Separation of Lanthanides/ Lanthanides and Actinides
Physical chemistry 2_Catalysis.pptx
1. CATALYSIS
Dr.K.V.Nagalakshmi
&
Dr. B. Santosh Kumar
https://www.researchgate.net/figure/Diagram-representing-catalyst-lowering-the-activation-energy-
thereby-accelerating-the_fig1_328121341
2. Importance of Catalysis
In the chemical industry and industrial
research, catalysis play an important role
Contact process-H2SO4
Haber’s Process-NH3
Automobiles use catalytic converters to
treat exhaust.
All important biochemical reactions are
catalyzed by molecules called enzymes.
3. The first known use of inorganic catalysts is
from 1552 -used sulfuric acid to catalyze the
conversion of alcohol to ether
catalytic action of MnO2 on the thermal
decomposition of KClO3, the basis for the
preparation of oxygen .
KClO3 2KCl+ 3O2
The first time a catalyst was used in the
industry was in 1746 by J. Hughes in the
manufacture of sulfuric acid by lead
chamber process
4. A +B Products
Catalyst is a substance that alters the rate of a chemical
reaction without being consumed in that reaction.
Catalysis is the chemical reaction brought about by a
catalyst.
For a chemical reaction to take place, it requires a certain
minimum amount of energy, called its activation energy
Ea.
The Substance that lowers activation energy-Catalyst
5.
6. 1.Positive catalyst - increases the rate of the
reaction.
• Haber Process
3H2 + N2 ==> 2NH3(Fe)
• Contact Process
2SO2 + O2 ==> 2SO3 (Pt/V2O5)
• Hydrogenation of C=C
(hardening of oil - vegetable oil to margarine)
CH2CH2 + H2 ==> CH3CH3 (Ni/Pd/Pt)
7. 2.Negative catalyst- decreases the rate of
the reaction.
To slow down the decomposition of H2O2 -
glycerine
To suppress the oxidation of CHCl3 -
Ethanol
To minimize knocking in internal
combustion engine-TEL
8. Promoter -increase the activity of a
catalyst in a chemical reaction.
By itself the promoter has little or
no catalytic effect.
For example, in Haber's process , traces of
molybdenum increases the activity of
iron catalyst. ...
In the hydrogenation of oils, the catalytical
activity of nickel is enhanced by adding
copper.
10. In auto catalysis, the reaction is catalyzed by
one of its products and that catalyst is called
Auto catalyst.
.
11.
12. The catalyst remains unchanged in its mass
and chemical composition at the end of the
reaction
A small quantity of the catalyst is required.
The catalyst does not change the
equilibrium constant. But the equilibrium
approaches earlier. K=k1∕k-1
The catalyst can not make impossible
reaction to occur and does not intiate a
reaction.
13. The catalyst is specific in nature. It means by the
change of catalyst, nature of the products changes
The catalyst exhibits maximum activity at a
particular temperature which is known as optimum
temperature.
16. catalyst and reactants are in the same phase
transition metal ions are often involved - oxidation
state changes
Eg-Fe(iii) catalysed persulphate and iodide reaction
S2O8
2-+ 2I- Fe(ii) 2SO4
2- + I2
18. Homogeneous catalysis
1.Reactants and catalysts are
in same phase.
2.The reaction occurs in liquid
or gaseous phase.
3.Active sites are distributed
throughout the homogeneous
phase.
4.Only one type of active site is
available. Highly selective.
5.Catalyst recovery is difficult, it
requires distillation or
extraction.
Heterogeneous catalysis
1.Reactants and catalysts are
in different phase
2.The reaction occurs on the
surface of solid
3.Active sites are present at
the surface.
4.Few sites catalyse the
reaction, other sites catalyse
other side reaction-Low
selectivity.
5.There is little difficulty in
separating and recycling the
catalyst.
20. A+ B C AB ------gaseous state
Reactants Products
Catalyst
Mechanism:
(i) A + C AC
Reactant Catalyst Intermediate compound (lower energy)
(ii) AC + B AB + C
Intermediate another product catalyst
compound reactant regenerated
22. explains the mechanism of heterogeneous catalysis.
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-Formation of product
Step 4-Desorption of products
23.
24.
25. 1. Promoter changes lattice structure of catalyst Increase in
peaks and cracks thereby increasing the active sites on the
surface and hence the rate of reaction.
26. 1. The poison is adsorbed on the catalyst surface in preference to
the reactants.
2. The catalyst may combine chemically with the impurity.
27.
28. Hydrolysis of lactones and amides-Specific acid
base catalysed reaction.
Hydrolysis of ortho esters –General acid
catalysed
Hydrolysis of Nitramide-General base catalysed
Mutarotation of glucose and enolisation of
ketone-General acid- base catalysed
29.
30.
31.
32. If the proton is transferred to water present in
the medium-Protolytic mechanism
If the proton is transferred to conjugate base
present in the medium-Prototropic mechanism
40. Numerous reactions that occur in the bodies of
animals and plants to maintain the life process are
catalysed by enzymes. The enzymes are, thus,termed
as biochemical catalysts and the phenomenon is
known as biochemical catalysis.
They are actually protein molecules of high molecular
mass
42. (i)Most highly efficient: One molecule of an enzyme
may transform one million molecules of the reactant
per minute.
(ii)Highly specific nature: Each enzyme is specific
for a given reaction.
For example, the enzyme urease catalyses the
hydrolysis of urea only.
(iii) Highly active under optimum temperature
(iv) Highly active under optimum pH
(v) Activity is increased by activator and
inhibited by inhibitor
51. Rate =
K2[E]O[S]
[S] + km
Where km is Michaelis menton constant = (k-1 +k2)/k1)
Case (i) : if [S] is very low then Ignore [S].
Rate =
K2[E]O[S]
km
i.e. Rate is proportianal to first power of substrate
concentration.---First order kinetics
52. Case (ii) : if [S] is high then Ignore km.
Rate =
K2[E]O[S]
[S]
= K2[E]O
Rate is independent of
substrate concentration.
Zero order kinetics.
53. When enzyme is saturated with substrate----Rate
reaches its limiting value.
i.e.[E]0 =[ES], no free enzyme [E]
Rate of reaction = K2 [ES] = K2 [E0] = Vmax
( Maximum velocity)
54. k2 [E0] = Vmax
Rate =
K2[E]O[S]
[S] + km
Rate =
Vmax [S]
[S] + km
1
𝑅𝑎𝑡𝑒
=
[S] + km
Vmax [S]
1
Rate
=
[S]
Vmax [S]
+
km
Vmax [S]
59. Catalysts can:
Make a reaction possible under achievable
conditions.
Reduce the necessity of expensive &
dangerous conditions.
Generate high yields and high product purity.
Catalysis is the backbone of many industrial processes,
to turn raw materials into useful products
60. Industrial Process Catalyst Used
Haber’s process for manufacture of
ammonia
Finely divided iron + Mo as promoter
Ostwald’s process for manufacture of nitric
acid
Platinised asbestos
Lead chamber process for manufacture of
H2SO4
Nitric oxide
Contact process for manufacture of H2SO4 Platinised asbestos or vanadium
pentoxide
Deacon’s process for manufacture of
chlorine
Cupric chloride
Bosch’s process for manufacture of
hydrogen
Ferric oxide + chromic oxide as
promoter
Synthesis of methanol Zinc oxide + chromic oxide as promoter
Hydrogenation of vegetable oils Nickel
Bergius process for synthesis of petrol Ferrix oxide
Manufacture of ethyl alcohol from molasses Yeast (invertase and zymase)
61. In general acid catalysis all species capable of donating
protons contribute to reaction rate acceleration.[5] The
strongest acids are most effective. Reactions in which
proton transfer is rate-determining exhibit general acid
catalysis,
In specific acid catalysis, protonated solvent is the catalyst.
The reaction rate is proportional to the concentration of
the protonated solvent molecules SH+.[4] The acid catalyst
itself (AH) only contributes to the rate acceleration by
shifting the chemical equilibrium between solvent S and
AH in favor of the SH+ species. This kind of catalysis is
common for strong acids in polar solvents, such as water.
When reactions are conducted in nonpolar media, this kind
of catalysis is important because the acid is often not
ionized.
62. 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.
Desorption (STEP 4)
There is a re-arrangement of electrons and the
products are then released from the active sites
63.
64.
65. Pollution control(air
and waste streams;
stationary and mobile)
Clean oxidation/
halogenationprocesses
using O2,H2O2(C2H4O,
C3H6O)
Avoiding toxic
chemicals in industry
( HF,COCl2 etc.)
Fuel cells( H2
generation)
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66. One common application
for catalysts is for
catalyticconverters.
Catalytic converters are
found inautomobiles.
Their role is to reduceto
emissions of harmful
gases (CO, VOC’s, NOx)
that are the result of the
combustion of fuel in
vehicleengines.
ysis-ed.org.uk
67. There is catalyticrole
of chlorine free
radicals in
the breakdown of
ozone. Theseradicals
are formed by the
action
of ultraviolet
radiationon
chlorof luorocarbons
(CFCs).
www.okiu.ac.jp
70. Many fine chemicals
are prepared via
catalysis; methods
include those of
heavy industry aswell
as more
specialized processes
that would be
prohibitively
expensive on a large
scale.
www.essentialchemicalindustry.org
72. Thereaction that depends upon the pore
structure of the catalyst & the size of the
reactant & product molecules is called shape-
selective catalysis.
Zeolites is used as catalysts in
petrochemical industries for cracking of
hydrocarbons and
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isomerisation.
An important zeolite catalyst used
in the petroleum industry isZSM-5.
It converts alcohols directlyinto
gasoline (petrol) by dehydrating
them to give a mixture of
hydrocarbons.
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73. Petroleum refining makes intensive use of catalysisfor
alkylation , catalytic cracking (breakinglong-chain
hydrocarbons into smaller pieces) , naphthareforming
and steam reforming (conversion
of hydrocarbons into synthesisgas).
Fuel cellsdepend on catalysts for both theanodicand
cathodicreactions.
Catalytic heatersgenerate flameless heat from a supply
fuel
