Refining Crude Oil Process, from Separation to Treatment

Refining crude oil is one of the processes that must not be missed when producing petroleum products. The step begins with crude oil extraction until finally, the oil becomes consumer or industry products.

This article discusses the process of refining crude oil from start to finish. Let’s pay attention to this article until the end.

A Glimpse of Crude Oil

Before we jump into how refining crude oil works, let’s get to know more about crude oil. Crude oil is a liquid hydrocarbon naturally formed in the Earth from fossils over millions of years.

Petroleum is one of the most in-demand natural resources because it is often used to make petrochemical products and other industries, such as rubber, plastics, medicine, fuel, and so on.

Data on Statista revealed that in 2024, the global demand for crude oil reached 103.75 million barrels per day, and in 2025, the demand is predicted to increase up to 105 million barrels per day.

How Refining Crude Oil Works

Generally, crude oil is refined in basic processes, which are separation, conversion, and treatment. Yet, before the oil is processed, you must extract it from the ground.

Some commonly applied crude oil exploration and extraction methods are well drilling, natural pressure, injection methods, and lift pumps. Then, it will be processed as follows:

1. Separation

Separation is carried out with fractional distillation. This distillation is done in a distillation tower using a furnace. The oil that has entered the oil refinery will be heated. Then, the liquid and vapor will separate into petroleum components called fractions. These components are distinguished by their boiling points.

In addition, the heavy and compact fractions will remain at the bottom of the tower, while the lighter ones will evaporate up to the top.

2. Conversion

The distilled petroleum will be further processed into more valuable products. The formed fractions will be converted into intermediate components that eventually become the final product.

The most common conversion is cracking. Cracking uses catalysts, heat, pressure, and usually hydrogen to break the heavy hydrocarbon into lighter ones. Moreover, cracking transforms petroleum into other products and rearranges the hydrocarbons to get better quality and value.

One of these processes is known as alkylation. An example of an alkylation process is combining cracking byproducts to make gasoline.

3. Treatment

After going through the transformation process, the product will go to the final treatment. One of the examples is improving the octane rating of gasoline by uniting the intermediate component in the processing units.

Next, the products that have gone through final treatment are stored in tanks near the oil refinery. It will be distributed using specialized trains, transport trucks, or pipelines around the world.

The Methods of Refining Crude Oil

The explanation below will explain the methods of refining crude oil. In general, the methods below happen in the conversion and treatment process. Here is the complete information:

1. Reforming

Reforming is a process of improving the product quality using a catalyst, pressure, and heat. Typically, reforming is done to increase the gasoline’s octane rating and the quality of petrochemical feedstock.

The processed petroleum, or naphtha, contains hydrocarbon mixtures high in paraffin and naphthene. The reforming process will turn the compound into aromatic and isoparaffin for mixing high-octane gasoline.

2. Cracking

Cracking is a process of breaking the heavier hydrocarbons, which are high-boiling-point oils, into lighter products, like diesel and gasoline. There are several types of cracking, such as:

Catalytic cracking: The process of converting heavy hydrocarbon fractions into a mixture of more valuable products with heat, catalysts, and pressure. This process is done chemically. The products are gasoline, LPG, unsaturated olefin compounds, etc.
Fluid catalytic cracking: A process that uses a catalyst in the form of a fine powder that flows like a liquid when mixed with air, water vapor, or steam.
Thermal cracking: A process that uses heat to break down distillation residue. The light elements from this process are utilized as gasoline and fuel. Then, the heavy residue is used to make coke for carbide and graphite manufacturing.
Hydrocracking: A process that increases the gasoline component and is used to produce light distillates. This process produces no residue.

3. Alkylation

Alkylation is a process of bonding an olefin with isobutane to make bigger branched-chain molecules, or isoparaffin. Isoparaffin is used to increase the octane rating.

In the process, isobutane and olefin will be mixed with acid catalysts and cooled. Next, alkylate, propane, butane, and isobutane are formed. Isobutane will be recycled to be feedstocks, while propane and butane are used to make LPG.

4. Polymerization

Polymerization is a process where light unsaturated hydrocarbon molecules react and fuse to create larger molecules. This process uses pressure, an acid catalyst, and a specific temperature.

It can be used to produce polymer gasoline (high-octane olefinic gasoline blend components) through butene and isobutane or isoparaffin reaction.

5. Isomerization

Isomerization is a process of rearranging straight-chained hydrocarbons, or paraffin, to make them have branches attached to the main chain (isoparaffin). This process releases additional isobutane feedstocks for alkylation and increases gasoline quality.

Isomerization mixes butane with a little chloride and hydrogen to make it react with the help of a catalyst and form isobutane, butane, and lighter gases. The lighter gas will be used as fuel for oil refineries, and the butane will be recycled into feedstock.

6. Hydrotreating

After becoming a petroleum refined product, several treatments will be carried out to remove contaminants, impurities, and sulfur content in the product. One of the ways is hydrotreating.

In this process, the material will be mixed with hydrogen and heated at 300–380 degrees Celsius. Then, the oil will get into a catalyst-filled reactor to make it react

The reactions include nitrogen turning into ammonia; hydrogen combining with sulfur to produce hydrogen sulfide; and the conversion of olefins, naphthene, and aromatics into paraffin, methane, ethane, butane, and propane. Furthermore, the iron content of the oil is also removed in this process.

That concludes the process of refining crude oil, from exploration to becoming industrial products. Crude oil is frequently used to produce many industrial and consumer products, like plastic and rubber.

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