Hydrometallurgical Treatment for Valuable Metals Recovery from Spent CoMo/Al₂O₃ Catalyst. 1. Improvement of Soda Leaching of an Industrially Roasted Catalyst

Abstract

This paper describes the recovery of molybdenum from a spent CoMo/Al2O3 by soda leaching after a roasting step. First, the leaching was performed on a catalyst industrially roasted at 800 °C during 20 min. In order to reach a molybdenum leaching yield higher than 85%, the process was optimized using a 23 design of experiments with parameters such as NaOH amount, leaching time, and temperature. Unfortunately, in the best leaching conditions defined by the factorial design, the leaching yield of molybdenum never exceeded 60% because of an incomplete roasting of the catalyst proved by the X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis of the residue. In a second part, the roasting was investigated on an unroasted catalyst containing 23.9% Al, 11% Mo, 2.9% Co, 7.9% S, and 6.3% C using a central composite design. By changing the thermal treatment conditions (700 °C, 20 min) and performing the best soda leaching conditions (an amount of sodium hydroxide equal to the twice of the required stoichiometry and a leaching time of 4 h at 60 °C), it was possible to extract more than 90% of molybdenum initially present in the catalyst.

Extraction and Recovery of Metals from Spent HDS Catalysts: Lab- and Pilot-Scale Results of the Overall Process

“…The rest of the process was tested in the laboratory, whose hydrometallurgical trials are much easier to scale up on pilot and thus full scale. The aim is the conversion of molybdenum and vanadium oxides into soluble sodium molybdate and vanadate, easily leached by hot water [23][24][25]. Although sodium hydroxide, sodium bicarbonate, and sodium sulfate have been used in direct salt roasting, sodium carbonate is the most used due to its lower cost [26,27].…”

Synthesis and characteristics of aluminate spinel ceramic pigments based on spent aluminium-cobalt-molybdenum catalyst

“…It represents granules of irregular cylindrical shape of pale blue colour. To increase the colour purity of obtained pigments, the valuable component MoO 3 was previously extracted from the spent АCМ catalyst by leaching according to the method described in Ruiz et al (2011). The extraction of molybdenum into solution when using NaOH as a reagent is more than 95%.…”

Efficient Phase Transformation of γ-Al2O3 to α-Al2O3 in Spent Hydrodesulphurization Catalyst by Microwave Roasting Method

“…2,3 The catalysts deactivate with time and eventually become hazardous wastes. 4,5 The production amount of spent HDS catalysts is about 120 000 tons (dry basis) every year. 6 In another hand, these solid wastes generally contain 15−30% aluminum, 4−12% molybdenum, 1−5% cobalt, 1− 5% nickel, and 1−5% vanadium, which make it economically feasible to recover these valuable metals from spent catalysts.…”