Efficient Recovery Of Valuable Metals From Spent Hydrogenation Catalysts

As typical solid,spent hydrogenation catalyst contains high grade valuable metals Mo,Ni,V and Al,as well as 20-40 wt%residual oil.At the same time,due to the uniqueness of spent hydrogenation catalyst itself,valuable metal elements exist in various forms such as oxides,sulfides and polymetallic complexes,which increases the difficulty of metals recovery.Therefore,efficient and green recovery of the residual oils and valuable metals deposited in spent catalyst is vital to realize the recycling of spent hydrogenation catalyst.In this work,the residual oils on the surface of spent hydrogenation catalyst were firstly removed by vacuum pyrolysis.And then,the valuable metals were extracted through air roasting-acid leaching or sulfation roasting-water leaching processes,respectively.Moreover,the valuable metals in the leachate were separated and recovered by solvent extraction.The main research contents were as follows:（1）The process of vacuum pyrolysis-air roasting-acid leaching was proposed to directly recover Ni,Mo,and V from unbroken spent hydrogenation catalyst.The residual oils in the spent hydrogenation catalyst were completely removed and recovered at 400℃for 120 min under vacuum conditions,and the recovery efficiency of residual oils was more than 88.0%.Then,the unbroken vacuum pyrolysis products were roasted in air atmosphere at 400℃for 120 min.And the Ni,Mo,and V deposited on the surface were quickly leached by sulfuric acid.The effects of roasting temperature,sulfuric acid concentration,and leaching time on leaching efficiency of valuable metals were investigated.Under the optimized conditions of 400℃,1 mol·L^-1 H₂SO₄,45℃,and solid-liquid ratio of was 1:15,the leaching efficiency of Ni,Mo,and V can reach98.99%,94.96%,and 98.60%within 15 min,but the leaching efficiency of Al was only 7.63%.The kinetic analysis showed that the leaching reaction of Ni,Mo,and V belongs to liquid film diffusion control model.（2）The synchronous recovery of Ni,Mo,V,and Al from spent hydrogenation catalyst was further studied by using sulfuric acid roasting-water leaching-solvent extraction process for the vacuum pyrolysis products.Vacuum pyrolysis products were mixed with concentrated sulfuric acid and roasted at 400℃for 120 min in air atmosphere,where the phases of valuable metals in the spent hydrogenation catalyst was converted to sulfate.Then,the Ni,Mo,V,and Al components can be directly dissolved into deionized water.The effects of roasting temperature,roasting time,molar ratio of sulfuric acid,leaching temperature,leaching time,and solid-liquid ratio on the leaching efficiency of valuable metals were investigated.After roasting at 400℃for 2 h for the mixture of concentrated sulfuric acid and spent catalyst with the molar ratio of 1.2,the leaching efficiency of Ni,Mo,V,and Al can reach 98.99%,97.60%,98.96%,and 98.50%within 10 min under the leaching temperature of 95℃and solid-liquid ratio of 1:20 g·m L^-1.Meanwhile,the separation behaviors of Ni,Mo,V,and Al in the leachate were investigated.It was found that Mo and V can be completely co-extracted into the organic phase with the synergistic role of trioctyl amine and H₂O₂.Commercial HBL110 extractant was used for selective separation of Ni from the raffinate,and the extraction rate reached 99.1%.The remaining Al was further extracted by P204,and the extraction efficiency reached 94.30%.99.70%Ni and 99.40%Al in the loaded organic phase can be extracted by using 2 mol·L^-1 and 5 mol·L^-1 H₂SO₄solution,respectively.Mo can be selectively stripped by using 15 g·L^-1ammonia water from the loaded organic phase with a stripping efficiency of 100%.Under the synergistic action of 2 mol·L^-1 H₂SO₄ and 0.5 mol·L^-1Na₂SO₃,the residual V in the organic phase can be effectively stripped,and the stripping efficiency reached 82.30%.This paper includes 52 figures,10 tables and 138 references...