Petrochemicals are the chemical byproducts of the refining of petroleum. Some of the chemical compounds produced by petroleum can also be created from renewable sources like maize, palm fruit, or sugar cane as well as alternative fossil fuels like coal or natural gas.

Olefins, which include ethylene and propylene, and aromatics are the two most prevalent types of petrochemicals, including benzene, toluene and xylene isomers.

Olefins and aromatics are made in oil refineries through the fluid catalytic cracking of petroleum fractions. Olefins are made at chemical facilities by steam splitting liquid natural gas, such as ethane and propane. By catalytically reforming naphtha, aromatic compounds are created. Olefins and aromatics are the building blocks for a variety of substances, including cleaners, adhesives, and solvents. Olefins serve as the building blocks for the polymers and oligomers used to make gels, lubricants, elastomers, resins, fibers, and plastics.

According to their chemical makeup, primary petrochemicals are split into three groups:

Ethene, propene, butenes, and butadiene are examples of olefins. Important suppliers of industrial chemicals and plastics goods are ethylene and propylene. Synthetic rubber is made with butadiene.

Aromatics, also known as BTX or benzene, toluene, and xylenes, are predominantly acquired from petroleum refineries through extraction from the reformate created in catalytic reformers utilizing naphtha that is also obtained from petroleum refineries. Alkanes can also be aromatized to create BTX as an alternative. The isocyanates MDI and TDI needed to create polyurethanes are made from benzene and toluene, both of which are utilized as basic materials for colors and synthetic detergents.

A mixture of hydrogen and carbon monoxide called "synthesis gas" is used to make compounds like methanol. Steam reforming facilities, which are used to generate hydrogen for the manufacturing of ammonia, should not be confused with steam crackers. Methanol is employed as a solvent and a chemical intermediary in the production of the fertilizer urea, which is made from ammonia.