Performance and stability in CO2 reforming of methane over neodymium nickel oxide composite catalysts

The stable nickel catalyst for CO2 reforming of methane (DRM) is an indispensable requirement for boosting the efficiency of methane conversion to synthesis gas. Herein, without using the regularly ordered porous support, neodymium-promoted nickel catalysts were synthesized by co-precipitation method (denoted as NixNd1-x catalysts, Ni/Nd = 1:9, 3:7, 5:5, 7:3 and 9:1). By regulating the Nd and Ni loadings, the nickel species in the reduced NixNd1-x catalysts could be controlled. When the Ni/Nd molar ratio was in the range of 3/7 to 7/3, NiNd2O4 predominantly existed on the catalyst surface. Once the Ni/Nd mole ratio exceeded this range, Ni species surface was covered by thick amorphous Nd2O3. The activity during DRM was studied as a function of temperature (550–800 °C) and time on stream (750 °C, 24 h). Although carbon deposition increased with the nickel loading, the produced carbon did not block the porous structure in the spent Ni5Nd5 and Ni7Nd3 catalysts. A fraction of the nickel segregating on the spent catalyst surface to become the active site ensured Ni5Nd5 and Ni7Nd3 catalysts having the most active and stable catalytic performance. The activity results correlated well with the higher surface area of the starting NixNd1-x catalysts, the smaller Ni crystallite sizes, and structural reconstructions during the DRM reaction.