During the refining process that yields mineral oil, primarily different hydrocarbons are separated from each other. Mineral oil itself is a specific fraction composed of a mix of hydrocarbons.
Refining is the process of converting crude oil into useful products. Crude oil is a complex mixture of countless hydrocarbons with varying molecular sizes and structures. The provided reference describes a key step in this process:
After the crude oil is desalted and sent through a furnace where it is heated and partially vaporized, it is sent to a fractionating column. This column operates slightly above atmospheric pressure and separates the hydrocarbons based on their boiling points, which are directly affected by their molecular size.
This fractional distillation process is the primary method used to separate crude oil into different components, or "fractions," based on their boiling point ranges. Mineral oil is one of these fractions.
The Separation Process
In the fractionating column:
- Heated crude oil enters the column.
- Components with lower boiling points rise higher in the column as vapors.
- Components with higher boiling points condense lower in the column.
- Each fraction consists of hydrocarbons that condense within a specific temperature range.
Therefore, the refining process separates the bulk mixture of hydrocarbons in crude oil into various fractions, each containing hydrocarbons with similar boiling points and molecular sizes. The mineral oil fraction is separated from both the lighter hydrocarbons (like those in gasoline and kerosene) and the heavier hydrocarbons (like those in lubricating oils and asphalt).
Essentially, refining doesn't separate from mineral oil in the sense of removing impurities from an already isolated mineral oil product (though further purification steps exist). Instead, it separates the complex mix of hydrocarbons in crude oil into different fractions, one of which is mineral oil. Thus, it separates the hydrocarbons that constitute mineral oil from the other hydrocarbons present in the crude oil feedstock.
Hydrocarbons Separated During Refining
The types of hydrocarbons separated include:
- Lighter Hydrocarbons: These have low boiling points and small molecular sizes.
- Mineral Oil Hydrocarbons: These have moderate boiling points and intermediate molecular sizes.
- Heavier Hydrocarbons: These have high boiling points and large molecular sizes.
Here's a simplified look at how crude oil is separated into common fractions:
| Fraction | Typical Carbon Atoms | Approximate Boiling Range (°C) |
|---|---|---|
| Refinery Gas | C1–C4 | Below 40 |
| Gasoline | C5–C12 | 40–205 |
| Naphtha | C7–C14 | 80–210 |
| Kerosene | C12–C16 | 175–325 |
| Diesel Fuel | C15–C18 | 250–350 |
| Lubricating Oil | C20–C50 | Above 350 (Vacuum Distillation) |
| Mineral Oil | Typically C15–C40+ | Varies (Often overlaps Kerosene to Lube Oil) |
| Fuel Oil | C20–C70 | Above 370 |
| Bitumen/Asphalt | C70+ | Residue |
Note: Mineral oil's exact composition and boiling range can vary depending on the source and specific refining process, often falling within or overlapping the ranges for Kerosene, Diesel, and Lubricating Oil.
In summary, the fundamental separation achieved during the initial refining of crude oil to obtain fractions like mineral oil is the separation of different groups of hydrocarbons based on their boiling characteristics, which are tied to their molecular size.
