James J. Chludzinski

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

Abstract 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 H 2 O H 2 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.

Platinum, barium and platinum-barium catalysed gasification of graphite in steam and CO2

The concept of forming a bifunctional catalyst system for the gasification of carbon was investigated using controlled atmosphere electron microscopy. Platinum and barium were chosen as the catalyst components and their effect has been studied, both in separate and combined forms, on the gasification of graphite in steam and CO2. Platinum was found to operate in both systems primarily by the channelling mode but was not very active and was susceptible to deactivation at temperatures 900 °C in a steam environment. This deactivation phenomenon is believed to arise from carbon deposition or precipitation during the reaction. In contrast, previous studies have shown that barium is a relatively active catalyst for both these reactions and operates predominantly by the edge recession mode. The mixed platinum-barium catalyst only exhibited channelling activity, but the intrinsic rate indicated that it probably functions as a true bifunctional catalyst with barium increasing the oxygen reactivity, and platinum the carbon reactivity. The results of this study demonstrate the potential of multicomponent catalysts in which the components are selected by their ability to enhance the rate of one particular step in the reaction scheme.