Simulation Study on Production of α-Terpineol from α-Pinene Isolated from
Turpentine from Indonesia Using Reactive Distillation Column
1
123
Tya Indah Arifta*, 2Sutijan, and 3Arief Budiman
Chemical Engineering Department, Gadjah Mada University, Indonesia
Jl. Grafika, No. 2, Yogyakarta, Indonesia, 55281
*E-mail: arifta87@gmail.com
Abstract
Turpentine is one of the essential oils obtained from pine trees and cannot be used for making any
derivatives since it contains several components depending upon the species of the pine trees. We have
succeeded to isolate α-pinene with 97 % purity from Indonesian turpentine using continuous low-pressure
distillation. Alpha-pinene can be readily converted into many chemicals having important pharmaceutical
properties including α-terpineol by acid-catalyzed hydration process.
Alpha-terpineol is valuable compound widely used for fragrant substance in the cosmetic
industry, anti fungal pharmaceutical industry, disinfectant, odorant in the cleaning industry and mineral
flotation agent in the mining industry. A conventional configuration for this hydration process involves
two steps, chemical reaction in a reactor followed by separation step in a distillation column. In this
study, both chemical reactions and separation by distillation were carried out simultaneously in reactive
distillation. Alpha-pinene 97%, which is distilled from the Indonesian turpentine as feeds and
chloroacetic acid as a catalyst. We simulated this process using Aspen plus and studied effect of the main
parameter, which includes reflux ratio, distillate rate and plate number on the conversion of α-pinene to
α-terpineol.
Key words: α-pinene hydration, α-terpineol, reactive distillation, aspen plus
Introduction
Turpentine is one of the essential oils obtained
from pine trees. Highly purified α-pinene that has
to reach 97% purity can be obtained by vacuumfractional distillation of turpentine [2].
When treated with water in the presence of
acid catalyst, α-pinene is hydrated to complex
mixtures
of
monoterpenes,
alcohol
and
hydrocarbons, although α-terpineol predominates.
α-terpineol is a valuable compound widely used
for fragrant substance in the cosmetic industry, anti
fungal in pharmaceutical industry [7], disinfectant
[14], odorant in the cleaning industry [1] and
mineral flotation agent in the mining industry [4].
Hydration of α-pinene by homogeneous acid
catalysts yielding α-terpineol has been studied
since the 1930s, when Charlton and Day (1937)
studied the hydration of α-pinene using sulfuric
acid at low temperature [3]. Then, Williams and
Whittaker (1971) investigated the rearrangements
of acid-catalyzed hydration of α-pinene in aqueous
and anhydrous acetic acids [13].
Pakdel et al (2001) studied hydration of crude
turpentine oil which contains 52% α-pinene and
used sulfuric acid as catalyst in the presence of
acetone. They reported the main hydration product,
α-terpineol, was obtained at a yield of 77.2%
(based o the quantity of α-pinene in the oil) by
reacting 2 g of crude turpentine oil with 15% (v/v)
aqueous sulfuric acid and with an excess of
acetone. They also studied effects of good
homogeneity of the initial mixture by the use of an
emulsifier. The results were not as good as
expected. An increase in the quantity of αterpineol formation was noted throughout the
temperature range. However, the yield were lower
than than those obtained using a procedure without
an emulsifier [6].
In 2005, Roman-Aguirre et al studied the role
of chloroacetic, oxalic and acetic acid catalysis for
hydration of α-pinene to terpineol using water as
the hydroxyl group donor. Chloroacetic acid was
found as good catalyst for the production of
α-terpineol from pinene results are due to strong
acidity and high solubility and affinity with
aqueous and organic phase during reaction. The
higher conversion was 99% with selectivity of
70% after 4 h of reaction at 70oC [8].
The industrial α-terpineol plant is designed
with two main equipment. Hydration reactor to
produce terpene hydrate and then following dehydration in distillation column to produce
perfumery α-terpineol in distillation column. In
this article, we integrate chemical reaction in
reactor and physical separation in distillation
column into a single unit of reactive distillation
column. Then, we analyze and discuss
comprehensively the main parameter of reactive
distillation using Aspen plus, which is widely used
for the flow sheet simulation in the process
industries.
Materials
Table 1 shows composition of α-pinene
solution, which is distilled from the Indonesian
turpentine as feed and Table 2 shows physicchemical properties of chemical species in the
α-pinene hydration process.
Table 1. Composition of α-pinene solution
α-pinene
Composition
(mass fract)
0.9709
Component
β-pinene
0.0160
camphene
0.0128
limonene
0.0002
carene
1.10E-09
Table 2.
Normal boiling points of chemical
species in the α-pinene hydration
Chemical Name
Chemical Formula
α-pinene
β-pinene
camphene
limonene
carene
chloroacetic acid
water
α-terpineol
C10H16
C10H16
C10H16
C10H16
C10H16
C2H3ClO2
H2 O
C10H18O
Mw
TB
(g/mol)
(K)
136.24
136.24
136.24
136.24
136.24
94.5
18.02
154.25
429.29
439.19
433.65
450.6
491.9
462.5
373.15
540.84
We react α-pinene 97% and water with
chloroacetic acid as catalyst. Chloroacetic acid was
found as good catalyst for the production of
α-terpineol from pinene results are due to strong
acidity and high solubility and affinity with
aqueous and organic phase during reaction [8].
Experimental
Aspen Plus is one of standard process
modeling tools for industrial simulation. This
software is equipped with reliable thermodynamic
data, realistic operating conditions and the rigorous
equipment models, so it has capabilities to predict
the actual behavior of a process using basic
engineering relationships such as mass and energy
balances, phase and chemical equilibrium, and
reaction kinetics. The system is also supported by
complete sets of modules, which includes reactive
distillation where both reaction and separation are
assumed to take place in the liquid phase in
column trays or packings. In this work, we used
ASPEN Plus to simulate production of α-terpineol
from α-pinene.
We have succeeded to isolate α-pinene from
Indonesian
turpentine
using
low-pressure
distillation column [2]. Then, the mixture of
613.0667 kg/hr (4.50 mole/hr) with the mole
fraction of α-pinene 0.9709, β-pinene 0.1601,
camphene 0.0128, limonene 0.0004%, introduced
to the middle of reactive distillation column (plate
5) along with 714.3998 kg/hr (7.56 mole/hr) of
chloroacetic acid as catalyst and 1,422.493 kg/hr
(78.96 mole/hr) of water. This capacity is based on
the capacity of one turpentine factory in Indonesia.
We set pressure 1 atm (at the top), 1.2 atm (at the
bottom) and distillate rate at 900.7663 kg/hr. A
twelve plate reactive distillation column including
a total condenser (plate 1) and reboiler (plate 12)
was used for Aspen simulation.
The procedure of simulation on Aspen plus is
as follows:
1. Flow-sheeting of the reactive distillation
process.
2. Defining components involved in hydration
process such as α-pinene, β-pinene, camphene,
carene, limonene, water, chloroacetic acid and
α-terpineol.
3. Property estimation is required for non-data
bank especially for carene and α-terpineol by
inputting their molecular structure. Ideal
property is assumed because there is no
azeotropic mixture.
4. Using mixer and heater for preliminary process
to get the best operational condition.
Choosing RadFrac block for reactive
distillation simulation.
5. Setting operation condition: temperature,
pressure, flowrate and composition for feed
and that’s for catalyst. Specifying plate
number, feed plate position, column pressure
and distillate rate. Specifying reaction kinetic.
6. Running Aspen plus for sensitivity analysis
and characterizing effect of the main
parameters.
Table 3.
Composition of feed, distillate and
bottom
Component
α-pinene
β-pinene
camphene
limonene
carene
chloroacetic acid
water
α-terpineol
Feed
Distillate
Bottom
mole frac
mole frac
mole frac
0.0480
0.0008
0.0006
0.0000
0.0000
0.0831
0.8675
0.0000
6.94E-14
1.11E-07
2.40E-07
2.48E-10
3.63E-18
1.13E-08
0.9999996
1.25E-13
6.00E-04
2.70E-03
2.20E-03
4.08E-05
1.54E-10
0.2835
0.5478
0.1632
A common industrial method of α-terpineol
synthesis consists of hydration of α-pinene with
aqueous mineral to give cis-terpin hydrate,
followed by partially dehydrated into α-terpineol
[9].
(1)
α-pinene
terpene hydrat
α-terpineol
In the previous work, Utami et al (2009) [10]
have developed model of reaction kinetics and
simplify Eq. (1) become:
k1
+ H2O
(2)
k2
α-pinene
α-terpineol
We also assume no side reaction in Eq. (2) and
reaction rate is determined as [11].
– rαp = dCαp/dt = k1CαpCH2O – k2Cαt
(3)
where Cαp, CH2O and Cαt are concentrations of
α-pinene, water and α-terpineol, while k1 and k2 are
chemical rate constants for the forward and reverse
reactions, respectively. For chloroacetic acid,
k1 = 2.632E+10 exp (-9,897.0325/T) and
(4)
k2 = 1,829E+08 exp (-8,383.6804/T)
(5)
Results and Discussion
The composition of feed, distillate and bottom
can be seen at Table 3.
The distribution of liquid mole fraction of
chemical species which involves in hydration
process over the whole column presented on a
water-catalyst-free basis, as shown in Fig. 2. At
(
plates 1 through 5, liquid mole
fraction of
2
α-pinene and α-terpineol look) very small, it
slightly increases from this plate to plate 10
for α-pinene, but it sharply increases for
α-terpineol. For β-pinene, on the other hand, it
slightly increases from top plates 1 to 3, but it
decreases to the bottom plate 10. While for
camphene, it decreases from top plate 1 to
bottom plate 10. These conditions indicate that
effective reaction takes place at the middle of
the column (plaste 5) to the reboiler (plate 12).
Fig. 3 shows the distribution of temperature
and mole fraction of α-terpineol over the whole
column. We may find that the temperature
increase from top plate 1 to the bottom plate. It is
because the far the plate from the heat source
(reboiler), the temperature will be decreased. From
this figure we may see that formation of
α-terpineol starts from plate 3, it increases sharply
from this plate to plate 5, and then it is constant
from this plate to the bottom plate. This shows that
reaction takes place more dominant at stripping
section, while separation process takes place more
dominant at rectifying section.
1. Effect of reflux ratio
Reflux ratio is the ratio of the amount of fluid
returned into the distillation column with a liquid
which is taken as the top product. Inside the
column, the down-flowing reflux liquid provides
cooling and condensation of the up-flowing vapors
thereby increasing the effectiveness of the
distillation column. This reflux can be associated
also with recycle system to promote certain
selectivity in the recycle reactors.
Fig. 4 shows conversion of α-pinene to
α-terpineol at different reflux ratio. From this
figure, we may find that increasing reflux ratio
from R = 1.0 to R = 7.0, results in the sharp
increasing conversion of α-pinene xαp, as well as
increasing reboiler duty. The increasing reflux
ratio further from R = 7.0 to R = 20.0, results in the
slight increasing conversion of α-pinene xαp, but
reboiler duty is increased further. So we may say
that reflux ratio, R = 7.0 is the optimal one.
The liquid which is returned into the
distillation column is increased as the reflux ratio
increased. Consequently, contact between the
vapor and liquid in the distillation column will be
better and the residence time will be longer, so the
conversion obtained by reflux ratio will increased
and reached a maximum value.
With the increasing amount of liquid in the
distillation column, the reboiler duty is also
increased because more liquid present inside the
column requires more amount of heat supplied by
the reboiler. Therefore, if the amount of liquid
which is returned to the column is increased, the
heat provided by the reboiler is also getting higher.
2. Effect of distillate rate
As it described before, when reflux ratio set at
a constant value, the increasing in distillate rate
will increasing the amount of liquid that is returned
to the distillation column.
Fig. 5 shows conversion of α-pinene to
α-terpineol at different distillate rate. From this
figure, we find that increasing the distillate rate
causes the α-pinene conversion increased. In this
reactive distillation column, α-terpineol was taken
as bottom product along with the remaining of
water, catalyst, β-pinene etc. The increasing
amount of fluid returned into the distillation
column resulted in contact between the vapor and
liquid in the distillation column will be better and
residence time will be longer. Consequently,
conversion of α-pinene to α-terpineol will
increased. We may see also in Fig. 5 that
increasing flow rate of distillate, results in the
increasing reboiler duty.
3. Effect of plate number
The increasing of plate number gives effect to
the conversion of α-pinene to α-terpineol, but there
are limits that can be achieved for the highest
conversion. Fig. 6 shows the conversion of
α-pinene to α-terpineol at different plate number.
rate is accompanied by the increase in reboiler
duty.
Acknowledgment
The authors would like to express their
appreciation to KMNRT Indonesia for financial
support of their projet. Our appreciation is also
expressed to WCRU program, Gadjah Mada
University, Dr. Wiratni for the supervisor of their
research.
From this figure we find that increasing of
plate number followed by increasing of α-pinene
conversion, especially for the plate number which
is less than five. This is caused by fact that the
increasing of plate number gives effect to increase
in the reaction zone. But for the plate number
which is more than five, the conversion of
α-pinene to α-terpineol relatively constant. When
the feed rate set constant and the operating
condition were maintained, the distillate and
bottom rate also be relatively fixed, although the
number of plate to be increased. Because of the
increasing of plate number, the amount of liquid
circulating in the reactive distillation column was
relatively fixed, so that the increasing of plate
number doesn’t give any effect to the reboiler duty.
This simulation results conversion of α-pinene
into α-terpineol which is range of above 99%. This
is because the thermodynamic model used in the
simulation is an ideal system. Furthermore, in an
ideal system, all the variables of a process that
occurs ideally calculated. In addition, the value of
reaction rate reported by Utami et al (2009) has no
side reactions, only produce α-terpineol from
α-pinene. Therefore, ASPEN simulates these
reactions using an ideal system that causes
conversion of α-terpineol formation from α-pinene
reaching 99%.
Conclusions
Hydration of α-pinene to α-terpineol can be
synthesized in reactive distillation column. The
optimal reflux ratio is observed in the calculation
where its value at higher than that point conversion
of α-pinene to α-terpineol slight increases.
Increasing flow rate of distillate results in
increasing conversion of α-pinene to α-terpineol.
Increasing plate number gives effect of α-pinene to
α-terpineol, but it doesn’t affect to reboiler duty.
And the increase in the reflux ratio and distillate
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