Simulation Study on Production of -Terpineol from -Pinene Isolated from Turpentine from Indonesia Using Reactive Distillation Column

1Tya Indah Arifta*, 2Sutijan, and 3Arief Budiman

123Chemical 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 -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 -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 -pinene to -terpineol. Key words: -pinene hydration, -terpineol, reactive distillation, aspen plus

Introduction Turpentine is one of the essential oils obtained from pine trees. Highly purified -pinene that has to reach 97% purity can be obtained by vacuum-fractional distillation of turpentine [2]. When treated with water in the presence of acid catalyst, -pinene is hydrated to complex mixtures of monoterpenes, alcohol and hydrocarbons, although -terpineol predominates. -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 -pinene by homogeneous acid catalysts yielding -terpineol has been studied since the 1930s, when Charlton and Day (1937) studied the hydration of -pinene using sulfuric acid at low temperature [3]. Then, Williams and Whittaker (1971) investigated the rearrangements of acid-catalyzed hydration of -pinene in aqueous and anhydrous acetic acids [13]. Pakdel et al (2001) studied hydration of crude turpentine oil which contains 52% -pinene and used sulfuric acid as catalyst in the presence of acetone. They reported the main hydration product, -terpineol, was obtained at a yield of 77.2%

(based o the quantity of -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 -terpineol 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 -pinene to terpineol using water as the hydroxyl group donor. Chloroacetic acid was found as good catalyst for the production of -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 -terpineol plant is designed with two main equipment. Hydration reactor to produce terpene hydrate and then following de-hydration in distillation column to produce perfumery -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 -pinene solution, which is distilled from the Indonesian turpentine as feed and Table 2 shows physic-chemical properties of chemical species in the -pinene hydration process. Table 1. Composition of -pinene solution

Component Composition (mass fract) -pinene 0.9709 -pinene 0.0160

camphene 0.0128 limonene 0.0002

carene 1.10E-09 Table 2. Normal boiling points of chemical

species in the -pinene hydration

Chemical Name Chemical Formula Mw TB

(g/mol) (K)

-pinene C10H16 136.24 429.29 -pinene C10H16 136.24 439.19

camphene C10H16 136.24 433.65 limonene C10H16 136.24 450.6

carene C10H16 136.24 491.9 chloroacetic acid C2H3ClO2 94.5 462.5

water H2O 18.02 373.15 -terpineol C10H18O 154.25 540.84

We react -pinene 97% and water with chloroacetic acid as catalyst. Chloroacetic acid was found as good catalyst for the production of -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 -terpineol from -pinene. We have succeeded to isolate -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 -pinene 0.9709, -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 -pinene, -pinene, camphene, carene, limonene, water, chloroacetic acid and -terpineol.

3. Property estimation is required for non-data bank especially for carene and -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 thats 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.

A common industrial method of -terpineol synthesis consists of hydration of -pinene with aqueous mineral to give cis-terpin hydrate, followed by partially dehydrated into -terpineol [9]. In the previous work, Utami et al (2009) [10] have developed model of reaction kinetics and simplify Eq. (1) become:

(2)

We also assume no side reaction in Eq. (2) and reaction rate is determined as [11]. rp = dCp/dt = k1CpCH2O k2Ct (3) where Cp, CH2O and Ct are concentrations of -pinene, water and -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.

Table 3. Composition of feed, distillate and bottom

Component Feed Distillate Bottom

mole frac mole frac mole frac -pinene 0.0480 6.94E-14 6.00E-04 -pinene 0.0008 1.11E-07 2.70E-03

camphene 0.0006 2.40E-07 2.20E-03 limonene 0.0000 2.48E-10 4.08E-05

carene 0.0000 3.63E-18 1.54E-10 chloroacetic acid 0.0831 1.13E-08 0.2835

water 0.8675 0.9999996 0.5478 -terpineol 0.0000 1.25E-13 0.1632

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 -pinene and -terpineol look very small, it slightly increases from this plate to plate 10 for -pinene, but it sharply increases for -terpineol. For -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).

-pinene terpene hydrat -terpineol

(1)

-pinene -terpineol

+ H2O k1

k2 (2)

Fig. 3 shows the distribution of temperature and mole fraction of -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 -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 -pinene to -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 -pinene xp, 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 -pinene xp, 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 -pinene to -terpineol at different distillate rate. From this figure, we find that increasing the distillate rate causes the -pinene conversion increased. In this reactive distillation column, -terpineol was taken as bottom product along with the remaining of water, catalyst, -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 -pinene to -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 -pinene to -terpineol, but there are limits that can be achieved for the highest conversion. Fig. 6 shows the conversion of -pinene to -terpineol at different plate number.

From this figure we find that increasing of plate number followed by increasing of -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 -pinene to -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 doesnt give any effect to the reboiler duty.

This simulation results conversion of -pinene into -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 -terpineol from -pinene. Therefore, ASPEN simulates these reactions using an ideal system that causes conversion of -terpineol formation from -pinene reaching 99%. Conclusions Hydration of -pinene to -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 -pinene to -terpineol slight increases. Increasing flow rate of distillate results in increasing conversion of -pinene to -terpineol. Increasing plate number gives effect of -pinene to -terpineol, but it doesnt affect to reboiler duty. And the increase in the reflux ratio and distillate

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. References 1) Arctander, S., 2000, Perfume and Flavor

Chemicals; Vols. 1 and 2, Allured Publishing. 2) Budiman, A., Sutijan, Umul, K., and Risal, R.,

2006, Separation Performance of Reactive Distillation Column: Case study in Methyl Tertier Butyl Eter (Indonesia), National Conference of Indonesias Chemical Engineers 2006, UGM-Yogyakarta, Indonesia.

3) Charlton, R.W. and Day, A.R., Ind Eng Chem, 29, 1, 92-95, 1937.

4) Fuerstenau, D.W. and Pradip, 1982, Adsorption of Frothers at Coal/Water Interface, Colloids Surf, 4 (3), 213-227.

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6) Pakdel, H., Sarron, S., and Roy, C., J Agric Food Chem, 49, 4337-4341, 2001.

7) Pitarokili, D., Couladis, M., Panayoutaru, N.P., and Tzakou, O., J.Agric. Food Chem, 50, 6688-6691, 2002.

8) Roman-Aguirre, M., Torre-Saenz, L.D., Flores, W.A., Robau-Sanchez, A., and Elguezabal, A.A., Catal Today, 107-108, 310-314, 2005.

9) Surburg, H. and Panten, J., 2006, Common fragrance and flavor materials, 5th. Ed., Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

10) Utami, H., Sediawan, B.S., Budiman, A., Sutijan, and Roto, Regional Symposium on Chemical Engineering, RSCE, Manila, Philippines, December 2009, 2009.

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