Petrochemical

Petrochemicals are chemical products derived from petroleum. Some

chemical compounds made from petroleum are also obtained from
other fossil fuels such as coal or natural gas, or renewable sources such
as corn or sugar cane

petrochemical industries have revolutionized our life and are providing

the major basic needs of rapidly growing, expanding and highly
technical civilization as a source of energy for domestic, industrial,
transport sectors and as feedstock for fertilizers, synthetic fibers,
synthetic rubbers, polymers, intermediates, explosives, agrochemicals,
dyes, and paints etc.

Oil refining and steam cracking of naphtha and natural gas (ethane &
propane) are the common routes of producing petrochemicals

Petrochemical Socio-economic Linkage

Used in the production of plastics, fibers, lubricants, films,

textiles, pharmaceuticals, etc. ---even chewing gum!

STRUCTURE OF PETROCHEMICAL COMPLEXES

The manufacture of basic raw materials like syngas, methane, ethylene,
propylene, acetylene, butadiene, benzene, toluene, xylenes, etc.
The basic building processes include partial oxidation, steam reforming,
catalytic and thermal cracking, alkylation, dealkylation, hydrogenation,
disproportionation, isomerisation, etc.
The commonly used unit operations are distillation, extractive distillation,
azeotropic distillation, crystallisation, membrane separation, adsorption,
absorption, solvent extraction, etc.
Manufacture of intermediate chemicals derived from the above basic
chemicals by various unit processes like oxidation, hydrogenation,
chlorination, nitration, alkylation, dehydrogenation along with various unit
operations like distillation, absorption, extraction, adsorption, etc.
Manufacture of target chemicals and polymers that may be used in the
manufacture of target products and chemicals to meet the consumer needs.
It includes plastics, synthetic fibers, synthetic rubber, detergents, explosives,
dyes, intermediates, and pesticides

BASIC PETROCHEMICALS

C1 group Methane, CO H2 synthesis, synthesis gas derivatives

C2 group Ethane, ethylene, ethylene derivatives, acetylene

C3 group Propane, propylene and propylene derivatives

C4, C5 group Butadiene, Butanes, Butenes, Pentane, Pentene, Isoprene,

Cyclopentadiene

Aromatic Benzene, Toluene , Xylenes Naphthalene, BTX derivatives

MAJOR END PRODUCTS

Polymer, Synthetic fibre, synthetic rubber, synthetic detergent, Chemical

intermediate, dyes and intermediates chemical intermediates, pesticides

BASIC BUILDING BLOCK PROCESS

Cracking: Steam cracking, Catalytic cracking for olefins pyrolysis gasoline
by product
Steam reforming and Partial oxidation: Synthesis gas
Catalytic Reforming: Aromatic production
Aromatic conversion processes: Aromatic production
Alkylation: Linear alkyl benzene
OXO Process: Oxo-alcohol
Polymerisation Process: Polymer, elastomers and synthetic fibre

Alternative Routes to Principal Petrochemicals

SYNTHESIS GAS
Methane and synthesis gas are important petrochemical feedstock for the
manufacture of a large number of chemicals, which are used directly or as
intermediates, a number of which are finding use in plastic, synthetic fiber,
rubber, pharmaceutical and other industries. Synthesis gas is commonly
used to describe two basic gas mixtures - synthesis gas containing CO,
hydrogen and synthesis gas containing hydrogen and nitrogen for the
production of ammonia.
Petrochemical derivatives based on synthesis gas and carbon monoxide
have experienced steady growth due to large scale utilization of methanol
and development of a carbonylation process for acetic acid and Oxo
synthesis process for detergents, plasticizers, and alcohols.
Recent market studies show that there will be a dramatic increase in
demand of CO and syngas derivatives Methanol is the largest consumer of
synthesis gas.
The reformed gas is to meet certain requirements with regard to its
composition. It is characterized by the stoichiometric conversion factor,
which differs from case to case

Manufacture of Methanol from Synthesis Gas

Desired: CO + 2H2
CH3OH
- Side reactions: CO + 3H2 CH4 + H2O
2CO + 2H2 CH4 + CO2
- All above reactions are exothermic
-Undesired reaction: CO + H2 alchohols + hydrocarbons
-Catalyst: Mixed catalyst made of oxides of Zn, Cr, Mn, Al.
-H2 and CO adjusted to molar ratio of 2.25
-The mixture is compressed to 200 350 atms
-Recycle gas (Unreacted feed) is also mixed and sent to the compressor
-Then eventually the mixture is fed to a reactor. Steam is circulated in the
heating tubes to maintain a temperature of 300 375C
-After reaction, the exit gases are cooled
-After cooling, phase separation is allowed.

-In this phase separation operation methanol and other high molecular weight
compounds enter the liquid phase and unreacted feed is produced as the gas
phase.
The gas phase stream is purged to remove inert components and most of the
gas stream is sent as a recycle to the reactor.
-The liquid stream is further depressurized to about 14 atms to enter a second
phase separator that produces fuel gas as the gaseous product and the liquid
stream bereft of the fuel gas components is rich of the methanol component.
-The liquid stream then enters a mixer fed with KMNO4 so as to remove traces
of impurities such as ketones, aldehydes etc.
-Eventually, the liquid stream enters a distillation column that separates
dimethyl ether as a top product.
- The bottom product from the first distillation column enters a fractionator that
produces methanol, other high molecular weight alcohols and water as three
different products.

 Side reaction-high molecular wt hydrocarbons

The first two reactions are exothermic and proceed with reduction in
volume.
In order to achieve a maximum yield of methanol and a maximum
conversion of synthesis gas, the process must be effected at low temperature
and high pressure.
After cooling to ambient temperature, the synthesis gas is compressed to
5.0-10.0 MPa and is added to the synthesis loop which comprises of
following items circulator, converters, heat exchanger, heat recovery
exchanger, cooler, and separator
The catalyst used in methanol synthesis must be very selective towards the
methanol reaction, i.e. give a reaction rate for methanol production which is
faster than that of competing
Mixed catalyst is used-oxides of zinc, chromium or aluminum
Catalyst fouling- at high CO partial pressure

FORMALDEHYDE

Some major intermediates derived from formaldehyde are chelating

agents, acetal resins, 1,4- butanediol, polyols, methylene diisocynate.

It is also used for the manufacture of wide variety of chemicals,

including sealant, herbicides, fertilisers, coating, and pharmaceutical.

Formaldehyde is commercially available as aqueous solution with

concentration ranging from 30-56 wt.% HCHO. It is also sold in solid
form as paraformaldehyde or trioxane.

The production of formaldehyde in India has been growing at a fairly

constant rate during last ten years. There are presently about 17 units in
India.

The reactions are carried out in vapour phase.

Catalyst: Silver or zinc oxide catalysts on wire gauge are used.
Operating temperature and pressure: Near about atmospheric pressure and
500 600 C
Air is sent for pre-heating using reactor outlet product and heat integration
concept.
Eventually heated air and methanol are fed to a methanol evaporator unit
which enables the evaporation of methanol as well as mixing with air.
The reactor inlet temperature is 54 C.
The feed ratio is about 30 50 % for CH3OH: O2
After reaction, the product is a vapour mixture with temperature 450 900 C
After reaction, the product gas is cooled with the heat integration concept
and then eventually fed to the absorption tower.
The absorbent in the absorption tower is water as well as formaldehyde rich
water.

Since formaldehyde rich water is produced in the absorption, a portion of the rich
water absorbent solution from the absorber is partially recycled at a specific
section of the absorber.
From the absorber, HCHO + methanol rich water stream is obtained as the
bottom product.
The stream is sent to a light end stripper eventually to remove any light end
compounds that got absorbed in the stream.
The vapors from the light end unit consisting of light end compounds can be fed
at the absorption unit at specific location that matches with the composition of the
vapors in the absorption column.
Eventually, the light end stripper bottom product is fed to a distillation tower that
produces methanol vapour as the top product and the bottom formaldehyde +
water product (37 % formaldehyde concentration).

CHLOROMETHANES
(METHYL
CHLORIDE,
METHYLENE
DICHLORIDE, CHLOROFORM, CARBON TETRACHLORIDE)
Chlorinated methanes, which include methyl chloride, methylene dichloride,
chloroform and carbon tetrachloride, are important derivatives of methane and
find wide application as solvents and as intermediate products.

Process Technology
There are two major routes for the manufacture of chloromethane:
Direct chlorination of methane
Through methanol route
Direct Chlorination of Methane: Chlorination of methane (natural gas) is
carried out at around 400-450 C during which following reaction takes place

The reactions are very exothermic.

The feed molar ratio affects the product distribution. When CH4/Cl2 is about
1.8, then more CH3Cl is produced.
On the other hand, when CH4 is chosen as a limiting reactant, more of CCl4 is
produced.
Therefore, depending upon the product demand, the feed ratio is adjusted
Methane and Cl2 are mixed and sent to a furnace
The furnace has a jacket or shell and tube system to accommodate feed preheating to desired furnace inlet temperature (about 280 300C).
To control temperature, N2 is used as a diluent at times.
Depending on the product distribution desired, the CH4/Cl2 ratio is chosen.
The product gases enter an integrated heat exchanger that receives separated
CH4 (or a mixture of CH4 + N2) and gets cooled from the furnace exit
temperature (about 400 C).

Eventually, the mixture enters an absorber where water is used as an absorbent

and water absorbs the HCl to produce 32 % HCl.

The trace amounts of HCl in the vapor phase are removed in a neutralizer fed
with NaOH
The gas eventually is compressed and sent to a partial condenser followed with
a phase separator.
The phase separator produces two streams namely a liquid stream consisting of
the chlorides and the unreacted CH4/N2.
The gaseous product enters a dryer to remove H2O from the vapor stream
using 98% H2SO4 as the absorbent for water from the vapor.

The chloromethane enter a distillation sequence. The distillation sequence

consists of columns that sequentially separate CH3Cl, CH2Cl2, CHCl3 and
CCl4.

NAPHTHA STEAM CRACKING FOR PRODUCTION

Ethylene & Acetylene

-Hydrocarbons such as Naphtha and LPG have lighter compounds.

-When they are subjected to steam pyrolysis, then good number of
petrochemicals can be produced.
-These include primarily ethyelene and acetylene along with other
compounds such as propylene, butadiene, aromatics (benzene, toluene
and xylene) and heavy oil residues.
- The reaction is of paramount importance to India as India
petrochemical market is dominated by this single process.

NAPHTHA STEAM CRACKING FOR PRODUCTION

Ethylene & Acetylene

The principal process used to convert the relatively unreactive alkanes

into much more reactive alkenes is thermal cracking, often referred to as
steam cracking.
In steam cracking, a hydrocarbon stream is thermally cracked in the
presence of steam, yielding a complex product mixture.
The name steam cracking is slightly illogical: cracking of steam does not
occur, but steam primarily functions as a diluent and heat carrier,
allowing higher conversion.
A more accurate description of the process might be pyrolysis

 The steam cracker remains the fundamental unit and is the heart of any
petrochemical complex and mother plant and produces large number of
products and byproducts such as - ethylene, propylene, butadiene,
butane and butenes, isoprene, etc., and pyrolysis gasoline.
The choice of the feedstock for olefin production depends on the
availability of raw materials and the range of downstream products.
Naphtha has made up about 50-55percent of ethylene feedstock sources
since 1992.
Requirement of steam will depend upon the type of feedstock; the
lighter hydrocarbon requires less steam as compared to heavier
feedstock

Reaction

The reaction is pretty complex -10 to 12 compounds in one go

Almost all basic principles of separation appears to be accommodated

from a preliminary look.
Important separation tasks: Elimination of CO and CO2, Purification of all
products such as ethylene, acetylene etc.
Reaction temperature is about 700 800C (Vapor phase reaction).

Naphtha/LPG mixed with superheated steam and fed to a furnace

The C2-C4 are fed to a separate furnace fed with fuel gas + fuel oil as fuels to
generate heat.
After pyrolysis reaction, the products from the furnace are sent to another heat
recovery steam boiler to cool the product streams (quenching) (from about 700
800C) and generate steam from water.
After this operation, the product vapors enter a scrubber that is fed with gas oil as
absorbent. The gas oil removes solids and heavy hydrocarbons.
Separate set of waste heat recovery boiler and scrubbers are used for the LPG
furnace and Naphtha steam cracking furnaces
After scrubbing, both product gases from the scrubbers are mixed and fed to a
compressor. The compressor increases the system pressure to 35 atms.
The compressed vapour is fed to a phase separation that separates the feed into
two stream namely the vapour phase stream and liquid phase stream.
The vapour phase stream consists of H2, CO, CO2 C1-C3+ components in excess.

The liquid phase stream consists of C3 and C4 compounds in excess

Subsequently, the vapour phase and liquid phase streams are subjected to
separate processing.
Gas stream processing:
CO2 in the vapour phase stream is removed using NaOH scrubber.
Subsequently gas is dried to consist of only H2, CO, C1-C3 components
only.
This stream is then sent to a demethanizer which separates tail gas (CO +
H2 + CH4) from a mixture of C1-C3 components.
The C2-C3+ components enter a dethanizer which separates C2 from C3
components.
The C2 components then enter a C2 splitter which separates ethane from
ethylene and acetylene.

The ethylene and acetylene gas mixture is fed to absorption unit which is
fed with an extracting solvent (such as N-methylpyrrolidinone) to extract
Acetylene from a mixture of acetylene and ethylene.
The extractant then goes to a stripper that generates acetylene by stripping.
The ethylene stream is fed to a topping and tailing still to obtain high purity
ethylene and a mixture of ethylene and acetylene as the top and bottom
products.
Liquid stream processing
The liquid stream consists of C3,C4, aromatics and other heavy oil
components is fed to a NaOH scrubber to remove CO2
Eventually it is fed to a pre-fractionator. The pre-fractionator separates
lighter components from the heavy components.

The lighter components are mixed with the vapour phase stream and sent to
the NaOH vapour phase scrubber unit.
The pre-fractionator bottom product is mixed with the de ethanizer bottom
product Eventually the liquid mixture enters a debutanizer that separates C3,
C4 components from aromatics and fuel oil mixture.
The bottom product eventually enters a distillation tower that separates
aromatics and fuel oil as top and bottom products respectively.
The top product then enters a depropanizer that separates C3s from C4
components.
The C4 components then enter an extractive distillation unit that separates
butane + butylenes from butadiene.
The solvent stripper produces butadiene and pure solvent which is sent to the
distillation column.
The C3 components enter a C3 splitter that separates propylene from propane
+ butane mixture.

OPERATING VARIABLES OF STEAM CRACKING

Composition of Feed Stock

Naphtha are mixture of alkane, cycloalkanes, and aromatic hydrocarbons

depending on the type of oil from which the naphtha was derived.

A full range naphtha boiling range approximately 20 to 200C would contain

compound, with from 4-12 carbon atms.

The steam cracking of the naphtha yields wide variety of products, ranging
from hydrogen to highly aromatic heavy liquid fractions.

The thermal stability of hydrocarbons increases in the following order:

parafins, naphthenes, aromatics.

Yield of ethylene as well as that of propylene is higher if the naphtha feed

stock is rich in paraffins.

Pyrolysis temperature and Residence Time

As the furnace exit temperature rises, the yield also rises, while the yields of
propylene and pyrolysis gasoline (C5-200C at) decrease.

The highest ethylene are achieved by operating at high severely, namely,

around 850C with residence time ranging from 0.2 to 0.4s

However, operating at high temperature results in high coke formation

Partial Pressure of Hydrocarbon and Steam to Naphtha Ratio

Pyrolysis reaction producing light olefins are more advanced at lower
pressure.
Decrease into the partial pressure of hydrocarbons by dilution with steam,
reduces the overall rate reaction rate, but also help to enhance the selectivity
of pyrolysis substantially in favour of the light olefins desired.
Other role of steam during pyrolsis is
(1) to increase the temperature of feed stock
(2) reduction in the quantity of heat to be furnished per linear meter of tube in
the reaction section
(3) to remove partially coke deposits in furnace tubes.
The ethylene yield decreases as the partial pressure of hydrocarbon increases.

ETYLENE OXIDE (EO)

Ethylene oxide is one of the important petrochemical intermediate used for the
manufacture of large number of products; some of the major uses are in the
manufacture monoethylene glycol, glycol ethers which is made by reaction of
ethylene oxide and alcohols, ethanol amines.
Surfactant industry is one of largest user of EO, both for industrial and house hold
applications.

Ethylene and air are compressed separately, mixed together

Catalyst- Silver oxide on a porous carrier of alumina
Side reaction suppressing agent (ethylene dichoride) is added
Highly exothermic reaction- carried out at 250-300 C
Residence time-1s
Effluent gas washed with water
Absorbed ethylene dioxide sent to desorber-fractionator
Air ethylene ratio kept minimum below lower explosion limit
(3%)- Inert gas added
Two reactor in series are used for better conversion
Use of oxygen instead air results in high yield

The reactor is fed on the shell side with Dowtherm fluid that serves to maintain the
reaction temperature.
A dowtherm fluid is a heat transfer fluid , which is a mixture of two very stable
compounds, biphenyl and diphenyl oxide.
The fluid is dyed clear to light yellow to aid in leak detection.
-The hot dowtherm fluid from the reactor is sent to a waste heat recovery boiler to
generate steam
-The vapour stream is cooled using a integrated heat exchanger using the unreacted
vapour stream generated from an absorber.
-The vapour stream is then sent to the heat integrated exchanger and is then sent
back to the reactor and a fraction of that is purged to eliminate the accumulation of
inerts such as Nitrogen and Argon.
The product vapors are compressed and sent to a water absorber which absorbs
ethylene oxide from the feed vapors.

Eventually, the ethylene oxide rich water stream is sent to a stripper which
desorbs the ethylene oxide + water as vapour and generates the regenerated
water as bottom product.
The regenerated water reaches the absorber through a heat integrated
exchanger.
-The ethylene oxide + water vapour mixture is compressed (to about 4 - 5
atms) and then sent to a stripper to generate light ends + H2O as a top product
and the bottom product is then sent to another fractionators to produce
ethylene oxide as top product.
-The heavy ends are obtained as bottom product

Ethanolamines
Ethanolamines use- Manufracture of detergent,
components from gases, intermediate chemical

to remove acidic

Ethylene Oxide + Ammonia to Monoethanolamine

-Monoethanolamine + Ammonia to Diethanolamine
-DIethanolamine + Ammonia to Triethanolamine
-The above reactions are series reaction scheme
-Reaction is exothermic
-Ammonia is in aqueous phase and ethylene oxide is in vapour state.
-Therefore, the reaction will be gas-liquid reaction

-Ammonia is mixed with ammonia recycle stream from the process and

pumped to the CSTR where liquid phase ammonolysis takes place.

-Ethylene oxide is compressed and fed to the CSTR.
-The CSTR operating pressure will be such that the feed (and product)
mixtures do not vaporize and good liquid phase reaction can occur.
-The reactor is cooled using water in the cooling jacket as the reactions are
mildly exothermic
-The product stream is then sent to a flash unit that separates NH3 + H2O as a
vapour stream and water + ethanolamines as a liquid stream.
- The ammonia + water stream is recycled to mix with the fresh ammonia and
enter the reactor.

-The bottom product from ammonia flash unit is sent to a water separation
tower that again removes dissolved ammonia in the ethanolamine rich solution
-Once again ammonia + water are generated and this stream is also recycled to
mix with fresh ammonia feed.
-The bottom product consisting of crude mixture of ethanolamines and heavy
ends.
-This mixture is fed to a monoethanolamine tower first to separate the
monoethanol amine from the other two and heavy ends
-The bottom product from the first distillation tower then enters the second and
third distillation towers which are operated under vacuum to produce
diethanolamine and triethanolamine as top products.
-The bottom product from the last distillation tower is the heavy ends product

The diethanol and triethanolamines dissociate at high operating

temperatures.
Therefore, vacuum is used to reduce the operating temperature of the
distillation columns (second and third).
Also solvents tend to have similar solubility factors for both di and
triethanolamines. Hence solvent extraction is not possible
When higher quantitites of di or triethanolamine is desired, then the
monoethanolamine can be sent to another reactor in which ethylene oxide
is added.
Its not advisable to recycle it the CSTR shown in the process flow sheet
as it can form amino-ethers but not diethanolamine

MONO-, DI- TRI- ETHYLENE GLYCOLS

A major petrochemicals and find application in manufacture of polyester and
as antifreeze accounts for 70% of Ethylene oxide production.
Ethylene oxide preheated to 195C. EO:H2O ratio 10:1 to maximize MEG
production By Products DEG, TEG.

ACETALDEHYDE

Ethylene reacts with oxygen in presence of palladium catalyst at temperature 50100C and pressure below 50 atm, residence time 6-40 min

Propylene (CH3CH=CH2)

Propylene can be polymerized alone or copolymerized with other

monomers such as ethylene.
Many important chemicals are based on propylene such as
isopropanol, allyl alcohol, glycerol, and acrylonitrile.

Propylene often referred as the crown prince of petrochemicals is superficially

similar to ethylene but there are many differences in both production and uses
Propylene is used in many of the worlds largest and fastest growing synthetic
materials and thermoplastics. The demand of propylene has increased rapidly
during the last twenty years and primarily driven by polypropylene demand

Propylene Oxide
There are two major processes for the manufacture of propylene oxide:
Propylene chlorhydrin process and propylene oxidation process using peroxides
Propylene Chlorhydrin Route:
The chlorhydrination process consists of formation of propylene chlorhydrins
by the reaction between hypochlorous acid and propylene.
The propylene chlorhydrin is reacted to propylene oxide by a 10% solution of
milk of lime or NaOH. Various steps involved are
Propylene hypochlorination: Propylene is reacted with aquous chlorine
resulting in the formation of propylene chlorhydrins. Unreacted propylene is
recyled.
Neutralisation: Neutrialisation of propylene chlorhydrins containing
hydrochloric acid which is formed during the process.

Dehydrochlorination: Reaction of propylene chlorhydrin with milk of

lime or caustic soda to produce propylene oxide
Purification: Distillation of crude propylene oxide for separation heavy
ends
Propylene hypochlorination reaction is exothermic, max temperature 50 C
Byproducts formed during the reaction propylene di chloride
Reactions

Some of the disadvantages and major economic drawbacks of the

process which led to the wide acceptability of the process are
use of costly chlorine,
production of weak calcium chloride byproduct,
corrosion problem due to chlorine handling

Oxidation Route using peroxide Compounds: In this process, propylene and

peracetic acid (in ethyl acetate) which is produced by oxidation of acetaldehyde
are reacted in a series of three specially designed reactors at 50-80 C and 90-120
MPa pressure.
The reaction products are fed to the stripper where a mixture of propylene and
propylene oxide are obtained as top product while mixture of ethyl acetate and
acetic acid is obtained as bottom product.
Both mixtures are fed to two separated columns where separation of propylene
oxide, ethyl acetate, acetic acid, and heavy end takes place.

Propylene Glycol
Propylene glycol is made by hydrolysis of propylene oxide. The process steps
involve are:
Reaction Section: Hydrolysis of propylene oxide resulting in formation of
mono propylene glycols(MPG). Small amount of di propylene glycol (DPG)
and tri propylene glycol (TPG) s are also formed
Concentration Section: Concentration of glycol solution in multiple effect
evaporator
Distillation Section: Separation of MPG,DIPG and TPG separated from MPG
column. series of distillation column where MPG is separated in first column.

Acrylonitrile
Acrylonitrile cheapest of acrylic monomer
Use for polymers such as: Acrylic fiber, Plastics, Nitrile rubber,
acrylamide
Propyelene, ammonia , air oxidation
Reaction:
The reaction is exothermic
-Stoichiometric ratio: C3H6 : NH3 : O2 = 1:1:1.5
-Operating conditions: 1.5 3 atms pressure and 400 500C
-By products: Acetonitrile and Hydrogen cyanide from side reactions
- Catalyst: Mo-Bi catalyst , microspheroidal catalyst, 0.01-0.03 mm

Propylene + Propane, Air and Ammonia, Steam are compressed to required

pressure and are sent to the fluidized catalytic reactor consisting of the Mo-Bi
spherical catalyst.
The reactor is maintained at 400 500C.
Cyclone separator is also kept in the fluidized bed reactor in which catalyst and
product gases are separated after fludization.
The contact time for fluidization is in the order of seconds.
The product vapors then enter a water scrubber that does not absorb propane
and nitrogen from the products.
The products absorbed in the water include acrylonitrile, acetonitrile and other
heavy ends.
The very dilute acryolonitrile (about 3 %) solution in water is sent to a
fractionator.
The fractionators separates acrylonitrile + heavy ends + HCN + light ends as a
top product stream and acetonitrile + water + heavy ends as a bottom product.

The top product then enters an extractive distillation column with water as
extractant.
The azeotropic distillation column vapour is partially condensed to obtain a
vapour, aqueous and organic layer.
The vapour consists of Light ends and HCN and is let out.
The organic layer consists of acrylonitrile and heavy ends is sent for further
purification.
The aqueous layer is sent as a reflux to the azeotropic column. In other words,
addition of water enabled the formation of a heterogenous azeotropic mixture at
the top.
The bottom product from the azeotropic distillation column enters a product
purification unit along with oxalic acid where acrylonitrile is further purified
from heavy ends (+ oxalic acid) and is obtained as a 99.5 % pure product.

In similarity to this, the bottom product from the product splitter enters an
azeotropic column which produces water as a bottom product.
The total condenser in this column generates both aqueous and organic layers.
The organic layer is rich in acetonitrile and heavy ends where as the aqueous
layer is sent back as a reflux to the azeotropic column.
The bottom product from the acetonitrile azeotropic column enters a
purification unit where distillation principle enables the separation of acetonitrile
from the heavy ends.
Regeneration of catalyst is not required if the feed is desulphurized
Byproduct of the process are cyanohydrins-readily dissociate to form volatile
polluting compound
Addition of oxalic acid form complex compounds and enter in the heavy end

Cumene (Isopropyl benzene)

Developed for high octane addition for engine fuels. Major use as raw
material for producing phenol
Produced from Propylene alkylation of benzene
The reaction is exothermic

-Catalyst: H3PO4 catalyst on porous carrier

- Operating conditions: 25 atms pressure and 250 C temperature

Propylene obtained from refinery processes as a mixture of propylene and

propane
The mixture along with benzene is compressed to 25 atms
Eventually the mixture enters a heat integrated exchanger to heat the pre-heat
the feed mixture.
The feed mixture enters a packed bed reactor.
The stream distribution in the packed bed reactor corresponds to cold shot
arrangement i.e., cold propane from the distillation column in the process is
added after every reactor with the product stream so that the temperature of
the stream is controlled.
Here, propylene is the limiting reactant and therefore, presumably all
propylene undergoes conversion.

Here, propane does not react but is a diluents or inert in the system. In that
way it controls the reaction temperature.
The reactor units are maintained at about 250C

The product vapors are cooled using the heat integrated exchanger
The vapors then pass to a depropanizer which separates propane from the
product mixture.
The bottom product consisting of benzene, cumene and polyalkyl benzenes
enters another distillation column which separates benzene from the mixture
of cumene and polyalkyl benzene. The benzene stream is recycled to enter the
compressor.
The bottom product from the benzene column is sent to a cumene column
which produces cumene as top product and poly alkyl benzene as bottom
product.
Using high feed ratio of benzene to propylene and using propane as diluent
formation of polyalkylbenzene can be minimized