based on their boiling points. The substances with the highest boiling points do not vaporize and remain at the bottom as a thick, viscous residue.

• Refinery Gases: Used for cooking gas (LPG).
• Petrol/Gasoline: Used for cars.
• Kerosene: Used for jet engines and domestic stoves.
• Diesel/Gas Oil: Used for heavy machinery and tractors.
• Lubricating Oils/Waxes: Used for lubrication and candles.
• Bitumen (Residue): This is the thick, black, sticky substance at the bottom. Because of its waterproof and adhesive properties, it is primarily used for road surfacing and as a protective coating for pipes to prevent corrosion.

Step-by-Step Solution

1. Identify the fraction: The "residual solids" mentioned are known as bitumen or asphalt.
2. Evaluate the options: • A (Coatings of pipes): Bitumen is widely used for coating pipes and road surfaces because it is waterproof and durable. This fits the description. • B (Raw materials for cracking): Cracking usually involves heavier gas oils or naphtha, not the final solid residue. • C (Fuel for tractors): This is the role of diesel (gas oil). • D (Fuel for jet engines): This is the role of kerosene (specifically Jet A-1).
3. Conclusion: Based on the properties of the residual fraction, it is used for surfacing and protective coatings.

Exam Tip

When studying the fractional distillation table, remember the order of boiling points: "Gases rise, solids sink." The higher the boiling point, the lower the fraction settles in the column. Bitumen is at the very bottom, so it is the "heaviest" and most viscous.