The role of NaCl in chlorine roasting of MoS2

This work presents the results obtained on the role of NaCl in chlorine roasting of MoS2. The process was performed in an oxygen atmosphere in the temperature range from 350 to 500 degrees C. The chlorine roasting of MoS2 in the mixture with NaCl was analysed and the products and change in the NaCl surface topography occurring during the processing were detected by x-ray diffractometry and Scanning Electron Microscopy (SEM), respectively. At a temperature below 400 degrees C chemical activity of NaCl resulted in a change of NaCl surface topography. However, only MoO3 was detected. At a temperature above 400 degrees C Na2Mo2O7, Na2SO4 and MoO3 were detected, as well as the melt around NaCl particles. Evaporation and condensation on cold wall of reaction tube of some compounds containing molybdenum and chlorine were also detected. Such phenomena will not occur if oxidation takes place without NaCl or MoS2/NaCl mixture is annealed in an inert atmosphere. This indicates that all detected phenomena were caused by NaCl reactions with products of oxidation of MoS2 and chlorine roasting of MoS2 occurred in the melt.