Benzene, also commonly called benzol, is an organic chemical compound classified as an aromatic hydrocarbon. A highly flammable, clear to yellow-tinted liquid with a characteristically sweet aroma, benzene is still widely in use today despite clear evidence as to its cytotoxicity. While small quantities of benzene form naturally during events such as forest fires or volcanic eruptions, the vast majority of the world’s benzene is manufactured.
First distilled from resin harvested from Styrax trees in southeast Asia in the early 19th century, benzene originally drew its name from that resin, known commercially as gum benzoin at the time. But by mid-century, chemists successfully produced benzene via coal tar and began large-scale production of it for use in industrial settings. Later, production technology evolved to include manufacturing benzene from crude oil, as well. Today, a small percentage of benzene is still manufactured via coal distillation, but most commercially produced benzene is a byproduct of petroleum production. Most of the world’s benzene is made in the Middle East and Africa, although the United States does maintain some small-scale benzene production. China is the world’s largest consumer of benzene. The United States currently ranks second in benzene consumption.
In 1825, English scientist, Michael Faraday, successfully separated out a quantity of benzene from a sample of illuminating gas, an early coal product used to light street lamps in the 19th century. Twenty years later, Charles Mansfield and August Wilhelm von Hofmann perfected the earliest processes for extracting benzene from coal tar and begun large-scale production.
Today’s benzene is primarily produced via two main methods: steam cracking or catalytic reformation. Both processes use fractions from crude petroleum (and to a lesser extent, natural gas) refinement called naphtha, which consists of a mix of aliphatic hydrocarbons that contain anywhere from five to ten carbon atoms per molecule.
Steam cracking begins by vaporizing the raw material and mixing that vapor with steam. This gaseous mixture is then forced through a superheated furnace in order to produce a raw pyrolysis gas. The gas gets mixed with assorted alcohol-based solvents which extract the individual aromatic compounds, to include benzene. These assorted dissolved compounds are then fractionally distilled to separate them out into individual products.
Catalytic reformation takes the same raw material, removes any and all sulfurous impurities, and mixes the naphtha with superheated hydrogen instead of steam. This gaseous mixture is pushed over a platinum catalyst under pressure. The resulting chemical reaction between the gas and platinum releases the separate hydrocarbons from the naphtha. These hydrocarbons are then dissolved and distilled in order to finish the production of each individual product, including benzene, among other aromatic hydrocarbons.
This manufactured benzene is an important intermediate ingredient in the production of many other industrial chemicals, solvents, resins, polymers, plastics, nylon fibers and pesticides. It is also found in gasoline in small percentages. Because benzene has a high octane rating, meaning it can sustain a high rate of compression before igniting, it is a beneficial additive to petroleum fuels.
However, benzene is also an extremely dangerous
In addition to being highly flammable, benzene is incredibly toxic and absolutely carcinogenic. Acute benzene poisoning via inhalation or ingestion carries an immediate risk of death if the exposed individual cannot be removed from the contaminated area and receive emergency medical attention. Long-term exposure to benzene is definitely linked with a significantly higher risk of developing several blood cancers.