3.

1 Process Modeling

This section presents the Aspen Plus-based model details for a process formation of
epoxy resin using a highly active Titanium Silicate 1 catalyst and separation purity of the
final product.

3.2 Process Property Model

The entire process was simulated in Aspen plus (version 14, Aspentech) software using
the NRTL thermodynamic property model which is most suitable for the aqueous involve
in the process. Moreover, it can be noted that all the binary interaction parameters
related to the property models NRTL are available in the pure components’ databank of
the Aspen plus process simulator.

3.3 Chemical Reactions and Kinetic Expressions

The four reactions (A, B, C, and D) involve in the Epichlorohydrin (ECH) synthesis
reaction system that result in the formation of epoxy resin are given below. The
components included are allyl chloride (AC), hydrogen Peroxide (HP), ECH, water (W),
1-chloropropane-2,3-diol (CPD), methoxypropan-2-ol (CMP), oxygen (O2) and methanol
(M). The reaction solution is pass over Titanium Silicate 1 (TS-1) catalyst.

A. AC + HP → ECH +W (3.1)

Side reactions

B. E C H +W ↔ CPD (3.2)

C. ECH + M ↔ CMP (3.3)

D. HP ↔ W +O2 (3.4)
3.3.1 Chemical Equilibrium
The equilibrium constants (b HP and b EC H ), with R = 8.314 J/mol K. The equilibrium
constants are calculated based on molar volume in (Lmol -1) using Aspen Plus. Since
those will be needed to express the driving force term of the kinetic rate equations.
 ( 19400
b HP=3.06 × 10− 4 exp ⁡
RT )

B
ln b HP =A + ( Aspen plus format)
T
(3.5)

A=ln ( 3.06 ×10−4 ) =−8.0919

19400 2333.43
B= =
8.314 × T T

2333.43
ln b HP =−8.0919+
T

b ECH =4 . 59 ×10−4 exp ⁡ ( 1 80R T00 )

(3.6)

A=ln ( 4 .59 ×10−4 ) =−7.68646

180 00 2165 . 02
B= =
8.314 × T T

2165.02
ln b ECH =−7.68646+
T

3.3.2 Catalytic Kinetics Expressions

For the ECH reaction, TS-1 catalysts are available based on kinetic formulations found
in the literature. Using Hougen-Watson Langmuir-Hinshelwood type reaction rate
equations. For the kinetic model TS-1 catalyst, the appropriate rate equations are as
follows:
 A.
k 1 b HP C HP C AC
r 1=
[ 1+b HP C HP +b ECH C ECH ]
(3.7)

where r 1 is the reaction rate for AC; C AC, C HP and C ECH are concentrations of the species

B.
k 2 b ECH C ECH C W
r 2=
[ 1+b HP C HP +b ECH C ECH ]
(3.8)

C.
k 3 b ECH C ECH C M
r 3=
[ 1+b HP C HP +b ECH C ECH ]
(3.9)
D.
k 4 b HP C HP
r 4=
[ 1+ b HP C HP + b ECH C ECH ]
(3.10)

Aspen Plus will employ the generalized rate expression, which is provided by:

kinetic factor ×driving force term

r=
adsorption term

(3.11)

Kinetic factor is the pre-exponential factor given in Arrhenius equation term

n
kinetic factor=kT exp ⁡(−Ea /RT )

(3.12)
It should be noted that the units of pre-exponential constant term are the same with
driving force and adsorption term.
The driving force term are expressed as follows:
 Reaction A:

(−55R ×T× 10 )
3
3
k 1=11.06×10 exp

(3.13)

Converting 11.06× 10 to for aspen plus input

3 L kmol
g.s k g .s

Given density of TS-1 as 550

g
L
3 L g 1 kmol 1000 g 6 kmol
11.06× 10 ×550 × × =6.083 ×10
g.s L 1000 mol 1 kg k g.s
Rewriting 3.13

( )
3
6 −55 ×10
k 1=6.083 ×10 exp Reaction B:
R ×T

( )
3
3 −66 × 10
k 2=1.12 ×10 exp
R ×T
(3.14)

Converting 1. 12× 10 to for aspen plus input

3 L kmol
g.s kg . s

Given density of TS-1 as 550

g
L
3 L g 1 kmol 1000 g 5 kmol
1. 12× 10 ×550 × × =6. 16 ×10
g.s L 1000 mol 1 kg kg . s
Rewriting 3.14

( )
3
5 −66 ×10
k 2=6.16 × 10 exp
R× T

Reaction C:

( −70.6
R×T )
3
3 ×10
k 3=6 . 71×10 exp

(3.15)

Converting 6 . 71× 10 to for aspen plus input

3 L kmol
g.s kg . s

Given density of TS-1 as 550

g
L
 3 L g 1 kmol 1000 g 6 kmol
6 . 71× 10 ×550 × × =3 . 6905 ×10
g.s L 1000 mol 1 kg kg . s
Rewriting 3.15

( )
3
6 −70.6 ×10
k 3=3.6905 ×10 exp
R ×T

Reaction D:

(−5 0.R ×T )
3
0 ×10
k 4=12.93 exp

(3.16)

Converting 12.93 to for aspen plus input

L kmol
g.s kg . s

Given density of TS-1 as 550

g
L
L g 1kmol 1000 g kmol
12.93 × 550 × × =7111.5
g.s L 1000 mol 1 kg kg . s
Rewriting 3.16

( )
3
−5 0. 0× 10
k 3=7111.5 exp The adsorption term is the denominator of reactions in
R×T
equation 3.7-3.10

[ 1+b HP C HP +b ECH C ECH ]

(3.17)

Table 3.1: The kinetic factor and driving force term values with chemical equilibrium value.

Reactions Expression k i ki Expression b i ln b i

( )
A k 1(k mol/ kg . s) −55× 10
3 b HP 2333.43
6.083 ×10 exp
6 −8.0919+
R ×T T

( )
B k 2( k mol /kg . s) −66 ×10
3 b ECH 2165.02
6.16 ×10 exp
5 −7.68646+
R×T T

( −70.6 × 10 b ECH
)
C k 3(k mol /kg . s) 3 2165.02
3.6905 ×10 exp
6 −7.68646+
R ×T T
 ( )
D k 4 (k mol /kg . s) −50.0 ×10
3 b HP 2333.43
7111.5 exp −8.0919+
R ×T T

Table 3.2: The driving force term values converted to Aspen plus format.

Reaction k 1 (First term) k 2 (Second term)

s
A B A B
A -8.0919 2333.43 -100 0
B -7.68646 2165.02 -100 0
C -7.68646 2165.02 -100 0
D -8.0919 2333.43 -100 0
-100 implies ln(∞ )=0 in order to eliminate second term

The adsorption terms depend on temperature (T) which is given as

b i=bo ,i exp ⁡(Qi / RT )

(3.18)

It should be noted that the expression in Equation (3.18) can be converted Aspen Plus
format as found in Equation (3.5). The adsorption expression values are computed in
Table 3.3.

Table 3.3: The derived adsorption term in Aspen plus format

Reaction A, B, C and D
Term Expression A=ln(bo ,i ) B=Qi ∏ Ckvk
1 1 0 0 -
2 b HP -8.0919 2333.43 C HP
3 b ECH -7.68646 2165.02 C ECH
3.4 Process Flowsheet Description

The process is initiated by mixing the AC, Methanol and HP in a mixer. The product of
the mixer (stream 3) proceed to reactor (RPLUG) input where the reaction take place in
the presence of (TS-1) catalyst. The reaction kinetics and reaction schemes were
evaluated and most of the chemical reaction were modeled using the Langmuir-
Hinshelwood-Hougen-Watson (LHHW) formulation to account for the effect of
adsorption of reactants and products on the active sites of the catalyst as earlier
reported in the previous section. The LHHW kinetic models were used for the adiabatic
and non-isothermal jacketed reformer reactor were implemented in the process
simulator Aspen Plus using plug flow reactor as shown in Fig. 3.1. The plug flow reactor
(RPLUG) model of Aspen plus is designed to perform mass transfer calculations
involving estimation of the effective diffusivity of the different species at the catalyst
side. The reactor operating conditions for the process simulation are shown in Table
3.4. The product stream of the reactor (stream 4) was separated in a distillation column
(modelled RADFRAC) in Aspen Plus where the number of stages is 50, reflux ratio of 2
and bottom rate 235 kg/hr to achieve 90% mass purity of ECH.

Figure 3.1: Process flow diagram for production of ECH.

Table 3.4: Reaction conditions for autothermal reforming of heptane

Reactor temperature (℃) 60
Reactor Pressure (atm) 3.5
AC flowrate (kg/hr) 250
Methanol flowrate (kg/hr) 20
HP flowrate (kg/hr) 100
Catalyst Density (kg/m3) 550
Catalyst loading (kg) 100
Bed Voidage (Porosity) 0.5
Reactor Length (m) 4
Reactor Diameter (m) 1

Results

Stream Results Summary

Material
Stream Name Units 3 4 5 AC-M ECH HP
Phase Liquid Liquid Liquid Liquid Liquid Liquid
Temperature C 62.08 60.00 29.79 60.00 120.69 60.00
Pressure bar 3.55 3.55 1.01 3.55 1.01 3.55
Mass Flows kg/hr 370.00 370.00 135.00 270.00 235.00 100.00
ECH kg/hr 0.00 253.65 42.04 0.00 211.61 0.00
AC kg/hr 250.00 25.47 25.47 250.00 0.00 0.00
HP kg/hr 100.00 0.00 0.00 0.00 0.00 100.00
CPD kg/hr 0.00 4.79 0.00 0.00 4.79 0.00
CMP kg/hr 0.00 18.60 0.00 0.00 18.60 0.00
WATER kg/hr 0.00 52.18 52.18 0.00 0.00 0.00
OXYGEN kg/hr 0.00 0.09 0.09 0.00 0.00 0.00
METHANOL kg/hr 20.00 15.21 15.21 20.00 0.00 0.00
Mass Fractions
ECH 0.00 0.69 0.31 0.00 0.90 0.00
AC 0.68 0.07 0.19 0.93 0.00 0.00
HP 0.27 0.00 0.00 0.00 0.00 1.00
CPD 0.00 0.01 0.00 0.00 0.02 0.00
CMP 0.00 0.05 0.00 0.00 0.08 0.00
WATER 0.00 0.14 0.39 0.00 0.00 0.00
OXYGEN 0.00 0.00 0.00 0.00 0.00 0.00
METHANOL 0.05 0.04 0.11 0.07 0.00 0.00