Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.
CATALYSIS 
Joel Cornelio 
I M Sc Analytical Chem 
St Aloysius College 
Mangalore
Definitions and Properties 
• To learn both these ideas, let’s imagine an 
experiment. 
• The experiment is a laboratory d...
Diagram
Steps in the Experiment. 
• Open the taps and let the N2 and H2 into the 
jar J. 
• No reaction occurs. 
• Now we insert t...
• Take the iron rod out and file it. 
• We get powdered iron.
• Weigh this iron powder, and put it inside the 
jar, keep the temperature between 400-450oC 
• There’s a tremendous incre...
Remove the iron powder out using a magnet and 
weigh it. 
There is no change in it’s weight. 
Put the iron back and Open t...
Terms in Catalysis 1 
• Catalyst: A substance that alters the rate of a 
reaction without any undergoing any change 
in it...
• Promoter: Substances that increase the 
catalytic activity, by increasing the number of 
active sites in the catalyst. 
...
• Homogenous Catalysis: Reaction where the 
catalysts are in the same phase as the 
reactants. 
e.g: Hydrolysis of ester i...
Properties 
• A small quantity of the catalyst is enough to 
catalyze a large quantity of reactants into 
products. 
• Mos...
• A catalyst cannot start the reaction by itself. 
• Catalytic activity increases as surface area of 
catalyst increases. ...
• If two catalysts can catalyze the same reaction, 
the better catalyst is the one which produces a 
greater reduction in ...
• The reaction occurs on the surface of the 
catalyst, at special sites called active sites. 
Increasing surface area, inc...
2
2
So how do catalysts work..? 
• All molecules posses energy, and during 
reaction they undergo collision. 
• Only those col...
• Catalysts provide an alternate pathway for 
reaction. 3 
• This alternate pathway requires lower 
activation energy and ...
2
Transition metals used as catalysts, provide vacant 
d orbitals for bonding with the Π electrons of the 
substrate 
2
WILKINSON’S CATALYST
Speeding Up Organic Reactions 7 
• Chloromethane reacts with hydroxyl to yield 
methanol. 
CH3Cl + OH- CH3OH + Cl- 
• The ...
Applications. 
• Every chemical industry uses catalysts to 
produce chemicals. 
• In biological systems, enzymes catalyze ...
• Photosynthesis is the best and most 
significant aspect of catalysis, by which we get 
food. 
• Pharmaceutical industrie...
CATALYTIC CONVERTER
References 
1. Puri, Sharma and Pathania: Principles of 
Physical Chemistry, VPC 2003 
2. Matthews, Philip: Advanced Chemi...
6. March, Jerry: Advanced Organic Chemistry, 
4th ed, Wiley 2005. 
7. Mukherji and Singh: Reaction Mechanism in 
Organic C...
Catalysis
Upcoming SlideShare
Loading in …5
×

Catalysis

293 views

Published on

  • Be the first to comment

  • Be the first to like this

Catalysis

  1. 1. CATALYSIS Joel Cornelio I M Sc Analytical Chem St Aloysius College Mangalore
  2. 2. Definitions and Properties • To learn both these ideas, let’s imagine an experiment. • The experiment is a laboratory demo of the Haber’s process of NH3 production. • Requirements include three cylinders (C1, C2 and C3) and large jar (J) made of metal, a file • Chemicals required are N2 and H2 and H2S gases separately in the three cylinders, an Iron rod, Molybdenum. • Other things required are a burner and a lot of your attention.
  3. 3. Diagram
  4. 4. Steps in the Experiment. • Open the taps and let the N2 and H2 into the jar J. • No reaction occurs. • Now we insert the iron rod into the jar. • Reaction does not begin, no ammonia formed. • Now we heat the jar to about 400 to 450oC. • Reaction begins, rate increases.
  5. 5. • Take the iron rod out and file it. • We get powdered iron.
  6. 6. • Weigh this iron powder, and put it inside the jar, keep the temperature between 400-450oC • There’s a tremendous increase in the reaction rate. • Now add a weighed amount of molydenum into the jar. • Reaction rate is highest.
  7. 7. Remove the iron powder out using a magnet and weigh it. There is no change in it’s weight. Put the iron back and Open the third tube, and let the H2S gas into the chamber. Rate of the reaction rapidly decreases. If the iron is weighed now, a small change in it’s weight is seen.
  8. 8. Terms in Catalysis 1 • Catalyst: A substance that alters the rate of a reaction without any undergoing any change in itself. • Substrate: The molecule subject to catalysis. • Positive Catalyst: increases rate of reaction. • Negative Catalyst: decreases rate of reaction.
  9. 9. • Promoter: Substances that increase the catalytic activity, by increasing the number of active sites in the catalyst. (In other words, the catalyst of a catalyst.) • Catalytic Poison: decreases or stops catalytic activity by blocking the active sites of the catalyst. 4
  10. 10. • Homogenous Catalysis: Reaction where the catalysts are in the same phase as the reactants. e.g: Hydrolysis of ester into alcohol and acid catalyzed by H+ ions • Heterogeneous Catalysis: Reaction where the catalyst and reactant are in different phases. e.g: Contact process for H2SO4 production catalyzed by Pt gauze or V2O5.
  11. 11. Properties • A small quantity of the catalyst is enough to catalyze a large quantity of reactants into products. • Most catalysts are highly selective. • Though reactants are same, the type of catalyst used may decide the products formed. 8 Eg. Pt C2H2 + 2H2 C2H6 Lindlar’s Catalyst C2H2 + H2 C2H4
  12. 12. • A catalyst cannot start the reaction by itself. • Catalytic activity increases as surface area of catalyst increases. • Catalysts are thermolabile, this effect is very well pronounced in enzymes. • Catalytic activity is maximum at a catalyst’s optimum temperature. • A catalyst does not alter the position of the equilibrium, instead it helps in achieving the equilibrium faster.
  13. 13. • If two catalysts can catalyze the same reaction, the better catalyst is the one which produces a greater reduction in activation energy. e.g. Activation energy for the decomposition of H2O2 for different catalysts. 8 Catalyst EA, kJ/mol None 75 MnO2 58 I- 56 Colloidal Pt 49
  14. 14. • The reaction occurs on the surface of the catalyst, at special sites called active sites. Increasing surface area, increases the number of active sites available for catalysis. • In homogenous catalysis, esp. in liquids, the rate of the reaction is proportional to the concentration of the catalyst.
  15. 15. 2
  16. 16. 2
  17. 17. So how do catalysts work..? • All molecules posses energy, and during reaction they undergo collision. • Only those collisions result in chemical reaction, in which the colliding molecules are associated with a certain minimum amount of energy, called the Threshold Energy. • The excess of energy that molecules have to gain to reach the threshold energy is called Activation energy. 1 • Ea = Et - Ei
  18. 18. • Catalysts provide an alternate pathway for reaction. 3 • This alternate pathway requires lower activation energy and is easier to achieve, and a larger number of molecules can react and yield products. • All these factors aid in increasing the rate of the reaction, and that is what catalysis is all about.
  19. 19. 2
  20. 20. Transition metals used as catalysts, provide vacant d orbitals for bonding with the Π electrons of the substrate 2
  21. 21. WILKINSON’S CATALYST
  22. 22. Speeding Up Organic Reactions 7 • Chloromethane reacts with hydroxyl to yield methanol. CH3Cl + OH- CH3OH + Cl- • The reaction is much faster when iodide ions are used, since they act as excellent nucleophiles and leaving groups. • CH3Cl + I- CH3I + Cl- • CH3I + OH- CH3OH + I-
  23. 23. Applications. • Every chemical industry uses catalysts to produce chemicals. • In biological systems, enzymes catalyze a variety of biochemical reactions. 8 • e.g. • Animals use enzymes for their defense, esp snakes. (snake venom is also an enzyme.)
  24. 24. • Photosynthesis is the best and most significant aspect of catalysis, by which we get food. • Pharmaceutical industries use catalyst for production of various drugs and medicines. • In catalytic converters of vehicles which aid in reducing emissions of harmful exhaust gases.
  25. 25. CATALYTIC CONVERTER
  26. 26. References 1. Puri, Sharma and Pathania: Principles of Physical Chemistry, VPC 2003 2. Matthews, Philip: Advanced Chemistry, Cambridge University Press, 2006 3. Upadhyay, Santhosh: Chemical Kinetics and Reaction Dynamics 4. Richard I. Masel: Principles of Adsorption and Reaction on Solid Surfaces 5. D’Mello, Caroline: Organic reaction mechanisms, Pearson, 2006
  27. 27. 6. March, Jerry: Advanced Organic Chemistry, 4th ed, Wiley 2005. 7. Mukherji and Singh: Reaction Mechanism in Organic Chemistry, Macmillan 1984 8. INTERNET

×