fractional distillation and cracking

• what is crude oil?

  mixture of mainly alkane hydrocarbons from remains of sea creatures and plants from millions of years ago
• how is crude oil separated?

  fractional distillation
• what is a fraction?

  mixture of hydrocarbons with similar boiling points
• where does fractional distillation occur?

  fractioning column
• what is the process of fractional distillation?

  1. crude oil heated so it vaporises
  2. column has temperature gradient
  3. fractions separate due to different boiling points
  4. shorter hydrocarbon chains have lower boiling points so condense at top
• what is cracking?

  process that breaks larger alkanes into smaller molecules

  breaks C-C and C-H bonds
• what is the general equation for cracking?

  larger alkane chain --> smaller alkane chain + alkene + hydrogen gas
• what is thermal cracking?

  heating molecules to 700-1200K at high pressure of 7000KPa

  one product must be alkene

  free radical intermediate
• what is atmospheric pressure?

  100KPa =100,000 Pa
• what is catalytic cracking?

  use zeolite catalyst to break bonds, 720K, pressure slightly above atmospheric

  products are branched alkanes and carbocation intermediate