LANTHANUM OXIDE-PROMOTED COBALT CATALYST SUPPORTED ON MESOPOROUS ALUMINA FOR SYNGAS PRODUCTION VIA METHANE DRY REFORMING TRAN NGOC THANG DOCTOR OF PHILOSOPHY UNIVERSITI MALAYSIA PAHANG UNIVERSITI MALAYSIA PAHANG DECLARATION OF THESIS AND COPYRIGHT Author’s Full Name : TRAN NGOC THANG Date of Birth : 20th NOVEMBER 1982 Title : LANTHANUM OXIDE-PROMOTED COBALT CATALYST SUPPORTED ON MESOPOROUS ALUMINA FOR SYNGAS PRODUCTION VIA METHANE DRY REFORMING Academic Session : SEMESTER 1 2021/2022 I declare that this thesis is classified as: CONFIDENTIAL (Contains confidential information under the Official Secret Act 1997)* RESTRICTED (Contains restricted information as specified by the organization where research was done)* OPEN ACCESS I agree that my thesis to be published as online open access (Full Text) I acknowledge that Universiti Malaysia Pahang reserves the following rights: 1. The Thesis is the Property of Universiti Malaysia Pahang 2. The Library of Universiti Malaysia Pahang has the right to make copies of the thesis for the purpose of research only. The Library has the right to make copies of the thesis for academic exchange.
Certified by: _____________________ _______________________ (Student’s Signature) (Supervisor’s Signature) C3811844 Ts. Sumaiya bt Zainal Abidin @ Murad ______________________ New IC/Passport Number Name of Supervisor Date: 04 January 2022 Date: 04 January 2022 NOTE: * If the thesis is CONFIDENTIAL or RESTRICTED, please attach a thesis declaration letter. SUPERVISOR’S DECLARATION We hereby declare that we have checked this thesis and in our opinion, this thesis is adequate in terms of scope and quality for the award of the degree of Doctor of Philosophy. _______________________________ (Supervisor’s Signature) Full Name : TS.
SUMAIYA BT ZAINAL ABIDIN @ MURAD Position : ASSOCIATE PROFESSOR Date : 04 JANUARY 2022 _______________________________ (Co-supervisor’s Signature) Full Name : DR. NURUL AINI BINTI MOHAMED RAZALI Position : ASSOCIATE PROFESSOR Date : 04 JANUARY 2022 STUDENT’S DECLARATION I hereby declare that the work in this thesis is based on my original work except for quotations and citations which have been duly acknowledged. I also declare that it has not been previously or concurrently submitted for any other degree at Universiti Malaysia Pahang or any other institutions. _____________________________ (Student’s Signature) Full Name : TRAN NGOC THANG ID Number : PKC18003 Date : 04 JANUARY 2022 LANTHANUM OXIDE-PROMOTED COBALT CATALYST SUPPORTED ON MESOPOROUS ALUMINA FOR SYNGAS PRODUCTION VIA METHANE DRY REFORMING TRAN NGOC THANG Thesis submitted in fulfillment of the requirements for the award of the degree of Doctor of Philosophy College of Engineering UNIVERSITI MALAYSIA PAHANG JANUARY 2022 ACKNOWLEDGEMENTS I would like to express my honest gratefulness to my supervisor, Assoc.
Sumaiya bt Zainal Abidin @ Murad for her meaningful guidance and support throughout the difficult time in the COVID-19 pandemic condition. She always encouraged me with her outstanding experience and valuable awareness. I also would like to thank my ex- main supervisor Dr. Vo Nguyen Dai Viet for his constant support.
He has imparted me with professional knowledge and unique insights as well as useful research skills in the reaction engineering and heterogeneous catalysis field for nurturing me as a qualified academician. I also wish to acknowledge my co-supervisor, Assoc. Nurul Aini Mohamed Razali for her suggestions and cooperation throughout the study. I appreciate the co-operation and information sharing in this research from all my colleagues in GTL group including Mahadi Bahari, Attili Ramkiran, Fahim Fayaz, Tan Ji Siang, Lau Ngie Jun, Shafiqah Nasir, and Sharanjit Singh.
Additionally, I would like to acknowledge all my lab mates, friends, and teaching staff of the Department of Chemical Engineering, College of Engineering and the Faculty of Chemical and Process Engineering Technology, Universiti Malaysia Pahang for their collaboration and friendship. Finally, I dedicate this thesis to my family for their endless love, support, and the source of my motivation in pursuing the studies. ii ABSTRAK Tindak balas pembaharuan kering metana (MDR) baru-baru ini muncul sebagai antara pendekatan pelbagai guna yang terbaik untuk menukar dua gas rumah hijau, karbon dioksida (CO2) dan metana (CH4), kepada bahan mentah yang berharga untuk proses hiliran petrokimia. Pada masa ini, masih terdapat cabaran dalam membangunkan pemangkin yang sangat stabil dan aktif untuk tindak balas MDR di samping rintangan yang lebih baik terhadap pemendapan karbon.
Baru0baru ini, pemangkin berasaskan kobalt yang disokong mesopori alumina muncul sebagai pemangkin yang berpotensi. Walau bagaimanapun, bahan-bahan konvensional yang digunakan untuk menyediakan sokongan pemangkin mesopori ini ialah prekursor organik dan etanol yang agak mahal dan berbahaya kepada alam sekitar. Oleh itu, dalam kajian ini, penggunaan mesopori alumina (Al2O3), yang direka menggunakan prekursor aluminium bukan organik yang murah dan tersedia dalam pelarut binari etanol-air, telah dikaji sebagai sokongan untuk pemangkin kobalt. Penyiasatan ini bertujuan untuk mereka bentuk sistem pemangkin berasaskan kobalt yang berkesan untuk tindak balas MDR, yang mengatasi halangan penyahaktifan yang disebabkan oleh karbon.
Kesan promosi La2O3 pada ciri fizikokimia pemangkin kobalt yang disokong Al2O3 dan prestasi pemangkinnya juga telah dijelaskan. Penilaian mangkin dalam tindak balas MDR telah dijalankan untuk mangkin 10%Co/Al2O3 dan 10%Co/Al2O3 yang digalakkan La2O3 (pemuatan La adalah dalam 1% – 8%) dalam reaktor katil tetap pada julat suhu 923 – 1073 K dan tekanan separa bagi bahan tindak balas dari 10 hingga 40 kPa. Sokongan Al2O3 mempunyai luas permukaan BET 173.4 m2 g-1 dan nanopartikel kobalt tersebar dengan halus diatas sokongan dengan saiz kristal yang dikehendaki berjulat dari 5. Interaksi kuat antara CoO dan Al2O3 telah disahkan dengan kehadiran spinel kobalt-aluminat dan struktur tekstur pemangkin adalah stabil terhadap suhu tindak balas.
Tingkah laku promosi La2O3 memudahkan pengurangan H2 dengan menyediakan ketumpatan elektron yang lebih tinggi dan meningkatkan kekosongan oksigen dalam 10%Co/Al2O3. Penambahan La2O3 boleh mengurangkan tenaga pengaktifan ketara bagi penggunaan CH4; lalu, meningkatkan penukaran CH4 sehingga 93. Pembentukan lanthanum dioksikarbonat secara terus semasa MDR bertanggungjawab dalam pengurangan karbon termendap melalui kitaran redoks sebanyak 17-30% bergantung pada suhu tindak balas. Selain itu, tahap kekosongan oksigen meningkat kepada 73.3% dengan promosi La2O3.
Pemuatan 5%La ialah kandungan penggalak yang optimum untuk penukaran bahan tindak balas serta penghasilan H2 dan CO. 5%La-10%Co/Al2O3 juga mempamerkan rintangan tertinggi terhadap pemendapan karbon kerana sifat asas, ciri redoks penggalak La2O3. Tindak balas MDR ke atas pemangkin 5%La-10%Co/Al2O3 telah diyakini mengikuti mod penjerapan bersekutu CH4 dan CO2 pada dwi tapak zarah aktif atau berbeza dan pemangkin menunjukkan kestabilan yang baik semasa tindak balas 48 jam pada 1023 K.98 yang terhasil adalah sesuai untuk tindak balas Fischer-Tropsch di hiliran untuk menjana bahan api hidrokarbon cecair. Akibatnya, penggunaan sokongan mesopori alumina dan penggalakk La2O3 meningkatkan aktiviti Co dengan efektif dalam tindak balas MDR disamping menahan pemendapan karbon pada permukaan pemangkin.
iii ABSTRACT Methane dry reforming reaction (MDR) has recently emerged as a promising multipurpose approach for converting two greenhouse gasses, included carbon dioxide (CO2) and methane (CH4), into valuable feedstock for downstream petrochemical processes. At present, there is still a challenge in developing the highly stable and active catalysts for MDR reaction as well as better resistance to carbon deposition. Though the mesoporous alumina supported Co-based catalysts have recently appeared to be the potential catalysts. However, the common starting materials for preparing these well- ordered mesoporous catalyst supports are organic precursors and anhydrous ethanol which are quite expensive and harmful to the environment.
Therefore, in this study, mesoporous alumina (Al2O3), fabricated using a cheap and available inorganic aluminium precursor in binary water-ethanol solvent, was implemented as support for cobalt catalyst. This investigation aimed to design an effective cobalt-based catalyst system for MDR reaction, which overcomes coke-related deactivation barriers. The promotional effect of La2O3 on the physicochemical features of Al2O3 supported cobalt catalyst and its catalytic performance were also elucidated. The catalyst evaluations in MDR reaction were conducted for 10%Co/Al2O3 and La2O3-promoted 10%Co/Al2O3 catalysts (La loading was in 1% – 8%) in a fixed-bed reactor at temperature range of 923 – 1073 K and partial pressure of individual reactant from 10 to 40 kPa.
The Al2O3 support has BET surface area of 173.4 m2 g-1 and cobalt nanoparticles were finely dispersed on the support with desired crystallite size ranged from 5. The strong interaction of CoO and Al2O3 phases was confirmed by the presence of cobalt-aluminate spinel and the textural structure of catalysts was stable with reaction temperature. The promotion behavior of La2O3 facilitated H2-reduction by providing higher electron density and enhanced oxygen vacancy in 10%Co/Al2O3. The addition of La2O3 could reduce the apparent activation energy of CH4 consumption; hence, increasing CH4 conversion up to 93.
Lanthanum dioxycarbonate transitional phase formed in situ during MDR was accountable for mitigating deposited carbon via redox cycle for 17-30% relying on reaction temperature. Additionally, the oxygen vacancy degree increased to 73.3% with La2O3 promotion. 5%La loading was an optimal promoter content for reactant conversions as well as yield of H2 and CO. 5%La-10%Co/Al2O3 also exhibited the highest resistance to carbon deposition owing to the basic nature, redox feature of La2O3 dopant.
The MDR reaction over 5%La-10%Co/Al2O3 catalyst was convinced to follow an associative adsorption mode of CH4 and CO2 on dual or different sites of active particles and the catalyst exhibited a good stability during 48 h reaction at 1023 K. The resulting H2/CO ratios of 0.98 are suitable for Fischer-Tropsch reaction in downstream to generate liquid hydrocarbon fuels. As a result, the employment of mesoporous alumina support and La2O3 promoter efficiently boosted the Co activity in MDR reaction along with suppressing the carbon deposition on the catalyst surface. iv TABLE OF CONTENT DECLARATION TITLE PAGE ACKNOWLEDGEMENTS ii ABSTRAK iii ABSTRACT iv TABLE OF CONTENT v LIST OF TABLES ix LIST OF FIGURES x LIST OF ABBREVIATIONS xv CHAPTER 1 INTRODUCTION 1 1.4 Objectives of Study 4 1.5 Scope of Study 5 1.6 Thesis Organization 6 CHAPTER 2 LITERATURE REVIEW 8 2.2 Overview of Syngas 8 2.3 Methane Dry Reforming Reaction 11 2.1 The Kinetics Studies 11 v 2.3 The Catalyst Development 22 2.4 Concluding Remarks 40 CHAPTER 3 METHODOLOGY 41 3.2 Materials and Equipment 43 3.2 X-ray Diffraction Analysis 47 3.3 H2 Temperature-programmed Reduction 48 3.4 CO2 Temperature Programmed Desorption 48 3.5 Temperature-programmed Oxidation 49 3.6 High Resolution Transmission Electron Microscopy 49 3.8 X-ray Photoelectron Spectroscopy 50 3.1 Experimental Set-up 50 3.3 Mass Flow Controller Calibration 52 3.4 Transport Resistance Estimation 53 3.6 Kinetic Parameters Determination and Modelling 54 vi CHAPTER 4 EVALUATION OF MESOPOROUS ALUMINA-SUPPORTED COBALT NANOCATALYST FOR METHANE DRY REFORMING REACTION 56 4.2 Characterization of Fresh Catalysts 56 4.4 Surface Morphology Analyses 61 4.3 Catalytic Performance for MDR 61 4.4 Spent Catalysts Characterization 65 4.5 Concluding Remarks 69 CHAPTER 5 LA-DOPED COBALT SUPPORTED ON MESOPOROUS ALUMINA CATALYSTS FOR IMPROVED METHANE DRY REFORMING AND COKE MITIGATION 70 5.2 Catalyst Attributes Assessment 70 5.2 X-ray powder Diffraction Measurement 72 5.3 H2 Temperature-programmed Reduction Analysis 74 5.4 CO2 Temperature-programmed Desorption 75 5.3 Catalytic Performance for MDR 77 5.1 Influence Reaction Temperature 77 vii 5.2 Influence of Promoter Loading 80 5.3 Influence of CH4 and CO2 Partial Pressure 83 5.4 Mechanistic Study of The MDR over 5%La-10%Co/Al2O3 86 5.4 Spent Catalyst Characterizations 93 5.3 Thermal Programmed Oxidation Measurements 96 5.4 X-ray Photoelectron Analyses 100 5.5 HRTEM Surface Morphology Study 105 5.5 Concluding Remarks 110 CHAPTER 6 CONCLUSIONS AND RECOMMENDATIONS 111 6.2 Recommendations 112 REFERENCES 114 APPENDIX A 137 APPENDIX B 140 APPENDIX C 142 APPENDIX D 152 viii LIST OF TABLES Table 2.1 List of involved reactions in the MDR reaction 15 Table 2.2 List of LH rate expressions proposed for MDR reaction 17 Table 2.3 Summary of MDR performance over different supported catalysts reported in literature 31 Table 2.4 Summary of textural properties of alumina and alumina supported catalysts reported in literature 39 Table 3.1 List of purchased chemicals and gases 44 Table 3.2 List of experimental equipments 44 Table 3.3 Summary of used chemicals for catalysts preparation 46 Table 3.4 Information of standard gas from GC analysis 52 Table 3.5 Properties used in the calculation of transport resistances 53 Table 4.1 Summary of textural attributes of Al2O3 and 10%Co/Al2O3 58 Table 4.2 Summary of peak assignment during H2 reduction of 10%Co/Al2O3.3 Summary of textural attributes of spent 10%Co/Al2O3 after MDR at 973 K, 1023 K and 1073 K.1 Physical attributes of Al2O3, 10%Co/Al2O3, and La2O3-promoted 10%Co/Al2O3 catalyst 71 Table 5.