Hetergenous

• Features of heterogenous catalysts:

  1. Catalyse reactions on their surface
  2. On the surface, there are active sites
  3. An attachment to the metal is called an adsorption
• Type of Catalysis

  • Catalyst
  • Homogeneous
  • Same phase as reagents
  • Heterogeneous
  • Different phase to reagents
• The reaction

  • The Contact Process converts sulfur dioxide to sulfur trioxide. Adding this to water produces sulfuric acid.
  • The equation is:
  • 2SO2(g) + O2(g) ⇌ 2SO3(g)
  • This is then converted to sulfuric acid:
  • SO3(g) + H2O(l) → H2SO4(aq)
• The reaction

  • The equation for the reaction is:
  • N2(g) + 3H2(g) ⇌ 2NH3(g)
  • This reaction is done in a sealed vessel at 200atm pressure and 450oC. It has a very low yield so we recycle unreacted gas and run the process again.
• Poisoning

  • The iron catalyst is readily poisoned by the presence of sulfur.
  • Iron sulfide (FeS) can form if sulfur is present.
  • The hydrogen gas is often produced from methane. It will contain some impurities, of which sulfur is one.
  • The Haber Process catalyst is slowly poisoned.
• Why a catalyst is so important in the Haber Process?

  1)Increases the rate so a lower temperature can be used

  2Since the reaction is exothermic, the lower temperature helps favour the forward reaction

  3)Overall, this makes the production of ammonia easier