Studies in Surface Science and Catalysis 130 A. Corma, F.V. Melo, S. Mendioroz and J.L.G. Fierro (Editors) 9 2000 Elsevier Science B.V. All fights reserved. 989 Synthesis of high surface area transition metal carbide catalysts A.P.E. York, J.B. Claridge, V.C. Williams, A.J. Brungs, J. Sloan, A. Hanif, H. AI-Megren and M.L.H. Green Wolfson Catalysis Centre, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QR, U.K. The synthesis of molybdenum and tungsten carbide from their oxides using the temperature programmed reaction method with methane and ethane is presented. Lower reaction temperatures are required for metal carbide formation with ethane, and the highest surface areas materials are also prepared by this method. In addition, the use of the different hydrocarbons enables synthesis of various phases of molybdenum or tungsten carbide. Thermogravimetric analysis studies demonstrate that the carbide formation mechanisms for the two transition metal carbides in ethane differ. Finally, a similar technique has been employed for the synthesis of uranium monocarbide with moderately high surface area. I. INTRODUCTION High surface area transition metal carbides are active catalysts for a wide range of reactions, including hydrodesulphurisation (HDS), hydrogenation, Fischer-Tropsch synthesis, hydrocarbon isomerisation and methane oxyforming [1-5]. Synthesis of these potentially important materials has attracted considerable attention over the years, and a number of procedures have now been described for the production of carbides with surface areas suitable for catalyst materials (i.e. > 30 m E g-l) [6]. The most commonly employed method is temperature programmed reaction (TPRe) of metal oxide with a hydrocarbon (usually methane), which was developed by Boudart and co-workers [7-9]. In spite of all the interest in these materials, comparatively few detailed studies of the material synthesis have been reported. Indeed, it may be possible to prepare carbides with improved properties by modification of already known methods. For example, replacement of methane by ethane for TPRe should lead to higher surface areas due to the more reactive nature of the latter hydrocarbon; the carbon activities can be expressed by the following equations, respectively (1 and 2) [ 10]. dC -- )2 (1) =I I___L__. ar )3 (2)