SYNTHESIS AND CHARACTERIZATION OF LITHIUM-MODIFIED MESOPOROUS CATALYST FOR SOLVENT-FREE SELECTIVE OLIGOMERIZATION OF GLYCEROL TO DIGLYCEROL MUHAMMAD AYOUB UNIVERSITI SAINS MALAYSIA 2013 SYNTHESIS AND CHARACTERIZATION OF LITHIUM-MODIFIED MESOPOROUS CATALYST FOR SOLVENT-FREE SELECTIVE OLIGOMERIZATION OF GLYCEROL TO DIGLYCEROL By MUHAMMAD AYOUB Thesis submitted in fulfillment of the requirements for the degree of Doctor of Philosophy JULY 2013 ii DEDICATIONS This thesis is dedicated to my beloved father Rafaqat Ali, mother Rahmat Bibi, wife Sarah Ayoub and my lovely daughters Rameen Ayoub and Farzeen Ayoub iii ACKNOWLEDGEMENTS In the name of ALLAH, the Most Beneficent, The Most Merciful First of all, I would like to thank to ALLAH the Almighty for the strength, guidance, and blessing until I accomplished my studies. I am grateful to my supervisor, Assoc. Prof. Dr. Ahmad Zuhairi Abdullah. Under his guidance, I was given the freedom to take my research into the areas that interest me the most. Not only he is a valuable information source, but he is also an excellent mentor. Due to my professor, my time at USM has been excellent. I am thankful to Dean Professor Dr. Azlina Bt. Harun @ Kamaruddin, Dy. Dean Assoc. Prof. Dr. Mohamad Zailani Bin Abu Bakar, Dy. Dean Assoc. Prof. Dr. Mohd Azmier Ahmad, Dy. Dean Assoc. Prof. Dr. Lee Keat Teong, Professor Dr. Bassim H. Hameed and all other persons in the school who encourage me and lead me towards my aim. I greatly appreciate the time and advice of my committee members. Thank you for reading through and editing this document! I am especially grateful to the past and present my research group members. They have been enjoyable to work with and have become life-long friends. I want to acknowledge my colleagues and friends specifically Benoit Faye and Reinhard Eckelt who greatly contributed to my research. I appreciate the laboratory assistance from USM Engineering campus. I wouldn’t have been able to make it through my PhD without the help of my friends and family. My parents, parents-in-law and all other family members have supported me with their precious prayers throughout my academic career. I finally made my dream come true! I am delighted to express my deepest affection, iv appreciation and thanks to my wife, Mrs. Sarah Ayoub, and my beautiful precious daughters, Rameen Ayoub and Farzeen Ayoub, who have always been with me during this period. They encouraged me with their love and understanding during difficult moments and also shared my joy and success all along. The strength of my uncle, K.A.Dost, taught me to fight through even the worst of situations. Special thanks to Dr. Muhammad Faisal Irfan, Dr. Shahid Iqbal, Dr. Muhammad Zubair, Dr. Javed Akhtar, Mr. Ubaid-Ullah, Mr. Khozema bin Ahmad Ali, Dr. Mutaz S.K, Dr. Mushtaq Ahmad and his wife Dr. Sahzia Sultana for their friendship and entertainment during long lab days I would also like to thank all other people whom I could not name here, for being near me in these years. All of them have made immense contribution to my study and life by their support, inspiration, understanding and sacrifices and therefore, I sincerely dedicate this piece of work to these people whom I love and cherish for the rest of my life. Acknowledgements are also extended to the USM for awarding IPS fellowship during whole period of my research. Lastly, but most importantly, I would like to thank Allah (Subhanaho Wa Tala) and our Holy Prophet Muhammad (Peace be upon him) for always keeping an eye over me and blessing me each day. Muhammad Ayoub, April 2013. v TABLE OF CONTENTS ACKNOWLEDGEMENTS __________________________________________ iv TABLE OF CONTENTS ____________________________________________ vi LIST OF FIGURES ________________________________________________ xii LIST OF TABLES ________________________________________________ xvii LIST OF APPENDICES ___________________________________________ xix LIST OF SYMBOLS ______________________________________________ xxi LIST OF ABBREVIATIONS ______________________________________ xxiii ABSTRAK _______________________________________________________ xxv ABSTRACT _____________________________________________________ xxvii CHAPTER ONE : INTRODUCTION __________________________________ 1 1.1 Fuel crisis _____________________________________________________ 1 1.2 World biodiesel production ________________________________________ 2 1.3 World glycerol production ________________________________________ 4 1.4 World glycerol pricing ___________________________________________ 5 1.5 Glycerol applications in industry ___________________________________ 7 1.6 Diglycerol as a valuable product of glycerol __________________________ 8 1.6.1 Diglycerol applications _______________________________________ 8 1.6.2 Diglycerol formation _________________________________________ 9 1.7 Glycerol oligomerization for diglycerol production ____________________ 10 1.7.1 Homogeneous catalysts ______________________________________ 10 vi 1.7.2 Heterogeneous catalysts ______________________________________ 11 1.7.3 Acid/ base heterogeneous catalysts _____________________________ 11 1.8 Acidic or basic solid catalysts for glycerol oligomerization ______________ 12 1.9 Modified clay as a catalyst for glycerol oligomerization ________________ 13 1.10 Problem statement _____________________________________________ 15 1.11 Objectives ___________________________________________________ 17 1.12 Scope of study ________________________________________________ 18 1.13 Thesis organization ____________________________________________ 19 CHAPTER TWO : LITERATURE REVIEW ___________________________ 22 2.1 Background ___________________________________________________ 22 2.2 Existing diglycerol synthesis methods ______________________________ 24 2.2.1 Small scale method _________________________________________ 24 2.2.2 Glycerol derivatization method ________________________________ 24 2.2.3 Pyrolysis of glycerol method __________________________________ 25 2.2.4 Industrial epichlorohydrin method ______________________________ 25 2.2.5 Catalytic reaction method ____________________________________ 26 2.3 Homogeneously catalyzed reaction for selective diglycerol______________ 26 2.3.1 Homogeneous acid catalysts __________________________________ 27 2.3.2 Homogeneous base catalysts __________________________________ 28 2.4 Solvent free glycerol etherification over solid catalysts _________________ 31 2.5 Oligomerization of glycerol to diglycerol ____________________________ 33 2.5.1 Production of undesired diglycerol isomers ______________________ 34 2.5.2 Production of the desired diglycerol isomers ______________________ 35 vii 2.6 Heterogeneously catalyzed reaction for selective diglycerol _____________ 37 2.6.1 Acidic heterogeneous catalysts ________________________________ 38 2.6.2 Basic heterogeneous catalysts _________________________________ 39 2.6.3 Metal oxide _______________________________________________ 40 2.6.4 Mixed metal oxides _________________________________________ 41 2.6.5 Microporous base catalysts ___________________________________ 42 2.6.6 Mesoporous base catalysts ____________________________________ 45 2.7 Montmorillonites clay as a solid mesoporous catalyst __________________ 49 2.8 Active metal for glycerol oligomerization to diglycerol _________________ 53 2.8.1 Alkali and alkaline earth metals as an active metal _________________ 53 2.8.2 Lithium compound as an active metal ___________________________ 54 2.9 Summarize heterogeneous activities for oligomerization ________________ 56 2.10 Effect of operating variables _____________________________________ 59 2.10.1 Effect of reaction temperature ________________________________ 59 2.10.2 Effect of catalyst loading ____________________________________ 60 2.10.3 Effect of reaction time ______________________________________ 61 2.11 Optimization studies ___________________________________________ 62 2.11.1 Response surface methodology (RSM) _________________________ 62 2.11.2 Central composite design (CCD) ______________________________ 64 2.11.3 Model fitting and validation __________________________________ 65 2.12 Kinetic study for oligomerization _________________________________ 65 2.13 Catalyst reusability study _______________________________________ 66 CHAPTER THREE : MATERIALS AND METHODOLOGY _____________ 69 viii 3.1 Materials and Chemicals _________________________________________ 69 3.2 Overall experimental flowchart ___________________________________ 72 3.3 Equipment ____________________________________________________ 73 3.4 Reactor setup for glycerol oligomerization ___________________________ 74 3.5 Catalyst preparation methods _____________________________________ 76 3.5.1 Preparation of SBA-15 support ________________________________ 76 3.5.2 Preparation of Li/ USY catalyst ________________________________ 77 3.5.3 Preparation of Li/ SBA-15 catalyst _____________________________ 77 3.5.4 Preparation of Li-Mg/ SBA-15 catalyst __________________________ 78 3.5.5 Preparation of Li/ MK-10 catalyst ______________________________ 78 3.6 Characterization of support and catalyst _____________________________ 79 3.6.1 X-ray diffraction (XRD) _____________________________________ 81 3.6.2 Surface analysis (BET, BJH, Vp, Dp) ____________________________ 81 3.6.3 Transmission electron microscope (TEM) ________________________ 82 3.6.4 Scanning electron microscope (SEM) ___________________________ 82 3.6.5 Energy dispersive X-ray (EDX) ________________________________