Adapted from powerpoint created by Lance Hammell

1. CATALYSTS AND ENZYMES Adapted from powerpoint created by Lance Hammell

2. N C C N O + O O + O O O Chemical Reaction Reactant Bonds Broken, Product Bonds Made NO2 (g) + CO (g) -> NO (g) + CO2 (g) Lisa R. Arnold South Georgia College 13.1

3. C N O O O Molecular Collision Theory • Reactants must collide with • correct orientation • enough energy, Ea Incorrect Orientation O C N O O Correct Orientation Lisa R. Arnold South Georgia College

4. Reaction Profile Reaction path for conversion of A + B into AB Abdul-Rahman Al-Betar

5. A + B C + D Endothermic Reaction Exothermic Reaction The activation energy (Ea) is the minimum amount of energy required to initiate a chemical reaction. Lisa R. Arnold South Georgia College 13.4

6. Activation Energy.. • ..is energy needed so there is enough energy to break reactant bonds. • ..is the energy needed to get molecules in the correct orientation. • ..is the energy needed to reach the transition state or activated complex Lisa R. Arnold South Georgia College

7. Activation Energy Definition The Activation Energy (Ea) determines how fast a reaction occurs, the higher Activation barrier, the slower the reaction rate. The lower the Activation barrier, the faster the reaction Abdul-Rahman Al-Betar

8. What are catalysts? • Simply put, catalysts are substances which, when added to a reaction, increase the rate of reaction by providing an alternate reaction pathway with a lower activation energy (Ea). • They do this by promoting proper orientation between reacting particles. • In biochemistry, catalysts are known as enzymes.

9. Activation Energy Catalyst Affect Catalyst lowers the activation energy for both forward and reverse reactions. Abdul-Rahman Al-Betar

10. Activation Energy Catalyst Affect This means , the catalyst changes the reaction path by lowering its activation energy and consequently the catalyst increases the rate of reaction. Abdul-Rahman Al-Betar

11. Why do we need catalysts? CEBC video

12. H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H2 absorption  palladium hydride Adsorption and Absorption H2 adsorption on palladium Surface process bulk process Abdul-Rahman Al-Betar

13. Catalytic Converters • One common application for catalysts is for catalytic converters. • Catalytic converters are found in automobiles. • Their role is to reduce to emissions of harmful gases (CO, VOC’s, NOx) that are the result of the combustion of fuel in vehicle engines.

14. Specifics of Catalytic Converters • Most modern cars are equipped with three-way catalytic converters. "Three-way" refers to the three regulated emissions it helps to reduce -- carbon monoxide, VOCs and NOx molecules. A: Reduction Catalyst B: Oxidation Catalyst C: Honeycomb Ceramic Structure • The converter uses two different types of catalysts, • Both types consist of a honeycomb-shaped ceramic structure coated with a metal catalyst, usually platinum, rhodium and/or palladium.

15. Step 1: The Reduction Catalyst • The reduction catalyst is the first stage of the catalytic converter. • It uses platinum and rhodium to help reduce the NOx emissions. When an NO or NO2 molecule contacts the catalyst, the catalyst rips the nitrogen atom out of the molecule and holds on to it, freeing the oxygen in the form of O2. • The nitrogen atoms bond with other nitrogen atoms that are also stuck to the catalyst, forming N2. • The equation for this is as follows: 2 NO => N2 + O2or 2 NO2 => N2 + 2 O2

16. Step 2: The Oxidization Catalyst • The oxidation catalyst is the second stage of the catalytic converter. • It reduces the unburned hydrocarbons and carbon monoxide by burning (oxidizing) them over a platinum and palladium catalyst. • This catalyst aids the reaction of the CO and hydrocarbons with the remaining oxygen in the exhaust gas. • The equation for this process is as follows: 2 CO + O2 => 2 CO2

17. Once this process is complete, most of the harmful substances have been broken down into harmless ones such as N2, O2, and CO2. Catalytic Converter Summary

18. Applications of Catalysts Fuel Cells

19. THE END