“Effect of Neodymium on the development of Ni supported catalysts for carbon dioxide reforming of methane.”

Abstract Rapid increase in population, growing energy demands and dependence on fossil fuels have been a major subject of discussion for researcher and scientists. Global climate changes related to the emission of greenhouse gases (CH4 and CO2) increasing rapidly due to fast consumption of fossil fuel. Therefore, for environmental protection, it is urgent to control the emission of greenhouse gases and to introduce new economic technologies for the energy production. In this work the most important issues regarding DRM reaction namely; high endothermic nature, low process efficiency and carbon deposition have been addressed by developing novel Ni based catalysts. Our main research goal is to develop Ni based catalysts operating at low temperature (600-800oC) which can further be used for other industrial application and fuel cell technology specially IT-SOFCs. The main disadvantage of Ni is the carbon formation specially at low temperature (600-800oC). Therefore, nickel catalyst supported on CeO2 and CeO2-ZrO2 solid solutions were selected due to their high oxygen storage capacity and high thermal stability. Neodymium (Nd) has been demonstrated as an effective dopant to improve the support properties, therefore, CeO2, ZrO2, and CeO2-ZrO2 supports doped with Nd are synthesized using a surfactant assisted co-precipitation method. All catalysts have been physicochemical characterized by several techniques such as isothermal N2 adsorption/desorption (BET and BJH analysis), X-ray diffraction (XRD), temperature programmed reduction/oxidation (TPR/TPO), desorption of CO2 (CO2-TPD) and CO-pulse chemisorption, elemental analysis (CHNS) and scanning electron microscopy (SEM). All catalysts were tested in dry reforming of methane reaction with a typical biogas composition (0.66) in a temperature range of 550-750°C. It has been observed that addition of surfactant (lauric acid) with surfactant/cation (S/C) molar ratio of 0.25 in the synthesis of support materials improves the morphological properties of the finally prepared catalyst. However, more prominent results regarding catalytic activity of Ni catalysts are obtained when ceria, zirconia and ceria-zirconia supports are doped with Nd compared to undoped supports. The physiochemical properties and catalytic activities of all synthesized catalysts are v compared at different and same surface area. XRD results has shown the presence of cubic fluorite structure for all ceria-based materials and Ni is well dispersed on support materials. TPR results reveals that degree of reduction of Ni/CeZrNd0.07 catalyst is higher (83%) in comparison to Ni/CeZr(53%) and Ni/CeZrNd0.2 (42%) at higher surface area. Catalytic results show that Ni/CeZrNd0.07 has highest CH4 and CO2 conversion with higher H2/CO ratio (≈ 1) and reached the thermodynamic value. This means that the co-presence of Zr and Nd inhibits the reverse water gas shift reaction and increase the H2/CO ratio. A comparative study between CeNd0.2 and ZrNd0.2 has shown that Nd affects more on the morphological and texture properties of Zr as compared to Ce. Higher catalytic activity and stability has been observed for Ni/ZrNd0.2. Long term durability tests show that all catalysts are stable and TPO analysis reveals that the gasification of carbon occurred between 450-600oC which means that the presence of Zr and/or Nd contributes to depress the carbon formation. Keywords: Neodymium doping; Ceria-Zirconia; dry reforming of methane