Kerosene, also known as paraffin oil or Jet A-1 fuel, is a colorless to pale yellow combustible liquid derived from petroleum. This hydrocarbon-based fuel has played a significant role in modern history since the mid-19th century. Canadian physician Abraham Gesner first produced it from coal in the 1840s, coining the name from the Greek word “keros,” meaning wax. Kerosene rapidly replaced whale oil for lighting, becoming the primary illuminant before the widespread adoption of the electric light bulb.
The Source of Kerosene
Kerosene is not found in a pure state in nature but is almost entirely sourced from crude oil. Crude oil, a complex, naturally occurring mixture of hydrocarbon compounds, serves as the raw material for nearly all major transportation and heating fuels. This black or dark brown liquid is a blend of thousands of different molecules, ranging from light gases to heavy solids.
While crude oil is the dominant commercial source, kerosene can also be derived from other carbon-rich materials. Historically, it was produced from oil shale and coal.
Defining the Chemical Components
Kerosene is chemically defined as a middle distillate, a complex mixture of hydrocarbon molecules. The molecules predominantly contain carbon chains ranging from C9 (nonane) to C16 (hexadecane). This specific range of molecular sizes sets kerosene apart from lighter fuels like gasoline (C4–C12) and heavier fuels like diesel (C10–C19).
The majority of these components are straight-chain saturated hydrocarbons, known as alkanes or paraffins, which account for over 70% of the volume. The mixture also includes smaller amounts of branched alkanes and ring-shaped molecules called naphthenes (or cycloalkanes). Aromatic hydrocarbons are present as well, usually not exceeding 25% of the total volume.
This chemical structure, defined by the C9 to C16 chain length, directly influences the fuel’s characteristics. The intermediate length of these carbon chains is responsible for kerosene’s moderate volatility and good energy density. Since its molecules are heavier than gasoline’s, they require more energy to vaporize, which makes kerosene safer to handle and store.
Refining Kerosene Through Distillation
The industrial process used to separate kerosene from crude oil is called fractional distillation. This process begins by heating the crude oil to a high temperature, typically around 350°C, to vaporize most hydrocarbon compounds. The resulting hot vapor is then fed into the base of a fractionating column.
As the vapor rises through the column, it cools, and different hydrocarbon fractions condense back into liquid at specific temperatures. Heavier molecules, which have higher boiling points, condense lower down, while lighter molecules travel higher before condensing.
Kerosene is collected in the middle section of the column, where the temperature range is suitable for its condensation, typically between 150°C and 300°C. This positions the kerosene fraction between lighter products, such as gasoline, and heavier products, like diesel. The resulting liquid, known as straight-run kerosene, undergoes further treatment to remove impurities like sulfur and meet quality standards for applications such as aviation fuel.
Real-World Properties
The C9 to C16 carbon chain structure gives kerosene physical properties suitable for specific applications. Compared to gasoline, kerosene exhibits low volatility, meaning it does not evaporate easily at room temperature. This low volatility results from its longer carbon chains, increasing its safety profile by making it less prone to accidental ignition.
A defining characteristic is its flash point, the lowest temperature at which the liquid produces enough vapor to ignite, which is typically above 38°C (100°F). This high flash point is required for aviation fuels like Jet A-1. Kerosene also offers a high energy density, delivering substantial power per unit of volume, making it widely used for heating systems and as the primary fuel for jet engines.