Crude Oil

• Crude oil/ petroleum- a mixture of hydrocarbons

  • some are small molecules, few atoms joined together
  • some are complex, many atoms forming long chain molecules
• Crude oil as a mixture is not a very useful substance

  • the fractions are useful
• Petroleum is a fuel that can be separated using fractional distillation similar to other fossil fuels
• Fractions - the different hydrocarbons that make up the mixture, enormously valuable, each fraction having many different applications

  • each fraction consists of groups of hydrocarbons of similar chain lengths
  • molecules in each fraction have similar properties and boiling points, depending on the number of carbon atoms in the chain
  • size and length of each hydrocarbon molecule determines in which fraction it will be separated into
  • size of each molecule is directly related to how many carbon and hydrogen atoms the molecule contains
• Most fractions contain mainly alkanes
• Alkanes - compounds of carbon and hydrogen with only single bonds between them
• Fractions in petroleum are separated from each other in a process called fractional distillation
• Fractional Distillation

  • carried out in a fractionating column which is very hot at the bottom and cool at the top
  • crude oil enters the fractionating column and is heated so vapours rise
  • vapours of hydrocarbons with very high boiling points will immediately condense into liquid at the higher temperatures lower down
  • Vapours of hydrocarbons with low boiling points will rise up the column and condense at the top
• The different fractions condense at different heights according to their boiling points and are tapped off as liquids

  • The fractions containing smaller hydrocarbons are collected at the top of the fractionating column as gases
  • The fractions containing bigger hydrocarbons are collected at the lower sections of the fractionating column
• Fractional Distillation Column - as you move up a fractionating column the temperature decreases, so the compounds with higher boiling points come off lower down the column
• Fractional Distillation Column

  A) cold

  B) hot

  C) heated crude oil

  D) gasoline

  E) Refinery gases

  F) bottled gas

  G) fuel for cars

  H) Naptha

  I) aircraft fuel

  J) diesel

  K) fuel for cars, lorries, buses

  L) fuel oil

  M) fuel for ships, power stations

  N) bitumen

  O) for roads and roofs

  
• Properties of fractions in crude oil

  • Viscosity: If the carbon chain is longer, the attraction between the hydrocarbon molecules increases, the liquid is more viscous
  • Colour: As carbon chain length increases the colour of the liquid gets darker as it gets thicker and more viscous
  • Melting point/boiling point: The longer carbon chain means more heat is needed to separate the strong intermolecular forces between the large molecules, increasing in boiling point
  • Volatility: The longer the carbon chain, the bigger the molecules are in size, attraction is stronger, the less volatile
• Uses for each fraction

  A) refinery gas

  B) bottled camping gas, heating, cooking

  C) fuel for cars

  D) naptha

  E) jet fuel (paraffin), oil stores

  F) diesel engines, lorries, trains

  G) ships, power stations, house heating systems

  H) surfacing roads and roofs

  
• LPG and CNG are gas fuels

  • LPG - liquified petroleum gas
  • CNG - compressed natural gas
• Order of each fraction mnemonic - rhinos play nicely, parrots dance funnily like birds
• Lubrication oil fraction - lubricants, waxes and polishes
• When changing the state of a simple molecular substance, the intermolecular forces are broken not the covalent bonds as the compound isn’t chemically changing as the chemical formula still remains the same when the substance changes state
• longer carbon chains have higher boiling points as they have more intermolecular forces, requiring more energy to break them, increasing boiling point
• Define crude oil/petroleum

  A mixture of hydrocarbons aka alkanes
• What type of fuel is petroleum? What is similar between petroleum and these fuels?

  Petroleum is a fossil fuel and these fuels, similar to petroleum, can be separated by fractional distillation
• What is LPG & CNG? Define each

  LPG and CNG are gas fuels

  LPG - liquid petroleum gas

  CNG - compressed natural gas
• Write down the order of hydrocarbon substances in fractional distillation from top to bottom in the tank

  Refinery Gas

  Petrol/gasoline

  Naptha

  Paraffin/Kerosene

  Diesel fuel

  Fuel Oil

  Lubrication Fraction

  Bitumen
• What are the uses of each hydrocarbon in crude oil?

  Refinery gas - bottled camping gas for heating and cooking

  Petrol and gasoline - fuel for cars

  Naphtha - making chemicals

  Paraffin/Kerosene - for jet fuel and oil stores

  Diesel fuel - for diesel engines like trucks, lorries, trains

  Fuel oil - for ships & home heating systems

  Lubrication fraction - waxes, polishes and lubricants

  Bitumen - for roofing and road surfaces
• What is the mnemonic for hydrocarbons in crude oil

  Rhinos play nicely, parrots dance funnily like birds
• What is Naphtha?

  flammable liquid hydrocarbon mixture
• Define fraction


  A fraction is the chemical that collects during the process of fractional distillation. The distillation process forms distillates at various temperature ranges.