Important process reactions of industrial importance

Important process reactions

1. Department of Chemistry , MIT, Manipal
by
DR. SANTOSH L GAONKAR
PROFESSOR, DEPARTMENT OF CHEMISTRY,
MANIPAL INSTITUTE OF TECHNOLOGY
MANIPAL ACADEMY OF HIGHER EDUCATION , MANIPAL
Process Reactions
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2. 2Department of Chemistry , MIT, Manipal
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Important Process reactions:
Introduction,
Nitration: Nitrating agents, Aromatic nitration, kinetics and
mechanism of aromatic nitration, process equipment for technical
nitration, mixed acid for nitration.
Halogenation: Kinetics of halogenation, types of halogenations,
catalytic halogenations. Case studies on some industrial processes
Oxidation: Introduction, types of oxidative reactions, Liquid phase
oxidation with oxidizing agents. Nonmetallic Oxidizing agents such as
H
2O
2, sodium hypochlorite, Oxygen gas, ozonolysis.
Reduction: Catalytic hydrogenation, Heterogeneous and
homogeneous catalyst; Hydrogen transfer reactions, Metal hydrides.
Case study on industrial reduction process.

3. 2Department of Chemistry , MIT, Manipal 2
Nitration
•Introduction ofone or more nitro groups (-NO2 ) into a
reacting molecule.
• The reaction between a nitration agent and an organic
compound that results in one or more nitro ( -NO2) groups
becoming chemically bonded to an atom in this compound.
• A process in which a nitro group (-NO2) becomes chemically
attached to a carbon, oxygen, or nitrogen atom in an organic
compound.
• A hydrogen or halogen atom is often replaced by the nitro
group.
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4. 2Department of Chemistry , MIT, Manipal
Three general reactionssummarize nitration chemistry

1.Nitro aromatic or Nitro paraffinic compound: C nitration, in which
the nitro group attaches to a carbon atom
2.Nitrate ester: O nitration (an esterification reaction), in which an
ON bond is formed to produce a nitrate
3. Nitramine: N nitration, in which a NN bond is formed
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C-nitration
•This is the most common type of nitration, particularly
with aromatic compounds.
• It typically involves replacing a hydrogen atom on a
carbon with a nitro group.
• The mechanism generally involves electrophilic
aromatic substitution where the nitronium ionacts as
the electrophile, attacking the electron-rich aromatic
ring
• Common nitrating agents include a mixture of nitric
acid and sulfuric acid. Sulfuric acid generates the
nitronium ion by protonating nitric acid
• An example is the nitration of benzene to produce
nitrobenzene

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O-nitration
•This type of nitration involves the formation of nitrate esters,
where the nitro group attaches to an oxygen atom which is
bonded to a carbon atom.
•Nitroglycerin, an explosive, is a common example of a nitrate
ester formed through O-nitration of glycerol.
•The formation of nitrate esters involves the reaction of nitric
acid with an alcohol.

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N-nitration
•N-nitration involves attaching a nitro group to a
nitrogen atom within an organic molecule.
•An example is the nitration of amines or similar
nitrogen-containing compounds.
•Nitroguanidine, used in explosives, is formed through
N-nitration of guanidine

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Importance of Nitration products:
•Solvents
• Dyestuffs
• Pharmaceuticals
• Explosives
• They also serve as useful intermediates for the preparation
of other compounds, particularly amines which are
prepared by the reduction of the corresponding nitro
compound.
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Nitrating agents:
•Fuming, concentrated,and aqueous nitric acid
•Mixtures of nitric acid with sulfuric acid, acetic acid,
acetic anhydride, phosphoric acid, and chloroform.
•Nitrogen pentoxide , N2O5
• Nitrogen tetroxide, N2O4
NOTE : In order to make an intelligent choice of nitrating system for
particular nitration, it is desirable to know what species are present
in the various systems and to understand the mechanism of the
reaction under consideration.
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Mixed acid for nitration

•Mixed acid:
• The mixture of nitric acid-sulfuric acid is the most important
nitrating medium from a practical standpoint.
• Nitric acid exists in strong sulfuric acid as the nitronium ion,
NO2 +
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Mechanism of Nitration
Formation of nironiumion
Electrophilic substitution
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Aromatic nitration:
• Nitronium ion is an electrophilic reactant.
• Carbon atom of aromatic ring contains strong electron density.
• Nitro group can attach to ortho, meta or para positions depending
upon the electron density.
• The amount of these isomeric product will depend upon the
substituent.
• Certain substituent cause the electron density to be greater at
ortho and para position than meta position, hence they yield
nitration products in which ortho, and para isomers predominate.
• Other substituent cause the electron density to be greater at meta
position rather than ortho and para, hence they are called meta
directing.
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Kinetics of AromaticNitration
• The kinetics of aromatic nitration are functions of temperature,
which affects the kinetic rate constant, and of the compositions
of both the acid and hydrocarbon phases.
• In addition, a larger interfacial area between the two phases
increases the rates of nitration since the main reactions occur at
or near the interface.
• Larger interfacial areas are obtained by increased agitation.
• The viscosities and densities of the two phases and the interfacial
tension between the phases are important physical properties
affecting the interfacial area.
• Such properties are, of course, dependent on both temperature
and the respective compositions of the phases.
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• Temperature alsochanges the solubilities of various compounds in
either the acid or hydrocarbon phase. Such dissolved compounds
often result in by-product formation.
• Rates of nitration determined over a range of temperatures in two-
phase dispersions have been used to calculate energies of
activation from 59-75 kJ/mol (14-18 kcal/mol).
• Such energies of activation must be considered as only apparent,
since the true kinetic rate constants, NO2+ concentrations, and
interfacial area all change as temperature is increased.
• Increased agitation of a given acid-hydrocarbon dispersion results
in an increase in interfacial areas owing to a decrease in the average
diameter of the dispersed droplets. •
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Process Equipment's ForTechnical Nitration
• Batch Nitration
• Continuous Nitration
Batch Nitration:
• Nitrationis usually done in closed cast iron or steel vessels. Modern
practice is to use mild carbon steel.
• Nitrator consists of a cylindrical vessel containing some kind of
cooling surface, a means of agitation, feed inlets and product
outlet lines.
• They are also equipped with a large diameter quick dumping line
for emergency use if the reaction gets out of control.
• The contents of the nitrator are dumped rapidly into a large
volume of water contained in a drowning tub.
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18. 2Department of Chemistry , MIT, Manipal 2
• A commonaccessory for the nitrator is a suction line in the vapor
space above the liquid charge to remove the acid fumes and
oxides of nitrogen which may be liberated.
• Two factors which are of prime importance in the design of
nitrators are:
• Degree of agitations
• Control of temperature
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Continuous Nitration:
• Theactual nitration reactions in a continuous process are carried
out in the same type of vessel as used for batch nitration, with the
exception that an overflow pipe or weir arrangement is provided for
the continuous withdrawal of product and that continuous feed of
reactants is provided.
• Atomization is there in continuous processes.
Agitating mechanism can be Single impeller , Double impeller ,
Propeller or turbine with cooling sleeve .
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Advantages And Disadvantagesof Batch And Continuous Reaction
Processes.
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Advantages And Disadvantagesof Batch And Continuous Reaction Processes.
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HALOGENATION
•Introduction
•Types of Halogenation
•Kinetics of Halogenation
•Catalytic Halogenation
CONTENT
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Halogenationis defined as the process in which
•one or more halogen atoms are introduced in into an organic
compound
•Halogen atom include F, Cl, Br and I
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TYPES OF HALOGENATION
•Free radical halogenation
• Addition of halogen to alkenes and alkynes
• Halogenation of aromatic compounds
• Other Halogenation method
a) Fluorination
b) Chlorination
c) Bromination
d) Iodination
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Free radical halogenation
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Addition of halogen to alkenes
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Addition of halogen to alkynes
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Kinetics-
1) Hea t of rea ctions
Kinetics-
1) Heat of reactions
2) Energy of activation
3) Progress of reaction
4) Rates of reaction fig:
30
Relative reactivates of halogen towards methane.

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Manufacturing process for Dichloroethane

43. 43
Manufacturing process for Dichloroethane
Direct chlorination is performed in the liquid phase
where liquid chlorine and pure ethylene are reacted in
the presence of ferric chloride. The reaction can be
carried out at either low (20-70°C) or high (100-150°C)
temperatures.
The low temperature process has the advantage of low
by-product formation but requires more energy to
recover the EDC. The high temperature process utilises
the heat of reaction in the distillation of the EDC ,
leading to considerable energy savings.

44. 44
Manufacturing process for Dichloroethane
In the oxychlorination process, pure ethylene and hydrogen chloride, mixed
with oxygen, are reacted at 200-300°C and 4-6 bar in the presence of a
catalyst, usually cupric chloride. The reaction takes place in either a fixed
bed or fluid bed reactor, the latter being preferred as it is easier to control
the temperature.
Some recent development in the choice of the catalyst have been reported
to produce EDC of high quality which eliminates the need for distillation.

45. 45
Manufacturing process for Dichloroethane
•Direct
Chlorination:
C
2H
4+ Cl
2→ C
2H
4Cl
2 ΔH
R,0= −220 kJ/mol
• Oxychlorination:
C
2H
4+ ½ O
2+ 2 HCl → C
2H
4Cl
2+
H
2O
ΔH
R,0= −320 kJ/mol
• Cracking: C
2H
4Cl
2→ C
2H
3Cl + HCl ΔH
R,0= + 97 kJ/mol
• Overall Reaction:
2 C
2H
4+ Cl
2+ ½ O
2→ 2 C
2H
3Cl +
H
2O

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1. Chlorination (common in industry)
•Reaction:
�
6�
6+�??????
2
????????????��
3/����
3
�
6�
5�??????+��??????
•Catalyst: Ferric chloride (FeCl₃), aluminum chloride (AlCl₃), or iron filings.
•Conditions:
•Temperature: 20–80 °C (controlled to avoid poly-chlorination).
•Pressure: Often atmospheric.
•Solvent: Sometimes CCl₄ or CH₂Cl₂, but in bulk industry often solvent-
free.
2. Bromination
•Reaction:
�
6�
6+�??????
2
????????????��3/����3
�
6�
5�??????+��??????
•Catalyst: FeBr₃ or AlBr₃.
•Conditions:
•Temperature: Mild (room temperature).
•Often more selective than chlorination.

48. 48
3. Iodination
•Reaction:
�
6�
6+�
2
??????��3
�
6�
5�+��
•Catalyst/Oxidant: Nitric acid or Cu salts (oxidizes HI to
regenerate I₂).
•Conditions: Higher energy input; less common industrially.
4. Fluorination (special case)
•Reaction: Direct reaction is highly vigorous and unsafe.
•Industrial method: Uses SbF₅/HF (Halex process) or
electrophilic fluorinating agents .
•Conditions: Strictly controlled (low temperature, specialized
reactors).

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50. OxidationReactions
Oxidation: Introduction, types of oxidative reactions,
Liquid phase oxidation with oxidizing agents.
Nonmetallic Oxidizing agents such as H2O2, sodium
hypochlorite, Oxygen gas, ozonolysis.

51. Introduction to Oxidation
•Oxidation is one of the most fundamental and widely
applied classes of reactions in organic and industrial
chemistry.
•Broadly, oxidation involves the increase in oxidation state,
often through the addition of oxygen, removal of hydrogen,
or loss of electrons.
• Oxidation reactions are important in the synthesis of fine
chemicals, intermediates, polymers, and pharmaceuticals,
as well as large-scale industrial processes.

52. Types of Oxidative Reactions
1.Hydroxylation – Introduction of hydroxyl groups into hydrocarbons
or aromatic rings.
2.Dehydrogenation – Removal of hydrogen from organic substrates
(e.g., alcohol → carbonyl, alkane → alkene).
3.Oxidative cleavage – Breaking of C–C double bonds or other
linkages, forming smaller oxygenated fragments (e.g., ozonolysis).
4.Aromatic oxidation – Conversion of alkyl side chains or rings to
carboxylic acids or quinones.
5.Selective oxidation – Transformation of functional groups under
mild and controlled conditions, important in pharmaceuticals.

53. 1. Hydroxylation Reactions
•Introduction of hydroxyl (–OH) groups.
•Examples: Alkene → Glycol; Benzene → Phenol.
•Applications: Diols, polymers, pharmaceuticals.

54. Aromatic Hydroxylation – Cumene Process
Significance:
•World’s dominant industrial process for phenol (≈ 90% of production).
•Valuable co-product acetone used as solvent

56. 2. Dehydrogenation Reactions
•Removal of hydrogen atoms.
•Examples: Alcohol → Aldehyde/Ketone; Alkane → Alkene.
•Industrial use: Ethylbenzene → Styrene.

57. PCC (Pyridinium Chlorochromate)
Formula: C₅H₆N⁺·ClCrO₃⁻
PDC (Pyridinium Dichromate)
Formula:�_5�_5���??????
2�
7
mild oxidizing agent in organic synthesis.

58. Formaldehyde is a key raw material for resins (urea-formaldehyde,
phenol-formaldehyde), plastics, adhesives, and disinfectants.

59. Dehydrogenation Reactions
Direct dehydrogenation of ethylbenzene to styrene accounts for 85 %
of commercial production.
The reaction is carried out in the vapor phase with steam over a
catalyst consisting primarily of iron oxide.
The major reaction is the reversible, endothermic conversion of
ethylbenzene to styrene and hydrogen:

Competing thermal reactions degrade ethylbenzene to benzene, and
also to carbon:
Styrene also reacts catalytically to toluene:

60. 3. Oxidative Cleavage Reactions
Involve the breaking of C–C double or triple bonds (and
sometimes side chains) by oxidation, leading to the formation of
smaller oxygenated fragments such as aldehydes, ketones, or
carboxylic acids.
Examples:
•Ethene → 2 Formaldehyde
•Cyclohexene → Adipic dialdehyde

61. Oxidative Cleavage of Alkynes
•Alkynes undergo cleavage to yield carboxylic acids.
Oxidative Cleavage of Glycols (Glycol Cleavage)
•Vicinal diols (1,2-diols) can be cleaved by periodic acid (HIO₄) or lead tetraacetate
(Pb(OAc)₄).
•Gives two carbonyl compounds (aldehydes/ketones).

62. Aromatic Side-Chain Oxidation
•Oxidation of alkyl side chains on aromatic rings.
•Example: Toluene → Benzoic acid.
•Industrial use: Xylene → Terephthalic acid (polyester precursor).
Large-scale production of terephthalic acid (precursor of polyester).
~90% of global terephthalic acid is used for PET fibers, films, and bottles.

63. Oxidative Coupling
Two identical or different molecules are joined together (C–C or C–O
bond formation) through an oxidation process.

64. Oxidative Decarboxylation
•Removal of CO2 along with oxidation.
•Examples: Pyruvate → Acetyl-CoA; Kolbe reaction.
•Applications: Biochemistry, organic synthesis.
Kolbe Reaction

65. Selective Oxidations
controlled introduction of oxygen (or removal of
hydrogen/electrons) into a specific functional group of a molecule
without affecting other sensitive groups present in the same
substrate.

66. Industrial Selective Oxidations
•Cyclohexane → Adipic acid (for nylon).
•p-Xylene → Terephthalic acid (for PET).
•Ethylene → Ethylene oxide (antifreeze, polymers).

67. Liquid Phase Oxidation with Oxidizing Agents
oxidation reactions that are carried out in the liquid phase, typically using organic
substrates dissolved in solvents (aqueous or organic) and oxidizing agents.
Important industrial and laboratory process for producing aldehydes, ketones,
carboxylic acids, alcohols, and peroxides.
Common Oxidizing Agents Used in Liquid Phase Oxidation
Oxygen / Air
•Industrially the cheapest oxidant.
•Requires catalysts (Co, Mn, Ce, Cu salts; metal acetates, or noble metals like Pt, Pd).
•Examples:
•p-Xylene → Terephthalic acid (PTA production).
•Cyclohexane → Adipic acid (nylon precursor).
Hydrogen Peroxide (H₂O₂)
•Environmentally friendly ("green oxidant," produces only water as byproduct).
•Used with transition metal catalysts (Ti, Mo, W, Fe, V).
•Examples:
•Epoxidation of alkenes.
•Baeyer–Villiger oxidation (ketones → esters).

68. Organic Peroxides / Hydroperoxides (e.g., t-BuOOH, cumene
hydroperoxide)
•Widely used in selective oxidations.
•Example:
•Cumene → Cumene hydroperoxide → Phenol + Acetone.
Nitric Acid (HNO₃)
•Strong oxidizer, used in large-scale oxidations.
•Examples:
•Cyclohexanol/Cyclohexanone → Adipic acid.
•o-Xylene → Phthalic acid.

69. Permanganate (KMnO₄)
•Powerful oxidant in acidic, neutral, or alkaline medium.
•Laboratory oxidations of alkenes (→ glycols, carboxylic acids).
Chromic Acid / PCC / PDC (Cr(VI) reagents)
•Selective oxidations of alcohols to aldehydes/ketones.
•Limited industrial use due to toxicity and waste problems.
Other Agents
•Sodium hypochlorite (NaOCl): bleaching, alcohol oxidation.
•Periodates, peracids (m-CPBA): selective epoxidation,
Baeyer–Villiger.
•Fenton’s Reagent (H₂O₂ + Fe²⁺): hydroxylation, degradation
reactions.

70. Industrial Examples
•Terephthalic acid production:
p-Xylene + O₂ (Co/Mn/Br catalyst, acetic acid solvent) →
Terephthalic acid.
•Adipic acid production:
Cyclohexane + O₂ (with Co/Mn catalysts, sometimes via nitric acid)
→ Adipic acid.
•Phenol–Acetone process:
Cumene + O₂ → Cumene hydroperoxide → Phenol + Acetone.
•Propylene epoxidation:
Propylene + H₂O₂ (TS-1 zeolite catalyst) → Propylene oxide.

71. Ozonolysis
is an oxidation reaction where ozone (O₃) cleaves carbon–
carbon double bonds (C=C) or triple bonds (C≡C) in
alkenes or alkynes, leading to the formation of smaller
oxygenated compounds.
Used in the industrial synthesis of aldehydes, ketones, and
carboxylic acids.

72. Industrial Uses:
•Oxidative cleavage of olefins for synthesis of aldehydes, ketones,
acids.
•Production of adipic acid (nylon precursor) from cyclohexene.
•Degradation of unsaturated fatty acids and natural products.

73. In industry, toluene is oxidized with air or oxygen in the liquid phase,
catalyzed by Co/Mn salts (often with bromide promoters), at 150–
200 °C and 5–10 atm, via a radical chain mechanism. The main
product is benzoic acid, widely used in food preservatives,
plasticizers, and as an intermediate for caprolactam and phenol
production.
Industrial liquid-phase oxidation of toluene to benzoic acid.
Process
•Medium: Liquid phase, generally using acetic acid or toluene itself
as solvent.
•Catalysts: Cobalt and manganese salts (e.g., cobalt naphthenate,
manganese acetate) are commonly used. Sometimes bromide ions
(Co–Mn–Br system) are added as promoters.
•Oxidant: Molecular oxygen (air or pure O₂).
•Conditions:
•Temperature: 150–200 °C
•Pressure: 5–10 atm (to maintain oxygen in solution)

74. Sodium hypochlorite (NaOCl) is an inorganic compound
commonly used as a disinfectant, bleaching agent, and
oxidizing agent.
Physical Properties
•Formula: NaOCl
•Appearance: Pale greenish-yellow solution (usually 5–15% w/v in
water).
•Odor: Strong chlorine-like smell.
Preparation
•Industrial method (Hooker process):
�??????
2+2�??????��⟶�??????�??????+�??????��??????+�
2�
Oxidizing Agent: Oxidizes many organic and inorganic compounds.
Example:
�??????��??????+�
2�⟶���??????+�??????��

75. •Bleaching: Destroys colored organic compounds (chromophores).
•Disinfection: Kills bacteria, viruses, fungi by oxidizing cell
components.
•Disproportionation: On heating or in acidic medium, it decomposes.
3�??????��??????⟶2�??????�??????+�??????�??????�
3

76. Haloform Reaction
NaOCl can oxidize methyl ketones (or secondary alcohols with –
COCH₃ group) to haloforms (e.g., CHCl₃).
Example:
��
3����
3
�����
���??????
3+��
3����??????
Way to make a nitrile oxide (R–C≡N⁺–O⁻) from an oxime using sodium
hypochlorite

77. Hydrogen Transfer Reactions (Transfer Hydrogenation)
•No H₂ gas; hydrogen is transferred from a donor
(isopropanol, formic acid, cyclohexene).
•Catalysts: transition metal complexes (e.g., Ru, Ir with chiral
ligands).
•More convenient & safer than direct H₂.
Example:
�ℎ����
3+
(��
3)
2
����
????????????��2??????−�??????�??????�??????]
2
���??????
�ℎ������
3

78. Metal Hydrides
•Hydride reagents deliver H⁻ directly.
Common reagents:
•LiAlH₄ (LAH): reduces esters, carboxylic acids, nitriles, amides,
ketones, aldehydes → alcohols.
•NaBH₄: milder, reduces aldehydes/ketones selectively (not esters or
acids).
•DIBAL-H: reduces esters, nitriles → aldehydes (at low temperature).
Examples:
•Acetone → Isopropanol (NaBH₄).
•Ethyl benzoate → Benzaldehyde (DIBAL-H).
•Ethyl benzoate → benzoic acid (LAH)

79. Hydrogenation of Vegetable Oils
•Process: Liquid vegetable oils (unsaturated triglycerides) are
hydrogenated with H₂ gas + Ni catalyst.
•Purpose: Convert liquid oils → semi-solid fats (margarine).
•Reaction:
??????��=��??????
′
+�
2՜
�??????
??????��
2��
2??????
′
•Conditions: 120–200 °C, 2–10 atm H₂.
•Challenge: Partial hydrogenation may form trans fats, which are
health hazards.
•Solution: Modern processes use improved catalysts for selective
hydrogenation (cis retention).

80. Oxo Process (Hydroformylation + Reduction)
•Converts alkenes into aldehydes, then hydrogenates them into
alcohols.
•Uses syngas mixture: CO + H₂.
•Catalyst: Transition metal carbonyls (Co, Rh).