Title Page
Abstract
Contents
Chapter 1. Introduction 12
1.1. Study Background 12
1.2. Methane dehydro-aromatization 17
1.3. Purpose of Research 19
Chapter 2. Enhanced reactivity and stability in methane dehydro-aromatization over Mo/H ZSM-5 physically mixed with NiO 21
2.1. Introduction 21
2.2. Experimental 25
2.2.1. Catalyst preparation 25
2.2.2. Catalytic experiments 26
2.2.3. Catalysts characterizations 27
2.3. Results and discussions 30
2.3.1. Methane dehydro-aromatization results 30
2.3.2. Role of NiO in the catalyst activation step 42
2.3.3. Effect of NiO on the catalyst deactivation 60
2.3.4. Discussion 75
Chapter 3. Enhanced catalytic performance via introducing silica shell on physically mixed catalyst of Mo/HZSM-5 and NiO in methane dehydro-aromatization 79
3.1. Introduction 79
3.2. Experimental 84
3.2.1. Catalyst preparation 84
3.2.2. Catalytic experiments 86
3.2.3. Characterizations 87
3.3. Results and discussions 89
3.3.1. Catalyst synthesis results 89
3.3.2. Methane dehydro-aromatization results 94
3.3.3. The effect of Silica shell on NiO 96
3.3.4. The effect of Silica shell and smaller NiO particle size by using NiO/SiO₂ 104
Chapter 4. Conclusions and summary 113
Bibliography 115
초록 119
Table 2-1. Deactivation rate of catalysts. 39
Table 2-2. CO uptake and mean diameter of Mo particles over pretreated and post-reaction catalysts. 52
Table 2-3. CO uptake and mean diameter of Mo particles over pretreated and post-reaction catalysts. 53
Table 2-4. Acid distribution of pretreated catalysts. 59
Table 2-5. TPO peak area of the post-reaction catalysts. 66
Table 2-6. BET surface area and relative decreased surface area of the pretreated and post-reaction catalysts. 72
Table 3-1. CO uptake over pretreated and post-reaction catalysts. 102
Fig. 1-1. World energy consumption and shares of global primary energy. 14
Fig. 1-2. Methane leakage rates from the natural gas system. 15
Fig. 1-3. The scheme of methane dehydro-aromatization. 16
Fig. 2-1. Catalytic performance of NiO-Mo/HZSM-5(IMP) catalysts with various Ni/Mo ratios: (a) Methane conversion, and (b) BTX yield. 36
Fig. 2-2. Catalytic performance of NiO-Mo/HZSM-5(PM) catalysts with various Ni/Mo ratios: (a) Methane conversion, and (b) BTX yield. 37
Fig. 2-3. Methane conversion and BTX yield of NiO/HZSM-5(PM) catalyst. 38
Fig. 2-4. Overall product distribution and total amounts of converted methane of the NiO-Mo/HZSM-5(PM) catalysts with various Ni/Mo ratio. 40
Fig. 2-5. The amount of cumulative H₂ production over NiO-Mo/HZSM-5(PM) catalysts with various Ni/Mo ratios during 14 h of reaction. 41
Fig. 2-6. The XRD patterns for (a) fresh catalysts, (b) pretreated catalysts, and (c) post-reaction catalysts (after reaction for 840 min). 44
Fig. 2-7. The XRD pattern for bulk NiO. 45
Fig. 2-8. CH₄-TPSR profiles of (a) Mo/HZSM-5, (b) the bulk NiO, (c) 10NiO-Mo/HZSM-5(PM), (d) 20NiO-Mo/HZSM-5(PM), and (e) 50NiO-... 49
Fig. 2-9. TEM images with diameter distribution diagram of MoCx and coke for (a) pretreated Mo/HZSM-5, (b) pretreated 10NiO-Mo/HZSM-5(PM), (c)... 54
Fig. 2-10. NH₃-TPD profiles of pretreated catalysts. 57
Fig. 2-11. FT-IR spectra for pyridine adsorption on pretreated catalysts. 58
Fig. 2-12. TEM images of post-reaction (a) 20NiO-Mo/HZSM-5(PM) and (b) 50NiO-Mo/HZSM-5(PM). 62
Fig. 2-13. TEM images and corresponding EDS mapping analysis data of C, Ni, Mo, Al and Si for post-reaction 50NiO-Mo/HZSM-5(PM). 63
Fig. 2-14. TPO profiles of the post-reaction catalysts. 65
Fig. 2-15. Raman spectra of graphite, CNT, and post-reaction catalysts. 69
Fig. 2-16. N₂ isotherm of the pretreated (left) and post-reaction (right), catalysts. 73
Fig. 2-17. BJH pore distribution of the pretreated (left), and post-reaction (right), catalysts. All figures are displayed at identical scale. 74
Fig. 3-1. TEM images of bulk NiO@SiO₂ (left) and nano NiO@SiO₂ (right). 91
Fig. 3-2. TEM-EDS images of NiO/SiO₂. 92
Fig. 3-3. TEM images of SiO₂@NiO/SiO₂. 93
Fig. 3-4. Catalytic performance of physically mixed catalysts with various Ni catalysts: Methane conversion (up), and BTX yield (down). 95
Fig. 3-5. XRD patterns of bulk NiO@SiO₂ and nano NiO@SiO₂ physically mixed catalysts (fresh, pretreated, post-reaction). 100
Fig. 3-6. CH₄-TPSR profiles of bulk NiO@SiO₂-Mo/HZSM-5 (up), and nanoNiO@SiO₂-Mo/HZSM-5 (down) 101
Fig. 3-7. TEM images of of pretreated (up 1) and post-reaction (down 2) bulk NiO@SiO₂-Mo/HZSM-5 (left), and nanoNiO@SiO2-Mo/HZSM-5(right). 103
Fig. 3-8. XRD patterns of SiO₂@NiO/SiO₂-Mo/HZSM-5. 108
Fig. 3-9. CH₄-TPSR profiles of SiO₂@NiO/SiO₂-Mo/HZSM-5. 109
Fig. 3-10. TEM-EDS images of pretreated SiO₂@NiO/SiO₂-Mo/HZSM-5. 110
Fig. 3-11. TEM-EDS images of post-reaction SiO₂@NiO/SiO₂-Mo/HZSM-5. 111
Fig. 3-12. Raman spectra of CNT and post-reaction catalysts. 112