Preparation And Catalytic Performances Of CeO₂Doped In Ni-based Catalysts In Methane Decomposition

In a fusion reactor, the helium gas and other impurities will increase by increasing of operation time. Under the consideration of environmental protection and economic point, the gas was need to be discharged from reactor to purify. Combined with the composition of plasma ehaust, methane catalytic decomposition become the main direction of the research to recycle the deuterium and tritium existed in compound.The primary target of this paper is to design the high-performance catalyst for methane catalytic decomposition reaction. The different CeOr-doped Ni-based catalysts were synthesized by the method of sol-gel, coprecipitation and impregnation, then characterized by XRD、XPS、 SEM SEM-EDX and TEM. Meanwhile, the catalytic performances of different CeO2-doped in Ni-based catalysts were characterized in a system of fixed bed. The structures of Cs produced in reaction were then characterized by SEM、TEM and Raman. It is the first time to investigate the the relationship between the structure and catalytic activity of CeO2-doped in Ni-based catalyst. Analyzed the results of research, the main conclusions are as follows:1) The introduction of Ce into Ni-based catalysts increased the catalytic activity, The introduction of Cu increased the stability of catalyst.2) Three CeO2-doped in Ni-Cu catalysts with different microstructure were synthesized by coprecipitation, CP-NaOH-R, CP-NH3-R and CP-urea-R. The structures of CP-urea-R and CP-NH3-R are closed to NiCuCeOx contained Ni-Cu-Ce-O solid solution. However, the structure of CP-NaOH-R is closed to NiCu/CeO2. Meanwhile, CP-NaOH-R showed a much higher catalytic activity for methane decomposition and could be deposited by carbon rapidly. However, the reaction was stopped by carbon deposition. CP-NH3-R initially showed a low methane conversion rate, about28%, followed by a rapid decrease in hydrogen production within200min. CP-urea-R had the longest catalytic lifetime, and methane conversion slowly decreased from42%to10%within400min.3) The NiCuCeOx catalysts with different microstructure were synthesized by coprecipitation with urea under different conditions. Then their physicochemical properties and catalytic performances in methane decomposition were characterized. In regard to catalytic behaviors influenced by microstructure of NiCuCeOx catalysts, high Ni content increased the highest conversion of methane and induced to form amorphous carbons encapsulated the catalyst that deactivated catalyst rapidly. High Cu content in NiCuCeOx catalysts was also considered to increase the tendency of amorphous carbons. Meanwhile, Ni-Cu-Ce-O solid solutions which obtained by increasing Ni content and decreasing Ce content in catalyst enhanced catalytic lifetime. At the same time, it was also speculated to increase the tendency to form well-proportioned carbon filaments..4) The NiCu/CeO2catalysts with different microstructure were synthesized by impregnation method. It is found that the catalytic activity and stability of all catalysts were poor, which can be attributed to low adhesive force between CeO2and active component.