A petrochemical is a chemical which has been derived from petroleum or natural gas. These chemicals are typically extracted during the refining process as crude oil and gas are distilled or cracked, and they can be utilized in a wide variety of ways. The explosion of the industry in the 20th century led to a proliferation of products which involved petrochemical components, and demand for these chemicals is constantly on the rise as people develop new products and new uses for such products. Refineries which process such chemicals can be found all over the world.
Some of the primary petrochemicals obtained in the refining process include toluene, benzene, ethylene, and propylene. These primary chemicals can be further refined into intermediate or derivative products which can be used in the manufacture of end-use goods. Most of the petrochemicals are hydrocarbons, reflecting the high concentration of hydrogen and carbon in crude oil, and they are distinctive, though chemically similar, from fuels refined from crude oil.
A huge variety of products are made with petrochemicals, including plastics, soaps, pharmaceuticals, fertilizers, pesticides, detergents, flooring, solvents, and epoxies. Synthetic fibers, rubber, and other materials are also manufactured from petrochemicals. Most people interact with numerous such products every day, from the synthetic fibers used in a fleece jacket on a cool day to the plastics used in the construction of a steering wheel.
Refineries can adjust their production of a primary petrochemical to meet demand in a variety of ways. As crude oil is refined, it can be treated with fractional distillation, in which it is heated to separate out the various components for use, or it can be “cracked” with a catalyst which breaks up hydrocarbon chains to create desired products. Because petrochemicals are commonly in high demand, refineries must be able to act quickly to take advantage of favorable pricing and demand.
The refining and production of end-stage petrochemical products has been criticized on the basis of environmental concerns. Extraction and transport of crude oil can have a very negative environmental impact, and the refining process can be highly polluting and sometimes dangerous for neighboring communities. Petrochemicals are also very slow to break down in the natural environment, raising issues about the proper use and disposal of consumer products. These products are also not renewable, because they come from resources built up over the course of millions of years, which means that once the world's deposits of crude oil and natural gas are exhausted, a serious problem could emerge for the petrochemical industry.