Cyrus G. Cooper

Carbothermal synthesis of nano-sized tungsten carbide catalyst

Highly dispersed tungsten carbide particles have been obtained via low temperature -programmed propane carburization of supported tungsten sulphide. Thermogravimetric analysis showed that irrespective of support type, the solid - state conversion was a 2-step process involving the substitutionary elimination of sulphur atom to produce a tungsten carbide. The relatively low activation energy obtained (50 - 75 kJ mol -1 ) also suggested that the solid carburization was diffusion - controlled. Moreover, gas phase kinetic analysis implicated a 1 st order dependency on H 2 :C 3 H 8 ratio.

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

Abstract: 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 Mo 2 C from the propane carburization of silica supported MoS 2 . BET surface area was strongly favoured by increased temperature and H 2 :C 3 H 8 ratio but to a lesser extent by carburization time. Based on statistical analysis, optimum conditions were identified as H 2 :C 3 H 8 = 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 NH 3 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 2 nd 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.