1.
Chemical processes
Unit operation and Unit processes
Week-1
1st IME

2.
Chemical Processes
• Interrelated elementary processes
– Transfer of reactants to the reaction zone
– Chemical reactions involving various unit processes
– Separation of products from reaction zone via
various unit operation

3.
Chemical Processes cont…..
Homogeneous Chemical Processes:
Reactants in same phase (solid/liquid/gas)
Heterogeneous Chemical Processes:
Reactants in two or more phases
(gas-liq, gas-sol, gas-gas, liq-liq, liq-sol etc)

4.
Chemical Processes
• Reversible and irreversible
• Products cannot revert back to reactants
• Products react with other products to give reactants
• Endothermic and Exothermic
• Heat absorbed (surrounding temp decrease and system
temp increase)
• Heat released (surrounding temp increase and system
temp decrease)

5.
Chemical Processes
• Catalytic and non catalytic
• Rate of reaction affected by catalyst
• Rate of reaction unaffected by catalyst
• Isothermal or Adiabatic
• Temperature constant
• No heat and mass transfer

6.
Chemical Processes
• Other variables affecting Chemical processes:
– Temperature
– Pressure
– Composition
– Catalyst activity, selectivity, stability and life
– Rate of heat and mass transfer

7.
Chemical Processes
• Batch process
• Semi-batch process
• Continuous process

8.
Chemical Processes
• Material and energy balance, raw material and
energy consumption, energy changes
• 􏰀 Batch vs Continuous, process flow diagram
• 􏰀 Chemical process selection: design and
operation, pilot plant data, Equipment required,
material of construction
• 􏰀 Chemical Process Control and
Instrumentation

9.
Chemical Processes
• Chemical Process Economics: Competing
processes, Material and, Energy cost, Labour,
• Overall Cost of production
• 􏰀 Market evaluation: Purity of product and
uniformity of product for further processing

10.
Chemical Processes
• Plant Location
• 􏰀 Environment, Health, Safety and Hazard
• 􏰀 Construction, Erection and Commissioning
• 􏰀 Management for Productivity and creativity
􏰀
• Research, Development and patent
• 􏰀 Process Intensification

11.
Unit Operations
• Physical separation of the products obtained
during various processes.
• Classification in 1910 by W. H. Walkers and A.
D. Little

12.
Unit Operations
Unit Operations in Chemical Process Industries
• Absorption and stripping
• Membrane Process: Reverse osmosis, Electrodialysis,
Adsorption and desorption, Chromatography
• Crushing Grinding and Screening
• Distillation: Batch distillation Flash distillation, Azeotropic
distillation, Extractive distillation Reactive distillation
• Solid liquid extraction
• Evaporation
• Fluidisation
• Sublimation
• Crystallisation
• Solvent extraction
• Liquid- Liquid extraction

13.
Unit Operations
• DISTILLATION
• Distillation has been the king of all the separation processes
and most widely used separation technology.
• Distillation is used in petroleum refining and petrochemical
manufacture.

14.
Unit Operations
• MEMBRANE PROCESSES
one of the major separation processes during the recent
years.
used in desalination, wastewater treatment and gas
separation and product purification.
Membrane process classified based on driving force.

15.
Unit Operations
Driving force
Reverse osmosis Pressure difference
Ultrafiltration Pressure difference
Micro and Nano filtration Pressure difference
Gas permeation Concentration difference
Electrodialysis Electrical potential
Thermo-osmosis Temperature difference

16.
Unit Operations
• Absorption
Separation technique for gas cleaning

17.
Unit Operations
• Adsorption
separation and purification of gas and liquid
mixture

18.
Unit Processes
• Unit process involves principle chemical
conversions leading to synthesis of various
useful product.
• Provide basic information regarding the
reaction temperature and pressure, extent of
chemical conversions and yield of product of
reaction, nature of reaction (endothermic or
exothermic), type of catalyst used.

19.
Unit Processes
NITRATION
Introduction of one/more nitro groups into reacting
molecules
various nitrating agents like:
fuming nitric acid
concentrated nitric acid
aqueous nitric acid
mixture of nitric acid and sulphuric acid
Batch or continuous process.

20.
Unit Processes
Applicable in chemical industry as:
solvent
dyestuff
pharmaceuticals
explosive
chemical intermediates
Typical products:
TNT
Nitrobenzene
Nitronaphthalene
Nitroparaffins

21.
Unit Processes
Preparation of TNT (trinitrotoluene)
A three-step process:
1. Toluene is nitrated with a mixture of sulfuric acid and
nitric acid to produce mono-nitrotoluene or MNT.
2. MNT is separated and then renitrated to dinitrotoluene
or DNT.
3. DNT is nitrated to trinitrotoluene or TNT using an
anhydrous mixture of nitric acid and oleum.

22.
Unit Processes
HALOGENATION
Introduction of one/more halogen groups into a organic
compound
making various chlorine, bromine, iodine, fluorine organic
derivatives
Various chlorinating agents are:
chlorine, HCl, phosgene sulfuric chloride,
hypochlorite,
Various brominating agents are:
bromine, hydrobromic acid, bromide, bromated,
alkaline hypobromites.
Various iodinating agents are:
iodine, hydroiodic acid and alkali hypoiodites

23.
Unit Processes
Examples
Ethylene dichloride Chlorinated methanes
Chloroform Carbon tetra chloride
Chloro propane Chloro butanes,
chloroparaffins Alkyl halhides,
Chlorobenzene Ethylene diiodide,
Chloroflurocarbon (CFCs)

24.
Unit Processes
Preparation of chloroform and
chloroflurocarbon (CFCs)

25.
Unit Processes
SULPHONATION AND SULPHATION
Sulphonation: Introduction of sulphonic acid group or
corresponding salt like sulphonyl halide into a
organic compound
Sulphation: Introduction of -OSO2OH or -SO4-.
Sulphonating agents: sulphur trioxide and compounds,
sulphurdixide, sulphoalkylating agents
Sulphaming agents are sulphamic acid

26.
Unit Processes
Preparation of Saccharin
Reaction of hydrogen chloride with a solution of sulfur
trioxide in sulfuric acid.
Sulfonation by chlorosulfonic acid gives the ortho and para
substituted chlorosulfones.
The ortho isomer is separated and converted to the
sulfonamide with ammonia.
Oxidation of the methyl substituent gives the carboxylic acid,
which cyclicizes to give saccharin.
• HCl + SO3 → ClSO3H

27.
Unit Processes
Applications:
Production of lingo sulphonates
linear alkyl benzene sulphonate
Toluene sulphonates
Phenolic sulphonates
Chlorosulphonic acid
Sulphamates for production of herbicide, sweetening agent
(sidiumcyclohexysulphamate)
Oil soluble sulphonate
saccharin

28.
Unit Processes
OXIDATION
Oxidation using oxygen:
1. oxidation via dehydrogenation using oxygen,
2. dehydrogenation and the introduction of
oxygen and destruction of carbon
3. partial oxidation
4. peroxidation
5. oxidation in presence of strong oxidizing
agent like KMnO4, chlorate, dichromate,
peroxides H2O2, PbO2, MnO2; nitric acid
and nitrogen tertra oxide, oleum, ozone

29.
Unit Processes
Product of oxidation:
Aldehyde Ketone
Benzyl alcohol Phthalic anhydride Ethylene
oxide Vanillin
Benzaldehyde Acetic acid
Cumene Propylene oxide
Benzoic acid Maleic acid
Oxidation maybe carried out either in liquid
phase or vapour phase.

30.
Unit Processes
Preparation of synthetic gas from hydrocarbon
Fischer–Tropsch process, or Fischer–Tropsch synthesis (a
collection of chemical reactions that converts a mixture of
carbon monoxide and hydrogen into liquid hydrocarbons)
H2O + CH4 CO + 3 H2
H2O + CO H2O + CO
synthetic gas

31.
Unit Processes
HYDROGENATION
The reaction of a substance with hydrogen in the presence of
a catalyst.
Other reaction involving hydrogen are,
hydrodesulphurisation
hydrcracking
hydro formylation
oxosynthesis
hydroammonylsis
synthesis of ammonia.

32.
Unit Processes
Preparation of aldehyde (Hydro-formylation):
H2 + CO + CH3 CH=CH2 HCo(CO)PBu3
CH3 CH2 CH2 CHO

33.
Unit Processes
ESTERIFICATION
Esterification is an important unit process in the
manufacture of:
polyethylene terephathalate
methyl metha acrylate
cellulose ester in viscose rayon manufacture (xanthation of
alkali cellulose with carbon disulphide)
Nitroglycerine

34.
Unit Processes
HYDROLYSIS
Used both in inorganic and organic chemical industry:
oil and fats industry during soap manufacture (hydrolysis of fats
are carried out to obtain fatty acid and glycerol followed by
addition of sodium hydroxide to form soap)
Manufacture of amyl alcohols. Some of the major product using
hydrogen is ethylene from acetylene, methanol, propanol,
butanol, production of alcohol from olefins (eg. Ethanol from
ethylene).
Pure hydrolysis, hydrolysis with aqueous acid or alkali, dilute or
concentrated, alkali fusion, hydrolysis with enzyme and catalyst.

35.
Unit Processes
Preparation of ethanol from ethylene:
CH2 = CH2(g) + H2O(g) catalyst CH3CH2OH(g)
H = - 45 kJ mol -1

36.
Unit Processes
ALKYLATION
Introduction of an alkyl radical into an organic
compound by substitution or reduction
Applications:
detergent, lubricants, high octane gasoline,
photographic chemicals, plasticizers,
synthetic rubber, chemicals etc.
Alkylating agents: olefins, alcohols, alkyl halides.

37.
Unit Processes
Catalysts: sulphuric acid and phosphoric acid
however due to the corrosive nature of these acid now
solid acid catalyst is finding wide application in new
alkylation processes.
Preparation of toluene
Alkylation is the transfer of an alkyl group from one
molecule to another.
Benzene CH3Cl Toluene
AlCl3 catalyst, reflux
anhydrous conditions

38.
Unit Processes
POLYMERIZATION
Applicable in manufacture of:
polymer
synthetic fibre
synthetic rubber
polyurethane
paint and petroleum industry for high octane gasoline.
Single monomer or with comonomer
Addition or condensation reaction
Bulk/ emulsion/solution/ suspension.

39.
Unit Processes
Important product:
Polyethyelene PVC
Poly styrene Nylon
Polyester Acryicfibre
Poly butadiene Poly styrene
Phenylic Urea
Melamine Alkyd resins
Epoxy resin Silicon polymers
Poly vinyl alcohol

40.
Unit Processes
Preparation of Polyethylene or polythene
Most common plastic:
n CH2 = CH2 -(CH2-CH2 )- n