Kinetics of Formation of Molybdenum Carbide (Mo2C) by Reaction between Carbon Monoxide and Molybdenite or Molybdenum

Abstract

Investigations have been conducted on the reactions between molybdenite (technical grade MoS2) and molybdenum metal powders with carbon monoxide in the temperature range 1123 to 1298 K. The rates of both MoS2+CO and Mo+CO reactions have been found to increase significantly with temperature. XRD examination of the reaction products reveal the formation of Mo2C directly by the reduction-carburization of MoS2. The said carbide is also observed to be the dominant product of molycarburization (Mo+CO) reaction. The MoS2 conversion has been found to be a slow process, whose results fit into a linear rate law with a high activation energy value (230 kJ mol−1). In contrast, the carburization of Mo powder has been observed to be a fast process, initially rapid upto about 30% conversion and subsequently progress in accordance with parabolic kinetics (low activation energy values of 76 and 33.5 kJ mol−1, respectively for initial and parabolic stages). Since no elemental Mo has been detected in the products of the MoS2+CO reaction, it is not possible to separate it from the subsequent in-situ molycarburization (Mo+CO) reaction. An indepth analyses of the findings indicate that the linear kinetics and the high activation energy value (230 kJ mol−1) determined for the overall reduction-carburization of MoS2 may pertain to the pre-requisite reaction (namely, MoS2+2CO=Mo+2COS) itself.