空气焙烧-碱浸法回收废加氢催化剂中的钼和钒

Recovering molybdenum and vanadium from spent hydroprocessing catalyst by air roasting-alkaline leaching process

废加氢催化剂中含有大量的有机污染物和金属元素,如钼、钒、镍和铝,若处理不当,会造成严重的生态污染和资源浪费。本研究采用空气焙烧-碳酸钠浸出法处理废弃加氢催化剂以回收其中的钼和钒。通过热力学计算可知低温碳酸钠浸出可以实现废催化剂中钼、钒与铝、镍的分离。单因素实验考察了空气焙烧温度、碳酸钠浓度、反应时间、浸出温度、液固比等工艺条件对钼和钒浸出率的影响。实验结果表明,在焙烧温度500℃,碳酸钠浓度4 mol/L,浸出温度80℃,反应时间90 min,液固比为20:1的条件下,钼和钒的浸出率可分别达到98.02%和94.36%。为了最大限度地回收钼和钒,采用二段逆流浸出流程处理废加氢催化剂,可将钼和钒的浸出率维持在98%和97%。浸出渣中主要含有Al_(2)O_(3),NiO和NiAl_(26)O_(40),而绝大部分钼和钒被转移至浸出液中。

With the rapid development of oil refining industry,the annual generation of global spent hydroprocessing catalysts is gradually increasing.Spent hydroprocessing catalysts are rich in organic pollutants and metals including molybdenum,vanadium,nickel,and aluminum,which will lead to not only serious deterioration of ecological environment but also waste a great amount of resource.In this study,a process featured by air roasting-alkaline leaching was proposed to treat the spent hydroprocessing catalyst in the purpose of recovering molybdenum and vanadium.Thermogravimetric(TG),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS) and scanning electron microscopy/energy dispersive spectroscopy(SEM/EDS) techniques were employed to characterize the raw spent catalysts,the roasted product and the leaching residues.Air-roasting can make the metal sulfides convert to oxides which were able to be dissolved into leaching solution by sodium carbonate.Thermodynamic analysis showed that the low-temperature leaching can separate molybdenum and vanadium from aluminum and nickel in the spent catalysts.The effects of air roasting temperature,sodium carbonate concentration,reaction time,leaching temperature and liquid to solid ratio on the leaching rate of molybdenum and vanadium were investigated by the single factor experiments.The experimental results showed that the leaching rates of molybdenum and vanadium reached 98.02% and 94.36%,respectively,under the optimum conditions with roasting temperature of 500℃,sodium carbonate concentration of 4 mol/L,leaching temperature of 80℃,reaction time of 90 min and liquid-solid ratio of 20:1.In order to maximize the recovery of molybdenum and vanadium,the two-stage counter current leaching process was adopted subsequently,and the leaching rate of molybdenum and vanadium were able to maintain at 98% and 97%,respectively.The leaching residue mainly contained Al_2O_3,NiO and NiAl_(26)O_(40),and most of molybdenum and vanadium transferred into leaching solution.The advantage of this process is that molybdenum and vanadium can be fully recovered and satisfactorily separated from nickel and aluminum with the mild leaching conditions,which is benefit for the following treatment of leaching residues.