Recovering Attached Crude Oil from Hydrodesulfurization Spent Catalysts

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As environmental awareness grows, hydrodesulfurization (HDS) catalysts have become crucial in petroleum refining, yet their use results in oil-laden waste, poses environmental risks, and complicates subsequent treatment. Efficient oil removal is thus critical for processing spent catalysts. This study systematically compares three de-oiling methods, extraction, chemical thermal washing, and pyrolysis, to identify the optimal de-oiling method. In the experiments, extraction achieves a 94.12% oil removal rate at a liquid-to-solid ratio of 10 mL/g, a temperature of 45 °C, and a time of 60 min, maintaining around 90% efficiency after five cycles of solvent recovery. Chemical thermal washing achieves an oil removal rate of 96.26% after 4 h at 90 °C, with 0.15 wt.% SDS, 3.0 wt.% NaOH, and a liquid-to-solid ratio of 10 mL/g. The heavy oil emulsion is then decomposed with 4% CuO and 5% H2O2. The pyrolysis method removes 96.19% of oil at 600 °C in 60 min. While the extraction and chemical thermal washing methods are effective, they produce wastewater, raising environmental concerns. In contrast, the pyrolysis method is more environmentally friendly. SEM, EDS, and FT-IR analyses show that after oil removal, the metal structures on the alumina support of the spent HDS catalyst are clearly exposed, facilitating the subsequent recovery of valuable metals.