Thermocarburization Synthesis of Silica-Supported Mo2C Catalyst Using H2/Propane Mixture

Transition metal carbides have properties similar to platinum group metals and their synthesis procedure have been the subject of recent patents. This paper deals with the synthesis of Mo2C from the propane carburization of silica supported MoS2. BET surface area was strongly favoured by increased temperature and H2:C3H8 ratio but to a lesser extent by carburization time. Based on statistical analysis, optimum conditions were identified as H2:C3H8 = 1, temperature at 973 K for a period of 1 hour. Surface area also decreased almost hyperbolically with Mo loading. FTIR analysis suggests the presence of co-ordinatively adsorbed NH3 molecules implicating the existence of weak Lewis acid centres with an optimum concentration at about 12% Mo content. The solid-state reaction kinetics was investigated by thermogravimetry. The carburization appeared to follow a 2nd order kinetics but characterised by a low activation energy of 16 kJ mol-1 indicative of a diffusional solid-solid rate controlling step involving interstitial substitution of carbon with sulphur atoms in the Mo matrix.