Electron microscopy studies of the catalysed gasification of carbon

• Main Author: Harris, Peter Stephen
• Published: University of Surrey 1974
• Subjects: 541.39
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.458334

Three metal catalysts for the reaction of graphite in oxygen have been studied in detail by controlled atmosphere electron microscopy (CAEM); zinc, silver and lead. Zinc catalyses the reaction by facilitating the detachment of atoms from prismatic graphite faces only and produces channels in the graphite. The activation energy of the catalysed reaction was 70 +/- 7 kJ mole[-1], for the uncatalysed reaction it was found to be 204 +/- 15 kJ mole[-1]. Silver also allows atoms to be detached from structurally perfect basal plane surfaces which is demonstrated conclusively by use of the etch-decoration technique. It also becomes an inhibitor at high temperatures. Lead is not only intriscally very active at low temperatures but it also wets the prismatic surface of graphite which makes it very active in terms of activity per unit weight; activation energy 126 +/- 28 kJ mole[-1]. These experimental findings are consistent with the literature. The literature has been critically assessed. Confusion over the criteria for determination of the form of anisotropy in catalysed reactions has been satisfactorily resolved. Several errors in the litera-turn have been brought to light and rectified. A new development of the theory of gasification reactions generally has been proposed. A new model to account for the rates of gasification of impure and doped carbons has been derived which successfully interprets much of the published data. Finally the mechanisms of the catalysis are discussed in as close a detail as objectivity will allow.