A fast and efficient method for the efficient recovery of crude oil from spent hydrodesulphurization catalyst

The deoiling process is a critical issue in catalyst regeneration and recovery of precious metals from spent catalysts. This study developed a fast and efficient method to recover crude oil from spent hydrodesulphurization (HDS) catalysts. We employed four solvents (p-xylene, acetone, dichloromethane, and n-hexane) with different polar and aromatic properties to remove crude oil from the spent catalyst. The effects of environmental factors, such as contact time, ratio of catalyst to solvent, temperature, stirring rate, and particle size on washing efficiency were investigated. The crude oil and solvent in the oil-containing washing solution were then effectively separated and recovered. The recovered solvent was used to evaluate solvent cycle washing performance, and the recovered oil was analyzed by gas chromatography-mass spectrometry. The spent and deoiled catalysts were characterized by scanning electron microscope, interracial rheometer, and contact angle. The results showed that p-xylene, which has similar polarity and aromaticity to the molecular structure of crude oil, achieved an excellent crude oil washing effect. The crude oil washing efficiency of the spent catalyst can exceed 94% in 2 min. Furthermore, the solvent was recycled 10 times, and still maintained a removal efficiency of over 93% for crude oil in the spent catalyst. Compared to crude oil, recovered oil has less viscosity, ash, residual carbon, and a higher heat of combustion, allowing it to be more easily refined and recovered, and to gain more energy as an energy source.