Partial Oxidation Of Methane To Synthesis Gas Catalyzed By Metallic Ni Catalysts

Synthesis gas is mainly produced by steam reforming of methane, which has several shortages, such as high energy intensity, easy carbon deposition, and moreover provides syngas with a higher H2/CO ratio than that required for several processes. Because of its low investment, less energy consumption and instant reaction rate, partial oxidation of methane has attracted much attention. In this work, metallic Ni catalysts were prepared with Ni foam and further treated by acid. The reaction scheme of the partial oxidation of methane to synthesis gas over metallic Ni catalysts was investigated. The metallic Ni catalyst was further promoted by metal oxides, such as yttria, zirconia, magnesia, or the mixture of them. The catalysts were characterized by ICP, XRD, XPS, SEM, H2-TPR, N2 physical adsorption, etc. and studied in the partial oxidation of methane to syngas and the combined partial oxidation and steam or CO2 reforming of methane. In addition, a novel nickel nanowire catalyst was prepared, characterized with XRD, XPS, H2-TPR, TEM, and N2 physical adsorption, and the catalytic properties were compared with the metallic Ni catalyst in the partial oxidation of methane.It has been found that in the absence of significant mass and heat transfer resistances, high selectivities to synthesis gas were obtained on the metallic Ni catalyst even in the low methane conversion range. The results indicated that the reaction of partial oxidation of methane to syngas over the metallic Ni catalyst might follow the direct reaction scheme.The optimum loadings of Y2O3, ZrO2, and La2O3 were 3.17 wt.%, 0.84 wt.%, and 1.32 wt.%, respectively. SrO did not show any promotion effect on the metallic Ni catalyst. 1.03Zr-0.11Y/Ni showed not only high activity but also high selectivities. BET results showed that after loading oxides the surface area of the metallic Ni catalysts increased. The results of SEM showed that the metal oxides were loaded on the surface of the catalysts. XRD and H2-TPR results showed that Zr/Ni, Y/Ni, and Zr-Y/Ni had more NiO phase than in the metallic Ni catalyst. XRD and XPS results showed that Zr4+, Y3+, and Ni2+ could dissolve in each other. After further loading MgO, the CH4 convertion on Zr/Ni, Y/Ni, and Zr-Y/Ni increased, but the selectivities to syngas did not change appreciably. The change of the amounts of MgO had no appreciable influence on the activities of these catalysts.The results of the combined partial oxidation and steam or carbon dioxide reforming of methane on Y/Ni, Zr/Ni, and Zr-Y/Ni showed that the addition of steam promoted the production of hydrogen, which might result from the water gas shift reaction; the addition of carbon dioxide promoted the production of carbon monoxide, which might result from the reverse water gas shift reaction.The study results on the nickel nanowire catalyst showed that the catalyst consisted of uniform length and width of nanowires, having a high BET surface area and narrow pore size distribution. The nickel nanowire catalyst exhibited high activity and high selectivities in the partial oxidation of methane to syngas.