Catalysis: An introduction
Dr.Rabiul Hussain
School of Material Science & Engineering
Jimma Institute of Technolgy, Jimma
University
E-mail: rabiul786@gmail.com
Ph.No. +251-0966882081 (Ethiopia)
+91-9508832510 (India)
7/6/2020
DR.RABIUL HUSSAIN
1
OUTLINES
Introduction
What is catalysis?
History of Catalysis
Types of Catalysis
Characteristics of catalytic reactions
Field of Applications
What is Catalysis?
• The term “catalysis” was introduced as early as 1836 by Berzelius in order
to explain various decomposition and transformation reactions. He
assumed that catalysts possess special powers that can influence the
affinity of chemical substances. [Catalysis(Greek kata = wholly, lein = to
loosen)].
• A definition that is still valid today is due to Ostwald (1895): “a catalyst
accelerates a chemical reaction without affecting the position of the
equilibrium.”
• A catalyst is defined as a substance which alters the rate of a chemical
reaction, itself remaining chemically unchanged at the end of the
reaction. The process is called Catalysis.
Catalysis
• A catalyst which enhances the rate of a
reaction is called a Positive catalyst and the
process Positive catalysis or simply Catalysis.
• A catalyst which retards the rate of a reaction
is called a Negative catalyst and the process
Negative catalysis.
• Catalysis is the occurrence, study, and use of
catalysts and catalytic processes
Catalysis
• Wilhelm Ostwald proposed
its valid definition in terms
of the concepts of chemical
kinetics: “A catalyst is a
substance which affects the
rate of a chemical reaction
without being part of its
end products”.
• In 1909, Ostwald was
awarded the Nobel Prize in
Chemistry
for
his
contributions to catalysis.
Early History of Catalysis
• Neolithic age ( ~5000B.C.)
 Biocatalytic fermentation in wine manufacture.
• 500B.C.
Soap manufacture (hydrolysis of animal fats with
potash lye)
• 1500A.C.
Alchemists formed sulfuric acid by a mysterious
catalytic process
Early History of Catalysis
• 1831
Pelegrine Phillips (a Bristol vinegar manufacturer)
obtained the 1stknown patent in catalysis for the
reaction
SO2+ air ® SO3 (Pt sponge as catalyst)
 The catalyst used now-a-day is V2O5/ SiO2
• 1835
J.J. Berzelius coined the word “ catalysis”Greek
words “ cata” means “ down”“ lysis ” means “
split” or “ break”
Early History of Catalysis
• “ This new force, which is unknown until now, is common to both organic
and inorganic nature. I do not believe that it is a force completely
independent of electrochemical affinities; … It is more convenient to give
this force a separate name. I would therefore call this the catalytic force. I
would furthermore, call the decomposition of substances resulting from
this force catalysis, just as the decomposition of substances resulting from
chemical affinity is called analysis.” Berzelius
Early History of Catalysis
• 1909 Ostwald (German) received Nobel Prize
for studies of reaction rate over catalysts.
https://www.nobelprize.org/prizes/chemistry/1909/ostwald/biographical/
• 1912 Paul Sabatier (French) received Nobel
Prize for studies of catalytic hydrogenation of
organic compounds.
https://www.nobelprize.org/prizes/chemistry/1912/sabatier/facts/
https://www.nobelprize.org/prizes/chemistry/1909/ostwald/lecture/
https://www.nobelprize.org/prizes/chemistry/1912/sabatier/lecture/
Early History of Catalysis
• 1915
 Haber Process: N2+ 3H2
2 NH3(Fe catalyst)
• 1919 Fritz Haber (German) received Nobel Prize
<https://www.nobelprize.org/prizes/chemistry/1918/haber/lecture/>
EARLY HISTORY OF CATALYSIS
• 1880 Carl Groebe
– Accidentally broke a thermometer while stirring a
mixture of hot naphthalene and H2SO4
– phthalic anhydride & phthalic acid===dye
chemistry
• 1899
Arrhenius equation k = A exp( -Ea/RT)
• 1903 Ostward process
– 2NH3+ 7/2 O2 2NO2+ 3 H2O (Pt sponge as
catalyst) RESULT=== HNO3industry
Early History of Catalysis
• 1920 Sabatier published the 1st book on
catalysis
• 1923 Methanol synthesis
• 1930 Fischer-Tropsch Process:
• 1932 Langmuir (USA) received Nobel Prize
 For surface chemistry and Langmuir isotherm
Early History of Catalysis
• 1936 Modern era in catalysis
– Catalytic cracking of petroleum (acid treated clays
as catalyst)
– BET surface area
– Deuterium discovery isotope research
• 1963 Ziegler (German) &
Natta(Italian)received Nobel Prize for
stereoregulated polymerization catalyst
Early History of Catalysis
The Nobel Prize in Chemistry 1963 was awarded jointly to
Karl Ziegler and Giulio Natta "for their discoveries in the
field of the chemistry and technology of high polymers."
History of Catalysis
WORK: Often, chemical reactions are speeded up by surfaces, as in the case when
gaseous molecules come in contact with a metal surface. During the 1960s Gerhard
Ertl developed a number of methods for studying surface chemical reactions. Among
other things, he made use of techniques for producing a very pure vacuum, which
had been developed within the semiconductor industry. Gerhard Ertl was able to map
out details of a process of great importance in the production of artificial fertilizer:
the Haber-Bosch process in which nitrogen in the air is converted to ammonia via an
iron catalyst.
History of Catalysis
History of Catalysis
History of Industrial Catalysis
continued
History of industrial Catalysis
Characteristic of Catalytic Reactions
The following features or characteristics are common to most of the catalysts.
1) A catalyst remains unchanged in mass and chemical composition at the
end of the reaction.
• A small quantity of catalyst is generally needed to produce almost
unlimited reaction. For example, one ten-millionth of its mass of finely
divided platinum is all that is needed to catalyze the decomposition of
hydrogen peroxide.
On the other hand, there are catalysts which need to be present in
relatively large amount to be effective. Thus in Friedel-Crafts reaction,
anhydrous aluminium chloride functions as a catalyst effectively when
present to the extent of 30 per cent of the mass of benzene.
Characteristic of Catalytic Reactions
• 3) A catalyst is more effective when finely divided. In heterogeneous
catalysis, the solid catalyst is more effective when in a state of fine
subdivision than it is used in bulk.
• (4) A catalyst is specific in its action: While a particular catalyst works for
one reaction, it will not necessarily work for another reaction. Different
catalysts, moreover, can bring about completely different reactions for the
same substance. For example, ethanol (C2H5OH) gives ethene (C2H4) when
passed over hot aluminium oxide, but with hot copper it gives ethanal
(CH3CHO).
Characteristic of Catalytic Reactions
• (5) A catalyst cannot, in general, initiate a reaction: In most cases a
catalyst speeds up a reaction already in progress and does not initiate (or
start) the reaction. But there are certain reactions where the reactants do
not combine for very long period(perhaps years).
For example, a mixture of hydrogen and oxygen, which remains
unchanged almost in definitely at room temperature, can be brought to
reaction by the catalyst platinum black in a few seconds.
Thus it is now considered that the catalyst can initiate a reaction.
According to this view, the reacting molecules (in the absence of catalyst)
do not possess minimum kinetic energies for successful collisions. The
molecules rebound from collision without reacting at all.
Characteristic of Catalytic Reactions
• (6) A catalyst does not affect the final position of equilibrium, although it
shortens the time required to establish the equilibrium. It implies that in
a reversible reaction the catalyst accelerates the forward and the reverse
reactions equally. Thus the ratio of the rates of two opposing reactions i.e.,
the equilibrium constant, remains unchanged.
Characteristic of Catalytic Reactions
• (7) Change of temperature alters the rate of a catalytic reaction as it
would do for the same reaction without a catalyst.
Some catalysts are, however, physically altered by a rise in
temperature and hence their catalytic activity may be decreased. This is
particularly true with colloidal solutions like that of platinum, since a rise
in the temperature may cause their coagulation. In such a case the rate of
reaction increases up to a certain point and then gradually decreases. The
rate of reaction is maximum at a particular temperature called the
optimum temperature.
Types of Catalysis
• The numerous catalysts known today can be classified according to various
criteria: structure, composition, area of application, or state of
aggregation.
Classification of Catalysts
Main two classes:
1. Homogeneous catalysis
2. Heterogeneous Catalysis
• Also, there is a third types of catalysis known
as Enzyme catalysis which is largely of
biological interest.
Homogeneous Catalysis
• In homogeneous catalysis, the catalyst is in the same phase as the
reactants and is evenly distributed throughout. This type of catalysis can
occur in gas phase or the liquid (solution) phase.
Examples of Homogeneous Catalysis in Gas Phase:
Homogeneous Catalysis
Heterogeneous Catalysis
• The catalysis in which the catalyst is in a different physical
phase from the reactants is termed Heterogeneous catalysis.
• The most important of such reactions are those in which the
reactants are in the gas phase while the catalyst is a solid. The
process is also called Contact catalysis since the reaction
occurs by contact of reactants with the catalyst surface.
• In contact catalysis, usually the catalyst is a finely divided
metal or a gauze. This form of catalysis has great industrial
importance.
Heterogeneous Catalysis
Heterogeneous Catalysis
Application of Catalysis
• Four major sectors of the world economy; petroleum and energy
production, chemicals and polymer production, food industry and
pollution control, involve catalytic processes.
Application of Catalysis
• Catalysts are used to produce fuels such as gasoline, diesel, heating oil,
fuel oil etc.
• Production of plastics, synthetic rubbers, fabrics, cosmetics etc. involve
catalytic processes.
• Automobile emission catalysts are used to reduce emissions of CO, NOx
and hydrocarbons from mobile vehicles.
• The pharmaceutical industry uses catalysts for production of drugs that
are used to save lives and improve the health of people. Catalysts are also
widely used in food processing.
• More than 90 % of industrial processes actually use catalysts in one form
or the other.
Application of Catalysis
Pollution Control and Catalysis
Application to Catalysis
7/6/2020
DR. RABIUL HUSSAIN : 966882081
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