Study On Mo Recovery Process From Spent Coal Tar Hydrogenation Mo-Fe₂O₃/Al₂O₃ Catalyst

Mo is a kind of rare metal with high economic value.In this paper,contain-oiling spent Mo-Fe₂O₃/Al₂O₃ catalyst was used as raw material,then,Mo contained in spent Mo-Fe₂O₃/Al₂O₃ catalyst of coal tar hydrogenation was recoverd by Na₂CO₃ roasting-water leaching process,and the process was optimized.The selection of solvents and methods for the de-oiling pretreatment process of spent catalyst was studied.The effects of three de-oiling methods,including the Soxhlet,the ultrasonic-assisted and the direct stirring,were compared in the de-oiling process with the nine pure solvents including n-hexane,ethanol,acetonitrile,carbon disulfide,toluene,DMF,petroleum ether,dichloromethane and ethyl acetate,respectively.It was concluded that ethyl acetate under ultrasonic-assisted conditions was optimum option.On the basis of preliminary experiments,it could be known the roasting temperature,the Na₂CO₃/sample weight ratio and the roasting time had a strong influence on Na₂CO₃ roasting-water leaching process than other factors.Single factor experiments were conducted to optimize the three operating parameters and the relationship between three variables and Mo recovery rate was obtained under different conditions.XRD patterns under different conditions were obtained to analyze the fused mixtures in the recovery procedure,and the internal causes of the three factors on Mo recovery rate were obtained.Combining with FT-IR spectra,it was concluded the optimized conditions were roasting temperature of 700?,Na₂CO₃/sample weight ratio of 2.0and roasting time of 80 min,respectively,Y_Mo could reach 90.79%under the comprehensive conditions.On the basis of single factor experiments,RSM coupled with CCD model was established,The experimental data were fitted and a second-order empirical equation was derived by multiple linear regression,furthermore,the model was proved to be effective through analysis of variance?ANOVA?.Then,it was concluded the optimum conditions were roasting temperature of 771.2?,Na₂CO₃/sample weight ratio of 2.09and roasting time of 93.56 min,Y_Mo can reach 92.58%under the optimum conditions in theory.In addition,a group of verification experiment was conducted under the optimum conditions,the experimental result was 92.19%and the relative deviation between the experimental value and the predicted value of Y_Mo was only 0.42%<2%,which further proved the validity of the model.Furthermore,ICP-AES were used to analyze the leachate of the tenth group experiment?the lowest recovery ratio?of CCD model and the verification experiment?the optimum experiment?,Si concentration in the leachate of two group experiments were 0.120 g·L^-1 and 0.107 g·L^-1,respectively.So it can be proved that the influence of Si on the subsequent extracting procedure could be negligible.Furthermore,XRD was conducted on the leaching residue under the optimum conditions,and it was found that the main phases in the residue were Ca CO₃,Ca₃Si₆O₁₂?OH?₆·5H₂O and Fe₂Al₄Si₅O₁₈,so it can be further concluded that Mo in the sample had been effectively leached.It was shown that Na₂CO₃ roasting-water leaching used in this study is effective and simple.