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RECOVERY OF CAROTENOIDS FROM CRUDE PALM OIL USING ORGANIC
SOLVENT NANOFILTRATION
KHAIRILANUAR BIN MOHD HANIM
A thesis submitted in fulfilment of the requirements
for the award of the degree of Master of Engineering
(Bioprocess)
Faculty of Chemical Engineering
Universiti Teknologi Malaysia
JUNE 2014
iii
To my beloved family and friends
iv
ACKNOWLEDGEMENTS
First and foremost I would like to thank Allah S.W.T for giving me the
strength, and courage to conduct this study. The knowledge I have gained
throughout this work and all my life is all because of His blessing. Alhamdulillah.
I would like to express my deepest appreciation to my supervisor, Dr. Mohd
Nazlee Faisal Ghazali for his guidance, advices, and dedication throughout the
research. It was his kind support that helped me complete this study successfully. I
am also grateful towards my colleague, Qadly Ameen Pahlawi for his unconditional
support and assistance for me towards the success of this research. Also I am grateful
to all the staff of Faculty of Chemical Engineering, Universiti Teknologi Malaysia
(UTM) for their support that made this research a success.
Last but not least, I would like to thank my beloved family members for their
love and moral support throughout every endeavor of mine.
v
ABSTRACT
The recovery of carotene from crude palm oil prior to refining would add
significant value to the country’s palm oil industry. Various methods are currently
available to yield high concentrations of carotene. These methods however, have
many disadvantages when factors such as cost, and energy consumption are weighed
into consideration. This work presents the application of organic solvent
nanofiltration membranes for the separation of carotene from a crude palm oil
(CPO)/solvent system. Filtration tests were conducted using a dead-end filtration
set-up, utilizing four different polyimide membranes and four different solvents.
PuraMem™ 280 showed the best performance, with a selectivity of 1.25 when
hexane was used as the solvent. Runs using DuraMem™ 150, DuraMem™ 300 and
DuraMem™ 500 showed low or no selectivity between carotene and triglyceride in
all solvents. It was found that rejection of carotene depends strongly on the type of
solvents and membrane type and therefore is critical for carotene separation. Lower
applied pressure and low feed concentrations improved the membrane selectivity.
The effect of solute-solvent coupling was much higher towards lower molecular
weight component (carotene) and at lower pressures. Theoretical pore size of the
membrane was predicted using sets of equations relating the diffusivity of the solutes
and the experimental rejection results. Results showed that the theoretical pore size
of membrane PuraMem™ 280 was between 1.38 nm to 1.85 nm. The effect of
concentration polarisation was predicted, and result showed that in this system, the
effect of concentration polarization was very minimal, where cw/cb was only between
1.06 to 1.24. Generally, high feed concentrations increased the feed viscosity,
resulting in significant osmotic pressures and reduces the permeate flux.
vi
ABSTRAK
Pemisahan karotena daripada minyak sawit mentah sebelum proses penapisan
memberi nilai tambah kepada industri minyak sawit negara. Pada masa ini, terdapat
pelbagai kaedah yang berupaya menghasilkan karotena dalam kepekatan tinggi.
Walau bagaimanapun, kaedah-kaedah tersebut mempunyai banyak kelemahan
apabila faktor seperti kos dan penggunaan tenaga diambilkira. Kajian ini
membentangkan aplikasi membran nanopenurasan pelarut organik untuk pemisahan
karotena daripada sistem minyak sawit mentah/pelarut organik. Ujian penurasan
dijalankan dengan susunan penurasan buntu, menggunakan empat membran
poliimida dan empat pelarut berlainan. PuraMem™ 280 menunjukkan prestasi
terbaik dengan nilai pemilihan 1.25 apabila digunakan bersama pelarut heksana.
Membran DuraMem™ 150, DuraMem™ 300 and DuraMem™ 500 menunjukkan
nilai pemilihan yang rendah antara karotena dan trigliserida dalam semua pelarut.
Kajian mendapati, kadar penolakan karotena sangat bergantung kepada jenis pelarut
dan jenis membran oleh itu sangat kritikal dalam pemisahan karotena. Tekanan yang
rendah dan kepekatan suapan yang rendah meningkatkan pemilihan membran
tersebut. Kesan gandingan antara bahan larut dan pelarut lebih tinggi terhadap
komponen yang mempunyai berat molekul lebih ringan (karotena) dan pada tekanan
yang lebih rendah. Saiz liang membran teori boleh diramalkan menggunakan
beberapa set persamaan yang mengaitkan kebolehresapan bahan larut dengan
penolakan yang didapati dari eksperimen. Keputusan menunjukkan bahawa saiz
liang membran teori adalah di antara 1.38 nm hingga 1.85 nm. Kesan kekutuban
kepekatan telah diramalkan, dan keputusan menunjukkan kesan tersebut adalah
minimum, di mana cw/cb adalah antara 1.06 hingga 1.24. Secara umumnya,
kepekatan suapan yang tinggi meningkatkan kelikatan, seterusnya meningkatkan
tekanan osmotik, dan merendahkan fluks.
vii
TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENTS iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES xi
LIST OF FIGURES xii
LIST OF ABBREVIATIONS xiv
LIST OF APPENDICES xv
1 INTRODUCTION 1
1.1 Research Background 1
1.2 Problem Statement 3
1.3 Research Objectives 3
1.4 Scope of Study 4
1.5 Significance of Research 5
2 LITERATURE REVIEW 6
2.1 Crude Palm Oil 6
2.2 Composition and Constituent of CPO 7
viii
2.2.1 Triglycerides 8
2.2.2 Carotenoids 10
2.3 Current Technology on Carotene Recovery from CPO 13
2.3.1 Solvent Extraction 14
2.3.2 Adsorption 15
2.3.3 Molecular Distillation 15
2.4 Organic Solvent Nanofiltration (OSN) Membranes 16
2.4.1 Introduction to OSN 16
2.4.2 OSN Membrane Market 17
2.4.3 Applications of OSN 18
2.4.3.1 Solvent recovery 18
2.4.3.2 Recovery of homogenous catalysts 19
2.4.3.3 Natural products recovery 20
2.4.3.4 Purification of pharmaceuticals 21
2.4.3.5 Oil and petrochemicals 22
2.4.4 Membrane Polymer 23
2.4.4.1 Polyimide 23
2.4.4.2 Polydimethylsiloxane 24
2.5 Transport Mechanism through OSN membranes 26
2.5.1 Solution diffusion 26
2.5.2 Pore flow 30
2.6 Effects of experimental conditions on OSN membrane
performance 32
2.6.1 Membrane material and nature of solute 32
2.6.2 Type of Solvent 34
2.6.3 Feed Concentration 34
2.6.4 Transmembrane Pressure 35
2.6.5 Temperature 35
ix
2.7 Transport Phenomena Affecting Membrane
Performance 36
2.7.1 Concentration Polarization 36
2.7.2 Compaction 40
2.8 Effective Solute Diameter and Diffusivity 41
3 METHODOLOGY 43
3.1 Raw Materials 43
3.2 Membrane System 44
3.3 Membrane Performance Parameters 47
3.4 Flux of Pure Solvents through Membrane 48
3.5 Membrane Screening 49
3.6 Effects of Different Operating Parameters towards
Membrane Performance 50
3.7 Analysis 51
3.8 Estimation of Solute Size and Theoretical Pore Size 52
3.9 Investigation on Effects of Concentration Polarization 53
4 RESULTS AND DISCUSSION 54
4.1 Flux of Pure Solvents through the Membranes 54
4.2 Membrane Performance Screening 59
4.3 Effects of feed concentration towards flux and
selectivity 66
4.4 Effects of Operating Pressure Towards Flux and
Selectivity 68
4.5 Filtration Tests using Model Solutions of Carotene in
Hexane 72
4.6 Filtration Tests using Model Solutions of Triglyceride
in Hexane 74
x
4.7 Estimation of Solute Diameter, and Membrane Pore
Size using Wilke Chang and Stokes Einstein Equation 75
4.8 Investigation on the Effects of Concentration
Polarization and Osmotic Pressure Towards the
Membrane Performance 79
5 CONCLUSIONS AND RECOMMENDATIONS 83
5.1 Conclusions 83
5.2 Recommendations 85
REFERENCES 86
Appendices A - C 93 - 107
xi
LIST OF TABLES
TABLE NO. TITLE PAGE
2.1 Minor components of crude palm oil (Gee, 2007) 13
3.1 Characteristics of the crude palm oil obtained from local
palm oil refinery 44
3.2 Properties of the membranes as used in the study 46
3.3 Properties of various solvents used in the study 49
3.4 HPLC analysis method for detecting triglycerides 52
4.1 Final permeate flux of various solvents through membranea 56
4.2 Solubility parameters of solvents and polyimide. 58
4.3 Final permeate flux for filtration of different CPO-solvent
solutions through the different membranesa 61
4.4 Summary of results for membrane screening experiments 62
4.5 Solubility of carotene in solvents used in the experiment 65
4.6 Values of variables and constants required for Wilke-
Chang equation for determining carotene solute diffusivity. 76
4.7 Calculated values of solute parameters of carotene and
triglyceride. 77
4.8 Calculated osmotic pressures influenced by carotene
concentrations 82
4.9 Calculated osmotic pressures influenced by triglyceride
concentrations 82
xii
LIST OF FIGURES
FIGURE NO. TITLE PAGE
2.1 General structure of triglyceride 9
2.2 Chemical structure of a) α-carotene, and b) β-Carotene
present in the crude palm oil 11
2.3 Molecular structure of polyimides (Hatori et al., 1995) 23
2.4 Basic chemical structure of polydimethylsiloxane (PDMS) 25
2.5 Concentration gradient through membranes (Wijmans and
Baker, 1995) 27
2.6 The transportation mechanism of mixtures based on the pore
flow model 30
2.7 Concentration polarization in nanofiltration and reverse
osmosis solutions 38
3.1 Diagram of the filtration apparatus 45
4.1 Flux profile of pure solvents through the membranes studied 55
4.2 Flux profile of CPO-solvent systems through the
membranes studied 60
4.3 Influence of CPO/hexane feed concentration towards the
viscosity and the permeate flux through PuraMem™ 280 66
4.4 Effects of feed concentration towards RC, RTG, and
selectivity of in CPO-hexane mixture through PuraMem™
280 67
4.5 Effects of pressure towards flux of pure hexane and CPO-
hexane mixture through PuraMem™ 280 69
4.6 Effects of pressure on RC, RTG, and separation factor of
CPO-hexane mixture through P280 71
4.7 Effect of concentration of carotene-hexane solution towards
flux and rejection 72
4.8 Effect of concentration of triglyceride-hexane solution
towards flux and rejection 74
xiii
4.9 Effect of feed concentration towards the observed rejection,
Robs, real rejection, Rreal, and concentration polarization effect,
cw/cb 80
xiv
LIST OF ABBREVIATIONS
CPO - Crude Palm Oil
MW - Molecular weight
MWCO - Molecular weight cut-off
TG - Triglycerides
MG - Monoglycerides
DG - Diglycerides
FFA - Free fatty acids
POME - Palm oil mill effluent
Da - Dalton
RSM - Response surface
methodology
HPLC - High performance liquid
chromatography
RO - Reverse osmosis
RPME - Red palm methyl esters
CPME - Continuous electrophoresis
with porous membranes
PAN - Polyacrylonitrile
PI - Polyimide
PDMS - Polydimethysiloxane
CHAPTER 1
INTRODUCTION
1.1 Research Background
Palm oil is one of the world's richest natural plant sources of carotenoids.
The minor components of crude palm oil (CPO) consist of carotenoids, tocopherols,
tocotrienols, vitamin E and sterols. It contains high concentration of carotenes of
about 0.5-0.7 g/L, 15 times more retinol equivalents (vitamin A) than carrots and 300
times more than tomatoes(Sundram e? 2003). The primary carotenes that exists
in palm oil are a-carotene and P-carotene, which account for 80% of the total
carotenes (Ooi e? %A, 1994). The importance of P-carotene is well documented for
human nutrition and serves as a major source of vitamin A, as they can be
transformed into vitamin A m vz'w (Chuang and Brunner, 2006) and serves as a
potential alternative means of fighting vitamin A deficiency which is prevalent in
many countries (Barison, 1996). Numerous studies have shown that carotenes can
prevent certain types of cancer, such as lung, oral, pharyngeal and stomach cancers
(Peto e? %A, 1981). It could also enhance the immune system and help to protect
against flu, colds, infections, and toxins. Furthermore, carotenoids are strong dyes,
in which at even very low levels of parts per million, they are able to impart the
desired properties to foods (Gordon and Bouernfeind, 1982). Due to broad
application of natural compounds in cosmetics, pharmaceuticals and food industry,
carotenoids have increased in its value and importance. Therefore, their recovery
from palm oil or its by-products are very important.
The nation's palm oil industry would benefit significantly from the process of
extraction and recovery of carotenes from palm oil. But unfortunately, conventional
physical and chemical methods of palm oil refining causes almost all of the carotenes
to be either removed or destroyed (Ooi e? 1994). This process also helps to give
the light colored oil as favoured by consumers. A few processes have been
developed to recover carotenes from palm oil which includes solvent extraction
(Tanaka, 1986), molecular distillation, and adsorption (Ong and Boey, 1980). These
technologies however require high capital expenditure to set up and have significant
operating costs due to vast energy consumption.
Nanofiltration offers a good alternative for the process of separating carotene
from crude palm oil due to its lower energy consumption, ambient temperature
operation, and retention of thermally sensitive compounds. Recently, organic
solvent nanofiltration (OSN) has found numerous applications including
homogeneous catalyst recovery, solvent exchange, chiral separation, concentration of
natural extracts, and peptide synthesis. There are a few reports on the membrane
process of recovering carotenoids from palm oils, in which the oil was first
transesterified into methyl esters, then the carotenes are separated from the methyl
esters through nanofiltration (Chiu e? %A, 2009; Darnoko and Cheryan, 2006). The
disadvantage of this process is that the edible oil is lost or rendered useless for
further consumption. Thus there is a need to find a membrane filtration process to
recover the carotenoids from crude palm oil prior to refining without chemical
transformation of the triglycerides.
2
3
1.2 Problem Statement
During conventional physical and chemical methods of palm oil refining,
almost all of the carotenes are removed and destroyed. It is proposed that prior to
chemical or physical refining of the crude palm oil, the carotenoids are first
recovered by adding an extra step of membrane filtration in the process. There are
various methods being applied to recover carotene from crude palm oil, and intensive
studies have been done on the extraction and recovery of carotene. These methods
include saponification, selective solvent extraction, and transesterification followed
by both phase separation and distillation of the ester. The process of
transesterification can produce high concentrations of carotene however, has many
disadvantages after weighing in factors such as cost, materials, and the large amount
of energy required for evaporation. Converting the palm oil into methyl esters also
renders the oil useless for further usage and consumption. Organic solvent
nanofiltration can address these problems whereby the separation of carotene from
crude palm oil is based on different molecular size, lowering energy consumption,
minimizing thermal damage and without involving any phase change,. Moreover,
the separation maintains the oil quality where the oil is not transformed to methyl
esters while increasing yield through gentle ambient temperature separations.
1.3 Research Objectives
The main objective of this study is to explore the potential of OSN process to
separate carotene from palm oil. In this present work, the performances of various
OSN membranes will be evaluated for the permeation of carotene and retention of
triglycerides. The best membrane in terms of flux and selectivity will be further
studied on the effects of operating parameters such as pressure and feed
concentration towards selectivity of carotene. The specific research objectives are as
follows:
1. To identify the best combination of membrane and solvent for the
separation of carotene from crude palm oil.
2. To evaluate the effects of varying operating parameters towards the flux
and selectivity using the best combination of membrane and solvent.
3. To study the transport phenomenon involved in the OSN membrane
separation of carotene and triglyceride using model solutions.
4
1.4 Scope of Study
In order to achieve the specified objectives, the study involves investigating
the performance of OSN membrane in the recovery of carotene from crude palm oil
directly without chemical transformation of the triglycerides. Performance was
based on the flux (J), rejection (R) and selectivity ( <x) between carotene and
triglycerides (palm oil). The process will use 4 different polyimide membrane
materials with different molecular weight cut-off (MWCO) as described by the
manufacturer. The membranes are PuraMem™ 280, DuraMem™ 150, DuraMem™
300, and DuraMem™ 500. The effect of using different types of solvents namely
acetone, hexane, ethyl acetate, and isopropanol towards flux and rejection will be
studied. The effects of varying operating parameters namely; palm oil feed
concentration, and pressure, and towards flux and selectivity will be studied. The
rejection characteristics of the selected membrane will then be tested using model
solution of carotene in solvent, and triglyceride in solvent. Based on the
experimental data, the solute diameters and theoretical pore size of the selected
membrane will be predicted using Stokes-Einstein equation. The implications of
concentration polarization, osmotic pressure, membrane swelling, and solubility
parameters in the membrane system will be investigated.
5
1.5 Significance of Research
This study will help to improve our understanding on the potential of OSN
membranes towards specific applications in the processing of crude palm oil. This
research will add significant advantages to the palm oil industry especially in the
processing of crude palm oil since the findings will help to add value to the final
product.
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