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CI 10.4

Learn about catalysts and their role in speeding up chemical reactions. Discover the different types of catalysts and how they work, including the process of adsorption and bond formation. Explore catalyst poisoning and methods for cleaning and regenerating catalysts.

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CI 10.4

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  1. CI 10.4 What is a catalyst?

  2. Catalysts • Speed up the rate of a chemical reaction • Are not chemically changed or used up in the reaction • May be specific for a particular reaction – applies especially to enzymes in biological reactions

  3. Types of catalysts • Homogeneous catalysts –reactants and catalyst in same state • Heterogeneous catalysts – reactants and catalysts in different states

  4. H H C CH H H H H H How do heterogeneous catalysts work? • Catalyst is usually a solid Catalyst surface

  5. H H • Reactants are adsorbed onto catalyst surface- i.e. weak bonds formed between reactants and catalysts H H C CH H H H

  6. H H C CH H H H H H • Bonds within reactant molecules are weakened and break

  7. H H C CH H H H • New bonds form between the reactants H H

  8. H H C CH H H H H • New bonds form between the reactant molecules H

  9. H H H C CH H H H H • The product(s) leave the catalyst surface

  10. Catalyst poisoning • In heterogeneous catalysis • Catalyst poisoned by a chemical binding to surface • Poison bonds irreversibly with catalyst • Sulphur and lead are two examples of catalyst poisons

  11. Cleaning a catalyst • Catalysts can sometimes be regenerated by blowing hot air over catalyst – oxidises chemicals on surface • Used to remove carbon (soot) after catalytic cracking

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