Sustainable recovery of surface-deposited oils and valuable metals from uncrushed spent hydroprocessing catalysts

Abstract

The spent hydroprocessing (HDP) catalysts containing a considerable quantity of oily pollutants and valuable metals including nickel (Ni), molybdenum (Mo), and vanadium (V) are hazardous wastes to be treated urgently. Herein, a sustainable process featuring vacuum pyrolysis and fast acidic elution was proposed to recycling the residual oils and metal values from the uncrushed spent HDP catalysts. The removal efficiency of oils by vacuum pyrolysis reached more than 85% at 400 °C in 60 min. The Ni, Mo, and V deposited on the uncrushed catalysts were fast eluted and recovered by 1 mol/L sulfuric acid solution within 15 min. The ultrasound-assisted leaching could promote metal recovery within 10 min but then has no difference with stirring leaching. The leaching efficiencies of Ni, Mo, and V reached over 95% with few Al being dissolved (7.63%). The obtained uncrushed Al2O3 residue could be potentially recycled as the support for a fresh catalyst. The liquid film diffusion control mechanism was disclosed to represent the fast leaching process of metal values. These results provided a promising and green approach for the sustainable recovery of both residual oils and valuable metals from spent hydroprocessing catalysts.