Extraction of Molybdenum from Spent HDS Catalyst by Two-Stage Roasting Followed by Water Leaching

The petroleum refining industry produces a large amount of spent hydrodesulphurization (HDS) catalyst every year, representing a hazardous solid waste but also an important secondary resource. In the work presented herein, extraction of molybdenum from spent HDS catalyst by two-stage roasting followed by water leaching was investigated. The effects of sodium carbonate roasting and water leaching on the extraction of molybdenum as well as the effect of roasting on the molybdenum loss were investigated. The spent catalyst could be oxidized by blank roasting at 650 degrees C for 2 h with molybdenum loss of 5.9%. Under the optimized conditions of sodium carbonate roasting (blank roasted spent HDS catalyst with 20 wt.% sodium carbonate addition at 650 degrees C for 2.5 h) followed by water leaching (at 100 degrees C for 2.5 h at liquid/solid ratio of 7 mL/g), the molybdenum leaching reached 94.0%.