LIQUID FUEL REFORMING OVER NICKEL-MOLYBDENUM BASED CATALYSTS FOR SOLID OXIDE FUEL CELLS APPLICATION
Bkour, Qusay Yousef
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The reforming of logistic liquid fuels for fuel cell applications is a challenging proposition because of the severe carbon deposition on the surface of the reforming catalyst and sulfur problems. It becomes more challenging for a catalyst to be able to reform fuels within realistic operation conditions that are compatible with fuel cells and tolerate the influence of various aromatic and poison compounds present in these fuels. Therefore, the successful reforming of these hydrocarbons will largely depend on the development of a catalyst. Supported nickel (Ni) catalyst and molybdenum carbide (Mo2C) have attracted considerable attention because of their unique chemical and physical properties and their affordable prices. However, coking over Ni catalyst and oxidation of Mo2C catalyst are the main challenges of these two catalysts. Coke formation often leads to the rapid deactivation of Ni-based catalysts and Mo2C catalysts cannot guarantee sufficient long-term stability under liquid fuel reforming conditions due to their phase instability. This work aims to improve the coking resistance of Ni catalyst by introducing a low contraction of Mo, and improve the phase stability and the performance of Mo2C by introducing of Ni and Ti. The Ni-Mo catalyst showed high reforming activity and stability with isooctane (gasoline surrogate) conversion of 97% and H2 yield of 73% over 24 hours. Our results indicated that less degree of sintering took place for the sample with Mo. Ni-Mo catalyst was used as an internal micro-reforming layer on top of conventional Ni-YSZ anode supported single cells. By applying the Ni-Mo/YSZ catalytic internal reforming layer, the single-cell displayed significantly improved stability with a low degradation rate compared to the cell without the catalyst layer. Ni-Mo2C and Ti-Mo2C catalysts exhibited excellent stability over the 24 h test period without indication of oxidation or coking with carbon conversion of 90%, H2 yield of 56% and CO yield of 63%. The addition of Ti or Ni to Mo2C improves hydrocarbon activation, which enhances the carburization process of the carbide catalysts. Thus, the balance between the oxidation of Mo2C and carburization of MoOx can be achieve.