CO2 reforming of methane over Pt–Ni/Al2O3 catalysts: Effects of catalyst composition, and water and oxygen addition to the feed

A series of Pt–Ni bimetallic catalysts supported on δ-Al2O3 to be used in carbon dioxide reforming of methane was prepared and tested with the objective of optimizing the Ni/Pt metal composition to obtain high activity and stability. Selected catalyst samples, before and after reaction, were characterized by XRD, XPS, TGA/DTA and SEM-EDS. The activity results showed that the catalytic performance of bimetallic Pt–Ni samples strongly depended on the metal loadings and Ni/Pt loading ratio. Among all the catalysts, 0.3%Pt–10%Ni/Al2O3, which has the lowest Ni/Pt ratio, exhibited the highest catalytic activity and stability. The combined characterization and catalyst performance tests results reveal that low Ni/Pt molar loading ratio of 0.3%Pt–10%Ni/Al2O3 sample led to a relatively easy reduction of nickel oxide species and smaller nano-sized nickel particles having better dispersion caused by the intimate interaction between Pt and Ni sites in the closed vicinity. The changes in the catalysts’ activity and stability under the presence of an additional oxygen source were determined through addition of small amounts of either oxygen or water vapor to the feed stream. The results of the combined dry reforming and partial oxidation tests strongly indicated a change in surface reaction mechanism depending on the Pt load and Ni/Pt ratio of the catalysts. 0.3Pt–10Ni was capable of operating under a variety of feed conditions without significant deactivation suggesting that the catalyst is very promising for synthesis gas production for gas-to-liquid technology.