Sulfur-Emission-Free Process of Molybdenum Carbide Synthesis by Lime-Enhanced Molybdenum Disulfide Reduction with Methane

Abstract

To investigate a sulfur-emission-free process of molybdenum carbide synthesis from molybdenite, the reaction pathways of MoS(2) reduction with methane in the presence of lime (CaO) have been studied. A mixture of MoS(2) + 2CaO was reduced isothermally with CH(4) in a microreactor, and the composition of effluent gases and the reduced fraction were determined as a function of reaction time. Analysis of the solid phase at different reaction tines at 800 degrees C showed the formation of CaMoO(4) as an intermediate phase. Hence, the reaction pathways proposed for reduction of MoS2 + 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(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. Carbon content of solid sample increased with reduction time, and in fully reduced sample at 800 degrees C it was well above the stoichiometric amount indicating considerable excess carbon deposition due to CH(4) cracking.