DEVELOPMENT OF NANOCATALYSTS VIA CO-PRECIPITATION CUM MODIFIED STÖBER METHOD AND APPLICATION TO METHANE DECOMPOSITION MUHAMMED ASHIK.U. - PDF

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DEVELOPMENT OF NANOCATALYSTS VIA CO-PRECIPITATION CUM MODIFIED STÖBER METHOD AND APPLICATION TO METHANE DECOMPOSITION MUHAMMED ASHIK.U.P THESIS SUBMITTED IN FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE

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DEVELOPMENT OF NANOCATALYSTS VIA CO-PRECIPITATION CUM MODIFIED STÖBER METHOD AND APPLICATION TO METHANE DECOMPOSITION MUHAMMED ASHIK.U.P THESIS SUBMITTED IN FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY FACULTY OF ENGINEERING UNIVERSITY OF MALAYA KUALA LUMPUR 2016 UNIVERSITI MALAYA ORIGINAL LITERARY WORK DECLARATION Name of Candidate: Muhammed Ashik.U.P (Passport No.: G ) Registration/Matric No.: KHA Name of Degree: Doctor of Philosophy Title of Project paper/research Report/ Dissertation/ Thesis ( this work ): Development of Nanocatalysts via Co-Precipitation cum Modified Stöber Method and Application to Methane Decomposition Field of Study: Reaction Engineering I do solemnly and sincerely declare that: 1. I am the sole author/writer of this work; 2. This work is original 3. Any use of any work in which copyright exists was done by way of fair dealing and for permitted purposes and any excerpt or extract form, or reference to or reproduction of any copyright work has been disclosed expressly and sufficiently and the title of the work and its authorship have been acknowledged in this work; 4. I do not have any actual knowledge nor do I ought reasonably to know that the making of this work constitutes an infringement of any copyright work; 5. I hereby assign all and every rights in the copyright to this work to the University of Malaya ( UM ), who henceforth shall be owner of the copyright in this work and that any reproduction or use in any form or by any means whatsoever is prohibited without the written consent of UM having been first had and obtained; 6. I am fully aware that if in the course of making this work I have infringed any copyright whether intentionally or otherwise, I may be subject to legal action or any other action as may be determined by UM. Candidate s Signature Date Subscribed and solemnly declared before, Witness s Signature Date Name: Designation: ABSTRACT Nanoparticle formation from their respective precursors through bottom-up method is a very fascinating practice in nanotechnology. This research contribution discusses two promising bottom-up methods: i) controlled precipitation of Ni, Fe, and Co nanoparticles and reinforcement with silicate through modified Stöber method, and ii) chemical vapor deposition of nanocarbon from methane. Thermocatalytic decomposition of methane is a fully green single step technology for producing hydrogen and nanocarbon. In spite of having great success in the laboratory scale production, industrial thermocatalytic decomposition of methane for greenhouse gas free hydrogen production is still in its infancy. However, deactivation of catalyst is the prime drawback found in thermocatalytic decomposition of methane. In this research contribution, n-nio/sio2, n- FeO/SiO2, and n-coo/sio2 nano-structured catalysts were prepared by co-precipitation cum modified Stöber method and used for thermocatalytic decomposition of methane to produce hydrogen and carbon nanotubes. Our experimental results reveal that the metal oxide particles were formed as single crystal nanoparticles upon the addition of silicate and exhibited catalytic activity promoting features, such as lower particle size and higher surface area and porosity. Temperature programmed methane decomposition from 200 to 900 C were conducted in a fixed bed pilot plant as preliminary catalytic examination and further isothermal analysis were performed in between 475 and 700 C. Production of hydrogen at each experimented temperature and corresponding carbon yield were measured. Among the three catalysts inspected, n-nio/sio2 found as the most efficient one for thermocatalytic methane decomposition and exhibited methane transformation activity more than 300 min, without a significant deactivation at temperature range from 475 to 600 C, designating the resistance capability of analyzed nano-structured catalyst irrespective of many reported catalysts. n-nio/sio2 produced an enormous carbon yield of ~5000% at 600 C within 5 h of experiment. While, the rapid deactivation of the n- iii FeO/SiO2 and n-coo/sio2 catalysts were attributed to the particle agglomeration and irregular formation of nanocarbon due to the metal fragmentation. Most efficient n- NiO/SiO2 catalyst was selected for further studies. Methane decomposition kinetics over n-nio/sio2 catalyst were studied by considering thermodynamic deposition of carbon at a temperature range of 550 to 650 C and methane partial pressure from 0.2 atm to 0.8 atm. The findings concluded that the enhancement occurred with carbon formation rate when increasing the methane partial pressure, which is very much evident at higher temperature such as 650 C. The effects of methane partial pressure and reaction temperature on the specific molar carbon formation rate were examined. The calculated reaction order and activation energy were found to be 1.40 and 60.9 kj mol -1, respectively. The governance of porosity and methane decomposition activity sustainability of n- NiO/SiO2 catalyst by changing synthesis parameters such as nickel/silicate ratio, C18TMS/TEOS ratio and different solvents were also conducted. Physical and chemical characteristics of produced nano-catalysts were performed by N2 adsorption-desorption measurement (BET), X-ray diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy - Energy-dispersive X-ray spectroscopy (FESEM-EDX), and hydrogen-temperature programmed reduction (H2-TPR). Produced nanocarbons were inspected with TEM, FESEM, and XRD. iv ABSTRAK Pembentukan nanopartikel daripada rumusan asalnya kaedah bottom-up adalah amalan yang sangat menarik dalam teknologi nano. Dua kaedah bottom-up telah digunakan dalam penyelidikan ini iaitu; i) mendakan terkawal nano-partikel Ni, Fe dan Co dan pengukuhannya dengan silikat dengan kaedah Stöber yang telah diubahsuai dan ii) pemendapan wap kimia nano karbon daripada metana. Penguraian pemangkin haba metana adalah satu langkah teknologi hijau untuk menghasilkan hidrogen dan nano karbon. Walaupun mempunyai kejayaan besar dalam pengeluaran skala makmal, penguraian pemangkin haba metana bagi pengeluaran gas rumah hijau tanpa hydrogen dalam industri masih di peringkat awal. Walau bagaimanapun, penyahaktifan mangkin adalah kelemahan utama yang ditemui dalam penguraian pemangkin haba metana. Sumbangan kajian ini, n-nio/sio2, n-feo/sio2 dan n-coo/sio2 pemangkin berstruktur nano menyediakan pemangkin melalui mendakan yang diubahsuai menggunakan kaedah Stöber untuk penguraian pemangkin haba metana bagi menghasilkan hidrogen dan karbon nanotube dalam membangunkan pemangkin yang sangat stabil. Hasil eksperimen menunjukkan bahawa zarah logam oksida terbentuk sebagai zarah nano kristal tunggal melalui penambahan silikat dan mempamerkan aktiviti pemangkin yang mempunyai ciriciri seperti saiz zarah yang lebih rendah dan luas permukaan yang lebih tinggi dan keliangan. Penguraian metana yang di programkan suhu dibuat di sebuah kilang perintis katil tetap sebagai pemeriksaan awal pemangkin dan analisis sesuhu lanjut telah dilakukan di antara 475 dan 700 C. Jumlah pengeluaran hidrogen pada setiap suhu eksperimen dan hasil karbon dicatatkan. Antara tiga pemangkin yang dikaji, n-nio/sio2 merupakan pemangkin yang paling berkesan untuk penguraian pemangkin haba metana dan telah mempamerkan aktiviti transformasi metana lebih daripada 300 minit tanpa banyak penyahaktifan pada julat suhu C, tidak seperti kebanyakan kajian yang mengkaji kebolehan pemangkin berstruktur nano terhadap keupayaan kalangan. v Sementara itu, penyahaktifan pesat pemangkin n-feo/sio2 dan n-coo/sio2 menyumbang kepada aglomerasi zarah dan pembentukan nano karbon yang tidak sekata disebabkan oleh pemecahan logam. Pemangkin n-nio/sio2 yang merupakan pemangkin yang paling efisien telah dipilih bagi kajian lanjut. Kinetik penguraian metana ke atas pemangkin n-nio/sio2 telah dikaji dengan mempertimbangkan pemendapan termodinamik karbon dalam pelbagai suhu di antara 550 C sehingga 650 C dan tekanan separa metana dari 0.2 atm sehingga 0.8 atm. Hasil kajian mendapati bahawa peningkatan itu berlaku dengan kadar pembentukan karbon apabila maningkatkan tekanan separa metana pada suhu yang labih tinggi seperti 650 C. kesan tekanan separa metana dan tindak balas suhu pada molar spesifik bagi kadar pembentukan karbon telah dikaji. Orde reaksi dan tenaga pengaktifan yang telah dikira masing-masing sebanyak 1.40 dan 60.9 kj mol -1. Kajian terhadap keliangan dan aktiviti penguraian metana bagi memastikan kemampanan pemangkin n-nio/sio2 dengan menukarkan parameter sintesis seperti nisbah nikel/silikat, nisbah C18TMS/TEOS dan pelurat yang berbeza turut dijalankan. Cir-ciri fizikal dan kimia yang dihasilkan pemangkin nano telah dijalankan melalui pengukuran penjerapan-penyaherapan N2 (BET), pembelauan sinar-x (XRD), transmisi mikroskop electron (TEM), imbasan mikroskop electron Tenaga sebaran sinar-x (FESEM-EDX) dan pengurangan suhu hidrogen diprogramkan (H2-TPR). Nano karbon yang dihasikan telah diperiksa dengan TEM, FESEM dan XRD. vi ACKNOWLEDGEMENTS In the name of God, Most Gracious, Most Merciful Read! In the name of your Lord who created - Created the human from something which clings - Read! And your Lord is Most Bountiful - He who taught (the use of) the Pen - Taught the human that which he knew not. (Holy Quran 96:1-5) My deepest gratitude is to my supervisor, Prof. Dr. Wan Mohd Ashri Wan Daud. I have been amazingly fortunate to have an advisor who gave me the freedom to explore on my own, and at the same time the guidance to recover when my steps faltered. Special thanks to Dr. Hazzim Fadhil Abbas, Department of Chemical Engineering, University of Nizwa, Oman, for his inspiration and support. Sincere thanks go to all those who have helped me in the various stages of this work, even with a mere word of encouragement. Thanks are also due to my fellow researchers, senior researchers in our group, all technicians, and staff in the Department of Chemical Engineering. It is their support that helped me to complete my project work successfully. Most importantly, none of this would have been possible without the love and patience of my family. Both Urampully and Thanappadath families to whom this thesis is dedicated to, have been consistent sources of love, concern, support, and strength all these years. My profound thanks and gratitude are extended with full respect, honor, and love to my beloved parents, who were my first teachers. I am really short of suitable words to express my gratitude and appreciation to my better half Shanu, who supported and tolerated me throughout this work. Finally, I appreciate the financial support from University of Malaya through High Impact Research Grant (UM.C/HIR/MOHE/ENG/11). Above all I prostrate myself in front of God almighty, the most merciful. O my Sustainer! Increase my knowledge (Holy Qur an 20:114). Muhammed Ashik.U.P March 2016 vii TABLE OF CONTENTS Title ABSTRACT Page No. iii ABSTRAK v ACKNOWLEDGEMENTS vii TABLE OF CONTENTS viii LIST OF FIGURES xiv LIST OF TABLES xx LIST OF SYMBOLS AND ABBREVIATIONS xxii LIST OF APPENDICES xxvi CHAPTER 1: INTRODUCTION GENERAL SCOPE OF WORK AIM OF STUDY OBJECTIVES OF STUDY THESIS STRUCTURE 8 CHAPTER 2: LITERATURE REVIEW HYDROGEN ENERGY THERMOCATALYTIC DECOMPOSITION OF METHANE Metal Catalysts for TCD 15 viii Non-supported catalysts Metal supported catalysts Metal oxide supported catalysts Ceramic and red-mud based catalyst Thin layer catalysts Experimental parameters influencing activity of metal catalyst Deactivation of metal catalysts Carbonaceous Catalyst for TCD Experimental parameters influencing activity of carbonaceous catalyst Deactivation of carbonaceous catalysts Carbon Catalytic Activity Boost by Metal Doping Comparison between Metal and Carbonaceous Catalysts 51 CHAPTER 3: MATERIALS AND METHODS INTRODUCTION PART 1: STABILIZATION OF Ni, Fe, AND Co NANO- PARTICLES THROUGH MODIFIED STÖBER METHOD TO OBTAIN EXCELLENT CATALYTIC PERFO- RMANCE: PREPARATION, CHARACTERIZATION, AND CATALYTIC ACTIVITY FOR METHANE DECOM- POSITION Materials 64 ix 3.2.2 Experimental Section Preparation of n-nio, n-feo, and n-coo nanoparticles through co-precipitation Stabilization of nanometal oxides using silicate through the modified Stöber method Characterization techniques Preliminary catalytic activity analysis PART 2: PROBING THE DIFFERENTIAL METHANE DECOMPOSITION BEHAVIORS OF n-nio/sio2, n- FeO/SiO2, AND n-coo/sio2 CATALYSTS PREPARED THROUGH CO-PRECIPITATION CUM MODIFIED STÖBER METHOD Experimental Setup for TCD Thermocatalytic Decomposition of Methane PART 3: METHANE DECOMPOSITION KINETICS AND REACTION RATE OVER n-nio/sio2 CATALYST Materials Experimental Setup PART 4: GOVERNANCE OF POROSITY AND METHANE DECOMPOSITION ACTIVITY SUSTAINABILITY OF n-nio/sio2 CATALYST BY CHANGING SYNTHESIS PARAMETERS Synthesis of n-nio/sio2 Catalysts through Coprecipitation cum Modified Stöber Method Thermocatalytic Decomposition of Methane 76 x CHAPTER 4: RESULTS AND DISCUSSION PART 1: STABILIZATION OF Ni, Fe, AND Co NANO- PARTICLES THROUGH MODIFIED STÖBER METHOD TO OBTAIN EXCELLENT CATALYTIC PERFORM- ANCE: PREPARATION, CHARACTERIZATION, AND CATALYTIC ACTIVITY FOR METHANE DECOMPO- SITION X-ray Diffraction Analysis Porosity Analysis Morphology and Composition Analysis Reduction Behavior Temperature Programmed Methane Decomposition Characterization of As-produced Nanocarbon Summary of Major Findings PART 2: PROBING THE DIFFERENTIAL METHANE DECOMPOSITION BEHAVIORS OF n-nio/sio2, n- FeO/SiO2, AND n-coo/sio2 CATALYSTS PREPARED THROUGH CO-PRECIPITATION CUM MODIFIED STÖBER METHOD Influence of Temperature on TCD over n-nio/sio2, n- FeO/SiO2, and n-coo/sio2 Catalysts Influence of Methane Feed Flow Rate on TCD over n- NiO/SiO2 Catalyst Characterization of Produced Nanocarbon XRD analysis TEM analysis 105 xi FESEM analysis Summary of Major Findings PART 3: METHANE DECOMPOSITION KINETICS AND REACTION RATE OVER n-nio/sio2 CATALYST Establishment of Carbon Deposition in Methane Decomposition over n-nio/sio2 Catalyst Influence of Methane Partial Pressure and Decomposition Temperature Methane Decomposition Kinetics over n-nio/sio2 Catalyst Summary of Major Findings PART 4: GOVERNANCE OF POROSITY AND METHANE DECOMPOSITION ACTIVITY SUSTAINABILITY OF n-nio/sio2 CATALYST BY CHANGING SYNTHESIS PARAMETERS XRD Nitrogen Adsorption Desorption Measurements H2-TPR TEM and EDX Thermocatalytic Methane Decomposition Summary of Major Findings 148 CHAPTER 5: CONCLUSION AND RECOMMENDATION FOR FUTURE STUDIES CONCLUSIONS 149 xii 5.1.1 Part 1: Stabilization of Ni, Fe, and Co Nanoparticles through Modified Stöber Method to Obtain Excellent Catalytic Performance: Preparation, Characterization, and Catalytic Activity for Methane Decomposition Part 2: Probing the Differential Methane Decomposition Behaviors of n-nio/sio2, n-feo/sio2, and n-coo/sio2 Catalysts Prepared through Co-precipitation cum Modified Stöber Method Part 3:Methane Decomposition Kinetics and Reaction Rate over n-nio/sio2 Catalyst Part 4: Governance of Porosity and Methane Decomposition Activity Sustainability of n-nio/sio2 Catalyst by Changing Synthesis Parameters 5.2 OVERALL CONCLUSIONS RECOMMENDATIONS FOR FUTURE STUDIES 153 REFERENCES 154 Appendix A 174 Appendix B 175 Appendix C 177 Appendix D 179 Appendix E 181 Appendix F 183 xiii LIST OF FIGURES Figure No. Title Page Figure 1.1 Worldwide hydrogen production by sources. 2 Figure 1.2 Schematic representation of the sources, preparation methods and utilization of hydrogen. 4 Figure 2.1 Sector-wise usage of hydrogen. 11 Figure 2.2 Figure 2.3 Influence of reaction temperature on the evolution of hydrogen concentration at space velocity 120 lg 1 cat h 1 Influence of space velocity on the evolution of hydrogen concentration at temperature 700 C Figure 2.4 Mechanism proposed for hydrocarbon decomposition on Ni catalysts. 30 Figure 2.5 a) Image of the carbon based honeycomb monoliths; b) Drawing with the geometric parameters of the monolithic structure. 37 Figure 2.6 SEM images of carbon produced from methane decomposition on different NCB at 850 C: (a) untreated NCB; (b) Ni/NCB; (c) Co/NCB; (d) Pd-Ni/NCB. 46 Figure 2.7 Methane conversion (mol%) over AC supported a) Pd and b) Ni catalysts (T = 850 C, VHSV = 1.62 l/h.gcat). 48 Figure 2.8 The nucleation and growth process of the fibrous carbon deposits described by SEM images: (a) 15 min, (b) 30 min, (c) 45 min, (d) 60 min, (e) 90 min, and (f) 10 h in the TCD of methane over AlRC sample. 50 xiv Figure 2.9 Thermogravimetric decomposition of methane over metal and carbon catalyst. 53 Figure 3.1 Schematic representation of the synthesis of nano-metal oxides and nano-metal oxide/silicates. 66 Figure 3.2 Simplified schematic visualization of methane decomposition unit. 70 Figure 4.1 XRD patterns of a) n-nio and n-nio/sio2, b) n-feo and n- FeO/SiO2, and c) n-coo and n-coo/sio2. 78 Figure 4.2 N2-adsorption desorption isotherms of a) n-nio, b) n- NiO/SiO2, c) n-feo, d) n-feo/sio2, e) n-coo, and f) n- CoO/SiO2. 81 Figure 4.3 Schematic representation of the method for evaluation of XRD crystal size and BET particle size for nano metal oxide before and after silicate support. 82 Figure 4.4 TEM images of a) n-nio, b) n-nio/sio2, c) n-feo, d) n- FeO/SiO2, e) n-coo, and f) n-coo/sio2. 85 Figure 4.5 EDX mapping and elemental composition of a) n-nio, b) n- NiO/SiO2, c) n-feo, d) n-feo/sio2, e) n-coo, and f) n- CoO/SiO2. 86 Figure 4.6 H2-TPR profile of a) n-nio and n-nio/sio2, b) n-feo and n-feo/sio2, and c) n-coo and n-coo/sio2. 87 Figure 4.7 Production of hydrogen (in percentage) during temperature programmed methane decomposition over 1g of n-nio, n- NiO/SiO2, n-feo, n-feo/sio2, n-coo, and n-coo/sio2 catalysts. Temperature ranged between 200 to 900 C with a flow rate of 0.64 L/min. 90 xv Figure 4.8 XRD patterns of a) n-nio and n-nio/sio2, b) n-feo and n- FeO/SiO2, and c) n-coo and n-coo/sio2 after TPMD. Peaks corresponds to graphitic carbon, Ni, Fe3C, and Co are indicated. Figure 4.9 TEM images of nano-catalysts after TPMD. a) n-nio, b) n- NiO/SiO2, c) n-feo, d) n-feo/sio2, e) n-coo, and f) n- CoO/SiO Figure 4.10 Figure 4.11 Figure 4.12 Hydrogen formation percentage during isothermal methane decomposition over a) n-nio/sio2, b) n-feo/sio2, and c) n- CoO/SiO2 catalysts at different temperature. Flow rate = 0.64 L/min and catalyst weight = 0.5 g. Methane decomposition over n-nio/sio2 catalyst at different methane feed flow rate. Temperature = 550 C and catalyst weight = 0.5 g. Comparison of calculated carbon yield in percentage produced over respective catalyst at 700, 600, and 500 C Figure 4.13 XRD patterns of a) n-nio/sio2, b) n-feo/sio2, and c) n- CoO/SiO2 after isothermal methane decomposition at different temperature. Peaks corresponds to graphitic carbon, Ni, FeO, Fe3C, and Co are indicated. Figure 4.14 TEM images of produced nanocarbon over n-nio/sio2 at a) 700, b) 600, and c) 500 C Figure 4.15 TEM images of produced nanocarbon over n-coo/sio2 at a) 700, b) 600, and c) 500 C. 106 Figure 4.16 TEM images of produced nanocarbon over n-feo/sio2 at 700 C. 107 Figure 4.17 FESEM images of produced nanocarbon over n-nio/sio2 catalyst at a) 700, b) 600, and c) 500 C. 109 xvi Figure 4.18 The diameter distribution histogram of nanocarbon produced over n-nio/sio2. Diameter of 50 nanocarbons were measured with ImageJ software. 110 Figure 4.19 Methane decomposition rate (RCH 4 ) vs. reaction time over n- 116 Figure 4.20 NiO/SiO2 catalyst at different partial pressure (0.2, 0.4, 0.6, and 0.8 atm) at temperature a) 650, b) 600, and c) 550 C, respectively. Activity loss in percentage at each temperature and methane partial pressure after 1.5 h of activity examination. 117 Figure 4.21 Figure 4.22 Accumulation of carbon with time over n-nio/sio2 catalyst at different temperatures (650, 600, and 550 C) at methane partial pressure (PCH 4 ) a) 0.2, b) 0.4, c) 0.6, and d) 0.8
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