Steam extraction of essential oils

159 Pages·2012·1.54 MB·English

by  Kabuba, John Tshilenge.

UNIVERSITY OF JOHANNESBURG
r.;
JOHANNESBLRG
STEAM EXTRACTION OF ESSENTIAL OILS:
INVESTIGATION OF PROCESS PARAMETERS
By
JOHN TSHILENGE KABIJBA
A DISSERTATION SUBMITTED TO THE DEPARTMENT OF
CHEMICAL ENGINEERING TECHNOLOGY
UNIVERSITY OF JOHANNESBURG, SOUTH AFRICAf
FOR THE FULFILLMENT OF THE DEGREE OF
MAGISTER TECHNOLOGIAE: CHEMICAL ENGINEERING
TECHNOLOGY
Supervisor: Dr. R HUBERTS
February 2009
Declaration by candidate
I hereby declare that this dissertation is my own, unaided work. It is being submitted for the
Degree of Master of Technology in Chemical Engineering Technology at The University of
Johannesburg. It has not been submitted before for any degree or examination in any other
University. I further declare that all sources cited or quoted are indicated and acknowledged by
means of a comprehensive list of references.
John T. Kabuba
(cid:9) day of February 2009
c
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Dedication
I dedicate this dissertation to my Father Tshilenge Kalonji Elias who
encouraged me enormously.
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Abstract
Essential oils are volatile oils, generally odorous, which occur in certain plants or specified parts
of plants, and are recovered by accepted procedures, such that the nature and composition of the
product is, as nearly as practicable, unchanged by such procedures (ISO, 1968). The principal
uses are as: flavouring agent, medicinal and aromatherapy application. Today, the essential oils
are sought-after for innumerable applications starting from markers for plant identifications to
bases for semi-synthesis of highly complex molecules. The extraction of highly delicate essential
oils from plants remains a crucial step in all these applications. By using steam to mediate the
extraction, it is possible to maintain mild conditions and effect superior extraction.
In the current work, an integrated procedure for steam extraction followed by volatiles sampling
and analysis from the leaves of the Eucalyptus tree was explored. There are two problems to
overcome in the extraction from solid plant materials: that of releasing the essential oils from
solid matrix and letting it diffuse out successfully in a manner that can be scaled-up to industrial
volumes. Towards this end, the effect of different parameters, such as temperature, pressure and
extraction time on the extraction yield was investigated and the experimental results show that all
of these temperatures (90°C, 97°C, and 99°C), were significant parameters affecting yield.
Increase in yield was observed as pressure was increased and the use of high pressure (150 kPa)
in steam extraction units permits much more rapid and complete distillation of essential oils over
atmospheric pressure. The yield was calculated from the relation between the essential oil mass
extracted and the raw material mass used in the extraction. The volatiles, Eucalyptus oil in
vapour form released from the leaves were condensed and analyzed using Gas chromatography,
and eight major components were found to be contained in this species.
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A mathematical model based on diffusion of essential oil from the leaves was developed. Using a
numerical method, the best diffusion coefficient was established for different operating
conditions by comparing the model concentration of oil remaining in the leaves with the
experimental amount of oil recovered; hence minimizing the sum of squared errors. It was found
that one can not simply assume that the oil leached and recovered was the same as that originally
present in the leaves. The initial mass of oil was determined by fitting the diffusion model to the
data.
An Arrhenius model was used to account for the effect of temperature. The resulting expression
for the diffusion coefficient as a function of temperature can now be used to model the large
scale extraction of the essential oils from Eucalyptus leaves.
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Acknowledgements
I wish to thank my supervisor Doctor R Huberts, for his guidance and advices. His enthusiasm
for research proved to be very valuable in assisting me in this endeavour. I appreciate very much
the input from the promoter, Mr. Mansoor Mollagee, despite his activities as Head of
Department.
I thank Professor B. Botha for the steam extraction unit of the complete experimental setup. I
wish to thank Mr. Aaron Martinus for many suggestions for improvement in the experiments.
Dr. Bulaje, Dr. Mazana and Dr. Njapha were the source of inspiration and enthusiasm and a
moral support owing to a refreshingly positive attitude.
I thank Prof. Krause for his support in GC analysis.
I am indebted to the University Research Committee and the National Research Foundation for
funding this work. Without money we can do nothing, there I am very grateful to the Department
of Chemical Engineering Technology, University of Johannesburg for providing me with the
opportunity to earn the necessary for my living throughout a part-time lectureship position.
I need to thank particularly Dr. Lizelle Van Dyk, Mr. Germain Mbuyu and all the colleagues
from The Chemical Engineering Department, for their encouragements and sharing the hardship
we went through during our studies.
Finally, I want to express special thanks to my parents, for their constant support and
understanding, to my family and wife Cathy Ntumba for their support and limitless
encouragement to further studies.
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Table of contents
Declaration (cid:9) .i
Dedication (cid:9) ii
Abstract (cid:9) .iii
Acknowledgements (cid:9) iv
Table of contents (cid:9) v
List of figures (cid:9) ..vi
List of tables (cid:9) ..vii
Nomenclature (cid:9) viii
Chapter 1: Introduction (cid:9) 15
1.1 Background of essential oils, rationale and motivation (cid:9) 15
1.2 Aims and Objectives (cid:9) 16
1.3 Format of the study (cid:9) 17
Chapter 2: Literature review (cid:9) 19
2.1 History of Essential Oils (cid:9) 19
2.1.1 General history (cid:9) 19
2.1.2 History of Eucalyptus Essential Oils (cid:9) 20
2.2 The uniqueness of Essential Oils (cid:9) 22
2.3 Uses of Essential oils (cid:9) 24
2.3.1. Fragrant uses (cid:9) 25
2.3.2. Medicinal uses (cid:9) 27
2.4 Methods of production (cid:9) 28
2.5 Important Physical and Chemical properties of Essential Oils (cid:9) 35
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2.6 Factors affecting the yield and quality of the Essential Oils (cid:9) 40
Chapter 3: Principles of Steam Extraction of Essential Oils (cid:9) 42
3.1 Preamble (cid:9) 42
3.2 Components of the Extraction Plant (cid:9) 43
3.3 Basic scientific principles involved in the process (cid:9) 47
3.4 Techniques of Extraction (cid:9) 48
Chapter 4: Experiments (cid:9) 52
4.1 Introduction (cid:9) 52
4.2 Materials and methods (cid:9) 52
4.1.1 Collection of the plant material (cid:9) 52
4.2.2 Treatment of the plant material (cid:9) 53
4.3 General description of equipment and procedure (cid:9) 54
4.3.1 Experimental and equipment description (cid:9) 54
4.3.2 Hazop analyses of the experimental equipment and procedure (cid:9) 56
4.4 Condensate isolation and characterization of the oils extracts (cid:9) 60
4.4.1 Isolation of the oil extracts from the steam condensation (cid:9) 60
4.4.2 Quantitative characterization of the Eucalyptus Essential Oils extracts (cid:9) 61
4.4.3 Qualitative characterization of the Eucalyptus Essential Oil extracts (cid:9) 62
4.5 Conclusion (cid:9) 68
Chapter 5: Results and Discussions (cid:9) 69
5.1 Introduction (cid:9) 69
5.2 The quantitative analyses of the oil extracts (cid:9) 70
5.3 The qualitative analyses of the oil extracts (cid:9) 72
5.4 The mathematical modelling of the oil extraction process (cid:9) 73
5.5 Concluding remarks (cid:9) 90
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Chapter 6: Conclusions and Recommendations (cid:9) 91
6.1 Achievement of objectives (cid:9) 91
6.2 Contribution of the study (cid:9) 92
6.3 Critical evaluation of the study (cid:9) 92
6.4 Recommendations for further research (cid:9) 93
References (cid:9) 94
Appendix A: Experimental run data analyses (cid:9) 99
A.1 Quantitative analysis results (cid:9) 99
A.2 Qualitative analysis results (cid:9) 100
Appendix B: Modelling results and analyses (cid:9) 108
Fitting the Theoretical oil extraction model using the best fit D value (cid:9) 108
Refining Mo, Do and Ea to ensure minimum SSE (cid:9) 112
Appendix C: Typical chromatograms for the Eucalyptus oil extract (cid:9) 158
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List of figures
Figure Page No:
4.1 Eucalyptus leaves (cid:9) 53
4.2 Schematic representation of the steam extraction equipment (cid:9) 54
4.3 Schematic representation of the separating funnel (cid:9) (cid:9) 60
4.4 Schematic diagram of gas chromatograph (cid:9) (cid:9) 62
4.5 The Flame Ionisation Detector (cid:9) 64
4.6 The Split/ Splitless injector (cid:9) 65
5.1 Cumulative mass of oil extracts (cid:9) 70
5.2 Yield curve of Eucalyptus essential oil (cid:9) (cid:9) .71
5.3 Schematic representation of diffusion in the leaf (cid:9) (cid:9) 74
5.4 Schematic diagram of modelling steps (cid:9) 77
5.5 Determination of required segment number and delta at 99 °C for use in the
spreadsheet (cid:9) 78
5.6 Fitting the Theoretical oil extraction model using the best fit D value to 90 °C
experiential data (cid:9) 79
5.7 Fitting the Theoretical oil extraction model using the best fit D value to 97 °C
experiential data (cid:9) (cid:9) .80
5.8 Fitting the Theoretical oil extraction model using the best fit D value to 99 °C
experiential data (cid:9) .80
5.9 Determination of the activate energy: In D versus 1/T (cid:9) 82
5.10 Fitting the Theoretical oil extraction model using calculated D values using
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