1. HETEROGENOUS CATALYST
Akamigas Balongan

2. Catalyst
A substance which changes the speed of a reaction without being used itself is called a catalyst.
The phenomenon of increasing the rate of reaction by the use of catalyst is called catalysis.
If а catalyst increases (accelerates) the speed of а reaction, it is called а positive catalyst and the phenomenon is called positive catalysis. On the other hand, if а catalyst decreases (retards) the speed of а reaction, it is called а negative catalyst and the phenomenon is called negative catalysis.

3. Catalyst lowers the activation energy for both forward and reverse reactions.
Type of catalyst :
Homogenous catalyst : catalyst and reactant in one phase
Heterogenous catalyst : catalyst and reactant in different phase

4. Catalysist
Catalysts increase reaction rate without themselves being changed
Can accelerate a reaction in both directions
Do not affect the state of equilibrium of reaction
simply allow equilibrium to be reached faster

5. Properties heterogeneous catalyst
Simple construction
Easy separated from mixed reaction
Stable and resistence for high temperature
Easy to construct in pellet form

6. Heterogenous catalyst
Adsorption (STEP 1)
Incoming species lands on an active site and forms bonds with the catalyst. It may use some of the bonding electrons in the molecules thus weakening them and making a subsequent reaction easier
Reaction (STEPS 2 and 3)
Adsorbed gases may be held on the surface in just the right orientation for a reaction to occur.
This increases the chances of favourable collisions taking place.

7. Heterogenous catalyst
Desorption (STEP 4)
There is a re-arrangement of electrons and the products are then released from the active sites

8. Adsorption reactan Desorption product
Reaction of adsorbed intermediates

9. CATALITYC ACTION

10. REACTION
HYDROGENATION
OXIDATION
OTHER REACTION

11. Oxide catalyst

12. Metal Catalyst

13. Heterogenous catalyst
Metals Ni, Pt hydrogenation reactions
Fe Haber Process
Rh, Pd catalytic converters
Cobalt
Copper
Oxides Al2O3 dehydration reactions
V2O5 Contact Process
Zeolit
Clay

14. Many cases, the choice of catalyst could affect product
Ethanol undergoes different reactions depending on the metal used as the catalyst.
The distance between active sites and their similarity with the length of bonds determines the method of adsorption and affects which bonds are weakened.

16. CATALYTIC REACTION

17. Mechanism of Catalytic Reaction
Example : heterogeneous catalytic hydrogenation of ethylene
Σ ΔFi < ΔF*

18. Surface area catalyst attract atom surrounding gas and solid.
Catalyst surface is an irregular crystal which has different form side, making its “attracting force” in each atoms were different.
The surface catalyst always has “active center”, where the increasing physic and chemist adsorption phenomena take place.

19. Irregular crystal form

20. Physic Adsorption Not specified
The solid molecule force in surface to fluid molecule of fluid is weak
Can’t explain the catalytic reaction
The increasing temperature, the decreasing physic adsorption
The physic adsorption was concern for determining the property of solid catalyst ( surface are, size distribution)

21. Chemist Adsorption
The force of chemist adsorption > physic adsorption
According to Langmuir, the adsorbed molecule are held to surface by valence energy are the same type as those occurring between atoms in molecules.
High heat adsorption

22. Chemist Adsorption
Non- Activated : activation energy near zero, occur rapidly
Activated : rate varies with temperature, process slow

25. Transfer massa liquid - solid

26. Transfer massa liquid - solid

27. Transfer massa gas - solid

28. PHYSICAL PROPERTIES OF CATALYST
High porosity
Surface area active center
Void volume
Solid material density
Void volume distribution

29. VOID VOLUME Micropore : void spaces within the particels
Macropore : void regions between particels

30. CATALYST CLASIFICATION
Conductor : metals ( Silver, Platinum, Vanadium, Iron) which has chemisorption properties
Semiconductor : Oxide (NiO, Cu2O, ZnO) have capabilities to exchange electron
Insulator : Silica, Alumina and their combined.

31. Metal chemisorb oxygen and hydrogen usually effective for catalyst for oxidation-reduction, hydrogenation-dehydrogenation. Example SO2 and Ni effective for hydrogenation.
The metal oxide, as semiconductor, catalyze the same kind of reactions, but need high temperatures. Due to relative strength of chemisorption bonds with O2 and CO attached metals, theses gases are poisons when metals are employed as hydrogenation catalyst

32. CATALYST PREPARATION
Promotor/ carier / support : a substance added during the preparation catalyst which improve activity, selectivity, or stabilized catalytic agent so as to prolong its life. (Ex : Al2O3, CaO, K2O)
Inhibitor : when added I small amounts during catalyst manufacture, it lessens activity, stability, or selectivity. (Ex: halogen group)

33. Catalsyt support
Example : Alumina, Silica, Carbon ( Carbon black, charcoal, graphite)

34. Effect heating on catalyst support

35. Effect particle size of metal support

36. Model catalyst support in support particels

37. Egg shell : type of catalyst having the active component on or near the surface is more efficient
Uniform : is preferred for reactions in which mass-transfer limitations have been removed.
Egg Yolk : action medium contains a catalyst poison or inhibitor, then the use of an “egg white” or “egg yolk” catalyst is desirable so the exterior of the support can adsorb the poison before it can reach the active metal