Comparison of the catalytic influence of Nickel and Cu-Ni alloys on the graphite-steam reaction

The catalytic effect of copper-nickel alloys on the graphite-steam reaction has been studied using a combination of controlled atmosphere electron microscopy and flow reactor techniques. These experiments show that the catalytic activity and selectivity of nickel can be modified by alloying with copper. However, in order for the alloy to function successfully, the H₂O H₂ ratio must be kept below 100:1, a necessary requirement to maintain the catalyst in the alloyed state. The maximum activity occurs with a catalyst containing equal amounts of the two metals. It was also found that the product selectivity in this reaction is a function of both alloy composition and reaction temperature. Methane to hydrogen ratios decrease sharply as copper is added to nickel, reaching a minimum value at a catalyst composition containing equal amounts of copper and nickel. Furthermore, the magnitude of this effect is strongly dependent on the temperature, being highest at 500 °C and tending to disappear as the temperature is raised to 700 °C.