ENG 101 Lecture 1: ISU CHEM
Intro
Crude oil is a naturally occurring, unrefined petroleum product composed of hydrocarbon deposits and
other organic materials. Crude oil can be refined to produce usable products such as gasoline, diesel and
various forms of petrochemicals.
Structure
Crude oil is a mixture of liquid hydrocarbons (compounds composed mainly of hydrogen and carbon),
though it also contains some nitrogen, sulfur, and oxygen. Those elements form a large variety of
complex molecular structures, some of which cannot be readily identified. Regardless of variations,
however, almost all crude oil ranges from 82 to 87 percent carbon by weight and 12 to 15 percent
hydrogen by weight.
Properties
The American Petroleum Institute gravity, or API gravity, is a measure of how heavy or light a
petroleum liquid is compared to water: if its API gravity is greater than 10, it is lighter and floats on
water; if less than 10, it is heavier and sinks. crude oils can be classified as heavy, medium, and light.
Heavy: 10–20° API gravity, Medium: 20–25° API gravity, Light: above 25° API gravity.
Crude oil also is categorized as “sweet” or “sour” depending on the level of sulfur, which occurs either as
elemental sulfur or in compounds such as hydrogen sulfide. Sweet crudes have sulfur contents of 0.5
percent or less by weight, and sour crudes have sulfur contents of 1 percent or more by weight.
Generally, the heavier the crude oil, the greater its sulfur content. Excess sulfur is removed from crude
oil during refining, because sulfur oxides released into the atmosphere during combustion of oil are a
major pollutant.
Paraffins: These can make up 15 to 60% of crude. • Paraffins are the desired content in crude and what
are used to make fuels. • The shorter the paraffins are, the lighter the crude is.
Extremely flammable and toxic to the environment. This is the light transmitted through crude oils. It is
yellowish to red for light oils and dark or even opaque for heavy (or low A.P.I gravity) oils, crude oils can
smell different depending on their composition. Sweet crude oils have a more gasoline-like smell,
whereas sour crude oils contaminated with high levels of sulfur smell of rotting eggs. All crude oil
contains VOCs ,Volatile organic compounds (VOCs) are compounds that easily become vapors or gases.
Chemical process
Dispersants are chemicals that are sprayed on a surface oil slick to break down the oil into smaller
droplets that more readily mix with the water. Dispersants do not reduce the amount of oil entering the
environment, but push the effects of the spill underwater. Chemical dispersants can be used to break
down the oil and speed up its natural biodegradation. Dispersants break the slick into droplets of oil,
which makes it easier for the oil and water to mix.
Document Summary
Crude oil is a naturally occurring, unrefined petroleum product composed of hydrocarbon deposits and other organic materials. Crude oil can be refined to produce usable products such as gasoline, diesel and various forms of petrochemicals. Crude oil is a mixture of liquid hydrocarbons (compounds composed mainly of hydrogen and carbon), though it also contains some nitrogen, sulfur, and oxygen. Those elements form a large variety of complex molecular structures, some of which cannot be readily identified. Regardless of variations, however, almost all crude oil ranges from 82 to 87 percent carbon by weight and 12 to 15 percent hydrogen by weight. Heavy: 10 20 api gravity, medium: 20 25 api gravity, light: above 25 api gravity. Crude oil also is categorized as sweet or sour depending on the level of sulfur, which occurs either as elemental sulfur or in compounds such as hydrogen sulfide.
