This document provides an introduction to catalysis. It defines catalysis as altering the rate of a reaction with a catalyst, which can increase or decrease the reaction rate. There are two types of catalysts: positive catalysts that increase reaction rate like enzymes and acids, and negative catalysts that decrease rate like lead. Catalysis can be homogeneous, with catalyst and reactants in the same phase, or heterogeneous with catalyst in a different phase. Promoters enhance catalyst activity while anticatalysts or poisons destroy it. Autocatalysis occurs when a reaction product catalyzes the same reaction.

1. WELCOME

2. CATALYSIS
Dr S Suprabha
Assistant professor
Department of Chemistry
VTMNSS College Dhanuvachapuram

3. DEFINITION
The phenomenon of altering the rate
of a reaction with the help of catalyst is
known as catalysis.
That is a catalyst may increase or decrease
the rate of a reaction

4. Catalysts are of two types,
1. Positive catalyst
These are substances that help hasten a chemical
reaction. Some typical examples include biological catalysts
like Amylase, Maltase, Protease, and Lipase; as well as
popular chemicals like sulfuric acid and manganese dioxide.
2. Negative Catalyst
These are substances that decreases the rate of a
chemical reaction. Lead tetraethyl as antiknock compound.
Glycerol in decomposition of H2O2. Ethanol in the oxidation
of chloroform

5. Homogeneous Catalysis
A catalytic process in which the catalyst and the
reactants are present in the same phase
Eg. Oxidation of SO2 to SO3 with
nitric oxide catalyst
2 SO2(g) + O2(g) ⇌ 2 SO3

6. Heterogeneous catalysts
In heterogeneous catalysis catalysts are in a
different phase than the reactants. For example,
the catalyst might be in the solid phase while the
reactants are in a liquid or gas phase
Eg:
.

7. PROMOTORS
• A substance which though itself not a catalyst ,
promotes the activity of a catalyst is called a
promoter.
• Eg: molybdenum or aluminium oxide promotes the
activity of iron catalyst in tne Haber process for the
manufacture of ammonia

8. ANTICATALYST
A substance which destroys the activity of the
catalyst is called anticatalyst or catalytic poison
and the process is called catalytic poisoning.
Eg: Platinum catalyst used in the oxidation of
sulphur dioxide is poisoned by arsenic oxide

9. AUTOCATALYSIS
When one of the products of a reaction itself act as a
catalyst for that reaction, the phenomenon is called
autocatalysis.
Eg:When oxalic acid is oxidised by acidified
potassium permanganate, mangonous sulphate
produced during the reaction act as a catalyst for
the reaction

10. THANK YOU