Refining Glossary


The American standard unit of measurement for oil. One barrel is 35 imperial gallons or 159 litres.


an extremely heavy semi-solid product of oil refining made up of heavy hydrocarbons. It is used for road-building and roofing.


a substance which alters the rate of a chemical reaction without being used up itself in the reaction.


the process of breaking down larger molecules of hydrocarbons into smaller ones. When this is done by heating the oil it is known as ‘thermal cracking’. If a catalyst is used it is known as ‘catalytic cracking’.

Crude oil

oil which has not undergone any refining. Crude oil is a mixture of hydrocarbons with small quantities of other chemicals such as sulphur, nitrogen and oxygen.

Cubic metre

one cubic metre is equal to 1000 litres.


Any process or process step that results in removal of sulfur from organic molecules.


a light oil fuel used in diesel engines.


The products obtained by condensation during the fractional distillation process.


Fluid catalytic cracking. A process for converting high boiling gas oils to lighter liquids, primarily gasoline range naphtha and diesel range gas oils. The most widely practiced refinery conversion process.


A raw material for the manufacturing process.

Fossil fuel

– the organic remains of plants, animals and bacteria which decayed and over millions of years formed crude oil, natural gas and coal.

Fractional distillation

– a separation process which uses the difference in boiling points of liquids.

Fuel oil

– a heavy distillate oil used for power stations, industry and ships boilers.

Gas oil

– a medium distillate oil, used to produce diesel fuel and to burn in central heating systems.


– the term used in the oil industry to refer to petrol.


Heavy Vacuum Gas Oil - An intermediate product produced in the Vacuum distillation unit, and further processed to produce GasOil or Gasoline


A compound containing hydrogen and carbon only. Hydrocarbons may exist as solids, liquids or gases (coal, crude oil and natural gas).


A medium-light oil used for lighting, heating and aircraft fuel.


Light Vacuum Gas Oil - The lightest fraction from the Vacuum Column, is blended into the gas oil mix


Liquefied Petroleum Gas - Generally, any light hydrocarbon fuel that must be compressed to keep it from boiling away. (LPG) Commercial LPG usually contains mixtures of propane (C3H8) and butane (C4H10).


The main component of natural gas. It also occurs in coal beds and is produced by animals and by the decay of vegetable matter. This is the smallest hydrocarbon molecule, with only one carbon atom and four hydrogen atoms.

Metric tonne

One metric tonne is equal to 1000 kilogrammes.


Methyl-t-butyl ether - an oxygen containing fuel component used in reformulated gasoline. Commonly made from methanol (methyl alcohol) and isobutene.


– very light fractions of oil, used to produce petrol and as raw material for the petrochemical industry (e.g. to make plastics).

Natural gas

– naturally occurring gases found either alone or together with oil in underground reservoirs. The main component is methane.

Octane rating

– a measure of the performance of gasoline. A high octane rating gives efficient ignition.


– chemicals made from crude oil.


– the light fuel used in cars and motor bikes also known as Gasoline.


– a plant where the components of crude oil are separated and converted into useful products.


, Short for Residuum - General term for any refinery fraction that is left behind in a distillation. Atmospheric resid, sometimes called long resid or atmospheric tower bottoms (ATB), is the undistilled fraction in an atmospheric pressure distillation of crude oil. Likewise, vacuum resid, short resid, or vacuum tower bottoms (VTB), is the undistilled fraction in a vacuum distillation.

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