Microwave sodium roasting (MWSR) spent HDS catalysts for recovery Mo and in situ sulfur fixation

Abstract

Abstract The heat pretreatment of the spent hydrodesulfurization (HDS) catalysts plays an important role in its comprehensive recycling. In this work, the microwave sodium roasting (MWSR) strategy was used for the heat treatment of the spent catalyst, with the aim of achieving effective separation of Mo and Al while achieving in-situ sulfur fixation. Specifically, the de-oiled, spent HDS catalyst was roasted with Na2CO3 by microwave heating in air, followed by hot water leaching. Based on the thermodynamic analysis, the effects of microwave heating temperature, holding time and Na2CO3 addition on the recovery of molybdenum have been thoroughly investigated. Owing to the special heating method of microwave, the spent catalyst after roasting has a microstructure suitable for leaching, and S is more in situ converted to Na2CO3. After following the strategy, the leaching degree of Mo can reach 99%, while the leaching degree of Al is less than 8%, which indicates that Mo and Al are effectively separated. More importantly, a sulfur fixation degree of 79.1% was obtained. This strategy provides a novel reference for the harmless treatment of spent HDS catalysts.