Experimental Study of Self-Sustained Electrochemical Promotion Catalysts for Heavy Hydrocarbon Reforming

of a doctoral dissertation at the University of Miami. Dissertation supervised by Professor Xiangyang Zhou. No. of pages in text. (230) Hydrogen production from reforming bio-fuels is considered as one of the major ways of utilizing renewable energy sources. Conventionally, most reforming catalysts are noble metal catalysts with high operation temperature above 1000 °C, which result in low thermal efficiency, long start-up time and use of high grade materials. These reasons hinder the development of hydrogen production technology. Novel self-sustained electrochemical promotion (SSEP) catalysts were developed and evaluated for heavy hydrocarbon reforming at relatively low temperatures, 450 to 650 °C. Typically, the SSEP catalysts contain NiO/Ni/CuO/Cu/CeO2 as a selective anodic phase, La0.9Sr0. 1MnO3 (LSM) as a selective cathodic phase, yttria stabilized zirconia (YSZ) as an oxygen ion conduction phase, and Ni/Cu also as an electronic conduction phase. The reforming performance of the SSEP catalysts was evaluated using a fixed bed reforming reactor for n-pentadecane. A commercially available noble metal containing catalyst, 2.4 %Pt on CeO2 support, was evaluated using exactly the same method. The following conclusions can be drawn as a consequence of this study: 1) The fuel conversion for the SSEP catalyst was 10 folds of that for the noble metal catalyst and the yield of hydrogen and carbon monoxide for the SSEP catalysts was 100 folds of that for the noble metal catalyst at 450°C. 2) The experimental results prove that this unprecedented result for the SSEP catalysts is due to the coupling of four constituent components of the SSEP catalysts, specifically, transport of oxygen ions through the oxygen ion conduction phase and transport of electrons through the electronic conduction phase between the selective anodic phase and the selective cathodic phase. This coupling gives rise to positive electrochemical potential shifting on the anode and thereby electrochemical promotion. 3) The study of the effect of each component and the effect of the concentration clearly reveals that the performance of the SSEP catalysts can be further improved to a higher level by the following ways: i) replacing the solid electrolyte, YSZ with one that has a higher oxygen ion conductivity than that of YSZ at lower temperatures; ii) replacing the cathode material, LSM with one that has a higher cathodic activity; iii) selectively depositing the anode only on the surface of the YSZ. These further verify the SSEP mechanism for the catalytic reforming process. In addition, all the catalysts were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Transmission Electron Microscopy (TEM) and Accelerated Surface Area and Porosimetry Analyzer 2020 (ASAP 2020). All solid state electrochemical sensors were also prepared. The experiments results demonstrate that the feasibility of the solid state electrochemical sensor. The new solid state electrochemical sensor is sensitive and reliable for the surface quality control.