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A study on hydrogen production via dry methane reforming using catalytic proton-conducting ceramic membrane reactors

초록/요약

A major challenge for dry reforming catalytic reaction, which occurs when producing hydrogen and carbon monoxide from methane and carbon dioxide, is improving the performance and stability of the catalyst in a relatively low temperature. With growing interest in utilizing hydrogen as a clean energy source, various catalysts and processes using the two greenhouse gases to produce and separate hydrogen have been researched. An integral membrane catalytic reactor that can be used has the advantage that the system components can be significantly reduced. Deactivation caused by carbon deposition of nickel catalyst in dry reforming reactions is closely related to catalyst support, preparation method, and the size of nickel particles on the surface of the catalyst. Such conditions are important factors in ensuring catalytic activity. Moreover, a dry reforming catalyst utilizing proton conductive ceramic can also produce hydrogen and separate hydrogen optionally. In this thesis, a proton conducting ceramic with a perovskite structures ware selected as the support to overcome the deactivation of carbon deposition of nickel catalysts in methane and carbon dioxide reforming in order to dope the nickel in a well-defined structure. In addition, to scale up the catalytic process, structural catalysts were prepared to evaluate performance and stability. Moreover, the feasibility of the membrane catalytic reactor was evaluated through combining hydrogen-producing catalyst and membrane capable of selectively permeating hydrogen. The reforming reaction of methane and carbon dioxide used nickel-based catalyst. First, BaZrO3, a proton conductive ceramic, was used as a support and nickel was supported on various conditions to prepare the catalyst. At this time, nickel was applied by temperature regulated chemical vapor deposition (TR-CVD) to allow nickel nanoparticles to be deposited on the surface of the support. Conformal nickel nanoparticles were formed on the BZO surface, and the Ni/BZO catalyst showed high catalytic activity and excellent stability even at low temperatures. As for BaTiO3 and BaCeO3 supports, which are other proton conductive ceramics, showed Ni/BZO catalysts predominated not only for catalyst activity but also for physical and chemical stability. As a result, the high ionic conductivity of the BZO support and the structural properties of nickel supported on the BZO suggest that -OH or -O species play an important role in promoting the oxidation of surface carbon species and forming CO and CO2. The Ni/BZO powder catalyst was prepared as a structural catalyst by extruding the BZO powder. Nano-Ni formed on the BZO structure by TR-CVD method, and the feasibility for scale-up was evaluated through comparison with the powder catalyst. Compared to the powder catalyst, the structural catalyst had a specific surface area of about 20%, which reduced the activity about 5% at same conditions, but showed a stable performance even for a long time similar to that of the powder catalyst. However, the decrease in catalyst performance with increasing space velocity was greater than that of the powder catalysts, which maybe was due to the decrease in catalyst specific surface area. Thus, the difference in reaction rates was caused by the decrease in catalytic active site. A membrane catalytic reactor was prepared for BaZr0.8Y0.16Zn0.04O3 by adding two additives to enhance the high temperature sintering and chemical stability of BZO, and this showed excellent sintering characteristics within 1350 oC. A porous catalytic layer was formed on top of the dense membrane, and the same BZYZ ceramics were used to link the proton's migration path. The thickness of the dense membrane was about 80 μm, and the hydrogen produced through the dry reforming reaction in the Ni/BZYZ catalytic layer was found to have the permeability of 0.0398 ml/cm2·min at 800 oC. In particular, the permeability of hydrogen showed a close relationship with the partial pressure between the membranes, and the permeability advanced with increasing the flow rate of sweep gas. In addition, the membrane dry reforming performance was found to be superior to the membrane reactor compared to the packed bed reactor. In conclusion, asymmetric membrane catalytic reactors using proton conductive ceramics were able to produce and separate hydrogen through a dry reforming reaction. Therefore, this enabled us to explore potential applications to dry reforming catalysts utilizing proton conducting ceramics and the separation of hydrogen produced in the reactions.

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목차

CHAPTER Ⅰ
1. Introduction 1
2. Literature Review 3
2.1 Review of Studies on Dry Reforming of Methane 3
2.1.1 General Background 3
2.1.2 Carbon Deposition over Ni-supported Catalyst during DRM 9
2.1.3 Catalytic Parameters for High Performance of DRM 11
2.2 Proton Conducting Materials and Hydrogen Permeable Membrane 26
2.2.1 Proton Conducting Ceramic Materials 26
2.2.2 Perovskite Structure and Proton Conducting Mechanism 30
2.2.3 Hydrogen Permeable Membrane 34
2.3 Catalytic Membrane Reactor for Hydrogen Production 46
2.3.1 Design of Membrane Reactor 46
2.3.2 Ni-perovskite Catalysts for Hydrogen Production 51
2.3.3 Application of Catalytic Membrane Reactor 59
3. Objective 62

CHAPTER Ⅱ
1. Ni/Perovskite Oxide for Dry Reforming of Methane 64
1.1 Introduction 64
1.2 Experimental Methods 65
1.3 Results and Discussion 70
1.4. Conclusion 88

2. Ni/Structural Supported Catalysts for Dry Reforming of Methane 89
2.1 Introduction 89
2.2 Experimental Methods 91
2.3 Results and Discussion 95
2.4. Conclusion 106

3. Catalytic Membrane Reactor for Hydrogen Production 107
3.1 Introduction 107
3.2 Experimental Methods 110
3.3 Results and Discussion 116
3.4. Conclusion 133

CHAPTER Ⅲ
Summary 134

Reference 135
국문초록 165

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