| Popis: |
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. |
