The oxidative roasting of industrial spent catalyst Co-Mo/Al2O3 for the hydrotreatment of diesel fuel with lime in an air atmosphere was studied. Using the data of DTA, TG and X-ray phase analysis, it was found that during roasting, the sulfur and carbon oxides forms CaSO4 and CaCO3, and Mo is converted to calcium molybdate. Using the filtering fixed bed of reagents, the kinetics of roasting was studied. It was found that in the temperature range of 550 – 600 °C with air, supply rate of 3 l/min the process ends in 38 - 44 min for ground and non-ground catalyst. The optimal parameters (lime consumption, temperature, and time of roasting) of the absorption of sulfur oxides during roasting were determined. The degree of sulfur and carbon oxides adsorption is 96 and 36%, respectively. Separation of roasting products using unmilled spent catalyst is proposed into a small fraction (contains a mixture of CaSO4, CaCO3 and CaO) and a coarse (consists of Al2O3, CaMoO4, CoO) fractions, and their separate processing. It has been shown that in the separate processing of roast fractions by a sodium carbonate solution, it is possible to separately obtain alumina (catalyst base) with cobalt oxide, a molybdenum-containing solution, and also a mixture of sulfate, carbonate and oxide calcium. The used method of roasting the spent hydrotreating catalyst with lime will allow hazardous waste of hazard class 3-4 to be disposed of without hazardous waste gas costs. It allows one to obtain, during further processing, molybdenum and cobalt compounds, as well as finely divided alumina.
Kinetics of the Oxidative Roasting of Low Grade Mongolian Molybdenite Concentrate
