Soran university
Faculty of engineering
Department of Chemical Engineering
DESIGN & SIMULATION OF NITROBENZENE
MANUFACTURING PROCESS
Name of student : kasar khanadal mhe
Supervisor:mr.ali
2019-2020
SR.NO. CONTENTS PAGE NO.
1 2
Introduction
2 Literature Review 3
Process For Production Of Nitrobenzene
Selection Of Process
Manufacturing Process Of Nitrobenzene
Chemical And Physical Properties
3 Thermodynamic Feasibility 10
Reaction Data For Formation Nitrobenzene
Calculations
4 Design Of Distillation Column 16
5 Simulation Using Aspen 20
Introduction to Aspen
Starting With Process Simulation
6 Result summary 23
Material Balance Over Reactor
Material Balance Over Decanter
Material Balance Over Distillation Column
Overall Material Balance
7 Conclusion 25
8 26
References
INTRODUCTION
Sources
Nitrobenzene is primarily used for the production of aniline. It is also used in soaps, in shoe polishes, for
refining lubricating oils, in the manufacture of pyroxylin compounds, and as a solvent. Nitrobenzene is also a
product of the photochemical reaction of benzene with oxides of nitrogen (HSDB, 1991). Nitrobenzene has
been detected but not quantified in motor vehicle exhaust (ARB, 1990b).
The primary stationary sources that have reported emissions of nitrobenzene in California are colleges and
universities, manufacturers of electronic components and accessories, and research and testing services
(ARB, 1997b).
property of benzene
Benzene, C6H6, was discovered by Michael Faraday in 1825. It is a hydrocarbon obtained from the distillation of coal
tar. It is a member of a large family of organic compounds called aromatic compounds.
The term aromatic was initially used because these compounds possess certain characteristic odor (or aroma), but
now, it is used to describe compounds which possess certain common features.
Some of these features are:
1. They are cyclic (i.e., ring) compounds.
2. Their molecules are planar.
3. They are unsaturated, and contain delocalized electron clouds above and below the ring.
4. They obey Huckel’s rule - i.e., there are (4n+2) electrons involved in the delocalization, where n is the number of
rings available.
Therefore, for benzene (n =1) - there are 6 delocalized electrons in the ring.
5. They exhibit resonance.
Structure of Benzene
Benzene has a molecular formula of C6H6 which indicates it to be unsaturated.
In 1865, a German chemist, August Kekulé, proposed that the structure of benzene is a ring called cyclohexatriene.
Although this was a great step forward, it could not explain the stability of the ring. However, modern methods for
investigating chemical structures, such as X-ray determination, have revealed that the benzene molecule is flat and that
the six carbon-carbon bonds are of equal length, 1.39Å.
If there were three single and three double bonds, we would expect their lengths to be 1.54Å and 1.34Å, respectively,
since these are the bond lengths in alkanes and alkenes.
The fact that the bonds in benzene seem to be intermediate between single and double bonds has received its most
satisfactory explanation by the application of the theory of resonance.
This theory explains that the three electron pairs (or six electrons) enclosed in the ring are not localized or fixed at a
particular position, but are free to move about within the ring. Hence, two equally reasonable structures which differ
only in the location of electrons can be written for the benzene molecule:
Notice that the “real” structure is neither of these. The real structure is a resonance hybrid that is intermediate in
character between the two.
All six carbon-carbon bonds are equivalent. Each is more than single and less than double. That is, the real structure is
a hybrid bond that cannot be satisfactorily represented on paper or with models. However, there are two methods that
are used in attempting to represent the structure of benzene.
1. By writing the two contributing structures above with braces enclosing them and a two-headed arrow separating
This symbolism must not be taken to mean tht molecules of two structures exist in equilibrium, but that only one kind of
molecule exists: a hybrid of the two contributing structures.
2. By using a simplified symbolism. This is frequently used, and it consists of a hexagon with a circle inside:
From the Kekulé structure of benzene above, it is seen that all the carbon atoms use sp 2 hybridization. Each carbon
atom, using it’s sp2 hybridized orbitals forms a sigma bond with an adjacent member (i.e. sp 2-sp2 ), and another sigma
bond with the s orbital of hydrogen. A pi () bond is formed between the unhybridized 2p orbitals.
Properties of Benzene
Physical Properties
1. Benzene is a liquid with a sweet smell (or aroma).
2. It burns in air with a sooty flame - due to high proportion of unburnt carbon.
3. It is insoluble in water, but dissolves organic compounds.
4. It has a boiling point of 80oC
PHYSICAL PROPERTY-
Refractive index 1.49792
Viscosity (absolute, at 20°C) 0.6468
Flash point, °C -11.1
Heat of fusion, kJ/kmole 9.847
Table No-2.1 Properties Of Benzene
Chemical Properties
The characteristic reactions of benzene are substitution reactions in which one or more hydrogen atoms are replaced
with another atom or group of atoms.
However, addition reactions occur, but only under drastic conditions, such as high temperature and pressure and the
use of catalysts. This shows that benzene is highly stable, in spite of the fact that it is highly unsaturated.
2.1 PROCESS FOR PRODUCTION OF NITROBENZENE
Nitrobenzene is manufactured by nitration of benzene using mixture of Nitric and sulphuric
acid.
Nitration can be done by two processes. Via.
Batch Process.
Continuous process.
2.1.1 BATCH PROCESS
In batch process the nitrator is charged with benzene and mixed acid (HNO3 32 – 39
%, H2SO4 60 -53 %, H2O 8%) is added slowly below surface of benzene. The rate of agitation
is such that both the acid & benzene phases are in intimate contact. The feed rate of mixed acid
and the rate of cooling are such that during the entire period of acid addition, the temperature of
nitrator is maintained at 323 -328 K. after complete addition of acid, The acid and organic
layers are drained into separate vessel from where spent acid is drawn off for reconcentration.
This crude product is washed with water to remove contamination in the nitrobenzene and the
aqueous sodium carbonate solution to remove small traces of nitro phenols formed during
nitration. Particularly when the product is to be further nitrated, removal of nitrophenolic
impurities is important, since they way undergo unwanted side reaction during subsequent
nitration. The product is further purified by distillation and the yield is 95 – 98% of the
theoretical.
CONTINUOUS PROCESS
A continuous process for the production of nitrobenzene has been developed by M / S.Biazzi of
Switzerland. The advantages of this process are the lower concentration of mixed acid is used
and higher reaction, rates though the sequence of operations is the same as in bath process.
Continuous nitrator with capacity of 150 lit. Can produce as a 7500 capacity batch nitrator, but
at the same time of quantity a reactants in nitrator is considerably small, unlike the batch
process.
Mixed acid and benzene are fed to nitrator in such that all nitric acid is utilized for nitraton of
benzene. The reactants are kept mixed under high speed agitation (600 rpm) and cooling. Due
to the controlled feed rate and rapid agitation, the reaction time is 15 to 20 minutes only at
reaction mixture is drawn off side of nitrator. The mixture is sent to decanter, where the,
product is separated from spend acid for further processing.
2.2 SELECTION OF PROCESS
Continuous process, in general, will be found to have the following to have the following
advantages over batch process.
Lower Capital Cost.
Safety
Labour Usage.
2.2.1 LOWER CAPITAL COST
For a given rate of production, the equipment needed for a continuous process is smaller than
for a batch process. This is usually the striking different between the two types of process.
The reason for that is obvious since, it is not necessary to accumulate material in a
continuous process anywhere; the vessel is designed with capacity dictated by the rate of
reaction process step which they must accommodate. Alternatively, because of relatively
small size of continuous process equipment, it is often possible and excessively high in cost
for batch scale equipment. Thus for example Corrosion resistance alloys such as appropriate
S.S. may be detected for a batch plant because of cost. In case of S.S. corrosion problems are
completely eliminated.
2.2.2 SAFETY
Because of relatively small size of continuous process equipment, there is less material in
process at any time than at certain in a comparable batch process. At the completion of batch
process nitration and during its normal separation of product from spent nitrating acid, the
entire batch of an often hazardous compound will be present in the equipment.
In the continuous process, only as much material need be present in hazardous conditions as
needed to again sufficient reaction of process time. In case of high explosive made by
nitration, this process has inherent safety factor is very attractive [3].
2.2.3 LABOUR USAGE
In the nitration filed the continuous process is usually more efficient labour usage than a
batch process. This is particularly true for small or medium scale production and for
hazardous products, since continuous processing minimizes the amount the material in
process on average. It is often possible to handle operations at one place that efficiency tends
to disappear as the scale of operations increases.
2.3 MANUFACTURING PROCESS OF NITROBENZENE
Nitrobenzene is manufactured commercially by direct nitration of benzene using a mixture of
nitric acid and sulphuric acid, which is commonly referred to as mixed acid for nitrating acid.
The reaction is conducted is specially build cast iron are S.S. reaction vessel
provided with agitator, external jacket and internal coils. Since two phases ate formed in
reaction mixture and reactant ate distributed between them. Rate of nitration is controlled by
transfer between the phases as well as by chemical kinetics.Benzene used is of commercial
quality. Mixed acid contain of 56 – 60 wt % H 2SO4, 20 – 26 wt% nitric acid and 15 – 18%
water. Sulphuric acid used is of 94% - 98% concentration and nitric acid commercial grade
of 55% - 60% concentration.
Benzene is charged to the nitrator. Mixed acid is slowly added on surface of benzene from
dosing tank with stirring. The ratio of mixed acid to benzene is kept around 2.5 : 1.0. The
temperature mass is maintain initially at 25 – 30°C. So by high speed agitator and proper
cooling coils reaction temperature can maintained upto 50 – 55°C. By obvious agitation, the
interfacial area, of the reaction mixture is maintained as high as possible, thereby enhancing
the mass transfer of reactants and cooling coils, which control the temperature of highly
exothermic reaction.
A slight excess of benzene usually is fed into the nitrator of ensure that the nitric acid in
mixed acid is formation of denitrobenzene. Reaction time is only 15 – 20 minutes because of
rapid and efficient agitation.
Nitrobenzene and spent acid are removed from the side reactor and send to decanter unit.
Organic and aqueous layers are formed, where two layers are separate in 10 to 20 minutes.
The aqueous phase or spent acid is drawn from the bottom and is concentrated in a sulphuric
acid is drawn from the bottom and is concentrated in a sulphuric acid reconcentration step or
is recycled to the nitrator, where it is mixed nitric acid and sulphuric acid immediately prior
to being fed into nitrator.
The crude Nitrobenzene can used directly for production of aniline if required, otherwise the
crude nitrobenzene flows through a series of washer – separators, where residual acid is
removed by washing with a dilute sodium carbonate solution followed by final washing with
water.The product is then distilled to remove benzene and the nitrobenzene can be refined by
vacuum distillation. Theoretical yields are 96 – 99 %. The nitration process is unavoidably
associated with the disposal of waste water from washing step. This water principally
contains Nitrobenzene, some sodium carbonate and inorganic salts from the neutralized spent
acid which was present in the product. Generally, the waste water is extracted with benzene
to remove the nitrobenzene and the benzene that is dissolved in the water is stripped from
water prior to the final waste treatment.
REACTION:-
C6H6 + HNO3 <===============> C6 H5 NO2 + H2O
DATA :-
HEAT OF FORMATION ( kcal/gmole)
Benzene (liquid) 11.71
Nitrobenzen (liquid) 13.76
Nitric acid (liquid) -41-61
Water (liquid) -68.315
Table No. 2.5 Enthalpy Data At Standard State
ENTHROPY kJ/(kmol.K)
Benzene (liquid) 172.915
Nitrobenzene (Liquid) 364.61
Nitric acid (liquid) 110.113
Water (liquid) 69.92
Table No. 2.6 Entropy Data At Standard State
SPECIFIC HEAT AT 25 °C kJ/(kmol.K)
Benzene (liquid) 91.73
Nitrobenzene (liquid) 185.361
Nitric acid (liquid) 111.113
Water (liquid) 75.362
Table No. 2.7 Specific Heat Data At Standard State
Fig No-2.1 Manufacturing Process Of Nitrob
DESIGN OF DISTILLATION COLUMN
Basis ; 1 hour of operation.
Mass flow rate of feed = 740.75 kg/hr.
Mass flow rate of distillate = 32.3 kg/hr.
Mass flow rate of bottom = 708.38 kg/hr.
Xf =
= 0.317/1.401
= 0.226
Xd = 2.8075/3.048
= 0.92
Xw = 0.0036/1.08667
= 0.003
Average Molecular weight of feed = 110.556
Feed rate = 593.568 kg/hr
Slope of q-line ;
We know that q = Hg-Hf / Hg-Hl
q=1
slope of q-line:
slope of q-line = q/q-1
= 1/1-1
Tan-1(α) = 0
q line is st.line
Xd / Rm+1 = 0.05
Rm+1 = 1/0.05
Rm+1 = 20
Rm = 19
R = 1.2 Rm
R = 22.8 ∼ 23
Xd = 1 = 0.042
Rm+1= 23+1 =24
From Mc-cabe Thile Graph
X 0 0.01 0.02 0.03 0.045 0.07 0.10 0.155 0.20 0.30
Y 0 0.03 0.485 0.63 0.74 0.82 0.88 0.92 0.94 0.964
Ideal Plate = 16 (From Graph)
Actual Plate = Ideal/n = 16/0.6
Actual Plate = 26.66
Height:
Plate Spacing = 450 mm = 0.45m
Ht = (Actual Plate-1)×0.45 + 2(0.45)
= 12.45m
Diameter :
Vap rate = v = D(R+1)
= 0.0087(23+1)
n = 0.21 kmole/hr
Top Column :
Vol.rate = nRT/P
= 0.21×8.314×103×(82+273)/ 1.01325×105 = 6.1170 m3/hr
Vol rate = 1.7×10-3 m3/sec
Velocity = 1 m/sec
Area = Vol rate / Velocity
= 1.7×10-3 /1 = 1.7×10-3 m2
Area = π D2 /4
D2 = 4A /π
D = 0.047 m
Bottom column:
Vol.rate = nRT/P
= 0.21×8.314×103×(210+273)/ 1.01325×105 = 8.32 m3/hr
Area = Vol .rate / Velocity
Velocity = 1 m/sec
Area = 2.31×10-3 m2
A = π D2 / 4
D2 = 4A /π D =
0.054 m
Both diameters are approximately same ,
we choose the larger diameter (i.e) bottom diameter
Bottom diameter D= 0.054 m
DESIGN SUMMARY
Ideal plate = 16.00
Actual Plates = 26.66
Column Height = 12.45 m
Column Diameter = 0.054 m
Fig No. 4.1 Rectification Section
Fig No-4.2 Stripping Section
SIMULATION USING ASPEN
5.1 INTRODUCTION TO ASPEN
5.1.1 What is a Process Flowsheet?
Process flowsheet can simply be defined as a blue print of a plant or part of it. It identifies all
feed streams, unit operations, streams that inter-connect the unit Operations and finally the
product streams. Operating conditions and other technical Details are included depending on
the detail level of the flowsheet. The level can vary from a rough sketch to a very detailed
design specification of a complex plant. For steady-state operation, any process flowsheet leads
to a finite set of algebraic equations. For a case where we have only one reactor with
appropriate feed and Product streams the number of equations may be manageable by manual
hand calculations or simple computer applications. However, as the complexity of a flowsheet
Increases and when distillation columns, heat exchangers, absorbers with many purge and
recycle streams come into the picture the number of equations easily approach many ten
thousands. In these cases, solving the set of algebraic equations becomes a Challenge in it.
However, there are computer applications called process flowsheet simulators specialized in
solving these kinds of large equation sets. Some well-known process flowsheet simulators are
Aspen Plus, ChemCad and PRO/II.These products have highly refined user interfaces and on-
line component databases. They are used in real world applications from interpreting laboratory
scale data to monitoring a full scale plant.
5.2 STARTING WITH PROCESS SIMULATION
1] First stating with Blank Simulation we must design our required flowsheet with proper
stream names & block names .each stream is properly connect to the proper unit.After doing
this we click Next to the required input step by step.
Fig No 5.1-Flowsheeting
2] we input Title of our simulation with all units are in SI units.
RESULT SUMMARY
6.1 MATERIAL BALANCE OVER DEACNTER
INPUT OUTPUT
(kg/hr) (kg/hr)
SR. COMPONENTS SPENT ACID ORGANIC PHASE
NO STREAM
1 BENZENE 91.07 2.09 88.98
2 NITROBENZENE 486.2 9.88 476.32
3 WATER 241.84+2000 2241.43 0.41
4 NITRIC ACID 0.89 0.89 -
5 SULPHURIC 580 553.51 26.49
ACID
TOTAL 3400 3400
Table No.6.2 Material Balance Over Decanter
6.2 MATERIAL BALANCE OVER DISTILLATION COLUMN
INPUT OUTPUT
(kg/hr) (kg/hr)
SR. COMPONENTS TOP PRODUCT BOTTOM PRODUCT
NO
1 BENZENE 88.98 78.6 10.38
2 NITROBENZENE 476.32 - 476.32
3 WATER 0.41 0.41 -
4 NITRIC ACID - - -
5 SULPHURIC ACID 26.49 - 26.49
TOTAL 592.2 592.2
Table No.6.3 Material Balance Over Distillation Column
OVERALL MATERIAL BALANCE
INPUT OUTPUT
(kg/hr) (kg/hr)
SR. COMPONENTS TOTAL SPENT TOP PDT BOTTOM
NO ACID STREAM PDT
STREAM STREAM
1 BENZENE 400 2.09 78.6 10.38
2 NITRIC ACID 250 0.89 - -
3 SULPHURIC 580 553.51 - 26.49
ACID
4 WATER 170 + 2000 2241.43 0.41 -
5 NITROBENZENE - 9.88 - 476.32
TOTAL(kg/hr) 3400 3400
Table No. 6.4 Overall Material Balance
Conversion of benzene is 77 %
Purity of Nitrobenzene in bottom product is 92.8 %.
CONCLUSION
It is very important for any process to kow that parameters like composition, streams,
temperature, pressure etc may affect the production rate.One must have perform pilot plant in
order to know this, so each time we need manual calculation to get desired results,this is so
time consuming. So the use of simulaters like ASPEN, CHEMCAD are helpful.Simulation &
modeling useful in doing risk analysis in production process.
In our project we simulate continuous process for nitrobenzene production using
benzene nitration.In that we know about how actually parameters mention above may affect
each stream.For example we first added calculated amount of extra water to decanter,but
from that action we know that how much extent it affect the each stream,so we are finaly able
to find the optimum amount of water required for operation.
Generally it is difficult to obtain desired result manually that is why we simulate it
using ASPEN PLUS .And we searching new techniques as possible in order to get the
optimum production. Also we can check where is the opportunity to increase the conversion
& reduce the losses as well as maintenance cost.
REFERENCES
Books,
[1]B.I. Bhatt & S.M. Vora. “ Stoichiometry”, Tata – Mcgraw Hill Publishing Co. Ltd.
[2]Dryden C. E., “Drydens Outline Of Chemical Technology”. East – West Press Pvt.
Ltd;(536)
[3]G. D. Muir, “Hazardous In Chemical Laboratory” The Chemical Society, London.
[4]Kirk – Othmer „Encyclopedia Of Chemical Technology‟.Vol. – 15. Wiley
Intenscience Publications, 1979.(138-139)
[5]P.H.Groggins .„Unit Process In Porganic Synthesis.‟ Mcgraw – Hill International
Book Co.
[6]R.Norris Shreve & Joseph A. Brink Jr.„Chemical Process Industries‟.Mcgraw – Hill
International Publications.(776-778)
[7]Robert H. Perry „Perry‟s Chemical Engineering Handbook‟.Mcgraw – Hill
International Publications.(642-644)
[8]Amiya K. Jana. „Process Simulation And Controle Using Aspen‟.PHI Learning
Private Limited ,Second Edition ,2012
[9]Bhattacharya A., Purohit V. C., Suarez, V.; Tichkule, R; Parmer, G.; Rinaldi, F.
(2006). "One-step reductive amidation of nitro arenes: application in the synthesis of
Acetaminophen" Volume 47, Issue 11, 13 March 2006, Pages (1861–1864)
[10]M.V.Joshi,Mahajani, Joshi's Process Equipment Design, Macmillan, 2009
[11]K.A.Gavane,”Chemical Reaction Engineering-I”,Nirali Publication,2012, Chapter 6
(6.1-6.15)
Journal Papers,
[12]R. D. BIGGS and R. R. WHITE „ Rate of Nitration of Benzene with Mixed Acid‟
University of Michigan, Ann Arbor, Michigan 2000
[13]J. Chil. Chem. Soc. vol.57 no.2 Concepción 2012, págs: 1194-1198.
[14]V. Dubois, G. James, J.L. Dallons, A. Van Geysel, In Catalysis of Organic Reactions,
M. Ford, Ed; Marcel Dekker, New York, 1994, Vol.82, p. 1.
[15]Laali, Kenneth K., and Volkar J. Gettwert. “Electrophilic Nitration of Aromatics in
Ionic Liquid Solvents.” The Journal of Organic Chemistry 66 (Dec. 2000): 35-40.
American Chemical Society.
[16] Sauls, Thomas W., Walter H. Rueggeberg, and Samuel L. Norwood. “On the
Mechanism of Sulfonation of the Aromatic Nucleus and Sulfone Formation.” The Journal of
Organic Chemistry 66 (1955): 455-465. American Chemical Society.
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