Reduction of Molybdenite with Methane in the presence of Lime Samad Ghasemi Najafabadi samad_ghasemi@yahoo.com March 2, 2011 Department of Materials Engineering Isfahan University of Technology, Isfahan, 84156-83111, Iran The thermodynamics and kinetics of molybdenite (MoS 2 ) reduction with methane in the presence of lime (CaO) has been investigated. The thermodynamic investigation resulted in construction of stability diagrams of molybdenum compounds. In addition to stability regions of Mo, Mo 2 C and MoC, the carbon deposition area was also identified. A U-shaped quartz micro-reactor was used for MoS2 reduction with CH4 in the presence of lime. The effluent gases were analyzed quantitatively by an online gas chromatograph. The reduced fraction was determined as a function of time by noting the gas flow rate and concentration of oxygen-containing gases. Analyzing the partially reduced solid phase showed the formation of CaMoO 4 as an intermediate phase. Hence, the mechanism proposed for reduction of MoS 2 +CaO with CH 4 involves the direct reduction of MoS 2 with CH 4 to form Mo 2 C and sulfur-containing gases. The sulfur-containing gases are captured by CaO to form CaS, CO(g), CO 2 (g) and H 2 O(g). The unreacted MoS 2 is oxidized by CO(g), CO 2 (g) and H 2 O(g) to form MoO 3 (g), which reacted with CaO to form CaMoO 4 on CaO particles. Finally, CaMoO 4 and remaining MoS 2 are further reduced with CH 4 . Characterization of solid samples was carried out by XRD, CHN and FE-SEM equipped with EDS, providing results consistent with the proposed reaction pathways. The results of isothermal kinetic analysis was in consistence with the 2-step proposed mechanism. In the first step, CaMoO 4 is formed according to power law kinetic model with the activation energy of 95kJ/mol. In the second step of reaction, the as formed CaMoO 4 and remaining MoS 2 were reduced with CH 4 and the results were fitted to tridimensional diffusion model and the calculated activation energy was 10kJ/mol. Keywords : Molybdenite, Reduction, Methane, Lime, Thermodynamics, Kinetics [1]
