Petrochemicals (also known as petroleum derivatives) are chemicals derived from petroleum. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable sources such as corn, palm fruit, or sugar cane.

The two most common petrochemical classes are olefins (including ethylene and propylene) and aromatics (including isomers of benzene, toluene, and xylene).

Petroleum refineries produce olefins and aromatics by fluid catalytic cracking of petroleum fractions. Chemical plants produce olefins by steam cracking "natural gas condensates" such as ethane and propane. Aromatics are produced by catalytic reforming of naphtha. Olefins and aromatics are the basic components of a wide range of materials such as solvents, detergents and adhesives. Olefins are the basis of polymers and oligomers used in plastics, resins, synthetic fibers, elastomers, lubricants and gels.[1]​[2]​.

Global production of ethylene and propylene is approximately 115 million tons and 70 million tons per year, respectively. The production of aromatics is approximately 70 million tons. The largest petrochemical industries are located in the United States and Western Europe; However, the greatest growth in new production capacity is in the Middle East and Asia. There is important interregional petrochemical trade.

Primary petrochemicals are divided into five groups based on their chemical structure:

In 2007, the quantities of ethylene and propylene produced in steam crackers were approximately 115 Mt (megatonnes) and 70 Mt, respectively.[3]​ The ethylene production capacity of large steam crackers ranged between 1.0 and 1.5 Mt per year.[4]​.

The adjacent diagram schematically shows the main sources of hydrocarbons used in the production of petrochemical products.[1]​[2]​[5]​[6]​.

Like basic chemicals, petrochemicals are manufactured on a large scale. Petrochemical manufacturing units differ from commodity chemical plants in that they often produce a number of related products. Compare this to specialty chemicals and fine chemicals where products are manufactured in discrete batch processes.

Petrochemical products are mainly manufactured in a few manufacturing locations around the world, for example in the industrial cities of Jubail and Yanbu in Saudi Arabia, Texas and Louisiana in the USA, in Teesside in the northeast of England in the United Kingdom, in Rotterdam in the Netherlands. and in Jamnagar") & Dahej") in Gujarat, India. Not all petrochemical or commodity chemical materials produced by the chemical industry are manufactured in a single location, but groups of related materials are often manufactured in adjacent manufacturing plants to induce industrial symbiosis, as well as material and utility efficiencies and other economies of scale. This is known in chemical engineering terminology as integrated manufacturing. Specialty and fine chemicals companies are sometimes located in similar manufacturing locations as petrochemicals, but in most cases do not need the same level of large-scale infrastructure (e.g. pipelines, storage, ports and energy, etc.) and can therefore be found in multi-sector business parks.