UNIVERSITI PUTRA MALAYSIA

SHANTI FARIDAH SALLEH

FK 2012 2

HYDROLYSIS OF OIL PALM EMPTY FRUIT BUNCH USING DILUTE ACID

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HYDROLYSIS OF OIL PALM EMPTY FRUIT BUNCH USING DILUTE ACID

By

SHANTI FARIDAH SALLEH

Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, In Fulfilment of the Requirements for the Degree of Doctor of Philosophy

December 2012

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DEDICATED TO

MY BELOVED CHILDREN, HUSBAND AND PARENTS

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Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfillment of the requirement for the degree of Doctor of Philosophy

HYDROLYSIS OF OIL PALM EMPTY FRUIT BUNCH USING DILUTE ACID

By

SHANTI FARIDAH BINTI SALLEH

December 2011

Chairman: Professor Robiah Yunus, PhD

Faculty: Engineering

Extensive research activities have been carried out to identify the best technology to

convert biomass to bioethanol and other value added chemicals. This research

focuses on the conversion of the hemicelluloses in the Oil Palm Empty Fruit Bunch

(OPEFB) fibre to xylose via an acid hydrolysis reaction. The objectives of this study

are to investigate a potential pre-treatment method prior to acid hydrolysis, to

optimise the reaction conditions and operation modes of the reactor as well as to

study the kinetics of the acid hydrolysis of OPEFB fibre in a batch reactor.

A preliminary assessment on the composition of the OPEFB fibre was conducted

using TGA analysis and the following composition of the fibre (% dry weight basis)

was obtained: cellulose, 44.5%; hemicellulose 26.5%; lignin, 19.1%. Since OPEFB

contains more than 70% cellulose and hemicelluloses in its fibre, it is an excellent

feed sock of fermentable sugars for bioethanol production. However, the cellulose

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and hemicelluloses in the fibre must firstly be converted to fermentable sugars

namely glucose and xylose. Consequently, a 1-litre batch reactor was fabricated and

commissioned to convert lignocellulosic materials in the fibre to either glucose or

xylose. The maximum temperature of the batch reactor was 140 oC, while the liquid

solid ratio was between 20:1 and 30:1. In the preliminary screening of the best acid,

three different types of acid were employed; sulphuric acid (H2SO4), hydrochloric

acid (HCl) and acetic acid (CH3COOH). The catalyst-screening study was

conducted at 100oC and at a liquid solid ratio of 25:1. Sulphuric acid showed the

highest catalytic effect, followed by hydrochloric acid and acetic acid. Sulphuric

acid was selected and applied for subsequent studies.

The effect of ultrasonic pretreatment on dilute acid hydrolysis of OPEFB was also

examined. The experiments were conducted at two temperatures; 100oC and 140oC.

The results showed that the exposure of the OPEFB fibre to 20 kHz signal of

ultrasonication power at different amplitudes had a marked effect on the efficiency

of low temperature (100oC) acid hydrolysis based on the yield of xylose. However,

no improvement on yield of xylose was observed for acid hydrolysis at 140oC. SEM

analysis showed that OPEFB fibre undergone significant morphological changes due

to the effect of ultrasonic pretreatment under different acid hydrolysis conditions.

Optimisation studies were conducted under various conditions; temperatures (80 oC

to 140 oC), acid concentrations (2%, 4% and 6%), and reaction times (15 min, 30

min, 60 min, 90 min, 120 min and 150 min). The results indicated that the effect of

acid concentration on the conversion of xylose was significant at higher temperature.

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At temperatures higher than 120oC, acid hydrolysis of OPEFB fibre favoured lower

acid concentration and longer reaction time (more than 60 minutes). At lower

temperatures (below 120oC), higher acid concentration and shorter reaction time

(less than 60 minutes) improved xylose production. The monomeric xylose present

in the liquid phase is the key indicator of the extent of the reaction, thus it was used

as the basis for the kinetics modelling analysis.

Kinetics study on the dilute acid hydrolysis of OPEFB fibre revealed that the

hydrolysis reaction is a first order irreversible reaction. Dilute acid hydrolysis

reaction was analysed using kinetics models developed by Saeman. Kinetics

constants for Saeman model were analysed using Arrhenius type expansion which

includes activation energy and catalyst concentration factors. A general kinetics

model for acid hydrolysis of OPEFB fibre in terms of acid concentration and

temperature was then developed.

This work highlighted the potential of OPEFB fibre as a feasible feed stock for

production of fermentable sugars especially xylose for bioethanol production. This

work also demonstrated the ability of the in-house batch reactor to convert OPEFB

fibre to xylose with 80% conversion. The breakthrough of this research was the

discovery of the ability of ultrasonic pretreatment to physically alter the surface of

OPEFB fibre, hence increase the yield of xylose. Ultrasonication of biomass has the

potential to be integrated with existing lignocelluloses pretreatment technologies in

biomass to bioethanol production to enhance the overall conversion efficiency.

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Abstrak tesis ini dibentangkan kepada Senat Universiti Putra Malaysia untuk memenuhi keperluan Sarjana Doktor Falsafah

HIDROLISIS ASID TANDAN KOSONG KELAPA SAWIT DALAM REAKTOR LONGGOK

Oleh

SHANTI FARIDAH BINTI SALLEH

Disember 2011

Pengerusi: Profesor Robiah Yunus, PhD

Fakulti : Kejuruteraan

Aktiviti penyelidikan secara meluas telah dijalankan untuk mengenalpasti pertukaran

jisimbio kepada ethanol-bio dan bahan kimia bernilai-tambah. Penyelidikan ini

secara spesifik memfokuskan kepada penukaran hemiselulosa dalam fiber tandan

kosong kelapa sawit (TKKS) kepada xylosa melalui tindakbalas hidrolisis

pemangkin asid. Objektif tesis adalah untuk menjalani ulangkaji terhadap pra

rawatan yang berpotensi untuk asid hidrolisis, mengoptima keadaan tindakbalas

reaktor dan juga mengkaji kinetik hidrolisis asid cair terhadap fiber TKKS dengan

menggunakan reaktor longgok yang telah direkacipta. Satu liter reaktor longgok

telah direkacipta, diformulasi dan dikomisenkan untuk mengkaji hidrolisis asid fiber

TKKS. Setelah beberapa pengubahsuaian and penambahbaikan, suhu operasi

reaktor longgok telah diletakkan pada suhu maksima 140 °C untuk operasi yang

stabil. Nisbah cecair-solid telah ditentukan antara 20:1 hingga 30:1 berdasarkan

isipadu kecil reaktor dan juga kebolehtahanan terhad bakul `stainless steel’ yang

menampung fiber TKKS.

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Komposisi pecahan utama fiber TKKS yang diperoleh melalui analisis TGA ialah

(% berat kering asas): selulosa, 44.5%; hemiselulosa 26.5%; lignin, 19.1%.

Keputusan ini adalah selari dengan kajian sebelum ini ke atas komponen asas TKKS

menggunakan hidrolisis asid secara kuantiti. Pada permulaan kerja eksperimen,

nombor pemangkin asid telah diskrin (H2SO4, HCl and CH3COOH) untuk

menentukan asid terbaik untuk digunakan dalam penyelidikan ini. Kajian skrin-

pemangkin ke atas hidrolisis asid cair fiber TKKS telah dijalankan pada 100 °C dan

nisbah cecair solid adalah 25:1.

Keberkesanan tiga jenis asid telah diuji untuk menentukan pemangkin asid paling

optima bagi penghasilan xylosa. Asid paling optima (H2SO4) telah dipilih dan

diaplikasikan dalam ujikaji yang seterusnya. Kajian terhadap kesan pra-rawatan

ultrasonik turut disertakan dalam kerja ini untuk menguji kesan beberapa kaedah

pra-rawatan ke atas hidrolisis asid cair fiber TKKS. Ujikaji berkenaan telah

dijalankan pada suhu serendah 100 °C dan setinggi 140 °C. Keputusan

menunjukkan pendedahan secara terus fiber TKKS kepada kuasa ultrasonik dengan

signal 20kHz pada amplitud yang berbeza, mempunyai kesan bertanda ke atas

keberkesanan suhu rendah (100 °C) hidrolisis asid berdasarkan kepada hasil

keseluruhan xylosa. Walaubagaimanapun, tiada sebarang penambahbaikan terhadap

hasil xylose yang dapat diperhatikan melalui hidrolisis asid pada 140 °C

mengginakan reaktor longgok. Analisis SEM menunjukkan perubahan ketara

morfologi fiber TKKS terhadap kesan pra-rawatan ultrasonik dan perbezaan keadaan

hidrolisis asid.

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Tiga jenis kepekatan asid iaitu 2%, 4% dan 6% telah dipilih untuk kajian ini. H2SO

4

menunjukkan kesan pemangkinan paling tinggi, diikuti oleh HCl dan CH3COOH.

Pengoptimuman hidrolisis asid cair telah dijalankan menggunakan H2SO4 sebagai

pemangkin. Tindakbalas telah dijalankan di bawah suhu yang berbeza (80 oC hingga

140 oC), kepekatan asid (2%, 4% dan 6%), dan masa tindakbalas (15 min, 30 min,

60 min, 90 min, 120 min dan 150 min). Secara keseluruhannya, keputusan bagi

hidrolisis asid fiber TKKS menunjukkan bahawa kesan kepekatan asid terhadap

penukaran xylosa adalah lebih kritikal pada suhu yang tinggi. Pada sebarang

kepekatan asid dalam kajian ini (2%, 4% dan 6%), suhu optima untuk penghasilan

xylosa telah diperhatikan pada 120 oC. Kepekatan asid mempunyai kesan yang lebih

dominan ke atas penghasilan xylosa pada suhu rendah (bawah 120 °C) dan masa

tindakbalas pendek (kurang dari 60 minit). Dengan kata lain, hidrolisis asid TKKS

adalah lebih sesuai pada kepekatan asid yang rendah bagi suhu lebih dari 120 °C dan

masa tindakbalas melebihi 60 minit. Monomer xylosa yang berada dalam fasa cecair

merupakan kunci penunjuk kepada pemanjangan kepada tindakbalas, seterusnya

menjadi matlamat untuk analisis model kinetik. Kajian kinetik ke atas hidrolisis asid

fiber TKKS menunjukkan bahawa tindakbalas yang terlibat adalah tindakbalas

berbalik pertama. Kinetik tindakbalas utama telah ditentukan dan keadaan

tindakbalas optima telah didefinisikan atas asas kepada model kinetik berkenaan.

Tindakbalas hidrolisis asid cair telah dianalisa menggunakan model kinetik dengan

mengaplikasikan model yang diperkenalkan oleh Saeman.

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Pemalar kinetic untuk model Saeman telah dianalisa menggunakan jenis perluasan

Arrhenius yang melibatkan tenaga pengaktifan dan factor kepekatan pemangkin.

Persamaan yang baik antara model anggapan dan data ujikaji dengan pembolehubah

penentuan melebihi 90%. Kinetik umum yang ditunjukkan dari segi kepekatan asid

dan suhu telah dibina. Akhirnya, walaupun pertukaran tinggi hemiselulosa kepasa

xylosa adalah ketara, aras rendah pertukaran selulosa adalah diberi perhatian.

Beberapa cadangan penambahbaikan telah diusulkan untuk kajian masa hadapan

bagi menambahbaik kajia ini. Walaubagaimanapun, kajian ini menunjukkan bahawa

penggunaan fiber TKKS berkemungkinan menjadi pilihan yang praktikal sebagai

bahan mentah untuk penghasilan gula bagi sintesis bahan api bio, berdasarkan kos

yang murah dan hasil gula yang tinggi.

Kajian ini menekankan potensi serat TKKS sebagai bahan mentah bagi pengeluaran

gula fermentasi terutama xylose untuk penghasilan bioetanol. Kajian ini juga

menunjukkan kemampuan reaktor kelompok dalaman untuk menukar serat TKKS

xylosa dengan keberkesanan sebanyak 80%. Penemuan kajian ini adalah penemuan

keupayaan prarawatan ultrasonik untuk mengubah fizikal permukaan serat TKKS,

justeru meningkatkan hasil xylose. Ultrasonikasi biomass mempunyai potensi untuk

diintegrasikan dengan teknologi prarawatan lignocelluloses yang sedia ada dalam

biojisim untuk pengeluaran bioetanol untuk meningkatkan kecekapan penukaran

secara keseluruhan

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ACKNOWLEDGEMENTS

My deepest appreciation goes to my dedicated supervisor Assoc. Prof. Dr Robiah

Yunus for her patient guidance, valuable suggestion, motivation and endless support

throughout my course the course of my research. I would like to extend my deepest

gratitude to my co-supervisors, Assoc. Prof Dr Nurhafizah Abdullah and Dr Dayang

Radiah Awang Biak for their precious advice and encouragement.

To Dr Chong, Ferra Naidir, Herliati, Azhari, Hamidah, sincere thanks for your

knowledge sharing and making my life in UPM meaningful and memorable. I am

also grateful to my dear friends, Ummi Nor Husna, Norazian, Musjikandi, Yusof

Harun, and others for their assistance throughout the course of the study. I would

like to acknowledge all the lecturers, technichians and staff of Department of

Chemical and Environmental Engineering for the kind cooperation and helping

hands. I am also grateful to UNIMAS for providing me with financial support under

the SLAI scheme that enabled me to undergo the PhD program and Universiti Putra

Malaysia for the short term research grant for funding this research. To all the people

who have helped me directly or indirectly throughout my research, your

contributions are very much appreciated.

Last but not least, to my children; Hakimi, Munira and Farihin, and my parents who

have been my inspiration. To my husband; Mohd Zaihan Lek, for his love, sacrifices,

patience and understanding.

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I certify that a Thesis Examination Committee has met on 13th November 2011 to conduct the final examination of Shanti Faridah Salleh on her thesis entitled “Acid Hydrolysis of Oil Palm Empty Fruit Bunch in A Batch Reactor” in accordance with the Universities and University Colleges Act 1971 and the Constitution of the Universiti Putra Malaysia [P.U.(A) 106] 15 March 1998. The Committee recommends that the student be awarded the Doctor of Philosophy degree. Members of the Examination Committee were as follows: Dr. Luqman Chuah b. Abdullah, PhD Professor Faculty of Engineering Universiti Putra Malaysia (Chairman) Dr. Azni b. Idris , PhD Professor Faculty of Engineering Universiti Putra Malaysia (Internal Examiner) Dr. Thomas Choong Shean Yaw, PhD Associate Professor, Ir. Faculty of Engineering Universiti Putra Malaysia (Internal Examiner) Dr. Vahid Nassehi, PhD Professor Chemical Engineering Department Loughborough University, Loughborough (External Examiner) SEOW HENG FONG, PhD Professor and Deputy Dean School of Graduate Studies Universiti Putra Malaysia Date:

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This thesis was submitted to the Senate of Universiti Putra Malaysia and has been accepted as fulfilment of the requirement for the degree of Doctor of Philosophy. The members of the Supervisory Committee were as follows: Robiah Yunus, PhD Associate Professor Faculty of Engineering Universiti Putra Malaysia (Chairman) Norhafizah Abdullah, PhD Associate Professor Faculty of Engineering Universiti Putra Malaysia (Member) Dayang Radiah Awang Biak, PhD Senior Lecturer Faculty of Engineering Universiti Putra Malaysia (Member) BUJANG BIN KIM HUAT, PhD Professor and Dean School of Graduate Studies Universiti Putra Malaysia Date:

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DECLARATION

I declare that the thesis is my original work except for quotations and citations which have been duly acknowledged. I also declare that it has not been previously, and is not concurrently, submitted for any other degree at Universiti Putra Malaysia or at any other institution.

SHANTI FARIDAH SALLEH

Date:

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TABLE OF CONTENTS

Page ABSTRACT ii ABSTRAK v ACKNOWLEDGEMENTS ix APPROVAL x DECLARATION xii LIST OF TABLES xvi LIST OF FIGURES xiii

CHAPTER

1 INTRODUCTION 1.1 Background 1 1.2 Research Objectives 6 1.3 Thesis Outline 9

2 LITERATURE REVIEW

2.1 Bioethanol 11 2.2 Resources Definition 14 2.2.1 Lignocellulosic Biomass 16 2.2.2 Potential Bioethanol Resources in Malaysia 19 2.3 Pretreatment of Lignocellulosic Materials 22 2.3.1 Physical Pretreatment 23 2.3.2 Physico-Chemical pretreatment 24

2.3.3 Chemical Pretreatment 25 2.3.4 Biological Pretreatment 27 2.3.5 Ultrasonic Pretreatment 27 2.4 Hydrolysis 29 2.4.1 Acid Hydrolysis 30 2.4.2 Factors Affecting Hydrolysis 35 2.5 Reaction Kinetics of Acid Hydrolysis 41 2.6 Reactors for Acid Hydrolysis 55 2.6.1 Batch Reactor 56 2.6.2 Percolation Reactor 58 2.7 Mathematical Modeling of a reactor 60 . 2.8 Development of Acid Hydrolysis Reactor 62 2.9 Analysis of Lignocellulosic Materials and Acid Hydrolysate 67 2.10 Summary 69

3 MATERIAL AND METHODS 3.1 Introduction 70 3.2 Materials and Equipments 70 3.3 Preparation of Raw Material 71

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3.4 General Description of Equipment 72 3.4.1 Design of A Laboratory Scale Acid Hydrolysis of A Batch

Reactor 72 3.5 Experimental Overview 85 3.5.1 Raw Material Chemical Analysis 86 3.5.2 Ultrasonic Pretreatment 86 3.5.3 Dilute Acid Hydrolysis Optimization 87 3.5.4 Kinetic Study of Dilute Acid Hydrolysis in a Batch Reactor 87 3.6 Analysis Methods 88 3.6.1 High Pressure Liquid Chromatography (HPLC) 89 3.6.2 Scanning Electron Microscope (SEM) 89 3.6.3 Thermogravimetric Analysis (TGA) 90 3.6.4 Energy Dispersive X-ray Spectroscopy (EDX) 90 3.7 Sugar Determination in OPEFB NREL 2000 90

4 ULTRASONIC PRETREATMENT OF OIL PALM EMPTY FRUIT

BUNCH FIBRE 4.1 Introduction 95 4.2 Materials and Methods 97 4.2.1 Biomass Preparation 97 4.2.2 Thermogravimetric Characterisation of OPEFB Fibre 97 4.2.3 Ultrasonic Pretreatment 98 4.2.4 Acid Hydrolysis Reaction 98 4.2.5 Analysis Method 99 4.3 Results and Discussions 100 4.3.1 TGA Characterisation of OPEFB Fibre 100 4.3.2 Effects of Ultrasonic Pre-Treatment on Dilute Acid

Hydrolysis of OPEFB Fibre 102 4.3.3 Effect of Ultrasonication on Morphological Structure of

OPEFB Fibre 106 4.3.4 Energy Dispersive X-ray Spectroscopy EDX 111 4.4 Conclusions 113

5 DILUTE ACID HYDROLYSIS OF OPEFB FIBRE IN A BATCH REACTOR 5.1 Introduction 114 5.2 Materials and Methods 115

5.2.1 Raw Material Preparation 115 5.2.2 Acid Hydrolysis Experiment in a Batch Reactor 115 5.2.3 Analysis Method 116

5.3 Results and Discussions 116 5.3.1 Development of Acid Hydrolysis Methods in a Batch

Reactor 116 5.3.2 Acid Screening: Effect of Acid Type 116 5.3.3 Effect of Temperature, Acid Concentration and Reaction

Time on Xylose Yield 119 5.4 Conclusions 123

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6 KINETICS OF DILUTE ACID HYDROLYSIS OF OPEFB FIBRE IN A BATCH REACTOR

6.1 Introduction 125 6.2 Materials and Methods 126 6.3 Model Development 127 6.4 Results and Discussions 130

6.4.1 Determination of Reaction Rate Constants 133 6.4.2 Model Verification/Curve Fitting using MATLAB 135 6.4.3 Parameter Expansions for Saeman Model Kinetics

Constants 145 6.5 Conclusions 153

7 CONCLUSIONS AND RECOMMENDATIONS

7.1 Conclusions 154 7.1.1 Design of a Laboratory Scale Acid Hydrolysis of a

Batch Reactor 154 7.1.2 Ultrasonic Pretreatment of Oil Palm Empty Fruit Bunch

Fibre 155 7.1.3 Dilute Acid Hydrolysis of Oil Palm Empty Fruit Bunch

Fibre in a Batch Reactor 156 7.1.4 Kinetics of Dilute Acid Hydrolysis of OPEFB Fibre in a

Batch Reactor 156 7.2 Recommendations 157

REFERENCES 161 APPENDIX 170 BIODATA OF STUDENT 184 LIST OF PUBLICATIONS 185

1HYDROLYSIS OF OIL PALM EMPTY FRUIT BUNCH USING DILUTEACID2 DEDICATED3 ABSTRACT4Abstrak5ACKNOWLEDGEMENTS6Examination Committee7Supervisory Committee8DECLARATION9TABLE OF CONTENTS10 REFERENCES