Study on the Synthesis of New Carbide Catalysts Supported on Active Carbon

An increasing interest has developed for the use of transition metal carbides in catalysis since analogies with noble metal catalysts have been observed. Carbides of molybdenum are known for their hardness, thermal stability and surface reactivity in heterogeneous catalysis. Bulk carbides were also found to be active in hydrodenitrogenation (HDN) of nitrogen-containing compounds such as 1,2,3,4-tetrahydroquinoline. One of the most usual way to prepare bulk transition metal carbides nowadays is the temperature-programmed reaction between bulk or supported molybdenum precursors, in flowing CH₄/H₂ (20/80) mixture. Active carbon as a support leads to a better preparation of the catalyst due to a lack of precursor-support interaction. The present objective is to get high specific surface area supported materials with low carbide-support interaction in order to get a large number of active sites accessible for HDN reactions. This paper describes a new route for preparing active carbon supported molybdenum carbides without flowing CH₄-H₂ mixture. Furthermore, this new preparation method allows to perform the synthesis of the carbide in situ in the reactor of the catalytic device, avoiding the passivation step necessary when the pyrrophoric material has to contact air between the preparation device and the catalytic reactor.