The Design Of Graphene-Based Nickel Catalyst And Catalytic Performance For Methanation Of CO₂

Graphene has become another legend of the carbon materials family, due to its unique physics, chemistry and mechanics properties, which make it has wide application prospect in catalysis. The graphene with larger specific surface area was uses as carrier in this work, high performance of non-noble metal nickel used as active component, with manganese and rare earth elements as additives, the different kinds of graphene based nickel catalyst were prepared for the methanation of carbon dioxide. Three parts of the work were carried out:1. First, graphene oxidation(GO) dispersion were prepared using use the graphite powder via improved Hummers method. Then, GO was reduced with NaBH4, and nickel salt was used to prepare the graphene based nickel catalyst. The catalytic evaluation for carbon dioxide methanation show that the catalysts with 10%nickel is the best. FTIR, XRD, BET and TEM methods were used to characterize the catalysts. Reduced of graphene oxide(RGO) have larger specific surface area, which is a kind of good catalyst carrier. Nickel particles were successfully supported on graphene layers, while some of them grow into larger particles. Further modified to improve dispersion of nickel is needed.2. Using hydrazine hydrate reduced RGO, NiCl2·6H2O and urea as support,precursor and hydroxyl relievers, respectively. The 10% Ni/RGO catalyst was prepared using deposition precipitation methods. The second manganese metal was also added for modification. The catalysts with different nickel/manganese ratio Ni-Mn/RGO(nNi:nMn=1:1/ 2:1/3:1) were also prepared and tested for the CO2 methanation reaction.it shows that that the best ratio of nickel/manganese ratio is n(Ni): n(Mn) = 2:1. XRD, BET, H2-TPR, SEM, TEM characterization results show that the second component of manganese metal added can promote the dispersion of the active component of nickel, hindered the NiO reunion on the RGO for larger particles, which made the nickel grain refinement and reduction component increases.Nickel and manganese compound also can effectively prevent the sintering ofcatalyst, and the low temperature activity of the catalyst increased significantly.3. Using RGO, nickel nitrate ethanol solution as support and precursor,respectively. The Ni/RGO with 1% rare earth, Ce, La, Nd and Y were prepared using immersion method. The activity and stability of the prepared catalysts were tested for CO2 methanation. It was found that Ce doped catalyst(Ni-Ce/RGO) show the best activity, especially at low temperature. Characterization results show that the addition of rare earth improved the dispersion of nickel and reduced the strong interaction between the active component Ni and RGO. The addition of the active ingredients in the catalysts, promotes the adsorption and dissociation of the reactants.Above all, this paper aims to obtain a graphene based nickel catalysts with high activity and thermal stability for the CO2 methanation reaction. Our results show that the catalyst with 10% nickel is the best. The second metal components such as,manganese and rare earth additives could improve the performance of the cataltysts to some extents. Especially 10%Ni-Mn(2:1)/RGO and Ni-Ce/RGO show high catalytic activity. Detailed characterization methods were carried out to reveal the interaction of graphene and the supported active components.