This document provides an overview of chemical catalysis. It defines a catalyst as a material that increases the rate of a chemical reaction without being consumed. There are two main types of catalysis: homogeneous catalysis involving catalysts in the same phase as reactants and heterogeneous catalysis using catalysts in a different phase. Catalysts can be classified based on their physical state, composition, and mechanism of action. Key concepts discussed include promoters, catalytic poisoning, autocatalysis, and how catalysts reduce the activation energy of reactions. Common catalyst preparation methods like precipitation, adsorption, and impregnation are also outlined.

1. Chemical Surface and Catalyst
Masters Lectures
Lecture : 1
catalyst
Asst. Prof. Firas H. Abdulrazzak
Physical chemistry
College of Education for Pure Science
Chemistry Dep.
Diyala University

2.  What is catalyst
 What is CATALYSIS
 TYPES OF CATALYSIS
 HOMOGENEOUS CATALYSIS
 HETEROGENEOUS CATALYSIS
 CHARACTERISTICS OF CATALYTIC
 REACTIONS
 PROMOTERS
 CATALYTIC POISONING
 AUTOCATALYSIS
 NEGATIVE CATALYSIS
 ACTIVATION ENERGY AND
CATALYSIS

3. A catalyst is as a materials can alters the rate of
reactions, without any chemically changed such
consumed or destroyed at the end of the reaction.
Catalysis is an action by catalyst.
 Positive catalyst :A catalyst which enhances the rate of a
reaction and the process Positive catalysis.
 Negative catalyst :A catalyst which retards the rate of a
reaction and the process Negative catalysis.

4. Classification of catalysts
which depend on many physiochemical properties:
Classification by physical state
gas
liquid
solid
Classification by nature of materials
Inorganic
Organic
Classification by the
mechanism of reactivity
Homogeneous
Heterogeneous
Classification by activity
Acid-base catalysts
Enzymatic
Photocatalysis
Electrocatalysis

5. The ideal properties of catalyst
o The mass of catalyst remains without any lose with kept the
content after the reaction.
o The mass of the catalyst which needed to catalysis the
reaction mostly needed small amounts.
o selectivity Byproducts should be minimized.
o can not initiate the reaction or create new equilibrium state
o Stability
o Particle size mostly nanometres in diameters

6. Catalyst components
 Active phase
Where the reaction occurs (active sites) (mostly metal/metal
oxide)
 Promoter or stimulus
 Modified with Electric groups
 Poison resistant promoters
 Selectivity enhancement
 Support / carrier
 Increase
• mechanical strength
• surface area
• activity
Promoter
A substance which,
though itself not a
catalyst, promotes
the activity of a
catalyst
MOSTLY IN
HETROGENOUS
REACTION

7. Theories of promoter reactivity
I. Change of Lattice Spacing.
II. Increase of Peaks and Cracks.
 AUTOCATALYSIS
$$$-When one of the products of reaction itself acts as a catalyst
for that reaction.
Hydrolysis of an Ester Oxidation of Oxalic acid
Decomposition of Arsine

8. CATALYTIC POISONING
A substance which destroys
the activity of the catalyst
to accelerate a reaction
Explanation of Catalytic Poisoning
#The poison is adsorbed on the
catalyst surface in preference to
the reactants
--------------------------------------
----------
#The catalyst may combine
chemically with the impurity
 poisoning a catalyst
 breaking a chain
reaction
Negative Catalysis

9. ACTIVATION ENERGY AND CATALYSIS

10. Preparation of catalysts
Home work????????
Precipitation
To form non-soluble precipitate by
desired reactions at certain pH and
temperature
Adsorption & ion-exchange
Cationic: S-OH+ + C+  SOC+ + H+
Anionic: S-OH- + A-  SA- + OH-
I-exch. S-Na+ + Ni 2+ D S-Ni 2+ + Na+
Impregnation
Fill the pores of support with a
metal salt solution of sufficient
concentration to give the correct
loading.
Dry mixing
Physically mixed, grind, and fired

11. 1-Intermediate Compound Formation
theory (Homogeneous )
THEORIES OF CATALYSIS
2-The Adsorption theory. (Heterogeneous)
 an intermediate compound produce with one of the
reactants.
 an intermediate compound reacts with the second
reactant to yield the product, releasing the catalyst
A + B ⎯C⎯→ AB
A + C → AC
Intermediate
AC + B → AB + C
 a reaction between two gases catalyzed by a solid.
 the catalyst functions by adsorption of the reacting
molecules on its surface.
Step 1. Adsorption of Reactant molecules
Step 2. Formation of Activated complex
Step 3. Decomposition of Activated complex
Step 4. Desorption of Products

12. Activated
complexes
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14. Active Centres on Catalyst Surface
pore
porous
solid
Active site
An Active site is a point on the surface that can form
strong CONACTION with an adsorbed atom or
molecule.

15. Classification of Solid Catalysts
1-Unsupported (Bulk) Catalysts
 Metal Oxides
• Simple Binary Oxides
• Complex Multicomponent Oxides
 Metals and Metal Alloys
 Carbides and Nitrides
 Carbons
 Ion-Exchange Resins and Ionomers
 Molecularly Imprinted Catalysts
 Metal – Organic Frameworks
 Metal Salts
 Supported Metal Oxide Catalysts
 Supported Metal Catalysts
 Supported Sulfide Catalysts
 Hybrid Catalysts
 Ship-in-a-Bottle Catalysts
 Polymerization Catalysts
3-Coated Catalysts
2-Supported Catalysts
 Supports
 Surface-Modified Oxides

16. Thank you