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Faculty of Process & Systems Engineering

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Simulation Lab WS
2017/2018

Supported
by:

Elizabeth
Richter

[email protected]

 

 

“Production
and Distillation of Cumene of the Hock Phenol Synthesis”

 

 

 

 

 

Date: 26.01.2018

Group Member:                      Course of Study            Matriculation number:

Mihir Khandelwal                             PSEE                             218017

Sannidh Ramoliya                             PSEE                             220845

Table of Contents

 

1. Introduction

2. Methods:
Properties and Procedure

3. Results

4. Conclusion

5. References

Appendix A: ASPEN
PLUS Simulation Model

Appendix B:
Results

1.      
Introduction

 

Cumene is produced with the reaction between benzene
and propylene, the process under consideration is hock-phenol process. In this,
the cumene produced is utilized to obtain phenol and acetone. The process was
described by Hock and Lang in 1944. The reaction to form cumene is desirable,
but reaction between cumene and propylene which forms diisopropyl-benzene
(DIPB) is undesirable. Both the reactions are irreversible.

 

The primary use of cumene is as a feedstock for the
manufacturing of phenol and acetone; however, it is used as starting reactants
for various chemicals. It is used as thinner in paints, enamels, lacquers.
Also, it is used in the production of rubber, paper, iron and steel.

 

 

§  Cumene
production reactions:

 

The reaction of
benzene with propylene is as follows:

 

 

C3H6         +      C6H6 ®       C6H5-C3H7

 

 

 

C3H6           +          C6H5-C3H7       ®        C3H7-C6H4-C3H7

 

 

 

 

Cumene (Isopropyl benzene) is an important component
in global chemical industries. As per a report (Wildcat market research
solution), in 2011 the production of cumene was 12 MT (million tons), which is
expected to increase by 50%, to 18 MT by 2020. This makes it a 20 billion
dollars industry per year. The demand is increasing in Asia-Pacific region,
which makes cumene production process important. The process can be simulated
using ASPEN, and the results can be obtained considering selectivity,
conversion, and feed in the mixture. With this, ASPEN model, we can vary feed
and check how much cumene is produced. Furthermore, description of process flow
made using ASPEN is discussed.

 

 

 

2.  
Methods:
Properties and Procedure

 

§  Properties
of cumene:

 

Description:            It
is a colorless liquid with gasoline like gasoline like odor. It is soluble in
alcohol, benzene and various inorganic components, but it is insoluble in
water. It is highly flammable.

Boiling
Point:         152.4 °C

Density:
                 0.8618 g/cm3 at 20 °C

Melting
Point:        -96.0 °C

Refractive
Index:   1.4915 at 20 °C

Flash
Point:                        39 °C, when
the cup is closed

Solubility:
             Not soluble in water,
miscible in benzene, acetone and ethanol.

Reactivity:
             Combustible, incompatible
with nitric acid, oxidizers and sulphuric acid.

 

(Reference:
Australian Government, Department of the Environment and Energy,
http://www.npi.gov.au/resource/cumene-1-methylethylbenzene)

 

§  Process
Economics:

The
costs of raw materials and products when considered for long term period, is
much higher than the cost of construction costs, energy or any initial
investments B. Process economics states that the reactants (Feed) conversion
to product should be as high as possible. Two principles are stated as per C.

(1)
The feed mixture contains benzene and propylene under normal atmospheric
conditions. The propylene feed stream contains impurity of propane, which
should be taken out. Propane under the reactor is inert, so its separation is
very time consuming and difficult. Instead, the better trade-off would be high
conversion of propylene.

(2)
The undesirable by-product, which has only the value of fuel, should be kept as
low as possible, as it consumes reactants.

 

§  Process
Description:

 

The
reactants benzene and propylene stored in their respective tanks are fed in the
reactor in liquid form, the feed temperature is kept under atmospheric
conditions, temperature is 25°C and pressure is 1 atmospheric bar. The feed is
kept in the ratio of 2:1, benzene to propylene respectively. This can be varied
as per needs to obtain different results. The temperature in the reactor is
maintained at 360°C and pressure of 25 atmospheric bar C.

 

Cumene obtained from benzene and propylene, also
produces undesirable by-product, which is of no relevance to us. This can be
done either by increasing benzene so that cumene and propylene concentrations
remain low but this will increase cost of separation A. Other method would be
if we increase the size of reactor provided the cost of material is
inexpensive.

If, the material cost is high, small reactor is the
only feasible option.

 

The
design of cumene production and distillation process is simulated using Aspen
Plus software. The process flow diagram (PFD) of the entire process is
illustrated below.

Figure 1: Process Flow Diagram of Cumene
process

 

Two
distillation columns and one flash tank are used to separate cumene from other
by-products and remaining reactants. Cumene process is mainly divided into two
sections: reactor section and separation section.

 

®     
Reactor section:

Reactors converts
cheap raw materials into desired, economical products. They play an important
role in terms of safety and environmental protection. A reactor is designed
with kinetics of reaction, experience, economic constraints and most
importantly thermodynamics. For a reaction to occur, we must specify reactants,
rate of reaction and products. Selection of reactor model depends on the
information available and type of simulation. ASPEN has 7 reactors for
modelling, they are: RStoic, RYield, RGibbs, RCSTR, RBatch, RPlug, REquil F.

 

RStoic
model can be used when the stoichiometry is known but the reaction kinetics is
unknown. It can have more than one feed streams, which are mixed in the reactor
to give single material-out stream.

Reaction
section consists of one reactor and two streamlines. Both reactants benzene and
propylene as liquids were fed into reactor at a temperature of 25°C
and pressure 1 bar. The temperature of the reactor has been set at 360°C
and pressure at 25 bars and there is no coolant used in the reactor C. All
the parameters that has been considered are described in below Table 1.

PROPERTIES

FEED

REACTOR (RSTOIC)

REACT-OUT

Temperature
(°C)

25

360

360

Pressure
(bar)

1

25

25

Mole
flow rate (kmol/hr)

100

100

70.3

Phase

Liquid

Vapor-Liquid

Liquid

 

Table 1: Parameters of
reaction section. All molar flow rate is in kmol/hr, temperature in °C
and pressure in bar.

 

®     
Separation section:

Separation
is a process of separating a mixture of substance into two or more distinct
products. Separation section consists of major three columns: flash tank,
distillation column 1 and distillation column 2. Reactor effluent, which leaves
reactor, is fed into flash tank where its temperature decreases. Propylene is
not in pure form, it contains propane as impurity, which is separated here.
This stream enters distillation column 1, where we get excess benzene present
in the process. As, benzene is obtained as top product, we name it benzene
distillation column. The bottom products then go to our other distillation
column, where we obtain residue (DIPB) as our bottom product which should be
kept to minimum and cumene as top product is gained, which should be high.

For shortcut
distillations, following models are available in ASPEN: DSTWU, Distl, and
SCFrac. We have selected Distl model for our process, as it is for
single column, free-water calculations in the condenser can be performed and it
allows us to draw water streams to free water streams from condenser F.

 

Distl model uses the
approach of Edmister, where we can separate inlet stream into two products (Top
and Bottom). It is a multicomponent model, for these we must mention values of
following parameters:

 

1.     
Number of Theoretical stages

2.     
Reflux ratio

3.     
Overhead product rate

Here, we can specify whether we want to
partial or total condenser.

 

SYSOP0
property method is selected for the distillation. In distillation column 1 the
pressure is kept fixed at 1 bar and other parameters such as: Number of Trays,
feed trays, distillate to feed mole ratio and reflux ratio have been obtained
from design book by Turton et al, (2003).

Number of stages

20

Number of feed stages

8

Reflux Ratio

0.42

Distillate to feed mole ratio

0.67

Condenser pressure (bar)

1

Reboiler pressure (bar)

1

 

Table 2: Input data for Distillation
column 1.

In
addition, for distillation column 2, the same property method is used. The
remaining substance from distillation column 1 were fed into distillation
column 2. In this column, cumene is obtained as a top product and other
residues have been collected as bottom product, in which DIPB is main substance
and that is why this column is called cumene column. In cumene column the
pressure is kept fixed at 1 bar and other parameters: Number of Trays, feed
trays, distillate to feed mole ratio and reflux ratio have been obtained from
design book by Turton et al, (2003).

Number of stages

20

Number of feed stages

10

Reflux Ratio

0.9

Distillate to feed mole ratio

0.33

Condenser pressure (bar)

1

Reboiler pressure (bar)

1

 

 

 

 

Table 3: Input data for Distillation
column 1.

 

3.
Results

After
performing simulation in Aspen Plus, results were obtained, which are mentioned
in the following Table 1. This table includes data such as: molar flow rates,
mass flow rates, temperature and pressure of all substances.

STREAM

FEED

BENZENE

CUMENE

PROPANE

RESIDUE

Phase

Liquid

Liquid

Liquid

Vapour

Liquid

Benzene

67

27.0938

1.96372 e-07

10.2062

6.58563 e-13

Propene

33

0.253354

0

3.04665

0

Cumene

0

10.0991

6.08641

1.15719

12.3573

Propane

0

0

0

0

0

Total Mole Flow

100

37.4463

6.08641

14.41

12.3573

Temperature

25

79.7081

151.908

92.5

151.908

Pressure

1

1

1

1

1

 

Table 1:
Molar flow rates, temperature and pressure of the streams. All mole flows are
in kmol/hr, temperatures in °C and
pressures in bar.

The
by-product propane has been separated in flash tank at a temperature of 92.5 °C
and pressure 1 bar. As shown in Table 1, propane is separated in vapour phase
at a rate of 14.41 kmol/hr. Stream 1 containing benzene, propene, cumene and
other by-products has fed into distillation column 1. In distillation column 1,
benzene is separated in liquid phase by distillation process.

Table
1 shows temperature, pressure and molar flow rate at which benzene is
separated. The remaining components of stream 2 flow to distillation column 2,
where cumene as a final product and diisopropyl benzene (DIPB) as by-product
has been distilled. The molar flow rate of cumene and residue are 6.08641
kmol/hr and 12.3573 kmol/hr respectively.

Table
2 and 3 represents mole fractions and mass fractions of the components. The
overall molar balances and mass balances of each streams have been balanced
throughout the process.

STREAM

FEED

BENZENE

CUMENE

PROPANE

RESIDUE

Benzene

0.67

0.723538

3.22639 e-08

0.70827

5.32936 e-14

Propene

0.33

0.00676579

0

0.211426

0

Cumene

0

0.269696

0.999999

0.0803043

0.999999

Propane

0

0

0

0

0

 

Table 2:
Mole fractions of the Components.

 

STREAM

FEED

BENZENE

CUMENE

PROPANE

RESIDUE

Benzene

0.790305

0.633478

2.09682e-08

0.748912

3.46352e-14

Propene

0.209695

0.00319113

0

0.120433

0

Cumene

0

0.363331

0.999999

0.130655

0.999999

Propane

0

0

0

0

0

 

Table 3:
Mass fractions of the streams.

 

 

4.      
Conclusion

 

The
cumene production process can be analyzed in two sections, Reactor and
Separator. The process involves trade-off between the size of reactor and
reactant flow rate. Process must be designed considering initial investment
cost and operational costs which includes energy costs, raw material costs. To
improve conversion of reactants to product cumene, we need to either provide
excess benzene or increase the size of reactor; both are expensive so depending
on the need, we must choose one. The benzene to propylene ratio was kept 2:1;
this can be varied to obtain different results. Also, the by-product should be
kept low as they consume our reactants.

The
hock-phenol process involves production of phenol and acetone from cumene, so
work can be carried out on that. In this process, RStoic reactor model is used
as stoichiometry of the reaction was known, reactor models such as RBatch,
RCSTR and RPLUG can be used, if reaction kinetics is considered.  Also, we have used benzene in excess to reduce
undesirable by-products; its recycling must be done.

5.      
References

 

A Turton, R., Bailie, R. C., Whiting, W. B.,
Shaelwitz, J. A. Analysis, Synthesis and
Design of

Chemical
Processes, 2nd Edition, Prentice Hall, Englewood
Cliffs, NJ, 2003

https://dredgarayalaherrera.files.wordpress.com/2015/08/analysis-synthesis-and-design-of-chemical-processes3rd-ed.pdf

 

B
Douglas, J. M. Conceptual Design of
Chemical Processes, McGraw-Hill, New York, 1988.

https://pdfs.semanticscholar.org/747c/a977200cbfd16a463ea790635836db603e9b.pdf

 

C
William. L. Luyben, Distillation Design
and Control Using Aspen Simulation, Wiley, New

York (2006).

https://www.aiche.org/sites/default/files/cep/20060553.pdf

 

D Nirlipt Mahapatra, Design and
Simulation of Cumene Plant using Aspen Plus, National Institute of
Technology Rourkela, 2010.

 

http://ethesis.nitrkl.ac.in/1746/1/nirlipt_ethesis.pdf

 

 E Global Cumene Market Size, Cumene Market Analysis By Production (Zeolite, Solid Phosphoric Acid,
Aluminium Chloride), By Application (Phenol, Acetone), By Region, And Segment
Forecasts, 2014 – 2025

https://www.grandviewresearch.com/industry-analysis/cumene-market

 

F
Aspen Technologies, Inc, Aspen Plus User
Guide, Version 10.2, February 2000.

https://web.ist.utl.pt/ist11038/acad/Aspen/AspUserGuide10.pdf

 

 

Appendix A:  ASPEN PLUS Simulation Model

Appendix
B: Results

STREAM

FEED

BENZENE

CUMENE

PROPANE

RESIDUE

REACT-OUT

STREAM 1

STREAM 2

Molar
Enthalpy (kJ/kmol)

40021.3

33626

-10311.9

69633.8

-10311.9

102596

15606.8

-10311.9

Mass
Enthalpy (kJ/kg)

604.344

376.894

-85.7937

942.594

-85.7938

1089.13

156.946

-85.7938

Molar
Entropy (kJ/kmol-K)

-213.925

-301.785

-473.215

-151.486

-473.215

-178.34

-364.295

-473.215

Mass
Entropy (kJ/kg-K)

-3.23039

-3.38252

-3.93708

-2.05058

-3.93708

-1.8932

-3.6634

-3.93708

Molar
Density (kmol/cum)

0.127062

9.04397

6.18491

0.0328933

6.18491

0.474904

7.98248

6.18491

Mass
Density (kg/cum)

8.41437

806.892

743.391

2.42998

743.391

44.7361

793.784

743.391

Enthalpy
Flow (Watt)

1.117e+06

349770

-17434.1

278729

-35396.5

2.0e+06

242295

-52830.5

The
reaction design reflects constraints and some consideration for future reports.
Table 4 shows results which are optimized from aspen plus. It includes molar
and mass entropy, density and enthalpy flow of each streams. These data are
required to perform mathematical simulation.

 

Table 4:
Specifications of each streams including molar and mass entropy and enthalpy,
mas density and enthalpy flow.

Table
5 represents reactants properties of reactants that are fed in. It also shows
reactor temperature, pressure, mole and mass flow rate.

PROPERTIES

FEED

REACTOR
(RSTOIC)

REACT-OUT

Temperature (°C)

25

360

360

Pressure (bar)

1

25

25

Mole flow rate (kmol/hr)

100

100

70.3

Mass flow rate (kg/hr)

6622.28

6622.28

4655.46

Phase

Liquid

Vapor-Liquid

Liquid

 

Table 5:
Properties and data of the feed stream, reactor and react-out stream.

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