Engineering Chemistry S Datta

148 ENGINEERING CHEMISTRY
The mechanism of hydroformylation using cobalt carbonyl as catalyst is shown in the
scheme.
1
Co (CO)
2
2 8
–
1 1
H
2 2
+ H
2 2
HCo(CO) 4
RCH CH CHO
2 2
+CO
–CO
RCH=CH 2
Hydrogenolysis
of Co-acyl
HCo(CO) 3
Insertion of
alkene into
Co—H
RCH CH Co(CO)
2 2 3
RCH CH CCo(CO)
2 2 3
O
RCH CH Co(CO)
2 2 4
CO
O
Insertion of —C into
Co-alkyl
Fig. 6.8
EXERCISES
1. Define with illustrations:
(i) catalysis,(ii) positive catalysis,(iii) negative catalysis.
2. What do you mean by (i) homogeneous and (ii) heterogeneous catalytic reactions?
3. What are catalyst poisons and promoters?
4. Discuss a few important catalytic processes.
5. “A catalyst doesn’t affect the final state of equilibrium, although it shortens the time required to
establish the equilibrium.”—explain.
6. Give a brief account of the various theories of the mechanism of catalysis.
7. What will be a more effective catalyst—platinum as a lump or finely divided platinum? Give
reason.
8. How does a catalyst accelerate the speed of a reaction? Explain with proper energy profile diagram.
9. Write notes on:
(i) Adsorption theory of catalysis,
(ii) Enzyme catalysis.