Leaching of spent Ni–Mo hydrodesulphurization (HDS) catalyst in oxalic acid solutions

Abstract

In this work, the effect of crushing, temperature, oxalic acid concentration and stirring speed on the leaching of spent Ni–Mo HDS catalyst was investigated. Spent Ni–Mo HDS catalyst was roasted at 500 °C under dynamic air atmosphere for 4 h prior to leaching experiments. It was found that roasted spent Ni–Mo HDS catalyst included mainly Al2O3, MoO3, NiMoO4 and AlPO4. Leaching experiments were performed using 5 g of uncrushed roasted Ni–Mo HDS catalyst, 1 L of 0.25, 0.50, 0.75 and 1 M H2C2O4 solutions, 25, 40, 55 and 70 °C temperatures and 200, 250 and 300 rpm stirring speeds. Leaching behavior of Mo, Al, P and Ni was determined. It is seen that H2C2O4 can be used successfully for the leaching of roasted HDS catalyst. More than 90% of the molybdenum and 80% of Nickel is extracted from the experiments carried out using 300 rpm stirring speed, 1 M H2C2O4 and 40 °C.