Carbon compounds as fuels and feedstock

• Crude oil:

  • Is a finite resource found in rocks
  • Is the remains of an ancient biomass consisting mainly of plankton that was buried in mud
  • Is a mixture of a very large number of compounds
  • Most compounds in crude oil consist of molecules made up of hydrogen and carbon only (hydrocarbons), with most being alkanes
  • It is possible to separate the substances in the mixture by physical methods including distillation
• Hydrocarbons have the general formula: CnH2n+2

  • Alkane molecules can be represented by methane, ethane, propane, and butane
  • Fractional distillation separates the many hydrocarbons in crude oil into fractions with similar numbers of carbon atoms
• The fractions from crude oil can be processed to produce fuels and feedstock for the petrochemical industry

  • Fuels such as petrol, diesel oil, kerosene, heavy fuel oil, and liquefied petroleum gases are produced from crude oil
  • Petrochemical industry produces materials like solvents, lubricants, polymers, and detergents
  • Carbon atoms can form families of similar compounds, leading to a vast array of natural and synthetic carbon compounds
• Properties of hydrocarbons:

  • Shorter molecules are less viscous and more runny
  • Longer molecules are more viscous
  • Shorter molecules have lower boiling points and are more flammable
  • Hydrocarbons are burnt as fuel, producing energy through oxidation of hydrogen and carbon
• Cracking:

  • Hydrocarbons can be cracked to produce smaller, more useful molecules by heating them to vaporize
  • Processes include catalytic cracking and steam cracking
  • Cracking produces alkenes with the general formula CnH2n, containing at least one double carbon-carbon bond
  • Alkenes like ethene and propene react with bromine water, turning it colorless due to their double bond making them more reactive
  • Alkenes are used for producing other chemicals like polymers
  • Products from cracking are useful as fuels due to shorter chains and increased flammability
• Equations for cracking:

  • Ensure the same number of carbons and hydrogens on each side of the equation
  • Going from a bigger molecule to usually 2 smaller molecules
  • Example: C6H14 → C2H4 + ?, calculate the remaining carbons and hydrogens to find the other product: C4H10