Investigation of Reaction Networks and Active Sites in Bio-ethanol Steam Reforming over Cobalt based Catalysts

Hydrogen is likely to play an important role in the energy portfolio of the future. Especially when it is used in fuel cells, it is an ideal energy carrier that can offer clean and efficient power generation. In the United States, ~95 % of hydrogen is produced using a steam reforming process [1]. Over 50% of world’s hydrogen production relies on natural gas as the feedstock [2]. As the concern for a sustainable energy strategy grows, replacing natural gas and other fossil fuels with renewable sources is gaining new urgency. In this context, producing hydrogen from bio-derived liquids such as bio-ethanol has emerged as a promising technology due to the low toxicity, ease of handling and the availability from many different renewable sources (e.g., sugar cane, algae) that ethanol has to offer. An added advantage of producing hydrogen from bio-derived liquids is that it is quite suitable for a distributed production strategy. In this study, the effects of metal loading, preparation methods, synthesis parameters, cobalt precursors, impregnation medium, promoters and supports as well as reaction conditions are investigated for steam reforming of bioethanol and other bio-derived liquids over Co-based catalysts. In addition to these effects, the reaction networks and catalytic active sites are evaluated through steady state reaction using Gas Chromatography (GC)-Mass Spectrometer (MS) as analytical tools. Characterization studies have been performed by employing versatile characterization techniques such as Temperature Programmed Reaction (TPRxn), Temperature Programmed Reduction (TPR), Temperature Programmed Desorption (TPD), Temperature Programmed Oxidation (TPO), N2 Physisorption, Pulsed Chemisorption, X-Ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), Laser Raman Spectroscopy (LRS), Thermogravimetric Analysis-Differential Scanning Calorimetry (TGA-DSC), Isotopic Labeling, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) to gain insights to the catalyst structure and its variations at different life stages on a microscopic level, leading to the proposal of possible reaction pathways and identification of the probable catalytic active sites. Integrated with the experimental results obtained, the predictions from molecular simulation are expected to theoretically guide the catalyst formulation with improved catalytic properties. In addition, the work also involves the deactivation mechanism exploration and strategy for sample regeneration in order to extend the catalyst lifetime. Furthermore, the economic analysis of this technique is performed from feedstock to final product ready for distributed usage, which will be beneficial for industrial applications. According to the results acquired in this research, the relationship between surface and structural properties (e.g., cobalt dispersion and oxygen availability) and activity has been initially established to facilitate rational design of catalyst systems for the steam reforming reactions studied. H2 yields over 90 % have been achieved at relatively lower temperatures ( Combined with the estimated economic analysis of this process simulated at industrial scale, the outcomes originating from this study will eventually lead to the commercialization of the developed catalyst system specially tailored for central and distributed hydrogen production from steam reforming of bio-derived liquids suitable for fuel cell application.