Petroleum refinement and products

This is an oil field. Here, drills and pumps are used to extract crude oil from under the ground. Crude oil, also called petroleum, formed millions of years ago, from remains of plants and animals buried in the layers of sediment at the bottom of the ocean. Nowadays, petroleum is used as a source of energy and to make a great range of products. But naturally occurring petroleum is a mixture of different substances, mostly hydrocarbons, in different proportions.

In this form, petroleum is not very useful. It needs to be processed first, so that the different components can be separated from each other and transformed into useful petroleum products. Oil processing happens in large industrial plants known as refineries. Oil refinement starts with separation of the different components that make up petroleum. These components have different physical and chemical properties.

One such property is the temperature at which each component vaporizes. So, crude oil is gradually heated to the specific temperatures at which the individual components turn into gas and separate from the liquid. This separates crude oil into fractions, according to their boiling points. This happens inside a unit called a fractionating column. It’s a cylindrical tower that contains special trays on which vapours can condense.

Heavy fractions, with the highest boiling temperatures, stay at the bottom. Light fractions with low boiling temperatures rise all the way up and condense at the top of the fractionating column. The lightest fractions include gasoline, and liquified petroleum gases. Medium weight fractions include substances such as kerosene, often used as jet fuel, naphtha, used as a solvent, and other distillates such as diesel. The heaviest fractions are fuel oil, lubricating oil, and bitumen that settle at the very bottom.

This process of separating the components of crude oil through vaporizing and condensing is called fractional distillation. Some of the fractions produced through fractional distillation, such as gasoline or diesel, are in higher demand and more valuable than others. So, the next step of oil refinement involves processes that allow us to convert some of the heavier, less useful petroleum products into other products that are of higher value. The most common of these methods uses pressure, heat, and catalysts to break up, or crack, larger heavy hydrocarbon molecules into lighter ones. This method is known as oil cracking.

Apart from light oils, like gasoline, cracking also produces gases, such as methane, ethylene, and propane. Other methods of refining oil involve rearranging or combining molecules through chemical reactions to form new products. For example, some of the gases produced as byproducts of cracking can be recombined to produce gasoline. This process is known as alkylation. Reforming is another conversion method used to change the structure of hydrocarbons, for example, in naphtha.

It results in formation of compounds that make up high-quality gasoline. In the last step, the products of previous processes are treated and purified to increase their quality. Refined and treated petroleum products can be used as fuel, and as raw materials to make plastics, lubricating oils, synthetic rubber, cosmetics, chemicals, and even medicine. Processes in different refineries might vary depending on, for instance, what substances are to be produced in the end. To sum up, oil refinement relies on a series of processes that take advantage of different properties of crude oil components.

Through the steps of separation, conversion, and treatment, crude oil is turned into higher-value petroleum products. Some of the most common methods of oil refinement include fractional distillation, oil cracking, alkylation, and reforming.