Crude oil refers to “unprocessed” oil, the raw material extracted directly from the ground, which is also known as petroleum .Crude oil is a fossil fuel that was naturally formed by the decay of ancient Marine plants and animals that lived millions of years ago-any spot where crude oil was found was once the seabed .Crude oil has different colors (from clear to black) and viscosity (from watery to almost frozen).

Crude oil, on average, consists of several elements or compounds like below：

Carbon – 84%

• hydrogen – 14%
• sulfur – 1 to 3% (hydrogen sulfide, sulfur, disulfide and elemental sulfur)
• nitrogen – less than 1% (alkaline compounds with amino)
• oxygen – less than 1% (found in carbon dioxide, phenol, ketones and carboxylic acids and other organic compounds)
• metal – less than 1% (nickel, iron, vanadium, copper and arsenic)
• salts — less than 1% (sodium chloride, magnesium chloride, calcium chloride)Crude oil is a very useful raw material for the production of many different substances.Because crude oil contains hydrocarbons, which are molecules of hydrogen and carbon with different lengths and structures, ranging from straight and branched chains to ring chains.There are two factors that make chemists particularly interested in

  hydrocarbons：

  Hydrocarbons contain a lot of energy.Many products from crude oil, such as gasoline, diesel and paraffin, use this energy .Hydrocarbons come in many forms.The simplest hydrocarbon is methane (CH4), a gas lighter than air .Long chains of five or more carbon atoms are liquid.Very long chains are solids, such as wax or tar.By chemically coupling the hydrocarbon chains, a variety of products can be made, from synthetic rubber to nylon to tupperware.Hydrocarbon chains are almost omnipotent!

  The main types of hydrocarbon in crude oil include:

  paraffin

  • chemical general formula: CnH2n + 2 (n as an integer from 1 to 20)

  Straight or side chain molecules

  • at room temperature, according to the different molecules, there are two kinds of gaseous and liquid form
  • example: methane, ethane, propane, butane, isobutane, pentane, hexane
  • aromatic hydrocarbon
  • chemical general formula: C6H5 – Y (Y is connected on the benzene ring of a long straight chain molecules)

  It has one or more ring structures

  • ring of six carbon atoms, bonding way as the single bond between carbon atoms alternates with double bond

  Generalize to liquid

  • example: benzene, naphthalene
  • naphthenic Napthenes or naphthenic Cycloalkanes
  • chemical general formula CnH2n (n as an integer from 1 to 20)

  It has one or more ring structures

  The key positions between the carbon atoms in the ring are all single bonds

  The room temperature is generalized as a liquid state

  • example: cyclohexane, methyl cyclopentane

  Other hydrocarbons

  • olefins
  • chemical general formula CnH2n (n as an integer from 1 to 20)

  A straight or supported chain molecule with a carbon double key

  The presence of liquid or gas form

  • example: ethylene, butene, isobutene

  alkyne

  • chemical general formula CnH2n – 2 (n as an integer from 1 to 20)

  A straight or supported chain molecule with two carbon double buttons

  The presence of liquid or gas form

  • example: acetylene, butadiene